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

Integrated socio-hydrogeological approach to tackle nitrate contamination in groundwater resources. The case of Grombalia Basin (Tunisia)

Nitrate contamination still remains one of the main groundwater quality issues in several aquifers worldwide, despite the perduring efforts of the international scientific community to effectively tackle this problem. The classical hydrogeological and isotopic investigations are obviously of paramount importance for the characterization of contaminant sources, but are clearly not sufficient for the correct and long-term protection of groundwater resources. This paper aims at demonstrating the effectiveness of the socio-hydrogeological approach as the best tool to tackle groundwater quality issues, while contributing bridging the gap between science and society. An integrated survey, including land use, hydrochemical (physicochemical parameters and major ions) and isotopic (delta N-15(No3) and delta O-18(No3)) analyses, coupled to capacity building and participatory activities was carried out to correctly attribute the nitrate origin in groundwater from the Grombalia Basin (North Tunisia), a region where only synthetic fertilizers have been generally identified as the main source of such pollution. Results demonstrates that the basin is characterized by high nitrate concentrations, often exceeding the statutory limits for drinking water, in both the shallow and deep aquifers, whereas sources are associated to both agricultural and urban activities

Influence of temperature, salinity and Mg:Ca ratio on microbially-mediated formation of Mg-rich carbonates by Virgibacillus strains isolated from a sabkha environment.

Studies have demonstrated that microbes facilitate the incorporation of Mg into carbonate minerals, leading to the formation of potential dolomite precursors. Most microbes that are capable of mediating Mg-rich carbonates have been isolated from evaporitic environments in which temperature and salinity are higher than those of average marine environments. However, how such physicochemical factors affect and concur with microbial activity influencing mineral precipitation remains poorly constrained. Here, we report the results of laboratory precipitation experiments using two mineral-forming Virgibacillus strains and one non-mineral-forming strain of Bacillus licheniformis, all isolated from the Dohat Faishakh sabkha in Qatar. They were grown under different combinations of temperature (20°, 30°, 40 °C), salinity (3.5, 7.5, 10 NaCl %w/v), and Mg:Ca ratios (1:1, 6:1 and 12:1). Our results show that the incorporation of Mg into the carbonate minerals is significantly affected by all of the three tested factors. With a Mg:Ca ratio of 1, no Mg-rich carbonates formed during the experiments. With a Mg:Ca ratios of 6 and 12, multivariate analysis indicates that temperature has the highest impact followed by salinity and Mg:Ca ratio. The outcome of this study suggests that warm and saline environments are particularly favourable for microbially mediated formation of Mg-rich carbonates and provides new insight for interpreting ancient dolomite formations

Specific heat and magnetocaloric effect in Pr1-xAgxMnO3 manganites

The magnetocaloric effect in alternating magnetic fields has been investigated in Pr1-xAgxMnO3 manganites with x=0.05-0.25. The stepwise reversal of the sign of the magnetocaloric effect has been revealed in a weakly doped sample (x=0.05) at low temperatures (~80 K). This reversal is attributed to the coexistence of the ferromagnetic and canted antiferromagnetic phases with different critical temperatures.Comment: 4 pages, 4 figure

Synthesis and structure of new pyrochlore-type oxides Ln2ScNbO7 (Ln = Pr, Nd, Eu, Gd, Dy)

We report the synthesis and structural study of mixed oxides in the Ln2ScNbO7 series. New phases with Ln = Pr, Eu, Gd and Dy are obtained. All crystallize in the cubic pyrochlore structure type, space group F-d3m, with no Sc-Nb ordering on the B-site. The structures are determined by Rietveld refinement. The evolution of cell parameters, interatomic distances and angles as a function of lanthanide cation size is discussed. Magnetic measurements show the absence of ordering down to 2 K, in agreement with the presence of strong geometric frustration in the lanthanide sublattice. The europium phase shows a peculiar magnetic behaviour; its magnetic susceptibility becomes constant below ca 50 K. This feature confirms the behaviour observed previously on Eu2Ti2O7 and is ascribed to crystal field effects

Propriétés mécaniques de films multicouches de polyélectrolytes

Les films multicouches de polyélectrolytes sont constitués d'une superposition alternée de polyélectrolytes de charges opposées, qui s'assemblent par interaction électrostatique pour former des films dont l'épaisseur peut varier de quelques longueurs moléculaires à plusieurs dizaines de µm. Ces matériaux suscitent actuellement un intérêt croissant en raison de leurs utilisations potentielles dans la réalisation de photodiodes, de membranes sélectives ou de revêtements biocompatibles. Nous présentons une étude du comportement du module de cisaillement complexe réalisée sur des films multicouches réticulés et non réticulés, constitués d'acide hyaluronique et de poly-L-lysine. Les mesures ont été effectuées avec le dispositif de piézorhéologie, que nous avons récemment développé, et qui permet de caractériser la réponse mécanique d'un échantillon mince (~10µm) sur une gamme de fréquence étendue et pour de très faibles déformations appliquées. Cette communication illustre l'intérêt de la piézorhéologie pour l'étude des propriétés mécaniques des systèmes lamellaires d'intérêt biologique

Effect of rosemary leaves and essential oil on turkey sausage quality

The purpose of this study was to evaluate the effect of rosemary essential oil (250–1000 ppm) or its leaves (0.5–2%) on the quality of turkey sausage. The addition of essential oil had no significant effect on the sausage texture and colour parameters. A high rosemary leaves level resulted in an increase in sausage hardness and chewiness and a decrease in lightness (L*) with respect to the control sausage. Sensory evaluation indicated that rosemary essential oil and its leaves increased the taste and the aroma scores of turkey sausage depending on the concentration. The obtained results also showed that rosemary leaves (0.5%) were more effective than essential oil in reducing total plate counts, TBARS, K232, and K270 values during chill storage, in comparison with the control product. This will contribute to reducing the use of chemical additives, which are badly perceived by consumers, while increasing the sensory properties of such products

Use of environmental isotopes to assess the sustainability of intensively exploited aquifer systems (2012‐2015)

Intensive exploitation of groundwater over longer period has led, in many important aquifers, to marked lowering of water tables, increasing exploitation costs, and often, to a progressive deterioration of water quality. Concentrated pumping may also alter flow patterns permanently with the risk of migration of pollutants into aquifers from the surrounding aquifers or surface water bodies due to lack of physical protection to prevent them. Isotope hydrology tools have proven to be very useful in assessing groundwater hydrology, addressing aspects related to recharge processes, delineation of flow patterns, water quality issues and interactions with other water bodies; this unique information can be further used to evaluate long term aquifer sustainability. The objective of the Coordinated Research Project F33019 is to develop and review approaches and methodologies, mostly based on the combined use of conventional hydrogeological techniques and environmental isotopes, to assess the response of groundwater systems to intensive exploitation and groundwater availability. Access to new dating tools and approaches for groundwater dating covering different time scales offers the possibility to evaluate changes in groundwater dynamics and flow patterns, providing key data to predict the evolution of aquifers and their sustainability as major sources of water. The CRP aims to assess the performance of these new tools and approaches and the possible adoption of these methods by water management experts