An Instrument for Measuring the Liquid Water Content of Aerosols

An instrument for measuring the liquid water content of aerosols is described. Aerosol samples are collected on PTFE membrane filters and then are placed in a closed chamber in which the relative humidity can be controlled over a range from 5 to 95%. A β-gauge measures the changing aerosol mass from a low humidity through a range of increasing humidities and then through a range of decreasing humidities. The instrument corrects for changes in air density in the β-gauge. A method for correcting electronic drift is described. A comparison of liquid water mass measurements of a test aerosol with gravimetric mass measurements gave a regression slope of 0.98 and a standard deviation of 0.7μg/m3. Examples of analyses on a generated aerosol and a fine fraction atmospheric sample are given.