Long-Term Efficiencies of Dust Suppressants to Reduce PM10 Emissions from Unpaved Roads.

A 14-month study was undertaken to assess the long-term efficiencies of four dust suppressants (i.e., biocatalyst stabilizer, polymer emulsion, petroleum emulsion with polymer, and nonhazardous crude-oil-containing materials) to reduce the emission of PM10 from public unpaved roads. PM10 emission rates were calculated for each test section and for an untreated section for comparison purposes. Emission rates were determined from PM10 concentrations measured from 1.25 m to 9 m upwind and downwind of the road and above its surface. Calculated emission factors ranged between zero and 1,361 g-PM10/vehicle kilometer traveled (VKT) (average uncertainty = ±35 g-PM10/ VKT) for the four types applied. One week after application, suppressant efficiencies ranged between 33% and 100% for the four types applied. After 8-12 months of exposure to weathering and 4,900-6,400 vehicle passes, the suppressant efficiencies ranged from zero to 95%. Roadway surface properties associated with low-emitting, well-suppressed surfaces are (1) surface silt loading and (2) strength and flexibility of suppressant material as a surface layer or cover. Suppressants that create surface conditions resistant to brittle failure are less prone to deterioration and more likely to increase long-term reduction efficiency for PM10 emissions on unpaved roads.