Risk assessment of arsenic from contaminated soils to shallow groundwater in Ong Phra Sub-District, Suphan Buri Province, Thailand

According to the sequential extraction result, the concentrations of total As in 39 soil samples ranges from 4.8 to 1070.4 mg/kg. The highest As concentration in shallow groundwater was found at well number 3, located within <0.5 km. downstream from the old tin mine. The Index of DRASTIC groundwater vulnerability, is in the range of 59-147, which is categorized into three vulnerability zones as follows: low (<100), moderate (100-130) and high (>130). The high vulnerability area, found along the waterway, is approximately 35 km2 (18.65% of the study area). Interestingly, the DRASTIC index of the old tin mine is indicated as the zone of moderate and high vulnerability. The findings in this study reveal that the integration of the DRASTIC risk map with CF can well elucidate As contaminated in shallow groundwater.