Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2010
Publication Date: 8/1/2010
Citation: Uchimiya, M., Lima, I.M., Klasson, K.T., Wartelle, L.H. 2010. Contaminant Immobilization and Nutrient Release by Biochar Soil Amendment: Roles of Natural Organic Matter. Chemosphere. 80 (8):935-940.
Interpretive Summary: Nutshells and manure are the major agricultural byproducts that can be thermally converted to biochars and activated carbons for use in a variety of agricultural and environmental remediation purposes. In this study, the effects of nutshell and manure-derived biochars and activated carbons on soil properties (pH, immobilization of contaminants, and release of nutrients) were investigated. Our results suggest that pre- and post-treatment of biochars and activated carbons strongly impact their ability to sequester toxic heavy metals and release essential plant nutrients in soil. In addition, soil organic matter and intrinsic lability of metal contaminants influence the effectiveness of amended carbons as soil fertilizer and conditioner.
Technical Abstract: Contamination of soil interstitial waters by labile heavy metals such as CuII, CdII, and NiII is of worldwide concern. Carbonaceous materials such as char and activated carbon have received considerable attention in recent years as soil amendment for both sequestering heavy metal contaminants and releasing essential nutrients like sulfur. Information is currently lacking on how aging impacts the integrity of biochars as soil amendment for both agricultural and environmental remediation purposes. Major contributors to biochar aging in soils are: sorption of environmental constituents, especially natural organic matter (NOM), and oxidation. To investigate the impact of NOM and organic fractions of chars, we employed broiler litter-derived chars and steam activated carbons that underwent varying degrees of carbonization, in the presence and absence of NOM having known carboxyl contents. For aging by oxidation, we employed phosphoric acid activated carbons that underwent varying degrees of oxidation during activation. Our results suggest that the organic fractions of biochars, and NOM having high carboxyl contents can mobilize CuII retained by alkaline soil. Base treatment of broiler litter-derived char formed at low pyrolysis temperature (350 oC) improved the immobilization of all heavy metals investigated, and the extent of immobilization was similar to, or slightly greater than pecan shell-derived phosphoric acid activated carbons. Portions of total sulfur were released in soluble form in soil amended with broiler litter-derived carbons, but not pecan shell-derived phosphoric acid activated carbons.