抗生素与杀菌剂顺序暴露对绿藻的联合毒性

本文选取常见的3种抗生素盐酸强力霉素(DOX)、红霉素(ERY)、土霉素(OXY)和3种三唑类杀菌剂腈菌唑(MYC)、丙环唑(PRO)、戊唑醇(TCZ)混合体系为研究对象,以生态系统中初级生产者绿藻(蛋白核小球藻)为受试生物,研究目标污染物顺序暴露的联合毒性.结果表明,6种单一目标污染物对蛋白核小球藻抑制毒性大小为:PRO>DOX>TCZ>ERY>MYC>OXY.抗生素-三唑类杀菌剂混合体系在50%效应浓度(EC_(50))下同时暴露和顺序暴露的抑制率差异为0.38%~36.76%.DOX与PRO、TCZ、MYC任何一种三唑类杀菌剂顺序暴露于蛋白核小球藻,顺序相反后,对蛋白核小球藻的毒性作用均增强,最大可增强36.82%.在不同浓度与时间的影响下,PRO-DOX和TCZ-DOX顺序暴露毒性高于调整暴露顺序后的DOX-PRO和DOX-TCZ顺序暴露毒性,且浓度越高,抑制率差异越大.在96h~144h暴露时间下,暴露浓度EC_(50)/20的顺序暴露抑制率差异为0.65%~11.57%;暴露浓度EC_(50)的顺序暴露抑制率差异为0.15%~36.93%,顺序暴露的抑制率差异范围随浓度增加变大.在EC_(50)/20~EC_(50)暴露浓度下,暴露时间96h的顺序暴露抑制率差异为0.29%~36.93%,暴露时间144h的顺序暴露抑制率差异为0.215%~30.09%,顺序暴露的抑制率差异范围随时间增加变小.因此,顺序暴露会改变抗生素与三唑类杀菌剂对蛋白核小球藻联合毒性大小,且顺序暴露、暴露时间和暴露浓度是影响毒性作用大小的关键因素.

桂林会仙岩溶湿地水体中有机氯农药分布特征及混合物环境风险评估

为研究桂林会仙岩溶湿地水体中有机氯农药(OCPs)的残留水平、分布特征、来源和环境风险,分别于2016—2017年四个季节在研究区域采集地表水(湖泊和沟渠水)和浅层地下水样品共88份,利用气相色谱法(GC-ECD)对其中15种OCPs残留量进行检测和相关分析。结果表明,会仙湿地湖泊、沟渠和浅层地下水中总OCPs残留量范围(平均值)分别为68.7~305 ng·L^(-1)(137 ng·L^(-1))、77.4~211 ng·L^(-1)(137 ng·L^(-1))和24.6~76.4 ng·L^(-1)(38.6 ng·L^(-1)),其中六六六(HCHs)是最主要的污染物,占总OCPs的61.7%以上,其次是七氯类OCPs和滴滴涕(DDTs)。与国内外其他地区水体OCPs污染相比,研究区域地表水OCPs污染处于较高水平,浅层地下水OCPs污染处于中等水平,同时夏季OCPs残留浓度高于其他季节。从特征组分比例可确认HCHs主要来自历史残留,但2016年10月可能有新的林丹输入;DDTs降解不完全,可能有持续输入。OCPs混合物风险评估结果表明甲壳类对研究区域水体中15种OCPs最敏感,其次为鱼类和藻类;15种OCPs混合物对浅层地下水水生生态环境具有中等风险,而对地表水水生生态环境具有高风险。

具有Hormesis效应抗生素对斜生栅藻的毒性效应及主成分分析

为了研究不同暴露时间对磺胺甲恶唑(SMX)、盐酸强力霉素(DXC)、磺胺二甲嘧啶(SMZ)生态毒性效应的影响,选取斜生栅藻(Scenedesmus obliquus)作为受试生物,采用4和8 d 2个不同的暴露时间节点,对其进行毒性实验,以斜生栅藻的生长情况、生化指标为基础进行毒性评估。结果表明:这3种抗生素均具有Hormesis效应特性,藻细胞体内的可溶性蛋白含量与其对应的时间-剂量-效应曲线一致,呈刺激效应。考察了不同暴露时间(4和8 d)对藻细胞体内的过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、丙二醛(MDA)及光合作用指标(叶绿素a、叶绿素b和类胡萝卜素)的影响。结果表明:抗生素胁迫斜生栅藻在不同的暴露时间,抗氧化酶SOD、CAT随浓度增加的变化趋势具有差异性;MDA含量与生长抑制率呈正相关,其对应的MDA含量的最低值:SMX暴露4 d为1.76 nmol/mL,8 d为1.33 nmol/mL;DXC暴露4 d为13.69 nmol/mL,8 d为1.33 nmol/mL;SMZ暴露4 d为5.92 nmol/mL,8 d为1.75 nmol/mL;藻细胞体内的叶绿素a和类胡萝卜素含量与生长抑制率呈负相关。主成分分析法研究表明,不同暴露时间下受试抗生素对斜生栅藻毒性作用的良好表征指标。研究结果对水环境中抗生素生态风险评估具有重要的现实意义。

