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>Copper accumulation on gills of fathead minnows: Influence of water hardness, complexation and pH of the gill micro‐environment
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Copper accumulation on gills of fathead minnows: Influence of water hardness, complexation and pH of the gill micro‐environment
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机译：Copper accumulation on gills of fathead minnows: Influence of water hardness, complexation and pH of the gill micro‐environment
AbstractWater pH in the gill micro‐environment of adult fathead minnows(Pimephales promelasRafinesque) was measured by means of opercular catheters and latex masks. Synthetic soft water of pH5.7 was made more acidic, so that pH of the gill micro‐environment stayed at approximately 5.4 to 5.9 over the inspired pH range 4.8 to 6.3. Copper would therefore be>99 Cu2+at the gills. To measure Cu accumulation on gills, the target organ for Cu toxicity, adult fathead minnows were exposed for 2 to 3 h to 16 μg/L Cu in synthetic soft water (Ca2+and Na+approximately 50 μeq/L) at pH 4.8 and 6.3. Gill Cu concentrations were about 1.7 μg Cu/g wet tissue for the inspired pH 4.8 and 6.3 exposures. Added Ca2+of 2,100 or 4,000 μeq/L reduced gill Cu accumulation during exposures at pH 4.8 but not at pH 6.3. EDTA eliminated Cu deposition at both pH 4.8 and pH 6.3 when equimolar with Cu, but reduced Cu deposition (by 50) when half equimolar only in the pH 4.8 exposures. These results can be explained by Ca2+and H+competition with Cu for gill binding sites and by complexation of Cu by EDTA. Added CaCO3did not reduce gill Cu, although both competition by Ca2+and complexation by CO2−3were expected. Water chemistry calculations suggested that because little CO2−3is available at pH<7, CO2−3from CaCO3is less likely to affect Cu deposition on fish gills than is C
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