Biochar in co-contaminated soil manipulates arsenic solubility and microbiological community structure, and promotes organochlorine degradation.
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.
New Zealand Biochar Research Centre, Massey University, Palmerston North, New Zealand.
Samuel J
SJ
Gregory
Soil and Earth Sciences, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
Christopher W N
CW
Anderson
New Zealand Biochar Research Centre, Massey University, Palmerston North, New Zealand.
Marta
M
Camps-Arbestain
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Patrick J
PJ
Biggs
Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand.
Austen R D
AR
Ganley
Liggins Institute, University of Auckland, Auckland, New Zealand.
Justin M
JM
O'Sullivan
Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
Michael T
MT
McManus
D001151:Arsenic / Q000737:chemistry* / Q000633:toxicity; D001673:Biodegradation, Environmental; D002606:Charcoal / Q000494:pharmacology*; D045247:Chryseobacterium / Q000737:chemistry / Q000302:isolation & purification; D001556:Hexachlorocyclohexane / Q000737:chemistry / Q000633:toxicity; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry / Q000633:toxicity; D012995:Solubility
D012989:Soil Pollutants; C540010:biochar; D002606:Charcoal; D001556:Hexachlorocyclohexane; D001151:Arsenic