Biochar amendment alters the relation between the Pb distribution and biological activities in soil

Abstract

In the present investigation, the impact of biochar amendments on the Pb fractionation pattern and soil enzymatic activities in soil was evaluated. Two spiking concentrations of exogenous Pb, two application rates (2% and 4%) of biochar and three plants such as Withania somnifera, Andrographis paniculata and Bacopa monnieri were taken for the study. Three experiment sets were designed for each plant. Distribution of Pb (in acid soluble, reducible, oxidizable and residual fractions), physicochemical and biological properties (β-glucosidase, acidic and alkaline phosphatases, urease and microbial biomass) of soil were examined. Several chemometric techniques were applied to this huge data to evaluate the association of soil microbial activities with Pb fractionation. The results revealed that biochar amendments altered the fractionation of Pb by shifting from mobile fraction (acid soluble) to immobile fraction (oxidizable and residual). The correlation analysis suggested that this could be attributed to the increase in cation exchange capacity, organic carbon and available phosphorus content in the soil after biochar amendments. The results clearly demonstrated that biochar amendments in Pb-contaminated soil improved the enzymatic activities in the soil. The multidimensional scaling, correlation and sequential equation modeling imply that biochar has a shielding effect on soil microbial activity against Pb stress from each fraction of soil.