Halogenated organic compounds of environmental relevance in the Southern California Bight and beyond
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Halogenated organic compounds of environmental relevance in the Southern California Bight and beyond


Halogenated organic compounds (HOCs) are a diverse groups of both environmentally interesting and challenging compounds. With both natural and anthropogenic sources and a wide range of toxicities, predictions of their environmental transport and fate are not always straightforward. This dissertation includes four chapters that explore HOCs in the environment. The first chapter introduces HOCs and what is currently known about their sources and environmental transport and fate and is followed by two research chapters and a summary chapter. Chapter 2 describes the development of a nontargeted approach to catalogue the accumulative HOCs in environmental samples. A mass spectral library was constructed of 327 persistent and bioaccumulative compounds identified in blubber from two ecotypes of common bottlenose dolphins (Tursiops truncatus) sampled in the Southern California Bight. The abundance of compounds whose structures could not be fully elucidated highlights the prevalence of undiscovered HOCs accumulating in marine food webs. Eighty-six percent of the identified compounds are not currently monitored, including 133 known anthropogenic chemicals. Compounds related to dichlorodiphenyltrichloroethane (DDT) were the most abundant. Natural products were, in some cases, detected at abundances similar to anthropogenic compound abundances. This nontargeted analytical framework has generated a comprehensive list of HOCs that may be characteristic of the region, and its application within monitoring surveys may suggest new chemicals for evaluation. Chapter 3 investigated the abundance, distribution, and ecological relevance of the dimethyl (DMBPs) and methyl bipyrroles (MBPs) present in coastal- and offshore-dwelling ecotypes of common bottlenose dolphins (Tursiops truncatus) stranded within the Southern California Bight and examined pyrrole distributions and compositions across the available datasets using a lens that considers the possible sources of these compounds and their cycling once released into the environment. The fully halogenated DMBP and MBP congeners have been detected the most frequently, specifically DMBP-Br4Cl2 and MBP-Cl7 (Q1). The D/MBP concentrations vary over large ranges, and the levels of D/MBP isomers detected in the environment do not appear to follow the trend predicted by their bioconcentration factors. Overall, the offshore dolphins sampled contained more abundant and diverse D/MBPs than the coastal dolphins. The analyses illustrate that the bioaccumulation of these compounds is not necessarily straightforward in all environments. To guide future investigations, a representative suite of Q1, MBP-Cl6, MBP-Br6, DMBP-Cl6, DMBP-Br6, and DMBP-Br4Cl2 could serve as an indicator of this compound class, with differences in this fingerprint potentially related to the sample location.

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