大气成分和大气化学
Atmospheric Composition and Atmospheric Chemistry

大气成分和大气化学研究进展

2014年，大气成分研究所圆满完成了承担的各项任务，在分析方法建立、比对校验、质量控制，大气成分及相关特性的观测、环境气象模式发展应用，影响评估等方面均取得了明显的进展。

1 分析方法、比对校验和质量控制研究

1.1 中国气溶胶遥感网Cimel太阳光度计积分球标定方法的建立

参考美国国家标准技术研究院对于积分球标定的方法，建立了中国气溶胶遥感网络（CARSNET）Cimel太阳光度计的积分球标定方法和流程。利用该标定方法和操作流程对4台CE318太阳光度计进行了标定试验。结果显示，与出厂参数相比，本方法获得的可见光波段标定系数相对偏差小于3%，而红外波段相对偏差约5%。太阳等纬圈(ALMUC)和主平面(PPLAN)现场验证实验数据显示，天空散射辐亮度在±6°表现出良好的一致性，所有波长的差异小于1%，表明该标定方法和流程适合CARSNET太阳光度计的校准，并有利于提高数据质量和网络观测的精度。（车慧正）

1.2 四级杆质谱与全二维气相色谱联用鉴定大气中的挥发性有机物

大气挥发性有机物的准确测量对空气质量评估、大气光化学机理研究和污染控制政策制定等具有重要意义。全二维气相色谱技术有助于准确测量复杂的大气挥发性有机物，但是对快速检测器的要求限制了全二维气相色谱与四级杆质谱的联用。通过研究将四级杆质谱与全二维气相色谱联用，并应用于大气挥发性有机物的鉴定。在对标准混合气体和北京城市空气测量中，鉴定了包括烷烃、烯烃、芳香烃、含氧烃以及卤代烃等125种挥发性有机物，并将鉴定化合物逐一对应至全二维气相色谱-氢火焰离子化检测结果中，从而完成了后者的谱图解析和进一步定量分析。对谱图中部分色谱峰保留时间随二维调制周期环绕的现象进行了详细讨论。全二维气相色谱分别与四级杆质谱和氢火焰离子化检测器联用进行定性和定量分析的方法不仅可靠实用，而且降低了仪器成本。该方法和研究结果可应用于其他挥发性有机物的分析中（图1）。（王瑛）

1.3 本底大气CO2观测分析过程中QA/QC方法的建立与评估

建立科学规范的本底大气CO2采样观测分析过程中的质量保证与质量控制方法，是实现该数据资源同化和共享的基础。本研究以中国气象局温室气体网络化采样观测经验为基础，以便携式采样观测尧波长扫描光腔衰荡光谱（WS_CRDS）分析技术为例，系统介绍了我国青海瓦里关全球本底站大气中CO2采样观测过程中的质量保证措施、样品分析过程中的玻璃瓶质量保证措施和样品分析过程中的系统质量控制方法、数据处理过程中的校正方法、数据分级质量标记和数据拟合插补方法等；并重点对该方法中几个关键步骤进行了评估验证；最后，应用本研究方法，对我国3个区域大气本底站CO2的采样观测数据进行了处理和浓度变化特征分析。本研究方法也可以较好地捕捉区域和局地环境因素对观测结果的影响，并客观、准确地反映该区域的自然和人为活动特征。（刘立新）

1.4 龙凤山本底站大气CO2数据筛分及浓度特征研究

针对黑龙江龙凤山区域大气本底站2009年1月至2011年12月低层（离地10 m）和高层（离地80 m）大气CO2在线观测数据，选取低层数据重点开展研究，分析地面风向和风速等因素对观测CO2浓度的影响。结果表明，龙凤山低层大气CO2浓度明显受局地源汇影响，其与高层观测结果差异在白天08∶00—17∶00相对较小，小于（0.5±0.5）×10-6（物质的比量）。春、夏和秋这3季节E-ESE-SE-SSE扇区来向的地面风会明显抬升大气CO2浓度、而冬季N-NNW-NW-WNW扇区CO2浓度明显较高。该站4个季节近地面CO2浓度随着风速增大而逐渐减小，在冬季尤为明显。结合日变化及地面风的影响对低层观测数据进行初步本底/非本底筛分，筛选出代表东北区域混合均匀CO2水平的本底数据占总数据的30.7%。本底CO2浓度季节变化显示该站大气CO2浓度呈现冬季高夏季低的趋势，季振幅为（36.3±1.4）×10-6，明显大于同期WMO、GAW同纬度站点观测结果，2009—2011年龙凤山大气CO2年平均增长率为2.4 ×10-6。（方双喜）

1.5 MeteoInfo: 气象数据显示分析GIS软件

MeteoInfo是为气象数据分析和显示开发的一套软件工具，包括一个面向软件开发人员的.Net类库和一个面向最终用户的桌面软件。MeteoInfo包含了一些基本的GIS功能，并能读取气象领域中常用的数据格式，如NetCDF和GRIB。对于格点和站点数据提供了能够进行复杂气象分析的数据模型。类库提供了丰富的空间和气象数据操作方法和控件，可以方便地用于相关业务软件开发。桌面软件具备友好的用户界面，是查看和探究气象数据的一个方便和强有力的工具。通过编写IronPython脚本程序，MeteoInfo可以自动运行并进行批处理操作。MeteoInfo是一个免费软件，已经在国内外有广泛的应用（图2）。（王亚强）

2 大气成分及相关特性变化的观测研究

2.1 我国上甸子区域本底站大气六氟化硫（SF6）在线观测研究

通过国际合作，采用欧亚地区卤代温室气体观测网（SOGE）和改进的全球大气实验网（AGAGE）技术，利用自组装气相色谱-电子捕获检测系统和气相色谱-质谱联用系统，在我国上甸子区域本底站自2009年6月至2011年5月开展了2个完整年度的在线观测。观测期间SF6平均本底和非本底浓度分别为7.22×10-12和8.66×10-12。上甸子站本底浓度与AGAGE同纬度本底站（Trinidad Head站和Mace Head站）浓度一致，大于南半球本底站（Cape Grim站和Cape Matatula站）浓度。观测期间SF6本底浓度快速增长，年增长率达到0.30×10-12。SF6本底浓度季节振幅为0.07×10-12，非本底浓度季节振幅则达到2.16×10-12。SF6的浓度峰值出现在秋季，地面风向来自W-WSW-SW-SWS-S，而SF6低浓度出现在地面风来自N-NNE-NE-ENE-E扇区。（姚波）

2.2 我国瓦里关和上甸子本底站大气CO2及其稳定同位素变化

利用2007—2010年瓦里关和上甸子站大气CO2及其碳稳定同位素观测数据，对二者的变化特征、相关关系和源汇特征进行了分析研究。结果显示，瓦里关站大气CO2及其δ13C具有显著的长期变化趋势和季节变化规律，同时二者呈明显的镜像关系，年际变化规律显示出北半球中高纬度陆地生态系统源汇季节变化特征。CO2年均浓度呈线性增长趋势，年均增长率为（2.1±0.1）×10-6；δ13C年均值则呈线性下降趋势，年均增长率为（-0.02±0.001）‰。在上甸子站，受陆地生态系统和人类活动共同影响下，大气CO2年均值亦呈线性增长趋势，年均增长速率为（1.8±0.1）×10-6；同时CO2季振幅达到23.0×10-6。2009—2010年度δ13C年均值由-8.27‰降至-8.36‰。瓦里关和上甸子站δs分别为（-25.44±0.72）‰和（-21.70±0.67）‰；在瓦里关站，冬春季δs偏负；而在上甸子站，由于受到夏季C4植物光合作用和冬季生物质燃烧的影响，其δs全年偏重并较瓦里关站更偏正。（刘立新）

2.3 我国4个大气本底站大气CO2浓度观测研究

利用基于光腔衰荡光谱技术，于2009—2011年对我国4个世界气象组织/全球大气观测网（WMO/ GAW）全球或区域本底站（浙江临安、黑龙江龙凤山、北京上甸子和青海瓦里关）大气CO2浓度进行连续观测研究。其中临安站位于经济发达区域（上海），龙凤山站位于农田和森林区域，离省会哈尔滨较近，而上甸子站距离北京约150 km。瓦里关站代表我国内陆本底清洁大气水平，该站也拥有国内最长的大气CO2观测记录。观测期内4站大气CO2浓度年增长率分别为（3.7±1.2）×10-6（临安）、（2.7±0.8）×10-6（龙凤山）、（3.5±1.6）×10-6（上甸子）、（2.2±0.8）×10-6（瓦里关）。相比而言，临安站CO2浓度最高，在2011年平均浓度为（404.2±3.9）×10-6。通过对各站大气CO2浓度日变化、季节变化以及局地源汇影响分析，研究了各站浓度特征以及影响因素。以上研究为认识我国大气CO2浓度特征以及模式研究提供了基础支撑。（方双喜）

2.4 长三角区域临安站大气CO2本底信息的评估

结合气溶胶观测记录和气象资料，对长三角地区大气中混合均匀的CO2本底信息进行了提取研究。基于新研发的方法，对浙江临安站2009—2011年观测的CO2浓度记录进行筛分，并评估了人为活动对观测浓度的影响。结果表明，通过本方法提取的CO2本底浓度与R筛分提取的信息基本一致，在重污染条件下，本方法对于区域本底CO2信息的提取明显优于R筛分法。2009—2011年临安站年平均CO2浓度分别为（404.7±8.2）×10-6、（405.6±5.3）×10-6、（407.0±5.3）×10-6，明显高于全球平均。人为活动排放对临安区域大气本底CO2浓度有明显影响，抬升约9.1×10-6。（方双喜）

2.5 上甸子本底站卤代温室气体大气浓度短期波动的个例分析

利用轨迹分析法、印痕分析和流场分析法，结合上甸子站卤代温室气体H-1301、HCFC-22、CFC-11和SF6在线浓度观测数据，选取2012年9月7—12日上甸子测站卤代温室气体浓度短期波动典型个例进行分析。轨迹分析结果表明：9月7日12∶00污染发生前，气团主要来自较远的偏西北、偏北方向，水平输送距离长、移速快、垂直高度高，对应的卤代温室气体浓度偏低，H-1301、HCFC-22、CFC-11和SF6的体积分数分别为4×10-12、350×10-12、260×10-12、10×10-12；9、10日有一定比例的气团在测站的偏南区域近地面回旋打转，水平输送距离短、垂直高度低，在边界层内缓慢移动，不利于污染物在边界层内扩散，导致卤代温室气体浓度偏高，对测站浓度的短期抬升贡献较大，9日12∶00 H-1301、HCFC-22、CFC-11的峰值体积分数分别达到45×10-12、200×10-12、310×10-12，10日03∶00 SF6的峰值体积分数达到28×10-12；11日西南方向回旋气团消失；12日气团完全来自较远的西北方向且轨迹移动较快。印痕分析与轨迹分析结果一致：7、8日敏感性系数较高区域主要分布在测站以北，9、10日敏感性系数较高区域分布在测站偏南，11、12日测站偏南的敏感性系数较高区域消失。流场分析结果表明：9、10日环流形势有利于污染物在测站区域累积，造成测站浓度的短期抬升。（安兴琴）

2.6 北京上甸子区域大气本底站甲基氯仿（CH3CCI3）在线观测研究

利用GC-ECD在线观测系统，在北京上甸子区域大气本底站开展了CH3CCl32年在线观测，利用逐步逼近回归法进行本底值筛分，讨论了上甸子站CH3CCl3浓度水平及其变化趋势。该站2009年和2010年的年均大气CH3CCl3本底浓度（摩尔分数，下同）分别为(9.03±0.53)×10-12和 (7.73±0.47)×10-12，本底数据出现频率为61.1%（2009年）和60.4%（2010年）。上甸子站CH3CCl3浓度水平与北半球同纬度带本底站观测结果基本一致，低于文献报道的2001—2005年间我国华南区域和城市观测的结果。观测期间本底浓度呈下降趋势，年下降率为1.39×10-12。结合风向分析，该站CH3CCl3平均浓度最高的风向来自西南扇区，而平均浓度最低的风向来自东北扇区，不同风向的浓度差值分别为0.77×10-12（2009年）和0.52×10-12（2010年）。2010年各风向CH3CCl3平均浓度比2009年降低1.03 ×10-12～1.68×10-12。（姚波）

2.7 气团垂直输送对中国西南香格里拉区域大气本底站近地面臭氧浓度的影响

根据2007年12月到2009年11月在中国西南香格里拉区域大气本底站（28.006°N，99.726°E； 3580 m）的近地面臭氧、一氧化碳以及气象数据的现场观测，发现臭氧和一氧化碳的季节峰值在春季而臭氧的谷值在夏季、一氧化碳的谷值在冬季。根据月均归一化的臭氧、一氧化碳和水汽值的变化，提出了一个用于指示来自高层大气、富含臭氧气团向下输送到近地面的归一化指示因子（标为Y）。这个组合的因子具有较少受季节或偶然个例变化影响的优点。 通过对Y值的分析，发现大多数有效的向下输送经常发生在冬季（占总数的39%，当Y的指示值大于4时），导致了近地面臭氧浓度显著地上升。来自较强的向下输送事件导致冬季近地面臭氧浓度增加9.6×10-9（21%）。基于Y值与位势涡度、臭氧总量和后向轨迹很好地分析了一个由西风槽主导下较强的臭氧向下输送个例。亚洲季风在压制夏、秋季近地面臭氧的积累中扮演了一个很强的角色，而由Y值指示的香格里拉高层臭氧向下输送的季节变化与青藏高原地区的平流层-对流层输送、副热带高空急流的季节变化有一致性。（郑向东）

2.8 超大城市北京冬季过氧乙酰硝酸（PAN）：化学与气象过程的作用

亚洲超大城市大气过氧乙酰硝酸（PAN）的测量研究过去很少，而且主要局限于夏季较短的时段。本研究给出了2010年1月25日至3月22日北京市区中国气象局大院同步观测的PAN、O3、NOx等的分析结果。PAN小时平均浓度为0.70×10-9（0.23×10-9～3.51×10-9），与NO2浓度呈较好的正相关，但与O3浓度却不相关，这表明冬季城市PAN和O3是脱钩的。风速风向和气团输送条件对O3、PAN等污染物有非常显著的影响。到达测点的气团来自严重污染N-S-W扇区的边界层或者来自W-N扇区的自由对流层。自由对流层的下沉空气富含O3，其平均PAN/O3比值小于0.031，而污染扇区边界层空气含高浓度PAN和一次污染物，其平均PAN/O3比值为0.11。这些有关输送条件的事实可较好地解释观测到的PAN与O3的脱钩现象。北京冬季光化学生成对于PAN仍是重要的。形成PAN需要的PA自由基浓度估算值介于0.0014×10-12和0.0042×10-12之间。计算了PAN的生成反应和热分解反应对PAN浓度变化的相对贡献，发现即使在北京较冷的时期，两者的作用都是显著的，其中生成作用超过分解作用（图3）。（徐晓斌）

