Assessment of heavy metals pollution in the gulf of Gabes (Tunisia) using four mollusk species

Since the establishment of the ‘Tunisian Chemical Group’ in Gabes city, Tunisia, no serious investigations were carried out about the heavy metal pollution in Gabes gulf.  In the present study, the contents of four heavy metals were assessed in four mollusk species (two gastropods, Gibbula ardens and Patella caerulea, and two bivalves, Pinctada radiata and Pinna nobilis), collected from twelve coastal stations. The results obtained showed generally that high concentrations of heavy metals were recorded in the central area of Gabes gulf, nearer to Gabes city; the low concentrations were in contrast found at the edges of this gulf, which is probably due to the chemical pollution generated from the huge industry of phosphoric acid in Gabes city. Comparing the results found with the four examined species, the lowest concentrations were noted with the two bivalve species P. radiata and P. nobilis. The highest heavy metals’ concentrations, noted during this study, are comparable to the findings of other authors in other areas, but they are considerably beyond the standards. A remediation action is necessarily needed either by reducing the amount of heavy metals in the phosphgypums quantities thrown directly in the sea or by stopping completely this harmful industry to protect the marine life in the area. A remediation action is necessarily needed to protect the marine life in the area

Le Numidien de la Tunisie septentrionale: données stratigraphiques et interprétation géodynamique

The Numidian flysch consists of a thick turbiditic sandy and clayey formation of Oligocene-Lower Miocene age which outcrops largely in northern Tunisia. Concerning the relationship between the Numidian formation and its «substratum», two hypothesis are discussed : i) allochtonous Numidian units (tangential abnormal contact) ; ii) autochtonous Numidian units (sedimentary contact : locally downlap). Detailed investigation undertaken in the study area, based on the survey and the dating of lithological logs, coupled with geodynamic and petrogenetic events, lead to the following results : i) absence of tangential tectonic contact in the base of Numidian series ; ii) a significant Tertiary tectonics attested by several phases. Moreover, the Numidian siliciclastic series are affected, like the other Tertiary formations in the North of Tunisia, by south-east ward deep-seated thrusts, oriented N50-60.El flysch Numidiense es una formación arenisco-arcillosa de gran espesor y de edad Oligoceno-Mioceno inferior, que aflora en el norte de Túnez. La naturaleza del contacto basal de esta formación ha suscitado numerosas discusiones. De ellas destacan dos hipótesis: 1) las unidades numidienses alóctonas se apoyan en forma de contacto anormal tangencial, y 2) se trata de unidades autóctonas (contacto sedimentario normal, a veces de tipo "downlap").El levantamiento de cortes litológicos detallados y su datación, combinado con datos de tipo geodinámico y petrogenético, ha permitido confirmar la ausencia de un contacto tectónico tangencial en la base del Numidiense y por el contrario, establecer la existencia de una significativa tectónica terciaria desarrollada en varias fases. Asi, las series siliciclásticas Numidienses se ven afectadas, como otras formaciones terciarias del norte de Túnez, por cabalgamientos de vergencia SE

Influence of aerial seed banks on germination response in three desert plant species

© The Author 2016. Aims To determine if the germination response of desert plant species to a period of aerial storage in field conditions (i.e. mature seeds that remain attached to the parent plant) is comparable to seeds harvested at maturity and stored in ambient laboratory conditions, to better understand the role of aerial seed bank in the germination ecology of desert plants, using one annual and two perennial species. Methods Seeds of three desert plants (Anastatica hierochuntica, Blepharis ciliaris and Scrophularia deserti) that matured in June 2014, were collected from wild plants in June and November 2014, and germinated under two photoperiods (0, 12 hours light) and three thermoperiods (night/day temperatures of 15/25, 20/30 and 25/35°C). Important Findings Seeds of B. ciliaris and S. deserti had significantly higher germination percentages when harvested and stored for five months, compared to being stored in the aerial seed bank. Germination percentages of these two species increased with decreasing temperature and in the presence of light. These results indicate that these species use a combination of aerial and soil seed banks to maintain a percentage of viable seeds through favourable germination periods. Germination percentages of A. hierochuntica were high under all tested circumstances, indicating that this species relies mainly on the aerial seed bank to maintain a percentage of viable seeds through favourable germination periods. This study shows that the population survival strategies of an aerial seed bank are species-specific. These results have practical implications for conservation and habitat restoration for these species, and also for their propagation since early collection of mature fruits and ex situ storage will result in greater germination percentages of some species

Low temperature, authigenic illite and carbonates in a mixed dolomite-clastic lagoonal and pedogenic setting, Spanish Central System, Spain

