Geochemistry of major and trace elements and their environmental significances in core sediments from Bosten Lake, arid northwestern China

Geochemistry of Bosten Lake sediments in northwest China

Geochemical element concentrations of a 41-cm-long sediment core from Bosten Lake were analyzed with grain size, total organic carbon and total inorganic carbon, and environmental evolution over the past ~150 years was reconstructed. Based on principal component analysis (PCA) and correlation analysis of the elements, three controlling factors for vertical distribution characteristics of elements were identified, the first factor was the combined effects of terrigenous detritus and endogenous carbonate, the second controlling factor was the granularity effects of the lake sediment, the third controlling factor was the input from human activities. A first stage was from the 1870s to the 1950s, Bosten Lake was in a natural state, the deposition rates were relatively low, and the concentrations of Ca, Sr, and Ba were high. The second stage was from the 1960s to the 1990s, triggered by the inflow of agricultural return water, the sedimentation rates were clearly higher than the former stage, the concentrations of Al, Fe, and K increased notably, and Ca, Sr, and Ba decreased. The third stage comprised the period since the 2000s, the scope of human activities has been extended. Enrichment factors of Cd, Pb and P of the sediment have increased. The economic development in the basin led to an increase in pollution of the lake. Human impacts on the environmental change were embodied in the enrichment of Cd, Pb, and P, and the clear decline of biogenic Ca. Sediment geochemistry has faithfully recorded the impacts of human activities on the environmental changes of Bosten Lakes.