Dissolved matter fluxes in the inner delta of the River Niger

Abstract This study is part of the EQUANIS programme, the objectives of which are (a) estimating inputs from the River Niger to the inner Delta; (b) computing the hydrological balance; and (c) monitoring the quality of water in the central lacustrine basin. Eleven sampling locations were selected near gauging stations, both on the Niger River and its main tributary, the Bani River. Those sites have been sampled weekly since July 1990. The inner delta of the Niger River is a system particularly subject to sahelian and sub-desert climatic conditions and characterized by large flood plains. Time series of input water volumes in the inner delta, and of the water losses within it, show that the water losses are high, due to the intense evaporation, and vary from 6 to 40 km3. The water .losses reach their maximum during the wettest years-up to 47%, and minimum during the driest years-only 32%, due to the reduction of the flooded area. The surface of the flooded area is inferred from the hydrological balance. The preliminary results of this study indicate that the Niger and Bani rivers have low levels of dissolved element concentrations. The mean conductivity values, ranging from 50-80 pS cm-', increase regularly during the low water stage and decrease drastically with rising water. The pH values are slightly basic, ranging from 7.1 to 8. Silica and bicarbonates are the main dissolved species; they always represent more than 75% of TDS. In May, when the rising water stage begins, the waters are poorly mineralized at the input of the delta, while they have been enriched during the dry season in the delta. A good mass balance is found between inputs and outputs through the delta. However, a disequilibrium appears at the sampling sites within the basin, which could be partially linked to poor mixing between the Niger and Bani river waters. The first results from the upper basin and below the inner delta, show low concentrations of matter. The specific dissolved loads vary between 10-12 t km-' year-' for the Niger River and 2.5 t km-2 year-' for the Bani River. The annual input in the inner delta was about 2.2 X lo6 t in 1992-1993. Chemical budgets show a saline deposit of 0.3 x lo6 t in the inner delta. Seasonal variations of the dissolved matter fluxes are very different between the upper and lower parts of the inner delta, due to the breaking of the annual flood and to the more important flood plains in the upper delta. Los flujos de materiales disueltos en el delta inerior del Niger Resumen Es presente estudio forma parte del programa EQUANIS, cuyos objetivos son (a) estimación de los aportes del río Niger al delta interior, (b) cómputo del balance gídrico, y (c) monitoreo de la calidad del agua en la cuenca lacustre central. Se seleccionaron once sitios de muestre0 próximos a las estaciones de aforo tanto en el Niger como en su principal afluente, el Bani. Desde julio de 1990 se llevaron a cabo allí muestreos semanales. EI delta interior del Niger is us sistema particular sometido a condiciones interior, y de pérdidas de agua en is mismo, muestran que las pérdidas son elevadas debido a la evaporación intensa, y fluctúan entre 40 y 6 km3. Las pérdidas de agua son máximas durante los años más húmedos (hasta un 47%) y mínimas durante los años más socos (solo 32%) debido a la reducción de las Breas inundadas. La superficie inundada se deduce del balance hídrico. Los resultados preliminares del estudio indican que los ríos Niger y Bani tienen un bajo nivel de concentración de elementos en disolución. Los valores medios de conductividad que van de 50 a 80 pS cm" se incrementan regularmente durante el período de estiaje y disminuyen drásticamente en períodos de avenidas y variacíon de niveles. Los valores de pH son ligeramente básicos, de 7.1 a 8. Los principales materiales dusueltos son el sílice y los bicarbonatos; siempre representan más del 75% del TDS. En mayo, cuando se inicia el período de crecida, las aguas contienen pocos minerales en la entrada del delta mientras que se han concentrado durante la estación seca del delta. Se observa un buen balance de masa en el delta entre los aportes y descargas, pero aparece un desequilibrio en los sitios de muestre0 dentro de la cuenca, que puede atribuirse parcialmente a una mala mezcla entre las aguals del Niger y del Bani. Los primeros resultados en la cuenca superior y baja del delta interior muestran bajas concentraciones de material. Las cargas disueltas específicas fluctúan entre 10 y 12 t km-2 año-' para el río Niger y 2.5 t km-* año-' para el río Bani. El aporte anual en el delta interior fue de unos 2.2 X lo6 t en 1992-1993. Los balances químicos presentan un depósito salino de 0.3 X lo6 t en el delta interior. Las variaciones estacionales de los flujos de materiales son muy diferentes entre las partes alta y baja del delta interior, debido al inicio de la crecida anual y a las más importantes planicies de inundación en la parte superior del delta

