Résumé : Digitized with funding from the Digital Library of the Caribbean grant awarded by TICFIA.
South America -- Aruba -- Bushiribana -- Northern coast
Caribbean

Droits : Copyright, Erich Kesse, 2008. May be used in accord with Creative Commons license allowing Attribution + Noncommercial + ShareAlike (by-nc-sa).

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : Tropical forests of the Guiana Shield are the most affected by gold-mining in South America,experiencing an exponential increase in deforestation since the early 2000’s.Using yearly deforestation data encompassing Guyana, Suriname, French Guiana and theBrazilian State of Amapá, we demonstrated a strong relationship between deforestation due togold-mining and gold-prices at the regional scale. In order to assess additional drivers ofdeforestation due to gold-mining, we focused on the national scale and highlighted theheterogeneity of the response to gold-prices under different political contexts. Deforestation dueto gold-mining over the Guiana Shield occurs mainly in Guyana and Suriname. On the contrary,past and current repressive policies in Amapá and French Guiana likely contribute to thedecorrelation of deforestation and gold prices. In this work, wefinally present a case studyfocusing on French Guiana and Suriname, two neighbouring countries with very different levelsof law enforcement against illegal gold-mining. We developed a modelling framework to estimatepotential deforestation leakages from French Guiana to Suriname in the border areas. Based onour assumptions, we estimated a decrease in deforestation due to gold-mining of approx. 4 300hectares in French Guiana and an increase of approx. 12 100 hectares in Suriname in response tothe active military repression of illegal gold-mining launched in French Guiana.Gold-mining in the Guiana Shield provides challenging questions regarding REDDþimplementation. These questions are discussed at the end of this study and are important topolicy makers who need to provide sustainable alternative employment to local populations inorder to ensure the effectiveness of environmental policies.
ISSN: 1748-9326

hal-01512075
https://hal.archives-ouvertes.fr/hal-01512075
https://hal.archives-ouvertes.fr/hal-01512075/document
https://hal.archives-ouvertes.fr/hal-01512075/file/document%20%2828%29_%7B81107B08-30D1-44D2-877D-32F6DFAEF28A%7D.pdf
DOI : 10.1088/1748-9326/aa6082

Éditeur(s) : Latin American Collection, George A. Smathers Libraries, University of Florida Latin American Collection, George A. Smathers Libraries, University of Florida ( Gainesville, FL )
Résumé : Source: University of Florida Latin American Collection, Gainesville, FL. Resources: Microfilm of The Creole, Port of Spain Gazette, and Royal Gazette of British Guiana

Droits : Applicable rights reserved.
http://ufdc.ufl.edu/AA00016150/00001

Éditeur(s) : Latin American Collection, George A. Smathers Libraries, University of Florida Department of English, University of Florida Latin American Collection, George A. Smathers Libraries, University of Florida ( Gainesville, FL ) Department of English, University of Florida ( Gainesville, FL )
Résumé : Source: University of Florida Latin American Collection, Gainesville, FL. Resources: Microfilm of The Creole, Port of Spain Gazette, and Royal Gazette of British Guiana

Droits : [cc by-nc-sa] This item is licensed with the Creative Commons Attribution Non-Commercial Share Alike License. This license lets others remix, tweak, and build upon this work non-commercially, as long as they credit the author and license their new creations under the identical terms.
http://ufdc.ufl.edu/AA00016150/00001

