临汾市臭氧污染变化特征、气象影响及输送源分析

结合2014~2020年临汾市臭氧逐小时质量浓度和同期气象数据、再分析数据以及潜在源贡献函数法（PSCF）对临汾市O₃污染时空变化特征、与气象因子的关系以及传输路径及潜在源分布开展研究.结果表明,临汾市近年来臭氧污染日益严重,O₃_8h_max年均质量浓度整体呈现上升趋势,2020年相对于2014年增加78.79%;月变化特征呈现“M”双峰型,季节变化峰值出现在夏季,而日变化受近地面大气光化学过程影响显著,呈较为明显的单峰单谷分布,峰值出现在14：00~16：00.O₃浓度与气温和日照时数呈显著线性正相关,当研究区相对湿度为40%~60%,气温高于20℃,风速区间为2~6m/s时易出现高浓度O₃污染.聚类分析表明临汾市O₃重污染天气期间以短距离输送气流为主,高O₃浓度除受到本地生成影响外,还受到省内临近城市及陕西省中部、河南省北部重工企业排放的大量NO_x和VOCs传输的影响.因此,针对临汾市O₃污染在严格控制本地污染源排放的前提下,必须加强汾渭平原地区的联防联控,才能有效缓解该区域大气污染的连片发生.     

一种考虑环境因素的自动步枪可靠性分析方法

目的 分析环境因素对于自动步枪系统可靠性的影响。方法 首先介绍贝叶斯网络理论,然后将自动步枪系统可靠性建模划分为刚性抛壳机构和弹匣供弹机构两大模块。在此基础上,从设计制造、使用因素和环境因素3个方面进行故障树建模。将故障树转化为贝叶斯模型后,基于给出的底事件失效概率和引入的环境影响因子,计算考虑环境因素带来的共因失效效应时自动步枪系统的可靠度。结果 从系统层面来看,环境因素的影响会使系统的可靠度下降8.1%。结论 在进行自动步枪的系统可靠性分析时,考虑由环境因素带来的共因失效效应更为符合实际情况,不考虑共因失效效应时,往往会高估子系统的可靠度。     

Analysis of herbicide residues by gas chromatography

The extraction and clean‐up, and gas Chromatographic conditions for the detection and determination of herbicides, their metabolites and related compounds are reviewed. The literature material is examined critically in the text and presented in tabular form for quick reference. The section dealing with extraction/clean‐up techniques is sub‐divided with respect to water, soil, plant material, animal, fish and micro‐organisms. Under eight herbicide group headings the important gas Chromatographic parameters such as stationary phase, support phase, column temperature and mode of detection are tabulated. Also tabulated are the application of various detectors to herbicide analyses and limits of detection where information was available. Most commonly used liquid and support phases are listed and their frequency of use given. Different aspects of derivative formation used for the positive identification and quantitation of herbicides are discussed with emphasis on esterification, alkylation and silylation. Other important conversion techniques are outlined, particularly those associated with enhancement of sensitivity e.g. bromination, iodination, dinitrophenylation etc. Efforts that have been made towards general and automated analytical methods are discussed.     

Unignited High-Pressure Methane Jet Impinging a Pipe Rack: Practical Tools for Risk Assessment

Although the diffusion of its storage and transport under liquefied conditions, nowadays it is common to have methane in gaseous form in several industrial applications. This leads to safety implications to be considered: hazards are linked to both the high-pressure at which the gas is kept and to its flammability. Scenarios where flammable jets impact an obstacle are of paramount importance because of their possible occurrence. Following a numerical approach, literature shows up that their assessment can be reliably performed by means of only Computational Fluid Dynamics tools. However, despite the improvements of computing power, Computational Fluid Dynamics costs still limit its use in daily risk analysts’ activities. Therefore, considering an accidental jet-obstacle scenario of industrial interest, the present work investigates how a pipe rack can influence the development of a high-pressure methane jet. Based on a Computational Fluid Dynamics analysis, main achievements of this work are a simple criterion able to identify the situations where the pipe rack does not influence the high-pressure methane jet behavior, therefore allowing to identify the scenarios where simpler models can be used (i.e., analytical correlations known for the free jet situation), and, if present, a simple analytical relationship that roughly predicts the influence of the pipe rack without the need of performing complex Computational Fluid Dynamics simulations.     

Influence of influent on anaerobic ammonium oxidation in an Expanded Granular Sludge Bed-Biological Aerated Filter integrated system

Shortcut nitrification-denitrification, anaerobic ammonium oxidation (ANAMMOX), and methanogenesis have been successfully coupled in an Expanded Granular Sludge Bed-Biological Aerated Filter (EGSB-BAF) integrated system. As fed different synthetic wastewater with chemical oxygen demand (COD) of 300–1200 mg·L^-1 and NH4+-N of 30–120 mg·L^-1 at the outer recycle ratio of 200%, the influence of influent on ANAMMOX in the integrated system was investigated in this paper. The experimental results showed that higher COD concentration caused an increase in denitrification and methanogenesis but a decrease in ANAMMOX; however, when an influent with the low concentration of COD was used, the opposite changes could be observed. Higher influent NH4+-N concentration favored ANAMMOX when the COD concentration of influent was fixed. Therefore, low COD/NH4+-N ratio would decrease competition for nitrite between ANAMMOX and denitrification, which was favorable for reducing the negative effect of organic COD on ANAMMOX. The good performance of the integrated system indicated that the bacterial community of denitrification, ANAMMOX, and methanogenesis could be dynamically maintained in the sludge of EGSB reactor for a certain range of influent.     

