| The carbon cycle is the main focus in the research of biogeochemistry now, freshwater lakes are important component of the global carbon cycle, and they also are the important object for the global change research because lakes are the important ecosystem. This study was based on gradient method to study the temporal and spatial variation of greenhouse gases (CO2, CH4and N2O) exchange of the water-air interface in large shallow lakes-Taihu Lake, and it alao analysis the environmental variables affecting the greenhouse gases concentration and exchange flux. It is aim at providing data to help estimate the emission of greenhouse gases in lake and other aquatic ecology system and quantitative the global greenhouse gases budget. The results of this study are as follows:The variations of greenhouse gases concentration in Lake Taihu have obviously characteristics.(1) There are obvious seasonal variations for CO2concentration, the result shows that there are high concentration in autumn and winter and low concentration in spring and summer, and there are significant diurnal variation and depth profile variation of CO2concentration in spring and summer, the CO2concentration are34.06,32.72,34.61, and46.96μmol·L-1in spring, summer, autumn, and winter, respectively. The CO2concentration in water body of Lake Taihu have a strong spatial variation throughout the year, it is very high in the northwest coastal region. The CO2concentration in Lake Taihu are positive correlated with wind speed and the concentration of dissolved oxygen, and negative correlated with air temperatyre、 solar radatiom water temperature and pH.(2) There are very obvious seasonal variations for CH4concentration, the result shows that there are high concentration in spring, summer and autumn and low concentration in winter, and there are no significant diurnal variation throughout the year, but there are significant depth profile variation in spring and summer, the CH4concentration are136.72,177.38,239.97, and43.89nmol·L-1in spring, summer, autumn, and winter, respectively. The CH4concentration in water body of Lake Taihu have a strong spatial variation throughout the year, it is very high in the northwest coastal region, east coast region, and East Lake Taihu. The CH4concentration in Lake Taihu are positive correlation with air temperature and water temperature, and negative correlated with wind speedd and the concentration of dissolved oxygen (3) There are no obvious seasonal variations for N2O concentration, and there are also no diurnal variation and depth profile variation throughout the year, the N2O concentration are15.19,11.18,11.49, and16.13nmol·L-1in spring, summer, autumn, and winter, respectively. The N2O concentration in water body of Lake Taihu have a strong spatial variation throughout the year, it is very high in the northwest coastal region. The N2O concentration in Lake Taihu are negative correlated with air temperature, solar radiation, water temperature, and the concentration of dissolved oxygen.There are some certain characteristics of temporal-spatial variation in the exchange of water-air interface in Lake Taihu.(1) The results show that Lake Taihu are the CO2source for atmosphere in general, and the emission flux are high in spring, summer, and autumn, but it is low in winter, the annual emission flux are15.54,29.90,17.40, and13.84mmol·m-2·d-1in spring, summer, autumn, and winter, respectively. The CO2flux of water-air interface of Lake Taiu have a strong spatial variation throughout the year, it is very high in the northwest coastal region. The CO2flux are positive correlated with air temperature, wind speed, and water temperature, and negative correlated with pH and the concentration of dissolved oxygen.(2) The results show that Lake Taihu are always the CH4source for atmosphere, and the emission flux are high in spring, summer, and autumn, but it is low in winter, the annual emission flux are0.14,0.21,0.19, and0.03mmol·m-2·d-1in spring, summer, autumn, and winter, respectively. The CH4flux in water body of Lake Taihu have a strong spatial variation throughout the year, it is very high in the northwest coastal region, east coast region, and East Lake Taihu. The CH4flux are positive correlated with air temperature, wind speed, solar radiation, and water temperature, and negative correlated with the concentration of dissolved oxygen.(3) The results show that Lake Taihu are the weak N2O source for atmosphere, the emission flux are high in spring and summer and low in autumn and winter in general, the annual emission flux are0.01,0.005,0.001, and0.0006mmol·m-2·d-1, respectively. The N2O flux in water body of Lake Taihu have a strong spatial variation throughout the year, it is very high in the northwest coastal region. The N2O flux are significant positive correlated with air temperature, wind speed, solar radiation, and water temperature, and negative correlated with the concentration of dissolved oxygen.The GWP of greenhouse gases in Lake Taihu is415.66g CO2·m-2·a-1, and the emission factor of N2O in Lake Taihu is0.146%. |
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