Approach for Measuring the Chemistry of Individual Particles in the Size Range Critical for Cloud Formation
Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093, United States. Analytical Chemistry
(Impact Factor: 5.64).
02/2011; 83(6):2271-8. DOI: 10.1021/ac103152g
Aerosol particles, especially those ranging from 50 to 200 nm, strongly impact climate by serving as nuclei upon which water condenses and cloud droplets form. However, the small number of analytical methods capable of measuring the composition of particles in this size range, particularly at the individual particle level, has limited our knowledge of cloud condensation nuclei (CCN) composition and hence our understanding of aerosols effect on climate. To obtain more insight into particles in this size range, we developed a method which couples a growth tube (GT) to an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS), a combination that allows in situ measurements of the composition of individual particles as small as 38 nm. The growth tube uses water to grow particles to larger sizes so they can be optically detected by the UF-ATOFMS, extending the size range to below 100 nm with no discernible changes in particle composition. To gain further insight into the temporal variability of aerosol chemistry and sources, the GT-UF-ATOFMS was used for online continuous measurements over a period of 3 days.
Available from: Roy M Harrison
- "Zauscher et al. (2011) developed a water-based growth tube system which uses condensation to grow particles which would be too small for optical detection. This enables the detection and analysis of particles down to 38 nm (Zauscher et al., 2011). The rapid single particle mass spectrometer (RSMS) has also been applied to single particle studies (Phares et al., 2003; Lake et al., 2003; Tolocka et al., 2004) with some success. "
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ABSTRACT: Knowledge of the human health impacts associated with airborne nanoparticle exposure has led to considerable research activity aimed at better characterising these particles and understanding which particle properties are most important in the context of effects on health. Knowledge of the sources, chemical composition, physical structure and ambient concentrations of nanoparticles has improved significantly as a result. Given the known toxicity of many metals and the contribution of nanoparticles to their oxidative potential, the metallic content of the nanoparticulate burden is likely to be an important factor to consider when attempting to assess the impact of nanoparticle exposure on health. This review therefore seeks to draw together the existing knowledge of metallic nanoparticles in the atmosphere and discuss future research priorities in the field. The article opens by outlining the reasons behind the current research interest in the field, and moves on to discuss sources of nanoparticles to the atmosphere. The next section reviews ambient concentrations, covering spatial and temporal variation, mass and number size distributions, air sampling and measurement techniques. Further sections discuss the chemical and physical composition of particles. The review concludes by summing up the current state of research in the area and considering where future research should be focused.
Available from: Julia Laskin
- "Characterisation of the chemical composition of particles smaller than 50 nm is hindered by difficulties in transmission of ultra-small particles through aerodynamic lenses and the limitations of the optical detection methods. To alleviate these problems, Zauscher et al.  coupled a growth tube to an ultrafine ATOFMS. Small particles (40–60 nm) grow to larger sizes in the growth tube in the presence of water vapour, which enables their detection using the standard optical detection scheme. "
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ABSTRACT: This manuscript presents an overview of the most recent instrument developments, field and laboratory applications of mass spectrometry (MS) in chemistry and physics of atmospheric aerosols. A broad range of MS instruments employing different sample introduction methods, ionization and mass detection techniques are utilized for both 'on-line' and 'off-line' characterization of aerosols. On-line MS techniques enable detection of individual particles with simultaneous measurements of particle size distributions and aerodynamic characteristics, and are ideally suited for field studies which require high temporal resolution. Off-line MS techniques provide means for detailed molecular-level analysis of aerosol samples which is essential to fundamental knowledge on aerosol chemistry, mechanisms of particle formation and atmospheric aging. Combined together, complementary MS techniques provide comprehensive information on the chemical composition, size, morphology and phase of aerosols - data of key importance for evaluating hygroscopic and optical properties of particles, their health effects, understanding their origins, and atmospheric evolution. Developments and applications of MS techniques in the aerosol research have expanded remarkably over a couple of last years as evidenced by sky-rocketing publication statistics. The goal of this review is to period of late 2010 - early 2012, which were not conveyed in previous reviews.
Available from: Alfred Wiedensohler
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ABSTRACT: An Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS) was deployed to
investigate the size-resolved chemical composition of single particles
at an urban background site in Paris, France, as part of the MEGAPOLI
winter campaign in January/February 2010. ATOFMS particle counts were
scaled to match coincident Twin Differential Mobility Particle Sizer
(TDMPS) data in order to generate hourly size-resolved mass
concentrations for the single particle classes observed. The total
scaled ATOFMS particle mass concentration in the size range 150-1067 nm
was found to agree very well with the sum of concurrent High-Resolution
Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and Multi-Angle
Absorption Photometer (MAAP) mass concentration measurements of organic
carbon (OC), inorganic ions and black carbon (BC) (R2 =
0.91). Clustering analysis of the ATOFMS single particle mass spectra
allowed the separation of elemental carbon (EC) particles into four
classes: (i) EC attributed to biomass burning (ECbiomass), (ii) EC
attributed to traffic (ECtraffic), (iii) EC internally mixed with OC and
ammonium sulfate (ECOCSOx), and (iv) EC internally mixed with
OC and ammonium nitrate (ECOCNOx). Average hourly mass
concentrations for EC-containing particles detected by the ATOFMS were
found to agree reasonably well with semi-continuous quantitative
thermal/optical EC and optical BC measurements (r2 = 0.61 and
0.65-0.68, respectively, n = 552). The EC particle mass assigned to
fossil fuel and biomass burning sources also agreed reasonably well with
BC mass fractions assigned to the same sources using seven-wavelength
aethalometer data (r2 = 0.60 and 0.48, respectively, n =
568). Agreement between the ATOFMS and other instrumentation improved
noticeably when a period influenced by significantly aged, internally
mixed EC particles was removed from the intercomparison. 88 % and 12 %
of EC particle mass was apportioned to fossil fuel and biomass burning
respectively using the ATOFMS data compared with 85 % and 15 %
respectively for BC estimated from the aethalometer model. On average,
the mass size distribution for EC particles is bimodal; the smaller mode
is attributed to locally emitted, mostly externally mixed EC particles,
while the larger mode is dominated by aged, internally mixed
ECOCNOx particles associated with continental transport
events. Periods of continental influence were identified using the
Lagrangian Particle Dispersion Model (LPDM) "FLEXPART". A consistent
minimum between the two EC mass size modes was observed at approximately
400 nm for the measurement period. EC particles below this size are
attributed to local emissions using chemical mixing state information
and contribute 79 % of the scaled ATOFMS EC particle mass, while
particles above this size are attributed to continental transport events
and contribute 21 % of the EC particle mass. These results clearly
demonstrate the potential benefit of monitoring size-resolved mass
concentrations for the separation of local and continental EC emissions.
Knowledge of the relative input of these emissions is essential for
assessing the effectiveness of local abatement strategies.
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