Biodegradation of hydrocarbons in soil and water

Abstract: Biodegradation of aliphatic and polycyclic aromatichydrocarbons was studied in soil and liquid cultures attemperatures ranging from -5 º C to 20 º C undervarious aerobic or anaerobic, nitrate reducing, conditions. Twocontaminated soils were used in the studies. One contaminatedwith weathered diesel fuel from the Arctic region in northernCanada and one weathered PAH/creosote contaminated soil from anold gaswork site in Stockholm, Sweden. Solid phasemicroextraction (SPME) was used to monitor both degradation andthe analysis of metabolites with gas chromatography and massspectrometry.Aerobic degradation of diesel fuel hydrocarbons was possiblein both uncontaminated potting soil at 20 º C andcontaminated Arctic soil at 7 º C by indigenousmicroorganisms. The Arctic soil contained cold adaptedmicroorganisms and approximately 1500 mg total petroleumhydrocarbons per kg was removed during 60 days of treatment inboth on-site biopiles and in microcosm treatments. Inoculationwith a jet A1 fuel grown cold adapted consortium did notenhance hydrocarbon degradation in any of the treatments.Continuos freezing and thawing, temperature cycling between 7º C and -5 º C every 24 hours did not inhibit theoverall total degradation during 50 days of treatment.Ribosomal intergenic spacer length polymorphism analysis(RIS-LP) showed that the microbial population changed slightlyin the freeze-thaw treated soil compared to soils kept at 7º C.Degradation of polycyclic aromatic hydrocarbons with up tothree aromatic rings was observed at 20 º C under variousnutrient additions and mechanical mixing in weathered creosotecontaminated soil. The mixing showed higher effect ondegradation than the nutrient additions. The compounds in theweathered soil was sorbed to soil particles and unavailable tothe microorganisms. Pure isolates from the PAH-contaminatedcould degrade three ring PAHs within 30 days in liquid culturesat 20 º C and it was shown that addition of salicylic acidstimulated PAH degradation whereas catechol did not. PAHdegrading enrichment cultures were produced from various soils,and it was shown that PAHs with up to four aromatic rings couldbe degraded at low temperature and under nitrate reducingconditions was accumulated in most systems during PAHdegradation. 9-Fluorenone accumulated to higher concentrationsin uncontaminated soils than in soil exposed to PAHs.A novel type of growth on pyrene crystals in liquid cultureswas also studied. The obtained biofilm was extracted for DNA,and cloning and partial 16S-rDNA analysis showed that the threemost abundant clones matchedPolaromonassp.,Sphingomonassp. andAlcaligenessp.Keywords:Solid Phase Microextraction, SPME,biodegradation, bioremediation, bioavailability, monitoring,Volatile Organic Compounds (VOC), Screening, headspacesampling, polycyclic aromatic hydrocarbons, PAHs, aliphatichydrocarbons, total petroleum hydrocarbons, TPH, biofilmproduction,Pseudomonassp. 9-fluorenone.