Erosion mécanique des sols et transferts géochimiques dans le bassin Adour-Garonne

L’érosion hydrique des sols résulte de processus naturels modifiés par la pression anthropique et contribue aux transferts de matières en suspension (MES) entre le continent et l’océan ainsi que du carbone organique (CO) et des éléments traces métalliques (ETM) associés. Sur la base d’une banque de données haute résolution temporelle (horaire à journalier et couverture pluriannuelle) de concentrations en MES et de débits sur des rivières contrastées du bassin Adour-Garonne, nous définissons par simulation numérique des fréquences d’échantillonnage adaptées à la typologie des bassins et les incertitudes associées. Des approches alternatives utilisant des relations MES-débit permettent de modéliser les flux annuels en MES. De plus, l’ajustement des régressions statistiques de type MES=aQ^b reflète les typologies avec une correspondance directe entre les coefficients et l’indice de sensibilité à l’érosion. Les taux d’érosion des bassins représentatifs du système Adour- Garonne montrent une large gamme comprise entre 5 et 180 t.km^-2.an^-1 et une forte variabilité interannuelle. L’étude à haute résolution des transferts de la Nivelle (représentative des petites rivières montagneuses pyrénéennes et cantabriques) a permis de quantifier précisément le flux spécifique annuel de CO particulaire (5,3 t.km^-2.an^-1), provenant pour 55% du sol, 40% de la litière et 5% de la production autochtone et de montrer la forte contribution de ces petits systèmes (70% des apports totaux) aux apports dans le Golfe de Gascogne. De même, le Congo (Zaïre), système diamétralement opposé, montre de fortes variabilités saisonnières des concentrations en CO en fonction de l’hydrologie. L’essentiel des transferts se font sous forme dissoute (>75%), en raison des faibles taux d’érosion (~9 t.km^-2.an^-1) contrairement à ceux des petites rivières montagneuses (~75 t.km^-2.an^-1). Les rapports élémentaires (As/Th, Cd/Th, Zn/Cd) établis lors de la crue cinquantennale du Lot échantillonnée à très haute résolution sont utilisés pour différencier et quantifier les zones sources de MES (235 000 t du Lot amont, 185 000 t de la remobilisation des barrages, 8000 t par le Riou Mort). Les variations temporelles en ETM reflètent la succession de dominance de source de l’aval vers l’amont et permettent de proposer une nouvelle explication de la baisse du coefficient de partition (Kd) avec des concentrations en MES croissantes (phénomène pce). Le suivi haute résolution spatiale et temporelle durant une année d’un bassin expérimental hétérogène fortement anthropisé (Decazeville) couvrant une large gamme de conditions hydrologiques (étiage prononcé – crue centennale) a démontré des différences spatiales des taux d’érosion. Des signatures géochimiques sont utilisées pour comprendre le fonctionnement hydrologique du bassin versant permettant d’interpréter les variations temporelles en ETM dissous et particulaires. Une source additionnelle souterraine est localisée contribuant à 60% et 38% du bilan annuel de Cd dissous et particulaire du Riou Mort. L’établissement du bruit de fond géochimique du bassin de Decazeville suggère que 93% et 99% des apports annuels en Zn et Cd sont d’origine anthropique.Soil erosion due to natural and anthropogenic processes controls transport of suspended particulate matter (SPM), organic carbon (OC) and associated trace elements from continent to ocean. We define sampling frequencies adapted to watershed typology and related uncertainties by using numerical simulation based on a long-term high resolution database on SPM concentrations and water discharge (Q). Alternative approaches using mathematical relations between SPM concentrations and discharge aim to develop models for annual SPM flux estimates. Moreover, statistical relations (type SPM=aQ^b) reflect watershed properties attributing distinct a and b coefficients to lithology and soil erosion sensitivity index. Representative watersheds of the Adour- Garonne River system cover a large range of annual SPM yields (5 to 180 t.km^-2.yr^-1) and show high interannual variability. High resolution data on particulate OC in the Nivelle River, a typical Pyrenean mountainous watershed, indicates high specific annual POC yields (5.3 t.km^-2.yr^-1), attributed to soil (55%), litter (40%) and autochthonous production (5%), highlighting the important contribution (70%) of small river systems to OC export into the Bay of Biscay. Despite of strongly contrasted properties, compared to the small Pyrenean rivers, also the Congo River shows seasonal OC variations related to hydrology. However, OC is essentially exported in the dissolved phase (>75%) due to the flat relief and very low SPM yields (~9 t.km^-2.yr^-1) compared to mountainous rivers (~75 t.km^-2.yr^-1). High resolution sampling during a major regional flood event in the Lot River provides geochemical signatures (e.g. As/Th, Cd/Th, Zn/Cd) for SPM, attributed to successive dominance of water masses transporting material from different sources (~235,000 t from the upstream Lot River, ~185,000 t from remobilisation of riverbed sediments and ~8,000 t from the Riou Mort River). Decreasing partition coefficients (Kd) with increasing SPM concentrations during the flood (particle concentration effectpce) are attributed to source-related variations rather than colloidal influence or changed grain size composition of SPM, suggesting a third possible explanation for the commonly observed pce. The high resolution observation network in the heterogeneous experimental Riou Mort watershed reveals important spatial and temporal variability of erosion during contrasted hydrological situations. Moreover, we identify an additional yet unknown underground point source contributing 60% and 38% to annual dissolved and particulate Cd fluxes, respectively. The determination of natural background values of heavy metal in the Riou Mort watershed suggests 93% and 99% of annual particulate Zn (73 t) and Cd (2,4 t) fluxes are of anthropogenic origin

