Research On The Variation Law And Influencing Factors Of Greenhouse Gas Emission Fluxes In Different Water Bodies

Aquatic ecosystems are important sources of greenhouse gas emissions.Regional differences,spatial heterogeneity and complex and fragmented underlying surfaces have brought huge challenges to the accurate accounting of carbon and nitrogen emissions from aquatic ecosystems.In this study,four types of water bodies were selected,including rivers,reservoirs,aquaculture ponds and landscape water bodies in Nanjing,with a total of 13sampling points.Using the floating static chamber method to observe the greenhouse gas fluxes at the water-gas exchange interface for one year,to explore the temporal and spatial variation of greenhouse gas emission fluxes at the water-gas exchange interface in different water bodies,and to clarify the key impact mechanisms of 14 environmental factors on greenhouse gas emissions from different water bodies.Finally,the observation data was used to estimate the total amount of greenhouse gas emissions of regional water bodies,in order to provide data support for the estimation of carbon and nitrogen emissions of regional water bodies in China,provide first-hand data for the revision of carbon and nitrogen models,and provide theoretical support for my country to achieve"carbon neutrality".The main conclusions of the study were:(1)From the perspective of time variation,the fluxes of carbon dioxide(CO₂),methane(CH₄)and nitrous oxide(N₂O)all reached their maximum in summer,and the minimum fluxes of CO₂ and CH₄ appeared in winter,while the minimum fluxes of N₂O appeared in spring.All three greenhouse gases were shown as net emissions throughout the year Temperature was a key factor driving the three greenhouse gases at the same time,indicating that aquatic ecosystems may exhibit stronger greenhouse gas emission capabilities in the context of climate warming.(2)From the perspective of water body types,landscape water bodies exhibited the strongest CO₂ and CH₄ emission capacity,with small landscape water bodies being the most prominent.Its CH₄ flux was 6450.76±11076.10?g·m^-2·h^-1,which was about 2.5 times the average discharge level of global water bodies.Small landscape water bodies were the hotspots for CH₄ emissions,and important influencing factors such as small area,shallow depth,low concentration of dissolved oxygen(DO)and no water exchange with the outside world were the main reasons for the high CH₄ emissions.Aquaculture ponds had the strongest N₂O emission capacity due to high nutrient loading levels and high sulfide concentrations.(3)In this study,the global warming potential(GWP)of greenhouse gas emission fluxes of different types of water bodies presented a changing trend of landscape water bodies>rivers>aquaculture ponds>reservoirs.In addition,based on the observation data and combined with land use type data,the total annual greenhouse gas emissions in Nanjing and Jiangsu were estimated to be 4.75×105 t and 8.77×106 t of CO₂ equivalent,respectively.The warming effect was equivalent to 0.056%and 1.04%of the total CO₂ emissions in Jiangsu Province in 2018,which should not be underestimated.