Characterization of a new smog chamber for evaluating SAPRC gas-phase chemical mechanism

A new state-of-the-art indoor smog chamber facility (CAPS-ZJU) has been constructed and characterized at Zhejiang University, which is designed for chemical mechanism evaluation under well-controlled conditions. A series of characterization experiments were performed to validate the well-established experimental protocols, including temperature variation pattern, light spectrum and equivalent intensity (J_NO2), injection and mixing performance, as well as gases and particle wall loss. In addition, based on some characterization experiments, the auxiliary wall mechanism has been setup and examined. Fifty chamber experiments were performed across a broad range of experimental scenarios, and we demonstrated the ability to utilize these chamber data for evaluating SAPRC chemical mechanism. It was found that the SAPRC-11 can well predict the O₃ formation and NO oxidation for almost all propene runs, with 6 hr Δ(O₃ – NO) model error of –3% ± 7%, while the final O₃ was underestimated by ~20% for isoprene experiments. As for toluene and p-xylene experiments, it was confirmed that SAPRC-11 has significant improvement on aromatic chemistry than earlier version of SAPRC-07, although the aromatic decay rate was still underestimated to some extent. The model sensitivity test has been carried out, and the most sensitive parameters identified are the initial concentrations of reactants and the light intensity as well as HONO offgasing rate and O₃ wall loss rate. All of which demonstrated that CAPS-ZJU smog chamber could derive high quality experimental data, and could provide insights on chamber studies and chemical mechanism development.     

Exploring the formation potential and optical properties of secondary organic aerosol from the photooxidation of selected short aliphatic ethers

Secondary organic aerosol (SOA) formation potential for six kinds of short aliphatic ethers has been studied. The size distribution, mass concentration, and yield of SOA formed by ethers photooxidation were determined under different conditions. The results showed that all six ethers can generate SOA via reaction with OH radicals even under no seed and NO_x-free condition. The mass concentration for six seedless experiments was less than 10 µg/m³ and the SOA yields were all below 1%. The strong increase in the SOA formation was observed when the system contained ammonium sulfate seed particles, while SOA yield decreased under the high-NO_x condition. SOA composition was analyzed using offline methods. Infrared spectra indicated that there are complex components in the particle-phase including carbonyls acid and aldehydes species. Moreover, the aqueous filter extracts were analyzed using ultraviolet-visible spectrometer and fluorescence spectrophotometer. For the fresh methyl n-butyl ether SOA, the largest absorption peak occurs at 280 nm and there exists slightly absorption in the 300–400 nm. Excitation-emission matrices display the distinct peak at excitation/emission = 470 nm/480 nm according to the fluorescence spectrum. These findings are important considerations of formation for ether SOA that can eventually be included in atmospheric models.     

Reactor characterization and primary application of a state of art dual-reactor chamber in the investigation of atmospheric photochemical processes

Increasing attention has been paid to the air pollution more recently. Smog chamber has been proved as a necessary and effective tool to study atmospheric processes, including photochemical smog and haze formation. A novel smog chamber was designed to study the atmospheric photochemical reaction mechanism of typical volatile organic compounds (VOCs) as well as the aging of aerosols. The smog chamber system includes an enclosure equipped with black lights as the light source, two parallel reactors (2 m³ of each) with separate control of light source and temperature, with a series of coupled instruments for online monitoring of gas phase and particle phase reactants and products. Chamber characterization, including air source stability, effective light intensity, temperature stability, as well as gas phase and particle phase wall losses, were carried out before further research. The results showed that our smog chamber systems developed by other domestic and international groups. It was also observed that the wall loss of aromatic VOCs varied with different functional groups as well as the isomerism. The results of preliminary simulation experiment from styrene-NO_x demonstrated that the chamber can be well utilized to simulate gas-particle conversion progresses in the atmosphere.     

