Heavy Metals Contamination in the Ecosystem of Mae Thang Reservoir in Northern Thailand

Abstract

{O}ne critical concern for {T}hailand 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. {T}he 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. {F}ourteen {TME} have been measured in water column (dissolved phase), fishes, and sediments of the {M}ae {T}hang {R}eservoir (northern {T}hailand) as well as soil and rice grains of irrigated area. {A}nalyses were performed by inductively coupled plasma-mass spectrometer ({ICP}-{MS}). {T}his 2-year study showed that {TME} concentrations in water were lower than standards for irrigation and aquatic life. {H}owever, localized values of {F}e and {M}n were higher than the standard in the bottom of the reservoir in dry season. {TME} in sediments were relatively high compared to pristine lakes. {T}wo species of fish were contaminated in {A}s and {N}i. {S}oils exceeded standard values for {C}r, {N}i, and {C}u, while rice grains showed contamination in {N}i that indicated a transfer between soil and rice grain. {T}he 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. {A}ccumulation of {TME} in soils of paddy field due to the use of pesticides and fertilizer may increase contamination of rice in the long term.