PAH source differentiation between historical MGP and significant urban influences for sediments in San Francisco Bay

A forensic source evaluation of polycyclic aromatic hydrocarbons (PAHs) in nearshore sediments in San Francisco Bay examined total PAH greater than ambient concentrations in sediments, and potential pyrogenic source relationships with respect to PAH compounds typically associated with point and nonpoint pyrogenic source types, including PAHs potentially associated with historical manufactured gas plant (MGP) operations. Diagnostic source ratio analysis was employed for determination of potential PAH source relationships. A two-model approach indicated distinct potential source signatures, as identified from the distributions of higher PAH concentrations in some sediments. Source characterization was aided by Polytopic Vector Analysis (PVA) and data visualization with t-Distributed Stochastic Neighbor Embedding (t-SNE). Two signatures exhibited pyrogenic character likely consistent with historical MGP sources, and one signature was related to creosote. A distinct and significant source of PAHs to the investigation area sediment consisted of ubiquitous nonpoint and potential unidentified point sources is termed 'urban influence'.

Automated summary

The forensic evaluation of PAHs in nearshore sediments in San Francisco Bay identified potential source relationships with historical MGP operations and creosote. Using diagnostic source ratio analysis, distinct source signatures were determined, with two exhibiting pyrogenic character consistent with MGP sources and one related to creosote. Urban influence was identified as a significant source of PAHs in the investigation area sediment, along with nonpoint and potential unidentified point sources.