TOC and Black Carbon records in sediment of Lake Yangzong, Yunnan Province under the influence of human activities during the past century

Abstract

Multi-proxy, including total nitrogen (TN), total organic carbon (TOC), black carbon (BC) and its stable carbon isotope (δ13CBC), were analyzed in the 40 cm sediment core from Lake Yangzong in Kunming city,Yunnan province. The sediment core was dated using 137Cs and 210Pb, and then we discussed the deposition processes of TOC and BC responding to human activities during the past 100 years in Lake Yangzong Basin. The results showed that:(1)the contents of TN,TOC and BC in the core of Lake Yangzong ranged from 0.76 to 5.07 mg/g, 4.95 to 42.65 mg/g, 0.69 to 11.16 mg/g, respectively, and the δ13CBC values ranged from -31.03‰ to -25.45‰ with a mean of -27.18‰; (2) the TN and TOC contents were both increased from the bottom to the top of the sediment core, and the molar ratio of TOC/TN reached a maximum in 1994 A.D. then gradually decreased, which indicated that the exogenous pollutants produced by human activities in the basin were continuously discharged into the Lake Yangzong, and led to an eutrophication of the lake; (3) the changes of BC and δ13CBC series in the sediment core in Lake Yangzong reflected the changes of local energy structure. With the rapid development of population growth and industrialization, carbon emissions were accelerated by the present energy consumption structure which were primarily depended on coal, and industrial and residents' consumption became the main sources of BC in Lake Yangzong. In addition, significant correlations were found between the BC and the population.