Evaluation of the effect of water type on the toxicity of nitrate to aquatic organisms.
A suite of acute and chronic toxicity tests were conducted to evaluate the sensitivity of freshwater organisms to nitrate (as sodium nitrate). Acute exposures with rainbow trout (Onchorhynchus mykiss) and amphipods (Hyalella azteca), as well as chronic exposures with H. azteca (14-d survival and growth), midges (Chironomus dilutus; 10-d survival and growth), daphnids (Ceriodaphnia dubia; 7-d survival and reproduction), and fathead minnows (Pimephales promelas; 7-d survival and growth) were used to determine sublethal and lethal effect concentrations. Modification of nitrate toxicity was investigated across a range of ionic strengths, created through the use of very soft water, and standard preparations of synthetic soft, moderately-hard and hard dilution waters. The most sensitive species tested were C. dubia and H. azteca, in soft water, with reproduction and growth IC25 values of 13.8 and 12.2 mg/L NO3-N, respectively. All of the organisms exposed to nitrate demonstrated significantly reduced effects with increasing ionic strength associated with changes in water type. Possible mechanisms responsible for the modifying effect of increasing major ion concentrations on nitrate toxicity are discussed.
Nautilus Environmental, 8664 Commerce Court, Burnaby, BC, V5A 4N7, Canada. Electronic address: josh@nautilusenvironmental.ca.
Josh A
JA
Baker
Borealis Environmental Consulting, 148 East 25th Street, North Vancouver, BC, V7N 1A1, Canada.
Guy
G
Gilron
The Mining Association of Canada, 350 Sparks Street, Suite 1105, Ottawa, ON, K1R 7S8, Canada.
Ben A
BA
Chalmers
Nautilus Environmental, 8664 Commerce Court, Burnaby, BC, V5A 4N7, Canada.
James R
JR
Elphick
D033304:Amphipoda / Q000187:drug effects / Q000254:growth & development; D000818:Animals; D002683:Chironomidae / Q000187:drug effects / Q000254:growth & development; D033361:Cladocera / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D003530:Cyprinidae / Q000254:growth & development; D009566:Nitrates / Q000633:toxicity*; D017686:Oncorhynchus mykiss; D009994:Osmolar Concentration; D012098:Reproduction / Q000187:drug effects; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D009566:Nitrates; D014874:Water Pollutants, Chemical; D014867:Water; C031618:sodium nitrate
Anions; Hardness; Modifying factor; Nitrate; Toxicity