Abstract
Ponds are abundantly found in suburban area of Hanoi City, Viet Nam, where groundwater pollution by arsenic is a major problem. We investigated water quality of pond waters, pore waters of pond sediments, and chemical property of pond sediments in four ponds in Hanoi suburbs in order to estimate the influence of pond seepage on groundwater pollution by arsenic. While pond waters had low arsenic levels (<10 μg/L), pore waters had high levels of arsenic (maximum: 134 μg/L), indicating the dissolution of arsenic from arsenic- and organic matter-rich pond sediments. It was also suggested that pond sediments not only released arsenic but also adsorbed arsenic from the dissolved phase, mitigating groundwater pollution by arsenic. Analysis of chloride and stable isotopes (δ18O, δD) indicated that seepage from ponds was a significant source of recharge of groundwater which was polluted by high levels of arsenic (median: 27 and 43 μg/L).
