Speciation of Selenium and Arsenic in Natural Waters and Sediments. Volume 2. Arsenic Speciation. Final Report

摘要

The disposal of coal combustion wastes is an environmental concern to the electrical power utilities because high concentrations of potentially toxic water-soluble trace elements, such as arsenic (As), may be released. During the last two years research was conducted to (1) develop a methodology for As speciation in waters and sediments, (2) predict the equilibrium speciation of As in natural waters using geochemical modeling techniques, and (3) determine the chemical speciation of As in fresh water and sediment of a reservoir which receives coal fly ash. The analytical methodologies have been developed for collection, storage and analysis of freshwater and sediment without significantly altering the speciation of As. Arsenic speciation of water and sediment is simply and reproducibly achieved using hydride generation in conjunction with atomic absorption detection. Very rapid freezing by immersion in liquid nitrogen followed by storage at -80 deg C is necessary to prevent oxidation of As (III) to As (V) during storage of water samples. Arsenic species are selectively extracted from sediment. At pH 2.3, As (III) is extracted and at pH 11.9 As (V) MMA and DMA are extracted. Field samples were collected from Hyco Reservoir in February and July 1984. The reservoir is apparently contaminated by As discharged from a coal fly ash pond. The majority of As is in the (V) valence state in the water column and ash pond. However, in the interstitial water squeezed from the reservoir sediments, As is equally divided between (V) and (III). 9 figs., 25 tabs. (ERA citation 11:039521)