• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Investigating Cloud Condensation Nuclei Activity and Particle Growth of Aging Diesel Exhaust Particles
【24h】

Investigating Cloud Condensation Nuclei Activity and Particle Growth of Aging Diesel Exhaust Particles

机译：研究老化的柴油机尾气颗粒的云凝结核活性和颗粒生长

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Soot particles are an essential atmospheric constituent because of their effects on human health, regional and global climate. The impact of soot on climate and human health depends on their ability to interact with water vapor. Freshly emitted soot particles are hydrophobic but the chemical and physical transformations (aging) they undergo while airborne can make them hydrophilic enough to retain water and act as nuclei for cloud formation. The aging of soot is a complicated process and represents a significant uncertainty in quantifying the net radiative forcing of soot particles. In this study, the cloud condensation nuclei (CCN) activity and the secondary organic aerosol formation of diesel exhaust aged in the presence of one or more of the following: UV-radiation, alpha-pinene, and ammonium sulfate seed particles were investigated. Four sets of experiments (diesel exhaust, diesel exhaust + alpha-pinene, diesel exhaust + ammonium sulfate seed particle, and diesel exhaust + alpha-pinene + ammonium sulfate seed experiments) were conducted. The changes in size distribution, number concentration and CCN activity of the aged diesel exhaust particles were monitored with Scanning Mobility Particle Sizer (SMPS) and Cloud Condensation Nuclei Counter (CCNc).;Results from dark experiments with diesel exhaust alone reveal no significant secondary organic aerosol (SOA) formation, nor CCN activation for fresh and aged diesel exhaust particles, as indicated by decreases in particle mass with time (mass decreased by a factor of 0.3), near zero kappa (kappa CCN ~ 0) and activation ratio (< 1%) values at all times, and large critical diameters. xx Aging of diesel exhaust particles in the presence of UV- radiation in the diesel exhaust experiments resulted in a significant increase in mass (increased by factor of 1.0-1.4), kappa value (ranging from 0.03--0.08), activation ratio (ranging from 0.1--0.75), and a substantial decrease in critical diameter after 200 minutes of aging.;The addition of 39 ppbv of alpha-pinene (diesel exhaust + alpha-pinene experiments) further enhanced CCN activation and SOA formation of diesel exhaust particles exposed to UV radiation. kappaCCN values (0.08--0.15) and particle mass (increased by a factor 1.4--1.7) increased further by 88% and 21%, respectively, when compared to the diesel exhaust experiments. Also, the addition of alpha-pinene reduced the particle diameter required for activation.;Experiments with a mixture of diesel exhaust and ammonium sulfate seed particles under UV and dark conditions investigated the effect on ammonium sulfate seed particles on SOA formation and CCN activation. Over the course of an experiment, particle mass in dark experiments decreased by a factor of 0.9--0.8, while particle mass in the UV experiments increased by a factor of 1.1--1.2. The result shows that SOA formation was higher for diesel exhaust experiments than when a mixture of diesel exhaust and ammonium seed particle were exposed to UV radiation. kappaCCN of the aged particles, which seems to be correlated with the ammonium sulfate fraction and the % increase in particle mass, was found to range from 0.02--0.3 for UV experiments.;The addition of 39 ppbv of alpha-pinene to the mixture of diesel exhaust and ammonium sulfate had a significant effect on particle mass (increased by 60%) but no discernible effect on kappaCCN when compared to diesel exhaust +ammonium sulfate experiments.;The results from this study underscore the importance of exposure to sunlight (UV), mixing with water-soluble particles, such as ammonium sulfate, and SOA precursors such as gas phase diesel exhaust and alpha-pinene, in transforming hydrophobic soot into more CCN-active particles. The increase in hygroscopicity and CCN activity of aged diesel particles is expected to reduce their atmospheric lifetime.
机译：烟尘颗粒是必不可少的大气成分，因为它们会影响人类健康，区域和全球气候。烟尘对气候和人类健康的影响取决于它们与水蒸气相互作用的能力。新鲜散发的烟灰颗粒具有疏水性，但是它们在空中传播时经历的化学和物理转变（老化）可以使其具有足够的亲水性，以保留水分并充当形成云的核。烟尘的老化是一个复杂的过程，并且在量化烟尘颗粒的净辐射力方面存在很大的不确定性。在这项研究中，研究了以下一种或多种情况下老化的柴油机废气的云凝结核（CCN）活性和次级有机气溶胶形成：UV辐射，α-pine烯和硫酸铵种子颗粒。进行了四组实验（柴油机废气，柴油机废气+α-pine烯，柴油机废气+硫酸铵种子颗粒和柴油机废气+α-pine烯+硫酸铵种子实验）。老化的柴油机排气颗粒的尺寸分布，数量浓度和CCN活性的变化通过扫描移动粒度仪（SMPS）和云冷凝核计数器（CCNc）进行监测。新鲜和老化的柴油机排气颗粒形成气溶胶（SOA），也没有CCN活化，这通过颗粒质量随时间的下降（质量下降了0.3倍），接近κ（κCCN〜0）和活化比（< 1％）值，并且临界直径较大。 xx在柴油机排气实验中，在存在紫外线辐射的情况下，柴油机排气颗粒的老化导致质量（Kappa值（范围为0.03--0.08），活化比（范围为0.03-1.48）显着增加（增加了1.0-1.4的系数）。从0.1--0.75开始），并且老化200分钟后临界直径大大减小;;添加39 ppbv的α-pine烯（柴油排气+α-pine烯实验）进一步增强了CCN活化和柴油机排气颗粒的SOA形成暴露于紫外线辐射。与柴油机尾气实验相比，kappaCCN值（0.08--0.15）和颗粒质量（增加了1.4--1.7）分别分别增加了88％和21％。同样，添加α-pine烯会降低活化所需的粒径。在紫外线和黑暗条件下用柴油机排气和硫酸铵种子粒子的混合物进行的实验研究了硫酸铵种子粒子对SOA形成和CCN活化的影响。在整个实验过程中，黑暗实验中的粒子质量下降了0.9--0.8倍，而UV实验中的粒子质量增加了1.1--1.2倍。结果表明，柴油机排气实验中的SOA生成要比柴油机排气和铵种子粒子的混合物暴露于紫外线辐射时要高。老化的颗粒的kappaCCN似乎与硫酸铵含量和颗粒质量增加的百分比有关，在UV实验中发现其值为0.02--0.3 .;向混合物中添加39 ppbv的α-pine烯与柴油机废气和硫酸铵实验相比，柴油机废气和硫酸铵对颗粒质量有显着影响（增加了60％），但对kappaCCN却没有明显的影响。这项研究的结果强调了暴露在阳光下的重要性）与水溶性颗粒（如硫酸铵）和SOA前体（如气相柴油机废气和α-pine烯）混合，从而将疏水性烟灰转化为更具CCN活性的颗粒。老化的柴油颗粒的吸湿性和CCN活性的增加预计会缩短其大气寿命。

著录项

  • 作者

    Chukwuto, Humphrey Chigozie.;

  • 作者单位

    The University of North Dakota.;

  • 授予单位 The University of North Dakota.;
  • 学科 Chemical engineering.;Engineering.
  • 学位 M.S.
  • 年度 2017
  • 页码 126 p.
  • 总页数 126
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号