Abstract
Heavy metals, including arsenic from abandoned mines, are easily transported with sediment and deposited in waterbodies such as reservoirs and lakes, creating critical water quality issues when they are released. Understanding the leaching of heavy metals is necessary for developing efficient water quality improvement plans. This study investigated how arsenic leaches from different soil and sediment types and responds to hydrologic conditions to identify areas susceptible to arsenic contamination. In this study, batch- and column-leaching tests and sequential extraction procedures were used to examine arsenic leaching processes in detail. The results showed that most arsenic-loaded sediments accumulated in the vicinity of a reservoir inlet, and arsenic in reservoir beds have a higher leaching potential than those from agricultural land and stream beds. Arsenic deposited at the bottom of reservoirs had higher mobility than that in the other soils and sediments, and arsenic leaching was closely associated with the acidity of water. In addition, arsenic leaching was found to be responsive to seasons (wet or dry) as its mobilization is controlled by organic compounds that vary over time. The results suggested that temporal variations in the hydrochemical composition of reservoir water should be considered when defining a management plan for reservoir water quality.
Highlights
Acid mine drainage and materials left at abandoned mines can cause significant pollution problems [1,2,3,4,5]
The highest average arsenic concentration was found in effluent from the reservoir sediment (0.026 mg/L); the average concentrations coming from the agricultural land soil (0.018 mg/L) and the stream sediment (0.019 mg/L) were similar to each other, but the concentrations of the soil samples from agricultural land show considerably greater variability (Figure 4)
This means that the arsenic concentrations in each agricultural land of this study area varied, and were not considered to be highly contaminated; certain agricultural lands which were readjusted using soil highly contaminated with mine tailings when the arable lands were altered show aAppl
Summary
Acid mine drainage and materials left at abandoned mines can cause significant pollution problems [1,2,3,4,5]. For efficient management of the quality of irrigation water, understanding of how heavy metals leach from contaminated sediments and soils is required [13]. As various studies stressed and analyzed deposition [27] and diffusive gradient [28,29,30,31] characteristics related to the arsenic bioavailability (heavy metals and other persistent pollutants) in water and sediments, we considered the seasonal effects (differences of the water quality between wet season and dry season, especially soluble organic matter) on arsenic leaching characteristics. In the column-leaching test, water quality in the wet and dry seasons were separately considered to understand the effects of different hydrologic conditions on arsenic leaching and contamination in the reservoir
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