From flood to drought: Transport and reactivity of dissolved organic matter along a Mediterranean river

[cat] Els rius juguen un rol essencial en el funcionament biogeoquímic global, ja que enllacen els cicles biogeoquímics terrestres amb els oceànics. En el si del cicle del carboni, els rius reben matèria orgànica dissolta (MOD) d’una gran varietat d’orígens, la qual és transportada riu avall i alliberada al mar. Hi ha evidències creixents que aquest pas, no consisteix només en un transport conservatiu, sinó que a més, té lloc un processat intern que en modifica qualitats i, fins a cert punt, l’oxida i allibera a l’atmosfera en forma de CO2. Malgrat tot, fins ara no s’ha avaluat com ocorren aquestes modificacions des d’una perspectiva longitudinal, de capçalera a desembocadura, ni el rol que la hidrologia fluvial juga en el desenvolupament d’aquests patrons longitudinals. Aquesta tesi explora el transport i la reactivitat de la MOD al llarg d’un riu Mediterrani (la Tordera) durant un ventall de condicions hidrològiques que comprenen des de grans avingudes fins a sequeres estivals. Primerament, es presenta un nou mètode quimiomètric per a determinar la composició de la fracció fluorescent de la MOD basat en una anàlisi neuronal amb mapes autoorganitzats de Kohonen. Aquesta anàlisi revela la presència de 4 fraccions de matèria orgànica: una relacionada amb la tirosina, una amb el triptòfan, i dues amb substàncies húmiques. Seguidament, es presenten els patrons longitudinals d’aquestes quatre fraccions, juntament amb un balanç de masses calculat a tretze segments de riu situats consecutivament riu avall. Els resultats d’aquesta tesi doctoral demostren que el pas fluvial és un pas decisiu que determina la qualitat i la quantitat de MOD que és finalment alliberada als mars. Les crescudes, malgrat que són esdeveniments molt puntuals en el temps, representen la màxima capacitat del riu d’exportar MOD i, a més, ho fan amb un mínim processat intern. En canvi, durant cabal basal i sequera, tenen lloc importants canvis durant el transport fluvial. Aquesta estacionalitat temporal en la qualitat i quantitat de la MOD exportada, determinada principalment per les condicions hidrològiques, pot ser determinant pel destí que tindrà la MOD un cop al mar.[eng] Rivers play a key role in the global biogeochemical functioning, as they link the biogeochemical cycles of the terrestrial and oceanic systems. In the framework of the carbon cycle, streams and rivers receive dissolved organic matter (DOM) from a variety of sources which is subsequently transported downstream and delivered to the oceans. However, there is increasing evidence that this step involves not only a relocation of DOM from the land to the seas, but also an important in-stream processing which modifies its quality and properties and, to some extent, outgas it to the atmosphere as CO2. However, up to now it has not been assessed how these modifications occur along a longitudinal perspective and, most importantly, the role that hydrology plays in such downstream patterns of DOM processing. This thesis explores the transport and reactivity of DOM along a Mediterranean river (la Tordera) under a variety of hydrological conditions ranging from flash floods to summer droughts. First, the composition of DOM was determined using 3D fluorescence spectroscopy (emission-excitation matrices) and a novel chemometric approach based on a self-organising maps analysis coupled with a correlation analysis. This step allowed discerning the presence of four DOM moieties: a tyrosine-like, a tryptophan-like, and two humic-like fluorescence components. Next, longitudinal patterns of these components are presented for a range of hydrological conditions. Along the main stem, the river exhibited three reaches with a differentiated DOM character: in the headwaters DOM had an eminent humic-like character derived from the drainage of the surrounding terrestrial catchment (high HIX); in the middle reaches (from Sant Celoni to Fogars de la Selva) there was a predominance of the protein-like component C2 reflecting the effect of direct anthropogenic water inputs (concomitant high nutrient concentrations); and the lowest part of the river was dominated by the protein-like component C1 and high FI, suggesting a predominance of microbially-derived DOM. Hydrology appeared to act as a modulator of such longitudinal patterns: during drought, the spatial heterogeneity of DOM character was maximised, whereas during flood conditions there was an homogenisation over the longitudinal dimension, consisting in a highly aromatic humic-like character. By means of an End-Member Mixing Analysis (EMMA) approach it was observed that in-stream reactive processes were likely to be driving DOM quality, especially during non-flood conditions and at the middle and lower reaches of La Tordera. Following such evidences, the relevance of in-stream transformations over transport and physical mixing were explicitly quantified by performing a mass balance approach at thirteen consecutive downstream segments. Results of the mass balance study showed that flood events, despite their brevity in time, had the capacity to export the largest amounts of DOM, although having undergone little in-stream processing. During baseflow conditions, which have been estimated to occur annually about half of the days, there were moderate efficiencies of bulk DOM retention; however, individual fluorescence components had important in-stream generations, especially the protein-like moieties C1 and C2. In space, this processing occurred in the final segments of the river, hence exhibiting a shift from a conservative to a reactive behaviour. Finally, during drought conditions the river had the highest capacity of DOM retention and exported the least amounts of DOM. In space, retention efficiencies were homogeneous along the mainstem, except for two anthropogenically-impacted sites where the retention capacities were reduced. The mass balance study also revealed that bulk DOC processing was subject to a stoichiometric control with nitrate, even though such control was weaker during drought. The findings of this thesis demonstrate that the riverine passage is a decisive step that defines the quantity and quality of the DOM that is finally delivered to the oceans. Moreover, the observed hydrological seasonality in La Tordera shapes a temporally-changing DOM character which may have complex repercussions for its fate once in the coastal systems