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BACKGROUND:In French Guiana, a French overseas territory in South America, 6 to 10 thousands undocumented persons work illegally in gold mining sites in the Amazonian forest. Precarious life conditions lead to poor health but few data exist on the health status of illegal gold miners in French Guiana. The objective of this article was to describe the sociodemographic and health status of this vulnerable population.METHOD:A prospective cross-sectional survey was conducted in 2015 on gold mine supply sites at the border between French Guiana and Suriname. Health status was assessed through medical examination, past medical history, haemoglobin concentration, and HIV and malaria testing. A questionnaire was used to collect data about the migration itinerary and life conditions on mining sites.RESULTS:Among the 421 adults included in the study, 93.8% (395/421) were Brazilian, mainly from Maranhão (55.7%, 220/395), the poorest Brazilian state. The sex ratio was 2.4. Overall, 48% of persons never went to school or beyond the primary level. The median time spent in gold mining was quite long (10 years), with a high turn-over. One third of the surveyed population (37.1%, 156/421) had high blood pressure, and only two had a medical follow-up. Most persons had experienced malaria (89.3%, 376/421). They declared frequent arboviroses and digestive disorders. Active leishmaniasis was observed in 8.3% of gold miners. Among women, 28.5% were anemic. Concerning HIV, 36.6% (154/421) of persons, mainly men, never got tested before and 6 were tested positive, which represented an HIV prevalence of 1.43% (95%CI =0.29-2.5).CONCLUSION:These findings support the hypothesis that mining in remote areas is linked to several specific illnesses. Theoretically, gold miners would be presumed to start their economical migration to French Guiana as a healthy group. However, their strenuous working and living conditions there lead to poor health caused by infectious and non infectious diseases. This description of their health status is precious for health policy planners in French Guiana given the importance of controlling communicable disease, and the severity and range of specific illnesses acquired by this neglected population.TRIAL REGISTRATION:Clinical trial registration PRS N° NCT02903706 . Retrospectively registered 09/13/2016.
ISSN: 1471-2458

inserm-01566314
http://www.hal.inserm.fr/inserm-01566314
http://www.hal.inserm.fr/inserm-01566314/document
http://www.hal.inserm.fr/inserm-01566314/file/2017%2C%20Douine%20-%20Illegal%20gold%20miners%20in%20French%20Guiana.pdf
DOI : 10.1016/S0140-6736(10)62169-1

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Total mercury (HgT) and monomethylmercury (MMHg) were investigated in a tropical head watershed (1 km(2)) of French Guiana. The watershed includes a pristine area on the hill slopes and a former gold mined flat in the bottomland. Concentrations of dissolved and particulate HgT and MMHg were measured in rain, throughfall, soil water and at three points along the stream. Samples were taken in-between and during 14 storm events at the beginning and middle of the 2005 and 2006 rainy seasons. Dissolved and particulate HgT concentrations in the stream slightly increased downstream, while dissolved and particulate MMHg concentrations were low at the pristine sub-watershed outlet (median = 0.006 ng L-1 and 1.84 ng g(-1), respectively) and sharply increased at the gold mined flat outlet (median = 0.056 ng L-1 and 6.80 ng g(-1), respectively). Oxisols, which are dominant in the pristine area act as a sink of HgT and MMHg from rain and throughfall inputs. Hydromorphic soils in the flat are strongly contaminated with Hg (including Hg droplets) and their structure has been disturbed by former gold-mining processes, leading to multiple stagnant water areas where biogeochemical conditions are favorable for methylation. In the former gold mined flat high dissolved MMHg concentrations (up to 0.8 ng L-1) were measured in puddles or suboxic soil pore waters, whereas high dissolved HgT concentrations were found in lower Eh conditions. Iron-reducing bacteria were suggested as the main methylators since highest concentrations for dissolved MMHg were associated with high dissolved ferrous iron concentrations. The connection between saturated areas and stagnant waters with the hydrographic network during rain events leads to the export of dissolved MMHg and HgT in stream waters, especially at the beginning of the rainy season. As both legal and illegal gold-mining continues to expand in French Guiana, an increase in dissolved and particulate MMHg emissions in the hydrographic network is expected. This will enhance MMHg bio-amplification and present a threat to local populations, whose diet relies mainly on fish.
Water Research (0043-1354) (Pergamon-elsevier Science Ltd), 2011-04 , Vol. 45 , N. 8 , P. 2659-2669

Droits : 2011 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/00035/14628/12134.pdf
DOI:10.1016/j.watres.2011.02.022
http://archimer.ifremer.fr/doc/00035/14628/

