BLACK CARBON - ATMOSPHERIC CONCENTRATIONS AND CLOUD-WATER CONTENT MEASUREMENTS OVER SOUTHERN NOVA-SCOTIA

Atmospheric black carbon concentrations have been measured in air and cloud water samples collected over southern Nova Scotia, Canada, durin g the North Atlantic Regional Experiment. The average black carbon atm ospheric concentration found in continental air masses is 0.23 +/- 0.0 4 mu g/m(3) compared with 0.03 +/- 0.01 mu g/m(3) for maritime air. Th e concentrations found in the 1- to 3- km layer are higher than those below 1 km, suggesting that most of the black carbon is not of local o rigin. About 9% of black carbon was in the form of an internal mixture inside cloud droplets. The average black carbon content of cloud wate r was about 40 mu g/kg. The average black carbon to non-sea-salt SO4 m ass mixing ratio was found to be between 0.02 and 0.04.