ARS | Publication request: Reversible and irreversible sorption of agrochemicals in biochar amended soils: synergistic effects of heavy metals

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 26, 2011
Publication Date: N/A

Technical Abstract: Soil amendment of biochar products from thermochemical waste-to-energy conversion (slow/fast pyrolysis and gasification) of biomass has received considerable interests for both contaminated and agricultural sites. Recalcitrant nature of biochar manifests in their decade-long effectiveness in soil along with the carbon sequestration potential. While biochars produced from plant and animal wastes are known to effectively sorb organic and inorganic contaminants, systematic studies are lacking in desorption of sorbed contaminants that will constrain the effectiveness of remediation strategies. In this study, a series of agricultural waste-derived biochars and activated carbons were examined for their ability to irreversibly stabilize inorganic (heavy metals) and organic (agrochemicals) contaminants in soils representing a wide range of pH, CEC, TOC, and the contamination level. Biochars were first characterized for the yield, moisture, ash, volatile matter, and fixed carbon contents, elemental composition (CHNSO), BET surface area, pH, pHpzc, surface charge, and by ATR-FTIR and 1H NMR. Biochar amended soils were exposed to a series of desorption conditions to address leaching by rainfall events, toxicity characteristics, and in vitro bioaccessibility. Both organophosphorus (malathion, parathion, and diazinon) and triazine pesticides showed nonlinear sorption isotherms on biochar and soil matrices. Increasingly irreversible nature of sorption for organophosphorus pesticides at higher biochar loading resulted in a greater retention of heavy metals in the contaminated soil, suggesting synergistic sorption of organic and inorganic contaminants. Based on the experimental findings, recommendations are given on the use of a suite of biochars to target specific functions in soil.