Éditeur(s) : HAL CCSD
Résumé : International audience
Despite the recent interest in psychiatric illness in prison, the psychopathology of the Remire-Montjoly prison population remains largely unknown. Subject to significant population movements, French Guiana and its prison houses a very mixed population in which recent history has left a strong mark (earthquake in Haïti, civil war in Suriname, violence related to gold mining population and drug trafficking). These negative life events appear as potential vectors of psychological trauma. Additionally, strong links have been established in the literature between post-traumatic stress disorder (PTSD) and many other psychiatric disorders, including suicidal behavior and addictions. Under these conditions, we felt it essential to focus on the identification of PTSD in this sensitive population.Through adapted reception interviews, we tried to identify the PTSD, to describe by means of socio-demographic factors the studied population and to detect psychiatric comorbidities. The screening tool was the M.I.N.I. 5.0, which identifies 17 psychiatric disorders including the PTSD, based on the DSM IV definition. The target population was the prison incomers, agreeing to participate in the study, aged more than 18 years old and imprisoned between 18 January 2013 and 31 December 2013. To this date, 549 inmates were included in the study.The main result of this study was a prevalence of PTSD of 17% for incomers in detention. We found that the PTSD+ population is more likely to be female (15% against 7% p = 0.0246), which is consistent with the literature data. The M.I.N.I. 5.0 showed a higher prevalence of psychiatric disorders in the PTSD+ group. This association was confirmed in several types of pathology like mood disorders including: major depressive episode and manic or hypomanic episode, suicidal risk, some anxiety disorders including: panic disorder, obsessive-compulsive disorder and generalized anxiety disorder. Strong association was found for current major depressive episode, current manic or hypomanic episode and suicidal risk (p < 0.005).The prevalence of PTSD is very high in this study, about 24 times higher than in a general population survey using the same screening tool.A large number of comorbidities have been identified, which corresponds to those described in the literature. The specific issues of psychiatry in prison lead us to examine more specifically the significance of the results about suicide risk. A comprehensive suicide risk (sum of medium and high risk screened by the M.I.N.I.) was found in significantly more PTSD+ inmates (17% versus 7%, p = 0.005). This study supports the need for routine screening of PTSD among incomers in detention. This disease is both worrying and common in this population but the real issues are the comorbidities. Suicidal potential is among the most important issues in detention. Its evaluation should be completed by an early recognition of a PTSD.
Soumis à des mouvements de population importants, la Guyane Française et son centre pénitentiaire abritentune population métissée chez qui l’histoire récente a laissé une empreinte forte (tremblement de terre en Haïti,guerre civile au Suriname, violence liée à l’orpaillage et au trafic de stupéfiants). Ces événements de vienégatifs apparaissent comme autant de vecteurs potentiels de psychotraumatismes. Dans ces conditions, il nous a paru essentiel de mettre l’accent sur le repérage du TSPT (Trouble de Stress Post-traumatique) dans cette population sensible. A l'aide d’entretiens d’accueil dédiés nous nous sommes proposé de repérer les TSPT, de décrire sur un plan sociodémographique la population étudiée et de rechercher les comorbidités psychiatriques. Le résultat principal de cette étude était une prévalence du TSPT de 17% chez les arrivants en détention. Le MINI 5.0 a montré une prévalence plus élevée des pathologies psychiatriques dans le groupe présentant un TSPT avec un lien très fort (p<0.005) pour l’épisode dépressif majeur actuel, l’épisode (hypo)maniaque actuel et le risque suicidaire. Cette étude appuie la nécessité d’avoir un dépistage systématique du TSPT chez les arrivants en détention. Cette pathologie est à la fois fréquente dans cette population et invalidante mais ce sont ses comorbidités, dont le potentiel suicidaire, qui font tout l’enjeu d’un repérage précoce.
ISSN: 0383-6320

inserm-01421075
http://www.hal.inserm.fr/inserm-01421075
http://www.hal.inserm.fr/inserm-01421075/document
http://www.hal.inserm.fr/inserm-01421075/file/2016%2C%20Arnal%20-%20Post-Traumatic%20Stress%20Disorder%20among%20Incomers%20in%20Remire-Montjoly%20Prison%2C%20French%20Guiana.pdf
PUBMED : 27570960

