甲苯、乙苯和二甲苯对中华新米虾的毒性效应

以中华新米虾(Neocaridina denticulata sinensis)为受试生物,采用半静态生物测定方法,研究了TEX污染物对中华新米虾的单一急性毒性和联合毒性效应.在单一毒性试验中,甲苯、乙苯和二甲苯对中华新米虾的96h LC50分别为13.8,10.4,11.3mg/L,毒性大小顺序为乙苯>二甲苯>甲苯.基于等毒性溶液法(ETS)分析了TEX二元混合物的联合毒性,结果表明,甲苯-乙苯、乙苯-二甲苯与甲苯-二甲苯按不同毒性单位比(4:1,3:2,2:3,1:4)组成的二元混合物对中华新米虾的联合毒性作用均表现为相加作用.基于毒性单位法(TU)和混合毒性指数法(MTI)研究了甲苯-乙苯-二甲苯按浓度比1:1:1和毒性单位比1:1:1所组成的三元混合物对中华新米虾的联合毒性,96h LC50分别为11.6,10.7mg/L,毒性大小与3种苯系物单独作用相当.当暴露时间为48h时,联合毒性表现为部分相加作用,而暴露时间为96h时,联合毒性作用为协同作用,即随着暴露时间的增加,甲苯-乙苯-二甲苯组成的三元混合物的联合毒性从部分相加作用转变为协同作用,但是协同作用均不明显,非常接近于相加作用.因此,甲苯、乙苯和二甲苯对中华新米虾的联合毒性作用主要表现为相加作用.

Toxic effects of toluene, ethylbenzene and xylene on Neocaridina denticulata sinensis

Single and joint toxicity of toluene, ethylbenzene and xylene on Neocaridina denticulata sinensis was examined using the semi-static bioassay. In the single acute toxicity experiments, the 96h LC50 value of TEX was 13.8, 10.4, 11.3 mg/L, respectively, and the sequence of toxicity was in order of ethylbenzene>xylene>toluene. On the basis of the equal toxicity solution method (ETS), the binary action of binary of toluene, ethylbenzene and xylene in different toxic unit ratios (4:1, 3:2, 2:3, 1:4) on Neocaridina denticulata sinensis was analyzed. The results showed that the joint action between toluene and ethylbenzene, ethylbenzene and xylene, and toluene and xylene was strictly in conformity with the model of additivity. On the basis of the toxic unit method (TU) and the mixture toxicity index method (MTI), the ternary action of toluene, ethylbenzene and xylene by two different ways of combination (in toxic unit ratio 1:1:1 and in concentration ratio 1:1:1) on Neocaridina denticulata sinensis weas evaluated. The 96h LC50 value of the ternary mixtures was 11.6 and 10.7 mg/L, respectively, which was quite similar to the results in the single action so that could be also regarded as the medium toxicity toxicant. Besides, the results demonstrated that the joint action was considered as partial addition after a 48-h exposure and synergism after a 96-h exposure. Thus, the joint toxicity of the ternary mixtures turned out to be related to the exposure time, from partial addition to synergism. However, synergism observed was not significant, which meant that the joint action was close to additivity. In conclusion, the joint action of the binary and ternary mixtures of toluene, ethylbenzene and xylene on Neocaridina denticulata sinensis can be mainly assumed to be additive action. Therefore, when establishing the water quality guideline or criteria, controlling water pollution, and assessing aquatic ecosystem risk of toluene, ethylbenzene and xylene in the future, the additive action can be safely recommended.