Toxicity of p-NP on Chlorella vulgaris and Scenedesmus obliquus at different pH levels

In order to study the environmental criteria of typical organic contaminants in aquatic systems,the influence of environmental factors on their biological effects was considered.End points of growth rate(μ),NOEC,LOEC and EC50 were selected as evaluation indices to study the growth of Chlorella vulgaris and Scenedesmus obliquus,and the p-nitrophenol(p-NP) toxicity to them at pH levels 7,8 and 9.The results showed that both Chlorella vulgaris and Scenedesmus obliquus could grow well at the range of pH 7-9,but the most suitable pH condition was different for each of them.Chlorella vulgaris grew best at pH 8,while Scenedesmus obliquus grew best at pH 9.The toxicity of p-NP to Chlorella vulgaris and Scenedesmus obliquus decreased with increasing pH,and the least toxic effect was observed at pH 9.The p-NP was more toxic to Scenedesmus obliquus than Chlorella vulgaris,that is,Scenedesmus obliquus was more sensitive to the toxicity of p-NP than Chlorella vulgaris.Therefore,the influence of pH should be considered when an aquatic ecological criteria of p-NP are selected.