吴思寒,吴雨濛,王双杰,陈 萌,刘 青,祝凌燕

全氟辛烷磺酰胺在小麦和蚯蚓中的富集与转化

吴思寒,吴雨濛,王双杰,陈 萌,刘 青,祝凌燕*

(南开大学环境科学与工程学院,环境污染过程与基准教育部重点实验室,天津城市生态环境修复与污染防治重点实验室,天津 300350)

研究了不同培养介质和培养方式下全氟辛烷磺酰胺(PFOSA)在小麦、蚯蚓体内的生物富集和转化.结果表明:小麦根系可以从培养介质中吸收PFOSA并向上转运至茎叶.土壤中PFOSA生物有效性受总有机碳(TOC)的影响显著,高TOC含量土壤中PFOSA的生物有效性降低,导致其在小麦和蚯蚓中的生物富集因子分别由(61.24±8.42)和(21347.91±208.86)降至(5.61±0.23)和(1404.92±108.21).PFOSA在小麦的根和茎叶以及蚯蚓中都可以转化为PFOS,但在蚯蚓中的转化率((3.87±1.71)%)显著低于小麦((26.39±3.02)%).小麦根中PFOS的支链异构体(-PFOS)比例在低、高TOC含量时分别为(14.8±2.0)%、(66.1±26.2)%,低于茎叶(分别为(63.0±21.3)%、(85.2±2.4)%)),可能是由于根部转化生成的-PFOS更容易向茎叶转运.小麦特别是小麦茎叶中的-PFOS比例((85.2±2.4)%)显著高于蚯蚓((16.5±4.0)%).小麦的存在可以提高土壤中PFOSA的生物有效性,从而促进蚯蚓对PFOSA的富集,但对其转化影响不大.本文为小麦和蚯蚓中PFOSA的富集和转化提供了证据,有助于探索环境中PFOS的间接来源.

全氟辛烷磺酰胺(PFOSA)；小麦；蚯蚓；生物富集；生物转化

全氟和多氟化合物(PFASs)因其优异性质已在日常生活中被广泛使用,如食品包装材料、消防泡沫、表面活性剂、纺织品等[1].PFASs结构中的C-F键是最强的共价单键,因此PFASs极为稳定,难以发生生物和非生物降解(如水解、光解),可在环境中长期存在,并发生生物富集、生物放大效应[2-3].全氟辛烷磺酸(PFOS)是研究最多、环境中最常见的一种PFASs[4],已在环境介质和人体中[5-10]广泛检出,并对生殖、免疫、内分泌和神经系统以及肝脏均具有毒害作用[11-12],因此于2009年列入斯德哥尔摩公约,被逐步禁用[13].除直接排放外,环境中PFOS的另一主要来源是环境中前体物(PreFOS)的转化[14].据报道,1970～2002年间,PreFOS的最大历史排放量(6800 ～45250t)要远高于PFOS(450～2700t)[15].全氟辛烷磺酰胺(PFOSA)是一种在环境中广泛检出的典型PreFOS[16-19].它是许多其他大分子PreFOS转化为PFOS的中间物质,且是限速步骤[20-26].工业生产的PFOSA中,支链异构体(-PFOSA)比例为24.7%[27]. PFOSA的转化存在异构体选择性,其异构体转化特征会对环境中PFOS的异构体分布特征产生影响,有助于追溯环境中PFOS的来源[28].但目前关于PFOSA在陆生动植物中的特异性转化研究较少,因此对其进行研究十分必要.

土壤是PFASs在环境中的重要归属地之一[6], PFASs能通过点源污染、大气沉降、地面径流等进入土壤系统[29].例如,在美国空军设施附近的土壤中PFOSA最高浓度甚至已达到20000ng/g[6].土壤中PFASs可以通过植物或动物进入食物链,经食物链的富集产生生物放大效应,对人体健康产生危害.小麦(L.)是一种世界各地都广泛种植的禾本科农作物,是人类食物的重要来源之一[12].蚯蚓()是土壤中生物量最大的无脊椎动物,其生命活动会直接或间接地对有机污染物在土壤中的迁移和转化产生影响[30].土壤的性质、生物种类等都会影响PFOSA的生物富集和生物转化,因此本文以小麦、蚯蚓为受试生物,PFOSA为目标污染物,研究不同培养介质和培养方式下PFOSA在小麦、蚯蚓体内的生物富集和转化,为探索环境中PFOS的间接来源、评价PFOSA的人类健康和生态风险以及环境修复提供理论参考.

