Measurements of the Vertical Distribution of Atmospheric Chloride Particles

An account is given of about 250 impactions made on ten flights to sample chloride particles. The particles are captured on small perspex slides coated with a gelatin-silver nitrate solution and become manifest as circular discs. The calibration of the method is described and the lower limit of detection is found to be about 10^-13 gm. NaCl.

The results show that, in the main, chloride particles originate from the sea surface but there is a possibility that the land or the coast produce some in the range 10^-11 to 10^-13 g. Particle concentrations are found up to about 2,000 litre^-1 and total chloride contents up to 230 μg m^-3. The variations of these particle concentrations with height, wind speed, state of sea and the three-day history of the sampled air are discussed.

Data are also presented on the concentrations of dust particles which were inadvertently sampled simultaneously with the chloride particles.