Quantification of aerosol chemical composition using continuous single particle measurements

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 <i>m/z</i> −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, PM<sub>2.5</sub>) 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 <i>r</i>) 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 PM<sub>2.5</sub> 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 PM<sub>2.5</sub> mass concentrations measured by a Tapered Element Oscillating Microbalance (TEOM, <i>r</i> = 0.86) at the urban site and a light scattering monitor (DustTrak, <i>r</i> = 0.87) at the rural site. In the urban area nitrate was the largest contributor to PM<sub>2.5</sub> mass in the winter, while organics and sulphate contributed ~64 % of the summer PM<sub>2.5</sub> 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

Comparison of three techniques for analysis of data from an Aerosol Time-of-Flight Mass Spectrometer

“…(Table S2). Moreover, the correlation between PMF factors and the corresponding species 499 concentrations may be even stronger if ATOFMS data are corrected for size-dependent transmission 500 losses (Jeong et al, 2011). 501 502…”

Insight into the in-cloud formation of oxalate based on in situ measurement by single particle mass spectrometry

“…Consistently, the average relative peak area (RPA) of oxalate in the cloud RES and cloud INT particles suppressed by a factor of ∼ 8 that in the cloud-free particles. Defined as fractional peak area of each m/z relative to the sum of peak areas in a mass spectrum, RPA could represent the relative amount of a specie on a particle (Jeong et al, 2011;Healy et al, 2013). At ground level, oxalate was found in ∼ 3 % of total particles in Shanghai (Yang et al, 2009) and the PRD region (Cheng et al, 2017), respectively.…”

Variation of secondary coatings associated with elemental carbon by single particle analysis

“…Despite of matrix effects on the laser desorption/ionization for SPAMS, advances have been made in quantifying individual chemical species, either through multivariate analysis or by applying peak intensities for specific ions (e.g., Healy et al, 2013;Jeong et al, 2011;Xing et al, 2011). Relative peak area (RPA), defined as the peak area of each m/z divided by the total dual ion mass spectral peak area, is related to the relative amount of a species on a particle.…”