Monitoring and flux determination of trace metals in rivers of the Seversky Donets basin (Ukraine) using DGT passive samplers

International audienceThis paper reports the results of the in situ application of diffusive gradients in thin-films (DGT) passive samplers for trace metals (Cd, Co, Cr, Cu, Ni, Pb and Zn) monitoring in transboundary Udy and Lopan rivers of the Seversky Donets watershed in the Kharkiv region (Ukraine), which has a long history of industrial development. The research discusses potential sources of DGT-measured labile metals in water and seasonal variations. Our results demonstrate the application of DGT for identifying and measuring labile metal concentrations in contrasted climate conditions (cold snowy winter and hot summer) and appropriateness of such a tool for continuous water monitoring with the presence of an ice cover. Results show that DGT-measured concentrations of most of trace metals were much higher downstream of the wastewater treatment plants discharges than upstream; thus wastewater treatment plants seemed not able to reduce or to remove trace metals' contaminations and become major sources of pollutants in the studied rivers. The calculation of the average metal fluxes based on the DGT-measured concentrations confirmed that the urban wastewater discharges significantly contribute to the metal fluxes into the Udy and the Lopan rivers during both low-flow and high-flow periods. Compared to the wastewaters inputs to the rivers, the transboundary effect is limited, but should be taken into account as the origin of some metals is from sources located on the adjacent Russian territory

Water reservoirs, irrigation and sedimentation in Central Asia: a first-cut assessment for Uzbekistan

International audienceWater reservoirs play an important role in areas with limited and erratic precipitation where water is stored and re-distributed later for different purposes. Irrigation is primarily a major water consumer in arid countries of Central Asia for the economic development, employment and food security of the region. The major rivers of Central Asia (e.g., Amu Darya, Syr Darya, and Zerafshan) are turbid watercourses. Sedimentation reduces the main reservoir asset i.e., its volume capacity. In addition, vast territories of the region's countries have been transformed for agriculture to grow water intensive crops such as cotton, rice and wheat during the Soviet Union that dramatically accelerated soil erosion by water and wind. Thus, many man-made water reservoirs are affected by high sedimentation rates. Moreover, uneven spatial and temporal water resources and a Soviet-inherited unified hydraulic infrastructure have raised transboundary reservoir management issues over water resources allocation among the countries in the region such as Kyrgyzstan, Tajikistan, Kazakhstan, Uzbekistan and Turkmenistan. The rivers such as Syr Darya and Amu Darya are already regulated by more than 78 and 94 %, respectively and attempts for new reservoir projects upstream raises increased concerns of the downstream countries (e.g., the Rogun hydropower station in Tajikistan and the Toktogul reservoir in Kyrgyzstan). For instance, the uncoordinated use of reservoirs has caused the Arnasai lake problem in Uzbekistan with environmental, material damage and social unrest. The aim of this paper is first to review the present conditions and the role of man-made water reservoirs for irrigation in Central Asia with special focus on Uzbekistan, second to document past and current reservoir sedimentation conditions in Uzbekistan and third to discuss research carried out by Soviet and present-time local research community in the domain of erosion and sedimentation in the region

Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

International audienceThis study aims at establishing groundwater residence times, identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression. A multi-tracer approach (major ions, SiO2, Br-, Ba+, Sr2+, 18O, 2H, 13C, 3H, Ne, Ar) combined with a groundwater residence time determination using CFCs and SF6 allows defining the global setting of the study site. A typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model. Terrigenic SF6 excesses have been detected and quantified, which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally. The use of CFCs and SF6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

Fonctionnement hydrogéologique et archives paléoclimatiques d'un aquifère profond méditerranéen (étude géochimique et isotopique du bassin miocène de Valréas (Sud-Est de la France))

AVIGNON-BU Centrale (840072102) / SudocAVIGNON-Bibl. de géologie (840072202) / SudocSudocFranceF

Isotope hydrogeology and geothermal applications to clarify the origin, the sustainability and the character of groundwater flow (examples of the Bohemian and Aquitaine sedimentary basins)

