Analysis of long‐term observations of NO_x and CO in megacities and application to constraining emissions inventories

Abstract

Long‐term atmospheric NOx/CO enhancement ratios in megacities provide evaluations of emission inventories. A fuel‐based emission inventory approach that diverges from conventional bottom‐up inventory methods explains 1970–2015 trends in NOx/CO enhancement ratios in Los Angeles. Combining this comparison with similar measurements in other U.S. cities demonstrates that motor vehicle emissions controls were largely responsible for U.S. urban NOx/CO trends in the past half century. Differing NOx/CO enhancement ratio trends in U.S. and European cities over the past 25 years highlights alternative strategies for mitigating transportation emissions, reflecting Europe's increased use of light‐duty diesel vehicles and correspondingly slower decreases in NOx emissions compared to the U.S. A global inventory widely used by global chemistry models fails to capture these long‐term trends and regional differences in U.S. and Europe megacity NOx/CO enhancement ratios, possibly contributing to these models' inability to accurately reproduce observed long‐term changes in tropospheric ozone.

Power plant fuel switching and air quality in a tropical, forested environment

“…Conversely, substitution by natural gas greatly improves the outlook for regional air quality and human health. In this context, even though anthropogenic emissions in the Amazon region are low compared to other regions of the world -such as Mexico City (Molina et al, 2010), São Paulo (Silva Junior and , and Los Angeles (Hassler et al, 2016) -the study results of Fig. 4 demonstrate the significant sensitivity of Amazonia to anthropogenic emissions.…”

Long-path measurements of pollutants and micrometeorology over Highway 401 in Toronto

“…Our [NO x ] / [CO] ratios during both weekdays and weekends are greater than their results (0.11 and 0.033), but our study only focused on near-surface observations over a short defined section of Highway 401 while their observations were at 1 km above the ground level with a bigger footprint which included off-road emissions and other local sources. Hassler et al (2016) [NO x ] in this study are 3.14 and 7.75 for weekdays and weekends, respectively. Therefore our results on NO x and CO are comparable with these previous studies.…”

Characterizing Regional-Scale Combustion Using Satellite Retrievals of CO, NO2 and CO2

“…However, most of these are focused on either field campaigns for specific megacities (e.g., Los Angeles or Paris [14]), specific regions (e.g., Europe by [20]), or specific ratios between two compounds (e.g., ∆CO/∆CO 2 , [17] or ∆NO x /∆CO 2 , [7]). For satellite analyses in particular, several multi-species studies have been designed to estimate emissions of air pollutants or surface fluxes of greenhouse gases; yet very few studies have focused on analyzing both from complementary datasets.…”

“…Important work has been carried out in recent years toward understanding emissions through analysis of enhancements of chemical species (including isotopes) based on ground [10][11][12][13][14], aircraft [15,16], and satellite observations ( [7,[17][18][19][20]). However, most of these are focused on either field campaigns for specific megacities (e.g., Los Angeles or Paris [14]), specific regions (e.g., Europe by [20]), or specific ratios between two compounds (e.g., ∆CO/∆CO 2 , [17] or ∆NO x /∆CO 2 , [7]).…”