Sediment Sources and Sealed-Pavement Area Drive Polycyclic Aromatic Hydrocarbon and Metal Occurrence in Urban Streams

Metals
and polycyclic aromatic hydrocarbons (PAHs) are common pollutants
in urban streambed sediment, yet their occurrence is highly variable
and difficult to predict. To investigate sources of PAHs and metals
to streambed sediment, we sampled pavement dust, soil, and streambed
sediment in 10 urban watersheds in three regions of the United States
and applied a fallout-radionuclide-based sediment-source analysis
to quantify the pavement dust contribution to stream sediment (%dust).
We also mapped the area of sealcoated pavement in each watershed (%sealed)
to investigate the role of coal-tar pavement sealant (CTS) as a PAH
source. Median total and carbon-normalized total PAH concentrations
were significantly higher in streambed sediment in the Northeast (54.3
mg/kg and 2.71 mg/gOC) and Southeast (5.37 mg/kg and 1.36 mg/gOC),
where CTS is commonly used, than in the Northwest (2.11 mg/kg and
0.071 mg/gOC), where CTS is rarely used. Generalized additive models
indicated that %sealed and in some cases %dust significantly affected
total PAH concentrations in streambed sediments. The %dust was a significant
variable for common urban metals: Cu, Pb, and Zn. These findings advance
our quantitative understanding of the role of pavement dust as a source
and a vector of contaminants to urban streams.