Contribution of Cropland Wind Erosion to Air Pollution: Results from a High-resolution Weather-Air Quality Modeling Framework Applied to an Arizona Dust Storm

Being in an arid zone that is frequently submitted to high winds, central Arizona regularly gets impacted by several blowing dust events or dust storms every year. Major consequences of these events are visibility impairment and ensuing road traffic accidents and a variety of health issues induced by inhalation of polluted air loaded with fine particulate matter produced by wind erosion. Despite such problems, and thus a need for guidance on mitigation efforts, studies dealing with dust source attribution for the region are largely missing. Furthermore, existing dust models exhibit large uncertainties and deficiencies in simulating dust events, rendering them of limited use. Therefore, to address some of these model issues, we have developed a high-resolution (1 km) dust modeling system by building upon an existing modeling framework consisting of Weather Research and Forecasting (WRF), FENGSHA (a dust emission model), and Community Multiscale Air Quality (CMAQ) models. In addition to new representations in the dust emission scheme, including roughness correction factor, sandblasting efficiency, and dust source mask, the dust model in this research was ingested with up to date and very high-resolution data on land use, soil texture, and vegetation index. The revised modeling system was used to simulate a springtime dust storm (0809 April 2013) of relatively long duration that caused a regional traffic incident involving minor injuries. The model simulations compared reasonably well against observations of concentration of particulate matter with a diameter of 10 m and smaller (PM10) and satellite-derived dust optical depth and vertical profile of aerosol subtypes. Furthermore, simulation results revealed that the anthropogenic (cropland) dust sources contributed more than half (~53 %) of total PM10, during the dust storm, over the region including Phoenix and western Pinal County. Contrary to the conventional wisdom that desert is the main dust source, our findings for this region suggest that the regional air quality modeling over dryland regions should emphasize an improved representation of dust from agricultural lands as well, especially during high wind episodes, to inform decision-making in order to reduce windblown dust-related hazards on public health and safety.