1 材料与方法

1.1 实验材料

实验所用试剂如下:全氟辛烷磺酰胺工业品(PFOSA,>90%,北京百灵威科技有限公司),全氟辛烷磺酸标准品及其内标(PFOS和13C-PFOS,>99%)、全氟辛烷磺酰胺标准品及其内标(PFOSA和13C- PFOSA, >99%)购自加拿大惠灵顿实验室.甲醇(色谱纯)、过氧化氢30%(H2O2,质量分数,分析纯)均购自天津市化学试剂供销公司,甲基叔丁基醚(分析纯,天津市康科德科技有限公司),氢氧化钠(NaOH,优级纯)、四丁基硫酸氢铵(TBAHS,分析纯)、无水碳酸钠(Na2CO3,优级纯)均购自天津市津科精细化工研究所.甲酸(色谱纯,上海安谱实验科技股份有限公司)、氨水(色谱纯,阿拉丁)、甲醇(HPLC级)和乙腈(HPLC级)购自美国Fisher公司.

实验所用小麦种子(L.)购自天津农科院,所用赤子爱胜蚓()购于天津当地养殖场.

1.2 暴露实验

1.2.1 小麦在土壤和石英砂介质中的暴露实验 首先将小麦种子于3% H2O2(质量分数)中浸泡30min消毒,用Milli-Q水冲洗5次后,用Milli-Q水浸泡一夜,之后在铺有湿滤纸的底部未全封闭的透气托盘架上均匀铺开,使之于22～27℃下发芽,托盘架上部铺一层铝箔以保证含水率,防止水分蒸发过快.为了研究土壤中TOC对PFOSA生物有效性的影响,实验采用2种培养介质种植小麦,分别为土壤和石英砂,设立4组实验:有毒有植物、无毒有植物、有毒无植物和无毒无植物,染毒浓度为200ng/g,每组设置3个平行.将发芽3d、大小均一的小麦幼苗移植到1L塑料花盆中,每盆装有650g培养介质,种植7株小麦.将花盆放置于采光较好的天台处培养,每天随机更换盆的位置以保证小麦受阳光照射条件良好,每天浇水使土壤含水率保持在30%左右,14d后收获小麦.收获时用蒸馏水冲洗小麦根部,之后用滤纸擦干,将小麦根和茎叶分离,弃去根茎连接处,于-20℃冰箱中储存.

1.2.2 蚯蚓在不同TOC含量土壤中的暴露实验 将蚯蚓于未染毒土壤中避光驯养14d.实验采用土壤和土壤/石英砂(8:2,质量比)两种培养介质,染毒浓度为0, 200ng/g,设置3个平行.将驯养好的蚯蚓放入250mL烧杯,每杯装有100g培养介质,放入10条蚯蚓.将烧杯用铝箔包裹,避光培养,每天加水保持土壤湿度在30%左右,分别培养7和14d后收获蚯蚓.收获时从土壤中取出蚯蚓并用水清洗,在装有潮湿脱脂棉的玻璃杯中放置24h清肠后用水冲洗,再用滤纸吸去水分,于-20℃冰箱中储存.

1.2.3 蚯蚓-小麦联合暴露实验 小麦种子的培育见1.2.1,蚯蚓驯养见1.2.2.将赤子爱胜蚓与小麦联合培养,采用土壤和土壤/石英砂(8:2)两种培养介质,染毒浓度为0, 200ng/g,设置3个平行.将发芽3d的小麦和驯养完成的蚯蚓放入1L塑料花盆中,每盆装有650g培养介质,加入7株小麦和10条蚯蚓.用铝箔包裹花盆边缘并高出边缘3cm,以防蚯蚓在实验期间爬出.每天加水保持土壤湿度在30%左右,14d后收获小麦和蚯蚓.小麦和蚯蚓的取样方式同1.2.1和1.2.2.

