The physicochemical properties of coarse-mode, iron-containing particles and their temporal and spatial distributions are poorly understood. Single-particle analysis combining X-ray elemental mapping and computer-controlled scanning electron microscopy (CCSEM-EDX) of passively collected particles was used to investigate the physicochemical properties of iron-containing particles in Cleveland, OH, in summer 2008 (Aug-Sept), summer 2009 (July-Aug), and winter 2010 (Feb-March). The most abundant classes of iron-containing particles were iron oxide fly ash, mineral dust, NaCl-containing agglomerates (likely from road salt), and Ca-S containing agglomerates (likely from slag, a byproduct of steel production, or gypsum in road salt). The mass concentrations of anthropogenic fly ash particles were highest in the Flats region (downtown) and decreased with distance away from this region. The concentrations of fly ash in the Flats region were consistent with interannual changes in steel production. These particles were observed to be highly spherical in the Flats region, but less so after transport away from downtown. This change in morphology may be attributed to atmospheric processing. Overall, this work demonstrates that the method of passive collection with single-particle analysis by electron microscopy is a powerful tool to study spatial and temporal gradients in components of coarse particles. These gradients may correlate with human health effects associated with exposure to coarse-mode particulate matter.

No abstract

No abstract

We report on the precision and accuracy of measuring PM10-2.5 and its components with particles collected by passive aerosol samplers and analyzed by computer-controlled scanning electron microscopy with energy dispersive X-ray spectroscopy. Passive samplers were deployed for week-long intervals in triplicate and colocated with a federal reference method sampler at three sites and for 5 weeks in summer 2009 and 5 weeks in winter 2010 in Cleveland, OH. The limit of detection of the passive method for PM10-2.5 determined from blank analysis was 2.8 μg m(-3). Overall precision expressed as root-mean-square coefficient of variation (CVRMS) improved with increasing concentrations (37% for all samples, n = 30; 19% for PM10-2.5 > 10 μg m(-3), n = 9; and 10% for PM10-2.5 > 15 μg m(-3), n = 4). The linear regression of PM10-2.5 measured passively on that measured with the reference sampler exhibited an intercept not statistically different than zero (p = 0.46) and a slope not statistically different from unity (p = 0.92). Triplicates with high CVs (CV > 40%, n = 5) were attributed to low particle counts (and mass concentrations), spurious counts attributed to salt particles, and Al-rich particles. This work provides important quantitative observations that can help guide future development and use of passive samplers for measuring atmospheric particulate matter.

No abstract