GEOCHEMICAL AND PHYSICAL PROPERTIES OF DUST SOURCE SEDIMENTS IN THE CHIHUAHUAN DESERT AND SOUTHERN HIGH PLAINS

We provide a preliminary reconnaissance and inventory of the geochemistry and texture of dust-producing soils and sediments of the Southern High Plains and Chihuahuan Desert regions in Texas (USA), New Mexico (USA) and Chihuahua (Mexico). Both regions are amongst the major initiation points in North America of aeolian dust plumes transported long distances across the continent. A total of 125 samples of surface soil/sediment (72 from the Southern High Plains and 53 from the Chihuahuan Desert) were obtained from source points of recent dust events detected via remote sensing; analyzed for grain size distribution, mineralogy, elemental chemistry and organic carbon content; and related to land use at the site. Granulometric data shows that dust sources in the Southern High Plains region are generally more sandy-textured compared to those in the Chihuahuan Desert (and, in fact, terrestrial dust sources generally). Dust-producing soils in both regions are organic-carbon-poor. A number of elements potentially associated with agriculture showed strong connectivity to anthropogenic activity (land use for farming). A cluster of samples with enhanced concentrations of heavy metals (arsenic, lead, copper, and chromium) appeared in rangeland sites in the Southern High Plains where land development and petroleum extraction activities were observed. The finest-textured dust-emitting sediments, especially in the Chihuahuan Desert, were significantly associated with higher concentrations of elements (calcium, magnesium, and strontium) associated with carbonate minerals: the coarser dust-emitting sediments of the Southern High Plains were dominated by quartz with proportionally fewer sites bearing calcite or other minerals. These results can be used towards developing a preliminary source apportionment tool to understand and trace the environmental impacts of dust events from these two zones locally, regionally, and continentally.