The use of passive seismological imaging in speleogenetic studies: an example from Kanaan Cave, Lebanon

Among many parameters that control the evolution of caves stands the volume of unconsolidated clay sediments generally produced by the alteration of the calcareous rocks. Here we introduce the use of a passive seismological imaging technique to investigate the clay deposits and estimate its total volume in a cave. Applied for the first time for speleogenesis studies, the HVSR (Horizontal / Vertical Spectral Ration) is a geophysical technique that can help better interpret cave geomorphology. We apply seismological spectral techniques (H/V ratio) on ambient noise vibrations to derive the clay volume, as well as its shape. This technique applied on the clay volume reveals some internal details, such as fallen blocks prior to the deposit accumulation and helps to understand deposit evacuation dynamics. The study focuses on the Kanaan Cave, located in Metn District, Lebanon, and reveals new stages related to the cave speleogenesis. This technique could be applied on ‘paragenetic’ caves where clay volume is frequently present in order to constrain the clay volume and reconstruct the buried floor shape of the cave, underneath the clay deposit

Lebanon

Lebanon is a small territory of extraordinary complexity. It offers paradoxes, which are exciting to understand. Having a small dimension of 10.452 km², this country occupies a special strategic position. Lebanon is located at the crossroads of the Mediterranean and the Arab Orient and was the cradle of civilizations since the Paleolithic. This mountainous country has seen, throughout the history, successive periods of foreign occupation: the Egyptian civilization, Greeks, Romans, Byzantines,..

Biosurfactant-Producing Mucor Strains: Selection, Screening, and Chemical Characterization

Biosurfactants are amphiphilic molecules with surface tension reducing activities. Among biosurfactant producers, fungi have been identified as promising organisms. While many studies have investigated biosurfactant production in fungal species from the Ascomycota and Basidiomycota phyla, less is known concerning species from the Mucoromycota phylum. In this context, the aim of this study was to screen and optimize biosurfactant production in 24 fungal strains, including seven Mucor, three Lichtheimia, and one Absidia species. After cultivation in a medium stimulating surfactant production, the surface activity of cell-free supernatants was measured using both oil spreading and parafilm M tests. Among them, five Mucor strain cell-free supernatants belonging to M. circinelloides, M. lanceolatus, M. mucedo, M. racemosus, and M. plumbeus, showed oil repulsion. Then, the impact of the medium composition on surfactant production was evaluated for eight strains. Three of them, i.e., Mucor circinelloides UBOCC-A-109190, Mucor plumbeus UBOCC-A-111133, and Mucor mucedo UBOCC-A-101353 showed an interesting surfactant production potential, reducing the medium surface tension to 36, 31, and 32 mN/m, respectively. A preliminary characterization of the surfactant molecules produced by these strains was performed and showed that these compounds belonged to the glycolipid family

Liban

Le Liban est au carrefour de la Méditerranée et de l'Orient arabe. Il concrétise une longue histoire naturelle de la construction des paysages levantins jusqu'à leurs façonnements par l’Homme depuis l’Holocène jusqu'à 21e siècle. Ce numéro spécial propose au travers les six articles, des lectures historiques et contemporaine de la transformation des territoires dans sa capitale Beyrouth, dans son espace montagnard et sa plaine agricole. Dans un premier volet, les transformations de l’espace urbain à Beyrouth sont décrites au travers l’occidentalisation des espaces publics depuis la fin du 19e siècle, suivies d’une étude morpho-dynamique à une échelle fine du tissu du bâti de la ville depuis 1950. Dans un deuxième volet, le Mont-Liban a connu aussi une recomposition territoriale de son espace reflétant une mobilité des populations et leurs adaptations depuis le Néolithique jusqu’aux époques historiques. Une étude de cette recomposition politique du territoire montagnard depuis 1975 repositionne le Mont-Liban entre espace « refuges » et espace « mondialisé ». Le dernier volet se focalise sur la plaine agricole de la Beqaa, les transformations de son occupation du sol ainsi que les stratégies d’adaptations adoptées face aux défis accrus de sécheresse. Lebanon is at the crossroads of the Mediterranean basin and the Middle-East. The country’s landscape reflects a variety of ecosystems, topography and micro-climate. Located at the crossroads of human dispersal routes, the landscape is hampered by human activity since the Neolithic time. This issue proposes different case studies regarding territorial transformation divided into three thematic parts. First, the transformation of the urban spaces in Beirut are described through the westernization of public spaces since the end of the 19th century followed by a morpho-dynamic study of the urban fabric of the city since 1950. Second, the mountainous areas of Lebanon were also impacted by human activity and mobility since the Neolithic. A first case study on spatial pattern of human occupation in Mount Lebanon describe the population dynamics and the adaptation strategies adopted in an archeological site. A second case study describe the political transformation of the Mount-Lebanon since 1975 to examine the mountain territory role between a "refuge" and a "globalized" space. The last part focuses on the agricultural sector in the Beqaa plain with two cases studies, one on the drought monitoring since 2001 and the other on land and water uses strategies followed by farmers to cope with drought challenges