Real-Time Measurement of Correlated Size and Composition Profiles of Individual Atmospheric Aerosol Particles

Abstract

In this paper, the unique real-time measurement capabilities of aerosol time-of-flight mass spectrometry (ATOFMS) for characterizing atmospheric aerosol particles are demonstrated. ATOFMS is used to obtain the aerodynamic size and chemical composition of individual aerosol particles sampled directly into the instrument from outdoors. Such measurements are made in-situ by combining a unique dual-laser aerodynamic particle sizing system to size and track individual particles through the instrument and laser desorption/ionization time-of-flight mass spectrometry to obtain correlated single particle composition data. At typical ambient concentrations, the size and chemical composition of 50−100 particles per minute can be measured (up to 600 per minute at high particle concentrations). Presented here for the first time are compositionally resolved particle size distributions of ambient aerosol particles, showing definitive size/composition correlations. A goal of these studies is to ultimately couple data obtained from the dynamic monitoring of individual particles in atmospheric systems with that obtained using conventional ambient aerosol sampling to assist in sorting out complex field data on atmospheric processes.

Evaluation of elemental carbon as a marker for diesel particulate matter

“…Schauer et al (1996) and Schauer and Cass (2000) employed molecular marker source apportionment models, which used unique particle-phase organic compounds to apportion the source contributions of nine primary sources to atmospheric fine particulate matter concentrations in the Los Angeles Basin and the San Joaquin Valley in California. Bhave et al (2001) demonstrated the feasibility of source apportionment of real-time single particle mass spectrometry measurements that were collected using an aerosol time-of-flight mass spectrometer (ATOFMS) (Prather et al, 1994;Noble and Prather, 1996). Although these source apportionment methods have been developed, they are relatively expensive and can only be conducted by a limited number of analytical laboratories.…”

Real‐time single particle monitoring of a relative increase in marine aerosol concentration during winter rainstorms

“…1997; Noble and Prather, 1996;Silva and Prather, 1997] which measures the size and composition of individual particles in polydisperse aerosol systems by coupling time-of-flight aerosol beam spectrometry (TOFABS) [Dahneke, 1978] with timeof-flight mass spectrometry (TOFMS). Although several realtime single particle mass spectrometry (RTSPMS) methods exist [for a review see Johnston and Wexler, 1995], ATOFMS is currently the only one which provides precise particle size and chemical composition for particles in polydisperse samples [Salt et al, 1996].…”

Towards direct measurement of turbulent vertical fluxes of compounds in atmospheric aerosol particles

“…As a direct quantification of compounds in aerosol particles is not possible from mass spectra obtained by LDI, we applied averaging and normalizing of peak areas to deduce relative concentrations of specific compounds such as nitrate. In single particle mass spectra, nitrate exhibits two characteristic peaks in the negative spectra at the mass/charge ratios (m/z) 46 (NO 2 À ) and 62 (NO 3 À ) [e.g., Noble and Prather, 1996;Murphy and Thomson, 1997;Trimborn et al, 2000]. For each individual particle, the peak areas at m/z = 46 and 62 are added up and then divided by the total peak area of the negative spectra yielding the normalized peak area, npa.…”