Diseño e implementación de robot prototipo para la inspección de tuberías en pozos petroleros (bombas de cavidad progresiva y bombas electro sumergibles)

En este trabajo se presenta el desarrollo de un robot basado en la estructura tensegrity con el fin de realizar tareas de inspección y mantenimiento en tuberías petroleras. Debido a la naturaleza de la aplicación, el robot debe ser capaz de desplazarse verticalmente por el exterior de una dicha tubería. Este tipo de estructura mecánica se caracteriza por su bajo peso y su alta capacidad de adaptación a los diferentes diámetros. La aplicación requiere que el dispositivo desarrollado se desplace a alta velocidad por las tuberías utilizadas en la extracción del petróleo. Cabe destacar que en dichas instalaciones se cuenta con Bombas Electro Sumergibles (BES) y Bombas de Cavidad Progresiva (BCP), ambas muy sensibles a las condiciones adversas del entorno. Consecuentemente se prevé que el robot incorpore una red de sensores específicos para medir aquellas variables que puedan interferir en el funcionamiento normal de las bombas. En este artículo se describen detalladamente las hipótesis de diseño realizadas y la metodología utilizada para el desarrollo del primer prototipo. Finalmente se presentan los resultados obtenidos de dicho desarrollo a través de los cuales se ha podido validar la potencialidad de la aplicación

Metodología para definir los criterios de diseño de una estructura robótica en tuberías petroleras de operación vertical

Este trabajo propone la aplicación de la metodología de despliegue de la función de calidad para definir los criterios de diseño de un robot deslizante para trabajar en tareas de inspección y mantenimiento en pozos petroleros. Dicho estudio analiza inicialmente el sistema y las diferentes opciones para la colocación de una estructura robótica evaluando alternativas y estudiando una estructura robótica para tal fin. Para ello se realizó una consulta por medio de encuesta a varios expertos en el tema con la finalidad de definir las características que debe tener el robot de acuerdo con los requerimientos críticos que tiene la aplicación. En este trabajo se muestran los resultados arrojados por la matriz QFD (Quality Function Deployment) cuando los datos de entrada son los proporcionados por el grupo de expertos encuestados. A partir de estos resultados es posible determinar los requisitos técnicos que debe reunir la estructura robótica que se desea diseñar

Experimental evidence reveals impact of drought periods on dissolved organic matter quality and ecosystem metabolism in subalpine streams

Subalpine streams are predicted to experience lower summer discharge following climate change and water extractions. In this study, we aimed to understand how drought periods impact dissolved organic matter (DOM) processing and ecosystem metabolism of subalpine streams. We mimicked a gradient of drought conditions in stream‐side flumes and evaluated implications of drought on DOM composition, gross primary production, and ecosystem respiration. Our experiment demonstrated a production and release of DOM from biofilms and leaf litter decomposition at low discharges, increasing dissolved organic carbon concentrations in stream water by up to 50%. Absorbance and fluorescence properties suggested that the released DOM was labile for microbial degradation. Dissolved organic carbon mass balances revealed a high contribution of internal processes to the carbon budget during low flow conditions. The flumes with low discharge were transient sinks of atmospheric CO2 during the first 2 weeks of drought. After this autotrophic phase, the metabolic balance of these flumes turned heterotrophic, suggesting a nutrient limitation for primary production, while respiration remained high. Overall our experimental findings suggest that droughts in subalpine streams will enhance internal carbon cycling by transiently increasing primary production and more permanently respiration as the drought persists. We propose that the duration of a drought period combined with inorganic nutrient availability are key variables that determine if more carbon is respired in situ or exported downstream

Quality and reactivity of dissolved organic matter in a Mediterranean river across hydrological and spatial gradients.

Understanding DOM transport and reactivity in rivers is essential to having a complete picture of the global carbon cycle. In this study, we explore the effects of hydrological variability and downstream transport on dissolved organic matter (DOM) dynamics in a Mediterranean river. We sampled the main stem of the river Tordera from the source to the sea, over a range of fifteen hydrological conditions including extreme events (flood and drought). By exploring spatial and temporal gradients of DOM fluorescence properties, river hydrology was found to be a significant predictor of DOM spatial heterogeneity. An additional space-resolved mass balance analysis performed on four contrasting hydrological conditions revealed that this was due to a shift in the biogeochemical function of the river. Flood conditions caused a conservative transport of DOM, generating a homogeneous, humic-like spatial profile of DOM quality. Lower flows induced a non-conservative, reactive transport of DOM, which enhanced the spatial heterogeneity of DOM properties. Moreover, the downstream evolution of DOM chemostatic behaviour revealed that the role of hydrology in regulating DOM properties increased gradually downstream, indicating an organised inter-dependency between the spatial and the temporal dimensions. Overall, our findings reveal that riverine DOM dynamics is in constant change owing to varying hydrological conditions, and emphasize that in order to fully understand the role of rivers in the global carbon cycle, it is necessary to take into account the full range of hydrological variability, from floods to droughts

