Analyses of Volatile Organic Compound Trends and Source Contributions Measured in the Los Angeles Basin during the COVID-19 Shelter-in-Place Orders
Abstract
The reported decreases in pollutant concentrations around the world, associated with COVID-19 shelter-in-place orders, led to expectations of similar trends in the US. The leading hypothesis has been that a decrease in on-road mobile source activity should lead to a decrease in nitrogen oxide (NOx) and subsequently ozone (O3) levels in NOx-limited regimes. Fine particulate matter (PM2.5)levels should also decrease due to a reduction in direct emissions and anthropogenic volatile organic compounds (VOCs) which serve as precursors to secondary PM2.5. However, recent evidence suggests that the role of transportation emissions in the formation of secondary pollutants (O3 and secondary PM2.5) has significantly decreased, including in the Los Angeles (LA) Basin, and other sources of anthropogenic VOCs are increasingly important. Since mid-April we have been measuring trace gases, including speciated VOCs, and particle mass and composition in the LA Basin, specifically on the Caltech campus (Pasadena, CA). Here we will focus on speciated VOC analyses using one- and two-dimensional gas chromatography with various detectors. We will present results of our efforts to: 1) identify and quantify the ambient gas-phase organic compounds across a gradient of human activity during and after the COVID-19 shelter-in-place orders; 2) identify VOC sources and source markers; 3) evaluate the contribution of specific source sectors to measured VOCs; and 4) compare the current VOC measurements and source contributions with previously published analyses. The data collected during this unprecedented time of dramatically reduced human activity will be of great utility in testing current understanding and hypotheses regarding urban O3 and secondary PM2.5 production under current and future conditions (as represented by negligible passenger vehicle emissions), as well as to answer some outstanding questions on the relative importance of emerging anthropogenic sources for secondary pollutant formation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA034.0002V
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3355 Regional modeling;
- ATMOSPHERIC PROCESSES