Distribution and potential for adverse biological effects of inorganic elements and organic compounds in bottom sediment, lower Charles River, Massachusetts

Surficial-sediment samples and cores
collected from the lower Charles River Basin are
generally enriched in inorganic elements and
organic compounds, including polychlorinated
byphenyls, total organochlorine pesticides, and
polyaromatic hydrocarbons. Median concentrations
of selected inorganic elements and organic
compounds measured in surficial-sediment
samples collected from the lower Charles River
ranged from 1. 3 to 3 5 times higher than median
concentrations of these constituents measured
in samples collected from urban rivers across
the conterminous United States by the U.S.
Geological Survey's National Water Quality
Assessment Program (NAWQA).

The distribution of the inorganic elements in
surficial sediment throughout the basin appears to
be controlled primarily by in-stream processes
associated with sediment transport and the presence
of an anoxic zone within a non-tidal salt
wedge in the basin. In contrast, the distribution of
organic compounds appears to reflect local point
and non-point sources.

Inorganic elements and organic compounds
are present at sufficiently high concentrations at
many surficial-sediment sampling sites to cause
potentially severe biological effects to benthic
organisms living in and on the bottom sediment.
Ratios of acid volatile sulfide to simultaneously
extracted metals, however, suggest that some inorganic elements would be toxic in fewer than
25 percent of the surficial-sediment samples.
Many individual polyaromatic hydrocarbons, total
petroleum hydrocarbons, and lead measured in
cores exceeded exposure-based soil-concentration
standards for direct contact and incident ingestion
at areas where restoration of public wading and
swimming beaches is being considered.