Molecular and physiological characterization of fluoroquinolone resistance in relation to uropathogenicity among Escherichia coli isolates isolated from Wenyu River, China

Increasing antibacterial resistance and pathogenicity in the environment is of growing concern due to its potential human risk. In the present study, 236 Escherichia coli isolates were collected from Wenyu River in China on drugless (48 isolates) and quinolone-containing plates (189 isolates). Their minimum inhibitory concentrations (MICs) were determined ranging from 0.125 μg mL⁻¹ to 128 μg mL⁻¹. Mutation points related to fluoroquinolone resistance were observed at S83 to L and D87 to N or Y in the GyrA subunit and S80 to R or I and E84 to G in the ParC subunit. Generally, MICs of LEV and GAT are dependent on the patterns of these mutation points. The profile with three mutation points was related to LEV-resistant E. coli isolates, and the (S83L, D87N + S80I) mutation profile was most prevalent (65.7%) in LEV-resistant isolates, while a large proportion of isolates, even those with three mutation points, were susceptive to GAT. The incidence of virulence factors in LEV-resistant isolates (44.7%, 59/132) was much higher than in nonresistant isolates (23.1%, 24/104) (χ² = 11.925, 1° of freedom, p < 0.001) indicating that fluoroquinolone-resistant E. coli would pose a potential risk. A similar distribution was also found in isolates resistant to GAT (χ² = 7.843, 1° of freedom, p = 0.0079).     

Desorption of polycyclic aromatic hydrocarbons from field-contaminated soil to a two-dimensional hydrophobic surface before and after bioremediation

This study investigated environmental distributions and production mechanisms of chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) in the sediments from some tidal flats located in Asia. Cl-PAHs were found in sediments taken from Arao tidal flat, Kikuchigawa River and Shirakawa River. The range of ∑Cl-PAHs was from 25.5 to 483 pg g⁻¹ for Kikuchigawa River and Arao tidal flat, respectively.Concentrations of PAHs and Cl-PAHs showed no significant correlations (r = 0.134). This result suggests that the origins of these compounds differ. In the identified Cl-PAH isomers, the most abundant Cl-PAH isomer was 9,10-dichloroanthracene (9,10-di-Cl-ANT) in the three sites. In general, concentrations of Cl-ANTs in the coastal environment are about 3-5 orders of magnitude lower than those of anthracene (ANT). However, concentration ratios between Cl-ANTs and ANT (Cl-ANTs/ANT) in the sediments ranged from 4.1% to 24.6%. This result indicated that Cl-PAHs were not generated under industrial processes but the high concentration ratios have resulted from the contribution of photochemical production of Cl-ANTs in the sediments because ANT is known to have high photochemical reactivity.For examining this phenomenon, ANT adsorbed onto glass beads was irradiated with UV under the mimicked field conditions of tidal flats. As a result, it was noticed that, while chlorinated derivatives were negligible in a light-controlled group, production of 2-Cl-ANT, 9-Cl-ANT and 9,10-diCl-ANT on the irradiated surface were found in this study. These results suggest that photochemical reaction of PAHs can be a potential source of the occurrence of Cl-PAHs in the coastal environment.     

西安市城市主干道路面径流初期冲刷效应

以西安市城市主干道南二环太白路高架桥为路面径流采样区域,采用人工等时间间隔采样方法,在桥梁排水立管对2010年9—11月的3场径流事件进行全程采样,测试径流过程SS、COD、溶解性COD、NH3-N、Pb、溶解性Pb、Zn和溶解性Zn的浓度变化,研究路面径流的初期冲刷效应及其影响因素。结果表明,西安市城市主干道路面径流污染严重,降雨数小时后的末期径流仍具有较高的污染水平;径流过程污染物浓度变化规律与其赋存形态有关,SS、COD、Pb等以颗粒态为主的污染物的浓度随雨强变化剧烈波动,NH3-N、溶解态COD、溶解态Zn等以溶解态为主的污染物浓度变化受雨强影响较小,随径流过程呈逐渐减小趋势;路面径流初期冲刷现象并非普遍存在,与污染物的赋存状态和场次降雨特征密切相关,溶解态污染物易于出现初期冲刷现象,颗粒态污染物是否出现初期冲刷与场次降雨特征有关;测试的3场径流事件初期30%的径流携带的SS、COD、溶解性COD、NH3-N、Pb、Zn和溶解性Zn的负荷占场次径流总负荷的比例分别为21.8%～50.0%、25.5%～49.3%、36.3%～52.6%、52.6%～66.7%、26.8%～45.0%、27.2%～63.4%和36.2%～62.6%,表明仅对初期径流进行治理无法实现对西安市路面径流污染的有效控制。     

环丁砜-哌嗪溶液吸收烟道气中二氧化碳

采用搅拌实验装置,研究环丁砜溶液及不同配比的环丁砜-PZ复合溶液对烟道气中二氧化碳的吸收和解吸性能,揭示了吸收容量与酸碱度、时间之间的内在联系,并对CO2初始逸出温度、试液再生温度、试液再生率、再生pH下降率进行了细致记录分析。实验结果表明,环丁砜-PZ复合溶液配比为0.4∶0.6时:吸收效果最佳,吸收量约为0.126 mol;再生温度最高,为105℃;再生率最高,为90.34%。同时与相同配比的MEA、DEA相比具有较大再生优势。实验结果还表明,环丁砜-PZ复合体系之间存在负交互作用。     

Bio-immobilization of Cu and Zn in recirculated bioreactor landfill

Purpose  

To protect the environmental quality of soil, groundwater, and surface water near the landfill site, it is necessary to make an accurate assessment of the heavy metal mobility. This study aims to present the bio-immobilization behavior of heavy metals in landfill and provide some reference suggestion for the manipulation of heavy metal pollution control after closure.     

