Sources of Atmospheric Dust Particles in California's Salton Sea Basin

Salton Sea, a highly saline lake in Imperial Valley of Southern California, is experiencing a shortage of water input that is leading to water level reductions in its shallow regions and exposing playa surfaces to the atmosphere. We report on ionic and elemental composition of passively collected aerosol particles in this region and quantify the contribution of various dust sources. Depositing dust samples were collected monthly at 5 sites, spanning from remote/background to urban and shoreline locations during 2017-2018, to better understand temporal behavior and regional influence of playa emissions in this arid environment. Ionic and elemental composition of aerosol samples determined by ion chromatography (IC) and inductively-coupled plasma mass spectrometry (ICP-MS) were used along with positive matrix factorization (PMF) to resolve 7 dust source factors in this region. The anthropogenic dust factors contributed to 55-80% of the collected particles, depending on the location and time of the year. Playa emissions were most intense during late spring/early summer, and their influence was significant only at the sites located south of the Salton Sea. Dust fluxes on the playa were higher than typical values in the southwestern US, but approached the values observed in Owens Valley in the late 20^th century. As shown by scanning electron microscopy- energy dispersive x-ray spectroscopy (SEM-EDS) and x-ray diffraction (XRD), playa emissions were enriched in evaporite minerals of magnesium, calcium, and sulfate. Details on temporal and spatial variability of the different dust factors will be presented.