Emmission Characteristics And Influencing Factors Of CO₂,CH₄,N₂O Fluxes In Different Levels Of Ditches In Chongzhou City

The rapid increase of greenhouse gases in the atmosphere is one of the main reasons for global warming.The top three greenhouse gases that contribute the most to the global greenhouse effect are CO₂,CH₄,and N₂O.Ditches are one of the most important and common landscape element in plain agricultural areas.There are key places for the interception,transformation and transmission of nutrients such as C,N and P,and they occupy important positions in the global C,N and P balance,they are also as a potential source of greenhouse gas emissions.In order to study the emmission fluxes characteristics of CH₄,CO₂,N₂O in different levels of ditches and their influencing factors,three ditches?main ditch,branch ditch,lateral ditch?were monitored from July 2016 to June 2017 by static floating chambers-Gas Chromatography method in Chongzhou City of Chengdu Plain.The sampling frequency of CO₂,CH₄ and N₂O emissions at different levels of the ditches water-gas interface was twice a month.When collecting samples,environmental parameters and the physicochemical properties of the overlying water and sediment were analyzed.Finally,the spatial-temporal distribution characteristics of CO₂,CH₄ and N₂O at the water-gas interface of the ditches and the major water qualities and environmental impact factors were identified.The main conclusions are as follows:?1?During the observation period,all levels of ditches showed a net source of CO₂,CH₄and N₂O emissions.The CO₂ emission flux of main ditch,branch ditch and lateral ditch were range from70.38⁵42.65?115.30⁹45.80 and 128.28¹188.00 mg·?m²·h?^-1,respectively.The CH₄ emission flux were range from 8.80¹68.27?7.18¹21.08?9.28⁵6.66mg·?m²·h?^-1,respectively.The N₂O emission flux were range from 7.97¹12.34?10.77¹89.70?13.12²36.06?g·?m²·h?^-1,respectively.?2?The seasonal variations of greenhouse gas emissions from the water-gas interface of the ditches were obvious.The average emission fluxes of CO₂ and N₂O in the 3 ditches were all showed that summer>spring>autumn>winter.The average emission flux CH4 in the three ditches were all showed that autumn and winter are higher than the spring and summer.The three greenhouse gas emission fluxes of the main ditch water-gas interface showed significant variations in daytime and nighttime.The average emission fluxes of CO₂,CH₄ and N₂O in the daytime were all higher than those in the nighttime.?3?There were many clear spatial differences in the CO₂,CH₄ and N₂O emission fluxes at the water-air interface of the ditches.The average emission fluxes of CO₂ and N₂O from the lateral ditch were significantly higher than those from main ditch and branch ditch?P<0.05?;the average emission flux of CH₄ from the main ditch was significantly higher than that from the branch ditch and lateral ditch?P<0.05?.?4?The main environmental and water quality parameters affecting the CO₂,CH₄ and N₂O emission fluxes at the water-air interface in the ditches ecosystem were not the same.The most important environmental factor affecting CO₂ and N₂O was water temperature;the most important environmental factor affecting CH₄ was the flow rate;the most important water quality parameter affecting CO₂ was TN;the most important water quality parameter affecting CH₄ and N₂O was DO.