Measurement of laboratory and ambient aerosols with temperature and humidity controlled nephelometry

The relationships between fine particle light scattering extinction coefficient, relative humidity and temperature can be used to quantify sulfate mass concentration and composition for laboratory generated and ambient aerosols. This measurement involves the use of an integrating nephelometer as well as a system for controlling the temperature and relative humidity of the air directly upstream of the nephelometer. Recent improvements in the control of these variables has subsequently enhanced our ability to detect the presence of sulfate compounds in complex atmospheric mixtures. Measurements at two urban sites (Seattle, WA and Riverside, CA) indicate the presence of fine presence of fine particle sulfate compounds mixed with more volatile compounds. Measurements at a 'background' site (Ozette Lake, WA) indicate a mixture of acidic sulfate compounds with compounds that are less volatile than (NH₄)₂SO₄.