Atmospheric Science Seminar: "Seasonal, Spatial, and Long-term Variability of Fine Mineral Dust and Coarse Mass at Remote Sites across the United States"

Presented by: Jenny Hand, CIRA, Colorado State University

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, which include influences on air quality, visibility, radiative forcing, hydrology, heterogeneous chemistry, biogeochemistry, and ecology. The spatial and seasonal variability of ambient FD and CM was characterized at rural and remote sites across the United States using 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 non-local 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 elemental composition in summer indicated contributions from non-local source regions (e.g., North Africa). Finally, long-term trend analyses (2000–2016) indicated increased FD concentrations during spring at sites across the Southwest associated with large scale climate variability. Both FD and CM have increased during summer and fall in the central United States.  As regulated sources of secondary aerosols continue to decline, the importance of FD and CM to the mass budget will continue to increase, especially given that regions and seasons with the highest concentrations also have experienced the largest increases.


Atmospheric Science Seminars



Dunn 101