title: Use of Cl and C isotopic fractionation to identify degradation and sources of polychlorinated phenols: mechanistic study and field application.
abstract: The widespread use of chlorinated phenols (CPs) as a wood preservative has led to numerous contaminated sawmill sites. However, it remains challenging to assess the extent of in situ degradation of CPs. We evaluated the use of compound-specific chlorine and carbon isotope analysis (Cl- and C-CSIA) to assess CP biotransformation. In a laboratory system, we measured isotopic fractionation during oxidative 2,4,6-trichlorophenol dechlorination by representative soil enzymes (C. fumago chloroperoxidase, horseradish peroxidase, and laccase from T. versicolor). Using a mathematical model, the validity of the Rayleigh approach to evaluate apparent kinetic isotope effects (AKIE) was confirmed. A small but significant Cl-AKIE of 1.0022 ± 0.0006 was observed for all three enzymes, consistent with a reaction pathway via a cationic radical species. For carbon, a slight inverse isotope effect was observed (C-AKIE = 0.9945 ± 0.0019). This fractionation behavior is clearly distinguishable from reported reductive dechlorination mechanisms. Based on these results we then assessed degradation and apportioned different types of technical CP mixtures used at two former sawmill sites. To our knowledge, this is the first study that makes use of two-element CSIA to study sources and transformation of CPs in the environment.
authors.affiliation: Department of Applied Environmental Science (ITM), Stockholm University, SE-106 91 Stockholm, Sweden. caeppli@whoi.edu
authors.forename: Christoph
authors.initials: C
authors.lastname: Aeppli
authors.forename: Mats
authors.initials: M
authors.lastname: Tysklind
authors.forename: Henry
authors.initials: H
authors.lastname: Holmstrand
authors.forename: Örjan
authors.initials: Ö
authors.lastname: Gustafsson
mesh_terms: D031215:Armoracia / Q000201:enzymology; D001203:Ascomycota / Q000201:enzymology; D001487:Basidiomycota / Q000201:enzymology; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000302:isolation & purification / Q000378:metabolism; D005591:Chemical Fractionation / Q000379:methods; D002711:Chloride Peroxidase / Q000378:metabolism; D002713:Chlorine / Q000302:isolation & purification / Q000378:metabolism; D002733:Chlorophenols / Q000378:metabolism*; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants / Q000378:metabolism*; D005659:Fungicides, Industrial / Q000378:metabolism*; D054879:Halogenation; D006735:Horseradish Peroxidase / Q000378:metabolism; D007554:Isotopes / Q000302:isolation & purification / Q000378:metabolism; D042845:Laccase / Q000378:metabolism; D008954:Models, Biological; D010084:Oxidation-Reduction
chemical_list: D002247:Carbon Isotopes; D002733:Chlorophenols; D004785:Environmental Pollutants; D005659:Fungicides, Industrial; D007554:Isotopes; D002713:Chlorine; D042845:Laccase; D006735:Horseradish Peroxidase; D002711:Chloride Peroxidase; C024564:2,4,6-trichlorophenol