IDENTIFICATION AND DISTRIBUTION OF INORGANIC COMPONENTS IN WATER: WHAT TO MEASURE?

Abstract

The molecular form as opposed to the total quantity of inorganic components in water often determines the role that these components play in the aquatic environment. Although the metal aquo ion is generally thought to be the reactive form for biologic interactions, the fraction of the total metal present in this form may be small and highly variable, depending on the available complexing ligands and the magnitude of the interactions. Calculations by use of the chemical equilibria model and the inorganic components in Lake Superior water as an example show the distribution of metals and ligands water to be complex and indicate that analytic measurements must be sensitive in the range of 10/sup -8/ to 10/sup -12/ M for most metals. Solutions that contain the same total metal concentration may be made completely nontoxic by adding complexing ligands. The comparison of calculated molecular distribution with effects on D. magna show that NTA and EDTA dominate the aquo chemistry of copper and cadmium, but not mercury. Mercury can be made nontoxic with cysteine. Metals introduced to water in the form of silicate mineral particles show some transfer to water and fish tissue but on the basis of total metal measurement wouldmore » contribute little total metal tissue content. The analysis of drinking water from Duluth on a continuous basis for suspended contaminates and at different locations shows large fluctuations caused by a variety of factors. Asbestiform fiber and mass content vary over almost two orders of magnitude. Changes in time, processes, and materials over the years result in changes in the water supply. Lead, chlorine, ammonia, asbestiform fibers, hexafluorosilicic acid, and glass have been introduced to the drinking water at various times, locations, and concentrations. Studies designed to look at the overall result of these components must consider all of the sources and variations.« less