Trace metals in water and sediment from a tropical watershed subject to anthropogenic inputs

摘要

Sixteen stations were established to assess water and sediment quality throughout the Caura/Tacarigua watershed. Samples were analyzed for Cd, Cr, Cu, Fe, Ni, Pb, Zn and Hg using atomic absorption spectrometry during the dry and wet seasons of 2005. In the dry season, Pb and Zn exceeded sediment quality guidelines for the protection of aquatic life. Highest concentrations of all metals were recorded at one station subject to a range of anthropogenic inputs in the lower watershed area; Cu exceeded the water quality guideline at this station. In the wet season, Zn exceeded the SQG at one station located south of residential areas in the lower watershed area and highest concentrations of Cr and Pb were recorded at that station. Metals in water were detected primarily at stations in the lower watershed area. Wet season concentrations of Zn in water were significantly higher than corresponding dry season concentrations. Likely sources of trace metals in the watershed include effluent from a light industrial estate, sewage/domestic waste from non-functioning sewage treatment plants and pit latrines, agricultural and urban runoff. Results of this study show that management strategies using an integrated approach are needed to minimize trace metal pollution within the watershed.