210-4 Using Anthropogenic Biomarkers in Sediments to Assess Fossil Fuel and Fecal Pollution in Urban Estuaries

Session: Environmental Geochemistry and Health

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Anthropogenic biomarkers in estuarine sediments offer valuable insights into the sources and extent of human impacts on coastal ecosystems. This study examined the sources and spatial distributions of fossil fuel-derived biomarkers—including hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs)—as well as fecal sterols in surface sediments from Mobile Bay and the adjacent eastern Mississippi Sound, two ecologically important estuarine systems in the northern Gulf of Mexico.

Results revealed distinct spatial patterns in both the sources and concentrations of fossil fuel biomarkers. Northern Mobile Bay was predominantly influenced by land-based inputs, while southern regions, including southern Mobile Bay and the Mississippi Sound, exhibited stronger offshore signatures. Elevated concentrations of αβ-hopanes and C27–C29 steranes in the southern sites were attributed to longer water residence times that facilitated their accumulation. In contrast, higher PAH concentrations in northern locations were linked to proximity to urban and industrial pollution sources. Notably, concentrations of αβ-hopanes and C27–C29 steranes in this study were comparable to—or exceeded—levels reported in other heavily developed estuaries. PAH concentrations at most southern sites remained below established ecological risk thresholds. Fecal biomarker data indicated generally low levels of animal-derived contamination across the region, with one localized hotspot of human-derived fecal input. Higher fecal sterol concentrations observed in the southern subregions likely reflected hydrodynamic conditions that favored organic matter accumulation. The findings enhance understanding of source apportionment and risk assessment of organic contamination in coastal sediments. The source and spatial heterogeneity of anthropogenic biomarkers underscores the need for targeted pollution control strategies.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8700

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