Abstract
Lakes are a crucial component of the global carbon and nitrogen cycle. As a trend of enhanced human activities and climate change, the mechanisms of burial remain poorly understood. In this study, diverse biogeochemical techniques were applied to analyze the temporal variation of organic carbon and nitrogen burial rates in Chaohu Lake. The results showed that burial rates have ranged from 9.39 to 35.87 g C m(-2) yr(-1) for carbon and from 1.66 to 5.67 g N m(-2) yr(-1) for nitrogen since the 1860s. The average rates were 19.6 g C m(-2) yr(-1) and 3.14 g N m(-2) yr(-1) after the 1970s, which were significantly higher than the rate before the 1970s, showing an increasing trend. The decrease of C/N ratios as well as organic matter δ(13)C values indicates that the major organic matter source in sediment has been algal production since the 1970s. The increase of δ(15)N values indicated that the promotion in productivity was stimulated by nutrient input from sewage and agricultural runoff. The burial rates of organic carbon and nitrogen were significantly positively related to socio-economics and temperature, indicating that Chaohu Lake will become an increasing carbon and nitrogen pool under conditions of enhanced human activities and intensive precipitation.