Overview
Polycyclic aromatic hydrocarbons (PAHs) continue to be common environmental contaminants. These toxic compounds, which are produced through incomplete combustion of organic matter found in fossil fuels and other sources, are a threat to public health and our state’s ecosystems. This study analyzed sediments from rivers that flow through and beyond three small Wisconsin cities — Root River (Racine), Plover River (Stevens Point), and Eau Claire River (Eau Claire) to determine their widespread effects in smaller Wisconsin communities.
Key Points
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PAH Contamination Exists Beyond Major Cities: Sediment samples from Eau Claire, Stevens Point, and Racine revealed measurable PAH concentrations, sometimes exceeding ecological safety thresholds, despite their smaller population sizes.
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Coal-Tar Sealants As a Major Source: Multiple lines of evidence show that coal-tar-based pavement sealants are a major contributor to PAH contamination across all three municipalities.
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Environmental And Economic Implications: Contaminated sediment in stormwater detention ponds poses both ecological risks and financial costs for municipalities, as disposal of PAH-laden material requires expensive hazardous waste management.
Summary
PAHs are toxic compounds produced by the incomplete combustion of organic matter, common in fossil fuel burning and found naturally in coal, tar, and oil. They accumulate in soils and sediments due to their resistance to degradation and high affinity for particulates. The anthropogenic sources of PAH compounds include activities such as coal burning, oil spills, and application of coal tar sealants. Several studies have focused on PAHs in sediments of lakes, streams, and stormwater ponds in larger urban areas, finding contamination from a number of different sources and correlating well to land use in the nearby watershed.
Among tested sediments, this study shows PAH levels were highest in Racine, followed by Stevens Point and Eau Claire. Even though smaller cities had lower absolute contamination than large urban centers, the findings demonstrate that localized sources like coal-tar sealants can still cause significant pollution.
The study underscores that stormwater management ponds—common in urban planning—may accumulate PAH-contaminated sediment. Findings show that smaller cities may need to plan for such contamination and should consider taking steps to reduce future pollution and remediation costs.
Important Takeaways
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PAHs Are Toxic And Persistent: They are mutagenic and carcinogenic, linked to cancers and developmental harm, and persist in sediment due to slow degradation.
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Contamination Is Linked To Urbanization: Developed and impervious areas have the highest PAH levels. Rural and natural areas show less contamination, but more data is needed.
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Coal-Tar Sealants Are a Main Source: The same source responsible for urban PAH pollution in Milwaukee is also dominant in smaller cities.
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Aquatic Life At Risk: PAH levels in some smaller cities exceed safety thresholds, potentially affecting fish and other aquatic organisms.
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Municipalities Face Costly Cleanups: Stormwater pond sediment contaminated with PAHs requires special disposal, creating financial burdens for local governments.
