Tropical regions are affected by intense soil erosion associated with deforestation, overgrazing, and cropping intensification. This land degradation leads to important on-site (e.g., decrease in ...soil fertility) and off-site (e.g., reservoir siltation and water pollution) impacts. This study determined the mean soil particle and sediment residence times in soils and rivers of three subcatchments (3–12
km
2) with contrasted land uses (i.e., cropland, forests, and rangelands) draining to a reservoir located in highlands of the transvolcanic Mexican belt. Calculations were based on rainfall amount and river discharges as well as on fallout radionuclide measurements (Be-7, Cs-137, and Pb-210) conducted on rainfall precipitated samples, soil sampled in the catchments, and suspended sediment collected by automatic samplers in the river during most storms recorded throughout the 2009 rainy season. Calculations using a radionuclide two-box balance model showed that the mean residence time of particles in soils ranged between 5000
±
1500 and 23,300
±
7000
years. In contrast, sediment residence time in rivers was much shorter, fluctuating between 50
±
30 and 200
±
70
days. The shortest mean residence times were measured in a hilly catchment dominated by cropland and rangelands, whereas they were the longest in an undulating catchment dominated by forests and cropland. Calculation of the Be-7/excess-Pb-210 in both rainfall and sediment allowed gaining insight on sediment dynamics throughout the rainy season. The first heavy storms of the year exported the bulk of the sediment stock accumulated in the river channel during the previous year. Then, during the rainy season, the two steeper catchments dominated by cropland and rangelands reacted strongly to rainfall. Sediment was indeed eroded and exported from both catchments during single heavy storms on several occasions in 2009. In contrast, the agro-forested catchment with gentler slopes exported sediment at a constant and low rate throughout the rainy season. Overall, land cover and flood type clearly proved to exert more control on sediment export than slope steepness and rainfall erosivity. Our results show the priority of stabilising old gully systems to prevent their extension by regressive erosion to cropland and to concentrate the implementation of on-site erosion control measures in cropland and rangeland of the most reactive catchments.
Recent epidemiological findings have suggested that urban atmospheric pollution may have adverse effects on the cardiovascular system as well as on the respiratory system. We carried out an ...exhaustive search of published studies investigating links between coronary heart disease and urban atmospheric pollution. The review was conducted on cited articles published between 1994 and 2005 and whose main objective was to measure the risk of ischaemic heart diseases related to urban pollution. Of the 236 references identified, 46 epidemiological studies were selected for analysis on the basis of pre-defined criteria. The studies were analysed according to short-term effects (time series and case-crossover designs) and long-term effects (case-control and cohort studies). A link between coronary heart disease and at least one of the pollutants studied (PM10, O3, NOx, CO, SO2) emerged in 40 publications. Particulate matter, nitrogen oxides, and carbon monoxide were the pollutants most often linked with coronary heart disease. The association was inconstant for O3. Although the mean mortality or morbidity risk related to urban atmospheric pollution is low compared with that associated with other better-known risk factors, its impact on health is nevertheless major because of the large number of people who are exposed. This exhaustive review supports the possibility that urban pollution is indeed an environmental cardiovascular risk factor and should be considered as such by the cardiologists.
Purpose
Quantifying suspended sediment fluxes and dynamics across mountains, and identifying the origin of sediment in severely eroded areas, are of primary importance for the management of water ...resources. This contribution aims to generalise previous results from suspended sediment fingerprinting obtained during 2007–2009 in a mesoscale Alpine catchment (the Bléone River; 905 km
2
) in France, and to assess variability in sediment sources throughout the second half of the twentieth century.
Materials and methods
Sediment fingerprinting, based on elemental geochemistry and radionuclide measurements, was conducted on a sediment core collected in an alluvial floodplain at the basin outlet. This technique was combined with hydro-sedimentary time-series to reconstruct the origin of suspended sediment deposited at this location over the last 50 years.
Results and discussion
Interpretation of sedimentation based on historical hydrological databases corroborates core dating obtained with
137
Cs and
210
Pb
xs
activity measurements. Black marls and (marly) limestone sources provided the main fraction of sediment throughout the sequence (40 and 22 %, respectively). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16 %, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. However, the relatively homogeneous sediment composition throughout the sequence confirms that core-derived information is representative of widespread flood events.
Conclusions
These results are consistent with those obtained in previous studies. They also outline the need to take into account the entire grain size range of fine sediment in order to provide an overall picture of sediment sources and transfers within highly erosive catchments. This study also emphasizes the importance of using archival data to validate the results of sediment fingerprinting studies conducted during short contemporary monitoring programmes, and to extend fingerprinting of sediment sources over longer time-scales which include large and widespread floods.
