趋磁细菌磁小体形成机制研究进展

磁小体(Magnetosome)是由趋磁细菌(Magnetotactic bacteria,MTB)体内合成并有生物膜包裹的纳米级磁性晶体,其形成过程是一个包括多种基因和蛋白参与并且受基因表达调控的酶催化过程.本文主要从铁离子吸收、磁小体膜形成、铁离子转运、生物矿化和磁小体链组装等5个方面来详细阐述磁小体的形成过程,重点介绍近年来分离和鉴定的相关基因和蛋白,并分析其在磁小体形成过程中的作用机制,同时还介绍了氧气、铁源和培养基成分等环境因素对磁小体形成的影响.尽管已经鉴别了大部分磁小体形成的相关基因,但是运用遗传学和生化分析手段阐明其作用机理仍然是一个挑战.磁小体形成机制的进一步研究和阐明将为其在生物技术领域的应用奠定基础.     

运用EASEWASTE对污泥填埋系统的生命周期分析

运用EASEWASTE对污泥与矿化垃圾混合填埋并用泥土作为覆盖材料的系统进行了生命周期分析.结果表明,污泥填埋的环境影响主要表现为存储的生态毒性(水)、温室效应和持久性生态毒性(土壤).其最大的污染因子分别为Cu、CH4和As.相比于前处理单元和运输单元,污泥填埋单元的环境影响最大,应尽可能加以控制.敏感性分析表明,降低渗滤液的产生量、提高填埋气的收集率以及把收集到的填埋气进行产热发电等综合利用都能有效的降低系统对环境的污染.应加强对填埋阶段的污染控制,改进填埋场的填埋气收集处理技术,规范日覆盖等填埋操作过程,加强渗滤液的收集和处理,最大程度的减小环境污染.     

Evaluate HAA removal in biologically active carbon filters using the ICR database

The effects of biologically active carbon (BAC) filtration on haloacetic acid (HAA) levels in plant effluents and distribution systems were investigated using the United States Environmental Protection Agency’s Information Collection Rule (ICR) database. The results showed that average HAA5 concentrations in all locations were 20.4 μg·L^-1 and 29.6 μg·L^-1 in ICR plants with granular activated carbon (GAC) and ICR plants without GAC process, respectively. For plants without GAC, the highest HAA levels were observed in the quarters of April to June and July to September. However, for plants with GAC, the highest HAA levels were observed in the quarters of April to June and January to March. This HAA level profile inversely correlated well with water temperature, or biologic activity. For GAC plants, simulated distribution samples matched well with distribution system equivalent samples for Cl₃AA and THMs. For plants with and without GAC, simulated distribution samples overestimated readily biodegradable HAAs in distribution systems. The study indicated that through HAA biodegradation, GAC process plays an important role in lowering HAA levels in finished drinking water.     

臭氧氧化深度处理二级处理出水的研究

以某城市污水处理厂二级处理出水为原水,研究了臭氧氧化深度处理对水中残留有机物以及病原微生物的降解和去除效果.结果表明,臭氧投加量达到6mg/L时,DOC、UV254、色度的去除率分别为15.49%、36.36%、73.61%,环境激素类痕量有机物邻苯二甲酸二丁酯(DBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)的去除率分别为37.29%和14.6%,三维荧光光谱荧光峰的各区域有机物质平均去除率在80%以上,DBP出水浓度为2.64mg/L,DEHP出水浓度为1.4mg/L,满足《城市污水再生利用地下水回灌水质》(GB/T 19772-2005)的标准.臭氧投加量达到10mg/L时,出水中指示性微生物粪大肠菌群仍接近103CFU/L,5mg/L有效氯消毒后出水粪大肠菌群仍接近10CFU/L,6mg/L臭氧与5mg/L有效氯组合消毒出水的粪大肠菌群下降至3CFU/L,满足《城市污水再生利用景观环境用水水质》(GB/T 18921-2002)的标准.三卤甲烷(THMs)的生成量随着有效氯投加量的增加而增加,臭氧与氯组合消毒过程与氯单独消毒过程相比,THMs生成量减少了78.08%.     

