Airborne dust accumulation and soil development in the North-East sector of Gran Canaria (Canary Islands, Spain)

Abstract

The island of Gran Canaria is located in the eastern Atlantic, to the west of the Saharan Desert, and, as a result of its proximity, is regularly affected by Saharan dust. When this weather condition occurs (haze conditions) the particulate/aerosol accumulation rate was lightly higher than under nonhaze conditions (5.473.8 mg m À2 h À1 versus 4.372.1 mg m À2 h À1). To quantify the contribution of airborne Saharan dust to soil development in northeastern Gran Canaria, aeolian dust was collected weekly at different altitudes and distances from the coast during a year in a series of collection plots. Mean values of dust accumulation rates decreased with increasing altitude (from 79 to 17 g m À2 yr À1 ). The mineralogy of airborne dust, identified by XRD, was quartz, Mg-calcite, calcite, feldspars, dolomite, magnetite, aragonite, halite, and minor amounts of illite, kaolinite-chlorite and palygorskite. Quartz is considered allochthonous because it is not present in the volcanic substrate of the island. However, the difference in quartz concentration from haze to non-haze conditions was only 10% higher. This suggests an external source, but does not preclude a recycled origin. The recognition of well shaped dolomites, observed by SEM-EDX in collected dust samples and in soils samples of the lowest altitude plot, indicate an edaphic origin, but are later recycled as an airborne component. r

Geomorphological investigations of sediment traps on Lanzarote (Canary Islands) as a key for the interpretation of a palaeoclimate archive off NW Africa

“…Thus, a high dust input on the Canary Islands could also be forced by other factors than aridity, including a change of the origin of dust or human activity connected to destablization in the dust mobilization area. These results were compared with studies on recent Saharan dust accumulation on the Canary Islands: One study points to an actual dust accumulation rate between 1.3 and 6.6 cm/ka depending on the altitude, an average value between 4 and 2 cm/ka seems representative for the altitude of the catchment area of Femés (Menéndez et al, 2007). A pedologic study points to an accumulation rate of about 1.5 cm/ka during the last 260 a (Herrmann et al, 1996).…”

Identification of Saharan dust particles in Pleistocene dune sand- paleosol sequences of Fuerteventura (Canary Islands)

“…Three different synoptic meteorological situations have to be taken into account regarding the dust availability on Fuerteventura: (1) low altitude easterly winds dominant all year long with winter-spring maximum; (2) summertime dust-bearing Saharan Air Layer as a results of northward migration of the intertropical convergence zone (although the main dust transport route is between N15°-21°, a southerly component of flow occur in the lee of the easterly wave); (3) low-level continental trade winds. Modern annual Saharan dust deposition rate is around 20 to 80 g/m 2 / year in the region, the reported grain sizes are primarily in the medium and coarse silt fractions (Menéndez, I. et al 2007). The amount of deposited dust in the past could even be significantly higher (Tsoar, H. and Pye, K. 1987).…”

The role of iron and black carbon in aerosol light absorption

“…Since, in our case, the bulk material was dust, we utilized the density of dust and assumed ρ total of 1 g cm −1 e.g., (Cattle et al, 2002). However, the dust density may vary in the range from around 1 to 2 g cm −1 , e.g., (Sugimae, 1984;Mamane and Dzubay, 1988;Simonson, 1995;Seinfeld et al, 2004;Menendez et al, 2007 ext ,å and C total in this model explain 55% of the variance in the spectral single scattering albedo. The rest of the variance may be explained by the following facts: (i) Fe is not directly related to the optically relevant iron oxide , (ii) other components of mineral dust may contribute to dust absorption (Jacobson, 2001), (iii) spectral absorption of pollution cannot be completely explained by measured BC, (Bond, 2001;Kirchstetter et al, 2004), and (iv) measurement uncertainties.…”