Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer 1Izaña Atmospheric Research Centre, AEMET Joint Research Unit to CSIC "Studies on Atmospheric Pollution", La Marina, 20, Planta 6, Santa Cruz de Tenerife, 38071, Canary Islands, Spain
13 Jul 2011
2Institute of Environmental Assessment and Water Research (IDǼA), CSIC, Jordi Girona, 18–26, 08034, Barcelona, Spain
3University of Huelva, Joint Research Unit to CSIC "Air Pollution", Campus El Carmen, 21071 Huelva, Spain
Received: 12 Jan 2011 – Published in Atmos. Chem. Phys. Discuss.: 14 Mar 2011Abstract. An analysis of chemical composition data of particulate matter samples (TSP,
PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic
free troposphere at the Izaña Global Atmospheric Watch (GAW) observatory
(Tenerife, Canary Islands) shows that desert dust is very frequently mixed
with particulate pollutants in the Saharan Air Layer (SAL). The study of this
data set with Median Concentrations At Receptor (MCAR) plots allowed the
identification of the potential source regions of the dust and particulate
pollutants. Areas located at the south of the southern slope of the Atlas
mountains emerge as the most frequent source of the soil desert dust advected
to the northern edge of the SAL in summer. Industrial emissions occurring in
Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco
appear as the most important source of the nitrate, ammonium and a fraction
of sulphate (at least 60 % of the sulphate <10 μm transported
from some regions) observed in the SAL. These emissions are mostly linked to
crude oil refineries, phosphate-based fertilizer industry and power plants.
Although desert dust emissions appear as the most frequent source of the
phosphorous observed in the SAL, high P concentrations are observed when the
SAL is affected by emissions from open mines of phosphate and phosphate based
fertilizer industry. The results also show that a significant fraction of the
sulphate (up to 90 % of sulphate <10 μm transported from some
regions) observed in the SAL may be influenced by soil emissions of evaporite
minerals in well defined regions where dry saline lakes (chotts) are present.
These interpretations of the MCAR plots are consistent with the results
obtained with the Positive Matrix Factorization (PMF2) receptor modelling.
The results of this study show that North African industrial pollutants may
be mixed with desert dust and exported to the North Atlantic in the Saharan
Revised: 25 Jun 2011 – Accepted: 27 Jun 2011 – Published: 13 Jul 2011
Citation: Rodríguez, S., Alastuey, A., Alonso-Pérez, S., Querol, X., Cuevas, E., Abreu-Afonso, J., Viana, M., Pérez, N., Pandolfi, M., and de la Rosa, J.: Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer, Atmos. Chem. Phys., 11, 6663-6685, doi:10.5194/acp-11-6663-2011, 2011.