Evaluation of the Joint Aquatic Toxicity of PNCB, MDNB and CDNB Acting on Brocarded Carp (Cyprinus Carpio)

In order to study the eco-toxicological combined effects of nitroaromatics compounds, joint toxicity test was used for examining the responses of aquatic organisms to three combination mixtures of most abundantly used nitroaromatics compounds in China, namely, para-nitrochlorobenzene (PNCB), m-dinitrobenzene (MDNB) and l-chloro-2,4-dinitrobenzene (CDNB). Brocarded carp was exposed to various concentrations of binary mixtures of three nitroaromatics compounds for 96 h. Four evaluation approaches (toxic units, additional Index, mixture toxic index and similarity parameter) were applied to evaluate the joint toxicity of three chemicals to Brocarded Carp. The results indicated that the joint action of PNCB and MDNB to fish was antagonistic action in 48 h and then was synergistic effect after 48 h. The joint toxicity effect of MDNB with CDNB was synergistic action on Brocarded carp. However, the binary mixtures action of PNCB with CDNB was antagonism when the chemicals were mixed by equi-toxicity ratios. The results show that joint toxicity of binary mixtures was more dependent on the exposure duration. The combined effect of binary mixtures having the same quantities of substituents would exceed the effect found for each of the compounds tested separately, and it was significantly strengthened compared with individual compound toxicities when they were co-existed in the water.