Stable chlorine isotopic compositions of aroclors and aroclor-contaminatedsediments

An exploratory investigation was conducted to evaluate if stable chlorine i sotopic ratios of polychlorinated biphenyls (PCBs) could be useful in study ing the processes that determine their transport and fate in the environmen t First, we determined the variability of delta(37)Cl in the source materia ls for PCBs. Second, we determined if the delta(37)Cl values of contaminate d environmental samples fell outside the range in source variability. The i sotopic variability among the source materials (Aroclors) was rather small; delta(37)- Cl values ranged from -3.37 to -2.11% (mean and standard deviat ion, -2.78 +/- 0.39%, n = 12). There was no correlation between the delta(3 7)Cl values and percentages of chlorine in the mixtures. We also found very similar values in several Clophen mixtures and one Phenoclor. The delta(37 )Cl values in the total PCBs isolated from Aroclor-contaminated sediments f rom the Hudson River, New Bedford Harbor, and Turtle River Estuary ranged f rom -4.54 to -2.25% (n = 19). While most of the delta(37)Cl values were wit hin 2 standard deviations of the mean Aroclor value (our assumed estimate f or overall source variability), two of the PCB contaminated sediment sample s from New Bedford Harbor did appear to be isotopically distinct. The PCBs in these sediments had lower amounts of less chlorinated congeners (when co mpared to the source material) and were likely isotopically affected by alt eration processes that preferentially removed these congeners. Compound spe cific measurements of two congeners in Aroclor 1268 suggest that there are no large congener-specific differences in the stable chlorine isotope ratio s in Aroclors. This study shows that the delta(37)Cl Values of PCBs may be a potentially useful diagnostic tool in studying the transport and fate of PCBs and indicates that additional research is warranted.