Continuous and Gravimetric Particulate Matter Mass Concentration as a Function of Thermodynamic Conditions

摘要

Worldwide regulatory air quality standards, objectives and measurement methods for particulaternmatter (PM) have recently come under increased scrutiny as health statistical data suggest linksrnbetween ambient PM mass data and human morbidity and mortality. The USEPA promulgatedrnnew fine PM rules in 1997 for the measurement of PM_(2.5). Globally, other reviews of nationalrnPM regulations have been initiated. Consistency in PM measurements is essential and has majorrnimplications in the development of subsequent control measures, harmonization of worldwidernstandards and objectives, and selection of reference and equivalent methods. In recent yearsrnscientific discussion has included the influence of thermodynamic conditions (e.g., temperature,rnrelative humidity and filter face velocity) on PM retention efficiency of filter-based samplers andrnmonitors. Method-associated thermodynamic conditions can, in some instances, dramaticallyrninfluence the presence of particle-bound water and other light molecular weight chemicalrncomponents such as particulate nitrates and certain organic carbon compounds. Thernmeasurement of fine particle mass presents a new challenge for all PM measurement methodsrnsince a greater fraction of the mass can be semi-volatile. This paper seeks to help identify the keyrnthermodynamic influences upon the routine regulatory measurement of ambient PM.