Airborne measurements of trace gases and aerosols over the London metropolitan region
Airborne measurements of trace gases and aerosols over the London metropolitan region
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DOI：
10.5194/acp-12-5163-2012
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发表时间：
2011-11
影响因子：
6.3
通讯作者：
G. McMeeking;M. Bart;P. Chazette;J. Haywood;J. Hopkins;J. McQuaid;W. Morgan;Jean-Christophe Raut-Jean-Christophe-Rau
中科院分区：
文献类型：
--
作者：
G. McMeeking;M. Bart;P. Chazette;J. Haywood;J. Hopkins;J. McQuaid;W. Morgan;Jean-Christophe Raut-Jean-Christophe-Rau
2009年6月，在英国大城市伦敦开展了M25高速公路周围排放（EM 25）活动，目的是确定进入城市地区和从城市地区排放的痕量气体和气溶胶的组成和性质。它有两个移动的平台，英国BAe-146空中大气测量设施（FAAM）研究飞机和一个地面移动的激光雷达货车，两者都在伦敦周围的电路中行驶，大致沿着环绕城市的M25高速公路的路径行驶。我们提出了一个概述，从该项目的调查结果，发生在典型的英国夏季污染条件。从伦敦地区排放的挥发性有机化合物（VOCs）的排放率与其他大城市地区的测量和顺风一致，并表示交通和相关的燃料蒸发是主要来源。亚微米气溶胶成分主要由次级物质组成，包括硫酸盐（伦敦羽流中亚微米质量的24%和背景气溶胶中的30%）、硝酸盐（羽流中的24%;背景气溶胶中的18%）和有机气溶胶（羽流中的30%;背景气溶胶中的30%）。与较大的区域背景相比，伦敦的主要亚微米气溶胶排放量较小，与背景相比，城市羽流中的气溶胶质量仅增加有限（平均增加15%）。黑碳质量是主要的例外，在城市羽流中增加了一倍多，并导致单次散射的平均散射系数从背景气溶胶中的0.91下降到伦敦羽流中的0.86。我们的观察结果表明，区域气溶胶似乎占主导地位的城市来源，至少在典型的夏季条件下，这意味着未来的努力，以减少PM水平在伦敦必须占区域以及当地的气溶胶来源。
The Emissions around the M25 motorway (EM25) campaign took place over the megacity of London in the United Kingdom in June 2009 with the aim of characterising trace gas and aerosol composition and properties entering and emitted from the urban region. It featured two mobile platforms, the UK BAe-146 Facility for Airborne Atmospheric Measurements (FAAM) research aircraft and a ground-based mobile lidar van, both travelling in circuits around London, roughly following the path of the M25 motorway circling the city. We present an overview of findings from the project, which took place during typical UK summertime pollution conditions. Emission ratios of volatile organic compounds (VOCs) emitted from the London region were consistent with measurements in and downwind of other large urban areas and indicated traffic and associated fuel evaporation were major sources. Sub-micron aerosol composition was dominated by secondary species including sulphate (24% of sub-micron mass in the London plume and 30% in the background aerosol), nitrate (24% plume; 18% background) and organic aerosol (30% plume; 30% background). The primary sub-micron aerosol emissions from London were minor compared to the larger regional background, with only limited increases in aerosol mass in the urban plume compared to the background (15% mass increase on average). Black carbon mass was the major exception, which more than doubled in the urban plume and lead to a decrease in the single scattering albedo from 0.91 in the background aerosol to 0.86 in the London plume, on average. Our observations indicated that regional aerosol appeared to dominate urban sources, at least during typical summertime conditions, meaning future efforts to reduce PM levels in London must account for regional as well as local aerosol sources.