Atmospheric dust deposition varies by season and elevation in the Colorado Front Range, USA

Heindel, R.C., Putnam A.L., Murphy S.F., Repert, D.A. and Hinckley, E.-L. 2020. Atmospheric dust deposition varies by season and elevation in the Colorado Front Range, USA. JGR Earth Surface 125, e2019JF005436. doi: 10.1029/2019JF005436

Ruth Heindel collecting dust samples on Niwot Ridge

Abstract

As atmospheric dust deposition continues to increase across the southwestern United States, it has the potential to alter ecosystem productivity and structure by delivering nutrients, base cations, and pollutants to remote mountain sites. Due to the sparse distribution of dust monitoring sites, open questions remain about the spatial and temporal variability of dust fluxes and composition across mountainous terrain. We present a 1 year (November 2017 to November 2018) record of seasonal dust fluxes and composition from an elevation transect across the Colorado Front Range extending from the urban plains to the remote alpine. At all nine sites, dust was enriched in the essential nutrient phosphorus and the metals copper, zinc, lead, and cadmium, elements that are enriched in dust deposited at sites across the Rocky Mountain West. We observed a seasonal pattern in dust composition, with the highest concentrations of zinc and cadmium during the summer, when back trajectory modeling suggested a greater contribution of dust from local urban and agricultural regions to the east of the collection sites. During the summer, there was also a trend of higher dust fluxes at lower elevations; dust fluxes ranged from 18.9 ± 0.1 g m−2 yr−1 on the plains to 5.9 ± 0.2 g m−2 yr−1 in the alpine. Our results suggest that urban and agricultural land east of the Colorado Front Range is an important source of nutrients and pollutants to all elevations of the mountain range.