Quantitative understanding of the transport and residence time of PAHs and related organic contaminants in coastal ocean are limited. PAHs and many other chemicals like organochloride pesticides have low aqueous solubility and high partition coefficients. They are readily ‘sorbed’ to certain particles, and are subsequently scavenged and deposited to bottom sediments or transported to the deeper ocean. Naturally occurring radioisotopes present in the ocean like 234Th and 210Pb, which are particle reactive, have been extensively used to understand particle transport and scavenging in the global ocean. In the current work, we utilized such radioisotopes in conjunction with PAH data to understand the particulate PAH residence time in water column and their accumulation in sediments of coastal Louisiana. Suspended particulate PAHs in coastal Louisiana were found to vary between 3.2 ± 1.9 ng L− 1 with their scavenging residence time varying between 2-18 days. Lower molecular weight PAHs (≤3 rings) contributed 89.0 ± 1.7% of the total particulate PAHs while middle molecular weight (4 rings) and higher molecular weight (&gt;4 rings) PAHs contributed about 10 ± 1.4, and 0.8 ± 0.5% of the total particulate PAHs, respectively. Moreover, 88.0% of the total particulate PAHs were due to alkyl homologous of the parent PAHs. The subsequent accumulation of PAH in the sediments were found to vary between 6–55 ng cm−2 y−1 with no significant change in their sediment accumulation rates over a 5 year period. PAHs source diagnostic analyses does not indicate a noticeable change in sediment PAHs composition in the recent years for this region.

Quantifying Polycyclic Aromatic Hydrocarbons (PAHs) distribution and accumulation in coastal Louisiana using natural radioisotope tracers

253rd National Meeting (2017)

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