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SEDIMENT HAZARD ASSESSMENT FOR NEAR-COASTAL AREAS OF THE GULF OF MEXICO
Citation:
Lewis, M A. SEDIMENT HAZARD ASSESSMENT FOR NEAR-COASTAL AREAS OF THE GULF OF MEXICO. Presented at Estuarine Indicator Workshop, Sanibel Island, FL, Oct 29-31, 2003.
Description:
Sediment contamination is a major problem in many coastal areas in the U.S. and has emerged as an important ecological issue for several geographic areas. Sediment chemical and biological quality is unknown in many areas of the Gulf of Mexico. To provide some information on this issue, sediment quality was determined in a multi year study for 108 near-coastal sites mostly located in Florida. The primary objective of the study was to determine the extent and magnitude of sediment contamination in relation to sources of contaminant stress common to Florida coastal areas. Other objectives included identifying relevant assessment techniques, sensitive toxicity test species and determining the predictability of proposed sediment quality guidelines proposed for Florida coastal areas. Sampling sites were located in reference areas and those impacted by 11 wastewaters and storm water runoff from urban areas, golf courses and agricultural fields. Contaminant concentrations in surface water and sediment were determined for 12 trace metals, 25 chlorinated pesticides, 18 PCB congeners and 24 PAH compounds. Three hundred and fifty acute and chronic whole sediment and pore water toxicity tests of 4 to 28 days duration were conducted with six species of estuarine invertebrates. Sediment phytotoxicity was determined using three common wetland vascular plants and the genotoxic potential (direct and indirect) of pore waters was determined using a microbial assay. Benthic community composition was also analyzed. Exceedances of sediment quality guidelines, toxicity, phytotoxicity and genotoxicity were greater in areas receiving urban runoff. Cadmium, copper, total PCBs, total DDT and DDE were common sediment contaminants that often exceeded quality guideline values. Grass shrimp embryos were the most sensitive test species and pore water was often more toxic than whole sediments. Genotoxicity and phytotoxicity (phytostimulation and phytoinhibition) were relatively common and the results based on these parameters did not parallel those for standard animal test species exposed to the same media nor to sediment quality guidelines. This finding is important in the context of understanding the predictive value of these guidelines and their relevance in the sediment hazard assessment process. It was concluded from the study that sediment hazard evaluations in coastal rivers, bays and estuaries associated with the Gulf of Mexico will require greater effort than those for sediments from other locations due to the unique hydrological (high annual rainfall, episodic weather events) and geomorphological characteristics (shallow) characteristic of this region that can effect contaminant availability.
Invited presentation.