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Copper accumulation on gills of fathead minnows: Influence of water hardness, complexation and pH of the gill micro‐environment
Author(s) -
Playle Richard C.,
Gensemer Robert W.,
Dixon D. George
Publication year - 1992
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620110312
Subject(s) - gill , soft water , copper , chemistry , environmental chemistry , hard water , pimephales promelas , toxicity , nuclear chemistry , fish <actinopterygii> , biology , fishery , minnow , organic chemistry
Water pH in the gill micro‐environment of adult fathead minnows (Pimephales promelas Rafinesque) was measured by means of opercular catheters and latex masks. Synthetic soft water of pH <5.7 was rendered more basic as it passed over the gills and water of pH >5.7 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% Cu 2+ 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 (Ca 2+ 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 Ca 2+ 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 Ca 2+ and H + competition with Cu for gill binding sites and by complexation of Cu by EDTA. Added CaCO 3 did not reduce gill Cu, although both competition by Ca 2+ and complexation by CO 2− 3 were expected. Water chemistry calculations suggested that because little CO 2− 3 is available at pH < 7, CO 2− 3 from CaCO 3 is less likely to affect Cu deposition on fish gills than is Ca 2+ from CaCO 3 .