Change in the antimicrobial resistance profile of Pseudomonas aeruginosa from soil after exposure to herbicides

The extensive use of pesticides represents a risk to human health and to the environment. This study aimed to investigate if the exposure to atrazine and diuron, two herbicides widely used in Brazil, could induce changes in the susceptibility profile to aztreonam, colistin and polymyxin B antimicrobials in isolates of P. aeruginosa obtained from soil samples by using the determination of minimum inhibitory concentration (MIC) test. Three isolates had an increase of MIC to aztreonam after exposure to both herbicides and one isolate did not show any MIC change. The MexAB-OprM efflux pump has already been upregulated in these isolates and the herbicides atrazine and diuron did not increase MexAB-OprM overexpression. Therefore, the decrease in aztreonam susceptibility was not directly related to this pump, suggesting that probably other mechanisms should be involved.     

36种典型除草剂对绿藻的毒性研究

近年来,农药对生态系统的初级生产者——藻类的毒性及其生态毒理学研究引起了国内外学者的广泛关注。除草剂在生产中广泛应用,对藻类的毒性作用最强,其毒性效应远高于杀虫剂和杀菌剂。论文选择市场上具有典型代表性的36种除草剂原药,分析解读除草剂在国内的登记情况,以及在作物、旱田和水田的使用情况;明晰对藻类生长抑制急性毒性效应。结果表明:1)除草剂的作用方式和化学类别对绿藻毒性影响显著;对于抑制植物细胞分裂和作用于植物叶绿体的除草剂对绿藻毒性均较高,以人工合成植物生长素为代表的除草剂对绿藻毒性均较低;2)相同作用方式,不同化学类别的除草剂,对单一绿藻的毒性差异明显。在水稻上获得登记的除草剂对藻类毒性整体低于在旱田获得登记的除草剂对藻类的毒性。开展多种农药对水生生态毒性的研究,为农药的合理安全使用、农药在淡水环境中的生态效应评价以及保护淡水生态系统提供科学依据。     

3种酰胺类除草剂对斑马鱼不同生长阶段的急性毒性效应

为探明酰胺类除草剂对鱼类不同生长阶段的毒性效应,分别以斑马鱼胚胎、8日龄仔鱼、55日龄幼鱼和3月龄成鱼为受试对象,研究3种酰胺类除草剂乙草胺、丙草胺和丁草胺对斑马鱼(Danio rerio)不同生长阶段的毒性效应。研究发现,高浓度乙草胺、丙草胺和丁草胺均可抑制斑马鱼胚胎的孵化。乙草胺对斑马鱼胚胎、仔鱼、幼鱼和成鱼的96 h-LC50值分别为5.82、1.34、3.00、1.44 mg·L-1,毒性从高到低顺序依次为:仔鱼成鱼幼鱼胚胎。丙草胺对斑马鱼胚胎、仔鱼、幼鱼和成鱼的96 hLC50值分别为2.79、2.02、2.26、2.01 mg·L-1,毒性从高到低顺序依次为:仔鱼、成鱼幼鱼胚胎。丁草胺对斑马鱼胚胎、仔鱼、幼鱼和成鱼的96 h-LC50值分别为1.73、0.919、3.37、1.19 mg·L-1,毒性从高到低顺序依次为:仔鱼成鱼胚胎幼鱼。研究结果表明,酰胺类除草剂对斑马鱼4个典型生长阶段的毒性差异较大,仔鱼阶段对酰胺类除草剂最敏感,成鱼其次。     

Trends in Pesticide Use and Efficacy During 26 Years of Changing Agriculture in Southern England

We report on trends in agricultural pesticide use from1970 to 1995 inclusive in arable crops on the SouthDowns, West Sussex, U.K. Information is given on theproportion of cropped area treated with pesticides,the percentage spray area, the number of pesticideapplications per field, and the number of compoundsapplied per field for herbicides, foliar fungicidesand insecticides. Compared to national publishedfigures, our data are broadly representative of thenational picture; they provide a complete and detailedtime series whereas national figures are available foronly 7 out of the 26 yr. In general, the areatreated (fungicides, insecticides) and the intensityof use (all three types of pesticide) increased overthe 26 yr. The spectrum of activity of theherbicides applied to arable crops increased from anaverage of 22 weed taxa susceptible in 1970 to 38 weedtaxa susceptible in 1995. The odds on herbicide andfungicide use in break crops were, respectively, 93%and 99% lower than average; odds on insecticide usein spring cereals were 98% lower than average. Comparing winter wheat on the most traditional farm(grass/cereal rotation) with the most modern one(monoculture winter wheat), the proportion of fieldstreated with herbicides was similar, but the odds onbeing treated with fungicides were 129% higher on themodern farm. Insecticides were used in only 2% ofthe fields on the traditional farm, while on themodern farm over the same time period, 79% of thefields were treated. This fits previously observeddifferences in wildlife abundance on the two farms.     

