Laboratory Method to Assess Efficacy of Dust Suppressants for Dirt and Gravel Roads

Particulate matter (PM) generated from dirt and gravel roads is a concern for both human and environmental health. To help reduce the amount of PM generated, many states allow the use of water coproduced from oil and gas wells (i.e., brines) as road dust suppressants. However, few methods exist to quantify the effectiveness of these brines and other dust suppressants. Here we designed and tested a bench-scale method to test the efficacy of dust suppressants on dirt and gravel road materials. The Standard Proctor test was modified to create discs of road aggregate that could be treated with dust suppressant, dried, and then tumbled in a mechanical drum attached to an aerosol monitor that measured PM generated within the drum. Using two types of road aggregate (DSA and 2RC) and a combination of nine simulated brines, the effects of brine total dissolved solids (TDS), and sodium adsorption ratio (SAR) on dust suppression were calculated. The effects of moisture content and aggregate type were also observed. Higher TDS and lower SAR were found to be good predictors of dust-suppression effectiveness, with the degree of effectiveness partially dependent on the type of road aggregate. The test method provides a means to quickly and reproducibly compare effectiveness of dust suppressants, with other variables such as aggregate type and moisture content, to accurately estimate dust suppression. Comparisons of dust measurements collected within the laboratory and vehicle-based measurements offer the ability to relate laboratory results to conditions encountered on dirt and gravel roads.