Purpose: Quantifying suspended sediment fluxes and dynamics across mountains, and identifying the origin of sediment in severely eroded areas, are of primary importance for the management of water ...resources. This contribution aims to generalise previous results from suspended sediment fingerprinting obtained during 2007–2009 in a mesoscale Alpine catchment (the Bléone River; 905 km22^2) in France, and to assess variability in sediment sources throughout the second half of the twentieth century.Materials and methods: Sediment fingerprinting, based on elemental geochemistry and radionuclide measurements, was conducted on a sediment core collected in an alluvial floodplain at the basin outlet. This technique was combined with hydro-sedimentary time-series to reconstruct the origin of suspended sediment deposited at this location over the last 50 years.Results and discussion: Interpretation of sedimentation based on historical hydrological databases corroborates core dating obtained with 137137^{137}Cs and 210210^{210}Pbxsxs_{xs} activity measurements. Black marls and (marly) limestone sources provided the main fraction of sediment throughout the sequence (40 and 22 %, respectively). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16 %, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. However, the relatively homogeneous sediment composition throughout the sequence confirms that core-derived information is representative of widespread flood events.Conclusions : These results are consistent with those obtained in previous studies. They also outline the need to take intoaccount the entire grain size range of fine sediment in order to provide an overall picture of sediment sources and transferswithin highly erosive catchments. This study also emphasizes the importance of using archival data to validate the results ofsediment fingerprinting studies conducted during short contemporary monitoring programmes, and to extend fingerprinting of sediment sources over longer time-scales which include large and widespread floods.
Influence of flow measurement uncertainty related to the calculation of TSS and particulate organic carbon fluxes: application to an alpine river (Isère, France).
Particulate Flux estimation ...(suspended sediment and associated substances such as organic matter or micropolutants) is a major issue in mountain rivers. A database of high-frequency (30 minutes) discharge, suspended solids (TSS) and particulate organic carbon (POC) on Isère River in Grenoble was used for the calculation of annual fluxes and during major floods over 6 years (2006-2011). Fluxes were calculated by summing the 30 minutes fluxes. The study presents a method for calculating uncertainty fluxes based on Monte Carlo simulations using the errors on the relationships between continuous measurement / experimental measurements (height / flow, TSS / Turbidity, TSS / POC). In particular, the effect of discharge for the calculation of uncertainty is analyzed for different error scenarios (0, 3, 10, 20, 30% and using a mean daily discharge). The method allowed estimating uncertainties < 10% for annual fluxes of TSS and POC whatever the scenario. However, uncertainties are more important for flood events (up to 30% with the use of a mean daily discharge). It appears from the study that the influence of the error on the discharge is relatively less important than the errors on the parameters MES and POC. It is also shown that the mean daily discharge should be avoided for flux calculations and that high frequency database remains the best alternative for a good estimate of the fluxes.
L’estimation des flux particulaires (sédiment en suspension et substances associées telles que la matière organique ou les micropolluants) est un enjeu majeur dans les rivières de montagne. Une base de données haute fréquence (30 minutes) de débit, matières en suspension (MES) et carbone organique particulaire (POC) sur l’Isère à Grenoble a été utilisée pour le calcul des flux annuels et pendant des crues majeures sur 6 années de mesures (2006-2011). L’étude présente une méthode de calcul d’incertitude des flux basée sur des simulations Monte Carlo utilisant les erreurs sur les relations entre mesure en continu et mesure expérimentale (hauteur/ débit, MES/ Turbidité, MES/ POC). L’effet du débit sur le calcul d’incertitude est analysé pour différents scenarios d’erreur (0, 3, 10, 20 et 30 % et utilisation d’un débit moyen journalier). La méthode permet d’estimer des incertitudes inférieures à 10% pour les flux annuels de MES et POC quel que soit le scénario. En revanche, les incertitudes sont plus importantes pour les événements de crue (jusqu’à 30% avec l’utilisation d’un débit moyen journalier). Il ressort de l’étude que l’influence de l’erreur sur le débit est relativement moins importante que celle des erreurs déterminées sur les paramètres MES et POC. Il est également montré que le débit moyen journalier peut entrainer d’importantes incertitudes sur les calculs de flux notamment en période de crues, durant lesquelles une grande partie du flux de MES annuel de l’Isère peut avoir lieu. Il ressort de l’étude que la base de données haute fréquence reste la meilleure alternative pour une bonne estimation des flux.
Arnaud Jérémy, Dutordoir Solène, Némery Julien, Belleudy Philippe. Influence de la mesure du débit sur l’incertitude liée au calcul de flux de matières en suspension et de carbone organique particulaire. Application sur un cours d’eau alpin (l’Isère à Grenoble, France). In: 35es journées de l’hydraulique de la Société Hydrotechnique de France. Hydrométrie 2013. Paris, 15-16 mai 2013. 2013.
Nemery Jean-Claude, Dupéron Olivier, Georges Franck, Guillemin Philippe, Traoré Seydou. 8. Rapports, Études et avis des organismes consultatifs. In: Annuaire des collectivités locales. Tome 19, 1999. ...pp. 535-551.
Némery Jean-Claude,Dupéron Olivier,Georges Franck,Guillemin Philippe,Traoré Seydou. 8 - Rapports, études et avis des organismes consultatifs. In: Annuaire des collectivités locales. Tome 20, 2000. La ...réforme de l'intercommunalité. pp. 587-602.
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