Study On Greenhouse Gas Fluxes At The Air-water Interface In Erhai Lake

The study of carbon flux at the air-water interface in the lake is of great scientific significance to the exploration of the global carbon cycle.Based on the observation data of CO2 and CH4 fluxes at the air-water interface in Erhai Lake,the time and spatial distribution of greenhouse gas fluxes at the air-water interface of Erhai Lake were analyzed by using a Closed-chamber and Gas Chromatography-based System.The results in the study are as follows:(1)Diurnal variation of the CO2 fluxes at the air-water interface is obvious,Releasing CO2 into the atmosphere at night while absorbing CO2 during the day.Erhai is the sink of atmospheric CO2 in the rainy season.However,Erhai during the dry season is the source of CO2.The CO2 flux of the algae dominated zone is larger than that of the macrophyte dominated zone.Calculated average daily CO2 fluxes for the algae dominated zone in September and November are 7.32 and 118.55 mg·m-2·h-1,respectively.Average daily CO2 fluxes for the macrophyte dominated zone in September and November are-260.88 and 1.92 mg·m-2·h-1,respectively.The CO2 fluxes in the northern and central water areas are smaller.The reason may be that these water areas have more aquatic plants and great photosynthesis intensity.(2)There is no obvious diurnal variation of CH4 fluxes at the air-water interface in Erhai Lake.Because of the high temperature and high nutrient level,the average daily CH4 flux in the rainy season is greater than that in the dry season.The algae dominated zones have a high level of nutrition and greater CH4 emission fluxes.Calculated average daily CH4 fluxes for the algae dominated zone in September and November are 38.88 and 26.98 ?g·m-2·h-1,respectively.Average daily CH4 fluxes for the macrophyte dominated zone in September and November are 19.63 and 2.24 ?g·m-2· h-1,respectively.The northern and the southern lake region has a lot of organic sediments.So the two water areas have larger CH4 emission fluxes.The nearshore water areas are connected to inflow lakes.There are high tropic level and rich aquatic plants,which is conductive to the production and transmission of CH4.(3)Correlation analysis results show that CO2 flux has significant negative correlation with water temperature,air temperature,dissolved oxygen concentration and pH value,but has significant positive correlation with oxidation-reduction potential.