ZHANG+Yu1　WANG+Shu-bo2

【Abstract】The research progress on the current domestic and foreign about river water system of the greenhouse gas methane（CH4）， and nitrous oxide（N2O） generation， transmission and release mechanism are reviewed in this paper. At present， at home and abroad of river water system of methane production and release of the driving factors and mechanism has been basically clear， but the N2O production mechanism is not clear， multi factor interaction of river water system of N2O production and release of complex， in different regions and time of result differences. The calculation of water flux of N2O river discharge coefficient of river IPCC released based on N2O， the release amount may underestimate the river water N2O.

【Key words】River； CH4； N2O

0 Introduction

Methane（CH4）， and nitrous oxide（N2O） is second only to the main greenhouse gas carbon dioxide（CO2） content in the atmosphere， although the relatively low CO2 concentration， but the hundred years increased warming potential is about CO2 25 times and 298 times， the contribution to the total global radiation can be reached 18.1% and 6.24%[1]. In this paper， the domestic and foreign current on the river water system of greenhouse gases（CH4 and N2O production and transmission of release mechanism research progress and discussed the influence of environmental factors on greenhouse gas generation and emissions， and explores the current greenhouse gas emissions coefficient and watershed water emissions assessment methods.

1 Generation mechanism of greenhouse gas drainage system

1.1 The river of greenhouse gas CH4 mechanism

The present study mainly from the CH4 river water sediment in water instead of water in the sediment itself， CH4 is mainly produced in the acetic acid fermentation and H2 oxidation. Researchers at home and abroad of methane in water produce mechanism is now has a clear understanding that water in the CH4 is mainly in anaerobic conditions by methanogens to organic matter in the sediment of acetic acid fermentation and H2 and CO2 reduction[2].

1.2 The river of greenhouse gas N2O mechanism

The present study mainly from the N2O river water sediment in the water but not the water itself. Main source on the nitrification and denitrification process and coupled nitrification denitrification effect. In addition， there are researchers also pointed out that the alienation of NO- 3

reduction process， anaerobic oxidation of NH+ 4 and algae and absorption of nitrogen fixation process of nitrous oxide （N2O） in river water also has the contribution.

2 The transmission mechanism of greenhouse gas drainage

On the water of greenhouse gases to the atmosphere transmission， 3 main approaches have been found so far： the solution diffusion transmission and organization of aquatic plant ventilation transmission and bubble overflow[3].

1）The liquid phase diffusion solution. This is the most important way to transfer water of greenhouse gases， lakes and oceans in the field of study abroad has many rivers.

2）The transmission of aquatic plants. Laanbreok[4] pointed out that due to the lack of aquatic plants and rhizosphere soil microorganism flora interaction of methane production and process of consumption.

3）Bubble sediment and water transport. Third ways of water as greenhouse gases into the atmosphere transmission， the greenhouse gas bubbles escaping in small river basin is far from the attention of researchers.

3 River N2O generation and transmission of emission factors

N2O in water mainly from sediment nitrification and denitrification， coupled nitrification denitrification. These effects can be affected not only by the use of reactants（NH+ 4， NO- 3， NO- 2） concentration control， also by DO， water temperature and salinity influence， therefore， the above factors are the main factor N2O concentration effect of solution in water. However， in the complex environment of river water conditions， impact and emissions of N2O combination of the changes of the parameters of the complex， the researchers also have different results[5].

4 The problems and Prospects

1）the drainage system of greenhouse gas emissions overall research started late， and the current research focus areas of Yu Haiyang， the Yangtze River and the Yellow River main road， River Delta and inland lakes. For the study of small watershed system， greenhouse gas.

2）in the greenhouse gas generating mechanism， scholars at home and abroad for river water system of methane produce mechanism has a clear understanding， but for N2O generation mechanism is not clear， multi factor interaction lead to different time and space scales， the river water system N2O production mechanism with complexity and diversity.

【Interference】

[1]Azam F， Müller C， Weiske A， et al. Nitrification and denitrification as sources of atmospheric nitrous oxide role of oxidizable carbon and applied nitrogen[J]. Biology & Fertility of Soils， 2002，35（1）：54-61.

[2]Alexander L A， Simon Bindoff N L. Working Group I Contribution to the IPCC Fifth Assessment Report Climate Change 2013： The Physical Science Basis Summary for Policymakers[R].OPCC，2013.

[3]Kumar W B， Khoiyangbam R S， Raghumani Y. Nitrous oxide emission from two rivers meandering through Imphal city， Manipur， India[J].Global Journal of Environmental Research， 2011，5（3）：106-111.

[4]Baulch H M， Schiff S L， Maranger R， et al. Nitrogen enrichment and the emission of nitrous oxide from streams[J].Global Biogeochemical Cycles， 2011，25（4）：4013-4027.

[5]Galloway J N， Townsend A R， Erisman J W， et al. Transformation of the nitrogen cycle：Recent trends， questions， and potential solutions[J].Science， 2008， 320（5878）：889-920.

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