Research On The Concentration And Flux Of CO₂?CH₄?N₂O In Agricultural Watershed Of Jurong Reservoir

To clarify spatial and temporal dynamics of greenhouse gas concentration and flux in agricultural watershed of Jurong Reservoir,water samples in the agricultural watershed of Jurong Reservoir were collected from October 2015 to September 2017.By measuring the headspace gaseous greenhouse gas concentration using the method of headspace balance-gas chromatography,the greenhouse gas concentration and flux in water was calculated.In combination with parameters of water quality,factors influencing aquatic greenhouse gas concentration and flux were analyzed.Result showed that in agricultural watershed,the CO2 concentration in Jurong watershed varied from 4.69 to 579.88 ?mol L-1 within 2 years.CO2 concentration was higher in summer while lower in other three seasons within two years in rivers.CO2 concentration in reservoir was higher in winter within two years.CO2 concentration in ponds shifted to the top in summer in 2016 and spring in 2017.There were clear spatial variations in CO2 concentration in Jurong watershed.In the three kinds of water,the CO2 concentration in river was higher while the CO2 concentration in reservoir was lower.The range of CH4 concentration in agricultural watershed ranged from 0.01 to 1171.50 nmol L"1.The CH4 concentration in rivers was generally higher in summer and winter,and lower in autumn and spring.CH4 concentration in reservoir was higher in summer,spring and winter within two years.CH4 concentration in ponds shifted to the top in summer and winter.There were clear spatial variations in CH4 concentration in agricultural watershed.In the three kinds of water,the CH4 concentration in river was higher while the CH4 concentration in reservoir was lower.In agricultural watershed,N2O concentration in agricultural watershedvaried from 3.90 to 70.83 nmol·L-1 within 2 years.They all shifted to the top in winter and summer.There were clear spatial variations in N2O concentration in agricultural watershed of Jurong Reservoir.In the three kinds of water,the N2O concentration in river was higher while the N2O concentration in reservoir was lower.The CO2 emission flux of agricultural watershedranged from-60.76 to 1651.39 mg·m-2·h-1.There were obvious seasonal variations in the water bodies of agricultural watershed.The winter's CO2 emission of the three water bodies was low,and the CO2 emission flux was high in summer.The CO2 emission flux in agricultural watershed showed significant spatial variability.In the three kinds of water,the CO2 flux in rivers was higher and lower in reservoir.The CH4 emission flux in agricultural watershed ranges from-4.79 to 737.21 ?g·m-2·h-1,which were high in summer and spring.The Characteristics of Spatial Variation of CH4 Emission in agricultural watershed were obvious.In the three kinds of water,the CH4 flux in rivers was higher and lower in reservoir.The N2O emission flux in agricultural watershed ranged from-8.50 to 158.95 ?g·m-2·h-1,which were high in summer.There were obvious seasonal variations in the water bodies of Jurong watershed's N2O.In the three kinds of water,the N2O flux in rivers were higher and lower in reservoir.The water temperature had positively correlated with CO2 concentration and N2O concentration;DO had negatively correlated with the concentration CO2 concentration and N2O concentration;pH had a significant negative correlation with CH4 concentration and N2O concentration,and ORP had negative correlation with CO2 concentration.The water temperature had positive correlations with CO2 emission flux,CH4 emission flux and N2O emission flux.DO had negative correlations with CO2 emission flux and N2O emission flux,which was not significantly related with CH4 emission flux.pH was not significantly related with CO2 emission flux,CH4 emission flux and N2O emission flux.ORP had significant negative correlation with CO2 emission flux,CH4 emission flux and N2O emission flux.