Search results for "desert"

Airborne measurements of dust layer properties, particle size distribution and mixing state of Saharan dust during SAMUM 2006

2009

The Saharan Mineral Dust Experiment (SAMUM) was conducted in May/June 2006 in southern Morocco. As part of SAMUM, airborne in situ measurements of the particle size distribution in the diameter range 4 nm < Dp < 100 μm were conducted. The aerosol mixing state was determined below Dp < 2.5 μm. Furthermore, the vertical structure of the dust layers was investigated with a nadir-looking high spectral resolution lidar (HSRL). The desert dust aerosol exhibited two size regimes of different mixing states: below 0.5 μm, the particles had a non-volatile core and a volatile coating; larger particles above 0.5 μm consisted of non-volatile components and contained light absorbing material. In…

Consequences of the discovery of Stenasellus (Crustacea, Isopoda, Asellota) 2 in the underground waters of Oman (Arabian Peninsula)

1999

An overview of the present knowledgeof the family Stenasellidae (Asellota: Aselloidea) is presented, focusing on the success of recent investigations of the underground waters of Oman (S.E. Arabian Peninsula). We take up the discovery of four new species of the genus Stenasellus: small species adapted to interstitial biotopes and larger ones typical of karstic aquifers. These species cohabit in ecotones between interstitial and karstic water systems. The putative presence of stenasellids in hypogean waters of Yemen and South Iran is suggested. The taxonomic status of the genus Stenasellus auct. needs to be reconsidered in the future. A scenario to explain the origin and the presence of thes…

Fungi and Sediments

2000

Fungi are saprophytic organisms that can form lichens in symbiosis with an alga. Along with lichens, they excrete large quantities of organic acids, contributing to rock dissolution and neoformation of crystals, mainly oxalates and carbonates. Fungi contribute to the accumulation of manganese and iron as desert varnish and play a major role in the calcium cycle inside calcretes and carbonate soils in arid zones. Fungi constitute an important part of calcified filaments found in calcretes. They are covered with calcium oxalate crystals, which can transform into calcite during early diagenesis. They can also precipitate needle-fiber calcite, a common form of CaCO3 found in soils and calcretes…

La vulnerabilità alla desertificazione della Sicilia

2009

FeMnOx-1: A new microanalytical reference material for the investigation of Mn–Fe rich geological samples

2016

Suitable Mn-Fe rich microanalytical reference materials (MRMs) as calibration material for laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) have not been available. The United States Geological Survey (USGS) in collaboration with the Max Planck Institute for Chemistry has prepared a synthetic MRM, FeMnOx-1, with elevated mass fractions of MnO (25 g/100 g), Fe2O3 (8.5 g/100 g) and high mass fractions of 25 trace elements varying between 200 and 5000 mg/kg. This new MRM has been designed as calibration material for a wide range of different Mn-Fe deposits, such as desert/rock varnish, ocean crusts and nodules as well as Mn accumulations in soils and lakes. Small-scale an…

Città e deserto. Appunti di un viaggio in Giordania. City and desert. Notes from a journey in Jordan

2012

The book is the result of some thoughts that I have gained during my stay in Jordan, where, for a few years, I have been teaching and researching, following an intense exchange activities developed productively thanks to the cooperation agreements between the University of Palermo, the University of Jordan in Amman and Al al-Bayt University of Mafraq.

La vulnerabilitè alla desertificazione della Sicilia

2009

Viene applicata una nuova metodologia che,i cui criteri di analisi vengono illustrati,che può essere considerata un'implementazione del modello DESERT e può costituire un supporto tecnico scientifico per il monitoraggio e la programmazione degli interventi nelle aree identificate a rischio desertificazione.

Patterns of soil microbial biomass and diversity across Mediterranean agroecosystems in areas under desertification risk

2022

Recent trends of temperature change under hot and cold desert climates: Comparing the Sahara (Libya) and Central Asia (Xinjiang, China)

2011

Abstract According to trend computations at three stations each in Sahara desert (Libya), characterized by a “hot” desert type (“BWh”, according to the Koeppen climate classification), and in Central Asia (Xinjiang, China) identified as a “cold” desert type (“BWk”, after Koeppen), increasing annual temperatures were detected over the period 1955–2005 corresponding with global temperature warming. From 1955–1978, negative (decreasing) temperature trends were, however, observed at all three hot desert stations and at two of the three cold desert stations. From 1979–2005, strikingly positive temperature trends were seen at all six stations. In seasonal respects, winter (December to February) a…

Small ice particles at slightly supercooled temperatures in tropical maritime convection

2020

In this paper we show that the origin of the ice phase in tropical cumulus clouds over the sea may occur by primary ice nucleation of small crystals at temperatures just between 0 and −5 ∘C. This was made possible through use of a holographic instrument able to image cloud particles at very high resolution and small size (6 µm). The environment in which the observations were conducted was notable for the presence of desert dust advected over the ocean from the Sahara. However, there is no laboratory evidence to suggest that these dust particles can act as ice nuclei at temperatures warmer than about −10 ∘C, the zone in which the first ice was observed in these clouds. T…