1.3 样品前处理

生物样前处理采用Chen等[31]的方法并稍作改进.将生物样置于冷冻干燥机中-50℃下干燥48h,剪碎.称取一定质量干重样品(根取0.01g,茎叶取0.05g,蚯蚓取0.1g)于10mL PP 离心管中,加入2ng内标(包括M4-PFOS和M8-PFOSA),涡旋振荡,使其充分混匀,平衡至少2h.依次加入1mL 0.5mol/L的TBAHS 溶液(pH值用氢氧化钠溶液调至10)和2mL 0.25mol/L的Na2CO3缓冲液,充分混匀后,加入4mL甲基叔丁基醚,混合液于250r/min下震荡20min,然后在4℃、6000r/min下离心10min使有机相与水相分离,将上层有机相转移至新10mL离心管中.萃取过程重复2次,萃取液氮吹至干.用2mL甲醇复溶,加入50mg Carb填料以去除色素等杂质,混匀后在4℃,11000r/min下离心15min.取上清液至新离心管中氮吹干.用1mL甲醇复溶,过0.22μm尼龙滤膜后转移到进样小瓶中,放在冻存盒中于-20℃冰箱中保存,以待分析.

培养介质前处理采用Zhao等[30]的方法并稍作改进.将培养介质置于冷冻干燥机中-50℃下干燥48h,将1g干燥的介质置于10mL PP离心管中,加入2ng内标(包括M4-PFOS和M8-PFOSA),涡旋振荡,使其充分混匀,平衡至少2h.加入5mL甲醇,然后于250r/min下震荡10min.将离心管于40℃超声10min.将该混合物在3000r/min下离心10min.重复提取3遍,并将上清液合并到另一个新的离心管中.萃取液氮吹至2mL.加入50mg Carb填料以去除色素等杂质,混匀后在4℃,11000r/min下离心15min.取上清液至新离心管中氮吹干.用1mL甲醇复溶,过0.22μm尼龙滤膜后转移到进样小瓶中,放在冻存盒中于-20℃冰箱中保存,以待分析.

1.4 仪器分析

在负电喷雾电离模式下,使用Waters超高效液相色谱-质谱联用仪(ACQUITY-UPLC/XEVO-TQS)分析样品中各物质含量.色谱柱采用FluoroSep-RP Octyl柱(150mm´2.1mm,3μm粒径; ES Industries, West Berlin,NJ).柱温为38℃,进样体积为10μL,流动相流速为0.15mL/min.对于PFOSA异构体,流动相A、B分别为3mmol/L甲酸的水溶液(pH值用氨水调至4.15)和乙腈溶液.流动相初始比例为60%A、40%B,保持1min,在3min变为74%B,在35min变为80%B,在35.1min变为100%B并保持至40min,在45min回到初始比例.对于PFOS异构体,流动相A、B分别为3mmol/L甲酸的水溶液(pH值用氨水调至4.15)和甲醇溶液.流动相初始比例为60%A、40%B,保持0.3min,在1.9min变为64%B,在5.9min变为66%B,在7.9min变为70%B,在26min变为74%B,在30min变为100%B并保持至33min,在35min回到初始比例并保持至40min.质谱条件为:毛细管电压2700V;离子源温度150℃;去溶剂温度350℃;锥孔气流速150L/Hr;去溶剂气流速800L/Hr;雾化气流速7bar.目标化合物的定量离子、锥孔电压及碰撞能参数如表1所示.

表1 目标化合物的定量离子、锥孔电压、碰撞能

注:a3-和5-PFOS异构体无法进行基线分离,因此被合并为3+5-PFOS.

1.5 质量保证与质量控制

回收率实验通过向空白基质中加入标准品进行.在样品前处理过程中添加过程空白以校正背景污染.根据样品峰面积与内标峰面积之比对物质浓度进行定量.方法检出限(MDL)定义为信噪比为3:1时物质浓度.各物质的回收率和检出限如表2所示.本实验中,各基质中PFOSA和PFOS的回收率均在80%～100%范围内,因此不使用回收率对测得的各物质浓度进行校正.

在暴露实验开始前,小麦中就检测到一定浓度的PFOSA(根(11.71±0.93) ng/g,茎叶(2.64±0.44) ng/g)和PFOS(根(16.89±4.25) ng/g,茎叶(4.20±2.56) ng/g).在暴露14d后,空白小麦中检测到相似水平的PFOSA(根(9.53±1.74)～(10.38±1.60) ng/g,茎叶(2.56±0.59)～(3.34±1.64) ng/g )和PFOS(根(15.31±1.31)～(16.24±1.96) ng/g,茎叶(1.64±0.54)～(1.71±0.47) ng/g).空白蚯蚓体内PFOSA和PFOS的浓度远低于实验组蚯蚓(相差103～105个数量级).由此判断,空白组小麦和蚯蚓中PFOSA和PFOS来源于背景污染.本文所用暴露组浓度均扣除了空白组浓度.

