Data Represent The Mean Of Triplicate Measurements

Data represent the mean of triplicate measurements  ± standard deviation (SD). Data with asterisk (*) mean that bioaccessibility at this time point was significantly different from that measured at previous time point (**, p0.05). When soils progressed from the gastric phase to intestinal phase, bioaccessibility of As, Cd and Pb in soils spiked with binary mixtures of As, Cd and Pb were not affected by each other. For example, intestinal bioaccessibility of Cd in KBA soil measured at 7 days (Table 4.3) was 22 ±1.9 %, which did not differ significantly (p0.05) from that (22 ±1.7 %) in soil spiked with both Cd and As (Table 4.5). Liang et al. (2014) found that when As (40 mg kg-1) and Pb (150 mg kg-1) were spiked together in soils which†¦show more content†¦Also, since As, Cd and Pb solutions were added into soils sequentially with 24 hours (spike time interval) apart rather than concurrently in one mixed-solution, insoluble compounds such as Cd/Pb arsenate were less li kely to be formed in soils due to the rapid sorption of metals/metalloid from solution to soil phase (Bradl, 2004). However, when Pb and As were added to Cd-spiked soil one after another, intestinal bioaccessibility of Cd in KBA and TAA soils increased relative to soils spiked with single Cd at the early stage of aging (data in Table 4.5 marked with *). In contrast, bioaccessibility of As and Pb were not influenced by the presence of Cd. Compared to binary mixtures of As, Cd and Pb, the co-existence of As, Cd and Pb in the same soil sample may lead to competitive sorption on soils due to the increased loading of metals/metalloid. Prior studies have noted that Pb was absorbed in preference to Cd thus increasing the observed solubility of Cd (Serrano et al., 2005; Appel et al., 2008). In this study, this preference was reflected on the observation that bioaccessibility of Pb in four types of soils was stable after 7 days aging, which indicates fast reaction between Pb and soil components. Besides, strong affinity of As to organic carbon, Fe oxide and Al oxide has been extensively reported (Solaiman et al., 2009; Komarek et al., 2013). Therefore, there was a high