Investigating the phytoavailability of trace elements in contaminated agricultural soils and health risks via consumption of water spinach grown under field conditions in Zhuzhou, China

In this study, the phytoavailability of trace elements from contaminated agricultural soils to water spinach grown under field conditions in Zhuzhou, China was investigated using three single extraction methods: CaCl2, HAc, and acid ammonium acetate-EDTA (AEDTA) compared with a strong acid digestion method. The soils are primarily contaminated by Cd (4.16 ± 5.98 mg kg−1) and Pb (152 ± 160 mg kg−1), followed by Zn (403 ± 443 mg kg−1), Cu (60.5 ± 29.4 mg kg−1) and As (39.1 ± 36.0 mg kg−1). The main pollutants in water spinach grown in this area are Pb and Cd. The estimated dietary intakes of Cd, Pb and As in some sampling sites were higher than the tolerable limits, indicating that the potential health risks from exposure to these three elements through consumption of water spinach need more attention. Importantly, water spinach has an increased propensity for Cd phytoextraction in contaminated soils with an average bioaccumulation factor of higher than 1, whereas Pb in the edible parts of water spinach is probably present from atmospheric deposition. Statistical analysis indicated that more aggressive extraction procedures (HAc or AEDTA) were better able to predict the phytoavailability of trace elements. Moreover, the phytoavailability of Pb, Cd and Zn could also be well predicted by their total concentrations in soils. Although the trace elements content in water spinach could mostly be explained by total or extractable concentrations, the regression predictions were further improved by the incorporation of soil properties.