Examining the correlation between quantifiable SVOCs and organic carbon content or particulate size in benthic sediments as a function of ocean stratum
The raw analytical concentration values of semi-volatile organic compounds (SVOCs) in ocean sediments do not necessarily reflect the bioavailable fractions of SVOCs in the sediments due to factors such as the total organic carbon content of sediment (TOC) and the percentage of fine particles in sediments (% Fines) believe to affect the extraction efficiency of SVOCs from sediment. Corrective actions are therefore taken to minimize their influence on measurements. In doing so, a broad and uniform correlation is assumed between the ‘native’ levels of the SVOCs and TOC or %Fines across ocean strata. Not yet verified though is the validity of this blanket assumption. In this study, we examined the strength of the assumption using levels of DDTs, PAHs and PCBs in sediments from Santa Monica Bay (SMB) in California, USA. (The distribution patterns of these SVOCs in SMB are known and reproducible for quality assurance.) As our results show, a uniform correlation between SVOCs levels and TOC or %Fines across strata is mostly unsupported. For example, while PAHs and PCBs levels show negative correlation with TOC or % Fines, and only in canyon sediments, DDTs levels correlate positively with both TOC and %Fines across at least three strata. Furthermore, the distribution of PAH molecules appears to be controlled by molecular size with the smaller PAHs found almost exclusively in the canyons. Our findings here, being the first of its kind, suggest that more work is actually needed to clarify the reporting of SVOCs levels in ocean sediments.
- This article is part of the themed collection: Halogenated (semi)volatile organic compounds (“X(S)VOCs”)