Aerosol Laser Ablation Mass Spectrometry of Suspended Powders from PM Sources and Its Implications to Receptor Modeling

Abstract

Primary sources of particulate matter (PM) were analyzed by suspending powdered samples into an aerosol laser ablation mass spectrometer (LAMS). PM sources studied included vehicle exhaust particulates, dust from a nonferrous smelter, cement powder, incinerator fly ash, two coal fly ash samples, and two soils. Marker peaks signified certain PM source sectors: construction particles could be distinguished by abundant Ca and Ca compounds, fuel combustion was marked by elemental carbon clusters, and nonferrous industrial particles showed inorganic As, Cu, Pb, Zn, and SO x . In addition to the distinction between particles from these different source sectors, mass spectral results also showed that for a single source, different particle types existed, and among different sources within a sector, similar spectra were present. The aerosol LAMS results show the difficulty in differentiating among separate fly ash sources as well as among different soil samples. A particle class balance receptor model that measures the amount of specific particle types rather than the amount of a chemical component is suggested as a means of source apportionment when particle spectra with overlapping source possibilities occur. The assumptions and limitations of receptor modeling aerosol LAMS data are also described. In particular, methods need to be developed to account for the contribution of secondary sources. INTRODUCTIONIn Ontario, Canada, ~1900 premature deaths, 9800 hospitalizations, and many more minor illnesses each year are attributed to air pollution.1 The Ontario Medical Association estimates that these burdens combine to cost, conservatively, more than $10 billion every year, both in direct (e.g., increased hospitalizations and employee absenteeism) and indirect (e.g., premature deaths and mental suffering) costs.1 A better characterization of air pollution, which includes a significant particulate matter (PM) component of acid aerosols, SO 4 2-particles, and PM from primary emission sources, would improve the understanding of its adverse health effects.2 Also, apportionment of the PM among its identified sources would help in determining targeted regulatory paths to remediate the PM component of air pollution problems.Single particle laser mass spectrometry is an advanced technique recently applied to the characterization of ambient PM.3 Aerosol laser ablation or laser desorption/ ionization mass spectrometers typically sample PM directly from the environment into the vacuum source region of a time-of-flight mass spectrometer. Individual particles are then ablated allowing particle-to-particle chemistries to be monitored online. In contrast to conventional bulk filter collection of PM that requires subsequent offline sample preparation and analysis, aerosol laser ablation mass spectrometry (LAMS) provides rapid, real-time information on separate particles. A recent literature review of the technique was conducted by Suess and Prather.

Characterization of Aerosols Containing Zn, Pb, and Cl from an Industrial Region of Mexico City

“…As shown in Supporting Information Table S2, the strongest associations within the industrial factor were, from weakest to strongest, between Cl, Na, Zn, Pb, Cr, and P. This was similar to the mixing state identified by the ATOFMS and CCSEM/EDX. Furthermore, many of these elements were key markers distinguishing incineration from smelting in the work of Tan et al (21). However, the PIXE factor analysis was unable to identify associations with nitrogen and carbon.…”

“…Municipal and hazardous waste incineration have been shown to emit Pb, Zn, and Cl particles (21,(28)(29)(30)(31). For this source, the Cl is primarily from the burning of plastics such as polyvinyl chloride and paper, whereas the Pb and Zn can be produced from a variety of waste materials.…”

Mixed Chloride Aerosols and their Atmospheric Implications: A Review

“…Online measurements of single particles by ATOFMS in an industrial/residential section of Mexico City by Moffet et al (2008a, b) demonstrated that the metal/Cl-containing particles accounted for a large fraction of the fine-mode particles, and the fraction reached 73% in the early morning hours. Other studies have also observed numerous micron-sized Zn/Pb/Cl-containing particles in lead smelter plumes (Ettler et al, 2005), in incinerator fly ash (Tan et al, 2002;Zhang et al, 2009), in mixed urban plumes (Lu et al, 2012), and in haze episodes (Li et al, 2009;Hu et al, 2015). The chloride particles from industrial smoke were often coated by organic matter after aging (see the schematic diagram in Fig.…”

Chemically-assigned classification of aerosol mass spectra

“…Smaller contributions from Ca, K/Organic, and NO/CH 4 N/Org were found in the positive ion, while H/C 2 /Organics, and Cl/Organics were identified in the negative. These smaller class contributions were expected as well, because work completed earlier on PM sources found that particle types from a standard PM source were chemically diverse [38]. The outlier classes were also small with Ͻ3.9% of the spectra in these classes.…”

“…These results showed that the same ADAMS scheme trained and applied to ambient could provide a consistent classification for a PM source. This consistency is important because it has been noted that a classification method for both source and ambient is a necessity for apportioning ambient aerosol LAMS data back to its original source(s) (receptor modeling) [38].…”