Effects of wind erosion, off-road vehicular activity, atmospheric conditions and the proximity of a metropolitan area on PM10 characteristics in a recreational site

PM10 concentrations were measured at Nellis Dunes Recreation Area (NDRA), Nevada, USA. NDRA is a desert area located 6 km northeast of the metropolitan area of Las Vegas. Three sources contribute to the dust at the site: local wind erosion, off-road vehicular activity and dust production in the city of Las Vegas. PM10 concentrations were measured during one complete year and stored as 20-min averages. Grain-size distribution was also determined from sediment collected in sediment traps. PM10 concentrations at NDRA are greater, and dust is finer in April–September as compared to October–March. Concentrations are also higher during the day than at night. The diurnal pattern of PM10 concentration at NDRA is characterized by a maximum in the early afternoon and a minimum in the morning. In all months except June–August, a secondary peak in concentration occurs around midnight. The higher concentrations during the day hours are not explained by local wind erosion, by meteorological parameters such as wind speed, wind direction, atmospheric stability or ventilation, or by the supply of dust from the Las Vegas metropolis. The diurnal pattern of PM10 concentration in NDRA also differs from that observed at other rural sites in the Las Vegas Valley and in the city itself. The aberrations in the PM10 pattern at NDRA are caused by intense off-road vehicular driving in this area. Although dust from NDRA is blowing towards Las Vegas from late autumn to early spring and also during most of the nights, no quantitative data is currently available to determine the impact NDRA-emitted dust may have on the PM10 concentrations in the city.