NOAA Chemical Sciences Laboratory, Boulder, Colorado 80305, United States.
Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado 80309, United States.
Environ Sci Technol. 2021 Apr 20;55(8):4332-4343. doi: 10.1021/acs.est.0c05471. Epub 2021 Mar 15.
Despite decades of declining air pollution, urban U.S. areas are still affected by summertime ozone and wintertime particulate matter exceedance events. Volatile organic compounds (VOCs) are known precursors of secondary organic aerosol (SOA) and photochemically produced ozone. Urban VOC emission sources, including on-road transportation emissions, have decreased significantly over the past few decades through successful regulatory measures. These drastic reductions in VOC emissions have led to a change in the distribution of urban emissions and noncombustion sources of VOCs such as those from volatile chemical products (VCPs), which now account for a higher fraction of the urban VOC burden. Given this shift in emission sources, it is essential to quantify the relative contribution of VCP and mobile source emissions to urban pollution. Herein, ground site and mobile laboratory measurements of VOCs were performed. Two ground site locations with different population densities, Boulder, CO, and New York City (NYC), NY, were chosen in order to evaluate the influence of VCPs in cities with varying mixtures of VCPs and mobile source emissions. Positive matrix factorization was used to attribute hundreds of compounds to mobile- and VCP-dominated sources. VCP-dominated emissions contributed to 42 and 78% of anthropogenic VOC emissions for Boulder and NYC, respectively, while mobile source emissions contributed 58 and 22%. Apportioned VOC emissions were compared to those estimated from the Fuel-based Inventory of Vehicle Emissions and VCPs and agreed to within 25% for the bulk comparison and within 30% for more than half of individual compounds. The evaluated inventory was extended to other U.S. cities and it suggests that 50 to 80% of emissions, reactivity, and the SOA-forming potential of urban anthropogenic VOCs are associated with VCP-dominated sources, demonstrating their important role in urban U.S. air quality.
尽管美国城市的空气污染已经减少了几十年，但在夏季仍会发生臭氧超标和冬季颗粒物超标事件。挥发性有机化合物（VOCs）是二次有机气溶胶（SOA）和光化学反应产生臭氧的已知前体。在过去几十年中，通过成功的监管措施，包括道路交通排放在内的城市 VOC 排放源显著减少。这些 VOC 排放量的大幅减少导致城市排放分布和非燃烧源 VOC 的变化，如挥发性化学产品（VCP）等，这些 VOC 现在占城市 VOC 负荷的更高比例。鉴于排放源的这种转变，量化 VCP 和移动源排放对城市污染的相对贡献至关重要。本研究进行了 VOC 的地面站点和移动实验室测量。选择了科罗拉多州博尔德市和纽约市（NYC）两个人口密度不同的地面站点，以评估 VCP 在 VCP 和移动源排放混合物不同的城市中的影响。采用正矩阵因子分解法将数百种化合物归因于移动源和 VCP 源。VCP 源分别占博尔德和纽约市人为 VOC 排放的 42%和 78%，而移动源排放分别占 58%和 22%。分配的 VOC 排放量与基于燃料的车辆排放和 VCP 清单估算的排放量进行了比较，大部分化合物的比较结果在 25%以内，超过一半的化合物在 30%以内。评估清单扩展到了其他美国城市，结果表明，50%至 80%的城市人为 VOC 排放、反应性和 SOA 形成潜力与 VCP 源有关，这表明它们在美国城市空气质量中具有重要作用。
