Ronald J. Ferek

LONG-RANGE TRANSPORT OF SOOT CARBON IN THE MARINE ATMOSPHERE

Atmospheric aerosols were collected during several oceanographic cruises in the Atlantic and Pacific Oceans as well as in the continental source regions of soot carbon aerosols. The samples were analyzed for soot carbon by a reflection technique, for light elements by proton elastic scattering (PESA), and for elements heavier than Na by proton induced X-ray emission (PIXE). Significant amounts of soot carbon were observed consistently over the remote tropical Atlantic and occasionally over the remote Pacific. On the basis of the concentrations of other aerosol components, in particular excess fine potassium (the amount of submicron K not related to the seasalt and soil components), we are able to suggest that a substantial fraction of the soot carbon over the remote tropical oceans originates from biomass burning in the tropics.

Photochemical production of carbonyl sulfide in seawater and its emission to the atmosphere

Carbonyl sulfide (COS) measurements in the surface waters of the temperate and subtropical North Atlantic and the Gulf of Mexico showed COS to be supersaturated with respect to atmospheric equilibrium at almost all locations and times investigated. Its concentration follows a pronounced diel cycle which can be modeled using a simple equation which includes hydrolysis removal and photo-chemical production. The concentration and ocean/atmosphere flux of COS depends strongly on marine productivity, the highest levels being found in coastal and shelf waters. Analysis of presently available data yields an estimate of 13 Gmol yr-1 (0.41 Tg S(COS) yr−1) for the total flux of COS from the oceans to the atmosphere.

Electron microscopy of acidic aerosols collected over the northeastern United States

Abstract As part of the acid precipitation experiment (APEX) conducted in the northeastern U.S. by the National Center for Atmospheric Research and cooperating universities, aerosols were collected from an aircraft in different seasons, locations and meteorological conditions. Particles were impacted on electron microscope grids for morphological analysis and thin-film chemical tests for sulfate and nitrate. Under most conditions the accumulation mode aerosols ( c . 0.1–1.0 μm diameter) collected in the boundary layer were composed of sulfate particles of uniform composition (i.e. an internally mixed aerosol), indicating that individual particle composition could be inferred from bulk measurements. Externally mixed aerosols (i.e. assemblages of different kinds of particles) were found to exist near certain sources (e.g. power plants), in urban plumes, and near fair weather cumulus clouds. Direct evidence of rapid oxidation of SO 2 to H 2 SO 4 in cloud droplets was obtained in samples collected near clouds in northern New York and central Illinois, and this represents a potentially major pathway for SO 2 oxidation in the lower troposphere.

PIXE analysis of cascade impactor samples collected over the Pacific

Abstract Aerosol samples were collected on a cruise of the R/V Conrad in the Pacific Ocean. The cruise track was divided into two legs, the first one on the Peru/Ecuador shelf, the second through the equatorial and tropical Pacific to Hawaii. Sampling took place by means of two 1 l/min, ten-stage Battelle-type cascade impactors positioned on the foremast of the ship at about 20 m above the sea surface. Strict precautions were taken to avoid contamination of the samples by the ship itself. The impactor slides and back-up filters were analyzed for 25 elements by PIXE using a 2.4 MeV proton beam, produced by a compact cyclotron. In the samples, collected on leg 1, a significant anthropogenic component could be detected. Excess fine sulfur, excess fine potassium, and V, Ni, Cu and Zn in

Elemental composition of aerosols collected with airborne cascade impactors

Aerosols were collected from an aircraft using a wing-mounted cascade impactor sampler fitted with isokinetic inlets. Particle size distributions of elemental concentrations in four different size ranges were determined by particle-induced X-ray emission (PIXE), and for 1-h samples the results for Si, S, Cl, K, Ca, and Fe are reported. In two sampling periods (fall 1979 and summer 1980) aerosol concentrations and size distributions over the northeastern U.S. showed distinct differences. Sulfate concentrations, higher in summer than in the fall, averaged x ± s = 16.7 ± 9.9 and 6.6 ± 3.0 μgm−3, respectively, while Cl concentrations were much lower in summer than in the fall with median concentrations equal to 90 and 600 ng m−3, respectively, a Cl deficit in the more acidic summertime aerosols. The average size distributions of aerosol sulfur showed a distinct difference between the two seasons. Estimates of the mass median diameters of sulfate particles, corrected for humidification growth, resulted in dry diameters of 0.22 μm in the fall and 0.28 μm in the summer, the latter corresponding to a two-fold greater sulfate mass per particle. This result may reflect an enhancement of sulfate in aerosol droplets by liquid-phase oxidation of SO2 which may be more rapid under atmospheric conditions in the summer than the fall.