表2 目标化合物的回收率和方法检出限(MDL)

1.6 数据分析

对小麦的根富集因子(RCF)、蚯蚓的生物富集因子(BSAF)和转化率(TR)进行计算,公式如下:

式中:m为培养介质中PFOSA的浓度, ng/g;root为小麦根中PFOSA浓度, ng/g dw;e为蚯蚓中PFOSA浓度, ng/g dw;PFOS为小麦或蚯蚓中PFOS浓度, ng/g dw;PFOSA为小麦或蚯蚓中PFOSA浓度, ng/g dw.

使用IBM SPSS Statistics 22进行数据分析.使用配对检验评估各组间RCF、TR和-PFOS比例的差异,当< 0.05时认为存在显著性差异,当< 0.01时认为差异极显著.

2 结果与讨论

2.1 小麦和蚯蚓的生理状况

在整个实验周期内,小麦和蚯蚓生理状况良好,没有不良反应、死亡等现象,空白对照组和实验组小麦和蚯蚓生物量无显著性差异(> 0.05).

2.2 小麦对PFOSA的富集和转化

通过公式(1)计算小麦的RCF,发现PFOSA在石英砂培养小麦中的RCF((61.24±8.42))远大于土壤中培养的小麦((5.61±0.23)),存在显著性差异(<0.01),说明培养基质中的总有机碳含量(TOC)会显著影响其生物有效性.Liu等[32]研究表明土壤TOC含量与所吸附的PFOS量之间存在显著的线性关系(< 0.01).土壤中TOC含量高于石英砂,对PFOSA具有较强的吸附能力,使得土壤中可生物利用的PFOSA减少,导致在土壤中生长的小麦的RCF较低.

在小麦的根和茎叶中均测得转化产物PFOS.通过公式(3)计算了小麦中PFOSA的转化率,发现茎叶中转化率远高于根中(<0.01,图1).有实验表明,当辛醇-水分配系数(logow)>4时,疏水性有机化合物会强烈吸附于根的上表皮,难以转运到茎叶[33].Zhao等[34]研究也表明当有机化合物logow>4时,该物质从根到茎叶转运因子(TF)随logow的增加而指数递减.PFOSA的logow(5.62)小于PFOS(logow= 6.43)[35],表明PFOS较PFOSA更难从根转运至茎叶,因此茎叶中较高的转化率表明叶中PFOS不仅来源于根部转运,还来源于茎叶的生物转化.此外还发现PFOSA在土壤培养的小麦根(<0.05)和茎叶(< 0.01)的转化率均大于石英砂中小麦(图1).这可能是由于PFOSA被土壤中微生物转化为PFOS[36],生成的PFOS被小麦富集.土壤中有机碳可以为微生物的生长提供充足的碳源,从而提高微生物数量和活性[37].Bizkarguenaga等[38]也观察到在高TOC的土壤中生菜对PFOSA降解更强.

图1 生长在不同培养基质中的小麦对PFOSA的转化率

**、*分别表示差异极显著(<0.01)和显著(<0.05)

除石英砂培养的小麦根外((14.8±2.0)%),小麦中-PFOS比例均显著高于24.7%(土壤中小麦根:(66.1±26.2)%,土壤中小麦叶:(85.2±2.4)%,石英砂中小麦叶:(63.0±21.3)%,图2),说明小麦中-PFOSA比-PFOSA优先发生转化.小麦中-PFOS比例呈现以下趋势:根中-PFOS比例小于茎叶,石英砂培养的小麦中-PFOS比例小于土壤.小麦根中- PFOS比例要小于茎叶,这是因为直链异构体比相应的支链异构体具有更高的疏水性[18],导致-PFOS比-PFOS更易从根转运至茎叶.石英砂介质培养的小麦根中-PFOS比例低于24.7%,可能也是由于根中生成的-PFOS部分转运至茎叶.已有研究表明,PFOSA是N-EtFOSE生物转化过程的中间产物[21,39].Liu等[25]在好氧土壤中观察到N-EtFOSE的异构体特异性生物转化并检测到-PFOS的生成.Chen等[31]表明,-PFOSA在生物体内会优先转化为-PFOS.因此可以推测,土壤中微生物对-PFOSA进行优先转化,生成更多的-PFOS并被小麦吸收,从而导致土壤中培养的小麦中-PFOS比例高于石英砂中培养的小麦.

