碱溶液中DMPO-OH加合物EPR信号形成研究

为考察碱溶液中DMPO-OH加合物的形成情况及其影响因素,以NaOH溶液为对象,利用EPR（electron paramagnetic resonance,电子顺磁共振）技术,通过DMPO（5,5-二甲基-1-吡咯啉-N-氧化物）自旋捕获,对不同条件下NaOH溶液中DMPO-OH加合物的形成及变化规律进行研究,探讨DMPO-OH加合物的生成过程及降解过程反应机制.结果表明:①将DMPO添加到碱溶液中后,在EPR内检测到典型的DMPO-OH四重特征峰（1:2:2:1）,说明碱溶液中形成了DMPO-OH加合物.②紫外光激发下,碱溶液体系能产生更强的DMPO-OH加合物特征信号,暗反应体系次之,可见光条件下最弱.③体系中DMPO-OH加合物的生成与碱溶液浓度密切相关,当c（NaOH）由0.001 mol/L增至2 mol/L时,DMPO-OH加合物的EPR信号峰呈先增后减最终几乎消失的变化趋势.④紫外光照时间对体系中DMPO-OH加合物的存在影响显著,随着光照时间的延长,DMPO-OH加合物的浓度并没有逐渐增高,而是更加倾向于逐渐降低的趋势,这可能是由于形成的DMPO-OH加合物在短时间内被淬灭或分解.⑤碱溶液中DMPO-OH加合物的生成过程为瞬态过程,降解过程占主导,并且紫外光在其生成及降解过程中发挥了重要作用.研究显示,当c（DMPO）为350 mmol/L、c（NaOH）为0.1 mol/L、紫外光照时间为15 min时,碱溶液中DMPO-OH加合物的EPR信号最佳.      

Characteristics of one-year observation of VOCs, NOx, and O3 at an urban site in Wuhan, China

A continuous online observation of ozone and its precursors(NOx, VOCs) was carried out in central urban Wuhan from September 2016 to August 2017. The concentration levels of ozone,NOx, VOCs and their variations in urban Wuhan were analyzed, as well as effects of VOCs on ozone photochemical generation and the main controlling factors for ozone production. During the observation period, the average concentrations of ozone and NOx in Wuhan was 22.63 and30.14 ppbv, respectively, and the average concentration of VOCs was 32.61 ppbv(42.3% alkanes,13.0% alkenes, 10.0% aromatics, 7.3% acetylene, 9.9% OVOCs, and 10.5% halohydrocarbons).Ozone concentration was higher in spring and summer as compared with autumn and winter,wheras VOCs and NOx concentratios were lower in spring and summer but higher in autumn and winter. Aromatics and alkenes, two of VOCs species, showed the highest contributions to ozone formation potential in Wuhan(35.7% alkenes, 35.4 aromatics, 17.5% alkanes, 8.6% OVOCs,1.6% halogenated hydrocarbons, and 1.4% acetylene). Among all VOCs species, those with the highest contribution were ethylene, m-xylene, toluene, propylene and o-xylene. The contribution of these five compounds to the total ozone formation potential concentration was 43.90%.Ozone-controlling factors in Wuhan changed within one day; during the early morning hours(6:00–9:00), VOCs/NOx was low, and ozone generation followed a VOCs-limited regime.However, during the peak time of ozone concentration(12:00–16:00), the ratio of VOCs/NOx was relatively high, suggesting that ozone generation followed a NOx-limited regime.     

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors: Effects of sludge properties

In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity 1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability normal sludge sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.     

沧州市春季NMHCs空间分布特征

2015年春季在沧州市城区、郊区和潜在污染源附近选择了15个采样点进行同期采样.研究表明沧州市NMHCs总体上市区高于近郊及远郊区县;市区以高新区NMHCs浓度最高;郊县采样点除河间市略高外,其它采样点的浓度均明显低于市区浓度;机动车的道路排放是沧州市NMHCs的重要来源之一;沧州大化和沧州炼油在停产期间未对市区NMHCs产生明显影响;大港油田采油三厂采取了较完善的油气回收措施,未对市区NMHCs产生明显影响;平均来看,沧州市NMHCs中烷烃占65%,烯烃占16%,芳烃占19%;臭氧生成潜势(ozone formation potential,OFPs)主要来源于二甲苯(19%)、乙烯(14%)、甲苯(11%)、丙烯(5%)、异戊烷(5%)和异戊烯(5%)等;气溶胶生成潜势(formation potential of secondary organic aerosol,SOAFPs)主要来源于甲苯(28%)、蒎烯(28%)、二甲苯(16%)、乙苯(9%)和苯(9%)等.     

