Copper retention and toxicity in a freshwater sediment

Abstract

The effects of Cu(II) sulfate on sediment respiration were investigated in a 3-phase aquatic microcosm, containing a calcareous, southern Ontario stream sediment. In Cu2+ treated flask-microcosms, with the pH restored to 7.1, both aerobic and anaerobic CO2 evolution were unaffected by 5000 jig Cu g−1 sediment over a 40-day period at 15 °C. Oxygen consumption in sediment was initially unaffected by 5000 μg Cu g−1. However, after 35 to 40 days, a significant reduction of 28% was observed. The added Cu−2+ was removed from the water column and the sediment solution. In microcosms containing 5000 μg g−1 of total Cu, only 1.00 ± 0.76 μg g−1 was water soluble Cu, and the free cupric cation (Cu2+) concentration was below the detection limit of the specific ion electrode (less than 0.01 μg g−1). Maximum Cu retention (98.6%) was observed at 2800 μg Cu g−1, above which fractional retention decreased. In a calcareous, organic rich, sediment of pH 7.1, Cu+ was essentially unvailable to exert a toxic effect on respiration.