The aim of this study was to further our understanding of the pedogenic and lacustrine modification of clay minerals. Some of these modifications are of special interest because they constitute reverse weathering reactions, rare in surface environments, and because there is not yet an accurate assessment of their global relevance in mineralogical and geochemical cycles. For this study, two sections from the Central System in Spain were selected. Both are sections through the Uppper Cenomanian-Turonian mixed clastic and carbonate succession, containing both calcite and dolomite, in the Sierra de Guadarrama. Mid-Turonian sea level fall resulted in the formation of a coastal plain environment in which extensive pedogenesis occurred around saline lagoons. The mineralogical changes that have occurred as a result of sedimentation in saline lagoons and as a consequence of pedogenesis are described. Textural relationships indicate that the dolomite cement pre-dates the calcite. Silicate minerals are represented by quartz, kaolinite, illite-smectite, illite, minor plagioclase and alkali feldspar, and trace chlorite and palygorskite. There is a positive correlation between the intensity of pedogenesis and the proportion of illite in the clay assemblage in one of the sections, indicating pedogenic illitisation. In this section, the intensity of the illitisation process increases up, reaching a maximum where pedogenesis is most intense in the middle part, and then decreases as marine influence increases towards the top of the Alcorlo Formation and the overlying marine Tranquera Formation. The clay assemblages are consistent with a slow transformation process from 42 kaolinite to illite by way of illite-smectite, taking place under surface conditions. The illitisation process has resulted in a less Fe-rich, more Mg-, and Al-rich illite than the majority of previously documented cases in the near surface. Formation of Al-rich illite is not therefore restricted to the deep subsurface. The mechanism for low temperature illitisation involves enhanced layer charge resulting from Mg2+ substitution for Al3+ (or Fe3+) and Fe3+ to Fe2+ reduction. Mg2+ enrichment may have occurred principally in saline lagoons or lakes, while Fe3+ to Fe2+ reduction occurred as a result of wetting and drying in a pedogenic environment. So far as it has been possible to establish, this dual mechanism has not previously been documented. This study indicates clearly that the dolomite and calcite are authigenic cements that precipitated in a clastic sediment, probably soon after deposition. Dolomitisation and Mg enrichment of the clay may have occurred at the same time. Seawater is the most probable source of Mg

A Palinspastic Reconstruction of Southern Tunisia: Multiphase Tethyan Rifting, Paleogeographic Inheritance and Petroleum Systems.

Palinspastic recontruction based on seismostratigraphic and seismotectonic data help help identify Tethyan during two major periods (upper Paleozoic, Triassic-Jurassic).Reactivation of major faults rooted in the basement overprints rift sedimentation and basin Framework. This study helps evaluate the petroleum potential of Southern Tunisia, and clarifies the formation and typology of oïl traps

A Palinspastic Reconstruction of Southern Tunisia: Multiphase Tethyan Rifting, Paleogeographic Inheritance and Petroleum Systems.

Palinspastic recontruction based on seismostratigraphic and seismotectonic data help help identify Tethyan during two major periods (upper Paleozoic, Triassic-Jurassic).Reactivation of major faults rooted in the basement overprints rift sedimentation and basin Framework. This study helps evaluate the petroleum potential of Southern Tunisia, and clarifies the formation and typology of oïl traps.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Collaborative agents for modeling traffic regulation systems

The development of surface public transportation networks is a major issue in terms of ecology, economy and society. Their quality in term of punctuality and passengers services (regularity between buses) should be improved. To do so, cities often use regulation systems at junctions that grant priority to buses. However, most of them hardly take into account both public transport vehicles such as buses and private vehicle traffic. This paper proposes a bimodal urban traffic control strategy based on a multi-agent model. The objective is to improve global traffic, to reduce bus delays and to improve bus regularity in congested areas of the network. In our approach, traffic regulation is obtained thanks to communication, collaboration and negotiation between heterogeneous agents. We tested our strategy on a complex network of nine junctions. The results of the simulation are presented

Comparison of absolute and relative growth patterns among five Pinna nobilis populations along the Tunisian coastline: An information theory approach

The variability in absolute and relative growth of Pinna nobilis along the Tunisian coastline was investigated. Five populations of P. nobilis were sampled, three from northern and two from eastern Tunisia. The specimens were aged and ten morphometric characters were measured on each individual. To test if differences existed in absolute and relative growth patterns among the different populations an information theory approach was followed. For absolute growth, von Bertalanffy, Gompertz, the logistic and the power models were fitted in combination with three assumptions regarding inter-population differences in absolute growth patterns: no differences, differences among all five populations or just between northern and eastern populations. The assumption of common absolute growth parameters among all five populations had the greatest support by the data, whereas the assumption of different growth patterns among all five populations had no support. Von Bertalanffy growth model and the power model were both equally supported by the data (while Gompertz had considerably less support and the logistic model had no support), and thus it may not be definitely concluded whether P. nobilis grows asymptotically or not. The P. nobilis populations of the Tunisian coastline had a slow growth and up to an age of ∼ 9 years their shells were smaller than from all other reported populations in the Mediterranean. For relative growth, apart from the classical allometric model Y = aX b , relating the size of a part of a body Y to another reference dimension X, more complicated models were used in combination with the three abovementioned assumptions regarding inter-population differences. Those models, of the form logY = f (logX), either assumed breakpoints in the relative growth trajectories or non-linearities. For most morphometric characters, the classical allometric model had no support by the data and more complicated models were necessary. In most cases, different relative growth either among all five populations or between the northern and eastern population groups was supported by the data. Further investigation is needed to relate the morphological differences observed among different populations of P. nobilis to environmental factors. © 2007 Springer-Verlag