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Metal concentrations in rivers and streams vary continually. An indicator of toxic trace metals is needed to establish recent maximum levels. An initial study was conducted during the summer of 1979 on Coal Creek and Slate River, Gunnison County, Colo., to test whether aquatic insects could be used to assay for low-level element presence. Aquatic insects were taken from Coal Creek above a mine tailing break. Both live and air-dried insects were transplanted to the Slate River below the discharge from the mine and removed consecutively for 3 days. Water samples were taken simultaneously with each insect collection. The dissolved ions in a litre of stream water were concentrated to 25 ml with the use of an ion-exchange resin column. The results demonstrate that the ratio of the concentration of the element in the insect to the concentration of the element in the water, the field concentration factor (FCF), for each genus of aquatic insect is more sensitive than a water sample for measuring the level of cadmium in water. The insect cadmium accumulation and water cadmium levels exhibited a repeated relationship in the Slate River. The similarity between the sorption of cadmium by the live and dead insects indicates that cadmium uptake is more than a physiological process. Mayflies concentrate cadmium and molybdenum more than caddis flies, and of the mayflies tested the Drunella grandis sorbs the most. Equilibration between water and insect concentration of cadmium appears to take place after 72 h.
aquatic insect, cadmium, molybdenum, trace element, concentration, field concentration factor (FCF), aquatic toxicology, hazard assessment
Graduate student, Western State College of Colorado and Rocky Mountain Biological Laboratory, Gunnison, Colo.