Les études isotopiques couplées avec des informations géothermiques peuvent constituer des outils pertinents pour l exploration des eaux souterraines en tant que ressources en eau potable ou géothermiques. Ce travail combine les deux approches, isotopes de l environnement et radioactifs associés à des données de température sur des aquifères profonds, dans l objectif d enrichir et d améliorer la connaissance des mécanismes de recharge (Bassin d Aquitaine, France) ainsi que des mécanismes de recharge et du potentiel géothermique (Bassin Crétacé de Bohème, République Tchèque).Les isotopes stables (18O, 2H, 13C) utilisés conjointement avec des radioisotopes (14C, 3H) sont utilisés pour estimer l époque de la recharge ainsi que les conditions climatiques qui prévalaient lors de l infiltration depuis la fin de Pléistocène jusqu à nos jours. Définir le type de recharge et les conditions d écoulement est nécessaire pour parvenir à modéliser de façon satisfaisante et fiable les grands systèmes aquifères profonds. Trois types de recharge ont été définis en Europe - (i) continue, (ii) interrompue lors du dernier maximum glaciaire (LGM) un troisième type (iii) correspond à des situations particulières de recharge.Les conditions géographiques et climatiques très différentes rencontrées en France et en République Tchèque ont engendrées une importante hétérogénéité des conditions et processus de recharge. Le sud de la France, avec un climat relativement doux depuis les derniers 40 ka BP, n a pas enregistré d interruption de la recharge. Le temps de séjour des eaux souterraines en Bohème est estimé à environ 11 ka BP au maximum. Cependant, l appauvrissement des teneurs en isotopes stables enregistré suggère une recharge liée à la fonte de la calotte glaciaire Nord Européenne après le dernier maximum glaciaire (LGM), autour de 18-20 ka BP. Des investigations sur les isotopes du carbone minéral dissous des eaux souterraines du bassin de Bohème ont montrées d importantes interactions avec différentes sources de carbone qui ont été identifiées.Pour le site d étude tchèque, les informations apportées par la géochimie ont été complétées par des données géothermiques afin d améliorer la connaissance des flux et de la dynamique des eaux souterraines. Plus d une centaine d enregistrements diagraphiques de température ont été utilisés pour estimer le gradient géothermique. Plusieurs phénomènes viennent perturber le gradient géothermique de la région. Les flux d eau souterraine verticaux et les variations lithologiques et topographiques sont à l origine d une distribution complexe du flux de chaleur, étant majoritairement conditionné par les écoulements souterraines. Les discontinuités peu profondes et les nombreux pointements volcaniques exercent aussi une influence importante sur l écoulement souterrain et donc aussi sur le potentiel géothermique du réservoir. Les investigations sur la géothermie ont ainsi fourni des informations fondamentales sur le potentiel géothermique mais aussi sur les conditions d écoulement des eaux souterraines. La prise en compte de ces informations s avère nécessaire afin de proposer des modèles mathématiques d écoulement réalistes.Isotopic investigations combined with geothermal applications represent powerful tools for the exploration of groundwater potential as a drinking or geothermal resource. This Ph.D. thesis combines both approaches, environmental and radioactive isotopes together with temperature data in deep aquifers, in order to enrich and update the knowledge concerning the aquifer recharge processes in the Aquitaine Basin (France) and the aquifer recharge processes and geothermal potential in the Bohemian Cretaceous Basin (Czech Republic).Stable isotopes (18O, 2H, 13C) combined with radioisotope data (14C, 3H) are used to estimate the recharge timing and climatic conditions prevailing during the infiltration from the Late Pleistocene up to modern time. The character of groundwater recharge and regime are necessary to generate relevant source data for the accurate modelling of complex groundwater systems. Three groups of groundwater recharge types can be distinguished throughout Europe (i) continuous recharge and (ii) interrupted recharge during Last Glacial Maximum and (iii) a group corresponding to particular recharge conditions.The contrasted geographic and climate conditions at both study sites in France and Czech Republic have entailed a great heterogeneity of the recharge conditions and processes. Southern France, with generally mild climatic conditions during the last 40 ka BP, did not experienced considerable hiatus in groundwater recharge. The residence time of groundwater in the Bohemian aquifers is estimated about 11 ka BP at the maximum but the depletion in the stable isotopes suggests that this groundwater originates in the melting of the north European ice sheets after the Last Glacial Maximum period, i.e. 18-20 ka BP. Further investigations on both stable and radioactive carbon isotopes indicated numerous groundwater interactions within the reservoir that were used to delineate the carbon origin within the Bohemian aquifers.Information on groundwater geochemistry was supplemented in the Czech case study by geothermal data in order to improve our knowledge of groundwater flow and dynamics. More than a hundred of temperature records from well-logging measurements were used to assess the geothermal gradient in the Bohemian Cretaceous Basin which is the most promising heat accumulation within the country. Many phenomena can affect the thermal field in the region. Vertical groundwater flow and variations in the lithology and the topography lead to a complicated areal distribution of the geothermal gradient and the heat flux which is dominantly controlled by groundwater. Shallow tectonic structures and numerous volcanic rocks exercise an influence on groundwater flow and therefore exert a secondary effect on the thermal field. The geothermal investigation provided useful information on the geothermal resources within the region but also represents an important tool for understanding groundwater flow, and for constructing realistic hydrogeological models in such a complex geological, tectonic and geothermal context.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Groundwater resources of Uzbekistan: an environmental and operational overview

International audienceAs a result of the massive irrigation development during the Soviet Union era and intensive chemization of agriculture, the surface runoff quality has been degraded in this arid and endorheic region. Moreover hydraulically related groundwater has also been affected. Excessive irrigation has lead to land salinization, which now threatens the soil quality of significant areas where crop yields would be at risk in the future. Since the collapse of the Soviet Union, institutional changes have been undertaken for the management of natural resources and water infrastructure. At present, underdeveloped and inadequate systems have been practiced with respect to groundwater use and management. This paper analyzes the present extent of groundwater resources with consideration to their reserves, quality evolution, and to technical, institutional and transboundary management practices in Uzbekistan

Groundwater Modeling as an Alternative Approach to Limited Data in the Northeastern Part of Mt. Hermon (Syria), to Develop a Preliminary Water Budget

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