Distribution and Geochemical Processes of Arsenic in Lake Qinghai Basin, China

Yuanxin Cao,Chunye Lin,Xuan Zhang

doi:10.3390/w13081091

Yuanxin Cao, Chunye Lin + Show 1 more

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https://doi.org/10.3390/w13081091

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Abstract

Lake Qinghai in the Qinghai-Tibet plateau is the largest lake in China, but the geochemical understanding of arsenic (As) in the lake is lacking. Water, sediment, and soil samples were collected from Lake Qinghai, rivers flowing into the lake, and lands around the lake. Water samples were analyzed for major ions and As, while sediment and soil samples were analyzed for major elements and As. The average As concentration (25.55 μg L−1) in the lake water was significantly higher than that (1.39 μg L−1) in the river water (p < 0.05), due to the evaporative concentration of lake water. The average As concentration (107.8 μg L−1) in the pore water was significantly higher than that in the lake water, due to its secondary release from sediment solid phases in the reductive condition. The average As/Cl−, As/SO42− and As/Na molar ratios in the lake water were significantly lower than that in the river water, indicating As was partially transferred from dissolved phase to solid phase in the evaporative concentration process of the lake water. The average As/Ca molar ratio in the lake water was significantly higher than that in the river water, indicating more Ca than As precipitated in the lake water. Furthermore, the average As/Ca molar ratio in the lake water was significantly lower than that in the pore water, indicating more As than Ca was secondarily released from sediment solid phases. The average concentration of As(III) and As(V) were 0.35 and 1.04 μg L−1 for the river water, respectively, and 6.99 and 18.56 μg L−1 for the lake water, indicating As(V) was the predominant As form. The average As concentration was 16.75 mg kg−1 for the lake sediment and 13.14 mg kg−1 for the soil around the lake. Arsenic concentration was significantly negatively correlated with S and Ca concentration in the lake sediments, due to solid dilution effect induced by carbonate and sulfate precipitation. The average As/Sc molar ratio in the sediment (2.06) was significantly higher than that in the soil (1.32), indicating that relatively more As was enriched in the lake sediment.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The major element concentration was generally higher in the pore water than that in the lake water
This can be linked to the secondary release from sediment solid phase in the reductive condition [37]

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Alpine lakes are among the least disturbed aquatic ecosystems [1]. Given their relative remoteness, no local impact masks the effects of large-scale changes, such as climatic and background diffuse contamination [2]. Alpine lakes can be viewed as sensors of regional and global environmental changes [2,3]

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