Abstract
Using 137Cs and 210Pb dating and multi-proxy evidence from a 41-cm sediment core from Bosten Lake in China, the responses of sediment grain size to environmental changes were reconstructed over the past 150 years. After the end of the Little Ice Age, the climate of the Bosten Lake region became warmer and drier, and the lake water level decreased. The results indicated that the lowest water storage periods occurred at approximately 1920–1930 AD. Decreases in the Siberian High intensity and water vapour transport from the Indian Ocean during this period led to a reduction in the water vapour supply, which resulted in reduced lake levels in the period 1920–1930 AD. Then, the lake was at a high level until the 1960s. The water storage then declined in the 1960s. Since the 1960s, the contents of total organic carbon and total nitrogen have significantly decreased, which is closely related to the significant decline in water level and increased water salinity caused by enhanced water demands. Increased irrigation water demand as a result of expanding cultivated areas and climate change, coupled with a reduced input of water vapour, resulted in the worst water environment in approximately 1980–1990 AD. Since the late 1980s, the water level of the lake has risen, and the lake primary productivity of Bosten Lake has improved. Through the application of statistical methods to grain size data from Bosten Lake combined with the abovementioned data on climate change and human activities, two major potential factors influencing the grain size of terrigenous clastic material were revealed. The first factor, consistent with a grain size of 3.31 μm, is related to the recent increase in agricultural acreage in the Bosten Lake watershed and may reflect increases in atmospheric dust. The second factor, correlated with grain sizes of 11.48 μm and 69.18 μm, can be used to reflect changes in the lake hydrological state. It is suggested that the grain sizes of these lake sediments sensitively reflect changes in the hydrological characteristics of the basin and can be used to reconstruct the history of climate change and human activities.
Highlights
Lake sediments record the history of human-environment interactions[1] and have been used to reconstruct the environmental evolution on different time scales and to assess the impacts of human activities[2]
Despite the existing body of research of Bosten Lake, few studies have focused on the sediment grain-size distribution in response to changes in the lake environment in response to climatic and anthropogenic influences, which could provide insights into the underlying mechanisms forcing environmental changes under the superimposed influences of climate change and intensified human activity
The specific activity of excess 210Pb was determined by measuring the amount of 210Pb and 226 Ra in the same layer. 210Pb and 226Ra were equilibrated at 39 cm, and the chronology of the sediment was established by the constant rate of supply (CRS) model with supported 210Pbex (210Pbex = 210Pb-226Ra)[40]
Summary
Lake sediments record the history of human-environment interactions[1] and have been used to reconstruct the environmental evolution on different time scales and to assess the impacts of human activities[2]. Under the combined influence of human activities and climate change, rapid changes in lakes in the arid regions of Central Asia, such as the Aral Sea[14], Bosten Lake[15], Ebinur Lake[16], and Lop Nur[17], have raised concerns in the past few decades. Despite the existing body of research of Bosten Lake, few studies have focused on the sediment grain-size distribution in response to changes in the lake environment in response to climatic and anthropogenic influences, which could provide insights into the underlying mechanisms forcing environmental changes under the superimposed influences of climate change and intensified human activity. The results will enrich the palaeo-environmental significance of multiple proxies from lake sediments and will be used to better understand the important role of human activities in influencing lake environmental change. The salinity showed an increasing trend, with values of 0.4 g/L in 1958–1960, 1.60–1.87 g/L in 1980–1991, 1.17 g/L after 1992, and 1.48 g/L in 200837,39
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
