Bioavailability of antimony and arsenic in a flowering cabbage-soil system: Controlling factors and interactive effect.

Soil contamination with antimony (Sb) and arsenic (As) has become a well-recognized environmental and human health issue. Consumption of vegetables, especially leafy vegetables, is one of the most important sources of Sb and As exposure in humans. Accordingly, it is necessary to understand the behaviors of Sb and As in the vegetable-soil system. Moreover, although Sb and As are often assumed to have similar biogeochemical behavior, identified differences in the controlling factors affecting mobility and bioavailability of Sb and As in soils need further investigation. In this study, 112 pairs of soil and flowering cabbage samples were collected from typical farmland protection areas and vegetable-producing regions across the Pearl River Delta (PRD), South China. The contamination levels of Sb and As in soils and harvested cabbages across the PRD were investigated. The main factors affecting the mobility and bioavailability of Sb and As in the cabbage-soil system were disentangled using a random forest model. The contamination levels of Sb in the cabbages and soils of the PRD were generally low, but the soils were moderately polluted by As. Increased concentrations of Fe oxides could decrease Sb accumulation in cabbages but increased the mobilization of As in soils to some extent. In contrast, Al oxides contributed strongly to the mobilization of Sb and the immobilization of As. Moreover, an increased sand content promoted the mobility of Sb and As, whereas increased silt and clay contents showed inhibitory effects. The interactions of As and Sb with Fe oxides decreased the mobility of Sb but moderately increased the mobility of As in soils. Overall, the behaviors of Sb and As in the cabbage-soil system under the effect of several important environmental factors showed some differences indicating that these differences should be considered in the remediation of co-contaminated soils.