INFLUENCE OF SOME ABIOTIC FACTORS ON THE ACUTE TOXICITY OF C MIUM TO CYPRINUS CARPIO
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Abstract
Hardness of water had significant effect on the acute toxicity of cadmium
to common carp, Cyprinus carpio. The 96h LC50 and safe application rate
increased from 43.17 and 22.77 mg 14 in soft water (0.9 mill Ca2' 14) to 310.48
and 177.66 mg I', respectively, in very hard water (6.0 mM Ca 2+14). In medium
hard and hard water, 96h LC 50 values were 48.39 and 116.45 mg 14. When
sediments were included in the medium hard, hard and very hard water
treatments, the 96h LC 50 were 111.20, 133.71 and 334.47 mg respectively.
Among these values, the one for medium hard water with sediment treatment
was significantly higher than medium hard water treatment; values for the
other two treatments were non-significant when compared with respective
water treatments. Sediment was able to reduce the acute toxicity of cadmium
mainly due to the complexation of cadmium with dissolved organic carbon
(DOC). At the lower hardness level, cadmium complexed with DOC and the
acute toxicity was reduced significantly. At higher hardness, most of the
DOC sites were occupied by calcium and the acute toxicity of cadmium was
not significantly reduced in hard water with sediment and very hard water
with sediment experiments in comparison to respective water treatments.
Keywords: Cadmium, hardness of water, sediment, Cyprinus carpio