Semi-Volatile Species in PM 2.5: Development and Validation of Integrated and Continuous Samplers for PM 2.5 Research or Exposure Monitoring.
Fine particulate matter (PM) in urban atmospheres contains substantial amounts of semi-volatile material (e.g. ammonium nitrate and semi-volatile organic compounds), some of which is lost when PM is sampled with a filter. This study addresses the hypothesis that the concentration of fine PM will be significantly underestimated in urban environments using the PM2.5 Federal Reference Method (FRM) because of the loss of semi-volatile material from the particles during and after sampling. Moreover, these losses will be substantial in environments where significant concentraitons of semi-volatile PM are present. It is further postulated that fine PM mass, include the semi-volatile fine PM species, is an appropriate surrogate for the components of fine particles which have been associated with observed mortality and morbidity effects in epidemiological studies. The underestimation of the semi-volatile species will tend to over emphasize the importance of non-volatile fine PM components such s sulfate. There is a need for real-time and week-long samping methods, as well as 24-hour methods, all of which accurately measure PM2.5, including the semi-volatile constituents ammonium nitrate and semi-volatile organic material.