我国人为源挥发性有机物反应性排放清单

以我国人为源挥发性有机物(VOCs)为研究对象,使用具有代表性的VOCs总量排放清单、各污染源成分谱及物种最大增量反应活性值(MIR),建立了2010年我国人为源VOCs基于臭氧生成潜势(OFP)的反应性排放清单.结果表明,2010年我国人为源挥发性有机物总OFP为84 187.61 kt,其中,烷烃6 882.53 kt,烯炔烃41 496.92 kt,芳香烃32 945.32 kt,卤代烃161.45kt,含氧有机化合物2 701.40 kt.OFP贡献前10种物种分别为丙烯、乙烯、间/对-二甲苯、甲苯、1-丁烯、邻-二甲苯、1,2,4-三甲苯、1,3-丁二烯、间-乙基甲苯和乙苯,占人为源总OFP的63.95%,仅占VOCs排放总量的31.84%.人为源三大污染源中,工业源贡献了49.29%的OFP,为最大贡献源,其次是交通源28.31%和农业源22.40%.建筑装饰、石油炼制、储存与运输、机械设备制造、交通设备制造和包装印刷为工业OFP主要贡献源;轻型载客汽车、重型载客汽车及摩托车为交通源OFP污染控制的重点;生物质燃烧两类子源均为农业源OFP重点控制对象.山东、江苏、广东、浙江和河南是我国人为源OFP贡献最大的省份,占人为源总OFP的39.65%.该反应性清单的建立,对我国基于反应性臭氧(O3)控制对策的制定具有重要意义.     

Study on the mechanism of copper–ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper–ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process.     

2008~2010年北京城区大气BTEX的浓度水平及其O3 生成潜势

苯、甲苯、乙苯及二甲苯是典型的人为排放有机物,不仅危害人体健康还参与对流层的光化学反应,生成O3和二次有机气溶胶.为认知北京大气中BTEX的浓度水平,评估其O3生成潜势,于2007年12月～2010年11月使用被动采样和化学分析相结合的方法对BTEX和O3浓度进行了连续3 a的同步观测.结果表明,北京城区大气BTEX中甲苯的浓度高达(8.7±3.1)μg·m-3,其次为苯、乙苯和间对二甲苯,浓度分别为(7.1±3.3)、(4.2±1.4)和(3.4±1.5)μg·m-3.BTEX总浓度在春、夏、秋和冬季的平均值分别为(16.8±1.4)、(24.7±2.8)、(25.9±4.9)和(26.8±12.1)μg·m-3,冬季苯的浓度全年最高,而夏季甲苯浓度高于冬季.采用最大增量反应活性方法计算了北京城区大气BTEX夏季O3生成潜势,发现间对二甲苯的贡献最大.北京2008、2009和2010年夏季BTEX的O3生成潜势分别为65.2、60.2和75.7μg·m-3,与O3实际浓度的年际变化趋势一致(同期浓度分别为80.5、65.0和101.9μg·m-3).机动车尾气和溶剂挥发是北京城区大气BTEX的主要来源,冬季苯的浓度可能受取暖燃煤的影响,夏季溶剂挥发对BTEX影响更大,并对O3的生成有一定贡献.     

对建立第三方事故调查机制的探讨

事故调查的根本目的在于查找事故的可能原因并提出事故的预防措施,而事故调查的独立性对此根本目的起关键作用。我国安全生产管理体制建设起步较晚,事故管理机制发展不成熟,与国外先进事故调查理念相比,我国事故调查机制缺乏独立性的保障,主要表现在技术调查与司法调查未能分离、事故调查报告未能完全公开、事故调查的客观性保障不足,限制了我国事故调查水平的进一步提高。通过分析国外第三方事故调查的机制的优势并结合我国国情,从第三方事故调查的任务、人员编制、人员培训、责任与权利、法律义务等方面提出我国第三方事故调查机制的框架,并规划了构建第三方事故调查的三阶段进程及其主要内容,以逐步实现第三方事故调查的公正、客观、高效,更好地促进我国安全生产管理水平的提高。     

基于损伤-断裂力学理论的起重机疲劳寿命估算方法

鉴于断裂力学无法估算裂纹形成寿命及难以确定其初始裂纹尺寸,提出将损伤力学与断裂力学相结合共同估算起重机疲劳寿命的思想。针对Paris公式应用的局限性,提出将裂纹扩展率与应力强度因子幅对数线性阶段的某一裂纹尺寸作为裂纹形成寿命和裂纹扩展寿命的分界点。用损伤力学估算疲劳裂纹的形成寿命,用断裂力学估算疲劳裂纹的扩展寿命,两者寿命之和构成起重机的疲劳全寿命。这样做既能避免断裂力学寿命估算中确定初始裂纹尺寸的混乱现象;又能确保Paris公式应用在裂纹扩展率与应力强度因子幅的对数线性阶段。试验验证结果表明,估算疲劳全寿命和试验寿命基本吻合。     

湿法烟气脱硫系统结垢腐蚀问题分析

湿法烟气脱硫系统受到管路或全线结垢堵塞腐蚀因素的困扰,脱硫系统无法正常运行,严重时被迫停车处理。脱硫系统结垢腐蚀的成因较复杂,解决的方法应具有针对性,本文对脱硫系统结垢的因素以及防治的方法进行了分析。