2.9 北京及周边地区3个典型站点NOx和CO的变化特征

为了研究华北平原北部区域不同类型站点光化学前体物的共性与差异，在华北平原北部地区西南—东北主导风向上选取间距大于100 km的3个站点，即中国气象局（CMA）、上甸子（SDZ）和固城（GCH）依次代表北京城区、华北本底地区和相对污染的农村地区，进行了近地面NOx和CO观测。结果表明：2008年6月至2009年5月，CMA、SDZ和GCH 3站NOx体积分数的年均值依次为（42.4±21.8）×10-9、（13.8±5.5）×10-9和（26.9±15.2）×10-9；CO体积分数的年均值依次为（1.13±0.37）×10-6、（0.67±0.17）×10-6和（1.11±0.62）×10-6。3站的NOx月均值体积分数以及CMA、GCH 2站的CO月均值体积分数呈现出冬季高夏季低的特点，而SDZ站的CO 6月均值体积分数（1.03×10-6）为一年中最高。SDZ站的NOx和CO体积分数值在中午12∶00前后出现一个低谷，比CMA和GCH站的提前3～4 h，此后呈上升趋势，体现了午后西南风输送对SDZ站的影响。尽管不同的源排放和大气输送影响导致3站的NOx和CO体积分数在日变化特征上有所差异，但3站的NOx和CO日平均体积分数之间存在极其显著的相关性，体现了区域性污染和气象条件共同影响的特征（图4）。（徐晓斌）

2.10 浙江临安大气本底站CO浓度及变化特征

利用基于光腔衰荡光谱（CRDS）技术自组装的大气CO在线观测系统，于2010年9月至2012年2月在浙江省临安大气本底站对大气CO进行了在线观测。结果表明，临安站四季CO日变化明显受人为活动影响，分别在每日07∶00—10∶00和19∶00—20∶00出现峰值，夏季CO日平均浓度和振幅均最低，分别为（314.3±7.6）×10-9（摩尔比，下同）和（50.1±47.9）×10-9。该站全年大气CO浓度呈现冬春季高、夏季低的趋势、与北半球瑞士Jungfrauioch站、青海瓦里关等站基本一致，但平均浓度明显高于其他国际站点，全年CO月均值振幅为（286.8±19.2）×10-9。轨迹聚类和地面风结果分析表明，临安站非本底CO浓度主要来自N-NNE-ENE扇区内城市及工业等人为排放，春、夏和冬季最大的浓度抬升均出现在NEN风向，冬季抬升值最大为（106.3± 58.0）×10-9。（方双喜）

2.11 长江三角洲区域本底站氨气和铵盐气溶胶季节变化特征

2009年9月至2010年12月在位于经济快速发展的华东长江三角洲之临安区域本底站使用被动采样器对大气氨进行了强化观测，同时在2010年对该站大气细粒子PM2.5开展了为期1年的观测。观测期间临安站NH3浓度变化范围为（0.1～41.8）×10-9，2010年NH3年均浓度是（16.5±11.2）×10-9。2010年临安站PM2.5中的NH4+质量浓度变化范围为0.02～19.2 μg/m3，年均浓度为（4.3±3.5）μg/m3。NH3浓度季节变化明显，夏季最高冬季最低，其主要与周边农业活动和气温呈正相关。NH4+浓度在秋季最高可能是受到农业残余生物质燃烧的影响。2010年临安站NH3/NHx的比值为0.8±0.1，说明NHx主要是受到当地源的影响。后向轨迹分析表明，临安站因受到长江三角洲区域及偏北气流引起的污染长距离传输影响，呈现出高细粒子水平特征。临安区域本底站高NHx沉降说明了在长江三角洲区域减少NH3排放的紧迫性。（孟昭阳）

2.12 北京PM2.5中水溶性离子的变化、形成以及酸性特征

总结了北京城区2009年6—11月期间PM2.5日均浓度、PM2.5中水溶性无机离子小时平均浓度以及PM2.5气态前体物浓度。结果表明，水溶性离子总浓度为44 μg/m3，占PM2.5的38%，其中硫酸盐、硝酸盐和铵盐是主要的离子成分。硫酸盐在夏季和秋季浓度差异在30%以内，而硝酸盐和铵盐的浓度在两个不同季节差别明显。由于源排放、生成机理以及气象条件的不同，导致多数离子成分及其前体物浓度的日变化特征明显。硫酸盐、硝酸盐和铵盐的氧化/转化率分别为63%，15%和15%。尽管环境大气中存在大量氨气，但铵盐的转化率仍然很低，说明气态氨的浓度水平不是铵盐生成主导因子。铵盐的日变化特征也与气态氨的日变化特征不同。对PM2.5中氢离子浓度以及气溶胶酸度的估算结果显示，有75%的样品显强酸性，只有极少部分样品显碱性。（张养梅）

2.13 我国中东部高山站PM1中主要化学组分和粒径分布特征

自2010年6月至2012年1月，对泰山高山站亚微米气溶胶主要化学组分质量浓度和粒径分布特点进行了归纳和总结。结果表明，该站点亚微米气溶胶中有机物、硫酸盐、硝酸盐、铵盐和氯化物的年平均质量浓度分别为11.2、9.2、7.2、5.8和0.95 μg/m3。这个浓度水平明显高于美国和欧洲的高山站，但比我国城市近地面站点浓度要低。在整个观测阶段，主要化学组分浓度具有明显的季节变化规律、边界层高度的季节变化特点，近地面污染物浓度以及区域传输过程等因素是导致秋季浓度低、夏季浓度高的主要原因。

为了更好地探讨不同类型污染天气对亚微米气溶胶特性的影响，本研究将气团分成了受边界层影响（PBL）、受自由对流层影响（LFT）、新粒子生成事件（NPF）、云中过程和污染过程等5类。其中，有机物在新粒子生成事件中占有主导地位，而硫酸盐在云中过程中对亚微米气溶胶的贡献最大。

整个研究期间，有机物、硫酸盐、硝酸盐和铵盐的质量谱均值粒径分别为539、585、542和545 nm。该均值粒径比在华北地区地面观测的均值粒径要偏大，说明高山站气溶胶粒子相对老化并混合均匀。在PBL、NPF和污染事件中，有机物在小粒子范围贡献最大，尤其在污染事件中，在100～200 nm之间，有70%的组分是有机物。在云中过程中，无机物在整个亚微米粒径范围贡献70%，其中硫酸盐在小粒子范围贡献40%，表明硫酸盐在云形成过程中起到至关重要的作用。

根据气团轨迹特点将该站点受到的主要气团来向分为7条，大多数气团来源于短距离的区域扩散，主要气团来自站点南方，其中有机物和硫酸盐是这类气团的主要污染物种。远距离传输气团通常载带着清洁和干燥的气团影响泰山站点。

利用正矩阵因子分析方法对有机物进行的分类解析结果表明，泰山站有机气溶胶中，氧化类有机气溶胶在春、夏、秋、冬4个季节分别占总有机物的49%、56%、51%和41%，说明夏季有机物氧化程度较严重。此外，生物质燃烧类有机气溶胶夏季占有机气溶胶的34%，燃煤类有机气溶胶在冬季占有机气溶胶的22%。（张养梅）

2.14 中国不同区域大气气溶胶化学成分浓度、组成与来源特征

为获得中国不同区域大气气溶胶化学组成的总体“图景”，进一步探讨污染治理方向，需要分区域评估其化学成分浓度水平、组成与来源特征。通过对近地层中国内陆大气气溶胶中6种主要化学成分（硫酸盐、硝酸盐、铵、有机碳、黑碳和矿物气溶胶）至少有1年观测研究的评估分析，获得不同区域气溶胶化学成分质量浓度水平与组成的评估结果。在气溶胶污染最严重的4大区域（即北京以南的华北与关中平原区域、以长三角为主体的华东区域、以珠三角为主体的华南区域以及四川盆地）的PM10中矿物气溶胶（所占20%～38%）、硫酸盐（占14%～24%）、有机碳（占11%～18%）是3个主要组分；其中华北与关中平原气溶胶污染在中国最重，硫酸盐浓度为35～47 μg/m3（远高于北京的（13～18 μg/m3））、有机碳为28～45 μg/m3（约是北京（19～22 μg/m3）的1.8 倍）、硝酸盐为19～22 μg/m3（约是北京（9.9～12 μg/m3）的2倍）、铵为14～16 μg/m3（比北京（6.2～8.4 μg/m3）高1倍），黑碳在北京和北京以南城市的浓度差别不大（9.1～12 μg/m3）。这其中燃煤对硝酸盐和有机碳气溶胶的贡献超过50%，农业活动是铵的最重要来源。华东、华南和东北城市区域气溶胶化学成分浓度水平与北京相近，但四川盆地城市站各组分浓度均高于北京，污染较重。西北兰州城市站，除了黑碳浓度低很多、硝酸盐浓度稍高外，其他气溶胶化学成分浓度水平与北京相当。西北偏远区域沙漠站点，各种气溶胶化学成分的浓度都远低于北京。青藏高原和云贵高原城市站气溶胶化学成分浓度与北京相比也明显偏低。不同区域气溶胶化学组成分析显示，燃煤、机动车、城市逸散性粉尘和农业活动是4个最需要关注的污染源，加强除发电行业外的燃煤脱硫，进一步消减燃煤氮氧化物、一次有机碳和挥发性有机物排放，并有效减少农业活动排放到大气中的氨，更有效限制硫酸盐和硝酸盐的形成是已有大气污染治理对策基础上，未来应特别关注的控制方向。（张小曳）

2.15 泰山PM10及其中化学成分变化特征

为研究具有区域背景代表性的气溶胶成分及其变化特征，在泰山顶从2010年6月至2011年7月采集了64个PM10滤膜样品，分析了样品的PM10及其中无机盐离子和有机碳（OC）、元素碳（EC）的质量浓度，并对各成分相关性等进行了分析。泰山PM10年均质量浓度约为68.4 μg/m3，其中无机盐离子约占总质量的64.8%，碳气溶胶约占17.4%。无机盐离子的质量浓度从春季逐渐增大，夏季达到峰值，秋季下降，冬季最小；OC质量浓度从春季至秋季逐渐增高，冬季最低，EC变化类似，但夏秋两季差别不大。二次有机碳（SOC）与OC的比值四季均在50%以上，年均值约为58.5%。通过后向轨迹聚类分析，发现在经过城市的较短轨迹以及南方较短混合轨迹的影响下，泰山PM10质量浓度较高，而西北长距离传输气团PM10浓度均较低。（王亚强）

2.16 北京上甸子典型天气个例的大气气溶胶数谱分布特征

使用差分淌度粒径分析仪（TDMPS）和空气动力学粒径分析仪（APS）对上甸子区域本底站颗粒物（直径3 nm～10 μm）数谱分布特征进行观测。利用2008年的观测结果，分析了不同天气（包括沙尘天气、干洁天气和雾霾天气）条件下大气气溶胶数谱分布及其与气象要素和气团来源的关系。结果表明，沙尘天气条件下，上甸子站受西北方向的气团控制，风速较大，粗粒子数浓度明显增加，PM10的质量浓度可以迅速增加到毫克每立方米的量级。典型的“香蕉型”新粒子生成事件通常发生在比较干洁晴朗的天气条件下，西北气团主导，大气中背景气溶胶数浓度较低，核模态气溶胶数浓度迅速增长，气溶胶的粒径呈现明显的增长过程，核模态可以平稳地增长到80 nm左右，达到成为云凝结核的尺度。雾霾天气通常是在西南气团影响下，细颗粒物（1 μm以下）的不断累积、相对湿度不断升高的条件下发生的。雾霾天气条件下数谱分布的几何中值粒径出现在积聚模态，积聚模态数浓度也高于非雾霾天。个例研究表明，雾霾天气条件下PM2.5质量浓度可以达到非雾霾天的10倍左右，其中以细颗粒物的贡献为主。在雾霾天气条件下，上甸子地区数浓度较高的积聚模态颗粒物主要来自城区的传输，因此对背景地区气溶胶数谱的研究可以为解析城区气溶胶复杂来源提供依据。（沈小静）

2.17 基于地基太阳光度计测试的2013年中国华北平原严重雾霾月数据进行的柱状气溶胶光学特性和气溶胶辐射强迫研究

2013年1月，华北平原经历了几次严重的雾霾事件，在2013年1月1—30日，基于Cimel 太阳光度计在华北背景、郊区和城市等7个站点进行了观测，研究气溶胶光学参数的时空变化和气溶胶辐射强迫。研究结果发现，500 nm气溶胶光学厚度在无污染时期每个站点都低于0.30，在污染事件发生时期，气溶胶光学厚度显著大于1.00。在大多数时间段，所有的站点Angstrom指数都大于0.80。污染和非污染时期，在北京的3个城市站点，500 nm平均气溶胶光学厚度从北向南逐渐增加。在城市站点污染期间细模态气溶胶光学厚度大约是无污染时期的2.5倍，而在郊区和农村站点达5.0倍左右。在2013年1月，对于所有站点675 nm细模态气溶胶光学厚度所占比例大于80%。污染时期，675 nm气溶胶光学厚度吸收在农村站点约为0.01，而在其他地区的污染和非污染时段，分别为0.03～0.07和0.01～0.03，单次散射反照率在0.87和0.95之间。雾霾最严重时期，北京城区气溶胶粒子谱分布呈现出明显的3峰分布特征。在污染时期，细模态气溶胶有效半径为0.01～0.08 μm，大于非污染时段；而粗模态粒子有效半径，在污染时段为0.06～0.38 μm，比非污染时期小。总体、细模态和粗模态气溶胶体积变化分别为0.06～0.34 μm3，0.03～0.23 μm3和0.03～0.10 μm3。在雾霾最严重的时期（1月1—16日），气溶胶辐射强迫在农村、郊区、城市分别超过了-50 W/m2、-180 W/m2和-200 W/m2。在大气层顶，农村和城市地区气溶胶辐射强迫数值分别为-30 W/m2和-40～60 W/m2。由于积雪覆盖导致的高反照率，惠民城市站点大气层顶正的气溶胶辐射强迫不同于其他站点。（车慧正）

2.18 2013年1月中国东部一次重度霾污染事件的天气成因分析

应用加密地面气象要素观测资料、经纬仪气球探空资料、NCEP再分析资料以及T639模式输出产品，采用大气环流三维结构合成分析、稳定边界层物理量诊断分析以及轨迹模式HYSPLIT4跟踪等方法，研究2013年1月6—16日中国华北大范围雾霾天气过程发生和持续的气象成因，探讨气象条件在2013年1月10—12日北京PM2.5质量浓度连续上升过程中的作用与影响。结果表明：（1）大气环流从经向波型调整成为纬向波型的过程为中国华北地区提供了有利于雾霾天气发生的静稳型环流形势；（2）边界层大气层结稳定、对流高度值低，使边界层湍流运动受到抑制，为雾霾的形成提供了有利的气象条件；（3）黄河河套以东广大地区（包括山西、河北等地）在对流层低层存在一支低空西南气流（6～11 m/s），有利于这些地区的污染物向北京方向远距离输送，加剧北京的空气污染程度；（4）美国NOAA研制的HYSPLIT4模式对气团72 h后向轨迹追踪与高空探测结果相吻合，具有参考价值。（王宏）

2.19 中国北京严重雾霾条件下气溶胶光学特性的研究

2013年1月，在中国华北地区发生了几次严重的霾污染事件。基于中国气象科学研究院站点2013年1月1—30日期间的Cimel太阳光度计的数据，详细研究了气溶胶的光学特性。研究发现，2013年1月雾霾期间，当北京城区气溶胶光学厚度大于0.60时，Angstrom指数大多大于0.80。在霾发生之前，北京城市地区气溶胶光学厚度大约可以稳定在0.40，而之后，伴随霾的产生，500 nm气溶胶光学厚度急剧上升超过1.50。在严重的霾污染时期，细模态大气气溶胶是粗模态的20倍。在440、675、870和 1020 nm 4个波段，单次散射反照率接近0.90±0.03，细模态粒子单次散射反照率在440 nm波段相对一致，而在675、870和1020 nm波段变化很大。除1月12日和18日外，所有的细粒子体积都高于粗粒子体积，表明由人为产生的细粒子是雾霾产生的主要因素。对2013年1月严重雾霾污染事件气溶胶类型分类分析表明，占主导地位的气溶胶类型能够被分为“混合”和“城市/工业/生物体燃烧”两种类别。混合型约为31%，而城市/工业型约为69%。（车慧正）

