Evaluation of Ambient Sulfate in Southern California Using Spatially and Temporally Comprehensive Surface Monitoring Network Data
Abstract
Sources and formation mechanisms of atmospheric sulfates (SO42-) in the fine particulate matter (PM2.5) fraction have been investigated since the early 1970s. Over the past several decades, the California Air Resources Board (CARB) and the local districts have regulated fossil fuel production and combustion sources, which led to statewide emission reduction of sulfur oxides (SOx) by 62% between 2002 and 2018.
In 2018, ambient SO42- accounted for approximately 5 to 20% of the monthly average PM2.5 mass at select monitoring sites in the South Coast Air Basin (SoCAB), which was significantly lower than the 10 to 35% observed in 2002. Although the Arctic Research of the Composition of the Troposphere from Aircraft and Satellite (ARCTAS) campaign in 2008 identified local emissions as the primary driver of ambient SOx over southern California, a more recent modeling study suggested that majority of the ground-level SO42- are driven by transport and meteorology. Uncertainties around the origin of SOx are reflected in various regional air quality models that typically under predict ambient SO42-, especially in southern California. SOx emissions are expected to scale with population and economic growth, and are predicted to overcome the effects of regulations after 2015. It is imperative that the origin of SO42- are reexamined using ambient measurements to ensure that California is on the most optimal path to controlling and mitigating PM2.5. This study presents a year-long (April 2012 to March 2013) dataset collected at spatially comprehensive monitoring network sites that employed high-frequency analyzers for SO42-, sulfur dioxide, carbon monoxide, oxides of nitrogen (NOx), ozone, PM2.5, and various meteorological parameters. The evaluation of hourly atmospheric sulfur conversion ratios and multi-pollutant regression analysis provide insight into the origin and the seasonality of SOx in southern California. This study is the first to conduct a long-term hourly SO42- measurement campaign beyond California's coastline in tandem with high-frequency SO42- measurements at multiple inland monitoring sites.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A11S2809K
- Keywords:
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- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3323 Large eddy simulation;
- ATMOSPHERIC PROCESSES