The joint effects of sulfonamides and their potentiator on Photobacterium phosphoreum: differences between the acute and chronic mixture toxicity mechanisms

Organisms are typically exposed to mixtures of chemicals over long periods of time; thus, chronic mixture toxicity analysis is the best way to perform risk assessment in regards to organisms. However, most studies focus on the acute mixture toxicity. To investigate the difference between chronic mixture toxicity and acute mixture toxicity, Photobacterium phosphoreum were exposed to chronic (24 h exposure) and acute (15 min exposure) toxicity of single sulfonamide (SA) and their potentiator (trimethoprim, TMP), both individually and mixtures (SA with TMP). A comparison of chronic vs. acute mixture toxicity revealed the presence of an interesting phenomenon, that is, that the joint effects vary with the duration of exposure; the acute mixture toxicity was antagonistic, whereas the chronic mixture toxicity was synergistic. Based on the approach of Quantitative Structure Activity Relationships (QSARs) and molecular docking, this phenomenon was proved to be caused by the presence of two points of dissimilarity between the acute and chronic mixture toxicity mechanism: (1) the receptor protein of SAs in acute toxicity was Luc, while in chronic toxicity it was Dhps, and (2) there is a difference between actual concentration of binding-Luc in acute toxicity and individual binding-Dhps in chronic toxicity. This deep insight into the difference between chronic and acute mixture toxicity will benefit environmental science, medical science, and other disciplines. The existence of these differences poses a challenge for the assessment of routine combinations in medicine, risk assessment, and mixture pollutant control, in which, previously, only a synergistic effect has been observed between SA and their potentiator.     

四溴双酚A降解技术的研究进展

综述了微生物、物理和化学降解技术等几种主要的四溴双酚A（TBBPA）降解技术的研究进展。阐述了各种降解技术的机理和优缺点。指出今后重点的研究方向是：根据不同的反应机理和生长特性分离出微生物降解TBBPA的优势菌种,探索将TBBPA彻底碳化的工艺条件;优化高级氧化法降解TBBPA的反应条件,使之更适于工程应用;将还原法与微生物降解技术或高级氧化法相结合,先将TBBPA快速还原成双酚A,再进一步彻底碳化成CO2和H2O。     

硝化菌的分离及特性分析

从联合脱硫脱氮填料塔中的陶粒上分离出两株硝化菌,命名为NS2和NS5,这2种菌均为革兰氏阴性菌。硝化能力测试结果表明:NS2和NS5能利用亚硝酸盐作为氮源,将亚硝酸盐转化成硝酸盐,硝化速率都达到60%以上。部分长度的16S rDNA序列同源性分析表明,NS2和NS5与Delftia sp.的同源性高达99%,并用MEGA程序对该菌株进行了系统发育进化分析。结合形态观察和生理生化鉴定,初步鉴定NS2,NS5为戴尔福特菌(Delftia sp.)。     

钙基吸附剂捕集生物质燃气中的二氧化碳

生物质热解燃气中CO2的捕集,是提高燃气热值和实现碳减排的关键问题之一。为利用生物质热解燃气温度偏高的特点,拟通过化学吸附方法,捕集燃气中高浓度的CO2。为此,利用不同钙基前驱物制备了系列钙基固体吸附剂,系列钙基固体吸附剂对CO2的单次吸附和循环吸附实验结果表明,含钙和镁氧化物混合物的吸附剂具有较稳定的循环吸附特性以及较大的吸附负荷。孔结构特性分析表明,适宜于CO2吸附的有效孔径范围可能为小于4 nm。因此,可以通过对天然白云石的改性获得合适孔径的钙镁基固体吸附剂,达到有效捕集生物质燃气中CO2的目的。     

铁-锰-碳微电解法处理对苯二酚废水

在传统铁-碳微电解填料(简称铁-碳填料)中加入锰粉进行改性,制备了规整化铁-锰-碳改性微电解填料(简称铁-锰-碳填料),并采用该填料处理质量浓度为1 000 mg/L的模拟对苯二酚废水。实验结果表明:在铁-锰-碳填料投加量25.0 g/L、反应时间4.0 h、锰粉质量分数9%、初始废水pH为3的最佳工艺条件下,对苯二酚去除率达95.55%;与铁-碳填料相比,铁-锰-碳填料可大幅提高对苯二酚的去除率,且对废水pH的适应范围较宽;采用铁-锰-碳填料处理对苯二酚废水的过程中,废水pH大体呈现先上升后下降的趋势;由降解中间产物可推断对苯二酚首先被氧化为对苯醌,然后逐渐降解为有机酸。     

