title: Effect of pyrolysis temperature on potential toxicity of biochar if applied to the environment.
abstract: Biochars have increasingly been used as adsorbents for organic and inorganic contaminants in soils. However, during the carbonization process of pyrolysis, contaminants, including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dioxins and furans (PCDD/DF) can be generated. In this study, biochars made from sawdust, were prepared at various temperatures ranging from 250 to 700 °C. The Microtox®and rat hepatoma cell line H4IIE-luc assays were used to characterize the general toxic and effects, mediated through the aryl hydrocarbon receptor (AhR), or dioxin-like potencies of organic extracts of biochars. The greatest total concentrations of PAHs (8.6 × 102μg kg-1) and PCDD/DF (6.1 × 102pg g-1) were found in biochar generated at 400 °C and 300 °C, respectively. Results of the H4IIE-luc assay, which gives total concentrations of 2,3,7,8-TCDD equivalents (TEQH4IIE-luc), indicated that total potencies of aryl hydrocarbon receptor (AhR) agonists were in decreasing order: 300 °C > 250 °C > 400 °C > 500 °C > 700 °C. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQchem) calculated as the sum of products of 16 PAHs and 17 PCDD/DF congers multiplied by their respective relative potencies (RePs) was less than that of TEQH4IIE-lucdetermined by use of the bioanalytical method, with the H4IIE-luc assay, which measures the total dioxin-like potency of a mixtures. The ratio of TEQchem/TEQH4IIE-lucwas in the range of 0.7%-3.8%. Thus, a rather small proportion of the AhR-mediated potencies extracted from biochars were identified by instrumental analyses. Results of the Microtox test showed similar tendencies as those of the H4IIE-luc test, and a linear correlation between EC50 of Microtox test and EC20 of H4IIE-luc test was found. The results demonstrated that biochars produced at higher pyrolysis temperatures (>400 °C) were less toxic and had lower potencies of AhR-mediated effects, which may be more suitable for soil application.
authors.affiliation: Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Honghong
authors.initials: H
authors.lastname: Lyu
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Biological Science, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Yuhe
authors.initials: Y
authors.lastname: He
authors.affiliation: Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China. Electronic address: tangjch@nankai.edu.cn.
authors.forename: Jingchun
authors.initials: J
authors.lastname: Tang
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Markus
authors.initials: M
authors.lastname: Hecker
authors.affiliation: Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Qinglong
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Jones
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: Garry
authors.initials: G
authors.lastname: Codling
authors.affiliation: Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; School of Biological Sciences, University of Hong Kong, Hong Kong, China; State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, China.
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D045744:Cell Line, Tumor; D002606:Charcoal / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated / Q000032:analysis* / Q000633:toxicity; D004785:Environmental Pollutants / Q000032:analysis* / Q000633:toxicity; D006358:Hot Temperature; D000072317:Polychlorinated Dibenzodioxins / Q000032:analysis* / Q000633:toxicity; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis*; D051381:Rats; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists / Q000378:metabolism; D013672:Technology / Q000379:methods
chemical_list: D000072338:Dibenzofurans, Polychlorinated; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D011084:Polycyclic Aromatic Hydrocarbons; D018336:Receptors, Aryl Hydrocarbon; C540010:biochar; D002606:Charcoal
keywords: Biochar; H4IIE-luc; Microtox; PAHs; PCDD/DF