Radon measurement in karstic waters with Lucas cell technique

Based on Lucas cell technique, the portable device named “PRASSI” (SILENA mod. 5S) was used to realise discrete radon measurements in water samples. The calibration factor is (64.766.9) cpmQBq21 and, with the present set-up for measuring radon in water, the detection and the determination limits are, respectively, 0.007 and 0.020 Bq. Thus, the device is well adapted for determining low radon content in karstic waters. Several discrete radon samplings were performed nearly every week in the three main springs of the Bastareny karstic system (Catalonian Pyrenees, N-E Spain). Thus, it was possible to estimate the reproducibility of the methodology as well as to characterise every spring of the aquifer in relation to their hydrogeological features. With the portable radon monitor, some useful measurements were achieved to estimate radon loss due to degassing process over short distances, with important consequences for radon studies in karstic waters. Lastly, it was possible to perform intensive sampling during a flood and the results point out the great variability of radon levels, closely related to the flow rate trend. That permitted also an intercomparison with other radon probes installed previously in every spring, for continuous radon measurements

Irreducibility and Asymptotics of Stochastic Burgers Equation Driven by α-stable Processes

The irreducibility, moderate deviation principle and $\psi$-uniformly exponential ergodicity with $\psi(x):=1+\|x\|_0$ are proved for stochastic Burgers equation driven by the $\aa$-stable processes for $\aa\in (1,2),$ where the first two are new for the present model, and the last strengthens the exponential ergodicity under total variational norm derived in \cite{Do-Xu-Zh-14}

Uso de isótopos estáveis da água para um melhor entendimento dos processos hidrogeológicos no Haiti: visão geral de dados de δ18O e δ2H existentes

