Anthropogenic Influences on Environmental Changes of Lake Bosten, the Largest Inland Freshwater Lake in China

A short lacustrine sediment core (41 cm) from Lake Bosten in arid central Asia was used to investigate the environmental changes that occurred in the past approximate to 150 years based on the superposition of climate and anthropogenic factors. Geochemical elements, total organic carbon (TOC) and nitrogen (TN), and stable isotope data (delta C-13(org) and delta N-15) were used to identify abnormal environmental changes. The average C/N ratio in the sediments of Lake Bosten suggested that the organic matter in lake sediments was mainly from aquatic plants. The delta C-13(org) and delta N-15 in the lake sediments mainly reflect changes in the structure of the lake's ecosystem. Before the 1960s, the primary productivity of the lake was relatively low with a relatively stable lake water environment. From the 1960s to the mid-1980s, the lake's ecosystem was closely related to a significant decline in water levels caused by human activities and an increase in salinity. From the late 1980s to approximate to 2000, the aquatic plant structure of Lake Bosten did not change significantly. After 2000, the upper part of the sedimentary record suggested enhanced productivity due to urban and industrial development in the catchment area. However, sedimentary perspectives of the responses of different environmental proxies in sediments to human activities were anisochronous, and the increasing heavy metal (Pb and Cu) and P accumulations appeared in 1970, reflecting heightened human impacts. Through the comparison between the Aral Sea and Lake Bosten, it was inferred that, under the intervention of human activities, the lake experienced a completely different evolution trend. Humans, as geological agents, should protect our living environment while satisfying social development. The results will provide an important supplement to a large spatial scale study of the influences of human activities on the environment in Central Asia, which also has some significant implications for the protection of the ecological environment and the realization of sustainable development in arid regions.