GEOCHEMICAL AND MINERALOGICAL ANALYSIS OF DUST DEPOSITION ON SAN JACINTO PEAK, CA: ELEVATION AND SEASONAL VARIABILITY

Airborne mineral dust from distant and regional sources plays an under appreciated and poorly constrained role in nutrient cycling and soil development, particularly in alpine ecosystems. To quantify dust inputs to montane soils across a range of altitudes, we collected airborne dust along two elevation transects at San Jacinto Peak (SJP) in southern California. This allows us to identify the sources of airborne nutrients reaching soils on SJP and probe the temporal and spatial variability of distal and local dust sources, which may impact climate, human society, and ecosystem fertilization. We deployed six passive dust collectors and co-located climate monitoring stations between 2019 and 2020 along two elevation transects on the north (977-2945m) and south (483-2883m) sides of SJP. We collect these dust traps every four months to assess seasonal variability in dust flux and composition. The sample is divided into two fractions, fine (0.2-30 µm) and coarse (30-400 µm) to distinguish between saltating particles and aeolian dust. HYSPLIT back-trajectory modeling is used to investigate possible regional dust sources and general air trends reaching the sites. Findings show a high degree of variability between the north and south sides of the mountain in both total deposition and mineralogy. Trace elements are measured using ICP-MS to characterize nutrient composition and possible source. Initial grain size analysis indicates fine (<1 µm) modal dust size in comparison to coarse local sediment.