Stormwater ponds
improve
water quality by facilitating the sedimentation of particles and particulate
contaminants from urban runoff. Over time, this function entails the
accumulation of contaminated sediments, which must be removed periodically
to maintain a pond’s hydraulic and treatment capacity. In this
study, sediments from 17 stormwater sedimentation facilities from
four Swedish municipalities were analyzed for 259 organic substances
likely to be found in the urban environment. A total of 92 substances
were detected in at least one sample, while as many as 52 substances
were detected in a single sample. A typical profile of urban contamination
was identified, including polychlorinated biphenyls, polycyclic aromatic
hydrocarbons, organotins, aliphatic hydrocarbons, phthalates, aldehydes,
polybrominated diphenyl ethers, perfluorinated substances, and alkylphenols.
However, levels of contamination varied greatly between ponds, influenced
heavily by the dilution of urban pollutants and wear particles from
other sources of particles such as eroded soil, sand, or natural organic
matter. For 22 of 32 samples, the observed concentrations of at least
one organic substance exceeded the regulatory threshold values derived
from toxicity data for both sediment and soil.