Résumé
One critical concern for Thailand reservoirs which are used for irrigated agriculture (mainly paddy rice) and aquaculture is the lack of information on contamination from trace metal element (TME) in waters and biological compartments of the reservoirs. TME are both from natural and anthropogenic origins and may affect the quality of lake waters and food chain. The goal of this study was to evaluate the contamination in TME and study their transfer between the different compartments in and downstream of the reservoir. Fourteen TME have been measured in water column (dissolved phase), fishes, and sediments of the Mae Thang Reservoir (northern Thailand) as well as soil and rice grains of irrigated area. Analyses were performed by inductively coupled plasma-mass spectrometer (ICP-MS). This 2-year study showed that TME concentrations in water were lower than standards for irrigation and aquatic life. However, localized values of Fe and Mn were higher than the standard in the bottom of the reservoir in dry season. TME in sediments were relatively high compared to pristine lakes. Two species of fish were contaminated in As and Ni. Soils exceeded standard values for Cr, Ni, and Cu, while rice grains showed contamination in Ni that indicated a transfer between soil and rice grain. The accumulation of TME in sediments showed that upstream cultivated areas may have contributed to bring TME in the reservoir. TME concentrations in fishes were thus affected and should be controlled. Accumulation of TME in soils of paddy field due to the use of pesticides and fertilizer may increase contamination of rice in the long term.