Measurement and manipulation of copper speciation and toxicity in urban runoff, acid mine drainage, and contaminated discharged groundwater.

摘要

Copper is one of the most important contaminants in natural waters due to its relatively high toxicity to algae, zooplankton, and fish. Lethal concentrations of copper in water are from urban runoff, particularly highway runoff, acid mine drainage, pesticide application, and the discharge of contaminated groundwater. Normally total or dissolved copper concentrations are regulated, though the bioavailable copper fraction is generally a much smaller concentration. These projects investigated the relationship between the chemistry and toxicity of copper in various natural water settings using the Chelex-100 resin, for labile copper separation, and the zooplankton, Ceriodaphnia dubia , for toxicity tests.; Stormwater samples taken from the eastern side of the San Francisco Bay showed that the particulate, dissolved non-labile, and dissolved labile copper concentrations in stormwater vary widely during the progression of a storm, with labile comprising 10–25% of the dissolved copper. The chelating capacity in stormwater copper was measured to be ∼3 μM, which was an order of magnitude higher than the chelating capacity found in dry weather flows.; Metal chemistry was manipulated indirectly in acid mine drainage with high copper concentration, via carbon addition in the form of sawdust, redwood needles, molasses, oak leaves, and eucalyptus leaves, to stimulate sulfate reducing bacteria (SRB) activity in order to produce sulfide. Though copper sulfide was not measured directly, the treatment microcosms with both a carbon source and a SRB inoculum resulted in a near 100% reduction in the dissolved copper concentration during the experiment. Water from the treatment microcosms had a lower toxicity than the control microcosm when mixed with uncontaminated creek water at a similar ratio to natural dilution.; Copper chemistry in contaminated discharged groundwater was directly manipulated by the addition of the synthetic compound, ethylenediaminetetraacetic acid (EDTA). Concentrations of 35–210 μM EDTA added in the field resulted in ∼50% of the available copper forming non-bioavailable complexes. Further lab experiments proved that the lack of complete copper chelation, which was predicted by computer speciation modeling, was caused by the Versene-100 EDTA solution used in the field. If pure EDTA were added instead, all of the aquatic copper would form stable, non-labile complexes.