Characterization and source apportionment of organic aerosol using offline aerosol mass spectrometry

K R Daellenbach,R Wolf,I El Haddad,A Křepelová,F Canonaco,S Szidat,J G Slowik,C Bozzetti,Y Sosedova,Y Zhang,L Poulain,P Zotter,R.-J Huang,U Baltensperger,A S H Prévôt,P Fermo,M Crippa

doi:10.5194/amt-9-23-2016

Abstract

Abstract. Field deployments of the Aerodyne Aerosol Mass Spectrometer (AMS) have significantly advanced real-time measurements and source apportionment of non-refractory particulate matter. However, the cost and complex maintenance requirements of the AMS make its deployment at sufficient sites to determine regional characteristics impractical. Furthermore, the negligible transmission efficiency of the AMS inlet for supermicron particles significantly limits the characterization of their chemical nature and contributing sources. In this study, we utilize the AMS to characterize the water-soluble organic fingerprint of ambient particles collected onto conventional quartz filters, which are routinely sampled at many air quality sites. The method was applied to 256 particulate matter (PM) filter samples (PM1, PM2.5, and PM10, i.e., PM with aerodynamic diameters smaller than 1, 2.5, and 10 µm, respectively), collected at 16 urban and rural sites during summer and winter. We show that the results obtained by the present technique compare well with those from co-located online measurements, e.g., AMS or Aerosol Chemical Speciation Monitor (ACSM). The bulk recoveries of organic aerosol (60–91 %) achieved using this technique, together with low detection limits (0.8 µg of organic aerosol on the analyzed filter fraction) allow its application to environmental samples. We will discuss the recovery variability of individual hydrocarbon ions, ions containing oxygen, and other ions. The performance of such data in source apportionment is assessed in comparison to ACSM data. Recoveries of organic components related to different sources as traffic, wood burning, and secondary organic aerosol are presented. This technique, while subjected to the limitations inherent to filter-based measurements (e.g., filter artifacts and limited time resolution) may be used to enhance the AMS capabilities in measuring size-fractionated, spatially resolved long-term data sets.

Highlights

Aerosols affect climate, air quality, ecosystems, and human health (Kelly et al, 2007; Griggs and Noguer, 2002)
For the Zurich yearly cycle campaign (2011–2012), we validated the Rbulk calculation approach adopted here to a more conventional approach for the determination of water-soluble organic carbon (WSOC) (Fig. 3c; water-soluble organic aerosol, WSOA = WSOC×(OM/organic carbon (OC))offline Aerosol Mass Spectrometer (AMS)). We show that both approaches give similar estimates, suggesting that offline AMS measurements are related to WSOA and that a great part of the organic mass is accessible by the analysis procedure followed here
We developed and evaluated an offline method using an HR-ToF-AMS for the characterization of the chemical fingerprints of aerosol collected on filters (Pall quartz filters for the current study)

Summary

Introduction

Air quality, ecosystems, and human health (Kelly et al, 2007; Griggs and Noguer, 2002). Daellenbach et al.: Characterization and source apportionment of OA using offline AMS Location Campaign period

Methods

Results

Conclusion