Low-cost, time-resolved chemical characterization of atmospheric aerosols

Currently the chemical composition of atmospheric particulate matter is measured either by off-line analyses of time-integrated filter samples, or by in-situ instruments requiring near-constant operator oversight. These measurement approaches result in sparse or limited data coverage. Despite the critical role of composition on the health and environmental impacts of particulate matter, there exist few time-resolved, long-term records of particle-phase chemical composition. New measurement approaches are needed that are robust, easy-to-operate, and suitable for DOE ARM and other atmospheric monitoring facilities for operationally-inexpensive measurements of particle composition. The proposed instrument will offer a robust and straightforward method for the on-line measurement of particle composition that provides moderate chemical and volatility detail with hourly time-resolution and little operator effort. This instrument will measure volatility-resolved particle-phase carbon and oxygen-to-carbon ratio, as well as inorganic sulfur, with the flexibility for future expansion to include nitrogen, phosphorous, or other atmospherically important elements. This instrument will provide hourly data of the parameters necessary for most existing models and descriptions of atmospheric particulate matter, with capital and operational costs that will allow substantially increased spatial and temporal extent of available data. Airborne particles from 0.005 - 2.5 micron will be captured as a concentrated “spot” deposit using our firm’s unique moderate-temperature, water- based condensation method that has been demonstrated in collecting samples for off-line analysis. It will be adapted here for on-line analyses by engineering a compact sample collection and thermal desorption cell.