Elevated concentrations of sulfate occur commonly in anthropogenically impacted and natural waters. However, water quality guidelines (WQG) have not been developed in many jurisdictions, and chronic toxicity data are scarce for this anion. A variety of test organisms, including species of invertebrate, fish, algae, moss, and an amphibian, were tested for chronic toxicity to develop a robust dataset that could be used to develop WQGs. As an example of how these data might be used to establish guidelines, calculations were performed using two standard procedures: a species sensitivity distribution (SSD) approach, following methods employed in developing Canadian WQGs, and a safety factor approach, according to procedures typically used in the development of provincial WQGs in British Columbia. The interaction of sulfate toxicity and water hardness was evaluated and incorporated into the calculations, resulting in separate values for soft (10-40 mg/L), moderately hard (80-100 mg/L) and hard water (160-250 mg/L). The resulting values were 129, 644, and 725 mg/L sulfate, respectively, following the SSD approach, and 75, 625, and 675 mg/L sulfate, following the safety factor approach.

Abstract-Assessment of total dissolved solids (TDS) represents an integrated measure of the concentrations of common ions (e.g., sodium, potassium, calcium, magnesium, chloride, sulfate, and bicarbonate) in freshwaters. Toxicity related to these ions is due to the specific combination and concentration of ions and is not predictable from TDS concentrations. Short-term chronic toxicity tests were conducted with larval chironomids and trout (eggs and swim-up fry) to assess their TDS tolerance relative to effluents from two Alaskan mines. Both effluents are characterized by high TDS content but differ with respect to concentrations of specific ions and alkalinity. The toxicity tests were conducted with synthetic effluents formulated to match the ionic composition of each mine discharge. No toxicity was observed at Ͼ2,000 mg of TDS/L with embryos or developing fry, but chironomids exhibited effects above 1,100 mg of TDS/L. These tests, together with information on the health of field populations (fish and benthic invertebrates), are appropriate and relevant for determining site-specific whole effluent TDS concentrations.

A method for conducting short‐term (7 day) embryo toxicity tests with rainbow trout is described. The test uses an easily recognizable endpoint that incorporates fertilization success, embryo mortality, and morphogenesis. Method validation included 26 tests on pulp and paper mill effluents and 10 tests with the reference toxicant sodium dodecyl sulphate. The results demonstrate that the method is sensitive and reproducible. Sensitivity, as measured by the minimum statistically significant response, averaged 15.5% of the control performance. Control embryo viability averaged 90% over 36 tests, indicating that the test procedures are robust with low probability of failure. Reference toxicant test results suggested that the short‐term embryo toxicity tests were appreciably more sensitive than 96 h acute tests with juvenile rainbow trout and 7 day fathead minnow larval survival and growth tests. This test offers the potential for conducting routine toxicity tests where cold water salmonids are the species of interest and it is desirable to use a more sensitive measure of effects than a 96 h LC50 acute toxicity test with juvenile fish. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 301–307, 1999

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