乙草胺和丁草胺的水解及其动力学

本文研究了乙草胺和丁草肢在恒温２５℃,ｐＨ值为４,７,１０蒸馏水和河水中的水解动力学．酰胺类除草剂的水解反应属于一级反应．结果显示乙草胺和丁草胺在蒸馏水和河水中的水解速度差不多,在ｐＨ ４水溶液中的水解速度较在ｐＨ７和１０的速度快,Ｈ＋有催化水解的作用．乙草胺在ｐＨ４,７,１０的速率常数分别为５×ｌ０－４ｄ－１,３×１０－４ｄ－１,３×１０－４ｄ－１．半衰期分别为１３８６ｄ,２３ｌ０ｄ,２３１０ｄ．丁草胺在ｐＨ４,７,１０的速率常数分别为 ｌ．１× １０－３ｄ－１,６ × １０－４ｄ－１,６ × １０－４ｄ－１．半衰期分别为 ６３０ｄ,１１５５ｄ,１１５５ｄ．     

Colloid facilitated transport of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) to the groundwater at Ma Da Area, Vietnam

PCDD/Fs are hydrophobic organic substances and strongly sorbing to soil particles. Once adsorbed to soil particles they are believed to be virtually immobile. However, research in the last decades confirmed that strong sorbing contaminants may reach the groundwater via colloid-facilitated transport. This pathway has not been investigated before in Vietnam. Ma Da area, 100 km north of Ho Chi Minh City, was repeatedly sprayed during the Vietnam War (1962–1971) with herbicides like Agent Orange containing, beside others, the teratogenic contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). 11 surface soil samples and 12 water samples were collected in Ma Da area for analysis of PCDD/Fs in solids. Soil TCDD concentrations ranged from 1–41 ppt with a mean of 8.8 ppt and a mean I-TEQ of 9.7 ppt. Two surface water samples showed colloid bound TCDD (7 and 19 ppt). Groundwater samples showed elevated colloid bound PCDD concentrations (mean 770 ng/kg), mainly octachlorodibenzo-p-dioxin. Groundwater colloids separated by filtration did not show any TCDD. The results support that TCDD/Fs can be relocated from the top soil to the groundwater by colloidal pathway. They did not provide evidence that the dioxins bound to groundwater colloids are leftovers from the Second Indochinese War. However, this study reinforces that the colloidal transport pathway has to be included investigating the relocation of strong sorbing organic contaminants.     

吹脱+A/O工艺处理氮肥企业高氨氮废水的工程实践

针对河南某氮肥企业高氨氮废水采用吹脱+A/O工艺处理的成功实践(当进水氨氮浓度在641～868mg/L时,出水始终稳定在1mg/L左右),分析了工程设计与调试中应注意的问题,可供此类污水处理工程设计参考。     

在中型氮肥厂推行清洁生产

在对合成氨厂污染源调查的基础上,通过对尿素解吸塔的改造、铜洗稀氨水的增浓、氨吸塔含氨废水的循环利用、氨泵密封水的回收,减少了生产过程中污染物－氨氮的产生量,并取得了显著的经济效益。     

高藻水臭氧预氧化过程有机物转化及消毒副产物生成势

研究了高藻水预氧化处理过程中,不同臭氧氧化程度及不同pH值条件下,藻类有机物释放与转化规律以及氯化消毒副产物(DBPs)的生成特性.结果表明,臭氧投加量为28.92 mg·L-1时藻去除率达36%.随着臭氧投加量的增加,藻的去除率进一步增加,类腐殖酸先增加后持续减少,溶解性微生物代谢产物、类富里酸和类芳香蛋白物质持续减少;低投加量的臭氧对二氯乙腈(DCAN)、三氯乙腈(TCAN)生成势有明显的控制作用,但会增加三氯硝基甲烷(TCNM)以及1,1,1-三氯丙酮(1,1,1-TCP)前体物,随臭氧投加量增大,DBPs生成势显著增大.酸性条件下臭氧对藻的去除效果最好,UV254以及总有机碳(DOC)均随pH的增大有所上升,但变化较小;臭氧氧化可降解溶解性微生物代谢产物,降解效果受pH影响较小,类腐殖酸有机物随pH值增大而减少;DCAN、TCAN生成势随pH增大有所降低,TCNM生成势在pH=10条件下最高,1,1,1-TCP生成势在pH=7条件下最高.     

甲醇衍生法测定环境水体中八种酸性除草剂

文章建立了一种测定环境水体中8种酸性除草剂残留量的分析方法。1 000 mL样品在pH<2的情况下由乙醚分三次萃取后,萃取液经脱水,K-D浓缩至约1 mL,转移到衍生瓶中。在衍生瓶中补加2 mL正己烷、1 mL甲醇、8滴浓硫酸,80℃水浴加热1 h,进行甲醇衍生化处理,衍生后的样品运用气相色谱-质谱联用-分段选择离子扫描技术测定,内标法定量。结果表明:8种除草剂在0.05～2.5μg/L范围内线性均良好;方法灵敏度高,检出限均低于或等于0.02μg/L;方法的准确度和精密度高,在0.10、0.50、1.00、1.50μg/L添加水平下所有除草剂的回收率均在82.07%～116.99%之间,相对标准偏差RSD≤7.68%;经实际样品检测,可用于测定环境水体中酸性类除草剂的残留量。