Bioavailability of Nickel in Polluted Soil Amended with Organic Amendments Under Two Different Moisture Regimes

Nickel (Ni) is an important heavy metal, and pollution by Ni has gained importance due to the greater understanding of its persistence and toxicity in the ecosystems. Indiscriminate disposal of various industrial effluents (electroplating, chemical manufacturing etc) resulted in a severe contamination of soil and water ecosystem. In the current study the effect of organic amendments like farm yard manure (FYM), poultry manure, pressmud and biochar on the speciation of Ni in contaminated soil was studied under two different moisture regimes. The results showed that the moisture conditions and organic amendments significantly affected the soil chemical properties like soil pH, organic carbon and thereby it affected the mobility and bioavailability of Ni in soil. Biochar significantly reduced the bioavailable fractions of Ni due to the high CEC and surface area by which it facilitates higher adsorption rate of Ni whereas poultry manure and pressmud compost increased the bioavailability of Ni due to the soluble fractions of organic matter and production of organic acids during decomposition. The organic acids reduced the soil pH which in turn increasedthe bioavailability of Ni. Based on the mobilization or immobilization of Ni, the organic amendments could be used for reclamation of Ni contaminated soil.