AN AQUATIC TOXICOLOGICAL EVALUATION OF SULFATE THE CASE FOR CONSIDERING HARDNESS AS A MODIFYING FACTOR IN SETTING WATER QUALITY GUIDELINES

Elevated concentrations of sulfate occur commonly in anthropogenically impacted and natural waters However water quality guideline s (WQG) have not been developed in many jurisdictions and chronic toxicity data at e 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 WQG, 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 Environ Toxicol Chem 2011 30 247-253 (C) 2010 SETAC