ABSTRACT:

Home Background Purpose and Scope Approach and Methods Results and Discussion Conclusions

Trace elements and organic contaminants in bottom-sediment samples collected from 10 sites on the Barron River Canal and from one site on the Turner River in October 1998 had patterns of distribution that indicated different sources. At some sites on the Barron River Canal, lead, copper, and zinc, normalized to aluminum, exceeded limits normally considered as background and may be enriched by human activities. Polynuclear aromatic hydrocarbons and p-cresol, normalized against organic carbon, had patterns of distribution that indicated local sources of input from a road or vehicular traffic or from an old creosote wood treatment facility. Phthalate esters and the trace elements arsenic, cadmium, and zinc were more widely distributed with the highest normalized concentrations occurring at the Turner River background site, probably due to the high percentage of fine sediment (74 % less than 63 micrometers) and high organic carbon concentration (42 %) at that site and the binding effect of organic carbon on trace elements and trace organic compounds. Low concentrations of pesticides or pesticide degradation products were detected in bottom sediment (DDD and DDE, each less than 3.5 µg/kg) and water (9 pesticides, each less than 0.06 µg/L), primarily in the northern reach of the Barron River Canal where agriculture is a likely source. Although a few contaminants approached criteria that would indicate adverse effects on aquatic life, none exceeded the criteria, but the potential synergistic effects of mixtures of contaminants found at most sites are not included in the criteria.

Figure 1. The Big Cypress National Preserve and major canals including the Barron River Canal. [larger image]

Big Cypress National Preserve (BICY) is a unique 295,000-hectare, water-dependent ecosystem (Fig. 1). As much as 90 % of the BICY is inundated to depths ranging from several centimeters (cm) to more than 0.9 meter (m) during the wet season (May to October). During the dry season (November to April) water levels recede, reducing the area of inundation to approximately 10 %. The ecology of the BICY is finely tuned to the seasonal flow of non-polluted water and changes in seasonal flows or deterioration in water quality can adversely affect the BIC's sensitive habitat. As a result, it is important to identify local and regional impacts on water quality so these impacts can be lessened or averted.