Spatial and seasonal variability in fine mineral dust and coarse aerosol mass at remote sites across the United States

Abstract

Understanding the spatial and temporal variability in fine mineral dust (FD, mineral aerosols with diameters less than 2.5 µm) and coarse aerosol mass (CM, mass of aerosols with diameters between 2.5 and 10 µm) is important for accurately characterizing and perhaps mitigating their environmental and climate impacts. The spatial and seasonal variability of ambient FD and CM was characterized at rural and remote sites across the United States for 2011–2014 using concentration and elemental chemistry data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) aerosol monitoring network. FD concentrations were highest (and had ≥50% contributions to PM2.5 mass) in the southwestern United States in spring and across the central and southeastern United States in summer (20–30% of PM2.5 mass). CM was highest across the Southwest and southern Great Plains in spring and central United States in spring, summer, and fall (≥70% contributions to PM10 mass). Similar FD and CM seasonal variability was observed near source regions in the Southwest, but a seasonal decoupling was observed in most other regions, suggesting the contribution of nonlocal sources of FD or perhaps non‐dust‐related CM. The seasonal and spatial variability in FD elemental ratios (calcium, iron, and aluminum) was fairly uniform across the West; however, in the eastern United States a shift in summer elemental composition indicated contributions from nonlocal source regions (e.g., North Africa). Finally, long‐term trend analyses (2000–2014) indicated increased FD concentrations during spring at sites across the Southwest and during summer and fall in the southeastern and central United States.

Assessing the Challenges of Surface‐Level Aerosol Mass Estimates From Remote Sensing During the SEAC4RS and SEARCH Campaigns: Baseline Surface Observations and Remote Sensing in the Southeastern United States

“…Highest soil concentrations and mass fractions were at the southern coastal OLF site. The International Cooperative for Aerosol Prediction (ICAP) multimodel ensemble (Sessions et al, 2015), NAAPS reanalysis (Xian et al, ), and aerosol chemistry filter analysis (Hand et al, ) indicate that these events are due to intrusions of African dust.…”

“…Similarly, SO 4 2− concentrations peaked in the summer months by 0.3, 0.4, 0.6, and 0.4 μg/m 3 relative to the winter months for CTR, OLF, YRK, and UAH, respectively. The soil/dust also increased in the summer with an increase in agricultural activity, biomass burnings, and long‐distance advection of African dust (Hand et al, ; Xian et al, ), driving a dip in the PM 2.5 :PM 10 ratio.…”

A Decadal Climatology of Chemical, Physical, and Optical Properties of Ambient Smoke in the Western and Southeastern United States

“…Combustion conditions (i.e., flaming through smoldering) also impact smoke emission factors, chemical composition (e.g., organics, black carbon, and potassium, McMeeking et al, 2009;Lee et al, 2010;Levin et al, 2010;Jen et al, 2019], size, and optical properties . Hand et al (2017) showed that fine dust concentrations are high in the southwestern United States in spring and summer due to abundant local dust sources. Hence, fresh smoke in the west, if dominated by wildfires, may be more absorbing (lower SSA) than in the SE.…”

Sand and Dust Storms: Impact Mitigation

“…However, wind erosion continues on the US Great Plains during times of drought and the potential for land management improvements to be undermined by other policies was highlighted by McCauley et al [136] who attributed part of the blame for a severe dust storm in 1977 to new government incentives to cultivate marginal land. Recent work by Hand et al [137] indicates that fine airborne dust loads (PM 2.5 ) in central and northern parts of the US Great Plains have increased over the period 2000-2014.…”