Un réseau de métiers CNRS consacré aux Milieux Souterrains et aux Karsts

International audienc

Un réseau de métiers CNRS consacré aux Milieux Souterrains et aux Karsts

International audienc

Un réseau de métiers CNRS consacré aux Milieux Souterrains et aux Karsts

International audienc

Un réseau de métiers CNRS consacré aux Milieux Souterrains et aux Karsts

International audienc

Quantification of spatial and temporal variations in trace element fluxes originating from urban areas at the catchment scale

International audienceBackground, aim, and scopeThe release of trace elements (TE) associated with the development of human activities has accelerated since the nineteenth century, leading to the pollution of river systems. Despite a drastic reduction in industrial inputs in northern Europe, diffuse pollution originating from urban areas still prevents achieving the good status required by the European Water Framework Directive. The objectives of the current study, which is a part of a wider project, were to determine the impact of hydrological dynamics on the total exports of TE from an urban catchment and to develop an assessment tool to evaluate the level of contamination of a catchment based on its specific particulate TE fluxes.Materials and methodsAccordingly, this research investigated the behavior of TE contamination in a 950 km2 catchment (Orge River, France) showing a strong urbanization gradient in downstream direction. Particulate and dissolved samples were collected in the river during a hydrological year at four stations reflecting the increasing urbanization gradient. Trace element concentrations were measured in the samples using inductively coupled plasma/mass spectrometry (ICP-MS). Daily and annual TE fluxes were calculated at the four stations to evaluate the contribution of urban areas to the total TE exports from the catchment.ResultsThe quantification of TE fluxes showed that up to 70% of particulate Cu, Zn, Sb, and Pb exported by the Orge River originated from the urban areas located in the lower catchment portions, especially during average water flow periods characterized by frequent rain events. Moreover, the results show that 50% of the dissolved fluxes of Cu, Zn, and Pb are supplied by urban areas during the entire year, regardless of hydrological conditions, and that the specific contribution of floods to these fluxes (i.e., the June 2016 event) is lower than that in other catchments because of the continuous supply of dissolved metal fluxes to the river in this urbanized environment.ConclusionThese results underline the need to integrate all hydrological conditions for the management of TE contamination in urban areas and not to focus on storm events only. Finally, based on a literature survey, the ratios of specific fluxes were homogeneous across different highly urbanized catchments, and they could be used as a tool to compare the levels of anthropogenic pressure in these contrasted study sites. This observation demonstrates the similar impacts of societal development on urban river geochemistry worldwide, although they occurred during different time periods

Impact of urban pressure on the spatial and temporal dynamics of PAH fluxes in an urban tributary of the Seine River (France)

International audiencePolycyclic aromatic hydrocarbons (PAHs) produced by numerous anthropogenic activities are ubiquitous in the environment and have become a priority concern due to their potential severe biological impacts. A better understanding of PAH transfer at the catchment scale is therefore necessary to improve the management of PAH contaminants and protect rivers. Furthermore, the impact of changes in hydrological regimes and land uses on PAH fluxes should be specifically investigated. Accordingly, the current research monitors the contamination in atmospheric fallout, soils and rivers in a 950-km2 catchment (Orge River) characterized by an increasing urban gradient in downstream direction. During an entire hydrological year, river water contamination was quantified through regular sampling of both particulate and dissolved material at four river-monitoring stations, reflecting the increasing urbanization gradient. The significant input of PAHs from urban areas in downstream river sections corresponded to a specific PAH flux that reached 23 g km−2 y−1 despite the low sediment yield. Moreover, the comparison with runoff-specific fluxes reported in the literature underlined the major impact of urban runoff on the Orge River water and sediment quality. Nevertheless, the annual PAH load exported by the river (21 kg y−1) remained lower than the PAH inputs from atmospheric fallout (173 kg y−1), demonstrating the continuous accumulation of PAH from atmospheric fallout in the catchment soils. Consequently, the notably large PAH stock (close to 1000 tons) resulting from historical contamination of this early-industrialized region continues to increase due to ongoing atmospheric inputs

Drones souterrains, inspection et imagerie 3D : contraintes et potentialités d’un nouvel outil de documentation des grottes et du karst

International audienceLes drones ont connu, au cours des dernières années, une forte diversification de leurs usages. La réduction du poids des engins et la diminution des coûts concourent à ces développements. En grotte, l’usage des drones est limité par l’altération des capteurs d’assistance au télépilotage : GNSS, vision, capteurs d’évitement, centrale inertielle. Le télépilote doit alors conduire la mission avec le double objectif de maintenir l’intégrité de la machine, de la grotte et des personnels, tout en assurant une captation correcte des données. Un test de photogrammétrie 3D, conduit dans la grotte Sainte-Catherine (Ariège) montre un résultat satisfaisant et confirme l’intérêt des drones dans les constructions de modèles 3D en grotte. Les conditions du pilotage, les conditions d’acquisition des données et les potentialités futures sont discutées

