Development and performance evaluation of online monitors for near real-time measurement of total and water-soluble organic carbon in fine and coarse ambient PM

Yashar Aghaei; Mohammad Aldekheel; Ramin Tohidi; Mohammad Mahdi Badami; Vahid Jalali Farahani; Constantinos Sioutas

doi:10.1016/j.atmosenv.2023.120316

Development and performance evaluation of online monitors for near real-time measurement of total and water-soluble organic carbon in fine and coarse ambient PM

Atmos Environ (1994). 2024 Feb 15:319:120316. doi: 10.1016/j.atmosenv.2023.120316. Epub 2023 Dec 23.

Authors

Yashar Aghaei¹, Mohammad Aldekheel^{1

2}, Ramin Tohidi¹, Mohammad Mahdi Badami¹, Vahid Jalali Farahani¹, Constantinos Sioutas¹

Affiliations

¹ University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, California, USA.
² Kuwait University, Department of Civil Engineering, P.O Box 5969, Safat 13060, Kuwait.

PMID: 38250566
PMCID: PMC10795521 (available on 2025-02-15)
DOI: 10.1016/j.atmosenv.2023.120316

Abstract

In this study, we developed two online monitors for total organic carbon (TOC) and water-soluble organic carbon (WSOC) measurements in fine (d_p < 2.5μm) and coarse (2.5μm < d_p < 10μm) particulate matter (PM), respectively. Their performance has been evaluated in laboratory and field tests to demonstrate the feasibility of using these monitors to measure near real-time concentrations, with consideration of their potential for being employed in long-term measurements. The fine PM collection setup was equipped with a versatile aerosol concentration enrichment system (VACES) connected to an aerosol-into-liquid-sampler (AILS), whereas two virtual impactors (VIs) in tandem with a modified BioSampler were used to collect coarse PM. These particle collection setups were in tandem with a Sievers M9 TOC analyzer to read TOC and WSOC concentrations in aqueous samples hourly. The average hourly TOC concentration measured by our developed monitors in fine and coarse PM were 5.17 ± 2.41 and 0.92 ± 0.29 μg/m³, respectively. In addition, our TOC readings showed good agreement and were comparable with those quantified using Sunset Lab EC/OC analyzer operating in parallel as a reference. Furthermore, we conducted field tests to produce diurnal profiles of fine PM-bound WSOC, which can show the effects of ambient temperature on maximum values in the nighttime chemistry of the winter, as well as on increased photochemical activities in afternoon peaks during the summer. According to our experimental campaign, WSOC mean values during the study period (3.07 μg/m³ for the winter and 2.7 μg/m³ for the summer) were in a comparable range with those of earlier studies in Los Angeles. Overall, our results corroborate the performance of our developed monitors in near real-time measurements of TOC and WSOC, which can be employed for future source apportionment studies in Los Angeles and other areas, aiding in understanding the health impacts of different pollution sources.

Keywords: Aqueous phase reactions; Los Angeles; Nighttime chemistry; Photochemical reactions; Total organic carbon; Water-soluble organic carbon.

Abstract

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