Congener-based analysis of the weathering of PCB Aroclor 1242 in paper mill sludge

Aroclor 1242 contains a high percentage of lightly chlorinated congeners, which makes it susceptible to congener profile alterations as a result of physical–chemical environmental weathering by water washing, evaporation, and volatilization. The analysis of the variability of congener profiles in paper sludge samples using PCA, mixing models, and correlation (R2) analysis, provided an integrated description of the behavior of Aroclor 1242 after its release in the environment. The results showed that the total PCB concentration decreased as the sample experienced weathering, with the congener profile of Aroclor 1242 shifting towards resembling heavier Aroclors as lighter congeners were lost. Mixing model analysis confirmed that a sample containing weathered Aroclor 1242 could easily be misidentified by laboratories as containing a mix of heavier Aroclors. The R2 analysis showed that the profile of the congeners within a homologue group remained the same after weathering. This analysis showed that congeners that belong to the same level of chlorination behave similarly in such a manner that retains their overall profile when exposed to physical weathering.

Research highlights
► Examine congener profile changes of Aroclor 1242 from paper mill processes.
► Lighter congeners were weathered, resulting in Aroclor 1242 resembling heavier Aroclors.
► Principal Component Analysis tracked the weathering pattern of Aroclor 1242.