PM2.5 composition and sources in the San Joaquin Valley of California: A long-term study using ToF-ACSM with the capture vaporizer

Peng Sun; Ryan N Farley; Lijuan Li; Deepchandra Srivastava; Christopher R Niedek; Jianjun Li; Ningxin Wang; Christopher D Cappa; Sally E Pusede; Zhenhong Yu; Philip Croteau; Qi Zhang

doi:10.1016/j.envpol.2021.118254

PM_2.5 composition and sources in the San Joaquin Valley of California: A long-term study using ToF-ACSM with the capture vaporizer

Environ Pollut. 2022 Jan 1;292(Pt A):118254. doi: 10.1016/j.envpol.2021.118254. Epub 2021 Oct 2.

Authors

Affiliations

¹ Department of Environmental Toxicology, University of California, 1 Shields Ave., Davis, CA, 95616, USA; Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, 210023, China.
² Department of Environmental Toxicology, University of California, 1 Shields Ave., Davis, CA, 95616, USA.
³ Department of Environmental Toxicology, University of California, 1 Shields Ave., Davis, CA, 95616, USA; Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China.
⁴ Department of Civil and Environmental Engineering, University of California, 1 Shields Ave., Davis, CA, 95616, USA.
⁵ Department of Environmental Sciences, University of Virginia, Charlottesville, VA, 22904, USA.
⁶ Aerodyne Research Inc., Billerica, MA, 01821, USA.
⁷ Department of Environmental Toxicology, University of California, 1 Shields Ave., Davis, CA, 95616, USA. Electronic address: dkwzhang@ucdavis.edu.

PMID: 34610412
DOI: 10.1016/j.envpol.2021.118254

Abstract

The San Joaquin Valley (SJV) of California has suffered persistent particulate matter (PM) pollution despite many years of control efforts. To further understand the chemical drivers of this problem and to support the development of State Implementation Plan for PM, a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) outfitted with a PM_2.5 lens and a capture vaporizer has been deployed at the Fresno-Garland air monitoring site of the California Air Resource Board (CARB) since Oct. 2018. The instrument measured non-refractory species in PM_2.5 continuously at 10-min resolution. In this study, the data acquired from Oct. 2018 to May 2019 were analyzed to investigate the chemical characteristics, sources and atmospheric processes of PM_2.5 in the SJV. Comparisons of the ToF-ACSM measurement with various co-located aerosol instruments show good agreements. The inter-comparisons indicated that PM_2.5 in Fresno was dominated by submicron particles during the winter whereas refractory species accounted for a major fraction of PM_2.5 mass during the autumn associated with elevated PM₁₀ loadings. A rolling window positive matrix factorization analysis was applied to the organic aerosol (OA) mass spectra using the Multilinear Engine (ME-2) algorithm. Three distinct OA sources were identified, including vehicle emissions, local and regional biomass burning, and formation of oxygenated species. There were significant seasonal variations in PM_2.5 composition and sources. During the winter, residential wood burning and oxidation of nitrogen oxides were major contributors to the occurrence of haze episodes with PM_2.5 dominated by biomass burning OA and nitrate. In autumn, agricultural activities and wildfires were found to be the main cause of PM pollution. PM_2.5 concentrations decreased significantly after spring and were dominated by oxygenated OA during March to May. Our results highlight the importance of using seasonally dependent control strategies to mitigate PM pollution in the SJV.

Keywords: Aerosol chemical speciation monitor (ACSM); Biomass burning emissions; Residential wood burning; Secondary inorganic and organic aerosols; Urban PM pollution; Wildfires.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Environmental Monitoring
Nebulizers and Vaporizers
Particulate Matter* / analysis

Substances

Aerosols
Air Pollutants
Particulate Matter