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
PURPOSE: Dairy farming is a risk factor for the development of chronic obstructive pulmonary disease (COPD). We assessed the prevalence of farming-induced COPD (FI-COPD) using a new screening device, and we analyzed symptoms and occupational risk factors. METHODS: We performed on-site screening study of bronchial obstruction using an electronic mini-spirometer (EMS) on an entire population of dairy farmers (n = 147) from two villages in Brittany, France. Suspected bronchial obstruction (FEV1/FEV6 <0.8) was confirmed with standardized lung function tests (FEV1/FVC ≤0.7). We assessed past medical histories, respiratory symptoms, and occupational tasks of subjects with bronchial obstruction; asthmatics were defined as atopic and/or reversible; smoking-induced COPD patients were defined as non-reversible, non-atopic with smoking histories (≥5 PY); and FI-COPD patients were defined as non-reversible, non-atopic, and non-smokers. RESULTS: Using the EMS, 30.6% (n = 45) of dairy farmers were suspected of bronchial obstruction and underwent standardized spirometry. The FEV1/FEV6 ratio and FEV1/FVC ratio were in good agreement (r² = 0.66, P < 0.0001). The prevalence of confirmed bronchial obstruction was 9.5% (n = 14), which included 4 asthmatics, 3 smoking-induced COPD subjects, and 7 FI-COPD subjects. All the COPD patients were GOLD Stage II, and none were aware of their respiratory disease. Foddering duration was significantly higher in FI-COPD subjects compared with non-obstructive subjects, with 44 versus 17 min/day, respectively. CONCLUSIONS: The EMS was a convenient mean of screening for bronchial obstruction, especially in on-site settings, and allowed us to diagnose FI-COPD in a non-spontaneously complaining dairy farmer population. Foddering was considered a significant risk factor.
ISSN: 0340-0131

hal-00872929
https://hal.archives-ouvertes.fr/hal-00872929
DOI : 10.1007/s00420-011-0708-6
PUBMED : 21986906

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Gold mineralisation in the Yatela Main gold mine is hosted in a saprolitic residuum situated above Birimian supracrustal rocks, and at depth. The supracrustal rocks comprise metamorphosed calcitic and dolomitic marbles that were intruded by diorite (2106 ± 10 Ma, 207Pb/206Pb), and sandstone-siltstone-shale sequences (youngest detrital zircon population dated at 2139 ± 6 Ma). In-situ gold-sulphide mineralisation is associated with hydrothermal activity synchronous to emplacement of the diorite and forms a sub-economic resource; however, the overlying saprolitic residuum hosts economic gold mineralisation in friable lateritized palaeosols and aeolian sands (loess).Samples of saprolitic residuum were studied to investigate the morphology and composition of gold grains as a proxy for distance from source (and possible exploration vector) because the deposit hosts both angular and detrital gold suggesting both proximal and distal sources. U–Pb geochronology of detrital zircons also indicated a proximal and distal source, with the age spectra giving Archaean (2.83–3.28 Ga), and Palaeoproterozoic (1.95–2.20 Ga) to Neoproterozoic (1.1–1.8 Ga) zircons in the Yatela depocentre. The 1.1–1.8 Ga age spectrum restricts the maximum age for the first deposition of the sedimentary units in the Neoproterozoic, or during early deposition in the Taoudeni Basin. Models for formation of the residuum include distal and proximal sources for detritus into the depocentre, however, it is more likely that material was sourced locally and included recycled material. The creation of a deep laterite weathering profile and supergene enrichment of the residuum probably took place during the mid-Cretaceous-early Tertiary.
ISSN: 0899-5362

hal-01277679
https://hal.archives-ouvertes.fr/hal-01277679
DOI : 10.1016/j.jafrearsci.2015.07.017

Éditeur(s) : HAL CCSD
Résumé : Since its appearance at the beginning of the 2000’s, the Reduction of Emissions from Deforestation and forest Degradation, known as REDD+, has gradually been admitted as an indispensable option for global policies aiming at tackling climate change. Relying on the concept of « avoided deforestation », it requires the formulation of a reference scenario aiming at evaluating efforts made by the countries involved in controlling their level of deforestation. Those scenarios are facing numerous political and scientific debates. This thesis aims at putting into perspective the principles of REDD+, based on a study site covering the Guiana Shield. In a first step, the formulation of a spatialiazed deforestation model over French Guiana will be presented, insisting on the necessity to focus on socio-economic drivers of deforestation. This statement will be reinforced, in a second step, by the the study of deforestation due to gold mining in the Guiana Shield, showing a very strong effect of gold prices and national political contexts on deforestation. These results finally contribute to a critical discussion on REDD+ mechanism, based on the formulation of very variable reference scenarios, relying more on political than on scientific determinants, and potentially enabling the emergence of environmental blackmailing.
Depuis ses balbutiements au début des années 2000, la Réduction des Emissions liées à la Déforestation et la Dégradation forestière, plus connue sous le sigle REDD+, a peu à peu été admise comme un moyen indispensable des politiques globales de lutte contre le changement climatique. Reposant sur le concept de « déforestation évitée », elle nécessite la formulation d’un scénario de référence servant à évaluer les efforts des pays dans la maîtrise de leur niveau de déforestation. Ces scénarios sont au cœur de nombreux débats politiques et scientifiques. Cette thèse constitue une mise en perspective des principes de REDD+ avec, comme cas d’étude, le Plateau des Guyanes. Dans un premier temps, on présentera l’établissement d’un modèle spatialisé de déforestation pour la Guyane française, insistant sur la nécessité de se focaliser sur les moteurs socio-économiques de la déforestation. Ce constat sera renforcé, dans un second temps, par l’étude de la déforestation liée à l’orpaillage à l’échelle de l’ensemble du Plateau des Guyanes, montrant un impact très fort du cours de l’or et des contextes politiques sur le niveau déforestation. Ces résultats alimenteront une discussion critique du mécanisme REDD+, basé sur la formulation de scénarios de référence potentiellement très variables et fondés sur des déterminants davantage politiques que scientifiques, ouvrant ainsi la porte à un potentiel chantage environnemental.
https://tel.archives-ouvertes.fr/tel-01564584

