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首页> 外文期刊>Atmospheric environment >What are the sources and conditions responsible for exceedences of the 24 h PM_(10) limit value (50 μgm~(-3)) at a heavily trafficked London site?
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What are the sources and conditions responsible for exceedences of the 24 h PM_(10) limit value (50 μgm~(-3)) at a heavily trafficked London site?

机译：在伦敦一个交通繁忙的地点，导致超过24小时PM_（10）极限值（50μgm〜（-3））的原因和条件是什么？

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The European Union has set limit values for PM_(10) to be met in 2005. At Marylebone Road, London, where the traffic is heavy, the daily limit value of 50μgm~(-3) is exceeded more than 35 times a year. A total of 185 days with daily PM_(10) concentrations exceeding the limit value of 50 μgm~(-3) measured between January 2002 and December 2004 (data capture of 89.5%) are discussed in this paper. These exceedences were more frequent in early spring and in autumn. Concentrations have been disaggregated into regional, urban (background) and local (street) contributions. Most of the episodes of gravimetric PM_(10) above the limit value were associated with a high regional background and very often the regional contribution dominated the PM_(10) mass. The secondary aerosol (especially the paniculate nitrate) made a major contribution to the PM_(10) load. These situations were frequently observed when air masses came from the European mainland (showing that both emissions from the UK and other EU countries contributed to the exceedences), and less frequently with maritime air masses that have stagnated over the UK (showing that emissions from the UK alone less frequently contributed to the high regional background). However, the higher frequency of episodes breaching the limit value at the roadside site than at the rural site and the higher frequency of PM_(10) concentrations above the limit value on weekdays show that the high regional contributions are additional to local and urban emissions. Local emissions mainly due to traffic were the second important contributor to the exceedences, while the contribution of the urban background of London was less important than the local emissions and the regional background. Applying the pragmatic mass closure model of Harrison et al. [2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927-4933], revealed that the regional aerosol is comprised very largely of ammonium nitrate and sulphate and secondary organic aerosol. Findings suggest that international abatement of secondary aerosol precursors may be the most effective measure to fulfil the requirements of the European Directive 1999/ 30/CE by lowering the regional background.
机译：欧盟已设定了PM_（10）的限值，要在2005年达到。在交通繁忙的伦敦马里波恩路（Marylebone Road），每年超过50μgm〜（-3）的每日限值超过35次。本文讨论了总共185天，在2002年1月至2004年12月之间测得的每日PM_（10）浓度超过了50μgm〜（-3）的极限值（数据捕获率为89.5％）。这些异常在早春和秋季更为常见。集中度分为区域，城市（背景）和本地（街道）贡献。超过极限值的重量PM_（10）的大部分发作都与较高的区域背景有关，并且通常区域贡献占PM_（10）质量的大部分。次级气溶胶（尤其是硝酸颗粒）对PM_（10）的负荷起了主要作用。当空气质量来自欧洲大陆时，通常会观察到这些情况（表明来自英国和其他欧盟国家的排放均是造成超标的原因），而停滞在英国的海洋气团则较少见（表明来自英国的排放量）。仅英国就较少导致较高的区域背景。但是，在路边站点发生的事件高于农村站点的事件发生频率高于农村站点，并且在工作日高于限值的PM_（10）浓度发生频率也更高，这表明较高的区域贡献量是对本地和城市排放的额外影响。主要由于交通造成的局部排放是造成排放量超标的第二重要因素，而伦敦城市​​背景的贡献则不如局部排放和区域背景重要。应用哈里森等人的实用的质量封闭模型。 [2003。一种实用的大规模封闭模型，用于城市背景和路边场所的空气中颗粒物。大气环境37，4927-4933]揭示，该区域的气溶胶主要由硝酸铵和硫酸铵以及次级有机气溶胶组成。研究结果表明，通过降低区域背景，国际减少次级气溶胶前体可能是满足欧洲指令1999/30 / CE要求的最有效措施。

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