摘要:
重金属和有机磷农药污染物在水域环境中普遍存在。以卤虫(Artemia salina)为受试生物,采用固定浓度比法,研究了重金属Zn、Cd与辛硫磷和敌百虫2种农药以毒性单位比为4:1、3:2、1:1、2:3和1:4构成的二元混合体系对卤虫的联合毒性,采用等效线图解法判定毒物间的相互作用类型。同时,基于单一化合物的浓度-效应曲线,运用浓度加和(CA)和独立作用 (IA)2种模型对不同配比二元混合物的联合毒性进行预测。结果表明,Zn-Cd混合物联合毒性随Zn比例的增加而增强。低 Zn比例的混合物(1:4、2:3)表现为拮抗效应,中、高Zn比例的混合物(1:1、3:2和4:1)为加和效应。5种不同配比的有机磷农药混合物均表现为加和效应。金属-农药混合物则均为拮抗作用。模型预测结果表明,CA能够较好地预测辛硫磷与敌百虫二元混合物的联合毒性,而IA则更适用于对金属-农药混合物联合毒性的预测。以上结果表明,混合体系中各组分的比例是影响联合毒性的因素之一,毒性评估时应该充分考虑其影响。CA及IA模型同样适用于评估和预测包含相同或完全独立作用机制组分的混合物对非单细胞生物体(如卤虫)的联合毒性。
Abstract:
Aquatic ecosystems are often suffered with a wide variety of chemical pollutants including heavy metals and pesticides. This study aimed to experimentally evaluate the joint toxicity of binary mixtures (prepared in predefined ratios of 4:1, 3:2, 1:1;2:3 and 1:4) of heavy metals (Zn and Cd) and organo phosphate pesticides (phoxim and dipterex) to saltwater crustacean Artemia salina. Additionally, the predictability of toxicity of the studied mixtures was investigated by concepts of concentration addition (CA) and independent action (IA), Isobologram method was used to assess the types of interaction. Toxicity modeling was based on the concentration response curves of the single substances. The obtained results revealed that no synergism was found in any of the tested combinations except that the joint toxicity of Zn-Cd mixtures was enhanced with increasing Zn/Cd ratios. With the Zn to Cd ratios increased, the interaction types changed from antagonism at lower Zn to Cd ratios (1:4 and 2:3) to additivity at higher Zn to Cd ratios (1:1, 3:2 and 4:1). Five organophosphate pesticide mixtures showed additive effect, while that of the metal pesticide mixtures were antagonism. In the estimating mixture toxicity, CA accurately described the joint effect of phoxim and dipterex, and IA provided accurate predictions for the mixtures involving metals and organophosphate pesticides. These findings imply that mixture ratios should be taken into account as a factor in mixture toxicity studies. Additionally, CA and IA are reasonable tools for the predictive hazard assessment of mixtures that contain components with similar or completely independent action mechanism against complex organisms such as A. salina.
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