2014年北京APEC期间大气醛酮污染物的污染特征与来源分析

于2014年11月北京APEC会议前后,调查了大气醛酮污染物的变化规律及污染特征. 结果表明甲醛、乙醛和丙酮是主要污染物,占总醛酮污染物的82.66%,特别是甲醛,约占40.12%. APEC会议期间北京采取相关措施后,总醛酮污染物浓度下降了64.10%,醛酮污染物在会议前后的变化趋势与PM_2.5等污染物相似. 会议期间和会议后甲醛、乙醛、丙酮和总醛酮污染物之间(R²为0.67~0.98)的相关性较好,说明其有相同来源; 但会议前的相关性较弱,(R²-0.11~0.42和R² 0.16~0.94),说明其来源不同. 计算所得的诊断参数如C1/C2、C2/C3和OC/EC比值显示,会议前来自汽车尾气与燃煤的复合源,而会议期间和会议后燃煤排放比例增加,特别是在会议后.     

南京市大气细颗粒物(PM2.5)中硝基多环芳烃污染特征与风险评估

硝基多环芳烃是大气细颗粒物中具有致癌效应的一类重要污染物,为探明硝基多环芳烃污染特征与来源,采集南京市14个大气细颗粒样品,利用气相色谱-质谱联用仪（GC-MS）测定硝基多环芳烃浓度,进行分布特征分析,来源识别和健康风险评估.结果表明,南京市大气细颗粒物中2,8-二硝基二苯并噻吩（743 pg·m^-3）、2,7-二硝基芴（331 pg·m^-3）、9-硝基蒽（326 pg·m^-3）、3-硝基荧蒽（217 pg·m^-3）和1,8-二硝基芘（193 pg·m^-3）为主要的硝基多环芳烃;硝基多环芳烃检出浓度具有明显的季节变化,冬季最高（3082 pg·m^-3）,秋季其次（1553 pg·m^-3）,春季最低（1218 pg·m^-3）.南京市大气细颗粒物中硝基多环芳烃主要来自多环芳烃大气光氧化反应与生物质燃烧,二次生成是硝基多环芳烃的重要来源.当前南京PM_2.5中硝基多环芳烃的致癌风险可控,二硝基多环芳烃是致癌风险的主要来源.     

典型排放源黑碳的稳定碳同位素组成研究

采集了我国主要的黑碳排放源(生物质燃烧、民用燃煤和机动车尾气)的烟尘样品,分析烟尘中黑碳(BC)和总碳(TC)与原始燃料的稳定碳同位素组成(δ13C),对比各种δ13C值之间的关联性,评估运用δ13C技术进行BC源解析的潜力.结果表明:①3种典型排放源烟尘样品的δ13CBC与燃料有较好的一致性,且不同排放源的δ13CBC变化范围之间有比较明显的差别:生物质燃料除玉米秸(C4植物,δ13CBC为-13.62‰)显著不同外,C3植物的δ13CBC平均值为-26.49‰±1.17‰;烟煤的平均值为-23.46‰±0.37‰;机动车尾气(包括柴油车和汽油车)的平均值为-25.17‰±0.40‰.②各种排放源的BC形成过程存在程度各异的碳同位素分馏,C4植物(玉米秸)燃烧过程分馏作用较明显(BC的δ13C相对燃料负偏1.62‰),而C3植物和民用煤燃烧过程的分馏较小(分别正偏0.63‰和0.52‰).③BC的纯化手段(CTO-375方法)对生物质烟尘的δ13C有一定的影响(BC和TC的δ13C相差约为0.50‰),对化石燃料烟尘没有影响.上述典型排放源的δ13C数据库可为BC源解析提供依据.     

燃料燃烧排放系数的研究

鉴于目前仍未有一套完整的燃料燃烧排放系数 ,文章主要以广州市为对象 ,通过大量的调查和深入的研究 ,使用五种不同的方法 ,得到一套适用于各种燃料及不同燃烧方式的排放系数 ,使通过燃料消耗量推算大气污染物排放量更方便准确     

Safety parameters for oxygen-enriched flames

The utilization of low-quality gaseous fuel from biomass gasification and the abundance of oxygen-rich streams obtained as a by-product of nitrogen-air separation by membrane technology has incentivized the development of sustainable oxygen-enriched combustion technologies in the last decades. However, a dearth of experimental and numerical analysis addressing the reactivity and safety aspects of these mixtures at initial low temperatures can be observed in the current literature.In this work, the heat flux burner was adopted for the measurement of the laminar burning velocity of methane in oxygen enriched air at different equivalence ratios. Results were compared with numerical data obtained by means of detailed kinetic mechanisms developed at the University of Bologna and the Gas Research Institute (GriMech3.0). Simplified correlations for the estimation of the laminar burning velocity with respect to the oxygen content at any equivalence ratio were developed, tested and evaluated.An elemental reaction-based function was found appropriate for the estimation of the overall reactivity of the investigated mixtures. Besides, numerical analyses were performed to characterize the flame structures in terms of temperature and product distribution under several initial conditions. These results gave further insights into the reaction mechanisms of gaseous fuels in the case of oxygen-enriched air, highlighting potential bottlenecks for kinetic model refinements. Eventually, relevant safety parameters were estimated, in particular the flammability range of the fuel/oxidant mixture, in terms of lower and upper flammability limits.     

