Spatiotemporal Variation And Influencing Factors Of CO₂ Emission Flux In Longkaikou Reservoir

Under the background of global warming,the Greenhouse gas emissions from reservoirs attracts more and more attention.For in-depth understanding of the temporal-spatial distribution characteristics of the CO2 flux and its influencing factors in Subtropical reservoir,The Longkaikou reservoir on the Jinsha River was selected as a research case.In 2015(March,July,August,September and November),air samples at 8 survey points in the reservoir were collected by static chamber-gas chromatograph technique,which were sampled and measured 5 times of the water vapor interface CO2 flux.Meanwhile,water quality in-situ such as surface temperature,dissolve oxygen,pH and turbidity were tested.Based on the analysis of the test results,the following conclusions are drawn:(1)The Longkaikou reservoir is mostly the source of atmospheric CO2 within the surveying time,and the average value of CO2 flux in the reservoir area is 631.82 mg·m-2·d-1,the average value of CO2 flux is mg·m-2·d-1 in the upper and lower reaches of the dam,and the estimated value of annual CO2 emission in the reservoir area is 3470.75 t.(2)The spatiotemporal distribution characteristic of CO2 flux in Longkaikou reservoirSeasonal variation characteristics:The Longkaikou reservoir are annually the source of atmospheric CO2;wet season's flux is higher than that in dry season,flux in July and August is generally highest,while value in November is lowest.The order of the mean flux is August>July>September>March>November.Space variation characteristics:stronger emission happen at the tail of reservoir and the area close to dam,stronger on absorption occured in middle reaches of the reservoir.At the point downstream the dam,C02 emiss in July and August,but were absorpted in March and September and November.The specific order of values could be showed as,middle part>nearby dam>tail of reservoir>downstream dam in March,tail of reservoir>nearby dam>downstream dam>middle part in July,the rule of August is same as July,tail of reservoir>nearby dam>middle part>downsteam dam in September,nearby dam>tail of reservoir>middle part>downstream November.(3)The relationship between CO2 flux of the Longkaikou reservoir and in-situ water environment factors:the CO2 flux has a significant negative correlation with dissolved oxygen,and positive correlation with the pH value,the correlation of water temperature and turbidity is not obvious.(4)The CO2 flux level of Longkaikou reservoir is far lower than that of tropical and temperate reservoirs.