NNT : 2017YANE0005
tel-01564584
https://tel.archives-ouvertes.fr/tel-01564584
https://tel.archives-ouvertes.fr/tel-01564584/document
https://tel.archives-ouvertes.fr/tel-01564584/file/these_dezecache.pdf

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
BackgroundMalaria is endemic in French Guiana, an overseas territory of France on the Guiana Shield. Since 2005, notified malaria cases are decreasing. However, new data show that malaria affects many Brazilian gold miners working illegally in French Guiana, the majority of whom are not counted in official data. In addition, one major concern is the usual practice of improper self-treatment in this mining population, raising fear of the development of antimalarial resistance. This prospective study, conducted in 2015, aimed to estimate the prevalence of Plasmodium spp. in illegal gold miners working in French Guiana. MethodsThe recruitment of gold miners was carried out in resting sites along the French Guiana-Suriname border, where they go for supplies, medical care or leisure. After recording agreement, three malaria diagnostic methods were performed: rapid diagnostic test, microscopy and PCR,ResultsAmong 421 persons recruited in the study, malaria prevalence, detected by nested-PCR, was 22.3% (CI=[18.3-26.3], n=94/421) of which 84% were asymptomatic. ConclusionThis significant malaria reservoir in a mobile and illegal population with difficult access to a health care system raises the threat of artemisinin resistance and puts the population of the Guiana Shield at risk of new transmission foci while countries of the region aim at malaria elimination. Even though French legislation may hamper dealing with this population, France must face the reality of malaria in illegal gold miners in order to meet its commitment to malaria elimination.
ISSN: 1475-2875

hal-01346800
https://hal.archives-ouvertes.fr/hal-01346800
https://hal.archives-ouvertes.fr/hal-01346800/document
https://hal.archives-ouvertes.fr/hal-01346800/file/2016%2C%20Douine%20-%20Prevalence%20of%20Plasmodium%20spp.%20in%20illegal%20gold%20miners%20in%20French%20Guiana%20in%202015.pdf
DOI : 10.1186/s12936-016-1367-6

Éditeur(s) : HAL CCSD Elsevier
Résumé : In the context of an ongoing monitoring study on the impacts of gold-mining activities on critical ecosystem processes, we explored the use of soil Denitrifying Enzyme Activity (DEA) and Substrate Induced Respiration (SIR) as ecosystem indicators in tropical rainforests of French Guiana. We also propose DEA/SIR ratio as ecosystem attribute able to describe the state of an ecosystem and to reflect changes in ecological processes. With this purpose, we measured SIR, DEA and DEA/SIR ratio in five gold-mining areas and five surrounding natural reference rainforests. We also measured indicators in two conditions of spontaneous regeneration of vegetation (stratified or not) and two conditions of soil rehabilitation (prior preparation of soils or not). We showed a high variability of DEA, SIR and DEA/SIR ratio in the natural reference forests. This pointed out the necessity to identify relevant reference systems - i.e. proving a close match in all relevant ecological dimensions - to compare with closed perturbed systems in order to assess the levels of alterations after disturbances. Results showed a high impact of gold mine on microbial processes with a strong decrease of DEA (10-fold lower), SIR (2-fold lower) and DEA/SIR ratio (8-fold lower) in perturbed areas in comparison with natural reference forests. The type of spontaneous vegetation (stratified or not) influenced the values of indicators as well as prior rehabilitation of soils, demonstrating the capacity of DEA. SIR and DEA/SIR ratio to respond in proportion to the perturbation (robustness) and to the different levels of restoration (sensitivity). The systematic decrease of the ratio DEA/SIR observed in the studied perturbed situations demonstrates clearly that the structure of microbial communities has been also modified. The ratio DEA/SIR proved to be robust and sensitive, and able to describe in fairly fine way changes of soil microbial communities in terms of structure and function in gold mine areas and during processes of restoration. We propose to use DEA, SIR and DEA/SIR ratio as bioindicators of both structural and functional aspects of C and N cycling in soils. Together with others bioindicators based on key supporting functions in soils, these indicators should accurately evaluate the ecological potential of natural ecosystems and the levels of degradation in case of land-use changes. (C) 2012 Elsevier Ltd. All rights reserved.
ISSN: 1470-160X

