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The Rio Desaguadero is the outlet of Lake Titicaca and flows into Lake Poopo in the endorheic watershed of the Altiplano in Bolivia (alt. 3 650 m); its main tributary is the Rio Mauri (fig. 1). The transport of dissolved and suspended solids has been recently evaluated by GUYOT et al. (1990). The data on Total Organic Carbon obtained for the first time in this hydrosystem allow to complement this investigation with an estimation of the organic carbon transport.The Altiplano is a basin filed with tertiary and quaternary sediments. The Eastern cordillera is constituted of primary rocks; the Rio Mauri flow from a tertiary volcanic watershed. The climate is rather cold, semi-arid (700 to 400 mm yr-1) and the vegetation is steppe-like with extensive pastures (sheep, lamas). The rainy season lasts from December to March. No direct pollution source can affect the TOC. The hydrology is very variable (see GUYOT et al., 1990). The base flow issues from Lake Titicaca and depends on the water level in the lake. The Total Suspended Solids (TSS) content is very high during floods. The annual flux of TSS is 6.6 106 t yr-1 at Ulloma, 90 % of transported sediment coming from the Rio Mauri.TOC was measured during 3 sampling series at 15 different stations (table 1). The 25 ml samples were acidified (pH 1) with H3 PO4 and sent to Lyon (France) to be analysed with a Dohrmann DC 80. In February 1988, Dissolved Organic Carbon was measured on filtered samples (Whatman GF/C decarbonated at 550°C). The major elements were analysed in La Paz (Bolivia).Raw TOC data are presented (fig. 2), with a Principal Components Analysis (PCA) for 9 parameters on all the samples (fig. 3). The first axis (52 % of total variance) is a scale of mineralization; it reveals a progressive concentration of dissolved elements in the Lake Poopo outlet (fig. 3B first cluster). The mineralization of these samples seems to be inversely correlated to the discharge flowing from Lake Titicaca for the corresponding series. The second axis (23 % of total variance) shows a correlation between the TOC and the TSS (fig. 3B, 4th cluster). This correlation is obvious for the samples of Dec. 87 and Feb. 88 (table 2), when TSS concentrations are high due to flash floods of some effluents. Equation (1) gives the hast regression of TOC vs TSS.The organic Carbon transported is constituted of dissolved (DOC) or Particulate Organic Carbon (POC). Estimation presented for DOC and POC transport at the three gauging stations (table 3) are based on the following hypotheses :In the Rio Desaguadero, DOC concentrations seam relatively stable (fig. 2D). Upstream of the Rio Mauri, the TOC transported at an average concentration of 11 mg. l-1 is assumed to be mainly DOC flowing out from Lake Titicaca. DOC transport may constitute a relatively constant base flow of organic carbon.Estimation of POC transport is much more difficult. During floods from tributaries, the rise in TOC concentrations correlated with an increase of TSS seems to be essentially due to the POC. Following a classical method (MEYBECK, 1982), a non-linear regression of percentages of POC In TSS vs TSS was calculed (equation 2), using the samples with high TSS concentrations (fig. 4A). Then, the POC fluxes were estimated using daily data of TSS for the gauging stations CA and UL. As most of the TSS come from the Rio Mauri results from this estimation that the flow rate of TOC from this stream would reach 7 t km-2yr-1. But this value according to MEYBECK (1982) is close to the export of a tropical rainforest. Thus, this hypothesis of a POC transport directly linked to the TSS flux must be rejected.POC and TSS, although correlated, have distinct origins. This is shown by the tact that the percentages of POC in TSS in the samples used to calculate equation (2) are much higher than those given by MEYBECK (1982) for world rivers (fig. 4B).A possible explanation for this phenomenon is that the POC could come from Rio Desaguadero Borders and wetlands, often rich in aquatic vegetation, and very extensive in some places (especially upstream of Nazacara and downstream of Eucaliptus). This particulate carbon might be flushed into the mainstream during rainy periods, while at the same time TSS flow down from tributaries. Hypotheses on POC transport (table 3) in the Rio Desaguadero are thus based on a POC/TSS correlation (equation (2)) valid only for the mainstream, the contribution of Rio Mauri to the total flux being estimated on the basis of e TOC export rate of 0.5 t km-2 yr-1.Contribution of these fluxes to organic carbon budgets seems to be negligible for Lake Titicaca, whose phytoplanctonic primary production is estimated at 4 106 t C yr-1 (RICHERSON et al., 1977). When considering only the labile fraction of TOC (ITTEKOT, 1988), the readily matabolizable organic carbon input in Lake Poopo hydrosystem could be evaluated to 36 000 t yr-1, corresponding to about 13 g C m-2yr-1; that might be unimportant for this presumably highly productive lake system.In conclusion, these preliminary data lead to hypotheses which consider the Rio Desaguadero as a very particular hydrosystem in organic carbon transport. If most of the particulate carbon comes from margins, the necessity for maintaining interconnexions between the main Carmel and the wetlands fn future regulation projects must be emphasized.

