Abstract
Abstract. Mass concentrations of sulphate, nitrate, ammonium, organic carbon (OC), elemental carbon (EC) were determined from real time single particle data in the size range 0.1–3.0 μm measured by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) at urban and rural sites in Canada. To quantify chemical species within individual particles measured by an ATOFMS, ion peak intensity of m/z −97 for sulphate, −62 for nitrate, +18 for ammonium, +43 for OC, and +36 for EC were scaled using the number and size distribution data by an Aerodynamic Particle Sizer (APS) and a Fast Mobility Particle Sizer (FMPS). Hourly quantified chemical species from ATOFMS single-particle analysis were compared with collocated fine particulate matter (aerodynamic diameter < 2.5 μm, PM2.5) chemical composition measurements by an Aerosol Mass Spectrometer (AMS) at a rural site, a Gas-Particle Ion Chromatograph (GPIC) at an urban site, and a Sunset Lab field OCEC analyzer at both sites. The highest correlation was found for nitrate, with correlation coefficients (Pearson r) of 0.89 (ATOFMS vs. GPIC) and 0.85 (ATOFMS vs. AMS). ATOFMS mass calibration factors, determined for the urban site, were used to calculate mass concentrations of the major PM2.5 chemical components at the rural site near the US border in southern Ontario. Mass reconstruction using the ATOFMS mass calibration factors agreed very well with the PM2.5 mass concentrations measured by a Tapered Element Oscillating Microbalance (TEOM, r = 0.86) at the urban site and a light scattering monitor (DustTrak, r = 0.87) at the rural site. In the urban area nitrate was the largest contributor to PM2.5 mass in the winter, while organics and sulphate contributed ~64 % of the summer PM2.5 in the rural area, suggesting a strong influence of regional/trans-boundary pollution. The mass concentrations of five major species in ten size-resolved particle-types and aerosol acidity of each particle-type were determined for the rural site. On a mass basis sulphate and OC rich particle-types (OC-S and OC-S-N) accounted for up to 59 % of the particles characterized and aerosols were weakly acidic in the rural area. This is the first study to estimate hourly quantitative data of sulphate, nitrate, ammonium, OC and EC in ambient particles from scaled ATOFMS single particle analysis; these were closely comparable with collocated high time resolution data of sulphate, nitrate and ammonium detected by AMS and GPIC.
Highlights
Numerous epidemiological studies have revealed significant associations between adverse cardiorespiratory health and exposure to atmospheric particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM2.5) (e.g. Dockery et al, 1993; Burnett et al, 1995; Schwartz et al, 1996; Janssen et al, 2003)
The scaling factor as a function of particle size was estimated during the Seasonal Particulate Observation in Regional Toronto (SPORT) campaign in downtown Toronto and the BAQS-Met study at a rural site (Fig. S1 in Supplement)
Mass concentrations of PM2.5 chemical components were determined from Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) data collected at urban and rural sites during the SPORT and BAQS-Met field campaigns
Summary
Numerous epidemiological studies have revealed significant associations between adverse cardiorespiratory health and exposure to atmospheric particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM2.5) (e.g. Dockery et al, 1993; Burnett et al, 1995; Schwartz et al, 1996; Janssen et al, 2003). Several studies have suggested procedures to scale ATOFMS measurements using collocated optical particle counters (Wenzel et al, 2003; Qin et al, 2006; Dall’Osto and Harrison, 2006; Ault et al, 2009). Size-resolved particle-types from single particle analysis data were scaled with number concentrations measurements from a collocated Scanning Mobility Particle Sizer (SMPS) (Reinard et al, 2007; Pratt and Prather, 2009). Qin et al (2006) and Dall’Osto et al (2006) corrected for transmission losses by scaling with an Aerodynamic Particle Sizer (APS) and the scaled values agreed well with total PM2.5 mass concentrations and 24-h sampled chemical species collected by a MOUDI. During PM episodic days, the RSMS was found to be offset by a constant value as compared to the continuous monitors
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