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In the Mediterranean the environment is under pressure from agricultural and urban development, changes in agricultural practices and international markets, and climate change. Moreover, many studies show a steady increase in the agro-pastoral pressure and land degradation and their impacts on water resources and soil, and ultimately the lives of local people. But few studies address these issues across the inclusive scale of large river basins. The conference held at Tipaza in Algeria, from which come several papers published in the Journal of Water Science in 2013, was intended to reflect on the topics, methods and tools available to study the relationships among humans, the environment and sediment transport at this large scale, with the result expected to improve the potential for dialogue between researchers and developers who make decisions for regional macro surfaces. The topics discussed at the conference that appear in the articles published here concern the factors responsible for the variability of sediment transport: climate change and anthropogenic changes, such as agricultural activity and water projects; relationships between land-cover/land-use, rainfall-runoff processes and sediment transport; modeling of sediment transport; and the interest of a multi-scale approach, predominantly a spatial one, for addressing the geographical realities of large basins and scale transfer issues, particularly in Mediterranean and semi-arid areas.

Keywords: Mediterranean, humans, soil, erosion, solid transport, climate change, spatialization, GIS, Méditerranée, homme, sol, érosion, transport solide, changement climatique, spatialisation, SIG

AbstractDrug trafficking is a poorly identified sociological object, even though its development feeds debates about crime, in France as in the majority of Western countries. This ambiguity, resulting from ideological and institutional as well as methodological factors, also translates the complexity of the social forms of trafficking, which are too often reduced to their most simple expression. Two sources of heterogeneity can be described: the heterogeneity of the trafficking on one side, and the heterogeneity of its treatment by the legal system on the other. This article discusses large scale trafficking, that is to say, the hybrid forms little explored between multinational drug trafficking and trade on the street. The author attempts to show the difference between the practices considered in their individual, organisational and social complexity, and their construction by the practices of the police officers and magistrates, including their more total interpretation in legal language, themselves determined by the evolution of the new procedures and policies.

The relationship between the entrepreneur and the investor is often viewed from a conflictual angle based on information asymmetry and on potential stakeholder opportunism. However, venture capital financing includes mixed relationships between venture capitalists and entrepreneurs. In this relationship, venture capitalists seek to orient the funded projects towards prospects of success while securing their investment funds through the negotiation of a set of legal agreements. On the other hand, the entrepreneurs strive to have some leeway to manoeuver while maintaining a certain degree of confidentiality. Our research question concerns the various governance mechanisms that surround the venture capitalist-entrepreneur relationship. Our theoretical framework is based on a double theoretical reading grid, by analyzing this relationship according to the two legal-financial and cognitive approaches of governance. Our results show that venture capitalists not only have a financial impact, but also organizational and cognitive impacts that can govern the internal organization of the venture capital-backed firm. The mode of governance employed can be influenced largely by the individual, organizational, institutional and economic characteristics of the venture capitalists. On the other hand, the managers of venture capital-backed firms may behave in ways that go beyond traditional opportunism, in which they conceal their personal interests, to generate cognitive resources and contribute to value creation.

Keywords: Governance, Gouvernance, venture-capital, capital-risque, cognitive approach, approche cognitive, legal-financial approach, approche juridico-financière, entrepreneurial finance, finance entrepreneuriale

In this article, we propose to examine the impact of the discourse of twinning policies on the development of the city of Bouake, more specifically on its post-conflict reconstruction. The discourse of twinning programs was originally intended to bring people together with the perspective of emulating peace and harmony. However, over the past few decades, this discourse has been extended to the economic sphere in a discursive vision of social action promoting cities now in a globalized and open market. Therefore, following the example of her twin sisters, the diplomatic speech of Bouaké takes a particular configuration that characterizes its ambitions and expectations in cooperation. However, the impact of this discourse on the development of the city is weak and does not meet the basic needs of post-conflict reconstruction. This creates a mismatch between the discourse and the actions that results from it.

