[Toxicity of nitrification substrates and products to photobacterium].

OBJECTIVE: In this study, we studied the toxic effect of nitrification substrates and products on photobacterium. METHODS: The acute toxicities of nitrification substrates and products to photobacterium were studied with the 15-min half inhibitory concentration (IC50) as indicator at pH = 7.0. RESULTS: The results of individual toxicity indicated that the toxicity of nitrification substrates and products to photobacterium increased with increasing concentration and there was a linear correlation. The IC50 values of ammonium, hydroxylamine, nitrite and nitrate were 2180.2 mg/L, 6.2740 mg/L, 1207.2 mg/L and 3140.3 mg/ L, respectively, and their toxic order was hydroxylamine > nitrite > ammonium > nitrate. The combined effects of substrates and products were assayed by equivalent concentration mixing method. The results showed that the combined effects of ammonium and hydroxylamine, ammonium and nitrite, hydroxylamine and nitrite were additive effects, whereas the combined effects of ammonium and nitrate, hydroxylamine and nitrate, nitrite and nitrate were independent effects. The combined effect of all nitrification substrates and productions was also additive effect. CONCLUSION: According to the correlation of the inhibiting concentration to photobacterium and nitrifying bacterium by nitrification substrates and products, the change of luminous intensity of photobacterium can indicate the inhibition from nitrification substrates and products.