In-situ measurements of the aerosol size distributions, physicochemistry and light absorption properties of Arctic haze

Abstract

Thermal and optical techniques were used at Barrow, Alaska during AGASP II (3/20/86–4/7/86) to measure in-situ variability of major aerosol components present in Arctic Haze. The experiment provided continuous data on the concentration, size distribution and relative proportions of sulfate species and refractory aerosol for particle diameters of 0.15 to 5 μm. Filter samples were also taken for determination of aerosol optical absorption due to soot (EC-elemental carbon). Although pronounced haze “events” were absence during this period the haze aerosol present varied in concentration between 2 and 6 μg/m³ but showed little change in relative constituents. Apart from local influences, the optical data indicated a persistent fine-mode sulfate aerosol with a NH₄ ⁺/SO₄ ⁻ molar ratio of about 0.4 and a refractory component of somewhat less than 10% by mass. A preliminary comparison of soot estimates determined from the light absorption data with the size distributions of refractory aerosol observed independently by the optical particle counter showed good agreement during the sample period. In the absence of local pollution, values of single scatter albedo derived from light scattering and light absorption showed similar variation about the average value of 0.86 found by us during flights north of Barrow three years earlier during AGASP I.