Particulate sulfur and chlorine in Arctic aerosols, spring 1983

Abstract

In each of 10 flights of the AGASP Arctic program, particulate sulfur and chlorine were determined by PIXE analysis of eight cascade impactor fractions from <0.25 to > 16 μm aerodynamic diameter (μmad). S occurred mainly in fine aerosol sizes of <2 μmad whereas Cl was mainly in coarser sizes. Two fine S modes could be identified, one being ultrafine (‘nuclei mode’) <0.25 fimad and the other being fine (‘accumulation mode’) centered around the 0.5–1.0 μmad range, with relative abundances of the two modes apparently depending on flight location. This suggests that both homogeneous gas phase and heterogeneous liquid phase reactions led to sulfuric acid formation in the haze. Qualitative comparisons of aerosol S and Cl distributions with particle size suggest that aerosol Cl concentrations are controlled by a sea surface source, particle coagulation and surface deposition, and volatility after reaction with acidic trace gases. Stratospheric aerosols sampled at 500 mb within a tropopause fold structure contained S concentrations greater than those in the Arctic haze and contained an appreciable Cl component.