QSAR Models for Predicting Additive and Synergistic Toxicities of Binary Pesticide Mixtures on Scenedesmus Obliquus

Pesticides released into the environment may pose potential risks to the ecological system and hu-man health.However,existing toxicity data on pesticide mixtures still lack,especially regarding the toxic interac-tions of their mixtures.This study aimed to determine the toxic interactions of binary mixtures of pesticides on Scenedesmus Obliquus(S.obliquus)and to build quantitative structure-activity relationship models(QASR)for predicting the mixture toxicities.By applying direct equipartition ray method to design binary mixtures of five pes-ticides(linuron,dimethoate,dichlorvos,trichlorfon and metribuzin),the toxicity of a single pesticide and its mix-ture was tested by microplate toxicity analysis on S.obliquus.The QASR models were built for combined toxicity of binary mixtures of pesticides at the half-maximal effective concentration(EC_(50)),30%maximal effective concen-tration(EC_(30))and 10%maximal effective concentration(EC_(10)).The results showed that the single toxicity follows:metribuzin>linuron>dichlorvos>trichlorfon>dimethoate.The mixtures of linuron and trichlorfon,dichlorvos and metribuzin,dimethoate and metribuzin induced synergetic effects,while the remaining binary mixtures exhib-ited additive.The developed QSAR models were internally validated using the leave-one-out cross-validation(LOO),leave-many-out cross-validation(LMO),bootstrapping,and y-randomization test,and externally validated by the test sets.All three QSAR models satisfied well with the experimental values for all mixture toxicities,and presented high internally(R^(2)and Q^(2)>0.85)and externally(Q^(2)_(F1),Q^(2)_(F2),and Q^(2)_(F3)>0.80)predictive powers.The developed QSAR models could accurately predict the toxicity values of EC_(50),EC_(30)and EC_(10)and were superior to the concentration addition model's results(CA).Compared to the additive effect,the QSAR model could more ac-curately predict the binary mixture toxicities of pesticides with synergistic effects.

Study of the Binding Mode of Quaternary Ammonium Cationic Surfactant to Firefly Luciferase and the Prediction of Binary Mixture Toxicity

The wide use of quaternary ammonium cationic surfactants(QACs)results in their release into the environment.Most surfactants have significant biotoxicity.However,existing toxicity data on QACs are still lacking,especially regarding the joint toxic effects of their mixtures.In computer simulation technology,molecular docking technology is commonly used for studying the mode of action of receptors docking with ligands.The research of QACs mixture interaction is relatively rare,and the binding mode of QACs is unknown.In this study,molecular docking technology was applied to explore the QAC binding mode,and the concentration addition(CA)and independent action(IA)models were applied for predicting the mixture toxicity.Firefly luciferase(FLuc)was used as a macromolecular receptor,and five typical QACs:benzalkonium bromide(BLB),tetraethylammonium bromide(TLB),N,N,N-trimethyl-1-tetradecyl ammonium bromide(CTE),tetrabutylammonium chloride(TAC),and dodecyltrimethylammonium chloride(DTC)were used as small molecule ligands.Molecular docking technology was used to investigate the binding mode of macromolecules and small molecules.The luminescence inhibitory effects of individual compounds and binary mixture on FLuc were determined by microplate toxicity assay of luciferase.The prediction of mixture toxicity was performed by CA and IA.The results showed that the relative toxicity follows:TLB<TAC<DTC<BLB<CTE.TLB and TAC showed the BS-Ⅱbinding mode,and BLB,CTE and DTC showed the BS-Ⅲbinding mode.The toxicity of compounds with binding mode BS-Ⅱwas less than that of those with BS-Ⅲbinding mode.Not all mixtures with the same binding mode could be predicted by CA model,and the IA model did not effectively predict the toxicity of mixtures with compound with different binding modes.The mixture toxicities of QACs with the same binding mode mostly presented additive and synergistic effects,while the mixture toxic effects of QACs with different binding modes presented additive or antagonistic effects.