Influence of Various Passivators for Nickel Immobilization in Contaminated Soil of China.

In agricultural field, nickel (Ni) contamination has become a serious concern/threat all over the world due to its hazardous effects on ecosystem and food chain. An incubation study was conducted to investigate the simultaneous efficiency of rice straw (RS) and its derived biochar (BI), calcium carbonate (calcite), zeolite (ZE), and triple superphosphate (TSP) on the stabilization of Ni in contaminated soil. Various chemical extraction techniques, including the sequential extraction (BCR), leaching toxicity (TCLP) test, and single CaCl2 extraction, were performed. The results revealed that greater reduction in acid-soluble fractions of Ni was observed by 45%, 65.1%, 42.1%, 55.7%, and 33.9% with RS, BI, ZE, calcite at 2%, and TSP 0.5% application rate, respectively. Similarly, TCLP and CaCl2-extractable Ni were significantly decreased by 49.8% and 97.5% with 2% BI application rate, respectively. The soil pH, EC, and organic matter were significantly improved with the incorporation of RS, BI, ZE, TSP, and calcite amendments. Overall, among all the amendments, the incorporation of BI and calcite was considered to be the best option for Ni immobilization and thereby reducing its mobility in Ni contaminated soil. These findings suggest that RS biochar and calcite can be used as Ni stabilizers in contaminated agricultural soils. [ABSTRACT FROM AUTHOR]