Abstract
Abstract. Carbonaceous aerosol is a major contributor to the total aerosol load and being monitored by diverse measurement approaches. Here, 10 years (2005–2015) of continuous carbonaceous aerosol measurements collected at the Centre of Atmospheric Research Experiments (CARE) in Egbert, Ontario, Canada, on quartz-fiber filters by three independent networks (Interagency Monitoring of Protected Visual Environments, IMPROVE; Canadian Air and Precipitation Monitoring Network, CAPMoN; and Canadian Aerosol Baseline Measurement, CABM) were compared. Specifically, the study evaluated how differences in sample collection and analysis affected the concentrations of total carbon (TC), organic carbon (OC), and elemental carbon (EC). Results show that different carbonaceous fractions measured by various networks were consistent and comparable in general among the three networks over the 10-year period, even with different sampling systems/frequencies, analytical protocols, and artifact corrections. The CAPMoN TC, OC, and EC obtained from the DRI model 2001 thermal–optical carbon analyzer following the IMPROVE-TOR protocol (denoted as DRI-TOR) method were lower than those determined from the IMPROVE_A TOR method by 17 %, 14 %, and 18 %, respectively. When using transmittance for charring correction, the corresponding carbonaceous fractions obtained from the Sunset-TOT were lower by as much as 30 %, 15 %, and 75 %, respectively. In comparison, the CABM TC, OC, and EC obtained from a thermal method, EnCan-Total-900 (ECT9), were higher than the corresponding fractions from IMPROVE_A TOR by 20 %–30 %, 0 %–15 %, and 60 %–80 %, respectively. Ambient OC and EC concentrations were found to increase when ambient temperature exceeded 10 ∘C. These increased ambient concentrations of OC during summer were possibly attributed to secondary organic aerosol (SOA) formation and forest fire emissions, while elevated EC concentrations were potentially influenced by forest fire emissions and increased vehicle emissions. Results also show that the pyrolyzed organic carbon (POC) obtained from the ECT9 protocol could provide additional information on SOA although more research is still needed.
Highlights
Carbonaceous aerosols, including elemental carbon (EC), which is often referred to as black carbon (BC) and organic carbon (OC), make up a large fraction of the atmospheric fine particulate matter (PM) mass (Heintzenberg, 1989)
For the Canadian Aerosol Baseline Measurement (CABM) samples, the pyrolyzed organic carbon (POC) determined at 870 ◦C by ECT9 represents different OC properties and does not equal the charred OC obtained by Sunset-thermal–optical transmittance (TOT), DRITOR, or IMPROVE_A thermal–optical reflectance (TOR)
The National Institute of Standards and Technology (NIST) Urban Dust Standard Reference Material (SRM) 8785 air particulate matter on filter media is intended primarily for use to evaluate analytical methods used to characterize the carbon composition of atmospheric fine PM (Cavanagh and Watters, 2005; Klouda et al, 2005). These samples were produced by resuspension of the original SRM 1649a urban dust sample, followed by collection of the fine fraction (PM2.5)
Summary
Carbonaceous aerosols, including elemental carbon (EC), which is often referred to as black carbon (BC) and organic carbon (OC), make up a large fraction of the atmospheric fine particulate matter (PM) mass (Heintzenberg, 1989). 2005–2015 Sunset ECT9 Retention time Cyclone 2.5 16.7 2500QAT-UP 47 13.85 20.09 Integrated weekly 24 048 168.3 No Yes – 476 117 ing high filter face velocities for longer sample durations may result in evaporation of semi-volatile compounds as negative artifacts (Khalek, 2008; Sutter et al, 2010; Yang et al, 2011). The objective of this study is to conduct an inter-comparison study for evaluating the comparability and consistency of 10-year co-located carbonaceous aerosol measurements at Egbert made by three North American networks (Interagency Monitoring of Protected Visual Environments, Canadian Air and Precipitation Monitoring Network, and Canadian Aerosol Baseline Measurement), all of which use different sampling instruments, frequencies, durations, analytical methods, and artifact corrections This inter-comparison study is expected to provide some suggestions/recommendations for improving the compatibility and consistency of long-term measurements
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