International audienceIsotope hydrological studies carried out since 1987 in Haiti have proven to be effective in improving conceptual models of the principal aquifers in this Caribbean island nation. However, many of these studies have been limited and are mostly unpublished. It is, therefore, important to share the available datasets with scientists and water managers to support further studies and guide decision-making. Eleven datasets were compiled in a unique database for continued advancement and application. This dataset now contains 248 δ 18 O and δ 2 H results from water samples collected at 190 locations throughout the country. δ 18 O and δ 2 H values range, respectively, from –3.8 to –8.95‰ and –67.4 to –16.8‰ for precipitation ( n = 5), 0.9 to 2.76‰ and 8.8 to 18.4‰ for lakes ( n = 4), –2.61 to 4.98‰ and –26.63 to 28.2‰ for rivers ( n = 11), –5.11 to –2.6‰ and –29.8 to –6.9‰ for springs ( n = 82) excluding hot springs, and –5.1 to –1.37‰ and –29.4 to –2.9‰ for boreholes ( n = 142). The overall presentation of the available data is complemented with an overview of the studies in which stable isotope data acquisition was performed. The global dataset is presented under three primary contexts: (1) elaboration of a local isotope meteoric water line of equation δ 2 H = 7.2δ 18 O + 8.8 supported with data predominately from the Ouest jurisdictional department, (2) spatial variability analysis of the dataset, and (3) definition of the altitude gradient (per 100 m) using freshwater springs of the Plaine du Cul-de-Sac/Massif de la Selle area of –6.67‰ for δ 2 H and –0.09‰ for δ 18 O.Los estudios hidrológicos isotópicos realizados desde 1987 en Haití han demostrado ser eficaces para mejorar los modelos conceptuales de los principales acuíferos de esta nación insular del Caribe. Sin embargo, muchos de estos estudios han sido limitados y en su mayoría no se han publicado. Por lo tanto, es importante compartir los conjuntos de datos disponibles con los científicos y los gestores del agua para apoyar nuevos estudios y orientar la toma de decisiones. Se recopilaron once conjuntos de datos en una base de datos única para su avance y aplicación ulterior. Este conjunto de datos contiene ahora 248 resultados de δ 18 O y δ 2 H de muestras de agua recogidas en 190 lugares de todo el país. Los valores de δ 18 O y δ 2 H varían, respectivamente, de –3.8 a –8.95‰ y de –67.4 a –16.8‰ para las precipitaciones ( n = 5), de 0.9 a 2.76‰ y de 8.8 a 18.4‰ para los lagos ( n = 4), de –2.61 a 4.98‰ y de –26.63 a 28.2‰ para los ríos ( n = 11), –5.11 a –2.6‰ y –29.8 a –6.9‰ para los manantiales ( n = 82), excluyendo las fuentes termales, y –5.1 a –1.37‰ y –29.4 a –2.9‰ para los pozos de sondeo ( n = 142). La presentación global de los datos disponibles se complementa con un resumen de los estudios en los que se realizó la adquisición de datos de isótopos estables. El conjunto de datos globales se presenta en tres contextos principales: (1) elaboración de una línea local de isótopos del agua meteórica de ecuación δ 2 H = 7.2 δ 18 O + 8.8 apoyada con datos predominantemente del departamento jurisdiccional Ouest, (2) análisis de la variabilidad espacial del conjunto de datos, y (3) definición del gradiente de altitud (por 100 m) utilizando manantiales de agua dulce de la zona de Plaine du Cul-de-Sac/Massif de la Selle de –6.67‰ para δ 2 H y –0.09‰ para δ 18 O.Les études hydrogéologiques menées depuis 1987 à Haïti ont montré leur intérêt pour l’amélioration des modèles conceptuels des principaux aquifères de ce pays insulaire des Caraïbes. Il est donc important de partager ces données avec les scientifiques et les gestionnaires de la ressource en eau pour appuyer d’autres projets et guider la prise de décision. Onze jeux de données ont été compilés dans une base de données unique évolutive à visée opérationnelle. Ce jeu de données contient aujourd’hui 248 résultats d’analyses de δ 18 O et δ 2 H provenant d’échantillons d’eau collectés sur 190 sites répartis dans tout le pays. Les valeurs de δ 18 O et δ 2 H s’étendent respectivement de –3.8 à –8.95‰ et –67.4 à –16.8‰ pour les pluies ( n = 5), 0.9 à 2.76‰ et 8.8 à 18.4‰ pour les lacs ( n = 4), –2.61 à 4.98‰ et –26.63 à 28.2‰ pour les rivières ( n = 11), –5.11 à –2.6‰ et –29.8 à –6.9‰ pour les sources ( n = 82) en excluant les sources chaudes, et –5.1 à –1.37‰ et –29.4 à –2.9‰ pour les forages ( n = 142). La présentation générale des données est complétée par un résumé des études ayant permis l’acquisition des données en isotopes stables. Le jeu de données complet est présenté à l’aide de trois principaux aspects: (1) élaboration de la droite météorique locale des pluies d’équation δ 2 H = 7.2δ 18 O + 8.8 s’appuyant sur des données principalement du département de l’Ouest, (2) analyse de la variabilité spatiale du jeu de données, et (3) définition d’un gradient d’altitude (par 100 m) utilisant les eaux douces des sources de la plaine du Cul-de-Sac/Massif de la Selle de –6.67‰ pour le δ 2 H et –0.09‰ pour le δ 18 O.Estudos hidrológicos isotópicos conduzidos no Haiti desde 1987 têm provado serem eficientes para melhorar os modelos conceituais dos principais aquíferos dessa nação das ilhas caribenhas. Porém, muitos destes estudos têm sido limitados e são majoritariamente não publicados. É importante, portanto, compartilhar os conjuntos de dados disponíveis com cientistas e gestores hídricos para incentivar mais estudos e guiar tomadas de decisão. Onze conjuntos de dados foram compilados em um único banco de dados para continuar seu avanço e aplicação. Este novo conjunto de dados agora contém 248 resultados de δ 18 O e δ 2 H de amostras de água, coletadas em 190 locais pelo país. Os valores de δ 18 O e δ 2 H variam, respectivamente, de 3.8 a –8.95‰ e –67.4 a 16.8‰ para precipitação ( n = 5), 0.9 a 2.76‰ e 8.8 a 18.4‰ para lagos ( n = 4), –2.61 a 4.98‰ e –26.63 a 28.2‰ para rios ( n = 11), –5.11 a –2.6‰ e –29.8 a –6.9‰ para nascentes ( n = 82), excluindo fontes termais, e –5.1 a –1.37‰ e –29.4 a 2.9‰ para poços ( n = 142). A apresentação geral dos dados disponíveis é complementada com uma visão geral dos estudos em que houveram coleta de dados de isótopos estáveis. O conjunto global dos dados é apresentado sob três contextos primários: (1) elaboração de uma reta meteórica local de equação δ 2 H = 7.2δ 18 O +8.8 baseada predominantemente nos dados do departamento jurisdicional de Ouest, (2) análise da variabilidade espacial do conjunto de dados, e (3) definição da altitude do gradiente (a cada 100 m) utilizando fontes de água doce da área do Plaine du Cul-de-Sac/Massif de la Selle de –6.67‰ para δ 2 H e –0.09‰ para δ 18 O

The fate of cellulose nanocrystal stabilised emulsions after simulated gastrointestinal digestion and exposure to intestinal mucosa

It is well recognised that the average UK diet does not contain sufficient fibre. However, the introduction of fibre is often at the detriment of the organoleptic properties of a food. In this study on the gastrointestinal fate of nanoparticles, we have used cellulose nano-crystals (CNCs) as Pickering stabilising agents in oil in water emulsions. These emulsions were found to be highly stable against coalescence. The CNC and control emulsions were then exposed to simulated upper gastrointestinal tract digestion and the results compared to those obtained from a conventional protein stabilised emulsion. Finally the digested emulsions were exposed to murine intestinal mucosa and lipid and bile absorption was monitored. Importantly, the results show that the CNCs were entrapped in the intestinal mucus layer and failed to reach the underlying epithelium. This entrapment may also have led to the reduced absorption of saturated lipids from the CNC stabilised emulsion versus the control emulsion. The results show the potential of CNCs as a safe and effective emulsifier