Advances in the study of directed evolution for cellulases

If cellulose can be effectively hydrolyzed into glucose by cellulase, the production costs of hydrogen, ethanol or other chemicals from cellulosic materials will be greatly decreased, and economically viable production of biohydrogen and bioethanol will become feasible. Cellulose is degraded into glucoses by multi-component enzyme systems. Nowadays cellulases are widely used in brewing, food, bioenergy, fodder, textiles, paper, pharmaceuticals, environmental protection and other industries. However, existing cellulases have several problems that limit their wider applications, including the low turnover number for solid cellulosic materials, and low stability in adapting to various application conditions. For example, high temperature, low pH, and so on. Application of directed evolution technology may be one of the most effective ways for improving the characteristics of cellulases. This paper presents a brief review of the cellulose hydrolysis mechanism by cellulase, advances in cellulases (endoglucanase and β-glucosidase) improvement by directed evolution for several characteristics (for instance, thermal stability, pH adaptability and enzyme activity), limitations of directed evolution for cellulases, and the outlook for directed evolution for cellulase.     

2013年1月中国东部地区重污染过程中上海市细颗粒物的来源追踪模拟研究

大气PM_2.5是当前我国城市和区域面临的最突出的大气污染问题,然而PM_2.5及其关键组分污染的来源不清,严重制约了人们对PM_2.5 的科学认知和污染防控的步伐.本研究以2013年1月中国东部地区一次典型重污染过程为研究案例,利用CAMx三维模型中耦合了物种示踪机制的颗粒物来源追踪方法,探讨和揭示了中国东部地区代表性城市上海及周边地区共4个源区(上海、苏南、浙北、大区域)、8类污染源(包括燃烧源、生产工艺过程、流动源、生活面源、挥发源、扬尘源、农业源、天然源)对上海城区大气中PM_2.5及其关键组分包括水溶性无机离子(SO^2-₄、NO^-₃、NH⁺₄)、元素碳(EC)和有机碳(OC)的污染贡献.研究结果表明,2013年1月份中国东部出现严重灰霾污染期间,上海城区PM_2.5的主要区域贡献为上海本地污染源排放累积(PM_2.5浓度贡献平均为55.4%±22.3%)和长距离输送(38.4%±20.0%).上海地区8类主要排放源中,扬尘源贡献均值最大,达到30.7%±31.8%,其次为燃烧源18.2%±15.6%、流动源18.6%±17.5%、挥发类源16.9%±18.0%.对上海市PM_2.5组分的源解析研究发现,燃烧源对细颗粒物中硫酸盐和硝酸盐的浓度贡献最大,其浓度贡献分别达到56.2%和55.9%.铵盐中72.4%来源于挥发类源贡献,元素碳约78.3%来自于交通源贡献.挥发类源排放和流动源是主要的有机气溶胶贡献源,浓度贡献分别为36.2%和32.5%.     

钻井液生物毒性评价方法对比

对目前国内外钻井液生物毒性评价的主要方法──糠虾法、黑褐新糠虾法、发光细菌法、发光海藻法等进行了对比,分析了各种评价方法的优缺点。研究结果表明,发光细菌法快速、简便,符合我国钻井现场应用实际情况,因而推荐使用发光细菌法作为钻井液生物毒性评价方法。     

Advances in the study of directed evolution for cellulases

If cellulose can be effectively hydrolyzed into glucose by cellulase, the production costs of hydrogen, ethanol or other chemicals from cellulosic materials will be greatly decreased, and economically viable production of biohydrogen and bioethanol will become feasible. Cellulose is degraded into glucoses by multi-component enzyme systems. Nowadays cellulases are widely used in brewing, food, bioenergy, fodder, textiles, paper, pharmaceuticals, environmental protection and other industries. However, existing cellulases have several problems that limit their wider applications, including the low turnover number for solid cellulosic materials, and low stability in adapting to various application conditions. For example, high temperature, low pH, and so on. Application of directed evolution technology may be one of the most effective ways for improving the characteristics of cellulases. This paper presents a brief review of the cellulases hydrolysis mechanism by cellulase, advances in cellulases (endoglucanase and β-glucosidase) improvement by directed evolution for several characteristics (for instance, thermal stability, pH adaptability and enzyme activity), limitations of directed evolution for cellulases, and the outlook for directed evolution for cellulase.     

中原城市群臭氧浓度分布特征及来源

利用2015年臭氧(O_3)自动监测数据和源排放清单,分析了中原城市群O_3浓度的空间、时间分布情况,探讨了中原城市群中城市间O_3的相关性,以及O_3浓度、NOx、VOCs、CO及汽车保有量间的相关性。指出中原城市群是全国更是河南O_3污染的严重地区,O_3浓度年内月度变化呈倒"V"型分布,具有明显的北部城市特征;中原城市群9个城市间除开封外其他8个城市间都呈高度正相关性,相关系数均为0.892~0.991;9个城市机动车保有量及NOx、VOCs和CO等前体物的年排放量与其年均O_3浓度之间存在正相关性。分析认为,NOx、VOCs和CO等前体物的排放是中原城市群O_3浓度偏高的主要影响因素,同时O_3浓度也与日照时间、降雨量、植物源VOCs排放量及相邻城市间污染物的空间输送等因素有着密切的关系。     

挥发性有机化合物气体泄漏检测与修复技术

介绍了一种先进的挥发性有机物(VOCs)排放控制技术,即设备管线组件泄漏检测与修复(LDAR)技术,详细分析了LDAR技术在国内外的实施经验,并探讨了该技术应用于我国石化行业VOCs排放控制的前景.     

