Modèle de lessivage des matières en suspension en milieu urbain

Le présent travail porte sur le développement et la validation du modèle conceptuel RQSM (Runoff Quality Simulation Model). Le modèle RQSM a pour objectif de simuler le lessivage des matières en suspension. Le modèle RQSM considère que l’accumulation est infinie sur les surfaces perméables et imperméables. Il utilise l’énergie cinétique des précipitations pour décrire la mise en suspension des particules solides. Il modélise le transport des matières en suspension à l’aide de la théorie des systèmes linéaires.Les charges de matière en suspension mesurées durant 22 événements pluvieux enregistrés à l’exutoire du sous-bassin (1) de l’arrondissement de Verdun au Canada et à l’exutoire de trois sous-bassins de la ville de Champaign aux États‑Unis ont servi à valider le modèle RQSM. Les charges de matière en suspension simulées par le modèle RQSM ont été comparées aux charges mesurées et aux charges simulées par le modèle de « rating curve » et par le modèle de lessivage exponentiel du logiciel SWMM. Les charges simulées à l’aide du modèle RQSM étaient comparables aux charges mesurées. De plus, la performance du modèle RQSM a été jugée équivalente à celle des modèles exponentiel et « rating curve ». Une analyse de sensibilité menée sur le modèle RQSM a mis en lumière l’influence de chaque paramètre sur la charge simulée.Urban runoff pollution due to suspended particles is of great concern for sewer system managers. Indeed, particles are the main source of urban water pollution because a large amount of chemical elements and organic wastes are associated with particles. Modelling runoff pollution due to particles is essential for the evaluation of its impact on receiving waters and for the adequate design of treatment structures.This paper presents a new conceptual model called RQSM (Runoff Quality Simulation Model) used to simulate the washoff (erosion and transport of particles) of total suspended particles (TSS) at the outlet of urban catchments. Conceptual models can accurately represent complex physical phenomena with a limited number of parameters and a simple mathematical formulation. Moreover, they can be easily calibrated and used at many sites.The build-up of solid particles in the RQSM model is infinite for pervious and impervious areas. The erosion process is related to the rainfall kinetic energy. Two relationships involving two erosion parameters are used, one for the impervious areas and the other for the pervious areas. The transport of suspended particles is described using the linear system theory. A rectangular impulse response function with a duration equal to the time of concentration describes the catchment response to an instantaneous erosion rate. Thereafter, a convolution product between the erosion rate and the rectangular impulse response function is used to compute loads of TSS at the catchment outlet.The mathematical formulation of the RQSM model has three advantages. Firstly, it describes the washoff of TSS by using only rainfall intensity. Secondly, it treats the washoff of pervious and impervious areas separately. Finally, it uses only two parameters to describe the washoff.The RQSM model was validated with the help of 285 TSS data points monitored during 22 rainfall events. Four rainfall events were monitored in the subcatchment (1) of Verdun borough in Canada and 18 rainfall events were monitored on three subcatchments in Champaign city (USA). The catchment areas varied between 6.8 and 177 ha, the catchment slopes between 0.4% and 1%, and the ratio of directly drained impervious area between 0.19 and 0.58. Land use was residential in two catchments and commercial for the other ones.The first step in the RQSM model validation was to calibrate the two erosion parameters. This step was realized using 11 measured TSS pollutographs. The erosion parameter for impervious areas was calibrated first for low intensity rainfall. The erosion parameter for pervious areas was then calibrated for high intensity rainfall.The second validation step was to simulate the TSS load resulting from 11 other rainfalls. The simulated loads of the RQSM model were compared to the measured loads. They were also compared to the simulated loads obtained with the rating curve model and with the SWMM exponential washoff model. Comparisons were made using three performance criteria: the Nash criterion, the ratio of the simulated TSS mass divided by the measured TSS mass (RM), and the peak charge ratio (RP). Reasonable agreement was reached between loads computed with the RQSM model and measured loads. The mean RM was 1.08 and the standard deviation was 35%. Moreover, the Nash criterion was greater than 0.6 for 50% of simulated events. Unfortunately, the number of events was insufficient to detect statistically significant differences in accuracy, between the RQSM model, the rating curve and the exponential model. Nevertheless, a qualitative study based on the value of the three performance criteria showed that the results given by the RQSM model are equivalent to the results given by the SWMM exponential wash off model.Finally, a sensitivity analysis was conducted on the RQSM model. In order to achieve the sensitivity analysis, reference values were attributed to the parameters of the RQSM model. The values of the RQSM parameters were then changed individually and the resulting change in the Nash criterion was noted. The change in the Nash value indicates that for rainfalls of high intensity and short duration, the RQSM method is particularly sensitive to the time of concentration. In the other cases, the erosion parameter of impervious areas was the most sensitive parameter

