title: Mild acid and alkali treated clay minerals enhance bioremediation of polycyclic aromatic hydrocarbons in long-term contaminated soil: A14C-tracer study.
abstract: Bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils requires a higher microbial viability and an increased PAH bioavailability. The clay/modified clay-modulated bacterial degradation could deliver a more efficient removal of PAHs in soils depending on the bioavailability of the compounds. In this study, we modified clay minerals (smectite and palygorskite) with mild acid (HCl) and alkali (NaOH) treatments (0.5-3 M), which increased the surface area and pore volume of the products, and removed the impurities without collapsing the crystalline structure of clay minerals. In soil incubation studies, supplements with the clay products increased bacterial growth in the order: 0.5 M HCl ≥ unmodified ≥ 0.5 M NaOH ≥ 3 M NaOH ≥ 3 M HCl for smectite, and 0.5 M HCl ≥ 3 M NaOH ≥ 0.5 M NaOH ≥ 3 M HCl ≥ unmodified for palygorskite. A14C-tracing study showed that the mild acid/alkali-treated clay products increased the PAH biodegradation (5-8%) in the order of 0.5 M HCl ≥ unmodified > 3 M NaOH ≥ 0.5 M NaOH for smectite, and 0.5 M HCl > 0.5 M NaOH ≥ unmodified ≥ 3 M NaOH for palygorskite. The biodegradation was correlated (r = 0.81) with the bioavailable fraction of PAHs and microbial growth as affected particularly by the 0.5 M HCl and 0.5 M NaOH-treated clay minerals. These results could be pivotal in developing a clay-modulated bioremediation technology for cleaning up PAH-contaminated soils and sediments in the field.
authors.affiliation: Future Industries Institute, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, ACT Building, The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: B.Nanda.Biswas@gmail.com.
authors.forename: Bhabananda
authors.initials: B
authors.lastname: Biswas
authors.affiliation: Future Industries Institute, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Department of Geological Sciences, Indiana University, Bloomington, IN 47405, USA. Electronic address: Binoy.Sarkar@unisa.edu.au.
authors.forename: Binoy
authors.initials: B
authors.lastname: Sarkar
authors.affiliation: Future Industries Institute, University of South Australia, Mawson Lakes Campus, SA 5095, Australia.
authors.forename: Ruhaida
authors.initials: R
authors.lastname: Rusmin
authors.affiliation: Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, ACT Building, The University of Newcastle, Callaghan, NSW 2308, Australia; Global Centre for Environmental Remediation (GCER), Faculty of Science and Information Technology, The University of Newcastle, Callaghan, NSW 2308, Australia. Electronic address: Ravi.Naidu@newcastle.edu.au.
authors.forename: Ravi
authors.initials: R
authors.lastname: Naidu
mesh_terms: D000143:Acids / Q000737:chemistry*; D000468:Alkalies / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D001673:Biodegradation, Environmental; D000077215:Clay; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*
chemical_list: D000143:Acids; D000468:Alkalies; D000538:Aluminum Silicates; D011084:Polycyclic Aromatic Hydrocarbons; D012987:Soil; D012989:Soil Pollutants; D000077215:Clay
keywords: (14)C-tracing; Acid/alkali treatment; Bioavailability; Bioremediation; Clay modification; Polycyclic aromatic hydrocarbons