Temporal and spatial variation of carbon dioxide concentration and its exchange fluxes in Lake Chaohu

Abstract

In order to understand the temporal and spatial variation of carbon dioxide concentration (cCO2)and its influencing factors in the surface water of Lake Chaohu, the physicochemical parameters, biological parameters, and cCO2 of surface (15-30 cm)water samples collected in February, April, August and November in 2017 from Lake Chaohu, representing different seasons, were measured. The surface water-air flux of CO2 was then calculated based on gradient method as well. The results showed that the cCO2 ranged from 13.31-55.47 μmol/L. The average annual cCO2 was 26.27 μmol/L. The cCO2 was higher in the west lake sub-lake zone than that in the central and east sub-lake zones. The surface water of Lake Chaohu had a lower cCO2 in the warm season (summer) than in cool and cold seasons (spring, autumn and winter). cCO2 was positively correlated with dissolved organic carbon (DOC)concentration and negatively correlated with chlorophyll-a concentration, suggesting that photosynthesis and decomposition of organic matter plays an important role in the biochemical cycle of CO2. Due to the serious pollution of inflowing rivers surrounding Lake Chaohu, DOC input from the watershed supplied substrates for CO2 production. Lake Chaohu was a relatively small source for atmosphere CO2 compared to others studies. Lake Chaohu shifted from a CO2 source to a sink in cold seasons.