State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China.
Environ Pollut. 2021 Jul 1;280:116972. doi: 10.1016/j.envpol.2021.116972. Epub 2021 Mar 20.
Vehicle emission is an important source of ammonia (NH) in urban areas. To better address the role of vehicle emission in urban NH sources, the emission factor of NH (NH-EF) from vehicles running on roads under real-world conditions (on-road vehicles) needs to update accordingly with the increasingly tightened vehicle emission standards. In this study, laser-absorption based measurements of NH were conducted during a six-day campaign in 2019 at a busy urban tunnel with a daily traffic flow of nearly 40,000 vehicles in south China's Pearl River Delta (PRD) region. The NH-EF was measured to be 16.6 ± 6.3 mg km for the on-road vehicle fleets and 19.0 ± 7.2 mg km for non-electric vehicles, with an NH to CO ratio of 0.27 ± 0.09 ppbv ppmv. Multiple linear regression revealed that the average NH-EFs for gasoline vehicles (GVs), liquefied petroleum gas vehicles, and heavy-duty diesel vehicles (HDVs) were 18.8, 15.6, and 44.2 mg km, respectively. While NH emissions from GVs were greatly reduced with enhanced performance of engines and catalytic devices to meet stricter emission standards, the application of urea selective catalytic reduction (SCR) in HDVs makes their NH emission an emerging concern. Based on results from this study, HDVs may contribute over 11% of the vehicular NH emissions, although they only share ∼4% by vehicle numbers in China. With the updated NH-EFs, NH emission from on-road vehicles was estimated to be 9 Gg yr in the PRD region in 2019, contributing only 5% of total NH emissions in the region, but still might be a dominant NH source in the urban centers with little agricultural activity.
车辆排放是城市地区氨（NH）的重要来源。为了更好地确定车辆排放对城市 NH 源的作用，需要根据日益严格的车辆排放标准，相应更新道路上行驶的车辆（道路车辆）的 NH 排放因子（NH-EF）。在这项研究中，2019 年在中国珠江三角洲（PRD）地区一条繁忙的城市隧道中进行了为期六天的测量，采用基于激光吸收的方法测量 NH。该隧道日交通流量接近 40,000 辆，在此期间测量了道路车辆车队的 NH-EF 为 16.6±6.3mg·km，非电动汽车的 NH-EF 为 19.0±7.2mg·km，NH 与 CO 的比例为 0.27±0.09ppbv·ppmv。多元线性回归显示，汽油车（GVs）、液化石油气车和重型柴油车（HDVs）的平均 NH-EF 分别为 18.8、15.6 和 44.2mg·km。虽然 GVs 的 NH 排放由于发动机和催化装置性能的提高，以满足更严格的排放标准而大大减少，但在 HDVs 中应用尿素选择性催化还原（SCR）使其 NH 排放成为一个新的关注点。根据本研究的结果，HDVs 可能贡献超过 11%的车辆 NH 排放，尽管它们在中国仅占车辆数量的 4%左右。根据更新后的 NH-EF，2019 年 PRD 地区道路车辆的 NH 排放量估计为 9Gg·yr，仅占该地区总 NH 排放量的 5%，但在农业活动较少的城市中心，它仍可能是一个主要的 NH 源。