2.20 使用Prede天空辐射计在北京城市站点反演的气溶胶光学特性

SKYNET是基于Prede天空辐射计的国际气溶胶光学特性观测网络，主要目的是研究气溶胶-云-辐射相互作用。利用最新SKYRAD.pack软件（版本5.0）反演了北京城市站点气溶胶光学特性，包括气溶胶光学厚度（AOD），波长指数（α），粒子体积谱分布及单散射反照率（SSA）等。研究结果表明，北京500 nm 的AOD值变化区间在0.11（第5百分位）到1.14（第95百分位），中值为0.34，季节平均的α最大值出现在夏季，为1.05±0.36，最小值出现在春季，为0.82±0.39。500 nm的SSA值在夏季和春季有相似的较高值，为0.96±0.03，但在冬季较低，为0.93±0.04。在北京全年的气溶胶粒子清楚地表明了双峰尺度分布：春季粗粒子，夏季细粒子。α随着AOD增大而变大，表明在北京细粒子在气溶胶光学特性中起着重要作用。根据沙尘标准阈值（α＜0.47并且 SSA400nm-SSA1020nm＜0.018） ，在所有的观测数据中沙尘类型气溶胶发生率在春、夏、秋和冬季分别占4.1%，5.1%，0.5% 和1.2%。（车慧正）

2.21 2013年1月一次持续性重度霾污染事件的综合观测研究

针对2013年1月6—16日中国东部地区的一次强污染过程， 对其能见度、PM10、SO2和NO2浓度、550 nm的ODIS AOD、440 nm的CARSNET AOD和CLIPSO 532 nm的气溶胶消光系数等观测资料进行了综合分析。 研究结果发现，东部地区这次持续性大面积霾污染过程伴随着低能见度、高PM10和AOD。污染最为严重的地区是京津冀以及河北中南部、山东西部和河南北部在内的紧邻周边地区。霾污染扩散到了中国东部到125°E 的海面，甚至对整个140°E以西的洋面都有所影响。京津冀及其周边地区PM10的变化趋势呈现出很大的相似性， 显示该地区污染物跨城市输送的可能影响。在这次严重霾污染事件中，超级城市群的郊区显示出和城市非常相似的严重污染状况。大部分污染物集中在地面以上1500 m高度， 特别是100～800 m高度是污染物最为集中带。（王宏）

2.22 中国华北平原地区区域背景大气柱状整合的气溶胶光学和物理特性

基于兴隆站2006年2月到2011年7月的气溶胶光学特性数据研究了北方平原区域背景气溶胶光学和物理特性以及在沙尘和霾条件下的时间变化情况。结果表明，兴隆年平均气溶胶光学厚度和消光波长指数分别为0.28±0.30和1.07±0.38。季节平均的AOD440nm在春季（0.40±0.3）和夏季（0.40±0.42）高于秋季（0.20±0.22）和冬季（0.19±0.21）。兴隆站的消光波长指数约为1.25，吸收波长指数为1.0～1.5，这表明占主导地位的类型是混合气溶胶（当AAE＞1.0时占88.2%）。几乎所有的沙尘观测都发生在春季。细模态和粗模态颗粒的体积浓度随AOD的增加而增加。在春季，粗粒子气溶胶的增加程度大于细粒子；然而，在其他季节观测到相反的现象。兴隆站的高值AOD可能与细模态气溶胶增长及粗模态粒子有关。该背景站不仅受来自中国西北和蒙古国南部沙尘气溶胶的影响，也受到来自南方城市和工业化地区人为气溶胶远距离输送的影响。沙尘天气的平均AOD为1.49，而霾天的AOD为1.10。沙尘天和霾天的平均波长指数分别为0.09和1.43。（车慧正）

2.23 1980—2009年塔克拉玛干沙漠沙尘气溶胶对驱动表面太阳辐射呈上升趋势

研究了塔克拉玛干沙漠在1980—2009年表面太阳总辐射（SSR）的长期趋势及其与总云量（TCC）、低云（LCC）、水汽含量（WVC）和气溶胶光学厚度（AOD）的关系。该地区年平均SSR每10年增加了1.21 W/m2，除了冬季，SSR均呈上升趋势。TCC，LCC和WVC有所增加，而AOD和严重沙尘时间发生频次均呈减少趋势，表明在塔克拉玛干沙漠是沙尘气溶胶而不是云层和水蒸汽驱动SSR的长期上升。（车慧正）

2.24 中国四川盆地基于地面测量的气溶胶光学特性

测量并分析了2007年2月到2009年12月中国四川盆地成都站点的气溶胶光学厚度（AOD）和Angstrom指数以及气溶胶光学厚度与PM10之间的关系。观测中发现AOD月平均高值出现在3月、8月和12月而相对较低的值出现在10月，Angstrom指数在3月和8月的变化与AOD相反，平均PM10呈显著的季节性差异，冬季存在高峰值，总的AOD值与近地面层的PM10之间存在一个复杂的（非线性）正相关关系。沙尘和雾霾条件下的3个案例表明，AOD值在沙尘天气条件下最大而在霾天气条件下最小，然而3种天气条件下Angstrom指数分布与AODs相反。3天的后向轨迹分析表明，空气质量的起源很大程度上影响四川盆地上方的气溶胶光学特性。（车慧正）

2.25 利用CloudSat卫星资料分析云微物理和光学性质的分布特征

利用2007年1月至2010年12月高垂直分辨率CloudSat卫星的2B数据产品，对云微物理特征量（包括云中液态水/冰水含量、液态水/冰水路径、云滴有效半径等）以及云光学参数（云光学厚度等）的全球分布和季节变化进行了统计分析，并研究了云微物理性质对光学性质的影响。结果表明，冰水路径分布在北美南部、南美大陆、非洲大陆、澳大利亚和南亚的陆地上空，以及太平洋、大西洋和印度洋的洋面上空，高值区最大值达600 g/m2以上，垂直方向上高值区位于赤道地区8 km附近以及中纬度地区4～8 km高度上。液态水路径在300 g/m2以上的高值区主要位于太平洋、印度洋和大西洋的中低纬度海域上空，垂直方向上液态水含量随高度递减。冰云有效半径在高纬度地区近地面层达200 μm以上，在赤道附近4～8 km上有1个高值区，南北半球中纬度地区2～4 km上有2个高值区，最大值均达到80 μm以上。在1 km以下的边界层水云有效半径值较大，达到12 μm以上。总云光学厚度在全球大部分地区＜40，高值区普遍位于中高纬度的广阔地区和低纬度靠近大陆的洋面上空；垂直方向上云光学厚度的高值集中在2 km以下的边界层。云光学厚度的分布受云量、云水含量和云滴有效半径的影响，云量大的地区基本为云光学厚度的大值区。（王志立）

2.26 青藏高原及其周边地区卫星Aura-MLS的臭氧与水汽廓线产品的验证分析

根据Aura卫星微波临边探测（MLS）2.2、3.3版水汽和臭氧廓线，采用线性内插方法，将夏季在青藏高原（西藏的那曲和拉萨）及其周边地区（云南腾冲）通过冷冻霜点仪（CFH）和电化学反应池型（ECC）探空仪分别测得的水汽和臭氧数据插值到与卫星产品规定的气压高度进行比较分析，以检验MLS水汽和臭氧廓线产品。结果表明：MLS 2.2、3.3版水汽相对误差在100 hPa的对流层顶附近分别为（9.8±46.0）% （n=18）、 （23.0±45.8）% （n=17）；在小于并包含82.5 hPa在内的下平流层则分别为（2.2±15.7）% （n=74）、（0.3±14.9）% （n=75）；而在对流层316～ 121 hPa高度则分别为（21.5±90.6）% （n=104）、（6.0±83.4）% （n=99）。相应MLS 2.2、3.3版臭氧的误差分别为：（-3.5±54.4）% （n=27）、（-8.7±41.6）% （n=38）（100 hPa）；（-11.7±16.3）% （n=135）、（15.6±24.2）%（n=305）（下平流层）；（18.0±79.1）% （n=47）、（34.2±76.6）% （n=160）（对流层上层）。MLS水汽和臭氧的误差垂直分布在对流层上层-平流层低层振荡和离散分布明显，部分误差可能由此高度层水汽和臭氧浓度梯度大和用线性插值探空数据引起。 “臭氧低谷”期间，拉萨地区70 hPa高度以下MLS卫星臭氧浓度误差明显增加；腾冲、那曲与拉萨3地的MLS臭氧误差的垂直分布特征较一致。卫星产品与探空测值的初步关系表明，MLS廓线的灵敏度与水汽和臭氧在大气中垂直分布有密切联系，3.3版水汽产品的灵敏度在82.5 hPa以上高度略有提高，臭氧产品灵敏度没有明显变化。对MLS水汽和臭氧廓线产品误差的可能因素也进行了讨论。（郑向东）

3 大气成分模式的发展应用及大气成分的影响研究…

3.1 APEC环境空气质量预测和减排效果评估

实施了APEC会议1个月前的污染趋势预报，在临近APEC和APEC期间，实施了精细化预报。对北京城区和会议区域（怀柔）的空气质量进行了7～10天的预报。与此同时，对APEC期间的减排措施进行了评估和分析。综合分析表明，2014年11月3—12日APEC会议期间，北京及周边采取的大气污染物减排措施使北京城区PM2.5浓度约降低35%，NO2浓度约降低33%，有效避免了重污染天气发生。APEC会议期间，由于南风弱，大气污染物跨区域输送不明显，北京本地减排对改善空气质量的贡献率为83%～89%，周边地区减排的贡献率为11%～17%。分析还发现，APEC会议期间，周边300 km范围内采取减排措施对北京的影响效果与600 km范围内的减排效果相当；外地机动车的减排措施对北京影响不大；周边区域高架点源减排对降低北京地区PM2.5浓度的贡献约为9%。（龚山陵，刘洪利）

3.2 气溶胶-气候在线耦合模式BCC_AGCM2.0.1_CUACE/Aero中云微物理过程的改进、评估以及更新的气溶胶间接效应

将一套能同时预报云滴和冰晶质量浓度和数浓度的双参数云微物理方案应用到气溶胶-气候在线耦合模式BCC_AGCM2.0.1_CUACE/Aero中，详细评估了模式对气溶胶、云性质和气象场的模拟性能，计算了气溶胶的间接辐射强迫。较之前模式，新模式能更真实地模拟出气溶胶的质量浓度和光学厚度。新模式模拟的全球年平均柱云滴数浓度为3.3×1010m-2，与卫星反演结果4.0×1010m-2相当。新模式模拟的全球年平均云顶云滴有效半径为8.1 μm，小于相应的观测结果10.5 μm。新模式模拟的云液态水路径明显低于旧模式的结果，特别是在中纬度一些区域，年平均的云液态水路径低了近100 g/m2，但是与卫星观测结果更加一致。新模式对云辐射强迫和降水的模拟在一定程度上也有所改进。新模式模拟的大气顶辐射能量收支为-0.6 W/m2，相比旧模式的结果（1.8 W/m2）有明显的差异。当没有设置云滴数浓度的较低限制时，新模式模拟的大气顶人为气溶胶的间接辐射强迫的全球年平均值为-1.9 W/m2。但是，当设定一个云滴数浓度的最低限制时，气溶胶的间接辐射强迫明显减小。(王志立)

3.3 气溶胶-气候耦合模式系统BCC_AGCM2.0.1_CAM气候态模拟的初步评估

讨论了国家气候中心第2代大气环流模式BCC_AGCM2.0.1 和加拿大气溶胶理化模式CAM 所组成的耦合模式系统对5 种典型气溶胶（硫酸盐、黑碳、有机碳、沙尘和海盐）和气候要素的模拟效果。结果表明，耦合系统对5 种典型气溶胶的模拟总体上比较合理，尤其是对硫酸盐、沙尘和海盐的模拟比BCC_AGCM2.0.1 原有的月平均气溶胶资料有很大的改进。耦合系统模拟的全球平均气候态参量与观测/再分析资料比较一致，在总云量、陆地表面温度和降水等方面要略优于原月平均气溶胶资料的模拟结果。耦合系统对沙尘和海盐气溶胶模拟的改进使得撒哈拉沙漠和南半球中纬度海洋大气顶净太阳辐射的模拟也有所改进，而这将直接影响地表温度尤其是陆地表面温度。而不同气溶胶方案在赤道海洋上引起的云反馈不仅引起辐射的改变，还将对降水产生明显影响。（王志立）

3.4 不同时刻污染减排对北京市PM2.5浓度的影响

利用空气质量模式Model-3/CMAQ及京津冀地区高分辨率排放源清单，针对有代表性的污染时段（2012年2月7—16日），设置了5种不同时刻的减排方案(在污染峰值提前4天、提前3天、提前2天、提前1天及当天减排)，对比在同样的减排比例下，不同时刻开始减排的效果差异。研究发现，提前采取减排控制措施比污染峰值当天开始减排对降低PM2.5浓度的影响更为明显，而且提前采取应急减排的时间越早，PM2.5浓度下降越明显。提前1天、2天、3天 减排海淀站和城6区峰值浓度下降率分别为23%和22%、31%和30%、39%和38%，均明显高于当天减排的峰值浓度下降率10%和9%。但随着提前天数的增加，PM2.5峰值浓度进一步下降的幅度越来越小，减排效益较之前显著降低。提前4天减排海淀站和城6区峰值浓度下降率分别为40%和39%，提前4天减排和提前3天减排对降低污染峰值日PM2.5浓度的效果已没有太大差别。同时针对另一个污染时段（2012年1月11—20日）进行了相似的敏感性试验，得出了类似的结论。因此，针对某些污染事件的应急减排，综合考虑减排成本和减排效果，根据气象条件的预报，在可能引起重污染事件的不利气象条件来临时提前2～3天采取减排措施效果最好，既能有效降低PM2.5浓度，也可以避免因盲目长时间减排造成的成本过大。（安兴琴）

3.5 NASA／Goddard长波辐射方案在GRAPES_Meso模式中的应用研究

将NASA/Goddard的长波辐射方案引入到GRAPES_Meso模式中，对2006年4月中国地区进行了1个月的模拟试验，并与相应的NCEP再分析资料进行了对比分析。试验结果表明： 在模拟区域内，GRAPES_Meso模式24 h、48 h预报晴空大气顶向外长波辐射通量(OLRC)、地面接收到向下长波辐射(GLWC)分布形势与NCEP再分析资料具有较好的对应关系；模式24 h、48 h预报OLRC和相应NCEP再分析资料月平均误差百分比控制在-10%～+10%以内，GLWC月平均误差百分比比OLRC略大，但总体上两者误差在合理和可接受范围之内。模式24 h、48 h预报的OLRC和GLWC的距平相关系数都在0.93以上，标准误差都在31 W/m2以内，GLWC预报与NCEP再分析资料的相关性比OLRC略好，OLRC与NCEP再分析资料的标准误差比GLWC小。本文研究结果表明，引入NASA/Goddard的长波辐射方案后的GRAPES_Meso模式整体上能够较好地预报OLRC和GLWC，该辐射方案可以作为模式GRAPES_ Meso的备选辐射方案之一。（王宏）

