Effect of pH and chloride on nitrite-induced lethality in bluegill (Lepomis macrochirus)

Nitrite toxicity, expressed as a 48-hour LC50, was determined in bluegill exposed to four test environments involving combinations of low pH (4.0), high pH (7.2), low chloride (5.0 mg per litre) and high chloride (18:1 chloride:nitrite molar ratio). Lowering pH resulted in a dramatic increase in nitrite toxicity whereas chloride concentration had little or no effect. Explanation for the pH findings is based on the predominance of uncharged nitrous acid at low pH as opposed to nitrous ions at high pH. This also accounts for the inability of chloride to affect nitrite toxicity at low pH, but the lack of chloride effect at high pH was unexpected and the authors offer no firm explanation.