Arsenic in drinking-water: background document for development of WHO guidelines for drinking-water quality

Overview

1.4 Environmental fate

Arsenic is introduced into water through the dissolution of rocks, minerals and ores, from industrial effluents, including mining wastes, and via atmospheric deposition (IPCS, 1981; Nadakavukaren et al., 1984; Hindmarsh & McCurdy, 1986). In well oxygenated surface waters, arsenic(V) is generally the most common arsenic species present (Irgolic, 1982; Cui & Liu, 1988); under reducing conditions, such as those often found in deep lake sediments or groundwater, the predominant form is arsenic(III) (Lemmo et al., 1983; Welch et al., 1988). An increase in pH may increase the concentration of dissolved arsenic in water (Slooff et al., 1990).

2. Analytical Methods

A silver diethyldithiocarbamate spectrophotometric method is available for the determination of arsenic; the detection limit is about 1 µg/litre (ISO, 1982). Graphite furnace atomic absorption spectroscopy, hydride generation atomic absorption spectrophotometry and inductively coupled plasma mass spectrometry (ICP-MS) are more sensitive. High-pressure liquid chromatography in combination with ICP-MS can also be used to determine various arsenic species (Irgolic, 1982).