Determination of levels of Mn, As, and other metals in water, sediment, and biota from Phayao Lake, Northern Thailand, and assessment of dietary exposure

This study was undertaken to determine levels of contamination of toxic metals in water, sediment, and consumed fishery products from Phayao freshwater lake located in northern Thailand, which is a major water resource for drinking water, agriculture, and household use. Concentrations of Mn, As, and other metals were determined in water, sediment,. sh tissues ( Puntius gonionotus) and pond snails ( Filopaludina martensi). Sampling was carried out in 3 periods ( February, May, and August) in 2005. Metal analysis was performed by using inductively coupled plasma mass spectrometer ( ICP- MS). Concentrations of Mn and As in lakewater ranged from 40 - 382 and 0.68 - 8.79 mu g L-1 whereas the USEPA ( Mn) and WHO ( As) guidelines for drinking water are 50 and 10 mu g L-1, respectively. Concentrations of some metals ( Al, Cr, Mn, and Fe) in water were found to be higher in the area where water. owed into the lake from a small river than in other areas. The highest metal concentrations were found in the period of the dry season ( May 2005). Among different sampling sites, the patterns of metal accumulations were different. Estimated fishery product consumption from the lake was calculated and the results indicated that the concentrations of metals in these products were lower than the recommended average daily dietary intake. Therefore, the consumption of. sh and pond snail from this water resource may not pose a risk of metal toxicity. However, monitoring of the levels of Mn and As in lakewater should be carried out routinely so that appropriate prevention of contamination from these toxic metals can be implemented.