Bacterial Degradation of Pentachlorophenol Indicated in Groundwater Undergoing Long Term In-Situ Remediation

IRG/WP 16-50318

C E Stokes, H Borazjani, L Prewitt

Pentachlorophenol (PCP, Penta) is a worldwide soil and water contaminant. The pervasive use of PCP as a fungicide, herbicide, pesticide, and as preservative for wood products has led to its global distribution. It is a highly effective preventative measure for most invasive insects, bacteria, fungi, and molds, as well as an excellent wood protection treatment. This study examined a known PCP contaminated site that has been undergoing remediation treatment since 2000 to determine if PCP degrading bacteria could be identified using molecular techniques. Bacteria were identified by sequencing the 16s rDNA fragment from DNA extracted from groundwater cultures and comparing those sequences to a database using a basic local alignment search tool, BLAST. The PCP-degraders Burkholderia cepacia and Flavobacterium (Sphingobium) chlorophenolicum were identified in multiple wells, as were the 4-chlorophenol degrader Herbaspirillum chlorophenolicum, and the common soil bacteria Pseudomonas sp., Aquaspirillum sp., and Rhodocista sp., among others. Numerous bacterial samples also appeared in the results as “uncultured”. Diversity measures including species richness, Simpson’s and Shannon’s indices, and species evenness were calculated from operational taxonomic unit results for each well at each sampling point in order to better understand changes in the bacterial community. Species richness tended to be higher at wells further away from the biosparging line, while diversity and evenness varied throughout the area. Correlations between PCP concentration, operational taxonomic units, and distance from biosparging wells were determined by Pearson’s product-moment correlation and Spearman’s rank correlation. Positive correlations were found between distance from biosparging wells and PCP concentration, species richness and distance, and to a smaller degree, diversity and distance. Biosparging remediation has a significant impact on the types of PCP-degrading bacteria within the groundwater matrix, and installations of this type of treatment should be applied to maximize the use of the native bacteria to assist in degradation of the contaminant.

Keywords: pentachlorophenol, bioremediation, restriction fragment-length analysis, chlorinated phenol degradation

Conference: 16-05-15/19 Lisbon, Portugal

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