Background

Global dust emissions in the Earth are within the range 300 – 1600 Tg/y. North Africa is the most important source, accounting for 60-70% of these desert dust emissions (Ginoux et al., 2004). Desert dust emitted and transported to distant regions influence on the climate, biogeochemistry and air quality of our planet. Some examples, dust influence on (see details in Rodríguez et al., 2012):

  1. distribution of energy in the Earth.
  2. formation and evolution of clouds.
  3. primary biomass production of the ocean and consequently on the absorption of atmospheric CO2.
  4. urban air quality. An increase in mortality and in respiratory and cardiovascular diseases has been observed during events of long range transport. Moreover, dust particles may act as substratum for the long range transport of microorganisms that may act as pathogens.

The strength of the influence of dust on our environment depends on (Figure 1):

  1. features of dust (composition, mineralogy and shape)
  2. mixing of dust with pollutants (e.g. sulphate, nitrate, ammonium)
  3. dust processing, which result in the deposition of coarser dust particles and in an homogenization of dust with pollutants.
Figure 1. Schematic illustration how microphysical and chemical properties of aerosol dust particles (usually measured by in situ techniques) participate in processes affecting climate. Source: Rodríguez et al. (2012).

Figure 1. Schematic illustration how microphysical and chemical properties of aerosol dust particles (usually measured by in situ techniques) participate in processes affecting climate. Source: Rodríguez et al. (2012).

Previous studies found that the composition of dust exported from the Saharan region, and its mixing with pollutants, experienced a significant variability, which depends on the source region of dust and history of air mass (Figure 2).

Figure 2. A) summer Sahara Air Layer. Red circle indicate the location of Izaña GAW observatory. C-F ) source regions of ammonium-sulphate, non-ammonium-sulphate, nitrate and phosphorus. Source: Rodríguez et al. (2011).

Figure 2. A) summer Sahara Air Layer. Red circle indicate the location of Izaña GAW observatory. C-F) source regions of ammonium-sulphate, non-ammonium-sulphate, nitrate and phosphorus. Source: Rodríguez et al. (2011).

 

References

  • Ginoux, P., Prospero, J.M., Torres, O., Chin, M., 2004. Long-term simulation of global dust distribution with the GOCART model: Correlation with North Atlantic Oscillation. Environmental Modelling Software 19, 113–128.
  • Rodríguez, S., Alastuey, A., Alonso-Pérez, S., Querol, X., Cuevas, E., Abreu-Afonso, J., Viana, M., Pandolfi, M., de la Rosa, J., 2011. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer. Atmospheric Chemistry and Physics 11, 6663–6685.
  • Rodríguez, S., Alastuey, A., Querol, X., 2012. A review of methods for long term in situ characterization of aerosol dust. Aeolian Research 6, 55–74.