Real-time measurements of mineral dust concentration in coarse particulate matter (PM10-2.5) by employing a novel optical-based technique in Los Angeles

Ramin Tohidi; Vahid Jalali Farahani; Constantinos Sioutas

doi:10.1016/j.scitotenv.2022.156215

Real-time measurements of mineral dust concentration in coarse particulate matter (PM₁₀_-_2.5) by employing a novel optical-based technique in Los Angeles

Sci Total Environ. 2022 Sep 10;838(Pt 2):156215. doi: 10.1016/j.scitotenv.2022.156215. Epub 2022 May 25.

Authors

Ramin Tohidi¹, Vahid Jalali Farahani¹, Constantinos Sioutas²

Affiliations

¹ University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
² University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA. Electronic address: sioutas@usc.edu.

PMID: 35623535
DOI: 10.1016/j.scitotenv.2022.156215

Abstract

As a primary component of coarse particulate matter (PM), ambient mineral dust has been linked to adverse health effects. Los Angeles, the largest metropolitan urban area of the United States, is impacted by both windblown and localized sources of mineral dust, often internally mixed with black carbon. The estimation of mineral dust concentrations with a high time resolution becomes critical in improving our understanding of its sources and temporal trends. Using Aethalometers combined with a high-volume virtual impactor (VI) to enrich coarse (2.5 <dp < 10 μm) particles, the light absorption and mass concentration of mineral dust were estimated in real-time during summer, fall, and winter over 2020-2021. The concentration-enriched coarse PM was collected on Teflon filters, and its chemical composition in terms of trace elements and metals was chemically quantified. The high time-resolution measurements enabled us to calculate the absorption coefficient of enriched dust particles by subtracting the light absorption of the post-VI coarse PM from that of the PM_2.5 aerosol fraction to reduce the impact of stronger light absorbers in ambient PM. Mineral dust was more prevalent during the fall and winter campaigns (i.e., 19.3 and 11.4 μg/m³, respectively), lower concentrations were observed during the summer campaign (i.e., 8.50 μg/m³). The calculated absorption Ångström exponent (AAE) was 2.18, highlighting the presence of dust particles during the sampling period. The dust mass absorption coefficient was estimated to be 2.7 ± 1.6 Mm^-1 at 370 nm and 0.41 ± 0.16 Mm^-1 at 880 nm wavelengths, respectively. The validation of the proposed approach was investigated by comparing the evaluated mineral dust mass concentrations in this study with the reported coarse PM concentrations by the California Air Resources Board (CARB). The results reported by the optical-based approach with high temporal resolution can provide crucial information on identifying sources of mineral dust in urban areas.

Keywords: Aerosol optical properties; Aethalometer; Coarse particulate matter; Los Angeles; Mineral dust; Virtual impactor/concentrator.

MeSH terms

Air Pollutants* / analysis
Dust / analysis
Environmental Monitoring / methods
Los Angeles
Minerals
Particle Size
Particulate Matter* / analysis

Substances

Air Pollutants
Dust
Minerals
Particulate Matter