HEAVY METAL CONTAMINANTS IN RIVER WATER; COEUR D'ALENE IDAHO

Over a century of unregulated mining practices within the Silver Valley of Idaho and Montana has led to the introduction of waste material containing heavy metal contaminants (As, Cd, Fe, Pb, Zn). The presence of many of these elements in large abundance can cause inadvertent effects on aquatic life and associated biota. Contamination has been dispersed throughout the entire Coeur d’Alene River system via fluvial transport and biological interactions. Concentrations of heavy metals within sediments as well as vegetation are now much greater than prehistoric times. Concern for the river ecosystem as well as potential effects on large human populations downstream have led to an appropriate amount of concern for this problem. Water samples were collected from multiple locations within the Coeur d’Alene River basin in order to gain a further understanding of the heavy metals currently available within the river system. Sample locations included both the North Fork and South Fork of the Coeur d’Alene River, one of which contained no historic mining (North Fork), and one of which had mining waste dumped into it for decades (South Fork). Samples were also taken from the mainstem of the Coeur d’Alene River at three different locations, as well as the Spokane River which lies on the northwest side of Lake Coeur d’Alene. Toxic levels of zinc and cadmium were found within the South Fork and along the mainstem of the Coeur d’Alene River. Lead concentrations were highest in the Coeur d’Alene River just upstream from Lake Coeur d’Alene. The presence of these heavy metals within the river system indicate a potential for negative impacts, and high toxicity for plants, micro and macro-invertebrates, as well as fish, and potentially other large mammals as these metals may be biomagnified through the food web.