Air quality trends for the ports of Los Angeles and Long Beach spanning the covid19 crisis: Part 1. Oxidant pollutants

Abstract

Ports are major air pollution sources impacting downwind communities with emissions from port activities, nearby energy and other heavy industries, truck, train, and vessel traffic, and commuting traffic. The Ports of Los Angeles/Long Beach, denoted Ports, are the western hemisphere's largest, with plans for port electrification to reduce air pollution. The covid19 shutdown impacted the Ports, providing a real-world experiment on the effects of electrification on exposure to neighboring communities.Eight in situ surveys with a mobile air quality laboratory (14 trace gases, aerosols, and meteorology) were conducted spanning the covid19 shutdown to characterize the resultant air quality changes. These data were combed with time series (2015-) from six Port area air quality stations and TROPOMI satellite nitrogen dioxide NO2 column XNO2.In situ surveys showed dramatic NO2 decreases from Jul. 2019 to May 2020 (during the shutdown), with NO2 only returning towards pre-covid levels by Jul. 2022. Lesser covid19 NO2 decreases were observed by the air quality station data and satellite XNO2 for the Los Angeles Basin; both showed NO2 decrease during the shutdown and an extended time for recovery to more normal concentration (and underlying economic activity) - until 2022 - far longer than the shutdown. Overall, ozone, O3 increased, signifying that O3, formation is volatile organic hydrocarbons, VOH, limited, with the strongest O3 source(s) arriving from offshore. This finding suggests efforts to purely address air quality by electrification without addressing area VOH emissions could potentially lessen, perhaps significantly, the expected air quality and health improvements in downwind communities. The Ports’ area industrial sites were identified as driving these VOHs, as the inverse relationship between NO2 and O3 persisted during the shutdown when non-industrial VOH sources would have decreased.