ABSTRACT: Long-Term Sampling of Selected Heavy Metals Concentrations in the Bottom Sediments of Imperial River and Spring Creek, Lee County, Southwestern Florida
MITCHELL-TAPPING, HUGH J. and ALETA M. MITCHELL-TAPPING
Heavy metal concentrations
are important in terms of their potential toxic effects and as a signal
for the presence of other types of pollution. However, heavy metals pollution
has four major interpretive
problems: (1) determining residual long-term
geologic chemical reactions, (2) distinguishing those components attributable
to natural causes from those attributable to man's activities, (3) determining
whether anthropogenically-enriched sediments are likely to cause adverse
affects, and (4) determining if the pollution is permanent (long-term)
or is an isolated event (short-term). Among the toxic heavy metals found
in stormwater, lead, copper and zinc appear to be the most abundant and
frequently detected. As stormwater runoff is of major importance in southwestern
Florida, this study has examined copper, lead, zinc and iron concentrations,
quarterly from 1981 to 1995, from sites along Spring Creek and Imperial
River. The results have given insight into the relationship of metal concentration
to changes in sediment grain-size and content during both wet and dry seasons,
and also to long-term pollution assessments. For example, a very high copper
concentration was detected in silt and clay-sized particles at an Imperial
River marina site. The same site was sampled the following year at the
end of the wet season. The analysis indicated that sediment size had increased
and copper concentration had returned to the lower natural background values
of previous years. The high copper concentration was subsequently determined
to be due to antifouling and preservatives of newly installed wooden mooring
posts and that the wet season stormwater runoff had flushed many of the
clay-sized particles from the marina sediments.
AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana