Application of DGT/DIFS to assess bioavailable Cd to maize and its release in agricultural soils

Highlights: • Millions of hectares of agricultural land are seriously enriched by Cd in China. • Due to the high mobility of Cd, it can easily enter plant tissues. • There are few studies on the bioavailability of Cd in maize in Tianjin. • The DGT has been shown as a reliable means of assessing metal bioavailability. • The DGT and DIFS model predicted labile metals release from the agricultural lands. Tianjin, as an important maize production region in China, has a long history of sewage irrigation resulting in the soil cadmium (Cd) contamination. In this study, single extractions of CaCl₂ and HNO₃, BCR sequential extraction and the diffusive gradients in thin films technique (DGT) were used to measure the bioavailable Cd content in soils. The Cd content in soil samples all exceeded the background values, with 14.3% and 33.3% of sites in the Baodi District (BDD) and Jinghai District (JHD) exceeding the risk control values, respectively. The average content of Cd in maize samples is lower than the pollution control values, which may be related to the higher pH (8.53) and organic matter (OM) content (15.01 g kg⁻¹) in soils. Bioavailable Cd measured by DGT correlated well with Cd in maize grains (R² =0.92). The DGT and DIFS model predicted the metals release from the agricultural lands, the total concentration of Cd in soil was relatively low, but the labile Cd in the soils has adequate metal release capability. This study shows that DGT is efficient in predicting Cd accumulation in grains from contaminated soils.