KẾT QUẢ BƯỚC ĐẦU VỀ HÀM LƯỢNG CÁC KIM LOẠI NẶNG TRONG NƯỚC SÔNG HỒNG TẠI TRẠM THỦY VĂN SƠN TÂY

This study  is  based  on the  experimental  results  obtained  from  analysis  of suspended  and  dissolved  heavy  metal concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Pb and Th) in the Red River at the SonTay station during 2011. The results showed that for the dissolved phase, heavy metal concentrations were relatively stable, whatever the water discharges.  In  contrast,  the  concentration  of  suspended  heavy  metals  tended  to  decrease  with  increasing  of  water discharge. Moreover, the results indicated also that the transfert of heavy metals by the Red River was mainly in the suspended phase (up to 99 %). If the water quality of the Red River can be classified as good (column A - QCVN08: 2008/BTNMT) in term of dissolved heavy metal concentrations; the suspended heavy metal concentrations were higher than  the  ecological  indicators  PEC  (Probable  Effect  Concentration),  suggesting  the  effect  of  this  heavy  metal contamination on the ecology and environment in the Red River basin is extremely high (over 50% ). Finally, this study estimated the contribution of the Red River on the global flux from 0.1 to 0.4% for dissolved phase and from 0.4% to 2.2  for suspended phase.ReferencesBerg M., Stengel C., Trang P.T.K., Pham H.V., Sampton M.L., and Leng M., 2007. Magnitude of arsenic pollution in the Mékong and Red River Deltas-Cambodia and Vietnam, Science of the Total Environment 327, 413-425. Blake, W.H., Walsh, R.P.D., Barnsley, M.J., Palmer, G., Dyrynda, P., James, J.G., 2003. Heavy metal concentrations during storm events in a rehabilitated catchment. Hydrol. Process. 17, 1923-1939. Cenci R.M., and Martin J.M., 2004. Concentration and fate of trace metals in Mekong River Delta. Science of the total Environment 332, 167-182. Coynel A., Schafer J., Blanc G., and Bossy C., 2007. Scenario of particulate trace metal and metalloid transport during a major flood event inferred from transient geochemical signals. Applied Geochemistry 22, 821-836. Coynel A., Blanc G., Marache A., Schäfer J., Dabrin A., Maneux E., Bossy C., Masson M., and Lavaux J. 2009. Assessment of metal contamination in a small mining- and smelting-affected watershed: high resolution monitoring coupled with spatial analysis by GIS, J Environ Monit. 11, 962-976. Dang T.H., Coynel A., Orange D., Blanc G., Etcheber H., and Le L.A., 2010. Long-term monitoring (1960-2008) of the river-sediment transport in the Red River Watershed (Vietnam): temporal variability and dam-reservoir impact, Science of the Total Environment 408, 4654-4664. Dang T.H., Coynel A., 2013. Assessment of arsenic contamination in the Red River: high resolution monitoring coupled with spatial analysis by GIS. Journal of Sciences and Technology, 51, 779-788. Eiche E., Neumann T., Berg M., Weinman B., van Geen A., Norra S., Berner Z., Stüben, D., 2008. Geochemical processes underlying a sharp contrast in groundwater arsenic concentrations in a village on the Red River delta, Vietnam. Applied Geochemistry 23, 3143-3154. Horowitz A.J., Meybeck M., Idlafkih Z., and Biger E., 1999. Variations in trace element geochemistry in the Seine River Basin based on floodplain deposits and bed sediments, Hydrological Processes 13, 1329-1340. Horowitz AJ, Elrick KA, Smith JJ., 2001. Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins. Hydrolog Process 15, 1169-1207. Huang X., Sillanpa M., Duo B. and Gjessing ET., 2008. Water quality in the Tibetan Plateau: Metal contents of four selected rivers. Environmental Pollution 156, 270-277. MacDonald DD., CG. Ingersoll, TA. Berger., 2000. Development and Evaluation of Consensus-Based Sediment Quality Guidelines for Freshwater Ecosystems. Arch. Environ. Contam. Toxicol. 39, 20-31. Masson M., 2007. Sources et transferts métalliques dans le basin versant de la Gironde-Réactivité et mécanismes géochimiques dans l’estuaire fluvial de la Gironde. Thèse doctorat de l’Université Bordeaux 1, 344 pp. Meybeck M., 1998. Man and river interface multiple impacts on water and particulates chemistry illustrated in the Seine River Basin, Hydrobiologia 373, 1-20. Osman, A.E. and Maha, A.A., 2005. Contribution of some trace elements from an Egyptian huge drain to the Mediterranean sea, west of Alexandria. Egypetian journal of aquatic research 31, 120-129. Schäfer J. , G. Blanc, S. Audry, D. Cossa C. Bossy., 2006. Mercury in the Lot-Garonne River system (France): Sources, fluxes and anthropogenic component. Applied Geochemistry 21, 515-527. Singh P., 2010. Geochemistry and provenance of stream sediments of the Ganga River and its major tributaries in the Himalayan region, India. Chemical Geology 269, 220-236. Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford, 312 pp. Viers J., Dupréa B., and Gaillardet J., 2009. Chemical composition of suspended sediments in World Rivers:  New insights from a new database. Science of the total environment 407, 853-868. Zhang J., W.W. Huang, R. Letolle, C. Jusserand, 1995. Major element chemistry of the Huanghe (Yellow River), China - weathering processes and chemical fluxes. Journal of Hydrology 168, 173-203. This study  is  based  on the  experimental  results  obtained  from  analysis  of suspended  and  dissolved  heavy  metal concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Pb and Th) in the Red River at the SonTay station during 2011. The results showed that for the dissolved phase, heavy metal concentrations were relatively stable, whatever the water discharges.  In  contrast,  the  concentration  of  suspended  heavy  metals  tended  to  decrease  with  increasing  of  water discharge. Moreover, the results indicated also that the transfert of heavy metals by the Red River was mainly in the suspended phase (up to 99 %). If the water quality of the Red River can be classified as good (column A - QCVN08: 2008/BTNMT) in term of dissolved heavy metal concentrations; the suspended heavy metal concentrations were higher than  the  ecological  indicators  PEC  (Probable  Effect  Concentration),  suggesting  the  effect  of  this  heavy  metal contamination on the ecology and environment in the Red River basin is extremely high (over 50% ). Finally, this study estimated the contribution of the Red River on the global flux from 0.1 to 0.4% for dissolved phase and from 0.4% to 2.2  for suspended phase