夏季大空间内火灾机械排烟效率的研究

采用全尺寸实验对夏季大空间内火灾机械排烟的效率进行了研究.实验过程中主要测量了火源功率和大空间内的烟气温度两个参数.通过分析大空间内烟气温度的分布规律,得到了机械排烟控制下不同火源功率的大空间内稳定的烟气层高度.根据Heskestad羽流模型计算了烟气生成速率,与机械排烟速率比较得到了夏季大空间内火灾机械排烟的效率.实验结果表明,在夏季大空间中,当火源功率不是很大时,大空间内外的温差使得外界补充进来的空气和火灾生成的烟气更加容易发生掺混,导致机械排烟的效率大大降低;按照规范规定的6次换气率进行排烟,在实验的300～1 000 kW的火源功率范围内,夏季大空间内火灾机械排烟的效率约为30%.火源功率的增大,在一定程度上削弱了空气与烟气的掺混,机械排烟的效率略有提高,但是提高的效果并不是很明显.     

Simplified multiple equations' inverse problem of vented vessels subjected to internal gas explosions

This paper analyses the experimental data reported by Höchst and Leuckel (1998) for combustion in partially confined vessels and uses the data from these experiments to establish the burning rate based on a simplified model for the combustion process in such vessels. The model establishes three fundamental parameters which are necessary in characterizing the combustion process. These are: i) the burning rate, ii) the fraction of vent area occupied by burnt gas (or discharge sub-model), and iii) the vent area model (if cover mechanisms with variable vent areas are utilized). A set of independent equations is derived to determine the burning rate according to conservation of mass and volume for each gas fraction separately along with a general equation based on general volume conservation. Using this method we are able to describe the combustion process and examine the effect of various discharge models. The advantages of the model presented here include rapid applicability and a valuable analysis to derive mass burn rate and other useful parameters using experimental data from vented explosions with reasonable residual reactant values. Based on these results, the correct interpretation of the obtained burning rate can be used in order to explain the correct prediction of flame velocity and position according to a reasonable discharge model. The paper also evaluates the suitability of several discharge models for phenomenological models of vented explosions. The most appropriate is a Heaviside step function which considers that only unburnt gas is initially expelled, with that component decreasing and the burnt gas component increasing until finally only burnt gas is expelled. The obtained results in this study can be used to predict the burning rate behavior and the combustion process of similar problems.     

Optimal fire histories for biodiversity conservation

Fire is used as a management tool for biodiversity conservation worldwide. A common objective is to avoid population extinctions due to inappropriate fire regimes. However, in many ecosystems, it is unclear what mix of fire histories will achieve this goal. We determined the optimal fire history of a given area for biological conservation with a method that links tools from 3 fields of research: species distribution modeling, composite indices of biodiversity, and decision science. We based our case study on extensive field surveys of birds, reptiles, and mammals in fire‐prone semi‐arid Australia. First, we developed statistical models of species’ responses to fire history. Second, we determined the optimal allocation of successional states in a given area, based on the geometric mean of species relative abundance. Finally, we showed how conservation targets based on this index can be incorporated into a decision‐making framework for fire management. Pyrodiversity per se did not necessarily promote vertebrate biodiversity. Maximizing pyrodiversity by having an even allocation of successional states did not maximize the geometric mean abundance of bird species. Older vegetation was disproportionately important for the conservation of birds, reptiles, and small mammals. Because our method defines fire management objectives based on the habitat requirements of multiple species in the community, it could be used widely to maximize biodiversity in fire‐prone ecosystems. Historiales de Incendios Óptimos para la Conservación de la Biodiversidad     

基于Boston矩阵的江苏省秸秆焚烧压力-状态-响应评价

构建了江苏省农作物秸秆露天焚烧引起雾霾污染的压力-状态-响应(PSR)模型,运用Boston矩阵方法分析江苏省13个地级市2010-2012年的农作物秸秆露天焚烧压力、状态和响应3个指标,研究表明,江苏省秸秆禁烧工作成效显著,占半数城市秸秆焚烧减排压力仍较大,多数城市在秸秆资源综合利用方面还存在较大提升空间.南京市需重点关注农作物秸秆的综合利用,提高秸秆综合利用水平;苏南地区秸秆利用率较高,资源利用的提升空间有限,需继续推行秸秆禁烧政策;苏中地区秸秆资源利用途径单一,拓宽资源利用渠道是工作重点;苏北地区秸秆焚烧污染现实压力较大,严格的秸秆禁烧政策与资源的综合利用需同时并进.     

农作物秸秆资源化利用技术与发展方向探讨

农业秸秆作为一种可再生能源资源,充分开发利用可促进当地经济发展和能源结构调整,其经济效益是十分可观的。大力发展农作物秸秆利用产业,对于充分利用作物再生资源,增加农民收入,推进科技创新,建立循环经济发展模式和环境友好型社会,具有重要的经济意义和深远的社会意义。