title: Heavy metal-immobilizing organoclay facilitates polycyclic aromatic hydrocarbon biodegradation in mixed-contaminated soil.
abstract: Soils contaminated with a mixture of heavy metals and polycyclic aromatic hydrocarbons (PAHs) pose toxic metal stress to native PAH-degrading microorganisms. Adsorbents such as clay and modified clay minerals can bind the metal and reduce its toxicity to microorganisms. However, in a mixed-contaminated soil, an adsorption process more specific to the metals without affecting the bioavailability of PAHs is desired for effective degradation. Furthermore, the adsorbent should enhance the viability of PAH-degrading microorganisms. A metal-immobilizing organoclay (Arquad(®) 2HT-75-bentonite treated with palmitic acid) (MIOC) able to reduce metal (cadmium (Cd)) toxicity and enhance PAH (phenanthrene) biodegradation was developed and characterized in this study. The MIOC differed considerably from the parent clay in terms of its ability to reduce metal toxicity (MIOC>unmodified bentonite>Arquad-bentonite). The MIOC variably increased the microbial count (10-43%) as well as activities (respiration 3-44%; enzymatic activities up to 68%), and simultaneously maintained phenanthrene in bioavailable form in a Cd-phenanthrene mixed-contaminated soil over a 21-day incubation period. This study may lead to a new MIOC-assisted bioremediation technique for PAHs in mixed-contaminated soils.
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, P.O. Box 486, Salisbury, SA 5106, Australia.
authors.forename: Bhabananda
authors.initials: B
authors.lastname: Biswas
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, P.O. Box 486, Salisbury, SA 5106, Australia.
authors.forename: Binoy
authors.initials: B
authors.lastname: Sarkar
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Division of Soil Biology, Indian Institute of Soil Science, Bhopal, Madhya Pradesh, India.
authors.forename: Asit
authors.initials: A
authors.lastname: Mandal
authors.affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, SA 5095, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, P.O. Box 486, Salisbury, SA 5106, Australia.
authors.forename: Ravi
authors.initials: R
authors.lastname: Naidu
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D058491:Bacterial Load; D001546:Bentonite; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000737:chemistry; D000077215:Clay; D000075322:Heavy Metal Poisoning; D019216:Metals, Heavy / Q000302:isolation & purification*; D010088:Oxidoreductases / Q000032:analysis; D019308:Palmitic Acid / Q000737:chemistry; D010616:Phenanthrenes / Q000032:analysis; D011041:Poisoning; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000302:isolation & purification*; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D019216:Metals, Heavy; D010616:Phenanthrenes; D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants; D002104:Cadmium; D001546:Bentonite; D019308:Palmitic Acid; D010088:Oxidoreductases; D000077215:Clay
keywords: Bioavailability; Metal-immobilizing organoclay; Microbial activities; Mixed contaminants; PAH-biodegradation