Abstract: Arsenic (As) pollution in soil has become a serious environmental issue in China. Soil washing is an effective way to remediate soil As pollution. In this paper, we selected three As contaminated soils and two environmentally friendly washing regents (KH2PO4 and oxalic acid) to explore the effectiveness of different washing regents on As contaminated soils. We then conducted two in vitro experiments (by the physiologically based extraction test (PBET) and in vitro gastrointestinal (IVG) methods) to explore soil As bioaccessibility. The results showed that both KH2PO4 and oxalic acid had various soil As removal capacities, and oxalic acid had a higher As removal rate of 54.3% on average. The soil As bioaccessibility determined by PBET was higher than that by the IVG method, and higher after KH2PO4 than oxalic washing. Therefore, compared with oxalic acid, KH2PO4 washing may increase human health risk from As contaminated soil. Our study showed that different in vitro methods can yield different assessments of different washing regents. Therefore, a conservative in vitro method should be selected for each washing regent to evaluate the bioaccessibility of soil As and its associated health risks from washing.

Key words: arsenic contaminated soil, KH2PO4 and oxalic acid washing, bioaccessibility, health risk