置换通风下不同风速对负离子净化PM_(2.5)的研究

利用人工环境舱进行实验,从衰减常数、去除率等方面分析了在置换通风下不同送风速度对负离子净化PM_(2.5)的影响。结果表明:负离子对PM_(2.5)具有净化作用;随着送风速度的增加,负离子对PM_(2.5)的净化作用先降低后增大。在保证工作区不会产生吹风感的情况下,所选的8个工况中,置换通风送风速度为0.3m/s左右时,负离子对PM_(2.5)的净化效果最佳,净去除率达到20.4%。     

Noise system在道路工程声环境影响预测中的应用研究

采用Noise system模型软件预测城市道路工程对周围敏感目标的影响.通过预测,拟建道路沿线路中心线两侧200 m范围内随距离增大受交通噪声影响呈明显衰减趋势.从路段达标距离分析,相对于昼间噪声达标距离,夜间噪声达标距离均大于昼间的达标距离,说明拟建道路夜间交通噪声影响大于昼间;沿线敏感点近期、中期、远期昼间、夜间噪声预测值均能满足《声环境质量标准》(GB 3096-2008)中2类、4a类标准;通过对首排在建小区均为3层以上建筑物不同垂直高度的影响进行预测,对居民区不会造成影响.     

浅层小尺度隐伏断层地表勘探的正演模拟及应用

采用二维声波方程有限差分法对浅层小尺度隐伏断层地质模型的地震波场响应进行数值模拟,分别从震源位于断层下降盘顶、断层上升盘顶及断层顶三个不同位置进行正演模拟,对地震波场在断层模型中的传播规律及其地震记录变化特征进行了详细分析。结果表明多个单炮记录的变化对比不仅可以对断层进行快速有效的判断,而且为分析断层几何类型、估计断裂带范围与宽度等方面提供重要的依据。同时将模拟结果应用到实际生产中,取得了较好的应用效果。该方法能有效辅助实际野外工作中对断层的判断,为合理设计观测系统及采集参数设置提供指导,对提高浅层地震勘探现场工作效率和精度具有重要作用。     

点声源环境噪声声场区域二维图形化表征方法研究

针对环境噪声监测中单一点声源声场图形化表征机理,依据点声源衰减规律建立了点声源声场二维平面表征算法,据此以网格化区域范围内非均匀布置少量监测点方法确定声源点,再经克里金插值法反演点声源声场平面分布规律,最后通过ArcGIS软件平台实现噪声图形化展示.以5×5网格化区域为例,其非均匀布点数应不少于3个,最佳布点数为3组共计6个点,其实测值与理论值最大误差为4.3％.仿真试验验证表明,点声源图形表征符合实际声场分布规律.     

行波管性能测试用试验箱的结构特点及其设计

介绍了一种专门用于行波管性能测试的试验箱的设计过程。在对试验箱结构特点进行分析的基础上,通过结构设计、制冷系统设计和控制系统设计,尤其在风道结构布局方面的创新设计,成功研制了该型试验箱,并在生产过程中得到了实际应用。     

环境实验室温度均匀性的数值分析研究

目的研究送风参数及围护结构对飞机结构及机构环境条件下功能性和耐久性实验室温度均匀性的影响。方法采用CFD方法对实验室的气流组织进行数值模拟,根据气流组织评价标准对工作区的温度均匀性进行分析。结果送风温差越大、送风速度越小温度场均匀性越差,保温层较厚时,温差过大将导致工作区温度分布达不到设计要求。结论相同温差下,减少送风口数量并提高单个送风口的送风速度有助于提高温度均匀性。     

O3浓度升高对南方城市绿化树种氮素的影响

近地层臭氧(O3)浓度升高会降低树木的光合速率,抑制Rubisco酶的活性,势必会间接影响树木N素的吸收与分配.本研究利用开顶式气室研究过滤大气(CF,<20 nL·L-1)与O3浓度升高(E-O3,约150 nL·L-1)对10种南方城市常用绿化树种幼苗N素吸收和分配的影响.结果表明,与CF相比,E-O3使枫香叶生物量和马褂木茎生物量分别显著降低了20.9%和21.4%,使枫香和马褂木的根生物量显著降低了24.2%和32.5%.O3对被测树种茎中N素含量影响显著,而对叶和根中N素含量无显著影响.O3对被测树种整株树N素吸收总量(Ntu)、叶片N素吸收量及根的N素吸收量存在显著影响,而对茎N素吸收量无显著影响.与CF相比,E-O3使马褂木与木荷的Ntu分别显著降低了28.4%与22.7%,而使舟山新木姜子Ntu显著增加了15.5%.O3浓度升高对各树种N素吸收量在各器官中的分配无显著影响.