Arsenic in the water-soil-plant system and the potential health risks in the coastal part of Chianan Plain, Southwestern Taiwan

The present study investigates the bioavailability, soil to plant transfer and health risks of arsenic (As) in the coastal part of Chianan Plain in southwestern Taiwan. Groundwater used for irrigation, surface soils from agricultural lands and locally grown foodstuffs were collected from eight locations and analyzed for As to assess the risks associated with consuming these items. The concentration of As in groundwater ranged from 13.8 to 881μg/L, whereas surface soil showed total As content in the range of 7.92-12.7mg/kg. The available As content in surface soil accounted for 0.06-6.71% of the total As content, and was significantly correlated with it (R²=0.65, p<0.05). Among the leachable fraction, the organic matter (3.23-54.8%) and exchangeable portions of oxides (6.03-38.4%) appear to be the major binding phases of As. The average As content in fourteen studied crops and vegetables varied from 10.3 to 151μg/kg with maximum in mustard and minimum in radish. All the plants showed considerably higher As content (21.5±3.64-262±36.2μg/kg) in their roots compared to the edible parts (9.15±1.44-75.8±22.9μg/kg). The bioaccumulation factor (BAF) based on total As (ranging from 0.0009 to 0.144) and available As in soil (ranging from 0.039 to 0.571) indicate that mustard, rice, amaranth and spinach are the highest accumulators of As. Although the health risk index (HRI) of the studied crops and vegetables ranged from only 0.0068-0.454, with the maximum in rice, the combined HRI indicates an alarming value of 0.88. Therefore, the possible health risks due to long-term consumption of rice and other As-rich foodstuffs could be overcome by controlling the contamination pathways in the water-soil-plant system.