Development of a novel autonomous robot for navigation and inspect in oil wells

This paper proposes a novel robotic system that is able to move along the outside of the oil pipelines used in Electric Submersible Pumps (ESP) and Progressive Cavity Pumps (PCP) applications. This novel design, called RETOV, proposes a light weight structure robot that can be equipped with sensors to measure environmental variables avoiding damage in pumps and wells. In this paper, the main considerations and methodology of design and implementation are discussed. Finally, the first experimental results that show RETOV moving in vertical pipelines are analyzed

Comparative analysis of tools to predict rapid progression in autosomal dominant polycystic kidney disease

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease and shows a wide phenotype. Only patients with rapid progression (RP) are included in clinical trials or are approved to receive disease-modifying drugs. This study aims at comparing different available predictive tools in ADPKD with the Mayo classification (MC) identification of rapid progressors based on high total kidney volume (TKV) according to age. Methods: A total of 164 ADPKD patients were recruited retrospectively from a single centre. The performance of diverse tools to identify RP defined as being in MC categories 1C-1E was assessed. Results: A total of 118 patients were MC 1C-1E. The algorithm developed by the European Renal Association-European Dialysis and Transplant Association Working Group on Inherited Kidney Disorders/European Renal Best Practice had a low sensitivity in identifying MC 1C-1E. The sensitivity and specificity of TKV to predict RP depend on the cut-off used. A kidney length of >16.5 cm before age 45 years has high specificity but low sensitivity. Assessing the MC by ultrasonography had high levels of agreement with magnetic resonance imaging (MRI) data, especially for 1A, 1D and 1E. The estimated glomerular filtration rate (eGFR) decline was very sensitive but had low specificity. In contrast, the Predicting Renal Outcome in Polycystic Kidney Disease (PROPKD) score was very specific but had poor sensitivity. Having hypertension before 35 years of age is a good clinical predictor of MC 1C-1E. Family history can be of help in suggesting RP, but by itself it lacks sufficient sensitivity and specificity. Conclusions: The MC by ultrasonography could be an option in hospitals with limited access to MRI as it performs well generally, and especially at the extremes of the MC, i.e. classes 1A, 1D and 1E. The eGFR decline is sensitive but not very specific when compared with the MC, whereas the PROPKD score is very specific but has low sensitivity. Integrating the different tools currently available to determine RP should facilitate the identification of rapid progressors among patients with ADPKD

Weight loss in obese patients with heart failure

BACKGROUND: In heart failure (HF), weight loss (WL) has been associated with an adverse prognosis whereas obesity has been linked to lower mortality (the obesity paradox). The impact of WL in obese patients with HF is incompletely understood. Our objective was to explore the prevalence of WL and its impact on long-term mortality, with an emphasis on obese patients, in a cohort of patients with chronic HF. METHODS AND RESULTS: Weight at first visit and the 1-year follow-up and vital status after 3 years were assessed in 1000 consecutive ambulatory, chronic HF patients (72.7% men; mean age 65.8±12.1 years). Significant WL was defined as a loss of ≥5% weight between baseline and 1 year. Obesity was defined as body mass index ≥30 kg/m(2) (N=272). Of the 1000 patients included, 170 experienced significant WL during the first year of follow-up. Mortality was significantly higher in patients with significant WL (27.6% versus 15.3%, P 0.001). In univariable Cox regression analysis, patients with significant WL had 2-fold higher mortality (hazard ratio 1.95 [95% CI 1.39-2.72], P 0.001). In multivariable analysis, adjusting for age, sex, body mass index, New York Heart Association functional class, left ventricular ejection fraction, HF duration, ischemic etiology, diabetes, and treatment, significant WL remained independently associated with higher mortality (hazard ratio 1.89 [95% CI 1.32-2.68], P 0.001). Among obese patients with HF, significant WL was associated with an even more ominous prognosis (adjusted hazard ratio for death of 2.38 [95% CI 1.31-4.32], P=0.004) than that observed in nonobese patients (adjusted hazard ratio 1.83 [95% CI 1.16-2.89], P=0.01). CONCLUSIONS: Weight loss ≥5% in patients with chronic HF was associated with high long-term mortality, particularly among obese patients with HF

Characteristics of the silhouettes of a range of hierarchical partitionings of the R-mode SOM grid.

<p>The silhouettes analysis <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099618#pone.0099618-Findlay1" target="_blank">[5]</a> corresponds to the calculation of for every object in the data set, where is a measurement of how well object matches its assigned cluster. corresponds to the average , to the minimum , to the maximum and to the number of objects that have a negative . Values of S near one indicate that the object is very well clustered, whereas negative S indicates that the object might be assigned to the wrong group.</p