图2 小麦根和茎叶中br-PFOS比例

2.3 蚯蚓对PFOSA的富集和转化

通过计算蚯蚓对PFOSA的生物富集因子(BSAF),发现随培养时间增加,PFOSA在蚯蚓体内的BSAF增加(图3).培养14d后,土壤/石英砂(8:2)介质中PFOSA在蚯蚓体内的BSAF值(21347.91±208.86)远高于土壤中(1404.92±108.21),是土壤中的15.20倍(图3),该趋势与PFOSA在小麦体内富集的结果相同,进一步说明土壤中TOC对PFOSA具有较强的吸附能力,降低了土壤中PFOSA的生物有效性.

图3 不同培养时间和培养介质下蚯蚓中PFOSA的BSAF

在蚯蚓中同样检测到PFOSA转化产物PFOS的生成,但其TR相对较低.在土壤中培养了14d的蚯蚓中PFOSA的TR((3.87±1.71)%)显著低于小麦中((26.39±3.02)%),表明不同生物对PFOSA的转化能力存在很大差异[40].

图4 不同培养时间和培养介质下蚯蚓中br-PFOS比例

不同培养介质对蚯蚓中-PFOS比例会产生影响,土壤/石英砂(8:2)介质中,-PFOS比例更高(图4,<0.05).这可能是由于土壤/石英砂(8:2)介质加入了石英砂,土壤黏性降低,孔隙度高,通气透水性强,更适宜蚯蚓生存,其中蚯蚓的活性更高.在生物体内-PFOSA异构体会优先代谢[31,41],生成-PFOS.土壤/石英砂(8:2)介质仅加入20%的石英砂,TOC含量与土壤差距不大,所以推测其微生物数量和活性差异较小,对PFOSA转化的影响也差别不大.因此土壤/石英砂(8:2)介质中蚯蚓体内-PFOS比例高.与小麦特别是茎叶中较高的-PFOS比例不同,在土壤中培养了14d的蚯蚓中-PFOS比例为(16.5±4.0)%,小于24.7%.这可能是由于蚯蚓通过大量排出粪便向外排出污染,而-PFOS比-PFOS更易从体内排出[31].

2.4 小麦共同生长对蚯蚓中PFOSA的富集和转化的影响

蚯蚓和小麦联合培养时,土壤/石英砂(8:2)介质中PFOSA在蚯蚓体内的BSAF(32176.65±844.49)高于土壤中(26743.14±11311.21)(图5),进一步说明土壤TOC会显著影响其中PFOSA的生物有效性.由图5可知,联合培养时PFOSA在蚯蚓体内的BSAF显著高于蚯蚓单独培养时的结果(<0.05).Kelsey等[42]、Zhao等[34]也发现南瓜和小麦会促进蚯蚓对p,p'-DDE和PFASs的富集.这主要是由于植物根系分泌物会提高PFOSA从土壤中的解吸,提高其生物有效性.小麦存在时,蚯蚓中PFOSA转化率与单独培养时无显著性差异(>0.05),表明小麦的存在对蚯蚓中PFOSA转化率无影响.

图5 不同培养方式和培养介质下蚯蚓中PFOSA的BSAF

E:蚯蚓单独培养; E+W:蚯蚓和小麦联合培养

3 结论

3.1 小麦根能从土壤溶液中吸收PFOSA并转运至茎叶.土壤TOC含量显著影响其中PFOSA的生物有效性,TOC含量高,其生物有效性降低.PFOSA在小麦的根和茎叶中都可以转化为PFOS,且土壤培养的小麦中PFOSA的转化率更高.小麦中-PFOS比例关系为根<茎叶,石英砂<土壤.

3.2 蚯蚓能有效从土壤中富集PFOSA并将其转化为PFOS.土壤/石英砂(8:2)介质培养的蚯蚓-PFOS比例更高.蚯蚓中PFOSA转化率和-PFOS比例均低于小麦.

3.3 小麦提高了蚯蚓对PFOSA的富集,但对蚯蚓中PFOSA转化率影响不大.

[1] Buck R C, Franklin J, Urs B, et al. Perfluoroalkyl and polyfluoroalkyl substances in the environment: terminology, classification, and origins [J]. Integrated environmental assessment and management, 2011,7(4): 513-541.

