抗生素与LED209对大肠杆菌的联合毒性机制

抗生素是一把双刃剑,在提高医疗水平的同时会促进抗性基因的发展。群体感应抑制剂(quorum sensing inhibitors,QSIs)可有效地避免这一缺陷,有望成为抗生素的替代品而与抗生素有环境共存的可能,但目前尚缺乏它们的联合毒性机制及其相关的环境风险评价研究。本文以大肠杆菌为受试生物,测定了群体感应抑制剂N-苯基-4-(3-苯基硫代脲基)苯磺酰胺(LED209)与5种抗生素的单一和二元联合毒性。结果表明,LED209与5种抗生素的联合毒性作用均表现为拮抗,推测是LED209通过影响鞭毛合成,减弱了抗生素对大肠杆菌的生物有效性;同时通过拆分分子式,发现了拮抗作用可能源于LED209分子式中的含苯基和硫代脲基的L1分子,因此建议未来在LED209药物优化时,应尽可能的保留L1部分的基团,从而保证混合体系的最小环境风险。本研究不仅为联合用药提供依据,而且从环境风险评价角度为抗生素替代品LED209的结构优化提供理论指导。     

基于IFS-动态加权的地下综合体深基坑施工风险评价

为控制地下综合体深基坑施工风险,提出了一种基于直觉模糊集(IFS)-动态加权的风险评价方法.从地质条件、建筑环境、岩土设计、施工方案和偶然风险5个方面分析地下综合体深基坑施工风险因素,构建了综合风险评价指标体系.采取施工风险5级划分方法,利用IFS理论确定指标风险;以偏大型正态加权函数确定指标权重,得到系统综合风险.以西安市某地下综合体深基坑施工实际为背景,进行方法应用.结果表明,该西安市地下综合体深基坑施工系统风险等级为显著风险.其中,指标"邻近建筑""地下管网"的风险等级为高度风险,"道路交通""基坑边坡稳定性""降排水实施"为显著风险,对此提出了相应的安全措施.     

特朗普“去气候化”政策对全球气候治理的影响

美国特朗普政府宣布退出《巴黎协定》是当前全球气候治理中最受舆论关注的问题,对事态发展趋势的判断和事件影响的评估是最为亟需的。本文系统分析了特朗普政府上任后推行的一系列"去气候化"政策,以及其退出《巴黎协定》的主要动因和可能形式,同时量化评估了这些内政外交的"倒退"对美国实施国家自主贡献目标以及全球气候治理格局的实质影响,并据此提出了中国应对全球气候治理新形势变化的对策和建议。研究表明,特朗普政府"美国优先"的能源政策根植于复兴制造业和加大基础设施投资的经济利益动机,随着特朗普"去气候化"进程持续发酵,诸多气候政策面临存续风险,美国实施国家自主贡献将面临严峻挑战,"倒行政策"将有可能使美国温室气体排放出现反弹。如果不考虑中、高危气候政策,美国2025年温室气体排放也仅能相对2005年下降11.0%—14.9%,距离下降26%—28%的国家自主贡献目标相去甚远。同时,特朗普政府拒绝继续履行向发展中国家提供气候资金支持的义务,将有可能导致绿色气候基金拖欠资金总额上升117%,并进一步挫伤全球低碳投资的信心。没有美国的全球气候治理3.0时代将呈现出新的复杂特征,并不可避免地造成减排、资金和领导力缺口的持续扩大,也不排除后续会出现消极的跟随者,整体进程将可能进入一个低潮周期。虽然国际社会对中国引领全球气候治理充满期待,但中国仍应审慎对待,长远谋划应对气候变化的内政外交战略,而不应将"气候举旗"看作是一蹴而就的短期策略,对各种要求中国发挥"领导作用"的说法保持清醒头脑。在今后气候谈判中,美国仍有较大可能会二次"要价",中国作为排放大国的压力依然不容小觑,中美气候关系需要再定位。     