Trends of chemical speciation profiles of anthropogenic volatile organic compounds emissions in China, 2005–2020

This study estimates the detailed chemical profiles of China＇s anthropogenic volatile organic com- pounds （VOCs） emissions for the period of 2005-2020. The chemical profiles of VOCs for seven activity sectors are calculated, based on which the Photochemical Ozone Creation Potential （POCP） of VOCs for these sectors is evaluated. At the national level, the VOCs species emitted in 2005 include alkanes, alkenes and alkynes, aromatic compounds, alcohols, ketones, aldehydes, esters, ethers and halocarbons, accounting for 26.4wt.%, 29.2wt.%, 21.3 wt.%, 4.7 wt.%, 5.4 wt.%, 1.7 wt.%, 2.1 wt.%, 0.7 wt. % and 2.2wt.% of total emissions, respectively. And during 2005-2020, their mass proportions would respec- tively grow or decrease by - 34.7%, -48.6%, 108.5%, 6.9%, -32.7%, 7.3%, 65.3%, 100.5%, and 55.4%. This change would bring about a 13% reduction of POCP for national VOCs emissions in the future. Thus, although the national VOCs emissions are expected to increase by 33% over the whole period, its ozone formation potential is estimated to rise only by 14%. Large discrepancies are found in VOCs speciation emissions among provinces. Compared to western provinces, the eastern provinces with a more developed economy would emit unsaturated hydrocarbons and benzene with lower mix ratios, and aromatic compounds except benzene, oxidized hydrocar- bons and halocarbons with higher mix ratios. Such differences lead to lower POCP of VOCs emitted in eastern provinces, and higher POCP of VOCs emitted in western provinces. However, due to the large VOCs emissions from Chinese eastern region, the ozone forma- tion potential of VOCs emission in eastern provinces would be much higher than those in western provinces by about 156%-235%.     

海藻酸钠对改性黏土絮凝特征的影响

以海藻酸钠为藻源有机质的模式化合物,考察了赤潮水体中藻源有机化合物对改性黏土絮凝速率及絮凝体特征的影响;并利用图像分析法,测定了絮凝体的分形维数Df,借助分形维数对改性黏土的絮凝形态学特征进行了半定量化分析.结果表明:当海藻酸钠浓度在10~100mg/L范围内时,可以提高改性黏土絮凝的速率,絮凝体的分形维数Df、絮凝体强度呈现出先增大后减小的规律;其中,最佳浓度为50mg/L,其最大絮凝速率达到44.13、Df 为1.6823.低浓度(100mg/L)海藻酸钠能促进改性黏土的絮凝效率,但促进作用呈现减小的趋势,表现为最大絮凝效率减小,Df降低、絮凝体的空隙率增大.     

Metal binding capacity of soft acid,organic‐rich waters

Organic carbon from one stream and two ponds in South Carolina was fractionated into five nominal molecular diameter fractions by ultrafiltration. The concentrations associated with and binding capacity for Ca, Cd, Cu and Pb were determined for each fraction. The distribution of organic carbon among ultrafilter fractions varied from water to water, with the largest percentage occurring in the smaller fractions. Calcium was associated with each of the fractions isolated from each of the three waters, indicating Ca is bound to organics in all fractions, however, more than 99% of the Ca which passed the smallest ultrafilter was removed by cationic exchange resin. Each fraction bound more Ca than Cd, Cu or Pb except in a few cases where Pb binding was greater. All of the organic fractions had their Ca++ binding sites saturated. Calcium was not an effective competitive ion against Cd, Cu or Pb for organic binding sites. The total Cu binding capacity was less than that of Ca or Pb but similar to that of Cd. Naturally occurring organics bound more Pb than Cd or Cu but less than Ca. Saturation of Cu binding sites was less than 20% in most ultrafilter fractions except that with a nominal molecular weight of between 10,000 and 300,000 where the percent of saturation was as much as 60%. Approximately 50% of the Cu was removed onto anionic exchange resin in two waters while more than 90% was removed from water with a high organic content. Percent saturation of Cd and Pb binding sites ranged from 0.091% to 5.4% and 0.059% to 1.5%, respectively. All ions tested effectively competed with Cd, Cu or Pb for some but not all binding sites, indicating that organic binding sites were heterogeneous. A generalized order of metal‐organic stabilities based on competition for binding sites is Al>Cd>Pb>Cu>Ni = Mg=Zn = Mn>Ca. Both Cd+2 and Al+3 effectively out competed Pb++ and Cd and Pb out competed Cu for most organic binding sites.     

