Size distribution and chemical characteristics of particles from crop residue open burning in North China

Crop residue open burning is an important emission source of ambient particles in China. This study analyzed the particle emission characteristics of crop residue open burning through combustion experiments with a novel open combustion simulation device using three typical crop straws in north China (corn, wheat, and rice). Particle samples size ranging from 0.006–9.890 µm were collected by an Electrical Low Pressure Impactor plus, a high size-resolution instrument capable of dividing particles into 14 size stages. The size distributions of organic carbon (OC), elemental carbon (EC), water-soluble ions, and elements were analyzed, and source chemical profiles were constructed for PM_0.1, PM₁, PM_2.5, and PM₁₀. The number concentration of particles was concentrated in the Aiken nuclei mode (0.006–0.054 µm), accounting for 75% of the total number, whereas the mass concentration was concentrated in the accumulation mode (0.054–0.949 µm), accounting for 85.43% of the mass loading. OC, EC, Cl^?, and K(include total K and water-soluble K) were the major chemical components of the particles, whose mass percentage distributions differed from those of other components. These five main components exhibited a bell-shaped size distribution in the 0.006–9.890 µm range, whereas the other components exhibited a U-shaped distribution. Among the chemical profiles for PM_0.1–PM₁₀, OC was the most important component at 10–30%, followed by EC at 2%–8%. The proportions of K⁺, Cl^?, and K varied substantially in different experimental groups, ranging from 0–15%, and K⁺ and Cl^? were significantly correlated (r = 0.878, α = 0.000).     

云南拱王山地区全新世以来的环境变化记录

对云南小江流域拱王山狐狸房峰南北两侧的老碳房(海拔3 597 m)及石板塘(海拔3 689 m)冰川湖泊沉积剖面进行地球化学元素和孢粉分析,结合14C年代,探讨了研究区全新世以来的气候环境。结果表明,该区全新世主要经历了6次较明显的气候波动,即8.4~7.7 ka气候凉湿;7.7~6.5ka气候冷湿;6.5~4.7 ka气候冷干;4.7~2.1 ka气候凉湿;2.1~1.0 ka气候温湿;1 ka至今气候以暖湿为主。此分析结果反映了本区全新世以来各个不同时段的气候变化与东南季风、西南季风的双重影响印记,与目前中国全新世新冰期与高温期交替及其气温变化规律有一定的耦合与差异。     

Simulation of three-stage operating temperature for supersaturation water-based condensational growth tube

In order to realize accurate dynamic control of supersaturation and to study condensation growth characteristics of nanoparticles through different levels of super saturation,a series of parametric analyses and systematic comparisons between two-stage and three-stage operating temperature designs were simulated with COMSOL Multiphysics.The simulation results showed that the three-stage operating temperature did not change peak supersaturation compared with two operating temperatures,and the three-stage operating temperature was superior in decreasing the amount of water vapor and the temperature,thus lowering particle loss and variation in detection and collection.The peak supersaturation level increased by 0.3 as the flow rate increased from 0.6 to 2.0 L/min,but the supersaturation peak moved from 0.0027 z0 to 0.08 z0(i.e.,the growth time and the final size decreased by 40%).Peak supersaturation increased as the temperature difference increased or the temperature difference window was shifting left,and minimum activation size decreased.Shifting the 70℃temperature difference window from 9℃,79℃-1℃,71℃for the condenser and initiator temperatures resulted in peak supersaturation in the centerline being above 5.8,and the activation size changed as low as 1 nm.Experiments with flow rates varying by a factor of 2.5(from 0.6 to 1.5 L/min) resulted in a final size decrease of 43%(from 3.2 to 1.8 μm),and experimental results of outlet particle size distributions were equivalent with theoretical analysis as the operating temperature was changed.     

装备全寿命周期环境适应性评价若干问题探讨

分析了装备全寿命周期不同阶段的环境适应性评价工作内容,对装备全寿命周期的环境剖面进行分析并提出了其一般结构,介绍了不同阶段的事件及环境。探讨了不同阶段环境适应性评价的要点,提出了环境适应性评价程序和要求。     

某型航空包装箱加速试验方法研究

目的激发航空包装箱使用寿命内的潜在薄弱环节。方法基于寿命期剖面和故障机理分析,采用时间压缩、事件压缩和加速应力的加速方法,设计一种综合考虑湿热、随机振动、叉运、人工拆装、冲击和跌落的多应力加速试验方法。结果该试验将模拟包装箱16年使用寿命的试验时间加速至96天,有效地激发了产品金属紧固件锈蚀、结构件部分损坏等潜在故障,进而通过改进措施提升了包装箱的可靠性水平。结论该方法用于多应力加速试验合理可行。     

系统级可靠性试验技术探讨

论述了开展系统级可靠性试验的重要意义,分析了系统级可靠性试验中需要解决的主要技术问题.首先进行系统可靠度验证,然后根据系统结构及工作环境设计试验方案及试验剖面,并合理设计试验夹具以保证试验评估结果的准确性.用实例证明了系统级可靠性试验的实用性与有效性.     

