中文摘要：

越来越多的研究表明，污染物在不同暴露时间具有不同的毒性变化规律。以4种氨基糖苷类抗生素，硫酸安普霉素（APR）、双氢链霉素(DIH)、硫酸新霉素(NEO)和硫酸链霉素(STS)为混合物组分，应用直接均分射线法和均匀射线法对4类抗生素设计出6组二元混合体系和4组三元混合体系，每个混合物体系设计5条射线共50条射线，采用时间毒性微板分析法(T-MAT)测定这些抗生素混合物射线在6个暴露时间点(即0、12、24、48、72和96h)对蛋白核小球藻(C.pyrenoidosa)的生长抑制毒性。结果表明，抗生素二元和三元混合物系的50条射线对C.pyrenoidosa毒性均具有明显的时间依赖性，即混合物射线的毒性随着暴露时间的延长而增强；以半数效应浓度(EC50)的负对数pEC50为毒性指标，不同混合物体系的时间毒性变化规律不同，有的混合物从0h开始，毒性随时间延长逐渐增强，有的从12h或24h，甚至48h后，毒性开始迅速增加；同一混合物体系中不同射线的毒性因组分浓度比的变化而变化，即混合物射线的毒性随毒性大的组分比例增加而增强。

英文摘要：

More and more researches published have shown that some pollutants have different toxicitychanging laws at different exposure times. Four aminoglycoside antibiotics including apramycin sulfate,dihydrostreptomycin sesquisulfate, neomycin sulfate and strepomycin sulfate being selected as the mixture components, six binary and four ternary mixture systems (containing fifty rays in all) were designed by the direct equipartition ray design and uniform design ray methods, respectively. The toxicities of the fifty rays in six binary and four ternary mixture systems to Chlorella pyrenoidosa were determined by using the timedependent microplate toxicity analysis (T-MAT) method at six different exposure times such as 0, 12, 24,48, 72 and 96 h. The results showed that all the fifty mixture rays exhibited clear time-dependent toxicity,i.e. toxicity increased with time lengthening. Selecting the negative logarithm of mean effect concentration (pEC50) value as a toxicity index, toxicity changing laws of different mixture systems varied with the exposure time lengthening. Toxicities of some mixture rays gradually increased from the exposure time of 0 h, while the toxicities of other mixture rays gradually or rapidly increased after 12 h or 24 h, even 48 h. The pEC50 values of different rays in the same mixture system changed with the mixture ratios of the component with higher toxicity, i.e., the toxicity of a mixture ray increased with the increasing of mixture ratios of the component with higher toxicity.