Immobilization of cadmium and lead in contaminated paddy field using inorganic and organic additives

Heavy metal contamination of agricultural soils has posed a risk to environment and human health. The present study was conducted to assess the effectiveness of soil amendments for reducing cadmium (Cd) and lead (Pb) uptake by rice (Oryza sativa L) in a contaminated field. The soil amendments used include lime, DaSan Yuan (DASY), DiKang No.1 (DEK1), biochar, Fe-biochar, Yirang, phosphorus fertilizer, (Green Stabilizing Agent) GSA-1, GSA-2, GSA-3, and GSA-4, applied at 1% rate in a field experiment. The results exposed that GSA-4 treatment showed best effects on reducing Cd and Pb phytoavailability in soil and uptake by early rice. Linear increase in pH (i.e. 5.69 to 6.75) was recorded in GSA-4 amended soil from sowing to the 3rd month of growth season. GSA-4 decreased DTPA extractable contents of cadmium (Cd) from 0.324 to 0.136 mg kg^-1 soil and lead (Pb) from 53.21 to 24.68 mg kg^-1 soil at 90 days of amendment. Treatment with GSA-4 improved rice growth (56%) and grains yield (42%). The enhancement effects on grain yield may be result from the positive effects of GSA-4 application on increasing photosynthesis (116%) and transpiration rate (152%) as compared to the control. Significant reduction in Cd and Pb uptake in shoot (42% and 44%) and in grains (77 and 88%), was observed, respectively in GSA-4 treatment as compared with the control. Moreover, negative correlation was recorded between DTPA extractable Cd/Pb and soil pH that directly depended on applied amendments. In short, use of combined amendment (GSA-4) was more effective for immobilizing heavy metals in contaminated paddy field, and secures rice safe production, as compared other tested amendment products.