Department of Environmental Science, Policy and Management, University of California at Berkeley, Berkeley 94720, California, United States.
Department of Earth and Planetary Science, University of California at Berkeley, Berkeley 94720, California, United States.
Environ Sci Technol. 2023 Oct 17;57(41):15533-15545. doi: 10.1021/acs.est.3c03162. Epub 2023 Oct 4.
Los Angeles is a major hotspot for ozone and particulate matter air pollution in the United States. Ozone and PM in this region have not improved substantially for the past decade, despite a reduction in vehicular emissions of their precursors, NO and volatile organic compounds (VOCs). This reduction in "traditional" sources has made the current emission mixture of air pollutant precursors more uncertain. To map and quantify emissions of a wide range of VOCs in this urban area, we performed airborne eddy covariance measurements with wavelet analysis. VOC fluxes measured include tracers for source categories, such as traffic, vegetation, and volatile chemical products (VCPs). Mass fluxes were dominated by oxygenated VOCs, with ethanol contributing ∼29% of the total. In terms of OH reactivity and aerosol formation potential, terpenoids contributed more than half. Observed fluxes were compared with two commonly used emission inventories: the California Air Resources Board inventory and the combination of the Biogenic Emission Inventory System with the Fuel-based Inventory of Vehicle Emissions combined with Volatile Chemical Products (FIVE-VCP). The comparison shows mismatches regarding the amount, spatial distribution, and weekend effects of observed VOC emissions with the inventories. The agreement was best for typical transportation related VOCs, while discrepancies were larger for biogenic and VCP-related VOCs.
洛杉矶是美国臭氧和颗粒物空气污染的主要热点地区。尽管机动车排放的前体物氮氧化物和挥发性有机化合物有所减少，但该地区的臭氧和 PM 在过去十年中并没有显著改善。“传统”来源的减少使得当前空气污染物前体物的排放混合物更加不确定。为了绘制和量化这个城市空气中广泛的挥发性有机化合物的排放，我们利用小波分析进行了机载涡度协方差测量。测量的 VOC 通量包括了交通、植被和挥发性化学产品（VCPs）等源类别的示踪剂。质量通量主要由含氧 VOC 主导，其中乙醇贡献了约 29%。就 OH 反应性和气溶胶形成潜力而言，萜烯类化合物的贡献超过了一半。观测到的通量与两种常用的排放清单进行了比较：加利福尼亚空气资源委员会清单和生物排放清单与基于燃料的车辆排放清单与挥发性化学产品（FIVE-VCP）的组合。比较表明，观测到的 VOC 排放与清单在数量、空间分布和周末效应方面存在差异。与生物源和 VCP 相关的 VOC 相比，典型交通相关 VOC 的一致性更好。
