干旱区生态环境知识资源中心

The coast of the Atacama Desert is characterized by the occurrence of strong south- and southwesterly winds. The arid climate, flat geomorphology and the characteristics of the superficial sediments on Pampa Mejillones, located in northern Chile (ca. 23 degrees S), favor the study of eolian erosion and transport processes in this coastal desert. In situ measurements of the horizontal particle flux (G) and winds in the area, together with sedimentological analyses of the uppermost part of the pampa sediments, allowed determination of the significant parameters in the eolian erosion and particle transport process and its seasonality. A local surface roughness parameter (z(0)) of about 10(-3) m was calculated, which is a typical value of desert plains. Seasonally, values of G up to 2, 100 g cm(-1) month(-1) were observed, associated with friction velocities (u*) between 0,4 and 0,5 m s(-1) during the spring of 2000. Similar results were obtained for the years 1999 and 2001. The sedimentology (granulometry and surface texture) and mineralogy of the surface and captured material in the dust traps show that the transported fraction is characterized mainly by quartz and feldspars, with grain-size modes between 75 and 1,000 mu m, similar to those observed in nearby soils and south (upwind) of the capture area. The results obtained and preliminary correlation of measured winds at the different meteorological stations on the Mejillones Peninsula, indicate a direct relationship between the horizontal particle flux towards Mejillones Bay and the regional south-southwest winds, especially during spring and summer, simultaneous with the intensification of winds favoring coastal upwelling in the area.