Wintertime PM2.5 and PM10 Source Apportionment at Sacramenio, California

摘要

The chemical mass balance (CMB) model was applied to winter (November through January) 1991-1996 PM2.5 and PM10 data from the Sacramento 13th and T Streets site in order to identify the contributions from major source cat- egories to peak 24-hr ambient PM2.5, and PM10 levels. The average monthly PM10 monitoring data for the nine-year period in Sacramento County indicate that elevated con- centrations are typical in the winter months. Concentra- tions on days of highest PM10 are dominated by the PM2.5, fraction. One factor contributing to increased PM2.5 con- centrations in the winter is meteorology (cool tempera- tures, low wind speeds, low inversion layers, and more humid conditions) that favors the formation of second- ary nitrate and sulfate aerosols. Residential wood burn- ing also elevates fine particulate concentrations in the Sacramento area. The results of the CMB analysis highlight three key points. First, the source apportionment results indicate that primary motor vehicle exhaust and wood smoke are significant sources of both PM2.5 and PM10 in winter. Sec- ond, nitrates, secondarily formed as a result of motor- vehicle and other sources of nitrogen oxide (NOx), are an- other principal cause of the high PM2.5 and PM10 levels during the winter months. Third, fugitive dust, whether it is resuspended soil and dust or agricultural tillage, is not the major contributor to peak winter PM2.5 and PM10 levels in the Sacramento area.