Cyanide Hazards Aquatic Ecosystems

Data on the recovery of cyanide-poisoned ecosystems are scarce. In one case, a large amount of cyanide-containing slag entered a stream from the reservoir of a Japanese gold mine as a result of an earthquake. The slag covered the streambed for about 10 km from the point of rupture, killing all stream biota cyanide was detected in the water column for only 3 d after the spill. Within 1 month, flora was established on the silt covering the abovewater stones, but there was little underwater 

Fish are the most cyanide-sensitive group of aquatic organisms tested. Under conditions of continuous exposure, adverse effects on swimming and reproduction usually occurred between 5.0 and 7.2 p,g free CN/L and on survival between 20.0 and 

Among aquatic invertebrates, adverse non-lethal effects occurred between 18.0 and 

0 pg/L, although some deaths occurred between 3.0 and 7.0 pg/L for the amphipod Gammarus pulex. Aquatic plants are comparatively tolerant to cyanide adverse effects occurred at 160.0 pg free CN/L. Adverse effects of cyanide on aquatic plants are unlikely at concentrations that cause acute effects to most species of freshwater and marine fishes and invertebrates. 

Biocidal properties of cyanide in aquatic environments are modified by water pH, temperature, and oxygen content life stage, condition, and species assayed previous exposure to cyanides presence of other chemicals and initial dose tested. There is general agreement that cyanide is more toxic to freshwater fishes under conditions of low dissolved oxygen that pH levels within the range 6.8-8.3 have little effect on cyanide toxicity but enhance toxicity at more acidic pH that juveniles and adults are the most sensitive life stages and embryos and sac fry the most resistant and that substantial interspecies variability exists in sensitivity to free cyanide. Initial dose and water temperature both modify the biocidal properties of HCN to freshwater teleosts. At low lethal 

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Cyanide compounds are useful to society in terms of their key role in synthetic and industrial processes, for certain fumigation and agricultural uses, and for some therapeutic applications (Ballantyne and Marrs 1987). Cyanides are present in effluents from iron and steel processing plants, petroleum refineries, and metal-plating plants, and constitute a hazard to aquatic ecosystems in certain waste-receiving waters (Smith et al. 1979) and to livestock (USEPA 1980 Towill et al. 1978). Cyanide serves no useful purpose in the human body, yet it is present in our food, air, and water (Becker 1985). 

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