Environmentally sensitive grain-size component records and its response to climatic and anthropogenic influences in Bosten Lake region, China

Abstract

Using 137 cs and 210 Pb 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. 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. Among the multiple proxies derived from lake sediments, the grain-size distribution has been widely used to reconstruct environmental histories 3-7. Variations in sedimentary environments are reflected by polymodal grain-size distributions, which represent changes in transport and depositional processes 8,9. Weibull 8 and unimodal lognormal distributions 10 , end-member mixing analysis 11,12 , and standard deviation variations 13 have been used to obtain environmental grain-size compositions and to distinguish sediment sources. Lakes in arid regions play significant roles in maintaining regional ecosystems. Deteriorations in water quality and quantity can threaten the livelihoods of local people an...

Distributions, Relationship and Assessment of Major Ions and Potentially Toxic Elements in Waters of Bosten Lake, the Former Largest Inland and Freshwater Lake of China

“…The catchment area of the basin is 5.5-105 km 2 . The rivers that flow into Bosten Lake are the Kaidu River, and the Huangshui River, and only the Kaidu River is perennial [13]. The Kaidu River originates from the snowy mountains in the west; its water source is supplied by mountain precipitation and meltwater of ice and snow, and the total length of this river is 513 km [41], with an annual runoff of 3.99 billion cubic metres [42].…”

“…The research on Bosten Lake mainly focuses on the changes in the lake water level [9], as well as the physical, chemical and biological characteristics of water bodies, such as water and salt dynamics [10], weathering processes and water quality [11], and water microorganisms [12]. The regional paleoclimate and paleoenvironmental characteristics are reconstructed from the aspects of lake sediment grain size [13] and carbon isotopes [14]. Previous researchers conducted fruitful research on paleoenvironmental changes using lake sediment [15][16][17][18][19][20][21][22] and the modern ecology and environment of Bosten Lake [23][24][25][26], especially for surface sediments, e.g., studies of organic pollution [23,27], bacterial community [28][29][30][31], and PTE pollution [32][33][34].…”

Historical Change and Ecological Risk of Potentially Toxic Elements in the Lake Sediments from North Aral Sea, Central Asia

“…In lacustrine sediments, the correlation between magnetic susceptibilities measured at different frequencies is very good, and the correlation coefficient (r) can exceed 0.99 (p < 0.001), indicating that increasing magnetic susceptibility is related to an increase in the content of magnetic minerals. Previous studies have shown that MS can be used to reflect the variations in the intensity of human activities [58][59][60]. The intensification of human activities has led to the enrichment in ferromagnetic materials of surface materials entering the lake, which has led to a significant increase in magnetic susceptibility since 1970 AD.…”

Variations in Sediment Grain Size from a Lake in the Tianshan Mountain of Central Asia: Implications for Paleoprecipitation Reconstruction

“…The proxies that are sensitive to precipitation changes in lake sediments are different in different regions, for example, biomarker compounds [34,71,72], Rb/Sr ratios [73], and magnetic susceptibility [74] are sensitive to changes in precipitation in some regions. In addition, the environmental information reflected by the grain size of lake sediments in different regions is also different, for example, it can reflect wind intensity and dust transport [75,76], riverine input [77] and lake water level changes [78]; however, it can be used as a useful indicator for quantitative reconstruction of long-term paleoprecipitation in the region of Lake Ta-Lung-Chi in Tianshan Mountains. The total precipitation from April to September showed a significant downward trend from 1930 to 1975, after which an overall increasing trend began.…”