喷气式飞机设备可靠性试验剖面的计算机辅助设计

主要介绍了喷气式飞机设备可靠性综合试验剖面的计算机辅助设计软件的设计方法和实现的功能．并给出了某喷气式飞机设备的可靠性综合试验剖面的设计实例。     

佛山市典型铝型材行业表面涂装VOCs排放组成

选取佛山市典型铝型材行业不同表面涂装工艺(溶剂型涂料涂装、水性涂料涂装、电泳涂装、粉末喷涂)有组织废气VOCs进行了采样分析.结果表明,溶剂型涂料涂装废气VOCs浓度(63. 90~149. 67 mg·m~(-3))要远大于其他3种涂装工艺(2. 99~21. 93 mg·m~(-3)). VOCs组成来看,溶剂型涂料涂装废气VOCs以芳香烃为主,比例在52. 32%~71. 55%之间,主要污染物包括甲苯、乙苯、二甲苯等苯系物和乙酸乙酯等含氧挥发性有机物(OVOCs).水性涂料涂装废气以OVOCs为主,如乙酸乙酯(48. 59%)、四氢呋喃(8. 43%),芳香烃比例(11. 32%)远低于溶剂型涂料涂装废气.异丙醇是电泳涂装废气中最主要的VOCs化合物,贡献比例高达81. 19%.而粉末涂料涂装废气VOCs污染物主要是丙酮(30. 25%),以及丙烷(15. 48%)、乙烯(12. 15%)、乙烷(9. 35%)、正丁烷(5. 16%)等C2~C4的烷烃和烯烃.臭氧生成潜势(OFP)计算结果表明,溶剂型涂料涂装废气排放单位质量VOCs的臭氧生成潜势(OFP,以O3/VOCs计,下同)最高(3. 89 g·g~(-1)),其次是粉末喷涂(2. 53 g·g~(-1)),而水性涂料涂装和电泳涂装则较低(1. 31 g·g~(-1)和0. 85 g·g~(-1)).溶剂型涂料涂装废气中芳香烃对OFP贡献比例高达93. 28%,有9种C7~C10芳香烃位列OFP排名前10化合物;水性涂料涂装废气中乙酸乙酯、间/对-二甲苯和甲苯的臭氧生成潜势占比最高,分别为23. 24%、21. 76%和17. 07%;粉末涂料涂装废气中的关键活性组分则为乙烯、丙烯和1-丁烯等低碳烯烃,烯烃对其OFP贡献为71. 11%;电泳涂料涂装废气中异丙醇的OFP贡献(65. 08%)明显高于其他组分(6%).     

典型地方炼化企业VOCs排放特征及其对二次污染生成的贡献

为研究石化行业VOCs的排放特征及其环境影响,选取山东省3家典型地方炼化企业开展样品采集和物种分析,并利用MIR(最大增量反应活性)法和SOAP(二次有机气溶胶生成潜势)法量化其对二次污染生成的贡献.结果表明,不同生产类型企业VOCs排放组成差异较大.从体积浓度来看,企业A各采样点位以芳香烃(30.4%~92.2%)为主要排放化合物;企业B排放以烷烃(15.4%~53.8%)、烯炔烃(11.4%~71.7%)和含氧VOCs(0.1%~53.8%)为主;企业C则主要排放烷烃(6.1%~95.3%)和烯炔烃(1.2%~93.1%).从合成源谱来看,企业A以芳香烃为主要化合物,乙苯、苯、苯乙烯、甲苯为高排放物种;企业B中烷烃、烯炔烃和含氧VOCs均有较高占比,1-丁烯、甲基乙基酮、反-2-丁烯、异丁烷、甲苯为主要物种;企业C则主要排放烷烃类化合物,包括异丁烷、丙烷、环戊烷.OFP(臭氧生成潜势)评估结果表明,芳香烃化合物包括乙苯、苯乙烯、苯和甲苯,其对企业A的贡献最大;企业B中,烯炔烃化合物包括1-丁烯、反-2-丁烯、异戊二烯,其OFP占比最高;企业C则以烯炔烃和烷烃为高贡献化合物,其中丙烯、异丁烷、间/对-二甲苯、顺-2-丁烯为关键活性物种.SOAP评估结果表明,各企业SOA(二次有机气溶胶)的生成均由芳香烃主导,关键活性物种为甲苯、苯乙烯、苯、间/对-二甲苯.研究显示,地方炼化企业所排的VOCs组分复杂且存在显著的工艺差异,应根据筛选出的关键活性组分制定针对性的VOCs减排策略.      

北京典型土壤剖面中饱和烃的组成及垂向分布特征

分析了北京地区不同环境功能区具有代表性的10个土壤剖面样品中饱和烃污染物的含量和组成特征.结果表明,不同剖面饱和烃的浓度差别明显,其变化范围为1.5～54.1 μg·g-1,其中城区(B7)、污灌农田(B9)和工业区(B10)浓度较高.所有的剖面均检出了正构烷烃、类异戊间二烯烷烃、烷基环己烷和甾、萜类等饱和烃污染物,大部分剖面中各类化合物的相对含量为正构烷烃＞类异戊间二烯烷烃＞甾萜类＞烷基环己烷,而且在表层土中正构烷烃的含量明显占优势.不同剖面中饱和烃浓度随深度增加而降低,在表层30 cm内饱和烃含量随深度增加而明显降低,40 cm以下含量基本保持恒定,且与有机碳含量的变化趋势基本一致,地球化学参数(如CPI1、CPI2、甾萜类生物标志物参数等)分析表明,城区表土(B7)主要受化石燃料污染,而其它剖面表土正构烷烃主要来源于高等植物,但也受不同程度的化石燃料及其燃烧产物的污染;剖面深部土样中正构烷烃来源与表层土不同,其来源与土壤本身或成土母岩中所含的有机质的地球化学演化有关,而甾萜类化合物和烷基环己烷与表层土中的来源可能基本相同.