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<br />5.5 to 7.5 mg/L; hardness, 113 to 120 mg/L as CaCO3; <br />pH, 8.1 to 8.5; alkalinity, 71 to 88 mg/L as CaCO3; specific <br />conductance, 240 µS/cm, and temperature, 18.5 to 21.0 °C. <br />Toxicant Solutions and Analytical Procedures <br />Stock solutions of analytical-grade copper sulfate and zinc <br />sulfate (CuSO4*SHzO and ZnSO4*7H2O; Mallinckrodt, Paris, Ky. ) were <br />prepared in deionized water. Exposure concentrations were <br />prepared by pipetting the desired amount of toxicant stock into <br />beakers containing 0.75 L dilution water. Exposure solutions <br />were stirred and transferred to exposure beakers within 30 min of <br />preparation. Nominal toxicant concentrations ranged from 0 to <br />266 µg/L copper and 0 to 1492 µg/L zinc. <br />Toxicant concentrations were measured at beginning and end <br />of the exposure periods. On each occasion, a 50 ml sample of <br />unfiltered water was collected from each exposure concentration <br />in a prewashed, nitric acid-rinsed, polyethylene bottle. Water <br />samples were preserved by addition of 0.5 ml of analytical-grade <br />nitric acid (Mallinckrodt, Paris, Ky.) and refrigeration at 4 °C. <br />Upon completion of all toxicity exposures, samples were submitted <br />to the Colorado State University, Soil Testing Laboratory (Fort <br />Collins, Co.) for determination of total copper and zinc by <br />inductively-coupled plasma emission spectroscopy. <br />4 <br />