Modèles hydrologiques et hydrauliques pour la gestion en temps différé des réseaux d'aissainissement

La gestion en temps différé des réseaux d'assainissement sert à évaluer la performance de fonctionnement des réseaux d'assainissement au regard de la quantité et de la qualité des eaux rejetées dans le milieu naturel. La thèse présente trois modèles originaux de simulation hydrologique et hydraulique. Ces trois modèles constituent l'ossature d'un outil de simulation pour un système de gestion en temps différé des réseaux d'assainissement. Le premier modèle développé est la méthode IRH (Improved Rational Hydrograph) destinée à la simulation du débit de ruissellement. La méthode IRH est une généralisation de la méthode rationnelle basée sur la théorie des systèmes linéaires. La méthode IRH présente deux variantes. La première variante, nommée IRH1, traite globalement le ruissellement sur le bassin urbain et dans le réseau d'assainissement. La seconde variante, nommée IRH2, traite séparément le ruissellement sur le bassin et dans le réseau d'assainissement. La méthode IRH a été validée à l'aide de 41 événements pluvieux mesurés sur 7 bassins différents situés en Amérique du Nord et en Europe. La méthode IRH a reproduit précisément les hydrogrammes mesurés. De plus, la précision des hydrogrammes fournis par la méthode IRH1 est comparable à celle du modèle du réservoir non linéaire mais inférieure à celle de la méthode IRH2. Le second modèle développé est le modèle RQSM (Runoff Quality Simulation Model) destiné à la simulation des charges de matière en suspension. Le modèle RQSM utilise l'énergie cinétique des précipitations pour décrire le processus de mise en suspension des particules solides. Le transport des matières en suspension est décrit à l'aide de la théorie des systèmes linéaires. Le modèle RQSM a été validé à l'aide de 285 mesures de matière en suspension obtenues au cours de 22 événements pluvieux mesurés sur 4 sous bassins différents. Le modèle RQSM a convenablement reproduit les pollutogrammes mesurés. De plus, il a fourni des résultats comparables à ceux du modèle de lessivage exponentiel. Le troisième modèle développé est destiné au suivi et à la validation des mesures pour un déversoir d'orage latéral à seuil court. La validation et le suivi des mesures sont réalisés grâce à l'utilisation combinée d'un système d'instrumentation et d'une loi de déversement. La procédure de suivi et de validation des mesures pour un déversoir d'orage latéral a été validée à l'aide de 24 essais réalisés sur un dispositif expérimental équipé de capteurs couramment utilisés en réseaux d'assainissement. La procédure a permis d'identifier et de corriger les erreurs de mesure contenues dans les échantillons de données

Changes in Cardiac Autonomic Regulation after Acute Lung Exposure to Carbon Nanotubes: Implications for Occupational Exposure

Carbon nanotubes (CNTs) are among the most relevant engineered nanomaterials (ENMs). Given the expected rise of exposure to ENMs, there is concern that they may adversely affect health of exposed people. Aim of the study was to test the hypothesis that single wall carbon nanotubes (SWCNTs) pulmonary exposure acutely affect the autonomic cardiovascular regulation in conscious rats. We studied Wistar-Kyoto rats in which a telemetry transmitter for continuous arterial pressure (AP) and heart rate (HR) recordings was surgically implanted. SWCNTs dispersed in phosphate buffer saline (PBS) or PBS alone were randomly administered intratracheally. Immediately before, and 24 hours after each instillation a 30 min AP recording was performed. The sequence analysis was performed to evaluate the baroreflex function. In the control group, PBS instillation did not induce any significant changes. At variance the SWCNT exposure induced a significant reduction of baroreflex system (BRS) (3.5 \ub1 0.6 versus 2.6 \ub1 0.40\u2009msec/mmHg) without significant changes in the occurrence of baroreflex sequences (7.5 \ub1 0.47 % versus 7.4 \ub1 0.38 %). Our results show that SWCNT pulmonary exposure might affect the cardiovascular autonomic regulation thus contributing to cardiac and arrhythmic events