A method to calculate sediment fluxes from infrequent data: application to 65 rivers of the French river quality database

International audienceImproving knowledge of sediment exports represents one major challenge for environmental sciences considering their role in geochemical cycles and their link with Earth's surface processes. Because suspended sediment (SS) fluxes in rivers reflect the integration of combined erosion, transport and deposition processes that occur within the drained area, their calculation is thus essential in surface processes studies. Suspended sediment fluxes are estimated from discharge measurements and SS concentrations, either by averaging methods or by predicting sediment concentration values from continuous discharge data. In the latter case, a power function (or power law relation) is often defined between the observed SS concentrations and the corresponding discharge data. However it seems unrealistic to consider a single relation between SS concentrations and river discharges. The reason is hat sediment production processes are not homogeneous in time, showing local and seasonal effects for example in agricultural areas where land cover varies inside a year or in mountainous regions where snow melting has a strong influence. Moreover, these processes are also spatially heterogeneous, due to spatial patterns in landscape characteristics, meteorological phenomena and geomorphology. In addition, important gaps persist when calculating SS fluxes, mainly due to SS measurements are not always carried out with high frequency. Based on 65 river basins in France, with various sizes, geomorphologies and land uses, this study aims at testing methods for an estimation of annual sediment loads, based on infrequent SPM concentration data spanning over several decades

Relations entre qualité du substrat, flux de matières et activités humaines. Connaissance pour la gestion des ressources en eau de la Région Aquitaine

Les résultats de ce travail de recherche, confirment une fois de plus l'absence de déterminisme apparent entre qualité du substrat et occupation des sols. Ils montrent qu'il n'y a pas de variables prépondérantes ou explicatives de facteurs sociaux ou physiques qui soient responsables des variations affectant les milieux étudiés. Cependant, les analyses régressives des rapports entre homme et milieu montrent les liens étroits entre habitat et types de sol. L'action humaine a des effets sur la couverture végétale, sur les sols et sur l'hydraulique qui avec le climat et la topographie constituent les principaux facteurs d'érosion

Science of The Total Environment

Tailings containing mining and ore treatment waste, accumulated over long time periods are major contaminant sources at the watershed scale and may seriously impair environmental quality of river-sea continuums. A critical review of existing work in different disciplines addressing the multi-metal contamination of the Gironde Watershed, a major fluvial-estuarine model system representative of many other systems worldwide, has provided a condensed, yet pertinent overview on various aspects of this environmental problem. Combining long-term observation and contamination records from different environmental archives, there is a clear trend towards resilience for the main historical contaminants (Cd, Zn, Pb and Cu), yet suggesting that resilience needs appropriate management of both, tailings as the initial source and contaminated sediments acting as temporary metal traps which may transform into delayed sources. Contaminated sediment management is an increasingly important challenge due to (i) successful remediation at the contamination source itself (ii) global-change induced factors and strategies and (iii) lacking coordination of actions between upstream and downstream parts of the fluvial-estuarine continuum. Less studied and emerging metallic contaminants show recent trends in sediments and biota that are decoupled from the legacy contaminant trajectories due to recent sources and applications, suggesting that further work is needed to assess their potential impact on the environmental quality of the Gironde fluvial-estuarine system and that of other systems, especially in a context of worldwide rapidly growing mining activity and metal use

Erosion mécanique des sols et transferts géochimiques dans le bassin Adour-Garonne

