Distribution and sources of heavy metals in stream sediments in Tum Talu watershed Bunnung Sata Yala Southern Thailand

Abstract

Recently metals contamination in the Pattani river has become an acute problem of Pattani city. The abandoned mines in the Tum Talu watershed are suspected to be sources of heavy metals pollution in surface and groundwater system. Field investigations and stream sediments sampling have been carried out to examine the distribution pattern and sources of toxic metals. Fine fractions of stream sediments collected from 63 locations underwent partial digestion, and were analyzed by ICP-OES for As, Cd, Pb, Cr, Cu and Zn concentrations. Mine waste dumps, mineralized outcrops and landfill leaks discharging typical acid mine drainage clearly indicate that they are sources of contaminant metals. Distribution patterns show markedly high levels of metals in the downstream areas of abandoned mines and landfills. Concentrations of As, Pb and Cu decrease slightly downstream areas, away from sources at abandoned mines and landfills, but Zn and Cd concentrations gradually increase. The As, Cd, Pb, Cu and Zn concentrations begin to be contaminated upstream areas of abandoned miens and seriously contaminated downstream areas of abandoned mines and landfills. Chromium concentration is not a contaminant in this watershed. Antropogenic activity in the watershed, waste emanating from abandoned mines and especially leakages from landfills which contain hazardous wastes, are major sources of toxic metals contaminating stream sediments in the Tum Talu watershed. However, mineralization of skarns and ores which are considered as being natural occurrences are very minor sources.