Impact of urban pressure on the spatial and temporal dynamics of PAH fluxes in an urban tributary of the Seine River (France)

International audiencePolycyclic aromatic hydrocarbons (PAHs) produced by numerous anthropogenic activities are ubiquitous in the environment and have become a priority concern due to their potential severe biological impacts. A better understanding of PAH transfer at the catchment scale is therefore necessary to improve the management of PAH contaminants and protect rivers. Furthermore, the impact of changes in hydrological regimes and land uses on PAH fluxes should be specifically investigated. Accordingly, the current research monitors the contamination in atmospheric fallout, soils and rivers in a 950-km2 catchment (Orge River) characterized by an increasing urban gradient in downstream direction. During an entire hydrological year, river water contamination was quantified through regular sampling of both particulate and dissolved material at four river-monitoring stations, reflecting the increasing urbanization gradient. The significant input of PAHs from urban areas in downstream river sections corresponded to a specific PAH flux that reached 23 g km−2 y−1 despite the low sediment yield. Moreover, the comparison with runoff-specific fluxes reported in the literature underlined the major impact of urban runoff on the Orge River water and sediment quality. Nevertheless, the annual PAH load exported by the river (21 kg y−1) remained lower than the PAH inputs from atmospheric fallout (173 kg y−1), demonstrating the continuous accumulation of PAH from atmospheric fallout in the catchment soils. Consequently, the notably large PAH stock (close to 1000 tons) resulting from historical contamination of this early-industrialized region continues to increase due to ongoing atmospheric inputs

Tracing the sources of suspended sediment and particle-bound trace metal elements in an urban catchment coupling elemental and isotopic geochemistry, and fallout radionuclides

International audienceThe excessive supply of contaminants from urban areas to rivers during the last centuries has led to deleterious impacts on aquatic ecosystems. The sources, the behavior and the dynamics of these contaminants must be better understood in order to reduce this excessive anthropogenic pollution. Accordingly, the current research investigated the particle-bound trace element (TE) contamination of the 900-km² Orge River (Seine basin, France) and the potential sources of these particles (agricultural or forest soils, channel banks, road deposited sediments), through the analysis of multiple fallout radionuclides, elemental geochemistry and lead isotopic composition on suspended particulate matter (SPM) collected during a hydrological year at four stations following an increasing urbanization gradient (300 to 5000 inhab.km-2). Fallout radionuclide measurements showed an increasing contribution of recently eroded particles from urban areas to the SPM in downstream direction. However, this contribution varied depending on hydrological conditions. A greater contribution of particles originating from urban areas was observed during low stage periods. On the contrary, the contribution of agricultural soils and channel banks that are less enriched in contaminants and fallout radionuclides was higher during seasonal floods, which explained the dilution of radionuclide contents in sediment transiting the river during those events. Trace element contamination of SPM in Cu, Zn, Pb and Sb increased from moderate to significant levels with urban pressure in downstream direction (with corresponding enrichment factors raising from 2 to 6). In addition, Pb isotopic ratios indicated that the main source of Pb corresponded to the "urban" signature found in road deposited sediments. The low variations in lead isotope ratios found in the SPM for contrasting hydrological conditions demonstrated the occurrence of a single source of Pb contamination. These results demonstrate the need to better manage urban runoff during both flood and low precipitation events to prevent the supply of diffuse particle-bound contamination to rivers draining urban areas

Drones souterrains, inspection et imagerie 3D : contraintes et potentialités d’un nouvel outil de documentation des grottes et du karst

International audienceLes drones ont connu, au cours des dernières années, une forte diversification de leurs usages. La réduction du poids des engins et la diminution des coûts concourent à ces développements. En grotte, l’usage des drones est limité par l’altération des capteurs d’assistance au télépilotage : GNSS, vision, capteurs d’évitement, centrale inertielle. Le télépilote doit alors conduire la mission avec le double objectif de maintenir l’intégrité de la machine, de la grotte et des personnels, tout en assurant une captation correcte des données. Un test de photogrammétrie 3D, conduit dans la grotte Sainte-Catherine (Ariège) montre un résultat satisfaisant et confirme l’intérêt des drones dans les constructions de modèles 3D en grotte. Les conditions du pilotage, les conditions d’acquisition des données et les potentialités futures sont discutées