Contribution of Cropland Wind Erosion to Air Pollution: Case of an
Arizona Dust Storm
Abstract
Being in an arid zone that is frequently submitted to high winds,
south-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 in attribution
studies or early warning systems. 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
incorporating new representations in the dust emission scheme, including
roughness correction factor, sandblasting efficiency, and dust source
mask, we implemented, in the dust model, up-to-date and very
high-resolution data on land use, soil texture, and vegetation index. We
used the revised dust modeling system to simulate a springtime dust
storm (08–09 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 μm and smaller
(PM₁₀) and satellite-derived dust optical depth and vertical profile of
aerosol subtypes. Interestingly, simulation results revealed that the
anthropogenic (cropland) dust sources contributed more than half
(~53 % or 260 µg/m³) 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 challenge such belief and 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. Such representations have the
potential to inform decision-making in order to reduce windblown
dust-related hazards on public health and safety.