Abstract
Abstract. We present a newly developed total carbon analyzer (TCA08) and a method for online speciation of carbonaceous aerosol with a high time resolution. The total carbon content is determined by flash heating of a sample collected on a quartz-fiber filter with a time base between 20 min and 24 h. The limit of detection is approximately 0.3 µg C, which corresponds to a concentration of 0.3 µg C m−3 at a sample flow rate of 16.7 L min−1 and a 1 h sampling time base. The concentration of particulate equivalent organic carbon (OC) is determined by subtracting black carbon concentration, concurrently measured optically by an Aethalometer®, from the total carbon concentration measured by the TCA08. The combination of the TCA08 and Aethalometer (AE33) is an easy-to-deploy and low-maintenance continuous measurement technique for the high-time-resolution determination of equivalent organic and elemental carbon (EC) in different particulate matter size fractions, which avoids pyrolytic correction and the need for high-purity compressed gases. The performance of this online method relative to the standardized off-line thermo-optical OC–EC method and respective instruments was evaluated during a winter field campaign at an urban background location in Ljubljana, Slovenia. The organic-matter-to-organic-carbon ratio obtained from the comparison with an aerosol chemical speciation monitor (ACSM) was OM/OC=1.8, in the expected range.
Highlights
Carbonaceous aerosols frequently account for a large and often dominant fraction of fine particulate matter (PM2.5) mass in polluted atmospheres
TCA08 and AE33, are compared to the reference set of instruments after their assembly as one of the tests during the final inspection procedure (in-house-defined requirements for successful intercomparison between new and reference set of instruments are (1) for TCA08, total carbon (TC) concentration range up to 75.000 ng m−3, slope between 0.95 and 1.05, R2 above 0.98 and (2) for AE33, equivalent black carbon (eBC) concentrations up to 25.000 ng m−3, slope between 0.95 and 1.05, R2 above 0.98; Table S1 in the Supplement)
When the TCA08 is combined with an AE33 Aethalometer, the TC–black carbon (BC) method yields equivalent organic carbon (eOC)–elemental carbon” (eEC) data with a much greater time resolution than that offered by the analysis of filter-based samples
Summary
Carbonaceous aerosols frequently account for a large and often dominant fraction of fine particulate matter (PM2.5) mass in polluted atmospheres. They are extremely diverse (Gelencsér, 2004; Karanasiou et al, 2015), and they directly impact air quality, visibility, cloud formation and properties, the planetary radiation balance, and public health (Pöschl, 2005). The carbonaceous fractions can be described as black carbon (BC) or elemental carbon (EC) and organic matter (OM). The amount of carbon that can be found in carbonaceous aerosols is called total carbon (TC), which is commonly categorized into fractions of organic carbon (OC) and elemental carbon (EC). OC can be directly emitted to the atmosphere in particulate form as primary organic matter by combustion and biogenic processes, or it can have a secondary origin from gas-to-particle conversion of (semi)volatile organic compounds in the atmosphere
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