Temporal variations of phosphorus concentrations, bacterial abundance and alkaline phosphatase activity (APA) were estimated in situ in a benthic chamber. The chamber used has a surface of 0.4m2 and a volume of 90 l ; it resembles those used in oceanography, with a tube connecting the interior of the chamber to the lake surface. The water in the chamber was permanently mixed by an electric agitation system. The chamber was placed at two points in the Sahela reservoir (Morocco). Point 1 was located near Guelta El Haila, a site that receives both domestic and industrial effluent, and point 2 was located in the centre of the reservoir. During the two incubations, eight samples were taken over 24 d in September and October 1998 from point 1, and seven samples were taken from point 2 over 29 d in October. After each sampling, an equal volume of water was injected into the chamber to avoid bubble formation.Under low dissolved oxygen concentrations in the benthic chamber, we noticed a relatively small elevation in orthophosphate concentrations (from 0.020 to 0.035 mg×L-1 at point 1 and from 0.015 to 0.025 mg×L-1 at point 2) in relation to total phosphorus (from 0.080 to 0.100 mg×L-1 and from 0.035 to 0.040 mg×L-1 at points 1 and 2 respectively). The low residual oxygenation of hypolimnic layer allowed the oxidation of iron, manganese and led to their binding to phosphorus released from the interstitial water. Dissociation of calcium-phosphorus complexes as a result of a pH decrease may have contributed to phosphorus release. The orthophosphate concentrations were relatively low, a situation that favours the synthesis of alkaline phosphatase by aerobic bacteria and facultative aerobic bacteria. In this period, the bacterial abundance and APA were comparable and showed the maximal values (8. 106 bact. ml-1 and 0.323 mmol. PNP l-1.h-1 (phosphate nitrophenol) in point 1 and 6. 106 bact. ml-1and 0.438 mmol. PNP l-1.h-1 in point 2 respectively). The lack of a significant correlation between total APA and bacterial abundance at the two sampling points is probably due to the decrease of aerobic bacteria followed by a repopulation with anaerobic bacteria. However, the relative contribution of two bacterial populations that have different sizes, as at points 1 and 2, showed that the majority of total APA was produced by bacteria that are attached to organic matter. Therefore we suggest that attached bacteria contribute more than free bacteria to APA production.The beginning of anoxic conditions and the decrease in pH favored the dissolution of particulate phosphorus and the liberation of reactive phosphorus. We noted an elevation in orthophosphate concentrations (from 0.035 to 0.050 mg×L-1 at point 1 and stabilised at 0.025 mg×L-1 at point 2) and total phosphorus (from 0.100 to 0.150 mg×L-1 at point 1 and from 0.040 to 0.050 mg×L-1 at point 2). This liberation followed an increase in anaerobic bacterial abundance (from 5×106 to 9.2×106 bact×mL-1 at point 1 and from 3.8×106 to 7.2×106 bact×mL-1 at point 2) and the progressive decrease in APA (from 0.200 to 0.025 mmol PNP L-1 ×h-1 at point 1 and from 0.125 to 0.077 mmol PNP L-1 ×h-1 at point 2). The anaerobic bacteria did not activate their alkaline phosphatase and the synthesis of their enzyme was progressively inhibited by a de-repression phenomenon caused by high phosphorus concentrations.We conclude that low oxygen and a decrease in pH favoured the release of phosphorus by dissolution of chemical complexes: calcium-phosphorus, iron-phosphorus, manganese-phosphorus and aluminium-phosphorus. This release is also the result of bacterial phosphatase activity to which fixed bacteria contributed the most. The release of phosphorus from water-sediment interface is further amplified by phosphate import from domestic and industrial waste waters originating from Taounate, which accelerates the eutrophication process in this reservoir.

Keywords: Phosphore, bactéries, activité phosphatase alcaline, eau-sédiment, réservoir, eutrophisation, Phosphorus, bacteria, alkaline phosphatase activity, water-sediment interface, reservoir, eutrophication

