Qu Zhen, Wu Dien, Henze Daven K, Li Yi, Sonenberg Mike, Mao Feng
Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO, 80309, USA; School of Engineering and Applied Science, Harvard University, Cambridge, MA, 02138, USA.
Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, 84112, USA.
Environ Pollut. 2021 Mar 15;273:116421. doi: 10.1016/j.envpol.2020.116421. Epub 2021 Jan 4.
High concentrations of ground-level ozone affect human health, plants, and animals. Reducing ozone pollution in rural regions, where local emissions are already low, poses challenge. We use meteorological back-trajectories, air quality model sensitivity analysis, and satellite remote sensing data to investigate the ozone sources in Yuma, Arizona and find strong international influences from Northern Mexico on 12 out of 16 ozone exceedance days. We find that such exceedances could not be mitigated by reducing emissions in Arizona; complete removal of state emissions would reduce the maximum daily 8-h average (MDA8) ozone in Yuma by only 0.7% on exceeding days. In contrast, emissions in Mexico are estimated to contribute to 11% of the ozone during these exceedances, and their reduction would reduce MDA8 ozone in Yuma to below the standard. Using satellite-based remote sensing measurements, we find that emissions of nitrogen oxides (NO, a key photochemical precursor of ozone) increase slightly in Mexico from 2005 to 2016, opposite to decreases shown in the bottom-up inventory. In comparison, a decrease of NO emissions in the US and meteorological factors lead to an overall of summer mean and annual MDA8 ozone in Yuma (by ∼1-4% and ∼3%, respectively). Analysis of meteorological back-trajectories also shows similar transboundary transport of ozone at the US-Mexico border in California and New Mexico, where strong influences from Northern Mexico coincide with 11 out of 17 and 6 out of 8 ozone exceedances. 2020 is the final year of the U.S.-Mexico Border 2020 Program, which aimed to reduce pollution at border regions of the US and Mexico. Our results indicate the importance of sustaining a substantial cooperative program to improve air quality at the border area.
高浓度的地面臭氧会影响人类健康、植物和动物。在本地排放量已然很低的农村地区减少臭氧污染颇具挑战。我们利用气象后向轨迹、空气质量模型敏感性分析以及卫星遥感数据，对亚利桑那州尤马市的臭氧来源展开调查，结果发现，在16个臭氧超标日中有12天受到来自墨西哥北部的强烈跨国影响。我们发现，通过减少亚利桑那州的排放无法缓解此类超标情况；即便完全消除该州的排放，在超标日里尤马市的每日最大8小时平均（MDA8）臭氧浓度也只会降低0.7%。相比之下，据估计在这些超标期间，墨西哥的排放对臭氧的贡献率为11%，减少其排放会使尤马市的MDA8臭氧浓度降至标准以下。利用基于卫星的遥感测量数据，我们发现，2005年至2016年期间墨西哥的氮氧化物（NO，臭氧的一种关键光化学前体）排放量略有增加，这与自下而上清单中显示的减少情况相反。相比之下，美国NO排放量的减少以及气象因素导致尤马市夏季平均和年度MDA8臭氧总体下降（分别下降约1 - 4%和3%）。对气象后向轨迹的分析还表明，在美国 - 墨西哥边境的加利福尼亚州和新墨西哥州也存在类似的臭氧跨境传输情况，在那里，来自墨西哥北部的强烈影响分别与17个臭氧超标日中的11天以及8个臭氧超标日中的6天相吻合。2020年是美墨边境2020计划的最后一年，该计划旨在减少美国和墨西哥边境地区的污染。我们的结果表明，持续开展一项实质性的合作计划对于改善边境地区空气质量至关重要。
