Pristine and iron-engineered animal- and plant-derived biochars enhanced bacterial abundance and immobilized arsenic and lead in a contaminated soil

In this study, typical animal- and plant-derived biochars derived from pig carcass (PB) and green waste (GWB), and their iron-engineered products (Fe-PB and Fe-GWB) were added at the dose of 3% (w/w) to an acidic (pH 5.8) soil, and incubated to test their efficacy in improving soil quality and immobilizing arsenic (As 141.3 mg kg(-1))and lead (Pb = 736.2 mg kg(-1)). Soil properties, microbial activities, and the geochemical fractions and potential availabilities of As and Pb were determined in he non-treated (control) and biochar-treated soil. Modification of PB (pH = 10.6) and GWB (pH = 9.3) with Fe caused a decrease in their pH to 44 and 3.4, respectively. The application of PB and GWB significantly increased soil pH, while Fe-PB and Fe-GWB decreased soil pH, as compared to the control. Application of Fe-GWB and Fe-PB decreased the NH4H2PO4-extractable As by 32.8 and 35.9%, which was more effective than addition of GWB and PB. However, PB and GWB were more effective than Fe-PB and Fe-GWB in Pb immobilization. Compared to the control, the DTPA-extractable Pb decreased by 20.6 and 21.7%, respectively, following PB and GWB application. Both biochars, particularly PB significantly increased the 165 rRNA bacterial gene copy numbers, indicating that biochar amendments enhanced the bacterial abundance, implying an alleviation of As and Pb bio-toxicity to soil bacteria. The results demonstrated that pristine pig carcass and green waste biochars were more effective in immobilizing Pb, while their Fe-engineered biochars were more effective in As immobilization in co-contaminated soils. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study demonstrated that iron-engineered biochars were more effective in immobilizing arsenic, while original animal- and plant-derived biochars were better at immobilizing lead in soil. Biochar amendments increased bacterial abundance in soil, potentially alleviating the bio-toxicity of arsenic and lead to soil bacteria.