L'érosion hydrique des sols résulte de processus naturels modifiés par la pression anthropique et contribue aux transferts de matières en suspension (MES) entre le continent et l'océan ainsi que du carbone organique (CO) et des éléments traces métalliques (ETM) associés. Sur la base de données à haute résolution temporelle de MES et débits sur des rivières contrastées du bassin Adour-Garonne, nous définissons par simulation numérique des fréquences d'échantillonnage adaptées à la typologie des bassins et les incertitudes associées. Des approches alternatives utilisant des relations MES-débit permettent de modéliser les flux annuels en MES. L'étude à haute résolution des transferts d'une petite rivière montagneuses pyrénéennes a permis de quantifier le flux spécifique annuel de COP provenant pour 55% du sol, 40% de la litière et 5% de la production autochtone et de montrer la forte contribution de ces systèmes aux apports dans le Golfe de Gascogne. Le Congo, système diamétralement opposé, montre de fortes variabilités saisonnières des concentrations en CO en fonction de l'hydrologie. L'essentiel des transferts se font sous forme dissoute en raison des faibles taux d'érosion contrairement à ceux des rivières montagneuses. Les rapports élémentaires métalliques établis lors d'une crue cinquantennale du Lot permettent de différencier et quantifier les zones sources de MES. Le suivi d'un bassin expérimental fortement anthropisé (Decazeville) a démontré des différences spatiales des taux d'érosion. Des signatures géochimiques sont utilisées pour comprendre le fonctionnement hydrologique du bassin versant permettant d'interpréter les variations temporelles en ETM dissous et particulaires. Une source additionnelle souterraine est localisée contribuant à 60% et 38% du bilan annuel de Cd dissous et particulaire du Riou Mort. L'établissement du bruit de fond géochimique du bassin de Decazeville suggère que 93% et 99% des apports annuels en Zn et Cd sont d'origine anthropique.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Détermination des zones de dépôt- Erosion des sédiments cohésifs à l’aide d’un modèle de transports 2DH – Application à l’estuaire de la Nivelle

Deposition / Erosion area definition through 2DH cohesive sediment transport model – Application to the Nivelle Estuary, France. Silting process management is an important issue for estuarian port management. St Jean de Luz – Ciboure Port, located at the mouth of the Nivelle River is submitted to silting process accelaration since 2002. Comparison between 1994-2002 and 2002-2007 periods shows a 48% increse of the annual equivalent dredging volume. This silting process acceleration leads to dredging cost rise. The Nivelle Project, funded by the Conseil Général of Pyrénées Atlantiques, in charge of St Jean de Luz – Ciboure port management, aims to improve the understanding of port silting acceleration process. This article introduces the results from a 2DH sediment transport model using MOHID (www. mohid. com). The hydrodynamic model has been calibrated with ADCP measurements. The transport model is forced with real 2002 summer conditions. Tidal scale results show alternated upward and downward sediment transport, intersected by potential deposition during slack water phases. The estimated annual sedimentary budget for low water conditions is insignificant compared to the annual equivalent dredging volume for the 2002-2007 period. This corroborates the following hypothesis : floods have a huge influence of on the sedimentary budget.La gestion des processus d’envasement est un enjeu d’importance pour l'exploitation des ports estuariens. Le port de St Jean de Luz – Ciboure situé à l’embouchure de la Nivelle connaît une accélération des processus d’envasement depuis 2002. La comparaison des périodes 2002-2007 et 1994-2002 montre une croissance de 48% des volumes de dragage annuels équivalents. Cette accélération des processus d’envasement entraîne une hausse des coûts de dragage. L’objectif du Projet Nivelle financé par le Conseil Général des Pyrénées Atlantiques, en charge de la gestion du port, est d’améliorer la compréhension des processus de dépôt sédimentaire. Cet article présente les résultats d''un modèle numérique 2DH de transport sédimentaire développé sous MOHID (www.mohid.com). Le modèle hydrodynamique a été calibré à l'aide d'une campagne de mesures ADCP. Le modèle de transport a été forcé dans les conditions réelles de l'été 2002. Les résultats obtenus à l'échelle de la marée montrent l'existence d'une alternance de phases de transport vers l'amont et vers l'aval, entrecoupés de phases de dépôts potentiels aux étals. L’estimation du budget sédimentaire annuel pour des conditions d’étiage est positif, mais son ordre de grandeur reste négligeable devant les volumes de dragage annuels équivalents pour la période 2002-2007. Ceci corrobore l’hypothèse d’une forte influence des périodes de crues sur le budget sédimentaire.Doré Raphaëlle, Maron Philippe, Coynel Alexandra. Détermination des zones de dépôt- Erosion des sédiments cohésifs à l’aide d’un modèle de transports 2DH – Application à l’estuaire de la Nivelle. In: 31èmes Journées de l’Hydraulique de la Société Hydrotechnique de France. Morphodynamique et gestion des sédiments dans les estuaires, les baies et les deltas. 22 et 23 SEPTEMBRE 2009. 2009

