Wet Dust Deposition Across Texas During the 2012 Drought: An Overlooked Pathway for Elemental Flux to Ecosystems

Abstract

Abstract Airborne dust can alter ecosystem productivity and biogeochemical cycling by enhancing atmospheric nutrient and pollutant deposition. Wet dust deposition (dust‐in‐rain) is less frequently quantified than dry deposition but represents a potentially significant flux to ecosystems. We quantified dust‐in‐rain event frequency, dust influence on rainwater ionic and elemental composition, and wet dissolved and particulate deposition during weeks affected by dust‐in‐rain and all other weeks (background samples) at two sites across Texas (one arid, Guadalupe Mountains, and one humid, Gulf coastal prairie) during the centennial‐scale 2012 drought. Although dust‐in‐rain was sporadic, a clear dust signature was evident in rainwater. Compared to background samples, crustal species (Fe and Mn) were more prevalent than anthropogenic species (Cu and Zn) in dust‐in‐rain. Volume‐weighted mean rainwater concentrations of K + , Na + , and Cl − and of all particulate elements were also significantly greater in dust‐in‐rain than in background samples. In the Guadalupe Mountains, West Texas, dust‐in‐rain contributed nearly 50% of annual wet dissolved Na + and Cl − and 22–35% of dissolved Ca 2+ , Mg 2+ , K + , and PO 4 3− deposition. In the Gulf coastal prairie, East Texas, dust‐in‐rain delivered 19%, 13%, and 9% of annual wet dissolved PO 4 3− , Ca 2+ , and K + deposition, respectively. A major proportion of annual wet particulate deposition (>56% in Guadalupe Mountains and ~30% in Gulf coastal prairie) similarly occurred with dust‐in‐rain. Our findings show that infrequent dust‐in‐rain events constitute an important but overlooked pathway for elemental flux to ecosystems in arid source and humid receptor sites during severe drought. Quantifying these fluxes is crucial to determine dust impacts on ecosystem processes.