干旱区云凝结核分布及其影响因子的观测研究

利用DMT CCN仪对宁夏盐池、银川地区地面及高空的云凝结核(CCN)进行实时连续观测.大量资料分析结果表明, CCN日变化明显,受人为因素影响,清晨和傍晚出现高值.夜晚温度与CCN浓度呈正相关,白天相反;强降水对CCN具有一定冲刷作用;沙尘气溶胶没有有效增加盐池地区的CCN浓度.与华北地区比较,银川、盐池地区CCN浓度偏低.此外,研究表明,过饱和度越高,活化CCN浓度越大.根据N=CSK拟合活化谱,银川属于典型大陆性核谱.由于云内清除作用,高空CCN浓度下降明显,但逆温层的存在使得该区CCN浓度累积增加.     

深圳市夏季臭氧污染研究

以2009年8月为例分析了深圳市夏季臭氧污染情况及污染气象特征,基于二维空气质量模式对臭氧污染控制进行数值模拟. 结果表明:深圳市８月各监测点均存在臭氧超标现象,污染形势严峻;副热带高压控制和热带气旋外围下沉气流是造成夏季出现高浓度臭氧的主要天气过程,此时大气边界层混合层高度在500～800 m,且近地面风速约在5 ms以内,不利于污染物扩散;臭氧的生成受前体物挥发性有机物(VOC)和氮氧化物(NO_x)排放的共同影响,其中VOC排放的影响较大,深圳市臭氧控制应以降低VOC排放量为重点,模拟得出对VOC和NO_x按25∶1～40∶1的比例协同减排可有效降低臭氧污染.      

北京夏季典型臭氧污染分布特征及影响因子

为研究北京地区O₃分布特征及其影响因子,利用AML-3车载式大气环境污染激光雷达系统(下称AML-3)对北京地区2011年5月7日—6月9日的φ(O₃)进行观测. 通过AML-3自带的污染物地面观测系统和差分吸收激光雷达,分析近地面、高空φ(O₃)时空分布特征,并将φ(O₃)与温度、风速及风向3个气象要素进行相关分析. 结果表明:近地面φ(O₃)日变化明显,06:00左右为低谷,下午14:00左右达到峰值. 高空φ(O₃)的空间分布很不均匀,上层气流易使O₃富集层向下输送造成污染,同时稳定边界层对大气扩散的不利影响也是形成O₃污染的重要原因. φ(O₃)的日变化趋势与温度的日变化趋势呈显著正相关,R(相关系数)为0.74;上下层湍流交换使风速与近地面φ(O₃)呈正相关,而水平扩散使二者呈负相关;通过分析风向的分布规律发现,东北风易造成北京地区O₃污染.      

北京4种阔叶绿篱球的减噪效应及其影响因子

运用AWA6288型多功能声级及TmeRTA音频分析软件等仪器对北京4种常见阔叶绿篱球的减噪功能进行了测定,并对其结构特征进行了定量化统计,以探寻与植物减噪密切相关的影响因子。结果表明：小叶黄杨球（Buxus microphylla）平均相对A声级减噪能力最强,为1．76dB／m;紫叶小檗球（Berberis thunbergii cv．atropurpurea）相对最差,为1．05dB／m。紫叶小檗球与大叶黄杨球（Euonymus japonicus）、小叶黄杨球、金叶女贞球（Ligustrum vicaryi）在平均相对A声级减噪能力、减噪率方面均存在冠著差异。影响单株植物减噪排名前5的相关结构因子分别是树冠体积（0．804）、冠高（0．781）、绿篱高度（0．733）、叶质地（0．690）、平均冠宽（0．679）;叶大小、冠层、叶质地和倾斜状态、叶密度、枝密度5个主因子的累积方差贡献率已达85．233％,在绿化减噪应用中要重点考虑这5个因子。大叶黄杨球平均相对A声级减噪能力随植株大小变化没有显著变化,与树体各结构因子不相关,这可能与研究的样本量较少或者树体结构特征差异不明显有关;影响不同种类植物减噪的相关因子不尽相同。     

深圳市酸雨变化特征及形成原因分析

深圳市长年属于较重酸雨区,对城市生态带来重要影响,酸雨污染已经成为当前迫切需要解决的环境问题。为了了解近年来深圳市降水的变化特征及污染状况,利用2001—-2011年的降水监测数据,分析了降水酸化程度及化学组分特征,探讨了致酸原因,’为酸雨污染控制对策制定提供基础依据。研究结果表明,深圳市酸雨污染在2004--2006年达到较高水平（降水pH值4,49～4．59）,2007年以来明显有所改善（降水pH值4．73～5．02）,酸雨频率也显著降低。在时间变化上呈现夏季酸雨污染相对较严重,在空间变化上表现出宝安区和龙岗区酸雨污染相对较轻。相对于北京等城市,深圳市降水中离子浓度较低,同时大气中污染物浓度也较低,表明深圳市降水比较清洁,但由于大气中碱性物质含量较低,导致降水酸性较强。深圳市近年降水[SO42-]／[NO3-]的比值不断下降并低于2,硫酸硝酸混合型酸雨特征明显,表明机动车对降水酸性的影响不断增强。Cl-和Na＋对降水阴阳离子的贡献较高（分别达到24％和30％）,反映降水受海洋的影响较大。深圳与广州、东莞、佛山等城市的降水酸度和酸雨频率变化趋势较为一致,区域传输对酸雨形成也有重要影响。