Accumulation, distribution, and toxicity of copper in sediments of catfishponds receiving periodic copper sulfate applications

Copper sulfate (CuSO4) is applied periodically to commercial channel catfis h (Ictalurus punctatus) ponds as an algicide or parasit icide. Current unde rstanding of the chemistry of copper in soil-water systems suggests that co pper may accumulate in pond sediments, although the forms and potential bio availability of copper in catfish pond sediments are not known. This study investigated the accumulation and distribution of copper in the sediment of catfish ponds receiving periodic additions of CuSO4 . 5H(2)O. All ponds we re constructed in Sharkey (very-fine, smectitic, thermic Chromic Epiaquert) soil. Nine 0.40 ha ponds received 59 applications of 2.27 kg CuSO4 . 5H(2) O per application per pond over 3 yr; no CuSO4 . 5H(2)O applications were m ade to nine additional ponds. Total Cu concentration in the sediments of Cu SO4 . 5H(2)O-amended catfish ponds (172.5 mg kg(-1)) was four to five times higher than that in the sediments of nonamended ponds (36.1 mg kg(-1)). Co pper accumulated in catfish pond sediments at a rate of 41 mug kg(-1) dry s ediment for each 1 kg ha(-1) of CuSO4 . 5H(2)O applied to ponds. Copper in the sediments of amended ponds was mainly in the organic matter-bound (30.7 %), carbonate-bound (31.8%), and amorphous iron oxide-bound (22.1%) fractio ns with a considerable fraction (3.4%; 3 to 8 mg kg(-1)) in soluble and exc hange able fractions. This indicates that Cu accumulates differentially in various fractions, with proportionally greater initial accumulation in pote ntially bioavailable forms. However, toxicity bioassays with amphipods (Hya llela azteca) and common cattail (Typha latifolia L.) indicated that the ef fect of exposure to amended or nonamended pond sediments was not different.