3.6 对流层气溶胶的直接气候效应对平流层的影响

通过 WACCM-3模式中气溶胶光学厚度与卫星资料的对比发现，模式可以很好地再现全球气溶胶的主要分布特征，但在一些区域还存在数值上的差异。利用数值试验研究了对流层气溶胶的直接气候效应对平流层气候的影响。结果表明，对流层气溶胶对平流层气候有明显影响，平流层化学过程在这一影响中起重要作用，而对流层气溶胶对平流层辐射的影响不是其直接气候效应对平流层影响的主要原因。其机制可能是对流层气溶胶改变对流层的辐射平衡，影响对流层的温度和大气环流，进而影响行星波的上传，使得平流层气候发生变化；影响区域主要位于高纬度和极地地区，南半球的变化比北半球大，温度变化最大达10 K，纬向风变化最大可达12 m/s，臭氧体积分数最多减少0.8×10-6。（刘煜）

3.7 城市排放与输送对北京上甸子站温室气体本底观测的影响分析

以北京上甸子区域大气本底站CO2和几种典型卤代温室气体（HFC-134a、PFC-218 和HCFC-22）浓度在线观测为例，统计分析并匹配计算了各风向浓度距平与浓度载荷，探讨了各季节城市排放和输送对上甸子站温室气体本底观测的影响。研究期间，CO2本底数据比例约为21.2%，受局地和城市排放与输送影响，非本底浓度比本底浓度偏高（3.7±1.3）×10-6；HFC-134a和PFC-218浓度距平和浓度载荷的特征反映了2个物种源区特征的差别；HCFC-22浓度特征与空调制冷剂夏高冬低的季节排放规律相一致。(姚波)

3.8 利用FLEXPART模式反演中国区域SF6排放量

六氟化硫( SF6) 是一种长寿命卤代温室气体，被列为《京都议定书》限排物质。随着经济高速发展，中国的排放量受到世界各国的关注。采用传统的“自下而上”清单方法估算排放量时，所需排放因子、活动水平数据的准确性和时效性存在较大局限。因此，本文利用拉格朗日粒子扩散模式FLEXPART，结合2009 年北京上甸子区域大气本底站浓度观测资料，尝试建立中国区域排放量的反演方法。结果表明，初步反演的2009年中国区域排放量为1.25×103（0.53×103～1.97×103）t，与文献结果相当，源排放量的不确定性从1.05×103t减小到0.72×103t。与先验源相比，反演源的相关系数从0.37提高到0.43，均方根误差减小了2.64%。(安兴琴)

3.9 不同气象条件下的气溶胶对暖云特征变化影响的卫星观测研究

考虑不同气象条件，研究了长时间序列的夏季长三角地区（YRD）和下风向的中国东海（ECS）等2个区域的气溶胶-暖云相互作用（ACI）。气溶胶和云特征数据来自于MODIS/Aqua Level 2，气象场数据来自NCEP再分析资料。为了减少气象条件对气溶胶-暖云相互作用统计分析的影响，本研究主要考察了不同云顶气压(CTP)、相对湿度(RH)、气压垂直速度(PVV)和下对流层稳定度(LTS) 条件下的ACI。结果表明，ECS地区的云滴有效半径(CDR)随气溶胶光学厚度增加而减少，而在YRD存在相反的变化趋势。再研究气溶胶对云量（CF）影响时，考虑了CTP和RH等2个气象参数。当气溶胶变化较小时，无论RH大小，YRD地区的CF随气溶胶的增长速度明显快于ECS地区。因此，本研究认为云的水平覆盖特征的改变主要由气溶胶而非相对湿度这一气象特征驱动。同时，针对AOD-CF、AOD-CTP的联合统计分析结果表明，CTP对AOD-CF相互作用非显著。本研究也考察了不同LTS和PVV条件下的CDR-AOD相互关系，发现了2个地区在大气热力条件相对稳定时，CDR随AOD增加而减少。而在大气不稳定时，存在截然相反的结果。通过研究不同动力条件对ACI的影响，发现在大气上升的时候，陆地和海洋2个典型地区的CDR随气溶胶变化存在一个更显著的改变，一个可能的解释是上升气流更有利于促进云滴的形成。总之，在云内存在更为复杂的热力和动力条件影响下，很难把观测到的云特征的改变完全归结为气溶胶。（郭建平）

3.10 西藏地面和卫星观测降水的日变化特征及其影响因子

基于2010—2011年2年夏季加密的西藏地区自动气象站和卫星降水产品（CMORPH），首次得到了该地区空间覆盖度最为广阔而全面的降水日变化特征。约60%站点的最大降水量和降水频次的峰值出现在下午-傍晚时分。由CMORPH数据也得到了同样的日变化特征，但它没有抓住有些站点临近中午的上午峰值。观测到的降水峰值时刻基本与该时刻附近容易出现降水的天气条件吻合。从空间上来说，没有明显的自西到东的日变化传输过程，表明该地区的降水主要由局地对流或环流而非大尺度环流导致，因此，该地区的降水日变化特征主要取决于地形和地形特征。进一步研究发现，降水峰值存在明显的地理依赖，即从山区的白天降水峰值过渡到山谷和湖泊（地形较低地区）的傍晚-夜间降水峰值。位于山峰（山谷）的站点在接近中午或午后时刻（傍晚时分）容易出现降水峰值。总体而言，无论降水量或降水频次，均出现类似的地形依赖特征，表明山谷环流效应（山谷风）在大（中）尺度降水特征比较弱的情况下对本地的降水峰值存在显著影响。同时，针对西藏空间异质的降水日变化特征提出了一种可能的机制，即在分析青藏高原降水日变化时空分布特征时，不仅需要考虑高原尺度的大尺度环流特征，更要考虑由复杂地形导致的局地环流因子的影响。（郭建平）

3.11 基于观测和模式模拟的华北地区山区和平原站点的降水和大气污染研究

利用华北太行山地区7个站点（4个平原站＋3个高山站）40年夏季的日平均能见度和小时降水数据，分析了其时间变化趋势。发现所有站点的夏季降水量均没有出现明显的变化趋势，而同期随着能见度减少，出现了小雨减少而大雨增加的趋势。小雨的减少表现在由地形降水和中尺度层云降水等产生的两类降水上。同时观测到的不同能见度、降水和地形因子变化趋势表明存在明显的气溶胶间接效应。同时，也深入分析了诸如可降水、对流有效位能、垂直风切变等大尺度环境因子对降水的潜在影响，发现他们之间不存在明显的内在直接联系。为了验证由观测得到的关于存在的气溶胶间接效应假设，使用了带谱分辨微物理方案的WRF模式进行云解析尺度模拟研究。模式模拟结果进一步确认了气溶胶间接效应是导致山区小雨雨量和降水频次减少的主要原因。当不考虑地形影响时，小雨对大气污染的效应出现相反的结果，表明地形可能是山区和平原站观测到不同的小雨变化的原因之一。（郭建平）

3.12 沙尘输送和沉降以及对黄海浮游植物生长的影响

利用地面PM10浓度、天气现象观测和卫星反演的气溶胶和海洋颜色数据，结合沙尘的数值模拟和后向追踪轨迹， 对发生于2010年19—22日的一次强沙尘过程及其对黄海浮游植物的影响进行了研究。研究发现，沙尘天气发生期间叶绿素a增加了4倍，而且10～14天之后， 浮游植物量显著增加。 严重沙尘天气带来的铁离子使得黄海南部的叶绿素a增加了10%～68%。研究结果表明，沙尘暴发生时给黄海地区带来的生物性养分有利于该地区浮游植物的成长。（王宏）

3.13 中国及东亚其他地区不同区域至酸性物质的湿沉降：采样升级的NAQPMS模式模拟研究

研究源与受体关系的传统方法是开展敏感性模拟，但是这种方法对涉及到非线性的二次形成的污染物（如臭氧、硝酸盐等）的研究存在弱点。本研究在嵌套空气质量预测模拟系统（NAQPMS） 基础上建立了一种在线源追踪方法，并首次将其与云过程模块耦合。新的模式不仅能更精确地确定硫酸盐、硝酸盐和铵盐总的湿沉降量，而且可追踪酸性物质的前体物。研究结果表明：（1）华东和华中是2个主要的污染物输出区，对其他区域的湿沉降分别具有15%～30%和10%的影响；（2）除了以上2区域外，我国西南和东北区域的酸沉降也达到或超过了各自环境条件下的临界负荷（图5）。（徐晓斌）

3.14 1-硝基芘和1,2-萘醌的联合细胞毒性和致DNA损伤

以人肺上皮细胞A549为研究对象，运用MTT方法检测1-硝基芘（1-NP）处理后A549的细胞存活率；测定细胞培养液中乳酸脱氢酶（LDH）的漏出率，评价细胞膜损伤；运用彗星试验检测DNA损伤；通过荧光探针的方法测定细胞内产生的活性氧自由基（ROS）。通过1,2-萘醌（1,2-NQ）预先染毒24 h，再使用1-NP染毒24 h的方法，评估1-NP和1,2-NQ对A549的联合细胞毒性和DNA损伤。结果表明，1-NP对A549暴露24 h和48 h的半致死浓度（LC50）分别为5.2 μmol/L和2.8 μmol/L。LC50随着染毒时间的增加而降低，提示暴露时间越长1-NP的细胞毒性越强。A549在1、2、3和4 μmol/L浓度的1-NP染毒下，DNA损伤显著增强，ROS水平不断升高，呈现剂量-效应关系（P＜0.05）；但LDH漏出率无显著变化。1,2-NQ（5 μmol/L）预染毒A549细胞24 h，能明显减弱1-NP造成的DNA损伤和ROS升高。结果说明，1,2-NQ预处理可能通过抑制1-NP暴露产生的ROS，来降低A549的DNA损伤。（李怡）

3.15 大气颗粒物携带醌类物质引发细胞毒性以及DNA损伤：氧化应激作用

大气颗粒物对人体有重要的健康影响。已有证据表明，颗粒物上携带的醌类物质可能通过氧化应激造成损伤，但是，肺部细胞的DNA损伤是否与醌类物质氧化应激有关，还缺乏相关研究。本研究选择了5种代表性醌类物质，在肺部上皮A549细胞中，研究了它们引发氧化应激的能力以及相应的DNA和其他生物学意义的损伤。这些醌类物质能够因剂量-效应引发细胞内Ca2+浓度增加，表明氧化应激是一个重要的途径。本研究结果再次证明了大气颗粒物对健康影响的重要性（李怡）

图1 北京空气样品GC×GC-qMS（a）和GC×GC-FID（b）的色谱图Fig. 1 GC × GC-qMS (a) and GC × GC-FID (b) chromatograms of a Beijing air sample

图2 MeteoInfo软件主界面及站点数据图形示例Fig. 2 MeteoInfo GUI and sample plot from station data

图3 中国气象局大院站点冬季PAN、O3、Ox、CO、NOx和气温的平均日变化(垂直线段表示各平均值的平均标准偏差)Fig. 3 Diurnal cycles of PAN, O3, Ox, CO, NOx, and air temperature at the CMA site during the wintertime. The vertical bars represent one standard error of the mean

图4 中国气象局（CMA）、上甸子（SDZ）和固城（GCH）3个站点CO和NOx均值体积分数变化Fig. 4 Variation of the monthly CO and NOx concentrations at the CMA, SDZ and GCH stations

图5 模拟的S（a）、N（b）、NH4+（c）的沉降空间分布以及东亚区域2007年3种致酸性物质模拟值和观测值的比较（d）（（d）中的黑点和红点分别表示来自东亚其他站点和中国境内站的观测数据）Fig. 5 Simulated patterns of wet deposition of (a) S, (b) N, (c) NH4+ and (d) scatter plot of the three acidifying substances over East Asia during 2007. Black and red points in (d) represent the observation data from other sites located in other East Asia and in China, respectively

Progress in Atmospheric Composition and Atmospheric Chemistry Research

In 2014, the Institute of Atmospheric Composition completed several tasks and made obvious progress in analytical methods, comparison and verif cation, quality control, observation of atmospheric composition and atmospheric chemistry process, model development and implementation, and in assessing the impact of atmospheric composition and related factors on climate, weather, and human health.

1 Analytical methods, comparison and verif cation and quality control

1.1 Establishment of the integrating sphere calibration method for China aerosol remote sensing network Cimel sunphotometer

Based on the integrating sphere traced from the National Institute of Standards and Technology (NIST, USA), a sphere calibration method and protocol for the China aerosol remote sensing network (CARSNET) Cimel sun photometer was established. Four CE318 sun photometers were verified using the proposed calibration method and operational protocol. The calibration results showed that the instrument coeff cients differed by less than 3% for visible (～5% for infrared) wavelengths from the original ones stated by Cimel electronique. In situ validation experiment data showed that radiances at ±6° measured by a sun collimator (aureole) were consistent with those measured by a sky collimator (sky), under both almucantar (ALMUC) and principal plane (PPLAN) scenarios. Differences at all wavelengths were less than 1%, indicating that the method and protocol are suitable for CARSNET f eld sun photometer calibration, and would benef t data quality and accuracy of network observations. (Che Huizheng)

1.2 Coupling of comprehensive two-dimensional gas chromatography with quadrupole mass spectrometry (GC×GC-qMS): Application to the identification of atmospheric volatile organic compounds

Observation data of atmospheric volatile organic compounds (VOCs) are highly needed in air quality assessment, photochemical mechanism study, and emission control policy-making, while it has been a challenge to accurately and comprehensively measure them. Comprehensive two-dimensional gas chromatography (GC×GC) is one of the advanced techniques in analysis of complex mixtures, providing a good choice for measurement of VOCs. However, the requirement for a fast detector limits the application of quadrupole mass spectrometry (qMS) in GC×GC analysis. This paper presents a method on how to apply a common qMS detector coupled with GC×GC to the identif cation of atmospheric VOCs. About 125 VOCs including alkanes, alkenes, aromatics, oxygenated hydrocarbons, and halocarbons were identif ed in the measurement of standard gas mixtures and/or urban air samples from Beijing. The results were applied to the analysis of GC×GC-FID by one to one correspondence of the equivalent peaking compounds between the GC×GC-FID and GC×GC-qMS chromatograms, and the retention times of the identif ed components in GC×GC-FID in turn underwent the qualitative analysis without the further help of MS. The wrap-around phenomenon which may confuse the match of peaks was discussed in detail. The co-use of GC×GC-FID and GC×GC-qMS in the identification process makes the GC×GC device more affordable and the qualitative and quantitative analysis more robust. The method and the identif ed results can be further used to analyze other volatiles (Fig. 1). (Wang Ying)

1.3 QA/QC method for and assessment of atmosphere background CO2 sampling and analysis

To strengthen scientific management and sharing of greenhouse gas data obtained from atmospheric background stations in China，it is important to ensure the standardization of quality assurance and quality control methods for background CO2sampling and analysis. The observation and study of atmospheric greenhouse gases in the Waliguan station (Qinghai) by CMA were begun in 1980s, with rich experience in data sampling，analysis and processing having been accumulated. In this study, the QA/QC method for atmospheric CO2concentration observation and analysis by portable f ask sampling and the CRDS system are discussed in detail. Then, several key steps of this method are evaluated. Finally, by using this method, the variation features of the three typical regions,, atmospheric background CO2concentration are preliminarily analyzed. (Liu Lixin)