轻型汽油车VOCs排放特征及其大气反应活性

采用车载式尾气测量系统对国Ⅱ、国Ⅲ、国Ⅳ轻型汽油车在实际道路排放的尾气进行样品采集,并采用GC-MS、GC-FID对尾气中烷烃、烯烃、苯系物进行测试分析.结果表明轻型汽油车的VOCs排放因子随排放标准的提高显著降低,国Ⅱ、国Ⅲ、国Ⅳ3种车型的排放因子分别为49.62、21.65、6.72mg/km.苯系物占测定VOCs组分的比例最高,占到总VOCs的47.43%~60.52%.由排放的VOCs估算获得不同标准车型的臭氧生成潜势及二次有机气溶胶生成潜势分别为24.64~234.14mg/km和13.24~125.32mg/km.在对国Ⅲ车型进行的不同速度的实验结果显示,轻型汽油车尾气VOCs排放因子及相应的臭氧生成潜势和二次有机气溶胶生成潜势均随实验车速的升高而降低.     

Screening the emission sources of volatile organic compounds (VOCs) in China by multi-effects evaluation

We develop a multi-effect evaluation method to assess integrated impact of VOCs. Enable policy-makers to identify important emission sources, regions, and key species. Solvent usage and industrial process are the most important anthropogenic sources. Styrene, toluene, ethylene, benzene, and m/p-xylene are key species to be cut. Volatile organic compounds (VOCs) play important roles in the atmosphere via three main pathways: photochemical ozone formation, secondary organic aerosol production, and direct toxicity to humans. Few studies have integrated these effects to prioritize control measures for VOCs sources. In this study, we developed a multi-effects evaluation methodology based on updated emission inventories and source profiles, by combining the ozone formation potential (OFP), secondary organic aerosol potential (SOAP), and VOC toxicity data. We derived species-specific emission inventories for 152 sources. The OFPs, SOAPs, and toxicity of each source were estimated, the contribution and sharing of source to each of these adverse effects were calculated. Weightings were given to the three adverse effects by expert scoring, and then the integrated effect was determined. Taking 2012 as the base year, solvent use and industrial process were found to be the most important anthropogenic sources, accounting for 24.2% and 23.1% of the integrated effect, respectively, followed by biomass burning, transportation, and fossil fuel combustion, each had a similar contribution ranging from 16.7% to 18.6%. The top five industrial sources, including plastic products, rubber products, chemical fiber products, the chemical industry, and oil refining, accounted for nearly 70.0% of industrial emissions. Beijing, Chongqing, Shanghai, Jiangsu, and Guangdong were the five provinces contributing the largest integrated effects. For the VOC species from emissions showed the largest contributions were styrene, toluene, ethylene, benzene, and m/p-xylene.     

融雪期城市河流中溶解性有机物的时空分布特征

以沈阳市新开河为研究对象,考察了河水中溶解性有机物(DOM)含量的月份变化,以及融雪期河水中DOM含量和特性的时空变化规律.利用XAD树脂将DOM分为5个部分:疏水性有机酸(HPO-A),疏水性中性有机物(HPO-N),过渡亲水性有机酸(TPI-A),过渡亲水性中性有机物(TPI-N)和亲水性有机物(HPI).结果表明,融雪期河水中的溶解性有机碳(DOC)浓度较高,HPO-N和TPI-N是融雪期河水中的主要DOM组分,并且DOM中的荧光物质主要为类芳香族蛋白质荧光物质和类腐植酸荧光物质.融雪期水体中的DOC、波长254nm处的紫外吸光度(UV-254)和三卤甲烷生成势(THMFP)呈先降低然后波动最后升高的变化趋势.特征紫外吸光度(SUVA)和三卤甲烷生成活性(STHMFP)与以上三者的变化规律相反.融雪期河水中的DOC受污水排放影响大,有排污口处的DOC含量明显大于其他区域.污水排放也使受纳水体中UV-254对THMFP的指示作用减弱.