振荡辐射下PMMA 热解与着火过程研究

采用正弦波变化振荡的辐射热流,对热厚PMMA(聚甲基丙烯酸甲酯)的热解和着火过程进行研究,同时采用数值模拟,对实验结果进行验证和补充。结果表明,表面温度和深度温度随着时间而增加,温度由于周期性的辐射而发生振荡,而振荡幅度随着深度的增加而衰减;表面温度与深度温度振荡存在时间延迟;着火时间随着热流振荡周期的增大而减小,主要由于平均热流密度随着周期增大而增大。     

Occurrence,sources, and ecological risks of PBDEs,PCBs, OCPs,and PAHs in surface sediments of the Yangtze River Delta city cluster,China

Polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) in 25 surface sediments in three cities (Nantong, Wuxi, and Suzhou) in the Yangtze River Delta, eastern China were measured. The mean concentrations were 378, 45.8, 1.98, 4,002 ng/g for PBDEs, OCPs, PCBs, and PAHs, respectively. Their levels in the sediments in the three cities were generally consistent with the city industrialization. PBDEs and OCPs were markedly dominated by deca-BDE (>90 %) and DDTs (>70 %). A principle component analysis of the analytes identified three major factors suggesting different sources of the contaminants in the sediments. PBDEs and the organic carbon in the sediments have common sources from industrial activities; whereas OCPs and PCBs, correlated with the second factor, were mainly from historical sources. The third factor with loadings of PAHs is indicative of various combustion sources. Ecological risk assessment indicated that the potential highest risk is from DDTs, for which 22 sites exceed the effects range low (ERL) values and three sites exceed the effects range median (ERM) value.     

Toxicity of urban highway runoff in Shanghai to Zebrafish (Danio rerio) embryos and luminous bacteria (Vibrio qinghaiensis.Q67)

Pollution from urban highway runoff has been identified as one of the major causes of the deterioration of receiving water quality. The purpose of this study is to assess the toxicity of urban storm water samples in Shanghai using the zebrafish (Danio rerio) embryo test and the bacterial luminescence (Vibrio qinghaiensis) assay. The toxicity of highway runoff from seventeen storm events was investigated in both grab and composite samples. Zebrafish embryos were exposed to the runoff samples and development parameters including lethality, spontaneous movements in 20 s, heart beat rate, hatching rate, and abnormality of zebrafish embryos were observed after 24, 48, 72, and 96 h of exposure. Inhibition rates of luminescence intensity were also recorded. The results showed that in the zebrafish embryo toxicity tests, both grab and composite samples increased the lethality, reduced the percentage with spontaneous movements and heart beats, inhibited the hatching of embryos, and induced morphological abnormalities. In the Vibrio qinghaiensis toxicity test, all the grab samples inhibited the luminescence, while some of the composite samples promoted it, which indicated that different types of toxicants might have been affecting the species. The multivariate statistics analysis indicated that heavy metal (zinc, manganese, and copper) and PAHs might mainly contribute to the toxicity of runoff samples.     

Study on the denitrification performance of FexLayOz/activated coke for NH3-SCR and the effect of CO escaped from activated coke at mid-high temperature on catalytic activity

Currently, activated coke is widely used in the removal of multiple pollutants from industrial flue gas. In this paper, a series of novel Fe_xLa_yO_z/AC catalysts was prepared by the incipient wetness impregnation for NH₃-SCR denitrification reaction. The introduction of Fe-La bimetal oxides significantly improved the denitrification performance of activated coke at mid-high temperature, and 4% Fe_0.3La_0.7O_1.5/AC exhibited a superior NO_x conversion efficiency of 90.1% at 400 °C. The catalysts were further characterized by BET, SEM, XRD, Raman, EPR, XPS, FTIR, NH₃-TPD, H₂-TPR, et al., whose results showed that the perovskite-type oxide of LaFeO₃ and oxygen vacancies were produced on the catalysts’ surfaces during roasting. Fe-La doping enhanced the amount of acid sites (mainly Lewis and other stronger acid sites) and the content of multifarious oxygen species, which were beneficial for NO_x removal at mid-high temperature. Moreover, it was investigated that the effect of released CO from activated coke at mid-high temperature on the NO_x removal through the lifetime test, in which it was found that a large amount of CO produced by pyrolysis of activated coke could promote the NO_x removal, and long-term escaping of CO on the activated coke carrier did not have a significant negative impact on catalytic performance. The results of the TG-IR test showed that volatile matter is released from the activated coke while TG results showed that the weight loss rate of 4% Fe_0.3La_0.7O_1.5/AC only was 0.0015~0.007%/min at 300–400 °C. Hence, 4% Fe_0.3La_0.7O_1.5/AC had excellent thermal stability and denitrification performance to be continuously used at mid-high temperature. Finally, the mechanisms were proposed on the basis of experiments and characterization results.

