WATER-SOLUBLE FRACTIONS OF AEROSOL AND THEIR RELATIONS TO NUMBER SIZEDISTRIBUTIONS BASED ON AIRCRAFT MEASUREMENTS FROM THE NORTH-ATLANTIC REGIONAL EXPERIMENT

Aerosol chemical and physical measurements were made at altitudes from 0.27 to 3 km near the coast of southern Nova Scotia, Canada, during t he 1993 North Atlantic Regional Experiment. The volume distributions o f aerosol with diameters between 0.005 and 3 mu m were dominated by ac cumulation mode particles. The mass and volume ratios (R(m) and R(v)) of the sum of soluble organics (SumOrg) to non-sea-salt (nss) SO4= wer e relatively invariant for estimated total particle mass (TPM) in exce ss of 13 mu g m(-3) (high TPM) but increased sharply with decreasing T PM below 13 mu g m(-3) (low TPM). Overall, the relationships between T PM and R(m) and R(v) were found to be R(m) = -(0.17 +/- 0.44) + (3.5 /- 1.0)TPM-((0.69+/-0.39)) and R(v) = -(0.35 +/- 0.70) + (5.7 +/- 1.7) TPM-((0.68+/-0.39)). The high TPM aerosols originated in eastern North America and had average composition of 46% nssSO(4)(=), 8% NH4+, and 8% SumOrg. In contrast, low TPM aerosols were found to be of backgroun d continental or marine tropospheric origins and had average compositi on of 23% nssSO(4)(=), 9% NH4+, and 20% SumOrg. The aerosols in both T PM regimes were separated into two groups based on the mode of the vol ume distributions. The correlation between the mass of each species an d the particle volume distribution was investigated for these groups.