Keywords: Andes, Bolivie, carbone organique, flux, matières en suspension, rivière, Andes, Bolivia, river, organic carbon, total suspended solids, transport

In order to study the response of native phytoplanktonic communities to different zinc concentrations (2.5, 10, 20 - 25 and 40 - 50 mg.l-1), four bioassays in vitro were carried out. They were conducted in autumn, winter, spring and summer under controlled conditions during a month and the samplings were performed each 2-3 days.The algal responses were variable according to the season and zinc-concentration, species, inoculum density and temperature dependent. 2.5 and 10 mg.l-1 of Zinc in the test medium caused a stimulatory effect on the growth rate of certain diatoms; with 20-25 mg.l-1 of Zinc the development of Chlorella vulgaris (Chlorophyceae) was stimulated, and with 40-50 mg.l-1 of Zinc it was generally found important mortality rates except for Chlorella vulgaris and for some tolerant diatom species: Cyclotella meneghiniana, Gomphonema parvulum, Navicula sp., Nitzschia palea, Nitzschia sp., Pinnularia biceps, Synedra acus and Synedra ulna var. amphirrhynchus. The Cyanophyceae, Euglenophyceae, Tribophyceae, Chrysophyceae, Zygophyceae and Dinophyceae were particularly sensitive to Zinc. In presence of abundant inoculums, the sensivity to Zinc was observed up to 25 mg.l-1 (autumn-20°C, spring-20°C and summer-25°C) while in presence of smaller inoculums the sensivity manifested up to 10 mg.l-1 (winter-15°C). In general, as Zinc concentration increased, Chlorella vulgaris gradually became the dominant taxon and thus, a decrease in the specific diversity of the assayed algal system made of Zinc-tolerant species was observed.

Keywords: Phytoplancton, pollution, bioessai algal multispécifique, métaux lourds dissous, zinc, eau douce, rivière Reconquista (Argentine), Amérique du Sud, Phytoplankton, pollution, multispecific algal bioassay, dissolved heavy metals, zinc, freshwater, Reconquista River (Argentina), South America

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.

Keywords: Claude-Henri Grignon, René Benjamin, maurrassisme, droites radicales françaises, influence intellectuelle, échange esthétique, correspondance, XXe siècle

Keywords: Lyndon B. Johnson, La Nouvelle-Orléans, Noirs, États-Unis, ouragan, Années 1960

AbstractThe fact that Johan van der Keuken was a photographer before becoming a filmmaker and that he never stopped practising photography, particularly late in life, invites us to think about the relationship between still and moving images in his photographs from the point of view of their cinematic potential. Nevertheless, an exploration of the detail of the compositions of these three photographs, the people who appear in them and their interaction amongst themselves, reveals that these images are those of an immobile world. This triptych thus appears to be a reflection on death, on the passage from the world of the living to a beyond, in which the filmmaker occupies the place of someone who has already crossed this threshold. In addition, this article will study the conditions under which van der Keuken, at the age of 17, entered the art field. A critic for the magazine Camera took notice of him at this time, along with two other photographers, and saw him as an unclassifiable photographer even at that early date, declaring himself unable to talk about his work. Van der Keuken's innovation, which he pursued in the cinema, was seen as a break with the dominant tradition of photography at the time, embodied by the great “Family of Man” exhibition by Steichen. In a sense, van der Keuken's later work was the site of a polemic in which he questioned this exhibition's humanism—Barthes had pinpointed its ideology in Mythologies—leading him to take up a political stance.

Keywords: Histoire du Canada, historiographie, épistémologie, progressisme, historien, 19e siècle, François-Xavier Garneau

Contributing to the ever-growing sociological and criminological research on policing of protests and of those on society's margins, this article analyzes the construction of police knowledge in the context of the implementation of the Montreal Police Department's controversial GAMMA project. Created in 2010, the project was intended to track marginal and anarchist activities and movements in the city of Montreal. After a two-year-long legal debate, documents were obtained through provincial access to information legislation and show that, far from dealing only with events that could be criminalized, GAMMA's implementation fundamentally involved problematization of the political marginality of social groups. Characteristics of marginal movements were implicitly considered to be visible indicators of possible criminality, as were specific political convictions and characteristics, which led GAMMA officers to be suspicious of members of such groups. The article explores the subjectivity of police knowledge that underlies the idea of institutionalizing, on a municipal scale, a differential response targeting specific marginal movements. Our results are discussed in the context of recent research on protest policing and marginality, particularly the concepts of “selective incapacitation”, “intelligent control”, and “landscapes of exclusion”.

Keywords: Police, surveillance, mouvements sociaux, marginalité, Québec, Protest policing, surveillance, social movements, marginality, Quebec, Policía, vigilancia, movimientos sociales, marginalidad, Québec

AbstractThe international cultural exchanges field is difficult to study. It is situated at the crossing point of various disciplinary domains and seems to be reluctant to any “ panoptical ” observation or analysis. But a communicational approach to some historical exchanges can help researchers avoid methodological problems. Thanks to the study of various documents related to French producer André Antoine's foreign experience between the 19th and the 20th centuries, it is possible to better understand the role played by the export of theatrical productions in the economy of performing arts. This role reaches financial, symbolic, media and artistic fields. Above all, it's the heterogeneousness of these exchange processes which is noticed. They fall under two categories : that of circulation and of translation.

This article re-examines French Canada's relationship with the Great War through a particular account: that of the journalist Paul Caron who enrolled in the Foreign Legion in 1914. A well-known anti-imperialist, the legionnaire wrote a series of letters from the front that were published in columns of the newspapers Le Devoir and Le Peuple de Montmagny between 1914 and 1917. By assuming the character of a French-Canadian “poilu”, the author offers a cathartic account which underlines the ambivalence of his fellow French-Canadians towards the ongoing conflict, rather than their refusal to participate in it. In this respect, his writings tell us less about the war than they do about the challenge to report it — what part of the horrors of the trenches to disclose? — all the while trying to respect his readers' expectations, particularly those of the nationalists — what war to tell? More than a mere factual report, the artefact produced by Caron reveals the burden and complexities of the cultural framework by which he and his contemporaries, whether they be English or French-Canadians, try to make sense of the war.