hal-01190730
https://hal.archives-ouvertes.fr/hal-01190730
DOI : 10.1016/j.ecolind.2012.01.021
PRODINRA : 213639

Éditeur(s) : Latin American Collection, George A. Smathers Libraries, University of Florida Department of English, University of Florida Latin American Collection, George A. Smathers Libraries, University of Florida ( Gainesville, FL ) Department of English, University of Florida ( Gainesville, FL )
Résumé : Source: University of Florida Latin American Collection, Gainesville, FL. Resources: Microfilm of The Creole, Port of Spain Gazette, and Royal Gazette of British Guiana

Droits : [cc by-nc-sa] This item is licensed with the Creative Commons Attribution Non-Commercial Share Alike License. This license lets others remix, tweak, and build upon this work non-commercially, as long as they credit the author and license their new creations under the identical terms.
http://ufdc.ufl.edu/AA00016150/00001

Éditeur(s) : HAL CCSD
Résumé :   Diffusion du document : INRA Antilles-Guyane, UMR ECOFOG, F97387 Kourou, Guyane (France) Diplôme : Master Recherche
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
Worldwide, there is concern regarding the declining quality of ecosystems, their rehabilitation, and their protection. In particular, the recognition that soil is a finite resource has spurred efforts to manage and restore it. In French Guiana, gold mining is a serious social and ecological problem, including the threats it poses to soil quality. The principal goal of this study was to establish a qualitative baseline of impacts of gold mining on soil microbial activity at five previously mined sites. We measured the potential rates of respiration and denitrification in disturbed soils, and compared theses rates with those of soils from adjacent forests, which served as un-disturbed references. Microbial activity, used as a bio-indicator, demonstrated the importance of soil rehabilitation, and the type of soil rehabilitation. We also found that visual observations of plant regeneration were insufficient to infer the rate of microbial activity. These bio-indicators can indicate soil quality, and help to formulate hypotheses about its developmnent. Bio-indicators can be used to obtain reliable indications about the quality of soil and contribute to decision-making in the management and restoration of this valuable resource.
Notre étude s'inscrit dans un contexte mondial de préoccupations environnementales, centrées notamment sur l'évaluation de la qualité des écosystèmes, la mise en place de leur réhabilitation et de leur sauvegarde. En particulier, la prise de conscience que le sol ne constitue pas une ressource inépuisable s'est accompagnée de la nécessité de gérer, voire de restaurer cette ressource. L'étude s'intègre également dans un contexte guyanais où l'exploitation aurifère constitue un problème écologique et sociétal majeur. Notre travail a pour but principal de dresser un bilan qualitatif des impacts de l'exploitation aurifère sur le fonctionnement microbien des sols de cinq sites miniers. Pour cela, nous avons effectué les mesures des activités potentielles de deux fonctions microbiennes, la respiration et la dénitrification, sur les sols des sites perturbés. Nous avons comparé ces valeurs d'activités microbiennes avec celles obtenues pour les sols de forêts naturelles (adjacentes à ces sites) que nous avons considérées comme la référence à atteindre (témoin). Les fonctions microbiennes, utilisées comme bio-indicateurs, ont mis en évidence l'importance de la réhabilitation et du type de réhabilitation sur la reprise du fonctionnement du sol. Nous avons constaté que l'observation de visu de la végétation ne suffit pas à évaluer de façon certaine la reprise de ce fonctionnement. Ces bio-indicateurs sont aptes à traduire l'état d'un sol perturbé et émettre des hypothèses quant à son évolution. Ainsi, les bio-indicateurs peuvent être utilisés afin d'obtenir des indications solides sur la qualité des sols et aider à la prise de décision en matière de gestion et de restauration de cette ressource.
https://hal.archives-ouvertes.fr/hal-01189544

