Search for: All records

Abstract Ambient ozone (O₃) concentrations in Southeast Michigan (SEMI) can exceed the U.S. National Ambient Air Quality Standard. Despite past efforts to measure O₃precursors and elucidate reaction mechanisms, changing emission patterns and atmospheric composition in SEMI warrant new measurements and updated mechanisms to understand the causes of observed O₃exceedances. In this study, we examine the chemical drivers of O₃exceedances in SEMI, based on the Phase I MOOSE (Michigan‐Ontario Ozone Source Experiment) field study performed during May to June 2021. A zero‐dimensional (0‐D) box model is constrained with measurement data of meteorology and trace gas concentrations. Box model sensitivity simulations suggest that the formaldehyde to nitrogen dioxide ratio (HCHO/NO₂) for the transition between the volatile organic compounds (VOCs)‐ and nitrogen oxides (NO_x)‐limited O₃production regimes is 3.0 ± 0.3 in SEMI. The midday (12:00–16:00) averaged HCHO/NO₂ratio during the MOOSE Phase I study is 1.62 ± 1.03, suggesting that O₃production in SEMI is limited by VOC emissions. This finding implies that imposing stricter regulations on VOC emissions should be prioritized for the SEMI O₃nonattainment area. This study, through its use of ground‐based HCHO/NO₂ratios and box modeling to assess O₃‐VOC‐NO_xsensitivities, has significant implications for air quality policy and the design of effective O₃pollution control strategies, especially in O₃nonattainment areas. 

Abstract Global economic development and urbanization during the past two decades have driven the increases in demand of personal and commercial vehicle fleets, especially in developing countries, which has likely resulted in changes in year-to-year vehicle tailpipe emissions associated with aerosols and trace gases. However, long-term trends of impacts of global gasoline and diesel emissions on air quality and human health are not clear. In this study, we employ the Community Earth System Model in conjunction with the newly developed Community Emissions Data System as anthropogenic emission inventory to quantify the long-term trends of impacts of global gasoline and diesel emissions on ambient air quality and human health for the period of 2000–2015. Global gasoline and diesel emissions contributed to regional increases in annual mean surface PM_2.5(particulate matter with aerodynamic diameters ⩽2.5μm) concentrations by up to 17.5 and 13.7µg m⁻³, and surface ozone (O₃) concentrations by up to 7.1 and 7.2 ppbv, respectively, for 2000–2015. However, we also found substantial declines of surface PM_2.5and O₃concentrations over Europe, the US, Canada, and China for the same period, which suggested the co-benefits of air quality and human health from improving gasoline and diesel fuel quality and tightening vehicle emissions standards. Globally, we estimate the mean annual total PM_2.5- and O₃-induced premature deaths are 139 700–170 700 for gasoline and 205 200–309 300 for diesel, with the corresponding years of life lost of 2.74–3.47 and 4.56–6.52 million years, respectively. Diesel and gasoline emissions create health-effect disparities between the developed and developing countries, which are likely to aggravate afterwards.