Citation:

Volckens, J. SAMPLING AND ANALYSIS OF SEMIVOLATILE AEROSOLS. Presented at State of the Science Workshop on Organic Speciation in Atmospheric Aerosols, Las Vegas, NV, April 5-7, 2004.

Impact/Purpose:

Develop and evaluate methods for the sampling and analysis of PM in ambient air, with emphasis on FRM/FEM for PMc, measurement of carbonaceous aerosols, measurement of biogenic aerosols, comparisons measurements from the STN and IMPROVE monitoring networks, and continuous methods for PM mass and its chemical components.

Description:

Denuder based samplers can effectively separate semivolatile gases from particles and 'freeze' the partitioning in time. Conversely, samples collected on filters partition mass according to the conditions of the influent airstream, which may change over time. As a result these time-integrated sampling techniques do not measure 'average Kp,' but instead report Kp measurements that are weighted towards the end of the sampling event. Several examples of such bias will be presented and discussed. However, denuders are subject to the same types of biases that affect filters and care must be taken in their use. Furthermore, the ratio Kp is easily corrupted by even minute artifacts that affect filters and denuders alike. Some of these errors are easily detected from plots of log Kp vs. log compound vapor pressure, P0 while others are more difficult to identify. Estimates of Kp can vary by up to two orders of magnitude depending on the sampling method used. A need exists to develop an improved sampling technique with less perturbation of semi-volatile equilibrium, shorter sampling periods, and lower limits of detection.

Although this work was reviewed by EPA and approved for presentation, it may not necessarily reflect official Agency policy.

Record Details: