Modeled PCB Weathering Series in Principal Components Space: Considerations for Multivariate Chemical Fingerprinting Check Access

Commercial formulations of polychlorinated biphenyls (PCBs) can weather after release to the ambient environment. A considerable amount of research has been done to quantify and establish predictive models for movement of chemicals between phases. Fugacity modelling is one framework used for this predictive approach. Fugacity is a quantitative measure of the “escaping” tendency of a chemical from one phase to another (e.g., water, mineral, organic matter, lipids). The objective is to predict the concentrations of a chemical in multiple phases (e.g., air, soil, and water) based on equilibrium partitioning equations. Weathering of PCBs in the ambient environment can result in congener profiles in sampled media (sediment, soil, air) that have been altered to the point that the profile differs significantly from the original source. Such alteration is most dramatic when “lighter” Aroclors are weathered (those with higher proportions of low-chlorinated congeners), in particular Aroclor 1242. In this chapter the influence that weathering can have on PCB fingerprinting is investigated using fugacity modelling. The modelling simulates the physical weathering of Aroclor 1242 in different environments (e.g., dry soil, submerged sediment), and assumes two different types of organic matter in the soil/sediment. The data from these weathering series, and the changes in how the congener distribution manifests itself in principal components analysis (PCA) score-plots, are shown.