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Florida Scientist


Iron, copper and zinc were monitored in the water, sediments, and 4 species of fish of the upper St. Johns River, Florida. Surface water concentrations of total iron commonly exceeded 300 ug/l, the standard established by the Florida Department of Environmental Regulation for waters intended for public consumption (Class I waters). Total iron levels in the upper St. Johns River are regulated by a series of interacting natural processes such as the ironphosphate cycle, inputs from nonartesian groundwater or bank seepage, complexation with dissolved organic compounds, increased land runoff during perids of high flow, and resuspension of bottom sediments during periods of increased discharge or wind mixing. Groundwater inputs in the headwaters region due to agricultural irrigation practices, in addition to runoff and groundwater seepage into the drainage canals entering the river, have significantly increased its trace metal content. Elevated trace metal levels were also found in sediments and fish tissue in the river. The results of multiple regression analyses indicated that as the extent of urban activity increases in undeveloped watersheds of the upper St. Johns River, total copper and total zinc concentrations in the surface waters of the watershed can also be expected to increase.

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