RT info:eu-repo/semantics/article
T1 Rapid changes of dust geochemistry in the Saharan air layer linked to sources and meteorology.
A1 Sergio Rodríguez
A1 Giulia Calzolai
A1 Massimo Chiari
A1 Silvia Nava
A1 M. Isabel García
A1 Javier López-Solano
A1 Carlos Marrero
A1 López Darias, Jessica
A1 Emilio Cuevas
A1 Alonso Pérez, Silvia
A1 Natalia Prats
A1 Fulvio Amato
A1 Franco Lucarelli
A1 Xavier Querol
A2 Ingeniería Industrial
K1 Saharan air layer
K1 Saharan dust sources
K1 Dust geochemistry
K1 North Africa
K1 Harmattan
K1 NAFDI
AB Based at Iza~ na Observatory (~2400 m a.s.l. in Tenerife), we performed 1-h resolution measurements of elemental composition of dust in the Saharan Air Layer (SAL) and studied the variability of the ratios of these elements to aluminium (elemental ratios). In a period (~1 week) of continuous dust presence (50–200 μg/m3), we observed rapid variations of dust composition; some elemental ratios changed by a factor 2 in a few (5–8) hours. The lowest variability (Normalized Variability Range, %) was found for Si/Al (9%) and Fe/Al (9%), followed by the ratios of K, Ti, Mg, Mn, Ca and Sr to Al (20–80%), and the highest for S/Al, Na/Al and Cl/Al (110–160%) and a number of trace metals (Cr, Cu, Ni, Zn, Zr) and Br (>200%). This variability was induced by the alternating impacts of three of the large North African dust sources: NE Algeria (rich in evaporite minerals bearing Ca, S, Sr, K and Mg and in illite mineral), Western Sahara to Bechar region (containing Na, S and Cl rich Yermosol soils) and SW Sahara – Western Sahel (rich in illite and hematite). We traced the variability in large-scale meteorology using the so-called North African Dipole Intensity (NAFDI: strength of the subtropical Saharan high -Morocco-to the monsoon tropical low -Nigeria-). The mobilization of dust from the different sources was associated with westward propagating Harmattan pulses linked to the change of phase of NAFDI (- to þ), the associated westward shifts of the Saharan Heat Low and convective monsoon inflow. We found a correlation between dust composition in the SAL and NAFDI: moderate NAFDI values (0 to þ2.5) were associated with Ca, K, Na, Mg and S rich dust linked to dust sources in NE Algeria, whereas higher NAFDI values (þ2.5 to þ4) were linked to Fe rich dust (Ca, Na and S depleted) linked to dust sources in SW Sahara – Western Sahel. The results of this study also show that some trace elements (Br, Cr, Ni, Zn and Zr) are influenced by industrial emissions into North Africa.
YR 2020
FD 2020
LK http://riull.ull.es/xmlui/handle/915/39718
UL http://riull.ull.es/xmlui/handle/915/39718
LA Inglés
DS Repositorio institucional de la Universidad de La Laguna
RD 22-nov-2024