1.4 Study of atmospheric CO2 mole fractions at the Longfengshan WMO/GAW regional station

Out of the in-situ observation results of atmospheric CO2mole fractions from two levels (10 m and 80 m above the ground) at Longfengshan (LFS) regional background station in Heilongjiang Province from January 2009 to December 2011, this study mainly focused on the lower (10 m) level (a.g.l.). The results indicate that the observed data from 10 m were strongly affected by the local sources/sinks. The differences between the 10 m and 80 m results were relatively small during the daytime (08:00–17:00) with values being lower than (0.5±0.5)×10-6. In spring, summer and autumn, higher CO2mole fractions were observed when surface winds came from the E-ESE-SE-SSE sectors, while, in winter, surface winds from the N-NNW-NW-WNW sectors obviously enhanced the observed values. Generally, lower CO2values were accompanied with higher wind speed in the four seasons. This phenomenon was most obvious in winter. Based on the analysis of the observed diurnal cycle and the local meteorological conditions, the observed data from 10 m were filtered into background/non-background events. About 30.7% valid hourly data turned out to be regional background representative. The background CO2variation displayed a peak in winter and a valley in summer with a seasonal peak to peak amplitude of (36.3±1.4)×10-6, which was higher than the values at similar latitudes from marine boundary layer (MBL) references and WMO/GAW stations. The annual CO2increasing rate at LFS was roughly estimated to be 2.4×10-6. (Fang Shuangxi)

1.5 MeteoInfo: GIS software for meteorological data visualization and analysis

MeteoInfo is a suite of software tools which has been developed for meteorological data visualization and analysis. It includes a .NET class library for software developers and a desktop application for end users. MeteoInfo also supports several basic GIS functions and can read common meteorological data formats such as NetCDF and GRIB. Complex meteorological analyses of grid and station data can be processed using provided data models. The class library can be conveniently used to develop software routines for manipulating spatial and meteorological data. The desktop application has a user friendly GUI and is a powerful tool to view and examine meteorological data sets. MeteoInfo can also be run automatically using the IronPython scripting language (Fig. 2). (Wang Yaqiang)

2 Observational studies of atmospheric compositions and related properties

2.1 Atmospheric sulfur hexafluoride (SF6) in-situ measurements at the Shangdianzi regional background station in China

We present in-situ measurements of atmospheric sulfur hexafluoride (SF6) conducted by an automated gas chromatograph-electron capture detector system and a gas chromatography/mass spectrometry system at a regional background site, Shangdianzi, in China, from June 2009 to May 2011, in which the system for observation of greenhouse gases in Europe and Asia and Advanced Global Atmospheric Gases Experiment (AGAGE) techniques were used. The mean background and polluted mixing ratios for SF6during the study period were 7.22×10-12and 8.66×10-12respectively. The averaged SF6background mixing ratios at Shangdianzi were consistent with those obtained at other AGAGE stations located at similar latitudes (Trinidad Head and Mace Head), but larger than AGAGE stations in the Southern Hemisphere (Cape Grim and Cape Matatula). SF6background mixing ratios increased rapidly during our study period, with a positive growth rate at 0.30×10-12yr−1. The peak to peak amplitude of the seasonal cycle for SF6background conditions was 0.07×10-12while the seasonal f uctuation of polluted conditions was 2.16×10-12during the study period. Peak values of SF6mixing ratios occurred in autumn when local surface horizontal winds originated from W/WSW/SW/SWS/S sectors, while lower SF6mixing ratios appeared as winds originated from N/NNE/NE/ENE/E sectors. (Yao Bo)

2.2 Background variations of atmospheric CO2 and carbon-stable isotopes at Waliguan and Shangdianzi stations in China

Observational data from 2007 to 2010 at the Waliguan (WLG) and Shangdianzi (SOZ) stations in China are used to study atmospheric CO2, its δ13C composition, and their potential relationship with sources and sinks. Results suggest that at WLG station, both CO2and δ13C feature a long-term variation and seasonal cycle that correlate well with each other. CO2and δ13C inter-annual variations indicate terrestrial ecosystem’s alteration in source-sink by season in the mid- to high-latitude Northern Hemisphere. CO2annual means vary from 384.0×10-6to 390.2×10-6, increasing in an approximately linear manner averagely at an annual growth rate of (2.1±0.1)×10-6. The δ13C annual means vary from -8.30‰ to -8.35‰, decreasing almost linearly and averagely at an annual rate of -0.02‰ ± 0.001‰. Given the terrestrial biosphere and anthropogenic activities at SDZ station, the CO2annual means vary from 385.1×10-6to 390.6×10-6, approximately increasing linearly and averagely at an annual growth rate of (1.8±0.1)×10-6. The peak-to-peak annual seasonal amplitude is 23.0×10-6. The δ13C annual means vary from -8.27‰ to -8.36‰ between 2009 and 2010. Mean values of (-25.44±0.72)‰ and (-21.70±0.67)‰ for the respective sources are obtained at WLG and SDZ. The estimated δsvalues are rather negative in winter and spring than in summer and autumn at WLG. While because substantial C4photosynthesis occurs in summer and biomass burns in winter, the estimated δsvalues at SDZ are heavy throughout the year and rather positive than those at WLG. (Liu Lixin)

2.3 In situ measurement of atmospheric CO2 at the four WMO/GAW stations in China

Atmospheric carbon dioxide (CO2) mole fractions were continuously measured from January 2009 to December 2011 at four atmospheric observatories in China with cavity ring-down spectroscopy instruments used. The stations are Lin’an (LAN), Longfengshan (LFS), Shangdianzi (SDZ), and Waliguan (WLG), which are either regional (LAN, LFS, SDZ) or global (WLG) under the World Meteorological Organization’s Global Atmosphere Watch program (WMO/GAW). LAN is located near the megacity of Shanghai, in China’s most economically developed region. LFS is in a forest and rice production area, close to the city of Harbin in northeastern China. SDZ is located 150 km northeast of Beijing. WLG, boasting the longest record of measured CO2mole fractions in China, is a high-altitude site in northwestern China registering background CO2concentration. The CO2growth rates are (3.7±1.2)×10-6yr-1for LAN, (2.7±0.8)×10-6yr-1for LFS, (3.5±1.6)×10-6yr-1for SDZ, and (2.2±0.8)×10-6yr-1for WLG during the period of 2009 to 2011. The highest annual mean CO2mole fraction of (404.2±3.9)×10-6was observed at LAN in 2011. A comprehensive analysis of CO2variations, their diurnal and seasonal cycles as well as an analysis of the inf uence of local sources on the CO2mole fractions allow for a characterization of the sampling sites and of the key processes driving the CO2mole fractions. These data form a basis to improve our understanding of atmospheric CO2variations in China and the underlying f uxes using atmospheric inversion models. (Fang Shuangxi)

2.4 Estimation of regional background concentration of CO2 at Lin,an station in Yangtze River Delta, China

A new method of extracting regional background concentration of CO2in Yangtze River Delta was developed based on the observations of both black carbon concentration and meteorological parameters. The concentrations of CO2and black carbon were observed at Lin,an regional background station from 2009 to 2011. The regional background concentration of CO2in Yangtze River Delta was obtained by means of this new method, and the impact of human activities on CO2concentration in this area was also assessed. The results show that the regional background concentration of CO2extracted by this approach was comparable to the values obtained by R statistical f lter method, and moreover this new method was better at picking up episodes heavily polluted by anthropogenic emissions. The annual regional average background concentration of CO2in Yangtze River Delta from 2009 to 2011 was approximately (404.7±8.2)×10-6, (405.6±5.3)×10-6and (407.0±5.3)×10-6, respectively, much higher than global average value, indicating the distinct characteristic of this region. The anthropogenic emissions from Yangtze River Delta had significant influence on the concentration of CO2in this area, increasing the local value by roughly 9.1×10-6. (Fang Shuangxi)

2.5 A case study of short-term f uctuation in atmospheric concentration of halogenated greenhouse gases at Shangdianzi regional background monitoring station

By means of trajectory analysis method and footprint analysis method, combined with the online observed concentration of H-1301, HCFC-22, CFC-11 and SF6, a typical case about short-term f uctuation of halogenated greenhouse gases at Shangdianzi background station during 7–12 September 2012 was analyzed. The results show that before the occurrence of pollution, air masses at 12:00 BT 7 September 2012 are mainly from the far-away north and northwest, with a long horizontal transport distance, rapid moving speed and high vertical height; meanwhile, the corresponding halogenated greenhouse gases concentrations are relatively low, which are 4×10-12, 350×10-12, 260×10-12and 10×10-12for H-1301, HCFC-22, CFC-11 and SF6, respectively. However, on 9–10 September 2012, a certain percentage of air masses convolutes over the south of the station with a short horizontal transport distance and low vertical height, moving slowly in the boundary layer, thus hindering the spread of pollutants in the boundary layer and resulting in relatively high halogenated greenhouse gases concentrations. Such situation contributes a lot to the short-term rapid growth of concentration levels and H-1301, HCFC-22 and CFC-11 respectively reach the peak concentrations of 45×10-12, 200×10-12and 310×10-12at 12:00 BT 9 September and SF6reaches 28×10-12at 03:00 BT 10 September. On 11 September, the convoluting air mass in the southwest direction disappears and on 12 September, air masses all f ow from the far-away northwest and have rapid moving trajectories. The result by footprint analysis method is the same as that by the trajectory analysis, which is that on 7–8 September, regions with a high sensitivity coeff cient are mainly located in the north of the station; on 9–10 September, they are seen mainly in the south of the station. Then on 11 and 12 September, the regions with high sensitivity coeff cients in the south of the observation station disappeared. In addition, a flow field analysis also showed that the circulation pattern on 9 and 10 September is favorable for the accumulation of pollutants in the observed region, resulting in the short-term lift of pollutants’ concentrations. (An Xingqin)

2.6 In-situ measurement of atmospheric methyl chloroform at the Shangdianzi GAW regional background station

An in-situ GC-ECD monitoring system was established at the Shangdianzi GAW regional background station (SDZ) for 2-year atmospheric methyl chloroform (CH3CCl3) measurement. Robust extraction of baseline signal f lter was applied to the CH3CCl3time series to separate background and pollution data. The yearly averaged background mixing ratios of atmospheric CH3CCl3were (9.03±0.53)×10-12in 2009 and (7.73±0.47)×10-12in 2010, and the percentages of the background data to the whole data were 61.1% in 2009 and 60.4% in 2010, respectively. The yearly background CH3CCl3mixing ratios at SDZ were consistent with the Northern hemisphere background levels observed at Mace Head and Trinidad Head stations, but lower than the results observed at sites in South China and some Chinese cities from 2001 to 2005. During the study period, background mixing ratios exhibited a decrease at a rate of 1.39×10-12yr-1in trend. The wind direction with the maximum CH3CCl3mixing ratio was from the southwest sector and with the minimum one was from northeast sector. The differences between the maximum and the minimum average mixing ratios in the 16 wind directions were 0.77×10-12(2009) and 0.52×10-12(2010). In the different 16 wind directions, the averaged mixing ratio of CH3CCl3in 2010 was lower than those in 2009 by 1.03 ×10-12–1.68×10-12. (Yao Bo)

2.7 Influence of downward air mass transport on the variability of surface ozone at Xianggelila regional atmospheric background station, Southwest China

In situ measurements of ozone (O3), carbon monoxide (CO) and meteorological parameters were made from December 2007 to November 2009 at the Xianggelila regional atmospheric background station (28.006°N, 99.726°E, 3580 m.a.s.), Southwest China. It was found that both O3and CO peaked in spring while the minima of O3and CO occurred in summer and winter, respectively. A normalized indicator (marked as “Y ”) on the basis of the monthly normalized O3, CO and water vapor, is proposed to evaluate the occurrence of O3downward transport from the upper, O3-rich atmosphere. This composite indicator has the advantage of being less inf uenced by the seasonal or occasional variations of individual factors. It is shown that the most frequent and effective transport occurs in winter (accounting for 39% of the cases when Y is larger than 4), which makes a signif cant contribution to surface O3at Xianggelila. A 9.6×10-9increase (21.0%) of surface ozone is estimated based on the impact of deep downward transport events in winter. A case of strong O3downward transport event under the synoptic condition of a deep westerly trough is studied by a combined analysis of the Y indicator, potential vorticity, total column ozone and trajectory. Asian monsoon plays an important role in suppressing O3accumulation in summer and fall. The seasonal variation of O3downward transport, as suggested by the Y indicator at Xianggelila, is consistent with the seasonality of stratosphere-to-troposphere transport and the subtropical jet stream over the Tibetan Plateau. (Zheng Xiangdong)

2.8 Wintertime peroxyacetyl nitrate (PAN) in the megacity Beijing: The role of photochemical and meteorological processes

Previous measurements of peroxyacetyl nitrate (PAN) in Asian megacities were scarce and mainly conducted for relatively short periods in summer. Here, we present an analysis of the measurements of PAN, O3, NOx, etc. made at an urban site (CMA) in Beijing from 25 January to 22 March 2010. The hourly concentration of PAN averaged 0.70×10-9(0.23×10-9–3.51×10-9) was well correlated with that of NO2but not O3, indicating that the variations of the winter concentrations of PAN and O3in urban Beijing are decoupled with each other. Wind conditions and transport of air masses exert very signif cant impacts on O3, PAN, and other species. Air masses arriving at the site originated either from the boundary layer over the highly polluted N-S-W sector or from the free troposphere over the W-N sector. The descending free-tropospheric air was rich in O3, with an average PAN/O3ratio being smaller than 0.031, while the boundary layer air over the polluted sector contained higher levels of PAN and primary pollutants, with an average PAN/O3ratio being 0.11. These facts related with transport conditions can well explain the observed PAN-O3decoupling. Photochemical production is important to PAN in the winter over Beijing. The concentration of the peroxyacetyl (PA) radical was estimated to be in the range of 0.0014×10-12–0.0042×10-12. The contributions of reaction from the formation and thermal decomposition to PAN’s variation were calculated and found to be signif cant even in the colder period in air over Beijing, with the production exceeding the decomposition (Fig. 3). (Xu Xiaobin)

2.9 Changing characteristics of NOx and CO emission at three sites in Beijing and its surrounding areas

To study the similarity and dissimilarity in the characteristic features of the ambient NOxand CO emission in different parts of the North China Plain (NCP), we observed the mixing ratios of CO and NOxin the surface layer air at three sites in the NCP, which are over 100 km apart from each other and in the prevailing SW–NE wind directions. The three sites are China’s Meteorological Administration (CMA), the Shangdianzi station (SDZ), and the Gucheng station (GCH), representing typically the urban area of Beijing, the regional background area of the NCP, and the rather seriously polluted rural area in North China, respectively. The results of our investigation show that from June 2008 to May 2009, the annual average concentration of NOxat CMA, GCH, and SDZ were (42.4±21.8)×10-9, (26.9±15.2)×10-9, and (13.8±5.5)×10-9, respectively, and those of CO were (1.13±0.37)×10-6, (1.11±0.62)×10-6, and (0.67±0.17)×10-6, respectively. At CMA and GCH, the monthly average concentrations of NOxand CO reached the corresponding maximum in winter and minimum in summer, whereas the highest monthly average concentration of CO at SDZ was observed in June (1.03×10-6). The concentrations of NOxat CMA, GCH, and SDZ turned to be 3.4, 3.6, and 1.8 times higher in winter than those in summer, respectively. The concentrations of CO at CMA, GCH, and SDZ were 1.8, 2.9, and 0.8 times higher in winter than in summer, respectively. The average diurnal variations indicated that the CO and NOxconcentrations of SDZ decreased to their minimum around noon, about 3–4 h earlier than those of GCH and CMA, and then increased gradually till evening, in response to the impact of transported pollutants on the gas concentrations of SDZ. The above dissimilarities in the diurnal variations can probably account for the different effects of emission sources and the air-mass transport on the concentrations of pollutants at the three sites. The time series of the daily average CO and NOxconcentrations show great similarities among the sites, revealing that the characteristic features were inf uenced by the common regional pollution and similar meteorological conditions. The observation data we have gained indicate fairly high CO level in the North China Plain in summer, which was probably caused by the outdoor combustion of wheat straw in large amount (Fig. 4). (Xu Xiaobin)

