Effect of pyrolysis temperature on potential toxicity of biochar if applied to the environment

Honghong Lyu; Yuhe He; Jingchun Tang; Markus Hecker; Qinglong Liu; Paul D Jones; Garry Codling; John P Giesy

doi:10.1016/j.envpol.2016.08.014

Effect of pyrolysis temperature on potential toxicity of biochar if applied to the environment

Environ Pollut. 2016 Nov:218:1-7. doi: 10.1016/j.envpol.2016.08.014. Epub 2016 Aug 15.

Authors

Honghong Lyu¹, Yuhe He², Jingchun Tang³, Markus Hecker⁴, Qinglong Liu¹, Paul D Jones⁴, Garry Codling⁴, John P Giesy⁵

Affiliations

¹ 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.
² Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Biological Science, University of Alberta, Edmonton, Alberta, Canada.
³ 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.
⁴ Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
⁵ 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.

PMID: 27537986
DOI: 10.1016/j.envpol.2016.08.014

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 × 10² μg kg^-1) and PCDD/DF (6.1 × 10² pg 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 (TEQ_H4IIE-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 (TEQ_chem) 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 TEQ_H4IIE-luc determined by use of the bioanalytical method, with the H4IIE-luc assay, which measures the total dioxin-like potency of a mixtures. The ratio of TEQ_chem/TEQ_H4IIE-luc was 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.

Keywords: Biochar; H4IIE-luc; Microtox; PAHs; PCDD/DF.

MeSH terms

Animals
Biological Assay / methods
Cell Line, Tumor
Charcoal / chemistry*
Dibenzofurans, Polychlorinated / analysis*
Dibenzofurans, Polychlorinated / toxicity
Environmental Pollutants / analysis*
Environmental Pollutants / toxicity
Hot Temperature*
Polychlorinated Dibenzodioxins / analysis*
Polychlorinated Dibenzodioxins / toxicity
Polycyclic Aromatic Hydrocarbons / analysis*
Rats
Receptors, Aryl Hydrocarbon / agonists
Receptors, Aryl Hydrocarbon / metabolism
Technology / methods

Substances

Dibenzofurans, Polychlorinated
Environmental Pollutants
Polychlorinated Dibenzodioxins
Polycyclic Aromatic Hydrocarbons
Receptors, Aryl Hydrocarbon
biochar
Charcoal