TRACE-METAL SPECIATION IN A TROPICAL ESTUARY - SIGNIFICANCE OF ENVIRONMENTAL-FACTORS

Speciation studies on the metals Cd, Cu and Zn were carried out in the Periyar and the Muvattupuzha Rivers and the adjoining estuary, a typical tropical waterway in southwest India. Metal species were classified as: (i) dissolved (0.45 μm) (AAS); (ii) Chelex-100 labile (ASV); (iii) metal released upon UV irradiation (AAS) and Chelex-100 labile metal released upon UV irradiation (ASV); (iv) exchangeable particulate-associated metal; and (v) total particulate-associated metal. Samples of particulate matter were treated with HOAc to obtain the exchangeable metal fraction, while strong acid digestion yielded the acid-leachable fraction. The results indicate the presence of varying proportions of metal species and their affinity to bind with solid phases. The particulate fractions of metals determined reveal the role of sorption processes in regulating trace metal levels. This study highlights the influence of numerous environmental factors, such as (a) the influx of riverine input of metals regulated by dams/reservoirs; (b) introduction of industrial effluents and sewage; (c) modifications arising from anthropogenic activities; and (d) hydrographic changes related to complexity of water use. © 1990.