2.10 Characteristics of CO at Lin,an Station in Zhejiang Province

Background CO mole fractions were continuously measured at Lian’an background station in Zhejiang Province from September 2010 to February 2012 with Cavity Ring Down Spectroscopy (CRDS) system used. The diurnal variation of CO was strongly inf uenced by anthropogenic activities with two peaks occurring at 07:00–10:00 and 19:00–20:00 (Local time). The average daily mole fraction and amplitude in summer were the lowest among the four seasons with values being (314.3±7.6)×10-9(mole fraction, the same below) and (50.1±47.9)×10-9, respectively. The seasonal variations displayed peak values during winter-spring period and valley in summer, which was roughly consistent with those observed variations at other sites located in the Northern hemisphere such as Jungfraujoch in Switzerland and Waliguan in China. However, the average mole fractions were much higher than other stations. The amplitude of monthly CO mole fractions was (286.8±19.2)×10-9. The analysis of cluster to backward trajectories and surface wind inf uence might suggest that the non-background CO mole fractions at Lin’an station were mainly affected by the emissions from the megacities and industrial areas in the N-NNE-ENE sectors. The maximum enhancements in spring, summer and winter all occurred in ENE sector, with a maximum value being (106.3±58.0)×10-9in winter. (Fang Shuangxi)

2.11 Seasonal variation of ammonia and ammonium aerosol at a background station in the Yangtze River Delta region, China

The measurement of atmospheric NH3was conducted by means of passive samplers from September 2009 to December 2010 at Lin’an regional background station located in the economically booming Yangtze River Delta (YRD) region in East China. NH4+in f ne particles was also measured in 2010 at this site. The NH3concentration ranged from 0.1×10-9to 41.8×10-9, with the annual average being (16.5±11.2)×10-9in 2010. The daily NH4+concentrations ranged from 0.02 to 19.2 μg m-3, with an annual average of (4.3±3.5) μg m-3. NH3concentrations were highest in summer and lowest in winter, showing positive correlations with agricultural activities and temperature. The highest concentrations of NH4+were in autumn coinciding with the period of active open burning of agricultural residues. The mean mass ratio of NH3/NHxis estimated to be (0.8±0.1) during 2010, indicating that NHxwas mainly inf uenced by local sources around Lin’an. The air mass back trajectory analysis suggests that both local sources and long-distance transport play an important role in the observed ammonium aerosol at Lin’an station. High NHxdeposition in this regional background station suggests the urgency of reducing NH3emission in the YRD region. (Meng Zhaoyang)

2.12 Variability, formation and acidity of water-soluble ions in PM2.5 in Beijing

Daily PM2.5and hourly water-soluble inorganic ions in PM2.5and gaseous precursors were measured during June–November 2009 at an urban site in Beijing. The average mass concentration of the total watersoluble ions was 44 μg m-3, accounting for 38% of PM2.5. Sulfate (SO42-), nitrate (NO3-) and ammonium (NH4+) were dominant ions. The summer-fall difference in seasonal average mass concentrations was smaller than 30% for SO42-, but was up to a factor of 2.0 for NO3-and NH4+. A pronounced diurnal cycle was found for most ions and gaseous precursors and could be explained by their respective sources, formation mechanisms and meteorological conditions. The average oxidation/conversion ratios for SO42-(SOR), NO3-(NOR) and NH4+(NHR) were estimated to be 63%, 15% and 15%, respectively. The low NHR value suggests that NH3was mainly from local sources, the excessive existence of which thus was not a limiting factor in the formation of NH4+. As a result, the diurnal pattern of NH4+was similar to that of SO42-to some extent, but differed signif cantly from that of NH3. Based on the estimated H+concentration and acidity purity (f ), 75% of data samples were strongly acidic and a few percentages might be alkaline. Seasonal variations in aerosol acidity and chemical forms of major ions were also brief y discussed. (Zhang Yangmei)

2.13 Chemical composition and mass size distribution of PM1 at an elevated site in central east China

Size-resolved aerosol chemical compositions were measured continuously for 1.5 year from June 2010 to January 2012 with an aerosol mass spectrometer (AMS) to characterize the mass and size distributions (MSDs) of major chemical components in submicron particles (approximately PM1) at Mountain Tai (Mt. Tai), an elevated site in central east China. The annual mean mass concentrations of organic, sulfate, nitrate, ammonium, and chloride were 11.2, 9.2, 7.2, 5.8, and 0.95 μg m-3, respectively, which are much higher than those at most mountain sites in the USA and Europe, but lower than those at the near-surface urban sites in China. A clear seasonality was observed for all major components throughout the study, with low concentration in fall and high in summer, which is believed to be caused by seasonal variations in planetary boundary layer (PBL) height, near surface pollutant concentrations and regional transport processes. Air masses were classif ed into categories impacted by PBL, lower free troposphere (LFT), new particle formation (NPF), in-cloud processes, and polluted aerosols. Organics dominated the PM1mass during the NPF episodes, while sulfate contributed most to PM1in cloud events. The average MSDs of particles between 30 and 1000 nm during the entire study for organics, sulfate, nitrate, and ammonium were approximately log-normal with mass median diameters (MMDs) of 539, 585, 542, and 545 nm, respectively. These values are slightly larger than those observed at ground sites within the North China Plain (NCP), likely due to the relative aged and well-mixed aerosol masses at Mt. Tai. There were no obvious differences in MMDs during the PBL, LFT, in-cloud and polluted episodes, but smaller MMDs, especially for organics, were observed during the NPF events. During the PBL, NPF, and polluted episodes, organics accounted for major proportions at smaller modes, and reached 70% at 100–200 nm particles in the polluted events. In cloud episodes, inorganics contributed 70% to the whole size range dominated by sulfate, which contributed 40% to small particles (100–200 nm), while organics occupied 20%, indicating that sulfate is a critical chemical component in cloud formation. Seven clusters of air masses were classified based on 72 h back-trajectory analysis. The majority of the regionally dispersed aerosols were found to be contributed from short distance mixed aerosols, mostly originating from the south with organics and sulfate as major components. Air masses from long range transport always brought clean and dry aerosols which resulted in low concentrations at Mt. Tai. AMS-PMF (positive matrix factorization) was employed to resolve organics into subtype. Oxygenic organics aerosols (OAs) occupied 49%, 56%, 51%, and 41% of OAs in the four seasons respectively, demonstrating that most OAs were oxidized in summer due to strong photochemical reactions. Biomass burning OAs (BBOAs) accounted for 34% of OA in summer, which was mainly from f eld burning of agricultural residues, and coal combustion OAs (CCOAs) accounted for 22% of OA in winter, which was from heating. (Zhang Yangmei)

2.14 Characterization of chemical components of aerosol particles in various regions over China

In order to obtain the overall chemical “picture” of the aerosol pollution in various regions of China and discuss the further direction in pollution control, we need to assess and evaluate the concentration level, chemical composition and pollution sources region-by-region in China. Features of the chemical aerosol particles in China have been obtained, based on the analysis of six major chemical components (sulfate, nitrate, ammonium, mineral aerosol, organic and elemental carbon) from ground-based observation, all of which have undergone at least one-year-long measurement. The four most hazy regions out of the nine with characteristics of synchronous changes in visibility within China are also identif ed in areas like the region to the south of Beijing (also called the Hua Bei Plain and Guanzhong Plain); mostly the East China region with Yangtze River Delta; the South China region focused on the Pearl River Delta; and also the region of Sichuan Basin. Of the total mass of PM10in China, three major components account for ～20%–38% for mineral aerosol, ～14%–24% for sulfate, and ～11%–18% for organic carbon.

The heaviest aerosol pollution was found in the Hua Bei and Guanzhong Plain regions, with the annual mean concentrations being 35–47 µg m-3of sulfate (much higher than the 13 to 18 µg m-3of urban Beijing), 28–45 µg m-3of organic carbon (about 1.8 factors higher than 19–22 µg m-3of Beijing), 19–22 µg m-3for nitrate (2 times higher than 9.9–12 µg m-3of Beijing), 14–16 µg m-3for ammonium (still one factor higher than the 6.2–8.4 µg m-3of Beijing mean concentration), and the 9.1–12 µg m-3of elemental carbon which was similar to the level of Beijing. More than 50% mass of nitrate and organic carbon is attributable to coalcombustion, and the agricultural activity is the most important source for ammonium.

In the urban areas of East, South and Northeast China, the concentration levels of aerosol chemical components were similar to that in Beijing, but in urban areas of the Sichuan Basin, the annual mean concentrations were higher than that in Beijing, exhibiting heavy aerosol pollution there. In Lanzhou of Northwest China, the urban concentrations of aerosol chemical components were also similar to that in Beijing, except for much lower concentration in elemental carbon and slightly higher concentration of nitrate observed. In the remote desert area of Northwest China, the chemical concentrations of aerosol particles were far lower than that in Beijing, so were in the Tibetan and Yunnan-Guizhou Plateaus.

Coal-combustion, motor vehicle, urban fugitive dust and agricultural activities are found to be the four major pollution sources according to the aerosol chemical composition analysis made in different regions. Therefore, the future control of atmospheric aerosol pollutants should be directed to the following: strengthening coal desulfurization in addition to the power generation industry, further reducing coal produced emissions of NOx, organic carbon and its precursor gases, and effectively reducing ammonia emissions from agricultural activity, and effectively limiting the formation of secondary aerosol, especially sulfate and nitrate. (Zhang Xiaoye)

2.15 Characteristics of PM10 and its chemical components at Mount Tai

In order to better understand the chemical components and their variations of background aerosols in the North China Plain, 64 PM10samples were collected on the top of Mount Tai from June 2010 to July 2011. The mass concentration and seasonal variations of PM10as well as its nine water soluble irons, organic carbon (OC) and elemental carbon (EC) have been analyzed. The correlation analysis of various chemical components has also been performed. The annual average mass concentration of PM10is 68.4 µg m-3, of which inorganic salt accounts for 64.8%, carbon aerosol for 17.4%. The mass concentration of inorganic salt increases gradually from the Spring Festival, reaches its peak in summer, then decreases in autumn and comes to the lowest in winter. The mass concentration of OC increases from the Spring Festival to autumn and reaches the minima in winter. Similar pattern has been found in the mass concentration of EC; however, the concentrations of EC between summer and autumn are much smaller in difference. The ratio of secondary organic carbon (SOC) to OC is above 50% for all seasons with an annual average of 58.5%. A back trajectory analysis shows that when Mount Tai is mainly inf uenced by air masses from the south and megacities, mass concentrations of PM10and its components are high; while it is mainly inf uenced by air masses from the Northwest China through long distance transport, the mass concentrations of PM10and its components are much lower. (Wang Yaqiang)

2.16 The characteristics of particle number size distribution under typical meteorological conditions at Shangdianzi regional station in Beijing

By using the instruments of Twin Differential Mobility Particle Sizer (TDMPS) system and an Aerodynamic Particle Sizer, measurements of particle number size distribution (PNSD) in the range of 3 nm–10 μm were performed at Shangdianzi regional station. Based on the dataset in 2008, the characteristics of particle number size distribution at different meteorological conditions such as dust storm, new particle formation event and fog-haze day were investigated. On the dust storm day, the air mass originated from the northwest, with high wind speed. The coarse particle number concentration increased sharply and PM10mass concentration could reach up to milligrams per cubic meter. A typical “banana shape” new particle formation event occurred when the atmosphere background was quite dry, clean and clear, with the air mass coming from the northeast. The nucleation mode particle could grow signif cantly in size to around 80 nm, which has the potential to be activated as cloud condensation nuclei. The fog-haze day usually occurred when southwest air mass arrived, with the meteorological conditions being of high humidity. The conditions favored the f ne particles (＜1 μm) for accumulation. The case study showed the PNSD on haze-fog day was dominated by the accumulation mode and higher number concentration than on a haze-fog free day. The mass concentration of PM2.5could increase by 10 times on a haze-fog day, which is mainly contributed by f ne particles. On fog-haze days, the accumulation mode particles of high number concentration were mainly transported from the urban area. Thus the study of PNSD at rural sites could also provide information for the analysis of the complex emission sources in urban areas. (Shen Xiaojing)

2.17 Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements

In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It is found that Aerosol Optical Depth at 500 nm (AOD500nm) during nonpollution periods at all stations was lower than 0.30 and increased signif cantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500nmaverages increased from north to south during both polluted and non-polluted periods at the three urban sites in Beijing. The f ne mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The f ne mode fraction of AOD675nmwas higher than 80% for all sites during January 2013. The absorption AOD675nmat rural sites was only about 0.01 during pollution periods, while 0.03–0.07 and 0.01–0.03 during pollution and nonpollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The f ne mode effective radius in the pollution period was 0.01–0.08 μm, which was larger than that during non-pollution periods, while the coarse mode radius in pollution periods was 0.06–0.38 μm, which was less than that during non-pollution periods. The total, f ne and coarse mode particle volumes varied by 0.06–0.34 μm3, 0.03–0.23 μm3, and 0.03–0.10 μm3, respectively, throughout January 2013. During the most intense period (1–16 January), ARF at the surface exceeded −50 W m-2, −180 W m-2, and −200 W m-2at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately−30 W m-2in rural and −40–60 W m-2in urban areas. Positive ARF at the top of the atmosphere at the Huimin suburban site was found to be different from others as a result of the high surface albedo due to snow cover. (Che Huizheng)

2.18 A study of the meteorological causes of a prolonged and severe haze episode in January 2013 over central-eastern China

This paper employs meteorological observation data from surface and high-balloon stations, China Meteorological Administration (CMA) model T639 output data, NCEP reanalysis data, PM2.5observations and modeled HYSPLIT4 trajectory results to study the meteorological causes, including large-scale circulation and planetary boundary layer features, which led to the extended haze episode on January 6–16, 2013 in central-eastern China. It discusses the possible impact of pollutants transported from southern Hebei Province on Beijing. The results show that: (1) the re-adjustment of atmospheric circulation from a longitudinal to a latitudinal model provides a valuable interpretation of the large-scale circulation background to the haze episode experienced in the metropolitan regions of Beijing, Tianjin, Hebei and their surrounding regions; (2) the regional atmospheric stratif cation of the planetary boundary layer is stable and the mixing height is low, suppressing air turbulence in the planetary boundary layer and providing favorable meteorological conditions for the formation of haze; and (3) the southwesterly jet stream with wind speeds of 6–11 m s-1at a height of 850–950 hPa and the below-700 m air mass trajectory tracking established using the HYSPLIT4 model interdependently suggest a transport of pollutants from southern Hebei Province to Beijing at 850–950 hPa. (Wang Hong)

2.19 Aerosol optical properties under the condition of heavy haze over an urban site in Beijing, China

In January 2013, several serious haze pollution events happened in North China. Cimel sunphotometer measurements at an urban site in Beijing (Chinese Academy of Meteorological Sciences—CAMS) from 1 to 30 January 2013 were used to investigate the detailed variation of aerosol optical properties. It is found that Angstrom exponents were mostly larger than 0.80 when aerosol optical depth values were higher than 0.60 in the urban region of Beijing during January 2013. The aerosol optical depth (AOD) in the urban region of Beijing remained steady at approximately 0.40 before the haze happened and then increased sharply to more than 1.50 at 500 nm with the onset of haze, which suggests that the f ne mode AOD is a factor of 20 of the coarse-mode AOD during a serious haze pollution event. The single scattering albedo was approximately 0.90±0.03 at 440, 675, 870 and 1020 nm during the haze pollution period. The single scattering albedo at 440 nm as a function of the f ne-mode fraction was relatively consistent, but it was highly variable at 675, 870 and 1020 nm. Except on January 12 and 18, all the f ne-mode particle volumes were larger than those of coarse particles, which suggested that f ne particles from anthropogenic activities made up most of the haze. An analysis of aerosol type classif cation showed that the dominant aerosol types can be classif ed as “mixed”and “urban/industrial (U/I) and biomass burning (BB)” categories during the heavy haze period of Beijing in January 2013. The mixed category occurrence was about 31%, while the U/I and BB was about 69%. (Che Huizheng)