Zr—Fe双组分复合除砷吸附剂的优化制备及性能评价

实验发现,铁氧化物或铁的羟基氧化物对As（V）有较好的吸附性能,而锆氧化物或锆水合氧化物则对As（Ⅲ）有优异的吸附选择性,但其使用的pH通常要在〉9的条件下。通过简单的共沉淀法制备了Zr-Fe双组分复合吸附剂,在制备过程中通过优化制备条件如：沉淀剂浓度、金属离子总浓度、金属离子配比、反应温度、反应时间及吸附剂价格等因素,最终合成出了对As（V）和As（Ⅲ）都具有良好吸附能力的吸附剂。这种吸附剂在中性条件下对As（V）和As（Ⅲ）的最大吸附量为62mg／g和118mg／g。     

Effect of silicate supplementation on the alleviation of arsenite toxicity in 93-11 (Oryza sativa L. indica)

Chronic exposure to arsenic (As) in rice has raised many health and environmental problems. As reported, great variation exists among different rice genotypes in As uptake, translocation, and accumulation. Under hydroponic culture, we find that the Chinese wild rice (Oryza rufipogon; acc. 104624) takes up the most arsenic among tested genotypes. Of the cultivated rice, the indica cv. 93-11 has the lowest arsenic translocation factor value but accumulates the maximum concentration of arsenic followed by Nipponbare, Minghui 86, and Zhonghua 11. Higher level of arsenite concentration (50 μM) can induce extensive photosynthesis and root growth inhibition, and cause severe oxidative stress. Interestingly, external silicate (Si) supplementation has significantly increased the net photosynthetic rate, and promoted root elongation, as well as strongly ameliorated the oxidative stress by increasing the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase, and peroxidase in roots and/or leaves of 93-11 seedlings. Notably, 1.873 mM concentration of Si considerably decreases the total As uptake and As content in roots, but significantly increases the As translocation from roots to shoots. In contrast, Si supplementation with 1.0 mM concentration significantly increases the total As uptake and As concentrations in roots and shoots of 93-11 seedlings after 50 μM arsenite treatment for 6 days.     

生物填料地下渗滤系统对生活污水的脱氮

将草甸棕壤、炉渣和活性污泥等基质按体积比13∶6∶1配制生物填料,研究了生物填料地下渗滤系统（subsurface wastewater infiltration system,SWIS）在不同的水力负荷和污染负荷条件下对校园生活污水的脱氮效果。场地实验结果表明,当BOD5负荷为12.0 g BOD5/（m2·d）,表面水力负荷为0.04-0.10 m3/（m2·d）时,SWIS对NH＋4-N和TN的平均去除率分别为92.4%和82.0%。当水力负荷为0.08 m3/（m2·d）,BOD5负荷9.3-16.8 g BOD5/（m2·d）时,SWIS对NH＋4-N和TN的平均去除率为92.7%和81.2%。SWIS中氧化还原电位（oxygen reduction potential,ORP）随进水水力负荷和BOD5负荷的增加而降低,脱氮效率下降。综合出水水质和处理效率,适宜的水力负荷和污染负荷分别为0.065 m3/（m2·d）和12.0 g BOD5/（m2·d）。在此条件下,SWIS的启动周期为25-30 d。出水水质均优于《城市污水再生利用-景观环境用水水质》（GB/T18921-2002）标准,且处理效果稳定,抗负荷冲击能力强。     

高碱度水库水混凝过程中残留铝控制

针对高碱度水库水源的某水厂残留铝超标问题,选取碱化度(B)与Alb含量不同的3种铝盐絮凝剂,研究不同投量与pH值下混凝效果与残留铝浓度水平。结果表明,碱化度和Alb含量显著影响混凝效果。DOC和浊度的去除率随着3种絮凝剂AlCl3(B=0)、PACl-1(B=1.2)、PACl-2(B=2.2)投量增大而升高。3种絮凝剂投量在1.5～2.0 mg/L(以铝计)范围内,总铝和溶解铝含量最低。对于该水厂自制的絮凝剂PACl-2,可通过降低絮凝剂碱化度,或将水的pH值降低至7～7.5之间,以此可以提高PACl-2混凝效果,而且可以降低出厂水残留铝浓度。考虑工程应用可行性,可优先考虑调整絮凝剂生产工艺。     

碳源及反硝化芽孢杆菌强化低C/N比景观水体的生物脱氮

实验探讨了添加碳源及投加反硝化细菌对低碳氮比景观水体生物脱氮的影响。结果表明,有机碳源及B.subtilis FS05均能显著促进实验水体的生物脱氮作用,实验水体在28℃静置72 h后,乙醇添加组的TN、氨氮、硝酸盐及亚硝酸盐的去除率分别达到了62.7%、67.0%、69.8%和29.4%,而同样条件下,B.subtilis FS05投加组的去除率分别达到了66.9%、73.4%、66.0%和82.2%。从水质变化趋势可以看出,投加B.subtilis FS05能在更短时间内完成生物脱氮过程,其中,硝酸盐和亚硝酸盐去除速率最快,分别仅需要18 h和12 h。