Mercury contamination in the Red river watershed: a review of the contaminated sites

This study is based on two sampling campaigns covering the whole Vietnamese Red River watershed in 40 sites at low and high water levels during 2009 in order to determine the seasonal and spatial variations of Hg concentrations in stream sediments. The results showed that the Hg concentrations during low water level were clearly higher than that during high water level, demonstrating an effect of particle (grain) size (i.e. significant contribution of less mercury-contaminated particles in high water level). In addition, in order to assess spatial distribution of the Hg contamination in the Red River watershed and localize geochemical anomalies, multidimensional statistical analyses combined with Hg maps generated by GIS tool were used. We observed that the high mercury anomalies are originated from the important pollutant sources (mining/smelting) located in the upstream and mid- Red River watershed, demonstrating an impact of anthropogenic activities on river Hg concentrations. Finally, the comparison between the Hg concentrations in the stream sediment from the Red River watershed and the consensus-based freshwater sediment quality guidelines (SQGs) indicated that the sediment quality for important areas of the Red River watershed is rather poor and probably represents serious threats to aquatic life.References Adrienne, R.F., Peter, V.H., Brian, C.H., 2008: Spatial and seasonal patterns of mercury concentrations in fish from the St. Lawrence River at Cornwall, Ontario: Implications for monitoring. Journal of Great Lakes Research 34, 72-85. Balogh, S., Meyer M., Kentjohnson, D., 1998: Transport of mercury in three contrasting river basins. Environ. Sci. Technol.32, 456-462. Berg, M., Stengel, C., Phạm, T.K.T., Pham, H.V., Sampton, M.L., Leng, M., 2007: Magnitude of arsenic pollution in the Mékong and Red River Deltas-Cambodia and Vietnam, Science of the Total Environment 327, 413-425. Brigham, M., Wentz, D., Aiken, G., Krabbenhoft, A., 2009: Mercury cycling in stream ecosystems.1. Water column chemistry and transport. Environ. Sci. Technol. 43, 2720-2725. Coynel, A., Blanc, G., Marache, A., Schäfer, J., Dabrin, A., Maneux, E., Bossy, C., Masson, M., Lavaux, J., 2009: Assessment of metal contamination in a small mining- and smelting-affected watershed: high resolution monitoring coupled with spatial analysis by GIS, J Environ Monit.11, 962-976. Dang, T.H., Coynel, A., Grosbois, C., Blanc, G., Orange, D., Etcheber, H., Le, L.A., 2011: Distribution, source and flux of arsenic in a typical humid tropics river originating from the Himalaya Mountains: the Red River watershed (China/Vietnam). Proceeding of 23eme RST conference, Bordeaux, France. Dang, T.H., Coynel, A., Orange, D., Blanc, G., Etcheber, H., Le, L.A., 2010: Long-term monitoring (1960-2008) of the river-sediment transport in the Red River Watershed (Vietnam): temporal variability and dam-reservoir impact. Science of the Total Environment 408, 4654-4664. Guangle, Q., Xinbin, F., Shaofeng, W., Tangfu, X., 2006: Mercury contaminations from historic mining to water, soil and vegetation in Lanmuchang, Guizhou, southwestern China. Science of the Total Environment 368, 56-68. Ho, T.L.T., Cao, T.S., Tran, T.L., Kurosawa, K., Egashira, K., 2010: Assessment of surface