2.20 Aerosol optical properties retrieved from a Prede skyradiometer over an urban site in Beijing, China

SKYNET is an international research network of ground-based Prede sky radiometers for the observation and monitoring of aerosol-cloud-radiation interactions in the atmosphere. The algorithm developed by SKYNET is SKYRAD.pack, which can be used to process the measurement data by Prede instruments. In this study, the latest SKYRAD.pack software (Version 5.0) has been used to retrieve the aerosol optical properties measured by a SKYNET Prede sky radiometer over an urban site in Beijing, China. Continuous data have been processed over a two-year period, and inversion products, including aerosol optical depth (AOD), Ångström exponent (α), volumes of different aerosol particle size distributions, and single-scattering albedos (SSA), have been analyzed. AOD values were found to vary from 0.11 (5th percentile) to 1.14 (95th percentile) with a median of 0.34 at 500 nm, and the maximum and minimum seasonal α values in Beijing were 1.05±0.36 in summer and 0.82±0.39 in spring. SSA values are higher in summer and spring with a similar value of 0.96±0.03, but lower in winter with a value of 0.93±0.04 at 500 nm. Aerosol particles in Beijing clearly demonstrated bimodal size distributions throughout the year: there were coarser particles in spring and finer particles in summer. The α values increased with AOD, indicating that f ne particles play an important role in the optical properties of aerosols in Beijing. Dust type aerosol occurrence accounted for 4.1%, 5.1%, 0.5%, and 1.2% of all measurements data in spring, summer, autumn, and winter, respectively, according to the dust criteria threshold (α＜0.47 and SSA400nm−SSA1020nm＜0.018). (Che Huizheng)

2.21 A multi-source observation study of the severe prolonged regional haze episode over eastern China in January 2013

By employing visibility observation of PM10, SO2and NO2concentration, MODIS AOD at 550 nm, CARSNET AOD at 440 nm, and CALIPSO extinction coefficient at 532 nm, we studied the air pollution condition of a severe haze episode occurring on 6–16 January 2013 over eastern China. It is found that this severe pollution episode of large area haze was accompanied with low visibility, high PM10and AOD in eastern China. The most polluted regions are the Jing-Jin-Ji and its closely neighboring ones including central and southern Hebei, western Shandong and northern Henan provinces. The haze pollutants were spread to the offshore area of from 125°E to the east of China, and even affected the whole ocean surface to the west of 140°E. The PM10variation trend shows a strong linkage among the big cities in Jing-Jin-Ji, and their closely surrounding cities, indicating the possible inter-transport of pollutants among them. The suburban areas of megacities suffered the similar serious pollution to the urban regions during this severe haze episode. Most aerosol pollutants concentrated in boundary layers of below 1500 m vertical height, in particular, the vertical heights of 100–800 m above the ground which are most intensive. (Wang Hong)

2.22 Column-integrated aerosol optical and physical properties at a regional background atmosphere in North China Plain

The AERONET level 2.0 data at Xinglong station from February 2006 to July 2011 were used to characterize the aerosol optical and physical properties, including temporal variability, aerosol absorption, classif cation and properties under dust and haze conditions. The annual mean aerosol optical depth (AOD) and extinction Angstrom exponent (EAE) are 0.28±0.30 and 1.07±0.38, respectively. The seasonal variations of AOD440nmare higher in spring (0.40±0.3) and summer (0.40±0.42) than in autumn (0.20±0.22) and winter (0.19±0.21). The EAE is low in spring (0.96±0.43) and high in summer (1.22±0.38). The EAE is ～1.25 with an absorption Angstrom exponent (AAE) of ～1.0–1.5 at Xinglong station, which indicates that the dominant type is mixed aerosol (accounting for 88.2% at AAE＞1.0). Almost all of the dust observations occurred in spring. The volume concentrations of both f ne and coarse mode particles increase with increasing AOD. In spring, the increase of coarse particles is greater than that of f ne aerosols; however, the reverse phenomenon is observed for other seasons. The high AOD at Xinglong station could be associated with the growth of f ne mode aerosols and the addition of coarse mode particles. This background station is not only impacted by dust aerosols from northwest China and south Mongolia but also inf uenced by long-range transport of anthropogenic aerosols from southern urban and industrial regions. The mean AOD was 1.49 on the dust day, while AOD was 1.10 on the haze day. The mean EAEs were 0.09 and 1.43 on dust and haze days, respectively. (Che Huizheng)

2.23 Dust aerosol drives upward trend of surface solar radiation during 1980–2009 in the Taklimakan Desert

Long-term trend of surface solar radiation (SSR) in the Taklimakan Desert (TD) during 1980–2009 and its relationship with total cloud cover (TCC), low cloud cover (LCC), water vapor content (WVC) and aerosol optical depth (AOD) were investigated. Annual mean SSR has increased by 1.21 W m-2decade-1. Upward SSR trends were observed in seasons except winter. TCC, LCC and WVC have increased while, however, AOD and occurrences of severe dust storms have decreased, which indicates that it is dust aerosol rather than cloud cover and water vapor drive long-term upward trend of SSR in the TD. (Che Huizheng)

2.24 Study of aerosol optical properties based on ground measurements over Sichuan Basin, China

The characteristics of aerosol optical depth (AOD) and Ångström exponent as well as the relationship between the AOD and particulate matter (PM10), were measured and analyzed at the Chengdu station over the Sichuan Basin in China from February 2007 to December 2009. High monthly AODs were observed in March, August and December, while a low value was observed in October. Monthly variations in Ångström exponent were opposite to that of AODs in March and August. The averaged PM10showed a significantly seasonal variation with a peak in winter. There is a complicated (not linear) positive correlation between total AOD and near-surface PM10. Three typical cases under the conditions of dust and haze were studied, and the results show that the AODs on the dust days were largest while minimum AODs occurred on haze days. On the contrast, the Ångström exponent distributions among three weather conditions were opposite to that of AODs. The 3-day back-trajectory analysis indicates that the origin of the air masses largely affects the aerosol optical properties over the Sichuan Basin. (Che Huizheng)

2.25 Analysis of global distribution characteristics of cloud microphysical and optical properties based on the CloudSat data

The global distribution and seasonal variation of the cloud physical characteristics (including the cloud liquid and ice water content, liquid and ice water path, the effective radius, etc.) and cloud optical parameters (the cloud optical depth, etc.) were analyzed with the CloudSat 2B data from January 2007 to December 2010. The results show that the distribution of ice water paths is mainly over the North America, South America, Africa, Australia and the South Asia, as well as the Pacif c, Atlantic and Indian Ocean, with the highest values reaching 600 g m-2or more. In the vertical direction, the high values of ice water content are located near the height of 8 km over the equatorial regions and from 4 to 8 km over the middle latitude regions. The high values of liquid water paths are located over the Pacif c Ocean, the Indian Ocean and the mid and low latitudes of Atlantic. In the vertical direction, the value of liquid water content decreases with height. The ice effective radius reaches its maximum of over 200 μm near the surface at high latitudes, while having a maximum of over 80 μm at the height of 4–8 km in the equatorial region and at the height of 2–4 km in the mid-latitude. The liquid effective radius is large at the boundary layer under 1 km, with a value of over 12 μm. The total cloud optical depth is below 40 around the globe, with largest values located in the vast middle and high latitudes as well as over the oceans off the west coasts of low-latitude continents. Large cloud optical depths are concentrated below the boundary layer. The distribution of the cloud optical depth is closely linked to cloud amount, which is in good spatial accordance with the former, and also to cloud water content, and cloud effective radius. (Wang Zhili)

2.26 Validation of Aura Microwave Limb Sounder (MLS) water vapor and ozone prof les over the Tibetan Plateau and its adjacent region during boreal summer

We present validation studies of MLS V2.2 and V3.3 water vapor (WV) and ozone profiles over the Tibetan Plateau (Naqu and Lhasa) and its adjacent region (Tengchong) respectively by using the balloon-borne Cryogenic Frost point Hygrometer and Electrochemical Concentration Cell ozonesonde. Coincident in situ measurements were selected to compare the MLS V2.2 and V3.3 WV and ozone prof les for understanding the applicability of the two version MLS products over the region. MLS V2.2 and V3.3 WV prof les respectively show their differences within (2.2±15.7) % (n=74) and (0.3±14.9) % (n=75) in the stratosphere at and above 82.5 hPa. Accordingly, at 100 hPa, the altitude approaching the troposphere height, differences are within (9.8± 46.0) % (n=18) and (23.0±45.8) % (n=17), and they are within (21.5±90.6)% (n=104) and (6.0±83.4)% (n=99) in upper troposphere. The differences of MLS ozone are within (-11.7±16.3) % (n=135, V2.2) and (15.6±24.2) % (n=305, V3.3) at and above 82.5 hPa. At 100 hPa, they are within (-3.5±54.4) % (n=27) and (-8.7±41.6) % (n=38), and within (18.0±79.1) % (n=47) and (34.2±76.6) % (n=160) in the upper troposphere. The relative difference of MLS WV and ozone profile is significant in oscillation and scattering at upper troposphere and lower stratosphere partly due to the stronger gradients of WV and ozone concentrations here as well as the linear interpolation of sounding data for the inter-comparison. At and below 70 hPa, the relative differences of MLS ozone are signif cantly larger over Lhasa during the Tibetan Plateau “ozone valley” season, which is also the Asian summer monsoon period. The MLS ozone differences over the three sites are similar in their vertical distributions during that period. A simple linear correlation analysis between MLS and sounding prof les indicates that the sensitivity of MLS prof le products is related to concentrations at each pressure level. The MLS V3.3 product sensitivity is slightly improved for WV at and above 82.5 hPa, whereas it is not for ozone. The possible factors contributing to the differences of the MLS prof le products of WV and ozone are discussed. (Zheng Xiangdong)

3 Model development and implementation, the impacts of atmospheric compositions on climate, weather, and human health

3.1 Air quality forecasts and assessment of control measures during APEC

With the climate forecasting results and the CMA operational air quality (AQ) forecast model CUACE, the AQ trends and detailed forecasts were carried out. One month before the APEC, we provided the day to day variation trend for the APEC period to capture the main pollution episodes. Ten days before the APEC, high resolution forecasts were obtained for the proper Beijing and the APEC meeting venue in Huairou district. With the same CUACE model and observational results, the impacts of pollution reduction control measures were also assessed. It is shown that the control measures had reduced the PM2.5by 35% and NO2by 33% in Beijing City, contributing to the “APEC Blue”. It is found that the local contribution by Beijing City to the overall control impacts was 83%–89%, where the outside contribution was only 11%–17%, due to the weak southerly winds during the APEC period. Spatially, the most eff cient control measures were those taken within a circle of 300 km around Beijing and the contribution of vehicle control measures outside Beijing was not signif cant. The reduction at the point sources outside Beijing contributed about 9% of the reduced PM2.5in Beijing. (Gong Shanling, Liu Hongli)

3.2 Improvement of cloud microphysics in the aerosol-climate model BCC_AGCM2.0.1_CUACE/ Aero, evaluation against observations, and updated aerosol indirect effect

A two-moment cloud microphysical scheme, which predicts both the mass and number concentrations of cloud droplets and ice crystals, is implemented into the aerosol-climate model BCC_AGCM2.0.1_CUACE/ Aero. The model results for aerosols, cloud properties, and meteorological fields are evaluated, and the anthropogenic aerosol indirect effect (AIE) is estimated. The new model simulates more realistic aerosol mass concentrations and optical depth as compared with the former version using a one-moment bulk cloud microphysical scheme. The global annual mean column cloud droplet number concentration (CDNC) from the new model is 3.3×1010m-2, which is comparable to the 4.0×1010m-2from satellite retrieval. The global annual mean cloud droplet effective radius at the cloud top from the new model is 8.1 μm, which is smaller than the 10.5 μm from observation. The simulated liquid water path (LWP) in the new model is signif cantly lower than that in the former model. In particular, the annual mean LWP is lower in the new model by more than 100 g m-2in some mid latitude regions, hence more consistent with satellite retrievals. Cloud radiative forcing and precipitation are improved to some extent in the new model. The global annual mean radiation budget at the top of the atmosphere is -0.6 W m-2, which is considerably different from the value of 1.8 W m-2in the former model. The global annual mean anthropogenic AIE is estimated to be -1.9 W m-2without a lower bound of CDNC being imposed, whereas it is reduced signif cantly when a higher lower bound of CDNC is prescribed. (Wang Zhili)

3.3 Primary assessment of the simulated climatic state by a coupled aerosol-climate model BCC_ AGCM2.0.1_CAM

With the coupled model system of the second generation Global Circulation Model of the National Climate Center (BCC_AGCM2.0.1) and Canadian Aerosol Model (CAM), the simulation of five typical aerosols (sulfate, black carbon, organic carbon, soil dust, and sea salt) and possible effects on the modeled climate are discussed. The results show that in general, the coupled system simulates the five aerosols reasonably well, and there are obvious improvements in that for sulfate, dust, and sea salt aerosols compared to the original monthly mean aerosol data used in BCC_AGCM2.0.1. The climatic statistics simulated by the coupled system mainly agree well with observational/reanalyzed data, and are a little better than the monthly mean aerosol data in terms of the total cloud amount, land surface temperature, and precipitation. The enhanced representation of dust and sea salt improves the simulation of net solar radiation at the top of the atmosphere in the Sahara Desert and mid-latitude ocean in the Southern Hemisphere, which directly affects the land surface temperature. The cloud feedback above the tropical ocean caused by the change in an aerosol scheme not only alters radiation but also markedly inf uences precipitation. (Wang Zhili)

3.4 Effects of emission-sources reduction at different time points on PM2.5 concentration over Beijing

The Model-3 Community Multi-scale Air Quality (CMAQ) modeling system with a high resolution inventory data over Beijing-Tianjin-Hebei area was used to investigate the effects on PM2.5concentrations over Beijing of emission-sources reduction, the rates of which were the same but the 5 time points of which were different: 4 days, 3 days, 2 days, 1 day and 0 day in advance of the most polluted day. Simulations were made for a representative air pollution episode (Feb 7th–16th, 2012), in which Feb 13th was found to be the most polluted day. The results show that the PM2.5concentration was likely to decline more signif cantly if emissionsources reduction measures were taken before the most polluted day than were taken on the most polluted day. In addition, the earlier emission-sources reduction measures were taken, the more signif cantly the PM2.5concentration would decline. Reducing emission-sources 1 day, 2 days, 3 days ahead of the most polluted day led to the reduction of the peak value of PM2.5concentration at the Haidian station by 23%, 31%, and 39%, and in urban Beijing by 22%, 30%, and 38%, respectively. However, as the number of days ahead of the most polluted day (Feb 13th) to take reduction measures increased further, the additional decrease of the peak PM2.5concentration became smaller, thus the emission-sources reduction became less effective. The peak PM2.5concentration would decrease by 40% and 39% at Haidian station and urban Beijing if the reduction measures were taken 4 days before the most polluted day, which shows almost no improvement compared with those taken 3 days in advance. Similar results were obtained from simulations for another pollution episode (Jan 11th–20th, 2012). For controlling severe air pollution, both reduction costs and benef ts should be considered. Our study indicates that the most effective way of emission-sources reduction is to take reduction actions 2–3 days ahead of a possible severe pollution event, the timing of which can be obtained from meteorological condition prediction. In this way, a substantial decrease of the peak PM2.5concentration can be achieved with less cost for implementing the reduction measures. (An Xingqin)

