title: Differential effect of biochar upon reduction-induced mobility and bioavailability of arsenate and chromate.
abstract: Heavy metals such as chromium (Cr) and arsenic (As) occur in ionic form in soil, with chromate [Cr(VI)] and arsenate As(V) being the most pre-dominant forms. The application of biochar to Cr(VI) and As(V) spiked and field contaminated soils was evaluated on the reduction processes [(Cr(VI) to Cr(III)] and [As(V) to As(III))], and subsequent mobility and bioavailability of both As(V) and Cr(VI). The assays used in this study included leaching, soil microbial activity and XPS techniques. The reduction rate of As(V) was lower than that of Cr(VI) with and without biochar addition, however, supplementation with biochar enhanced the reduction process of As(V). Leaching experiments indicated Cr(VI) was more mobile than As(V). Addition of biochar reversed the effect by reducing the mobility of Cr and increasing that of As. The presence of Cr and As in both spiked and contaminated soils reduced microbial activity, but with the addition of biochar to these soils, the microbial activity increased in the Cr(VI) contaminated soils, while it was further decreased with As(V) contaminated soils. The addition of biochar was effective in mitigating Cr toxicity by reducing Cr(VI) to Cr(III). In contrast, the conversion process of As(V) to As(III) hastened by biochar was not favourable, as As(III) is more toxic in soils. Overall, the presence of functional groups on biochar promotes reduction by providing the electrons required for reduction processes to occur as determined by XPS data.
authors.affiliation: Southern Cross GeoScience, Southern Cross University, PO Box: 157, Lismore 2480, NSW, Australia.
authors.forename: Girish
authors.initials: G
authors.lastname: Choppala
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes 5095, SA, Australia; Global Centre for Environmental Remediation (GCER), University of Newcastle, Callaghan Campus 2308, NSW, Australia. Electronic address: Nanthi.Bolan@newcastle.edu.au.
authors.forename: Nanthi
authors.initials: N
authors.lastname: Bolan
authors.affiliation: Chemical Safety Division, Department of Agro-Food Safety, National Academy of Agricultural Science, Wanju-gun, Jeollabuk-do, 55365, Republic of Korea.
authors.forename: Anitha
authors.initials: A
authors.lastname: Kunhikrishnan
authors.affiliation: Southern Cross GeoScience, Southern Cross University, PO Box: 157, Lismore 2480, NSW, Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Bush
mesh_terms: D001149:Arsenates / Q000378:metabolism* / Q000633:toxicity; D001682:Biological Availability; D002606:Charcoal / Q000737:chemistry*; D002840:Chromates / Q000378:metabolism* / Q000633:toxicity; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism* / Q000633:toxicity
chemical_list: D001149:Arsenates; D002840:Chromates; D012989:Soil Pollutants; C540010:biochar; D002606:Charcoal
keywords: Arsenic and chromium species; Bioavailability; Reduction; Sorption; XPS