Vertical Concentration Distributions of Arsenic in a Reservoir and Its Sediment

Abstract

Abstract Vertical concentration distributions of arsenite and arsenate in a reservoir (depth, ≈31 m) and its bottom sediment (core depth, ≈18 cm) have been investigated. The concentrations of arsenite and arsenate in the water were determined by a spectrophotometric method, and those in the sediment were also determined by the same method after the following leaching-treatments of the sediment. The leaching of arsenic from the sediment was carried out by using three solutions; (1) 0.1 M hydrochloric acid (acid-soluble fraction), (2) 1 M sodium hydroxide solution (alkali-soluble fraction), and (3) hydrofluoric and perchloric acid mixture (silicate fraction). It was found that arsenic was rich in the surface layer of the sediment, and most of it existed as arsenite fixed with iron hydroxide. Based on the analytical and leaching results of arsenic, iron, manganese, zinc, copper, and others in the reservoir and in its sediment respectively, the sedimentation process of arsenic from the reservoir and its dissolution process from the sediment have been discussed.