Examination of the Multiplier Used to Estimate PM2.5 Fugitive Dust Emissions from PM10

Background and Overview The major sources of fugitive dust emissions are paved and unpaved roads, construction, agricultural operations, minerals industries and wind erosion from both agricultural and non agricultural lands. Fugitive dust in the ambient air is predominantly comprised of coarse particles (between 10 and 2.5um) and is a relatively minor part of fine PM, i.e., PM2.5. However, the emissions inventory suggests that about one half of primary PM2.5 emissions are from fugitive dust, and these emissions contribute to the overestimation of ambient PM2.5 concentrations by air quality models. This overestimation creates problems for those involved in PM2.5, regional haze and PM Coarse analyses. Most experts agree that this overestimation is due to a combination of shortcomings in the inventory-modeling process: 1) the multiplier used to “scale” or infer PM2.5 from PM10 emissions in the inventory, 2) faulty emission factor algorithms, 3) imprecise or difficult to obtain activity data to apply these algorithms (including inability to account for the effect of actual meteorological conditions on emissions), and 4) modeling deficiencies (especially in the treatment of particles near their point of emissions). A method was developed to improve the treatment of particles near their point of release (Pace 2004). Also, work is underway in some areas to improve activity data for fugitive dust categories in some areas. The emissions algorithms for paved and unpaved roads were revised within the past few years to incorporate minor improvements. This paper reviews the current data related to the multiplier used to “scale” or infer PM2.5 from PM10 emissions in the inventory.