Physical characterization of aerosol particles during the Chinese New Year’s firework events

Measurements for particles 10 nm to 10 μm were taken using a Wide-range Particle Spectrometer during the Chinese New Year (CNY) celebrations in 2009 in Shanghai, China. These celebrations provided an opportunity to study the number concentration and size distribution of particles in an especial atmospheric pollution situation due to firework displays. The firework activities had a clear contribution to the number concentration of small accumulation mode particles (100–500 nm) and PM₁ mass concentration, with a maximum total number concentration of 3.8 × 10⁴ cm^?3. A clear shift of particles from nucleation and Aitken mode to small accumulation mode was observed at the peak of the CNY firework event, which can be explained by reduced atmospheric lifetimes of smaller particles via the concept of the coagulation sink. High particle density (2.7 g cm^?3) was identified as being particularly characteristic of the firework aerosols. Recalculated fine particles PM₁ exhibited on average above 150 μg m^?3 for more than 12 hours, which was a health risk to susceptible individuals. Integral physical parameters of firework aerosols were calculated for understanding their physical properties and further model simulation.     

基于OSAT方法对上海2010年夏季臭氧源解析的数值模拟研究

上海夏季臭氧浓度超标现象频繁出现,危害人体健康,已成为一个重要的大气环境问题.本文采用CAMx模型并使用OSAT方法对上海2010年夏季（8月）地面臭氧的源贡献进行了数值模拟研究,探讨了上海本地、浙江、江苏和远距离传输对上海徐汇站O₃浓度的贡献,同时还详细分析了上海本地8类源（农业源、工业过程、工业锅炉、电厂、生活源、交通源和挥发源）的贡献特征.结果表明：在白天O₃低浓度污染时段和夜间,上海徐汇站O₃主要来自外围（最内层模拟区域之外）的贡献.而在白天高浓度O₃污染时段,来自上海市本地污染源排放的贡献率显著地升高.从2010年8月6—31日期间徐汇站O₃小时浓度贡献百分率的平均值来看,外围贡献了61.2%,上海本地、江苏和浙江对上海徐汇站的平均贡献率分别为22.8%、7.4%和8.6%.工业过程是上海本地O₃的最大贡献源,其次是挥发源和交通源,因此,降低上海本地O₃污染浓度的有效措施为控制来自工业过程、挥发源和交通源的O₃前体物的排放.另外,通过OSAT方法模拟计算还得出,上海市交通源、上海电厂和工业过程是徐汇站NO_x浓度（O₃的重要前体物之一）的三大主要贡献源,实施针对该三大重点排放源的减排措施将有效减少上海市的NO_x大气环境浓度.     

基于Urban-RAM模型的上海居民生活碳排放研究

随着全球对碳排放相关研究的不断深入,居民生活引起的能源消耗和碳排放问题引起了研究人员越来越多的关注,但目前鲜有对上海市居民生活整体碳排放的系统研究.本文以2010年为基准年,引入美国劳伦斯伯克利国家实验室开发的Urban-RAM模型,对上海市居民生活碳排放情况进行定量分析,旨在初步掌握上海市居民生活碳排放的总体规模和结构特征,为上海市低碳城市建设和相关决策提供科学依据.研究结果表明,上海市2010年居民生活碳排放总量(CO2e)为4985.7万t,主要以间接排放为主,间接碳排放和直接碳排放分别占居民生活碳排放总量的64.1%和35.9%;上海市居民生活碳排放在各个消费领域的分布不均,直接碳排放主要来自公共和居住建筑领域,该领域的直接碳排量为1065.0万t,占全市居民生活直接碳排放总量的59.5%;间接碳排放主要来自家庭消费领域,该领域的间接碳排量为1625.2万t,占全市居民生活间接碳排放总量的50.9%,其中以食品消费和衣装消费的贡献最大,分别占家庭消费领域碳排放总量的53.5%和29.5%;综合来看,公共和居住建筑领域的整体碳排量最大,为2231.6万t,占全市居民生活碳排放总量的44.8%.     

不同屋面类型径流污染特征研究

了解不同屋面类型对径流污染特征的影响,对控制城市非点源污染具有重要意义.选取不同材质、不同形状和老化程度的典型屋面,采用事件平均浓度（EMC）和M（V）曲线判识方法,对不同屋面类型降雨径流污染浓度、污染负荷和初期冲刷效应进行分析.结果表明,油毡屋面径流污染物平均浓度大于彩钢屋面;老化材料径流污染物平均浓度大于未老化屋面,未老化油毡屋面降雨冲刷效应更为明显;尖形顶屋面相比弓形顶屋面初期冲刷效应更为明显.