纳米FeVO_4的制备及其可见光下降解甲苯的性能

以Fe(NO3)3或FeCl3作为铁源,采用水热法制备了纳米FeVO4光催化剂,通过XRD、SEM、DRS等手段表征了所合成FeVO4的物相、表面形貌及光学性质,研究了其可见光下光催化降解甲苯的性能。表征结果显示:FeVO4平均晶粒尺寸约为75 nm,为棒状;FeVO4在可见光区域(λ400 nm)表现出较高的吸光性,其吸光区域可红移至约600 nm;以FeCl3为铁源,水热反应3 h制备的FeVO4的禁带宽度为2.1 e V;以Fe(NO3)3为铁源制备的FeVO4的比表面积(74.70 m2/g)大于以FeCl3为铁源制备的FeVO4的比表面积(67.72 m2/g)。在初始甲苯质量浓度为494 mg/L、FeVO4为光催化剂、反应4 h的条件下,甲苯降解率达62%。甲苯降解最终产物为CO2和H2O。     

活性炭吸附处理电镀废水中的EDTA

采用颗粒活性炭对模拟废水中EDTA进行批式吸附实验,在实验中考察了恒温振荡器的振荡速度、温度、pH值等因素对吸附的影响,同时探讨了吸附等温线模型和吸附动力学模型。实验结果表明,在25％时活性炭对EDTA的吸附平衡时间为40h。在pH值为5．0、温度为25℃、振荡器振荡速度为200r／min、活性炭粒径为1～2mm、活性炭加入量为10g／L的情况下,EDTA的浓度在48h内由368．8mg／L降低至76．34mg／L,对应的COD值从305．9mg／L降低为67．21mg／L,去除率达到了79．3％。活性炭对EDTA的吸附符合Langmuir吸附等温线模型,其吸附行为可以用准二级吸附动力学模型来描述。     

K-Ca-Mg-Cl-H_2O体系中硫酸钙结晶介稳区的研究

对K-Ca-Mg-Cl-H2O体系中硫酸钙结晶介稳区进行了研究。以一定浓度氯化钙溶液与硫酸镁溶液反应结晶的方式,采用激光散射法测定了不同浓度复合盐溶液和温度下硫酸钙过饱和度与结晶之间的关系,并测定了与之平衡的溶解度,从而确定该体系中硫酸钙结晶介稳区宽度,探讨了影响结晶介稳区的因素,以及硫酸钙结晶和结晶相与复合盐溶液浓度、温度、结晶介稳区之间的关系。     

改性污泥替代垃圾填埋场覆土的研究

以市政污泥为研究对象,采用固化剂对污泥进行改性,通过分析不同固化剂添加比例下固化产物的抗压强度和渗透系数,比较不同养护时间下污泥固化产物浸出液的COD、氨氮和重金属性质,探讨市政污泥固化产物作为垃圾填埋场覆土可行性。实验结果表明：固化剂添加比例为30％的固化产物抗压强度高于50kPa,其渗透系数达到10^-7cm／s数量级,基本满足覆土材料的标准要求。污泥固化产物重金属的最大浸出量远远低于《污水综合排放标准》（GB8978-88）中一级排放标准。随养护时间延长,固化产物浸出液COD和氨氮浸出浓度亦呈下降趋势,重金属Pb、Cd浸出量明显减少,浸出比例小于1％。养护有利于降低固化产物的浸出污染程度,30％的污泥固化产物养护3d后可作为垃圾填埋场日覆盖材料。     

Reducing volatilization of heavy metals in phosphate-pretreated municipal solid waste incineration fly ash by forming pyromorphite-like minerals

This research investigated the feasibility of reducing volatilization of heavy metals (lead, zinc and cadmium) in municipal solid waste incineration (MSWI) fly ash by forming pyromorphite-like minerals via phosphate pre-treatment. To evaluate the evaporation characteristics of three heavy metals from phosphate-pretreated MSWI fly ash, volatilization tests have been performed by means of a dedicated apparatus in the 100-1000 °C range. The toxicity characteristic leaching procedure (TCLP) test and BCR sequential extraction procedure were applied to assess phosphate stabilization process. The results showed that the volatilization behavior in phosphate-pretreated MSWI fly ash could be reduced effectively. Pyromorphite-like minerals formed in phosphate-pretreated MSWI fly ash were mainly responsible for the volatilization reduction of heavy metals in MSWI fly ash at higher temperature, due to their chemical fixation and thermal stabilization for heavy metals. The stabilization effects were encouraging for the potential reuse of MSWI fly ash.