Wastewater discharge is an environmental problem, especially in developing countries. Biological wastewater treatment seems to be an alternative for these countries due to its low cost. Algae are used in such wastewater treatment systems in many parts of the world. In addition to preventing environmental damage, the reuse of treated wastewater can be an alternative water supply in arid regions and during drought periods.In this paper, three algal (Chlamydomonas reinhardtii, Chlorella pyrenoïdosa and Scenedesmus quadricauda) species were isolated from an urban effluent collected from a Mediterranean city (Fez, Morocco, situated between 4° to 7° W and 33° to 35° N) and their ability to remove phosphate and nitrogen was tested under laboratory conditions. The toxicity and uptake of chromium and cadmium were also studied.Fez city wastewater was sampled monthly during one year (2000) at three main stations located along the Boukhrareb stream which crosses the city. The following parameters were measured according to methods described by RODIER J. (1996): Chemical oxygen demand, COD; Biological oxygen demand, BOD; NO3 -; NH4 +; PO43 -; electrical conductivity (EC) and organic matter. Heavy metals (Cr, Fe and Zn) were measured by INAA (Instrumental Thermal Neutron Activation Analysis) in wastewater samples dried on Teflon sheets at 70°C.The collected samples were incubated under controlled conditions and species of alga were identified, isolated, and then transferred to fresh culture medium. Chlamydomonas reinhardtii, Chlorella pyrenoïdosa and Scenedesmus quadricauda were chosen for these experiments because of their abundance in wastewater over the year and for their capacities for biomass production. The removal of nutrients from aqueous media was studied by using monospecific cultures. Algae were in the exponential growth phase when the experiments were started and BG11 culture medium was used under standard growth conditions. Initial concentrations of phosphate and nitrogen were 2.24 mg×L-1 (PO43 -), 12.84 mg×L-1 (NO3 -) and 0.26 mg×L-1 (N-NH4 +). The concentrations decreased during the experimental period, and degrees of removal ranged from 83 to 75% for phosphate, from 85 to 77% for nitrogen and from 52 to 75% for ammonium.To evaluate the sensitivity of the algal cells to heavy metals, the algal strains were exposed for one week to chromium as K2Cr2O7 and cadmium as CdCl2 at concentrations of 0.1, 0.5, 1, 1.5 and 2 ppm (mg×L-1) of Cr or Cd. Culture growth was monitored by microscopic counting of algal cells to determine quantitative biomass changes. Results demonstrated that growth inhibition occurred at 1 ppm Cr and Cd, whereas levels of 1.5 and 2 ppm of both metals were lethal to the cultures, but no effect on growth was seen in algae exposed to 0.1 ppm of Cd or 0.1 ppm of Cr. Scenedesmus quadricauda was more resistant than Chlamydomonas reinhardtii and Chlorella pyrenoïdosa to chromium and cadmium.Radiotracers (51Cr and 109Cd) were used to trace the biosorption of chromium and cadmium by the three algal strains. Cr(VI) as K2 Cr2O7 and Cd as CdCl2 were added to the algal suspension culture to give concentrations of 1, 1.5 and 2 ppm Cd and Cr respectively. At various stages during growth of the unialgal cultures, samples were removed, a pulse of51 Cr or109 Cd was added, and the uptake rates of Cr(VI) and Cd were determined. To evaluate the amount of heavy metals removed by the algal cells, microscopic cell counting was carried out. All the experiments were conducted under the above-mentioned conditions for each concentration studied, the measurements were repeated three times and the mean values from the three replicates were calculated. The results showed that chromium and cadmium removal by algae was dependent on the metal concentration in the culture medium. The quantity of metal removed also varied with algal species, where 20 µg, 23 µg and 35 µg of Cd were accumulated by 106 cells of Chlorella, Chlamydomonas and Scenedesmus respectively at a metal concentration of 2 ppm. About 25 µg of Cr were accumulated by 106 cells of Chlorella and Chlamydomonas whereas, 106 cells of Scenedesmus accumulated 32 µg of Cr at a concentration of 2 ppm.The experimental data presented here demonstrated that there was not a great difference in the uptake capabilities between the three algal strains, and reaffirmed the potential of algae in the purification of metal-contaminated wastewater. This wastewater treatment system has many advantages and it is an efficient way to significantly reduce the release of nutrients (e.g., phosphorus, nitrogen, ammonia) and heavy metals (e.g., chromium and cadmium).

Keywords: Algues, cadmium, chrome, eaux usées, absorption, azote, ahosphates, Algae, cadmium, chromium, wastewater, biosorption, nitrogen, phosphate

SummaryThe mobilization and exploitation of surface water are ancient practices in Tunisia. Installations carried out during last century are exposed to a greater or lesser degree of accelerated silting. The storage capacity of reservoirs is progressively reduced over the course of time. This sometimes accelerated loss of capacity of reserves by silting exceeds the forecasts of hydraulic installation projects. The quantification of trapped sediments is based on the assessment of a reservoir's retained solid matter, either by bathymetric or topographic rising or by Digital Models of Grounds (DMG) corresponding to different dates. These various evaluations of the sediments trapped in reservoirs are, however, sullied with uncertainty. Tunisian reservoirs lose 0.5% to 1% of their storage capacity to silting annually. The analysis of the results presented in this study shows that silting is related to three factors: river hydrology, water reserve management and dredging operations. The comparison between the silting results and the project forecasts highlights relatively significant differences which may be due to river hydrology. Indeed a significant rising in water level can cause an increase in silting above the annual average found during normal hydrological modes. While meandering reservoirs are quickly filled with sediment, linear reservoirs can undergo dredging to remove a significant quantity of sediment. The annual averages in storage capacity losses of the dam under exploitation and its projections up to the year 2010 enable us to quantify the volumes of the sediment trapped as 500 Mm3. In 2030, the loss of storage capacity of the studied reservoirs may reach 43% of their initial storage capacities. Installations upstream and soil and water conservation efforts may reduce the rate of silting and prolong the lifespan of large dams.

Keywords: retenue de barrage, alluvionnement, évolution, Tunisie, reservoir, silting, evolution, Tunisia