3.5 Research on the application of the NASA/Goddard Long-Wave Radiative Scheme to the GRAPES_Meso model

The National Aeronautics and Space Administration (NASA)/Goddard Long-Wave Radiative Scheme is integrated into the Global/Regional Assimilation and Prediction System Mesoscale (GRAPES-Meso) model in this study. One month of simulation experiments conducted in China and its nearby areas are compared with the corresponding National Centers for Environmental Prediction (NCEP) reanalysis data recorded in April 2006. The results show that the distribution of the clear-sky outgoing long wave radiation f ux (OLRC) at the top of atmosphere and downward long wave radiation f ux at ground (GLWC) of 24-h and 48-h forecasts by using the GRAPES Meso model are in good agreement with the NCEP reanalysis data. The monthly average percentage error of the OLRC of these forecasts is within -10% and 10%. Although the monthly average percentage error of the GLWC is slightly larger than that of the OLRC, both are within a reasonable and acceptable range. The comparison study of the daily averaged anomaly correlation coeff cient and standard error of these f uxes of the two forecasts show that the monthly averaged anomaly correlation coeff cients of the OLRC and the GLWC of the 24-h forecast are 0.96 and 0.98 respectively, and that the monthly averaged standard errors are 24.54 W m-2and 27.23 W m-2respectively. Those of the OLRC and the GLWC of the 48-h forecast are 0.95 and 0.98 and 22.43 Wm-2and 27.64 W m-2respectively. Overall, the daily averaged anomaly correlation coeff cients of the OLRC and the GLWC of both 24-h and 48-h forecasts are above 0.93, and the daily standard error is within 31 W m-2. Moreover, the correlation of the GLWC and the NCEP reanalysis data is stronger than that of the OLRC, whereas the standard error of the OLRC and the NCEP reanalysis data is smaller than that of the GLWC. A comparison of the long wave radiative schemes of the rapid radiative transfer (RRTM) and the NASA/Goddard models reveals that the forecasting by the two schemes is essentially identical. The results of OLRC and the GLWC show that NASA/Goddard long wave radiative scheme may be appropriate for application to the GRAPES_Meso model. (Wang Hong)

3.6 Direct effect of tropospheric aerosols on stratospheric climate

Satellite data are used to be compared with WACCM-3 model results. It is found that model results have a very good consistency with satellite data in such areas: central Africa, the Arabian Peninsula, Indian subcontinent, and most of China; however, in southern central Africa, Caribbean, Europe and the Americas, the model results are low. In short, model results can well reproduce the global distribution of aerosols, and there still exist numerical differences in some areas.

Simulation tests indicate that the changes of stratospheric temperature are neither caused by changes of stratospheric short-wave radiation nor decided by the changes of long-wave radiation. It is not the main reason of the tropospheric aerosol effect on the stratospheric temperature, the changes of temperature are caused by dynamic processes, the change of the long wave radiative heating rate is in response to temperature changes. The stratospheric chemical, dynamic and radiation processes are tightly coupled together. The stratospheric chemical process is of vital importance to the effect of the tropospheric aerosols on stratospheric climate. The stratospheric chemical process has different effects in different seasons and different regions. Polar and highaltitude regions are considered to be mostly affected. In addition, the stratospheric chemical process also has a great inf uence to the upper stratosphere.

Planetary wave propagation changes make the stratospheric climate change: Stratospheric temperature, and wind f eld. Stratospheric ozone and radiation and dynamic processes are closely linked and inf uence each other. The temperature and wind changes then inf uence the concentration of ozone. Polar and high-altitude regions are considered to be mostly affected and impact on high southern altitude is greater than that on high northern altitude. The temperature variation could reach 10 K at most, while zonal wind variation could reach 12 m s-1and ozone mixing ratio could decline for 0.8×10-6at most at 20 hPa in the lower Antarctic stratosphere. In most other areas the temperature change does not exceed 1 K. (Liu Yu)

3.7 Study on impact of city emission and transport on greenhouse gases background observation at Shangdianzi station, Beijing

In-situ measurements of Carbon dioxide (CO2) and several halogenated greenhouse gases (HFC-134a, PFC-218 and HCFC-22) were chosen for case study. We did a statistical analysis and calculation of concentration anomalies and loadings from each wind direction, discussing impact of city emission and transport on greenhouse gases background observation at Shangdianzi station in different seasons. In the study period, the ratio of background concentration of CO2was about 21.2%. The difference between nonbackground concentration and background concentration was (3.7±1.3)×10-6due to local and city emission and transport. Anomalies and loadings of HFC-134a and PFC-218 ref ected differences in source characteristics of these two compounds. The seasonal trend of HCFC-22 was in consistency with the emission pattern of refrigerant. (Yao Bo)

3.8 Retrieve emission of SF6 in China using FLEXPART

SF6is one of long-lived halogenated greenhouse gases and listed as the restricted emission species in“Kyoto Protocol”. Along with the rapid economic development, SF6emission in China is increasing, which attracts attention in the world. For the traditional “bottom-up” method for SF6emission estimation, the required highly accurate and timely updated emission factors and activity data constitute a bottleneck. This paper presents the results on the estimation of SF6emissions in China for the year 2009 by using the Laprange particle dispersion model of FLEXPART and based on the in-situ measurement data obtained from the Shangdianzi regional atomspheric background station (SDZ). The preliminary estimations of SF6emissions in China for the year 2009 is 1.25×103(0.53×103–1.97×103) t, which is similar to the results reported by other studies in the literature. Compared to the a-priori emission, the retrieved emission boasts an improved correlation coefficient which increases from 0.37 to 0.43 and an improved root-mean-square (RMS) which decreases by 2.64 %. (An Xingqin)

3.9 Satellite observed aerosol effect on warm cloud properties under different meteorological conditions over eastern China

By taking meteorological conditions into account, this paper studies aerosol indirect effect on summertime warm clouds over the Yangtze River Delta (YRD) and East China Sea (ECS). The observed aerosol and cloud data are from MODIS/Aqua Level 2 datasets, and meteorological variables are from NCEP Final Analyses Operational Global Analysis datasets. To minimize meteorological effect on statistical analyses of aerosolwarm cloud interaction, several meteorological variables such as cloud top pressure (CTP), relative humidity (RH), pressure vertical velocity (PVV) and lower tropospheric stability (LTS) are considered in this study. Results show that cloud droplet radius (CDR) decreases with increasing aerosol optical depth (AOD) over ECS, while increases with increasing aerosol abundance over YRD. By taking CTP and RH into account, aerosol effects on cloud fraction (CF) are investigated. When aerosol loading is relatively small, CF is found to increase more sharply over YRD than over ECS in response to aerosol enhancement regardless of RH conditions. Therefore, we argue that the horizontal extension of cloud is prone to be driven by aerosol rather than meteorological conditions. Meanwhile, a joint correlative analysis of AOD-CF and AOD-CTP reveals that CTP effect on AOD-CF is not signif cant, indicating CTP makes little contribution to observed AOD-CF relationship. Constrained by lower LTS and pressure vertical velocity (750 hPa), CDR variation in response to AOD is analyzed. In general, CDR tends to decrease as aerosol increases over both ECS and YRD under stable conditions (higher LTS value). In contrast, CDR positively responds to aerosol over land under unstable conditions. Dynamically, CDR has stronger effects on the ascending motion than on the sinking motion with the same aerosol loading over both land and ocean. The reason can be partially explained by the phenomenon that updrafts favor the growth of cloud droplets. Overall, the observed cloud variations can be extremely diff cult to be attributed to aerosol particles alone due to dynamical and thermodynamical processes in cloud systems. (Guo Jianping)

3.10 Diurnal variation and inf uential factors of precipitation from surface and satellite measurements in Tibetan Plateau

Some new features concerning the diurnal variation of precipitation over the Tibetan Plateau (TP) are revealed from rainfall data acquired by a network of rain gauge stations and estimated by the Climate Precipitation Center Morphing (CMORPH) technique during the summer of 2010 and 2011. Maxima in precipitation amount and frequency are associated with the afternoon-to-evening precipitation regime as recorded at approximately 60% of the stations in the network. CMORPH data also capture this pattern, but miss the late morning peak that occurs at some stations. The timing of maximum occurrence agrees well with the diurnal cycle of synoptic conditions favoring the development of precipitation over this area. There is no distinct west-to-east propagation of the diurnal cycle, implying that the diurnal cycle is more driven by local effects than by large-scale circulation. It turns out that the diurnal cycle in precipitation frequency depends largely on topography and landscape. The geographical transition in precipitation peaking is distinct from hilly regions (daytime peak) towards lakes and valleys (evening-to-nocturnal peak). Stations located in mountainous regions (valleys) tend to experience more precipitation in either late morning or early afternoon (late afternoon or evening). Overall, precipitation amount shows a similar topographic dependence, as does the precipitation frequency, suggesting that local-scale effects, such as the mountain valley circulation effect, have a great impact on the diurnal variation in precipitation when large-scale dynamical processes are weak. A possible mechanism for the non-uniform diurnal cycle of precipitation over the TP is proposed. The major conclusion is that plateau-scale synoptic systems, as well as local circulation systems caused by the complex topography, should be taken into account when the diurnal variation in precipitation over the TP is determined. (Guo Jianping)

3.11 Precipitation and air pollution at mountain and plain stations in North China: Insights gained from observations and modeling

We analyzed 40-year datasets of daily average visibility (a proxy for surface aerosol concentration) and hourly precipitation at seven weather stations, including three stations located on the Taihang Mountains in North China during the summertime. There was no signif cant trend in summertime total precipitation at almost all stations. However, light rain decreased, whereas heavy rain increased as visibility decreased over the period studied. The decrease in light rain was seen in both orographic-forced shallow clouds and meso-scale stratiform clouds. The consistent trends in observed changes in visibility, precipitation, and orographic factor appear to be a testimony to the effects of aerosols. The potential impacts of large-scale environmental factors, such as precipitable water, convective available potential energy, and vertical wind shear, on precipitation were investigated. No direct link was found. To validate our observational hypothesis about aerosol effects, Weather Research and Forecasting (WRF) model simulations with spectral-bin microphysics at the cloud-resolving scale were conducted. Model results conf rmed the role of aerosol indirect effects in reducing the light rain amount and frequency in the mountainous area for both orographic-forced shallow clouds and meso-scale stratiform clouds and in eliciting a different response in the neighboring plains. The opposite response of light rain to the increase in pollution when there is no terrain included in the model suggests that orography is likely a signif cant factor contributing to the opposite trends in light rain seen in mountainous and plain areas. (Guo Jianping)

3.12 The transport and deposition of dust and its impact on phytoplankton growth in the Yellow Sea

Observed surface PM10mass concentrations and weather records, satellite-derived aerosol and ocean color data, dust simulations, and a backward trajectory analysis were used to investigate a severe dust storm episode during 19–22 March 2010 and its impact on phytoplankton growth in the Yellow Sea. The observed PM10concentrations and weather records show that heavy dust pollution occurred along the transport pathway. The high MODIS AOD regions were consistent with the simulated high dust emission and deposition ones. Based on the CALIPSO satellite observations, the high dust aerosol layer was below 2 km above ground, indicating the dust transported to the sea was centered within the lower layer. The model simulation estimated that the total deposition f ux over the southern Yellow Sea during 19–22 March 2010 was about 1.5 g m−2. Consequently, the chlorophyll a concentration was calculated to have increased four-fold. Ten to thirteen days later, a phytoplankton bloom occurred. The iron deposited by the severe dust episode could have increased the chlorophyll a concentration in the southern Yellow Sea by 10%–68%. Our results suggest that severe dust storms containing readily bioavailable nutrients may enhance phytoplankton growth in the southern Yellow Sea. (Wang Hong)

3.13 Wet deposition of acidifying substances in different regions of China and the rest of East Asia: Modeling with updated NAQPMS

The traditional way to study Sources-Receptor Relationships (SRRs) of wet deposition is based on sensitivity simulation, which has weakness in dealing with the non-linear secondary formation pollutants (e.g. ozone and nitrate). An on-line source tracking method has been developed in the Nested Air Quality Prediction Modeling System (NAQPMS) coupled with the cloud-process module for the f rst time. The new model can not only quantify the total volume of the sulfate, nitrate and ammonium wet deposition with more accuracy, but also trace these acidic species to their emitted precursors. Compared with previous studies, our result clearly shows: (1) East China and Central China, which are the two primary export regions, have 15%–30% and 10% effect on wet deposition in other areas, respectively; (2) Besides the above two regions, the total acid deposition in Southwest and Northeast China has reached or exceeded the critical loads under the environmental conditions of the two regions (Fig. 5). (Xu Xiaobin)

3.14 Combined effects of 1-nitropyrene and 1,2-naphthoquinone on cytotoxicity and DNA damage in A549 cells

With human lung epithelial A549 cells treated with 1-nitropyrene (1-NP), viability was measured by MTT assay; lactate dehydrogenase (LDH) leakage was determined to evaluate the cellular membrane injury; DNA damage was detected with comet assay; reactive oxygen species (ROS) generation was measured with f uorescent probe. The combined toxic effects of 1-NP and 1,2-naphthoquinone (1,2-NQ) on A549 were also evaluated. 1-NP caused a significantly concentration-dependent and time-dependent viability decrease. The LC50for 24 h and 48 h were 5.2 μmol L-1and 2.8 μmol L-1, respectively. DNA damage and intracellular ROS levels were also increased signif cantly through a dose-dependent manner after exposure to 1-NP. The LDH leakage was not signif cantly changed. Compared with the groups treated with 1-NP alone, the viability and LDH leakage were not changed signif cantly in combined-treated groups with 1-NP and 1,2-NQ. However, the DNA damage and ROS levels were signif cantly reduced in the combined-treated groups compared with the groups treated with 1-NP alone. These results suggest that 1-NP may mediate the genotoxic and cytotoxic effects through ROS generation and pretreatment with 1,2-NQ, and may inhibit the ROS generation induced by 1-NP, thereby reducing the DNA damage in A549 cells. (Li Yi)

3.15 Airborne quinones induce cytotoxicity and DNA damage in human lung epithelial A549 cells: The role of reactive oxygen species

Ambient particulate matter (PM) is associated with adverse health effects. Quinones present in PM are hypothesized to contribute to these harmful effects through the generation of reactive oxygen species (ROS). However, whether the ROS induced by quinones is involved in mediating DNA damage as well as other biological responses in pulmonary cells is less well known. In this study, the toxic effects of fve typical airborne quinones, including 1,2-naphthoquinone, 2-methylanthraquinone, 9,10-phenanthrene-quinone, 2-methyl-1,4-naphthoquinone, and acenaphthenequinone, on cytotoxicity, DNA damage, intra-cellular

calcium homeostasis, and ROSgeneration, were studied in human lung epithelial A549 cells. Anantioxidant N-acetylcysteine (NAC) was used to examine the involvement of ROS in adverse biological responses induced by quinones. The quinones caused a concentration-dependent viability decrease, cellular LDH release, DNA damage, and ROS production in A549 cells. 1,2-Naphthoquinone, but not the other four quinones, increased intracellular calcium (Ca2+) levels in a dose-dependent manner. These toxic effects were abolished by administration of NAC, suggesting that ROS played a key role in the observed toxic effects of quinones in A549 cells. These results emphasize the importance of quinones in PM on the adverse health effects of PMs, which has been underestimated in the past few years, and highlight the need, when the effects on health and exposure management are evaluated, to always consider their qualitative chemical compositions in addition to the size and concentration of PMs. (Li Yi)