hal-01189544
https://hal.archives-ouvertes.fr/hal-01189544
PRODINRA : 46710

Éditeur(s) : Elsevier
Résumé : The accumulation of nine heavy metals in fine-grained sediments from the mangrove fringed coast of French Guiana is evaluated. The dynamic features of the South American tropical coastline, from the Amazon to the Orinoco Rivers, result in mangrove sediments being alternately submitted to phases of erosion and net sedimentation a few tens of years long. This process influences the distribution of the heavy metals associated with these frequently re-mobilized deposits. Sedimentary cores and mangrove plant samples were collected, at different seasons, in various swamps characterized by different properties (content of sedimentary organic matter, distance from sea water and fresh water). The ranges of measured concentrations expressed in mu mol g(-1) were the following: Cu (0.06 to 0.61), Co (0.12 to 0.68), Pb (0.08 to 0.18), Ni (0.32 to 0.76), Cr (0.61 to 1.40), Zn (1.25 to 5.94), Mn (4.36 to 45.4) and Fe (441 to 1128). No differences were found between sediments from mangroves developing upstream and downstream of urban areas, i.e. Cayenne and Kourou. This suggests that the content of mangrove sediments in heavy metals along the coastline of French Guiana is essentially the result of the continuous alternation of accumulation and transport phases occurring upstream after departing from the Amazon watershed. The sources of this heavy metals content are thus difficult to identify. However it is well known that the alluvium produced by the natural erosion of the Amazonian soils is naturally enriched in mercury. Also, the run-off from gold mining activities is known to contribute to mercury pollution. Ranges in total Hg were between 0.15 and 2.57 nmol g(-1), with mean values close to 0.41 nmol g(-1), and were clearly correlated with total organic carbon except for some outstanding high values, which may be a result of rapid geochemical changes. Heavy metal concentrations showed variations with depth. The redox conditions and the decay processes affecting the organic matter control the cycling of iron and manganese, which in turn control the concentrations and associations of heavy metals. These preliminary results suggest that the variations in heavy metal content with depth or between mangrove areas result largely from diagenetic processes rather than changes in metal input resulting from local human activities. (c) 2005 Elsevier B.V. All rights reserved.
Marine Chemistry (0304-4203) (Elsevier), 2006 , Vol. 98 , N. 1 , P. 1-17

Droits : 2005 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/2006/publication-1041.pdf
DOI:10.1016/j.marchem.2005.06.001
http://archimer.ifremer.fr/doc/00000/1041/

Éditeur(s) : EDP Sciences
Résumé : We present results obtained from a pristine site of French Guiana (South America), at the Pic Matecho, a region far from gold mining activity. This area contains a small permanent lake, a rare situation in French Guiana. Tree canopy, soils and Lake Matecho sediments were analysed in total Hg and Pb-210. The annual deposit of litterfall is estimated at 40 mug (Hg)/m(2)/y. The top sediment content of 0.2 mug (Hg)/g indicates a large contribution of the atmospheric deposit. In sediment, the decrease of total Hg with depth is neither due to local human influence, nor to increase of atmospheric background during this century. It is attributed to remineralization of organic matter in the upper part of the sediment : the majority of the total Hg deposited at the water/sediment interface is not permanently trapped in the sediment but remobilized in water. Interpretation of the historical sediment profile suggests a constant deposit rate over the last millennium.
Journal De Physique Iv (1155-4339) (EDP Sciences), 2003-05 , Vol. 107 , P. 859-862

Droits : 2003 EDP Sciences
http://archimer.ifremer.fr/doc/00000/10630/9348.pdf
DOI:10.1051/jp4:20030433
http://archimer.ifremer.fr/doc/00000/10630/

