Biochar in Co-Contaminated Soil Manipulates Arsenic Solubility and Microbiological Community Structure, and Promotes Organochlorine Degradation

• Published in: PloS one Vol. 10; no. 4; p. e0125393
• Main Authors: Gregory, Samuel J., Anderson, Christopher W. N., Camps-Arbestain, Marta, Biggs, Patrick J., Ganley, Austen R. D., O’Sullivan, Justin M., McManus, Michael T.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29.04.2015; Public Library of Science (PLoS)
• Subjects: Arsenic; Arsenic - chemistry; Arsenic - toxicity; Bacteria; Biodegradation; Biodegradation, Environmental; Biological activity; Charcoal; Charcoal - pharmacology; Chryseobacterium - chemistry; Chryseobacterium - isolation & purification; Communities; Community structure; Contaminants; DDE; DDT; Degradation; Environmental degradation; Hexachlorocyclohexane; Hydrocarbons; Incubation; Isomers; Lindane; Lindane - chemistry; Lindane - toxicity; Microbial activity; Natural attenuation; Nitrous oxide; Organic compounds; Organochlorine compounds; Ovis aries; Reduction; Sediment pollution; Sheep; Soil amendment; Soil contamination; Soil investigations; Soil Microbiology; Soil microorganisms; Soil Pollutants - chemistry; Soil Pollutants - toxicity; Soil pollution; Solubility; Willow
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0125393

We examined the effect of biochar on the water-soluble arsenic (As) concentration and the extent of organochlorine degradation in a co-contaminated historic sheep-dip soil during a 180-d glasshouse incubation experiment. Soil microbial activity, bacterial community and structure diversity were also investigated. Biochar made from willow feedstock (Salix sp) was pyrolysed at 350 or 550°C and added to soil at rates of 10 g kg-1 and 20 g kg-1 (representing 30 t ha-1 and 60 t ha-1). The isomers of hexachlorocyclohexane (HCH) alpha-HCH and gamma-HCH (lindane), underwent 10-fold and 4-fold reductions in concentration as a function of biochar treatment. Biochar also resulted in a significant reduction in soil DDT levels (P < 0.01), and increased the DDE:DDT ratio. Soil microbial activity was significantly increased (P < 0.01) under all biochar treatments after 60 days of treatment compared to the control. 16S amplicon sequencing revealed that biochar-amended soil contained more members of the Chryseobacterium, Flavobacterium, Dyadobacter and Pseudomonadaceae which are known bioremediators of hydrocarbons. We hypothesise that a recorded short-term reduction in the soluble As concentration due to biochar amendment allowed native soil microbial communities to overcome As-related stress. We propose that increased microbiological activity (dehydrogenase activity) due to biochar amendment was responsible for enhanced degradation of organochlorines in the soil. Biochar therefore partially overcame the co-contaminant effect of As, allowing for enhanced natural attenuation of organochlorines in soil.