Variation of marine aerosol acidity with particle size

pHs were measured in minimally diluted extracts of size‐segregated aerosols sampled under moderately polluted conditions at Bermuda during spring 1997. Extrapolation to aerosol liquid water contents yielded ambient pHs for most super‐μm diameter size fractions in the upper 3s to upper 4s. Aerosols within this size range of each sample approached similar pH. These results are consistent with recent estimates of sea‐salt aerosol pHs based on thermodynamic considerations and model calculations. Most pHs for finer aerosol size fractions were in the 1s and 2s. The H+ + SO42− ↔ HSO4− equilibrium strongly buffered aerosol pH in all size fractions.