Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities
Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities
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DOI：
10.5194/acp-15-9983-2015
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发表时间：
2015-09
影响因子：
6.3
通讯作者：
R. Dunmore;J. Hopkins;R. Lidster;James D. Lee;M. J. Evans;A. Rickard;A. Lewis;J. Hamilton
中科院分区：
文献类型：
--
作者：
R. Dunmore;J. Hopkins;R. Lidster;James D. Lee;M. J. Evans;A. Rickard;A. Lewis;J. Hamilton
抽象的。碳氢化合物是臭氧和颗粒物这两种优先空气污染物的关键前体。从历史上看，碳含量在2到7之间的人很容易观察到，在许多发达城市，通过空气质量政策干预已经成功地减少了碳排放。柴油车排放的长链烃没有被明确视为空气质量战略的一部分，而且对其在大气中的气体丰度的直接测量也很少。这项研究描述了在一个发达的特大城市(伦敦)对有机化合物进行的化学综合和连续测量，结果表明，按季节中位数计算，与柴油有关的碳氢化合物仅占总碳氢化合物混合比的20%-30%，但占大气碳氢化合物质量的50%以上，是二次有机气溶胶的主要局部来源。这项研究首次表明，冬季初级碳氢化合物羟基自由基反应性的60%来自与柴油有关的碳氢化合物，并使用最大增量反应性标度，我们预测它们对伦敦臭氧产生潜力的贡献高达50%。将现实世界的城市组成与英国和美国的监管排放清单进行比较，突出了以前未说明但非常严重的与柴油相关的碳氢化合物的低估；低估了C9物种的~4因子，并在冬季将C12物种的因子上升到70以上。这些观察表明，在柴油车比例较高的城市，柴油车排放的碳氢化合物可能会主导气相活性碳。未来对这些地区的城市颗粒物和臭氧的控制需要将政策重点转移到柴油排放的气相碳氢化合物上，因为这种车辆类型在世界范围内继续取代汽油。
Abstract. Hydrocarbons are key precursors to two priority air pollutants, ozone and particulate matter. Those with two to seven carbons have historically been straightforward to observe and have been successfully reduced in many developed cities through air quality policy interventions. Longer chain hydrocarbons released from diesel vehicles are not considered explicitly as part of air quality strategies and there are few direct measurements of their gaseous abundance in the atmosphere. This study describes the chemically comprehensive and continuous measurements of organic compounds in a developed megacity (London), which demonstrate that on a seasonal median basis, diesel-related hydrocarbons represent only 20–30 % of the total hydrocarbon mixing ratio but comprise more than 50 % of the atmospheric hydrocarbon mass and are a dominant local source of secondary organic aerosols. This study shows for the first time that 60 % of the winter primary hydrocarbon hydroxyl radical reactivity is from diesel-related hydrocarbons and using the maximum incremental reactivity scale, we predict that they contribute up to 50 % of the ozone production potential in London. Comparing real-world urban composition with regulatory emissions inventories in the UK and US highlights a previously unaccounted for, but very significant, under-reporting of diesel-related hydrocarbons; an underestimation of a factor ~4 for C9 species rising to a factor of over 70 for C12 during winter. These observations show that hydrocarbons from diesel vehicles can dominate gas phase reactive carbon in cities with high diesel fleet fractions. Future control of urban particulate matter and ozone in such locations requires a shift in policy focus onto gas phase hydrocarbons released from diesels as this vehicle type continues to displace gasoline world-wide.