[2] Loi E I H, Yeung L W Y, Taniyasu S, et al. Trophic magnification of poly- and perfluorinated compounds in a subtropical food web [J]. Environmental Science & Technology, 2011,45(13):5506-5513.

[3] Powley C R, George S W, Russell M H, et al. Polyfluorinated chemicals in a spatially and temporally integrated food web in the Western Arctic [J]. Chemosphere, 2008,70(4):664-672.

[4] Mudumbi J B N, Ntwampe S K O, Matsha T, et al. Recent developments in polyfluoroalkyl compounds research: a focus on human/environmental health impact, suggested substitutes and removal strategies [J]. Environmental Monitoring and Assessment, 2017,189(8),402.doi:10.1007/s10661-017-6084-2.

[5] Li Y, Feng X M, Zhou J, et al. Occurrence and source apportionment of novel and legacy poly/perfluoroalkyl substances in Hai River basin in China using receptor models and isomeric fingerprints [J]. Water Research, 2020,168,115145.doi:10.1016/j.watres.2019.115145.

[6] Brusseau M L, Anderson R H, Guo B. PFAS concentrations in soils: Background levels versus contaminated sites [J]. Science of the Total Environment, 2020,740,140017.doi:10.1016/j.scitotenv.2020.140017.

[7] Sun J C, Bossi R, Bustnes J O, et al. White-tailed eagle (Haliaeetus albicilla) body feathers document spatiotemporal trends of perfluoroalkyl substances in the Northern environment [J]. Environmental Science & Technology, 2019,53(21):12744-12753.

[8] Goodrow S M, Ruppel B, Lippincott R L, et al. Investigation of levels of perfluoroalkyl substances in surface water, sediment and fish tissue in New Jersey, USA [J]. Science of the Total Environment, 2020,729, 138839.doi:10.1016/j.scitotenv.2020.138839.

[9] Oliveira S M C, Pereira S M C, Masato H, et al. Exposure to per- and polyfluorinated alkyl substances in pregnant Brazilian women and its association with fetal growth [J]. Environmental research, 2020, 187,109585.doi:10.1016/j.envres.2020.109585.

[10] 郭萌萌,崔文杰,刘晓玉,等.黄渤海区域水产品中全氟烷基物质的分布特征 [J]. 中国环境科学, 2020,40(8):3424-3432. Guo M M, Cui W J, Liu X Y, et al. Distribution of perfluoroalkyl substances in aquatic products in coastal and adjacent areas of the Yellow Sea and Bohai Sea, China [J]. China Environmental Science, 2020,40(8):3424-3432.

[11] Lau C, Anitole K, Hodes C, et al. Perfluoroalkyl acids: A review of monitoring and toxicological findings [J]. Toxicological Sciences, 2007,99(2):366-394.

[12] 关 月.小麦对全氟化合物的吸收研究 [D]. 大连:大连理工大学, 2012. Guan Y. Uptake of perfluorinated compounds (PFCs) by wheat (Triticum aestivum L.) [D]. Dalian: Dalian Universtity of Technology, 2012.

[13] UNEP. The 9new POPs: An introduction to the nine chemicals added to the Stockholm Convention by the Conference of the Parties at its fourth meeting [EB/OL]. http://chm.pops.int/Programmes/NewPOPs/ Publications/tabid/695/language/en-US/Default.aspx, 2010-08/2020- 09-11.

[14] 周绍宏,王淦淦,张利兰.环境中全氟辛基磺酸前体物好氧生物降解进展 [J]. 中国环境科学, 2019,39(9):3967-3975. Zhou S H, Wang G G, Zhang L L. Aerobic biodegradation of perfluorooctane sulfonateprecursors in different environment media [J]. China Environmental Science, 2019,39(9):3967-3975.

[15] Paul A G, Jones K C, Sweetman A J. A first global production, emission, and environmental inventory for perfluorooctane sulfonate [J]. Environmental Science & Technology, 2009,43(2):386-392.

[16] Chen M, Wang Q, Shan G Q, et al. Occurrence, partitioning and bioaccumulation of emerging and legacy per- and polyfluoroalkyl substances in Taihu Lake, China [J]. Science of the Total Environment, 2018,634:251-259.

[17] Houtz E F, Higgins C P, Field J A, et al. Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil [J]. Environmental Science & Technology, 2013,47(15):8187-8195.

[18] Fang S H, Chen X W, Zhao S Y, et al. Trophic magnification and isomer fractionation of perfluoroalkyl substances in the food web of Taihu Lake, China [J]. Environmental Science & Technology, 2014, 48(4):2173-2182.

