By P.H. Davies, J.P. Goettl Jr., J.R. Sinley, N.F. Smith
Water Research, Volume 10, Issue 3, 1976, Pages 199-206, ISSN 0043-1354, DOI: 10.1016/0043-1354(76)90128-7.

Lead was found to be highly toxic to rainbow trout in both hard water (hardness 353 mg l-1 as CaCO3) and soft water (hardness 28 mg l-1. Analytical results differ greatly with methods of analysis when measuring concentrations of lead in the two types of water. This is exemplified in LC50's and maximum acceptable toxicant concentrations (MATC's) obtained when reported as dissolved lead vs total lead added in hard water. Two static bioassays in hard water gave 96-h LC50's of 1.32 and 1.47 mg l-1 dissolved lead vs total lead LC50's of 542 and 471 mg l-1, respectively. In a flow-through bioassay in soft water a 96-h LC50 of 1.17 mg l-1, expressed as either dissolved or total lead, was obtained. From chronic bioassays, MATC's of lead for rainbow trout in hard water were between 18.2 and 31.7 [mu]g l-1 dissolved lead vs 120-360 [mu]g l-1 total lead. In soft water, where exposure to lead was initiated at the eyed egg stage of development, the MATC was between 4.1 and 7.6 [mu]g l-1. With exposure to lead beginning after hatching and swim-up of fry, the MATC was between 7.2 and 14.6 [mu]g l-1. Therefore, fish were more sensitive to the effects of lead when exposed as eggs.

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