Unresolved Complex Mixtures of Aromatic Hydrocarbons:  Thousands of Overlooked Persistent, Bioaccumulative, and Toxic Contaminants in Mussels

Abstract

Comprehensive two-dimensional gas chromatography-time-of-flight-mass-spectrometry can be used to resolve and identify individual petroleum-derived hydrocarbons in unresolved complex mixtures (UCMs), such as those accumulated by mussels (Mytilus edulis). Mussels exhibiting a range of scope for growth values were collected from sites around the UK coast. Tissue extracts from mussels exhibiting impaired health contained large amounts of aromatic hydrocarbon UCMs compared to the extracts from healthy mussels. The UCMs (up to 125 microg g(-1) dry tissue) contained thousands of previously unidentified branched alkyl homologues of known aromatic hydrocarbons such as branched alkylbenzenes (BABs), tetralins (BATs), and indanes and indenes (BINs). The toxicity of few such alkyl branched compounds has been investigated previously, but here we show that a commercial mixture of BABs (C12-C14) is toxic to mussels in laboratory tests (11-57 microg g(-1) dry tissue), reducing feeding rate by up to 40% in 72 h. Thus, some, if not all aromatic UCMs, apparently comprise potent mixtures of persistent, bioaccumulative and toxic compounds which have been overlooked previously.

Effect of field exposure to 38-year-old residual petroleum hydrocarbons on growth, condition index, and filtration rate of the ribbed mussel, Geukensia demissa

“…This current PAH content is 40x greater than thresholds thought to be associated with the incidence of biological effects (Long et al, 1995), assuming that the biological response for parent and alkylated PAHs is the same. Furthermore, the PAHs found in these sediments are characteristic of PAHs shown to chronically persist within bivalve tissues (Boehm and Quinn, 1977;Stegeman 1981;Farrington et al, 1982;Booth et al, 2007).…”

Toxicity of diesel contaminated soils to the subantarctic earthworm Microscolex macquariensis

“…Naturally occurring biological and physical processes, such as volatilization, leaching, and microbial degradation, selectively change the composition of petroleum hydrocarbon compounds, thereby altering the toxicity of contaminated soils to biota [12]. Over time, as the chemistry of petroleum hydrocarbons in the soil changes, soils are left contaminated with what is referred to as an unresolved complex mixture of hydrocarbons (UCM; also referred to as recalcitrant petroleum hydrocarbon residuals) that are resilient to degradation [13,14]. In cold regions, these natural processes take extended periods of time, but can be enhanced through remediation practices.…”

Toxicity of sediment-associated unresolved complex mixture and its impact on bioavailability of polycyclic aromatic hydrocarbons

“…Although the UCM or "humps" of petroleum hydrocarbons were commonly encountered during GC analysis, little consideration has been given to their toxicological effects [14,15]. Recent studies, however, have showed that the UCM constituents in sediment not only accumulated in benthic organisms, but also caused sub-lethal effects to these organisms [7][8][9][10][11]15].…”

“…Recent studies, however, have showed that the UCM constituents in sediment not only accumulated in benthic organisms, but also caused sub-lethal effects to these organisms [7][8][9][10][11]15]. For example, UCM contributed to the overall toxic effects of oils to the marine amphipod Corophium volutator and its contribution was separate from the PAHs [7].…”