[19] Stubleski J, Salihovic S, Lind L, et al. Changes in serum levels of perfluoroalkyl substances during a 10-year follow-up period in a large population-based cohort [J]. Environment International, 2016,95: 86-92.

[20] Zhao S Y, Wang B H, Zhu L Y, et al. Uptake, elimination and biotransformation of N-ethyl perfluorooctane sulfonamide (N- EtFOSA) by the earthworms (Eisenia fetida) after in vivo and in vitro exposure [J]. Environmental Pollution, 2018,241:19-25.

[21] Zhao S Y, Liu T Q, Wang B H, et al. Accumulation, biodegradation and toxicological effects of N-ethyl perfluorooctane sulfonamidoethanol on the earthworms Eisenia fetida exposed to quartz sands [J]. Ecotoxicology and Environmental Safety, 2019,181:138-145.

[22] Peng H, Zhang S Y, Sun J X, et al. Isomer-specific accumulation of perfluorooctanesulfonate from (N-Ethyl perfluorooctanesulfonamido) ethanol-based phosphate diester in Japanese Medaka (Oryzias latipes) [J]. Environmental Science & Technology, 2014,48(2):1058-1066.

[23] Fu Z Q, Wang Y, Wang Z Y, et al. Transformation pathways of isomeric perfluorooctanesulfonate precursors catalyzed by the active species of P450enzymes: In silico investigation [J]. Chemical Research in Toxicology, 2015,28(3):482-489.

[24] Benskin J P, Holt A, Martin J W. Isomer-specific biotransformation rates of a perfluorooctane sulfonate (PFOS)-precursor by cytochrome P450isozymes and human liver microsomes [J]. Environmental Science & Technology, 2009,43(22):8566-8572.

[25] Liu J X, Zhong G W, Li W, et al. Isomer-specific biotransformation of perfluoroalkyl sulfonamide compounds in aerobic soil [J]. Science of the Total Environment, 2019,651:766-774.

[26] Zhao S Y, Zhou T, Zhu L Y, et al. Uptake, translocation and biotransformation of N-ethyl perfluorooctanesulfonamide (N- EtFOSA) by hydroponically grown plants [J]. Environmental Pollution, 2018,235:404-410.

[27] Shan G Q, Yang L P, Zhao J Y, et al. Identification and quantification of perfluorooctane sulfonamide isomers by liquid chromatography- tandem mass spectrometry [J]. Journal of Chromatography A, 2019, 1594:65-71.

[28] Benskin J P, De Silva A O, Martin J W. Isomer profiling of perfluorinated substances as a tool for source tracking: A review of early findings and future applications [J]. Reviews of Environmental Contamination and Toxicology, 2010,208:111-160.

[29] 李法松,倪 卉,黄涵宇,等.安徽省部分城市土壤中全氟化合物空间分布及来源解析 [J]. 环境科学, 2017,38(1):327-332. Li F S, Ni H, Huang H Y, et al. Spatial distribution and source of perfluorinated compounds in urban soil from part of cities in Anhui Province, China [J]. Environmental Science, 2017,38(1):327-332.

[30] Zhao S Y, Wang B H, Zhong Z, et al. Contributions of enzymes and gut microbes to biotransformation of perfluorooctane sulfonamide in earthworms (Eisenia fetida) [J]. Chemosphere, 2020,238,124619. doi:10.1016/j.chemosphere.2019.124619.

[31] Chen M, Qiang L W, Pan X Y, et al. In vivo and in vitro isomer-specific biotransformation of perfluorooctane sulfonamide in common carp (Cyprinus carpio) [J]. Environmental Science & Technology, 2015,49(23):13817-13824.

[32] Liu Y, Qi F, Fang C, et al. The effects of soil properties and co-contaminants on sorption of perfluorooctane sulfonate (PFOS) in contrasting soils [J]. Environmental Technology & Innovation, 2020,19,100965.doi:10.1016/j.eti.2020.100965.

[33] Collins C, Fryer M, Grosso A. Plant uptake of non-ionic organic chemicals [J]. Environmental Science & Technology, 2006,40(1): 45-52.

[34] Zhao S Y, Fang S H, Zhu L Y, et al. Mutual impacts of wheat (Triticum aestivum L.) and earthworms (Eisenia fetida) on the bioavailability of perfluoroalkyl substances (PFASs) in soil [J]. Environmental Pollution, 2014,184:495-501.