and groundwater quality in pig-raising villages of Hai Duong province in Vietnam. Journal of the Faculty of Agriculture, Kyushu University 55, 123-130. Le, T.P.Q., Garnier, J., Gilles, B., Sylvain, T., Chau, V.M., 2007: The changing flow regime and sediment load of the Red River, Viet Nam. Journal of Hydrology 334, 199-214. MacDonald, D.D., Ingersoll, C.G., Berger, T. A., 2000: Development and Evaluation of Consensus-Based Sediment Quality Guidelines for Freshwater Ecosystems. Arch. Environ. Contam.Toxicol.39, 20-31. MacFarlane, M., 2004: Mercury concentrations in water and sediment in Resurrection Creek, Alaska.Final Report, 27p. Maria, H.D.P., Milton, L.L.F., Elba, C.T., 1997: Heavy metals in stream sediments from copper and gold mining areas in southern Brazil. Journal of Geochemical Exploration 58, 133-143. Mlayah, A., Ferreira da Silva, E., Rocha, F., Ben Hamza, Ch., Charef, A., Noronha, F., 2009: The OuedMellègue: Mining activity, stream sediments and dispersion of base metals in natural environments, North-western Tunisia. Journal of Geochemical Exploration 102, 27-36. Nguyen, M.P., Kang, Y., Sakurai, K., Iwasaki, K., Chu, N.K., Nguyen, V.N., Le, T.S., 2010: Levels and Chemical Forms of Heavy Metals in Soils from Red River Delta, Vietnam. Water, Air, and Soil Pollution 207, 319-332. Schäfer, J., Blanc, G., Audry, S., Cossa, D.,  Bossy, C., 2006: Mercury in the Lot-Garonne River system (France): Sources, fluxes and anthropogenic component. Applied Geochemistry 21, 515-527. Spadini, L., Charlet, L., 2003: Distribution of anthropogenic mercury in French Guyana river sediments downstream from gold mining sites. Journal of Physical IV France 107, 1263-1266. Subramanian, V., Madhavan, N., Rajinder, S., Lundin, L.C., 2003: Nature of distribution of mercury in the sediments of the River Yamuna (tributary of the Ganges), India. J. Environ. Monit.5, 427-. Viers, J., Dupréa, B., Gaillardet, J., 2008: Chemical composition of suspended sediments in World Rivers:  New insights from a new database. doi:10.1016/j.scitotenv.2008.09.053.

European fluxes of medical gadolinium to the ocean: A model based on healthcare databases

Marine ecosystems are exposed to a multitude of stresses, including emerging metals as Rare Earth Elements. The management of these emerging contaminants represents a significant environmental issue. For the past three decades, the increasing medical use of gadolinium-based contrast agents (GBCAs) has contributed to their widespread dispersion in hydrosystems, raising concerns for ocean conservation. In order to control GBCA contamination pathways, a better understanding of the cycle of these elements is needed, based on the reliable characterization of fluxes from watersheds.Our study proposes an unprecedented annual flux model for anthropogenic gadolinium (Gdanth) based on GBCA consumption, demographics and medical uses. This model enabled the mapping of Gdanth fluxes for 48 European countries. The results show that 43 % of Gdanth is exported to the Atlantic Ocean, 24 % to the Black Sea, 23 % to the Mediterranean Sea and 9 % to the Baltic Sea. Together, Germany, France and Italy contribute 40 % of Europe’s annual flux. Our study was therefore able to identify the current and future major contributors to Gdanth flux in Europe and identify abrupt changes related to the COVID-19 pandemic