Éditeur(s) : HAL CCSD
Résumé :   Diplôme : DEA
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
As part of a programme of degraded soils rehabilitation, and in order to follow the biological processes connected with the soils reconstitution, it is a requisite to determine indicators able to account for the evolution of the soil. These indicators can he found on structural and/or functional characteristics of the bacterial communities, such as soil respiration, denitrification or genetic diversity. Theses descriptors are able to characterize the global community or targeted communities chosen for their importance in the ecosystem functioning. In this work, we tried to know whether soil bacteria genetic diversity was able to be a relevant indicator of the soil evolution in a rehabilitated sequence. This diversity is apprehended via a molecular technique: ARISA. A chronosequence situated on a gold mine, already experimented as part of a programme of degraded zones rehabilitation, was at our disposal. Results show that ARISA is a very sensitive technique, able to account for the bacterial community heterogeneity in a soil but unable, at the parcel scale, to discriminate the treatments nor to account for the evolution in lime of planted treatments. Lastly, the advantage of this indicator of genetic diversity may arise from its confrontation to other indicators (functional, for example).
Dans le cadre de la revégétalisation d'un sol dégradé et afin de pouvoir suivre les processus biologiques liés à la reconstitution des sols, il est nécessaire de déterminer des indicateurs pouvant rendre compte de l'évolution de l'état du sol. Ces indicateurs peuvent être fondés sur des caractéristiques fonctionnelles et/ou structurales des communautés bactériennes telles que la respiration, la dénitrification ou la diversité génétique. Ces descripteurs peuvent analyser la communauté globale ou des communautés cibles choisies pour leur importance dans le fonctionnement de l'écosystème. L'objectif de ce stage était de savoir si la diversité génétique des bactéries du sol pouvait être un indicateur de l'évolution des sols au sein d'une séquence de revégétalisation. Cette diversité est appréhendée par une technique de biologie moléculaire : l'ARISA. On dispose d'une chronoséquence située sur une mine d'or étudiée dans le cadre d'un programme de réhabilitation des zones dégradées. Les résultats montrent que l'ARISA est une technique très sensible, qui rend bien compte de l’hétérogénéité des communautés bactériennes présentes dans un sol mais est incapable, à l’échelle de la parcelle, de discriminer ni les traitements ni de rendre compte de l'évolution dans le temps de ces parcelles. Enfin, l'intérêt de cet indicateur de diversité génétique pourra résulter de sa confrontation avec d'autres indicateurs (fonctionnels par exemple).
https://hal.archives-ouvertes.fr/hal-01189155

hal-01189155
https://hal.archives-ouvertes.fr/hal-01189155
PRODINRA : 9464

Éditeur(s) : HAL CCSD Elsevier
Résumé :  
Microbial-based indicators, such as C and N contents or microbial functions involved in C and N cycles, are currently used to describe the status of soils in disturbed areas. Microbial functions are more accurate indicators but their measurement for studies at the ecosystem level remains problematical because of the huge spatial variability of these processes and, consequently, of the large number of soil samples which must be analyzed. Our goal was to test the capacity of near-infrared reflectance spectroscopy (NIRS) to predict respiration and denitrification but also carbon and nitrogen contents of soils submitted to various procedures of restoration. To achieve this objective, we took advantage of an experiment conducted on a reforestation system established after open-cast gold mining in French Guiana. In this experimental station, plantations of various ages and various soil textures were at our disposal. Our results showed that both plantations and soil texture had a strong impact on the recovery of soil functioning: carbon and nitrogen contents, respiration and denitrification increased with age of plantation and clay content. Calibrations were performed between spectral data and microbial-based indicators using partial least squares regression (PLS). The results showed that C and N contents were accurately predicted. Microbial functions were less precisely predicted with results more accurate on clayey soils than on sandy soils. In clayey soils, perturbed or restored soils and the year of plantation were discriminated very efficiently through principal component analyses of spectral signatures (over 80% of variance explained on the first two axes). Near-infrared spectroscopy may thus be extended to the prediction of functional soil parameters, but the capacity of this method must be strengthened by expending the databases with other soils in other contexts. The possibility of using NIRS provides many opportunities for understanding both the temporal dynamics and the spatial variability of the recovery of key microbial functions during soil restoration.
ISSN: 0929-1393

hal-01032188
https://hal.archives-ouvertes.fr/hal-01032188
DOI : 10.1016/j.apsoil.2007.07.001