Electroencephalographic response to sodium nitrite may predict delayed cerebral ischemia after severe subarachnoid hemorrhage

OBJECTIVES: Aneurysmal subarachnoid hemorrhage often leads to death and poor clinical outcome. Injury occurring during the first 72 hours is termed "early brain injury," with disruption of the nitric oxide pathway playing an important pathophysiologic role in its development. Quantitative electroencephalographic variables, such as α/δ frequency ratio, are surrogate markers of cerebral ischemia. This study assessed the quantitative electroencephalographic response to a cerebral nitric oxide donor (intravenous sodium nitrite) to explore whether this correlates with the eventual development of delayed cerebral ischemia. DESIGN: Unblinded pilot study testing response to drug intervention. SETTING: Neuroscience ICU, John Radcliffe Hospital, Oxford, United Kingdom. PATIENTS: Fourteen World Federation of Neurosurgeons grades 3, 4, and 5 patients (mean age, 52.8 yr [range, 41-69 yr]; 11 women). INTERVENTIONS: IV sodium nitrite (10 μg/kg/min) for 1 hour. MEASUREMENTS AND MAIN RESULTS: Continuous electroencephalographic recording for 2 hours. The alpha/delta frequency ratio was measured before and during IV sodium nitrite infusion. Seven of 14 patients developed delayed cerebral ischemia. There was a +30% to +118% (range) increase in the alpha/delta frequency ratio in patients who did not develop delayed cerebral ischemia (p < 0.0001) but an overall decrease in the alpha/delta frequency ratio in those patients who did develop delayed cerebral ischemia (range, +11% to -31%) (p = 0.006, multivariate analysis accounting for major confounds). CONCLUSIONS: Administration of sodium nitrite after severe subarachnoid hemorrhage differentially influences quantitative electroencephalographic variables depending on the patient's susceptibility to development of delayed cerebral ischemia. With further validation in a larger sample size, this response may be developed as a tool for risk stratification after aneurysmal subarachnoid hemorrhage.This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Role of nitric oxide in glioblastoma therapy: another step to resolve the terrible puzzle?

Glioblastoma Multiforme, the most common and aggressive primary brain tumor, remains incurable despite of the advent of modern surgical and medical treatments. This poor prognosis depends by the recurrence after surgery and intrinsic or acquired resistance to chemotherapy and radiotherapy. Nitric oxide is a small molecule that plays a key roles in glioma pathophysiology. Many researches showing that NO is involved in induction of apoptosis, radiosensitization and chemosensitization. Therefore, NO role, if clarified, may improve the knowledge about this unsolved puzzle called GBM

A New Model for Simulating TSS Washoff in Urban Areas

This paper presents the formulation and validation of the conceptual Runoff Quality Simulation Model (RQSM) that was developed to simulate the erosion and transport of solid particles in urban areas. The RQSM assumes that solid particle accumulation on pervious and impervious areas is infinite. The RQSM simulates soil erosion using rainfall kinetic energy and solid particle transport with linear system theory. A sensitivity analysis was conducted on the RQSM to show the influence of each parameter on the simulated load. Total suspended solid (TSS) loads monitored at the outlet of the borough of Verdun in Canada and at three catchment outlets of the City of Champaign in the United States were used to validate the RQSM. TSS loads simulated by the RQSM were compared to measured loads and to loads simulated by the Rating Curve model and the Exponential model of the SWMM software. The simulation performance of the RQSM was comparable to the Exponential and Rating Curve models

A New Model for Simulating TSS Washoff in Urban Areas

This paper presents the formulation and validation of the conceptual Runoff Quality Simulation Model (RQSM) that was developed to simulate the erosion and transport of solid particles in urban areas. The RQSM assumes that solid particle accumulation on pervious and impervious areas is infinite. The RQSM simulates soil erosion using rainfall kinetic energy and solid particle transport with linear system theory. A sensitivity analysis was conducted on the RQSM to show the influence of each parameter on the simulated load. Total suspended solid (TSS) loads monitored at the outlet of the borough of Verdun in Canada and at three catchment outlets of the City of Champaign in the United States were used to validate the RQSM. TSS loads simulated by the RQSM were compared to measured loads and to loads simulated by the Rating Curve model and the Exponential model of the SWMM software. The simulation performance of the RQSM was comparable to the Exponential and Rating Curve models