[35] Wang Z Y, Macleod M, Cousins I T, et al. Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs) [J]. Environmental Chemistry, 2011,8(4):389-398.

[36] Hao J, Wang P H, Kang Y F, et al. Degradation of perfluorooctane sulfonamide by acinetobacter Sp. M and its extracellular enzymes [J]. Chemistry-an Asian Journal, 2019,14(16):2780-2784.

[37] Perez-Bejarano A, Mataix-Solera J, Zornoza R, et al. Influence of plant species on physical, chemical and biological soil properties in a Mediterranean forest soil [J]. European Journal of Forest Research, 2010,129(1):15-24.

[38] Bizkarguenaga E, Zabaleta I, Mijangos L, et al. Uptake of perfluorooctanoic acid, perfluorooctane sulfonate and perfluorooctane sulfonamide by carrot and lettuce from compost amended soil [J]. Science of the Total Environment, 2016,571:444-451.

[39] Avendano S M, Liu J X. Production of PFOS from aerobic soil biotransformation of two perfluoroalkyl sulfonamide derivatives [J]. Chemosphere, 2015,119:1084-1090.

[40] Zhao S Y, Zhu L Y. Uptake and metabolism of 10:2 fluorotelomer alcohol in soil-earthworm (Eisenia fetida) and soil-wheat (Triticum aestivum L.) systems [J]. Environmental Pollution, 2017,220:124-131.

[41] Ross M S, Wong C S, Martin J W. Isomer-specific biotransformation of perfluorooctane sulfonamide in Sprague-Dawley rats [J]. Environmental Science & Technology, 2012,46(6):3196-3203.

[42] Kelsey J W, Slizovskiy I B, Petriello M C, et al. Influence of plant-earthworm interactions on SOM chemistry and p,p '-DDE bioaccumulation [J]. Chemosphere, 2011,83(7):897-902.

Bioaccumulation and biotransformation of perfluorooctane sulfonamide in wheat and earthworms.

WU Si-han, WU Yu-meng, WANG Shuang-jie, CHEN Meng, LIU Qing, ZHU Ling-yan*

(Key Laboratory of Pollution Processes and Environmental Criteria of Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China)., 2021,41(5)：2434～2440

The bioaccumulation and biotransformation of perfluorooctane sulfonamide (PFOSA) in wheat and earthworms was investigated in different culture media by different culture methods. The results indicated that PFOSA was effectively absorbed by wheat roots from the culture media and translocated from roots to shoots. The bioavailability of PFOSA in soil was significantly affected by the soil total organic carbon (TOC) content. The bioavailability of PFOSA in the soil with higher TOC content was reduced, resulting in the bioaccumulation factors in wheat and earthworms decreased from (61.24±8.42) and (21347.91±208.86) to (5.61±0.23) and (1404.92±108.21), respectively. PFOSA could be transformed into PFOS in the earthworms as well as in the roots and shoots of wheat, but the transformation rate of PFOSA in the earthworms ((3.87±1.71)%) was significantly lower than that in the wheat ((26.39±3.02)%). The ratio of branched PFOS isomers (-PFOS) in the wheat roots was (14.8±2.0)% and (66.1±26.2)% at low and high TOC content, respectively, lower than those in the shoots ((63.0±21.3)% and (85.2±2.4)%), respectively), which might be because it was easier to translocate-PFOS formed in roots to shoots. The ratio of-PFOS in wheat, especially in wheat shoots ((85.2±2.4)%), was significantly higher than that in earthworms ((16.5±4.0)%). The presence of wheat enhanced the bioavailability of PFOSA in the soil, thereby promoted the accumulation of PFOSA in earthworms, but had little effect on the transformation of PFOSA. The results provided evidence for the bioaccumulation and biotransformation of PFOSA in wheat and earthworms, and were helpful to explore the indirect sources of PFOS in the environment.

PFOSA；wheat；earthworm；bioaccumulation；biotransformation

X131

A

1000-6923(2021)05-2434-07

吴思寒(1998-),女,河南安阳人,南开大学硕士研究生,主要从事全氟和多氟化合物环境行为研究.

2020-10-08

国家重点研发计划(2018YFC1801003,2019YFC1804203),国家自然科学基金资助项目(41991313,21737003)

* 责任作者, 教授, zhuly@nankai.edu.cn