Emission Factor for Antimony in Brake Abrasion Dusts as One of the Major Atmospheric Antimony Sources

Abrasion tests were conducted using a brake dynamometer to determine the antimony (Sb) emission factor originating from automobiles. Abrasion dusts from commercially available brake pads (nonasbestos organic type) were emitted into an enclosed chamber under various braking conditions in terms of initial driving speed and deceleration. Suspended dusts inside the chamber were collected on a quartz fiber filter and weighed. From the experimental data, dust emission could be regressed as a function of the initial kinetic energy loading and the braking time. Using the regression function, the emission factors of brake abrasion dusts under the typical braking conditions (initial driving speed; 50 km/h, deceleration; 1.0 m/s2) were calculated as 5.8 mg/braking/car for PM10 and 3.9 mg/braking/car for PM2.5. The elemental composition of the collected dusts indicated that the fraction originating from disk wear contributed to approximately 30% of the suspended dusts. From these analytical results, it was concluded that the Sb emission factors originating from automobiles were approximately 32 microg Sb/braking/car for PM10 and 22 microg Sb/ braking/car for PM2.5. These essential data will contribute to the modeling of atmospheric Sb concentration alongside roadways and also to the better understanding of Sb source apportionment.