Evaluation of ionic contribution to the toxicity of a coal-mine effluent using Ceriodaphnia dubia.
The United States Environmental Protection Agency has defined national in-stream water-quality criteria (WQC) for 157 pollutants. No WQC to protect aquatic life exist for total dissolved solids (TDS). Some water-treatment processes (e.g., pH modifications) discharge wastewaters of potentially adverse TDS into freshwater systems. Strong correlations between specific conductivity, a TDS surrogate, and several biotic indices in a previous study suggested that TDS caused by a coal-mine effluent was the primary stressor. Further acute and chronic testing in the current study with Ceriodaphnia dubia in laboratory-manipulated media indicated that the majority of the effluent toxicity could be attributed to the most abundant ions in the discharge, sodium (1952 mg/L) and/or sulfate (3672 mg/L), although the hardness of the effluent (792 +/- 43 mg/L as CaCO3) ameliorated some toxicity. Based on laboratory testing of several effluent-mimicking media, sodium- and sulfate-dominated TDS was acutely toxic at approximately 7000 microS/cm (5143 mg TDS/L), and chronic toxicity occurred at approximately 3200 microS/cm (2331 mg TDS/L). At a lower hardness (88 mg/L as CaCO3), acute and chronic toxicity end-points were decreased to approximately 5000 microS/cm (3663 mg TDS/L) and approximately 2000 microS/cm (1443 mg TDS/L), respectively. Point-source discharges causing in-stream TDS concentrations to exceed these levels may risk impairment to aquatic life.
Kennedy
A J
AJ
Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA. alan.j.kennedy@erdc.us-ace.army.mil
Cherry
D S
DS
Zipper
C E
CE
D000818:Animals; D002713:Chlorine / Q000633:toxicity; D003032:Coal Mining; D003621:Daphnia / Q000187:drug effects* / Q000254:growth & development; D005618:Fresh Water / Q000737:chemistry*; D007477:Ions / Q000633:toxicity*; D012964:Sodium / Q000633:toxicity; D012996:Solutions; D013431:Sulfates / Q000633:toxicity; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D007477:Ions; D012996:Solutions; D013431:Sulfates; D014874:Water Pollutants, Chemical; D002713:Chlorine; D012964:Sodium