Biochar in co-contaminated soil manipulates arsenic solubility and microbiological community structure, and promotes organochlorine degradation

PLoS One. 2015 Apr 29;10(4):e0125393. doi: 10.1371/journal.pone.0125393. eCollection 2015.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arsenic / chemistry*
  • Arsenic / toxicity
  • Biodegradation, Environmental*
  • Charcoal / pharmacology*
  • Chryseobacterium / chemistry
  • Chryseobacterium / isolation & purification
  • Hexachlorocyclohexane / chemistry
  • Hexachlorocyclohexane / toxicity
  • Soil Microbiology*
  • Soil Pollutants / chemistry
  • Soil Pollutants / toxicity
  • Solubility

Substances

  • Soil Pollutants
  • biochar
  • Charcoal
  • Hexachlorocyclohexane
  • Arsenic

Grants and funding

Metagenomics work was funded by Massey University Strategic Innovation Fund (SIF) grant (to JMO), with support from the New Zealand Microbiology Society and the Maurice Wilkins Centre, and from commercial sources: Custom Science, Roche, New Zealand Genomics Limited and KapaBiosystems. The first author gratefully acknowledges the Ministry of Science and Innovation (New Zealand) for the award of a Ti Tipu Putaiao Fellowshop (PhD scholarship). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Acceptance of funding from the named sources does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.