Submicron particle, radon, and soot carbon characteristics over the northeast Atlantic

Abstract

Atmospheric aerosol particles (0.05μm ≤ rdry ≤ 1.5μm), 222Rn, and soot carbon mass were measured on a cruise over the Northeast Atlantic (63°N, 8°W) during October and November 1989. An accumulation mode (AM) was present in all particle data and was characterized by a lognormal size distribution with parameters N cm−3 (total number concentration), rg μm (geometric mean radius) and σg (geometric standard deviation). For aerosol associated with the “cleanest” Northeast Atlantic maritime and Arctic air masses, the AM parameters were found to be 16 cm−3 ≤ N ≤ 48 cm−3, 1.32 ≤ σg ≤ 1.46, and 0.08 μm < rg < 0.09 μm, leading to AM masses of between 0.20 μg m−3 and 0.38 μg m−3. Clean background levels of soot carbon mass for maritime and Arctic air were estimated to be around 20 ng m−3 and were associated with particle size radii r ≤ 0.15 μm. Soot carbon mass showed an excellent correlation with AM number concentration (cc=0.93), demonstrating its usefulness as an air mass tracer and as an indicator of anthropogenic pollutant transport. By comparison, radon, which is often used for this purpose, exhibited a significantly poorer correlation (cc=0.60) for this region. Approximately 9% of the total AM mass was accounted for by soot carbon, regardless of air mass origin, suggesting that early winter marine aerosol in the remote North Atlantic is primarily of anthropogenic origin.