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PT13 Aquatic Ecotoxicology I
(PT211) Effects of hardness and chloride on the acute toxicity of sulfate to freshwater invertebrates.
Soucek, D1, 1 Illinois Natural History Survey, Champaign, IL, USA
ABSTRACT- Forty eight- or 96-hour LC50s were generated for Ceriodaphnia dubia, Chironomus tentans, Hyalella azteca, and Sphaerium simile using sodium sulfate (Na2SO4) dissolved in moderately hard, reconstituted water (MHRW) with the intention of determining a sulfate standard for the protection of aquatic life in Illinois. The mean LC50s, expressed as mg SO42-/L, for the four organisms in MHRW were as follows: 512 mg/L for H. azteca, 2,050 mg/L for C. dubia, 2,078 mg/L for S. simile, and 14,134 mg/L for C. tentans. Additional tests were conducted to determine the effects of chloride concentration, and water hardness on the acute toxicity of sulfate. When chloride was increased incrementally from 5 to 67 mg/L with hardness (106 mg/L) and sulfate (2,800 mg/L) held constant, percent survival of H. azteca increased from 20 to 100%. Hardness also had an effect on the toxicity of sulfate to C. dubia and H. azteca. In tests with C. dubia at hardness values ranging from 90 to 484, LC50s increased from 2,050 mg/L at hardness = 90 to 3,516 mg/L at hardness = 484. Using a Reformulated Moderately Hard Reconstituted Water (RMHRW) with a similar hardness but higher chloride concentration and different calcium to magnesium ratio than that in MHRW, the mean LC50 for H. azteca (2,836mg/L) was nearly 5.5 fold higher than that generated using MHRW (512 mg/L). For C. dubia, the mean LC50 increased from 2,050 mg/L in MHRW to 2,526 mg/L in RMHRW.
Key words: total dissolved solids, sulfate, osmoregulation
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