Evaluation of wind-induced dust-PM emission from unpaved roads varying in silt content by experimental results

Increasing pressures on land uses lead to dust emission and atmospheric pollution. The U.S. Environmental Protection Agency (EPA) published the document Compilation of Air Pollutant Emission Factors (AP-42), which provides tools to estimate dust emissions from surfaces of unpaved roads. However, unpaved roads are subjected to dust emission by wind, regardless of vehicles traveling, and overall these could be a substantial contribution to mass transfer and pollution. This study integrates experiments in a boundary-later wind tunnel of dust fluxes and numerical model that was developed for PM dispersion in the atmosphere. We tested the dust emission in response to changes in the silt content in the soil. Reference soils were used to simulate dust fluxes under various wind velocities. The results of the wind-induced dust were used for comparison with the calculated emission coefficients by the AP-42. The empirical parameters of dust fluxes by wind were used in the atmospheric PM dispersion model at a spatial scale of several kilometers from the source area. The results show the dependence of dust emission on the silt content, which is the major factor in AP-42, as well as the wind velocity. The AP-42 equations do not accurately predict PM fluxes by wind. Coupling of the AP-42 equations and natural wind erosion is necessary to estimate the total dust emission from unpaved roads. This study can contribute to the establishment of a database for assessments of environmental pollution.