title: First compound-specific chlorine-isotope analysis of environmentally-bioaccumulated organochlorines indicates a degradation-relatable kinetic isotope effect for DDT.
abstract: Compound-specific chlorine-isotope analysis (CSIA-Cl) of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (p,p'-DDE) in blubber from Baltic Grey seal (Halichoerus grypus) was performed in order to investigate if a kinetic isotope effect (KIE) could be observed concomitant to environmental degradation of DDT. The delta(37)Cl of p,p'-DDT and p,p'-DDE were -0.69 +/- 0.21 per thousand and -2.98 +/- 0.57 per thousand (1s igma, n = 3), respectively. Both samples were enriched relative to the hypothesized initial isotope composition (-4.34 per thousand), thus indicating a composite KIE associated with the degradation mechanisms pertaining to DDT. An isotope fractionation factor for degradation of dichloromethane, from the literature, was adapted and modified for use in the calculation of DDT degradation. A subsequent simplified Rayleigh distillation model of the DDT chlorine-isotope composition yielded an estimated fraction (f) of 7 +/- 2% of released DDT presently remaining as undegraded compound in the environment. The consistency between the result of the Rayleigh model (f approximately 7%) and the use of the DDT/(DDT + DDE) ratio as a measure of DDT degradation ( approximately 10% undegraded DDT) suggests that the KIE of DDT degradation may be significant, and that the novel approach of CSIA-Cl may be a valuable tool for degradation/persistence studies of lipophilic organochlorines in the environment.
authors.affiliation: Laboratory for Isotope Geology, Swedish Museum of Natural History, Box 50007, Stockholm SE-104 05, Sweden.
authors.forename: Henry
authors.initials: H
authors.lastname: Holmstrand
authors.forename: Manolis
authors.initials: M
authors.lastname: Mandalakis
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Zencak
authors.forename: Per
authors.initials: P
authors.lastname: Andersson
authors.forename: Orjan
authors.initials: O
authors.lastname: Gustafsson
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001673:Biodegradation, Environmental; D002713:Chlorine; D002849:Chromatography, Gas; D003634:DDT / Q000032:analysis* / Q000493:pharmacokinetics; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D007554:Isotopes; D007700:Kinetics; D013058:Mass Spectrometry; D008956:Models, Chemical; D046048:Seals, Earless / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D007554:Isotopes; D014874:Water Pollutants, Chemical; D002713:Chlorine; D003634:DDT