SALT DYNAMICS OF THE LAS VEGAS WASH WETLANDS, LAS VEGAS NV

The Las Vegas Wash and associated wetlands east of Las Vegas, Nevada are subjected to high evapotranspiration rates characteristic of desert climates, and therefore contain soils heavily concentrated with salts. Erosion of these soils contributes greatly to problems associated with salinity in the Colorado River system, and affects plant communities and surrounding habitat in the wetlands. In this study we use SEM (scanning electron microscope) analyses to determine the salt mineralogy and chemistry of both surface crust and subsoil horizons. Samples were taken at the surface (0-2cm), and at four subsurface depths (2-22cm, 22-61cm, 61-98cm, and 98-140cm). Additional surface samples were obtained from different regions within the Wash. Gypsum is the primary salt mineral in the subsurface. The surface crust contains bloedite (Na₂Mg(SO₄)₂*4H₂0), halite (NaCl), hexahydrite (MgSO₄*5H₂0), thenardite (Na₂SO₄), and mirabilite (Na₂SO₄*10H₂0) in addition to gypsum. The crystal habits of these minerals and their relative abundance are controlled by environmental fluctuations associated with changes in temperature and soil water status. Understanding the soil mineralogy and salt dynamics of the Las Vegas Wash may provide insight into the water chemistry and quality of the Colorado River System, where many of these eroded salts are ultimately transported. Additionally, this data is important for better understanding the physical and chemical characteristics of the soils in the Las Vegas Wash and what their effects may be on the sustainability of the natural habitat and the impact of future land use planning.