Contribution of resuspension to particulate matter inmission levels in SE Spain

Abstract

Ambient air particulate matter concentrations were measured at three locations in semi-arid SE Spain during 2005–2007. Sites representative of urban and rural background levels, as well as one representative of a rural area influenced by local mineral industry, were selected. The contribution of coarse particle resuspension (mainly crustal) in the area was assessed by studying the influence of wind speed, human activity and African dust outbreaks on the daily mass concentration and the aerosol number size distribution. Wind and soil characteristics in the area, typical of many semi-arid environments, are not conducive to major dust entrainment events. Twenty-four hour PM 10 mass concentrations, subjected to air quality regulation, present a net decrease as wind speeds increase at the three study sites. Size-resolved measurements in the diameter range 0.25–32 μm with higher temporal resolution, however, show a net increase in the coarse particle concentrations with increasing wind speed, while the smallest particles are diluted. Although suspension is found to occur at all wind speeds, threshold values for an increase in particulate concentration can be identified and show some dependence on the particle size. African dust outbreaks, human activity and wind speed are (in this order) the main contributors for increasing particle sizes.