| Title: | "Multiple lines of evidence to demonstrate vinyl chloride aerobic biodegradation in the vadose zone, and factors controlling rates" |
| Author(s): | Patterson BM; Aravena R; Davis GB; Furness AJ; Bastow TP; Bouchard D; |
| Address: | "CSIRO Land and Water, Floreat, Australia; School of Chemistry and Biochemistry, University of Western Australia, Crawley, Australia. Electronic address: bradley.patterson@csiro.au" |
| DOI: | 10.1016/j.jconhyd.2013.07.008 |
| ISSN/ISBN: | 1873-6009 (Electronic) 0169-7722 (Linking) |
| Abstract: | "A field-based investigation was conducted at a contaminated site where the vadose zone was contaminated with a range of chlorinated hydrocarbons. The investigation consisted of groundwater and multilevel soil-gas monitoring of a range of contaminants and gases, along with isotope measurements and microbiology studies. The investigation provided multiple lines of evidence that demonstrated aerobic biodegradation of vinyl chloride (VC) was occurring in the vadose zone (i) above the on-site source zone, and (ii) above the downgradient off-site groundwater plume location. Data from both the on-site and off-site locations were consistent in showing substantially greater (an order of magnitude greater) rates of VC removal from the aerobic vadose zone compared to more recalcitrant contaminants trichloroethene (TCE) and tetrachloroethene (PCE). Soil gas VC isotope analysis showed substantial isotopic enrichment of VC (delta(1)(3)C -5.2 to -10.9 per thousand) compared to groundwater (delta(1)(3)C -39.5 per thousand) at the on-site location. Soil gas CO(2) isotope analysis at both locations showed that CO(2) was highly isotopically depleted (delta(1)(3)C -28.8 to -33.3 per thousand), compared to soil gas CO(2) data originating from natural sediment organic matter (delta(1)(3)C= -14.7 to -21.3 per thousand). The soil gas CO2 delta(1)(3)C values were consistent with near-water table VC groundwater delta(1)(3)C values (-36.8 to -39.5 per thousand), suggesting CO(2) originating from aerobic biodegradation of VC. Bacteria that had functional genes (ethene monooxygenase (etnC) and epoxyalkane transferase (etnE)) involved in ethene metabolism and VC oxidation were more abundant at the source zone where oxygen co-existed with VC. The distribution of VC and oxygen vadose zone vapour plumes, together with long-term changes in soil gas CO(2) concentrations and temperature, provided information to elucidate the factors controlling aerobic biodegradation of VC in the vadose zone. Based on the overlapping VC and oxygen vadose zone vapour plumes, aerobic vapour biodegradation rates were independent of substrate (VC and/or oxygen) concentration. The high correlation (R=0.962 to 0.975) between CO(2) concentrations and temperature suggested that aerobic biodegradation of VC was controlled by bacterial activity that was regulated by the temperature within the vadose zone. When assessing a contaminated site for possible vapour intrusion into buildings, accounting for environmental conditions for aerobic biodegradation of VC in the vadose zone should improve the assessment of environmental risk of VC intrusion into buildings, enabling better identification and prioritisation of contaminated sites to be remediated" |
| Keywords: | "Aerobiosis Bacteria/genetics/*metabolism Biodegradation, Environmental Environmental Monitoring Genes, Bacterial Groundwater/chemistry/microbiology Hydrocarbons, Chlorinated/*metabolism Mixed Function Oxygenases/genetics Soil Microbiology Transferases/gen;" |
| Notes: | "MedlinePatterson, B M Aravena, R Davis, G B Furness, A J Bastow, T P Bouchard, D eng Research Support, Non-U.S. Gov't Netherlands 2013/09/04 J Contam Hydrol. 2013 Oct; 153:69-77. doi: 10.1016/j.jconhyd.2013.07.008. Epub 2013 Aug 13" |