     

Sulfur cycle as an electron mediator between carbon and nitrate in a constructed wetland microcosm

• Fe(III) accepted the most electrons from organics, followed by NO₃^‒, SO₄^2‒, and O₂. • The electrons accepted by SO₄^2‒ could be stored in the solid AVS, FeS₂-S, and S⁰. • The autotrophic denitrification driven by solid S had two-phase characteristics. • A conceptual model involving electron acceptance, storage, and donation was built. • S cycle transferred electrons between organics and NO₃^‒ with an efficiency of 15%. A constructed wetland microcosm was employed to investigate the sulfur cycle-mediated electron transfer between carbon and nitrate. Sulfate accepted electrons from organics at the average rate of 0.84 mol/(m³·d) through sulfate reduction, which accounted for 20.0% of the electron input rate. The remainder of the electrons derived from organics were accepted by dissolved oxygen (2.6%), nitrate (26.8%), and iron(III) (39.9%). The sulfide produced from sulfate reduction was transformed into acid-volatile sulfide, pyrite, and elemental sulfur, which were deposited in the substratum, storing electrons in the microcosm at the average rate of 0.52 mol/(m³·d). In the presence of nitrate, the acid-volatile and elemental sulfur were oxidized to sulfate, donating electrons at the average rate of 0.14 mol/(m³·d) and driving autotrophic denitrification at the average rate of 0.30 g N/(m³·d). The overall electron transfer efficiency of the sulfur cycle for autotrophic denitrification was 15.3%. A mass balance assessment indicated that approximately 50% of the input sulfur was discharged from the microcosm, and the remainder was removed through deposition (49%) and plant uptake (1%). Dominant sulfate-reducing (i.e., Desulfovirga, Desulforhopalus, Desulfatitalea, and Desulfatirhabdium) and sulfur-oxidizing bacteria (i.e., Thiohalobacter, Thiobacillus, Sulfuritalea, and Sulfurisoma), which jointly fulfilled a sustainable sulfur cycle, were identified. These results improved understanding of electron transfers among carbon, nitrogen, and sulfur cycles in constructed wetlands, and are of engineering significance.     

生物基质对煤渣改良地下渗滤系统脱氮效果的影响

地下渗滤系统(SWIS)对硝化、反硝化过程调控不灵活,导致其对氮的去除效果不够理想。组建了两套SWIS装置(1#装置:65～80cm段没有生物基质;2~#装置:65～80cm段添加生物基质),对沿程氮素、硝化和反硝化作用强度及氮还原酶活性进行分析。结果表明,两套装置均表现为硝化反应主要发生在20～60cm段,反硝化反应主要发生在60～80cm段。2~#装置的反硝化作用明显强于1#装置,因此其TN去除率高于1~#装置。硝化作用强度随深度增加而递减,反硝化作用强度随深度增加而递增。硝酸盐还原酶(NAR)活性随深度的增加而逐渐减弱,亚硝酸盐还原酶(NIR)活性随深度的增加先减弱后又增强。主要原因是2~#装置中添加了干化污泥作为生物基质,为反硝化作用补充了碳源,增强了脱氮能力。