有机磷农药对蛋白核小球藻的毒性相互作用研究

水体中农药复合污染产生的毒性效应具有潜在风险。为系统考察有机磷农药(OPs)混合物对淡水生态系统中绿藻的联合毒性效应,以马拉硫磷(MIT)、敌敌畏(DDVP)、敌百虫(TRC)、乐果(DIT)和氧乐果(OMT)等5种OPs作为混合物组分,运用直接均分射线法设计9组二元混合物体系共45条混合物射线。利用96孔微板测定5种OPs及其二元混合物对蛋白核小球藻(C. pyrenoidosa)的生长抑制毒性,通过基于置信区间的组合指数法分析混合物的联合毒性及毒性相互作用。结果表明,以p EC50为毒性指标,5种OPs对C. pyrenoidosa的毒性大小顺序为:TRCMITDDVPOMTDIT,OPs对C. pyrenoidosa的毒性大小受其中心磷原子的电正性影响;因混合组分的不同,部分OPs混合物对C. pyrenoidosa的联合毒性依赖于组分浓度比; OPs混合物对C. pyrenoidosa的毒性相互作用以加和为主,部分发生拮抗作用,发生拮抗作用的混合体系具有低效应区域呈加和作用,高效应区域呈拮抗作用的规律;与MIT混合的体系均有发生拮抗作用,且依赖于MIT浓度,MIT浓度比例越高,拮抗作用越强,OPs混合物的毒性相互作用与组分浓度比相关; OPs混合物的毒性相互作用组分浓度比依赖性与其联合毒性的组分浓度比依赖性规律不相关。

Toxicological Interactions of Organophosphorus Pesticides Mixtures to Chlorella pyrenoidosa

The toxicity effects of combined pesticides pollution have potential risks to aquatic environment. To investigate the combined toxicity effects of organophosphorus pesticides (OPs) mixtures on green algae in freshwater ecosystems, five OPs, i.e. malathion (MIT), dichlorvos (DDVP), trichlorfon (TRC), dimethoate (DIT) and omethoate (OMT), were selected as the mixture components. Nine OPs binary mixture systems contained 45 mixture rays were designed by a direct equipartition ray design (EquRay) method. The growth inhibition toxicities of the five single OPs and 45 binary mixture rays to Chlorella pyrenoidosa (C. pyrenoidosa) were determined using the 96-well microplate. Combination index based on the confidence intervals method was applied to analyze the toxicological interactions in OPs binary mixtures. Taking the negative logarithm of median effective concentration (pEC₅₀) as toxicity index, the toxicity order of five OPs was as follows: TRC>MIT>DDVP>OMT>DIT. The toxicity of single OPs to C. pyrenoidosa was affected by the electropositivity of its phosphorus. The combined toxicity of some OPs mixtures depended on component concentrations. The toxicological interactions of OPs mixtures on C. pyrenoidosa were dominated by additive action, and some mixtures presented antagonism behavior. In addition, the mixture systems with antagonism displayed additive effects at low-effect regions and showed antagonistic effects at high-effect regions. The antagonism of the mixture systems containing MIT were strengthened with the increasing of MIT concentration ratio. It was worth noting that the toxicological interactions of OPs mixtures were related to component concentration ratio. Meanwhile, the concentration-ratio-dependent interactions of OPs mixtures were not associated with their concentration-ratio-dependent toxicity.