Driving mechanisms for groundwater flow and salt transport in a subterranean estuary

This paper presents field measurements and numerical simulations of groundwater dynamics in the intertidal zone of a sandy meso-tidal beach. The study, focusing on vertical hydraulic gradients and pore water salinities, reveals that tides and waves provide important forcing mechanisms for flow and salt transport in the nearshore aquifer. Such forcing, interacting with the beach morphology, enhances the exchange between the aquifer and ocean. The spatial and temporal variations of vertical hydraulic gradients demonstrate the complexity and dynamic nature of the processes and the extent of mixing between fresh groundwater and seawater in a subterranean estuary''. These results provide evidence of a potentially important reaction zone in the nearshore aquifer driven by oceanic oscillations. Land-derived contaminants may undergo important biogeochemical transformations in this zone prior to discharge.

Coupling of eastern and western subpolar North Atlantic: salt transport in the Irminger Current

Salt transport in the Irminger Current and thus the coupling between eastern and western subpolar North Atlantic plays an important role for climate variability across a wide range of time scales. High-resolution ocean modeling and observations indicate that 5 salinities in the eastern subpolar North Atlantic decrease with enhanced circulation of the North Atlantic subpolar gyre (SPG). This has led to the perception that a stronger SPG also transports less salt westward. In this study, we analyze a regional ocean model and a comprehensive global coupled climate model, and show that a stronger SPG transports more salt in the Irminger Current irrespective of lower salinities in its 10 source region. The additional salt converges in the Labrador Sea and the Irminger Basin by eddy transports, increases surface salinity in the western SPG, and favors more intense deep convection. This is part of a positive feedback mechanism with potentially large implications for climate variability and predictability.

Study of biological desalination phenomena: salt transport mechanisms of selective avian salt glands,

Mode of access: Internet.

Hydrodynamics and suspended sediment transport in the Camboriú estuary - Brazil: pre jetty conditions

Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Camboriú estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Camboriú estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Camboriú estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments, periodically resuspended by the tidal currents. The advective salt and suspended sediment transport was different between neap and spring tides, being more complex at spring tide. The river discharge term was important under both tidal conditions. The tidal correlation term was also important, being dominant in the suspended sediment transport during the spring tide. The gravitational circulation and Stokes drift played a secondary role in the estuarine transport processes.

Sodium chloride added to transport water and physiological responses of Matrinxã Brycon amazonicus (Teleost: Characidae)

The addition of salt to the water has been used to mitigate stress and improve survival in fishes. This study investigated the effects of sodium chloride (0.0, 1.0, 3.0 and 6.0 g/l) on levels of plasma cortisol, glucose, tryacilglycerol, total protein, hematocrit, hemoglobin, erythrocyte number, liver glycogen and lipid, and muscle lipid in adult matrinxã(Brycon amazonicum) after a 4-h transport and during a 96-h recovery period. Fish were sampled before and after transport, and 24 and 96 h of the recovery period. Plasma cortisol was higher than initial condition immediately after transportation, except in fish transported in 3.0 and 6.0 g/l of salt. A similar pattern was observed for blood glucose but fish transported in water with 0.0, 1.0 and 3.0 g/l of salt needed more than 24 h to return to the initial condition. Liver glycogen was lower after transport in fish not exposed to salt. Hemoglobin, erythrocyte number, total plasma protein and liver lipid did not change during the experiment but hematocrit was lower after transport in all treatments and returned to pre-transport values in 24 h. Reductions of muscle lipid and plasma tryacilglycerol were observed during the recovery period in fish from all treatments. The results show that 6.0 g/l NaCl added to the transport water reduce the stress responses and a 96-h recovery period is needed if no salt is used to mitigate the stress.

Sodium chloride added to transport water and physiological responses of Matrinxã Brycon amazonicus (Teleost: Characidae)

A adição de sal à água tem sido utilizada para a mitigação de estresse e aumento da taxa de sobrevivência em peixes. O presente estudo avaliou o efeito do cloreto de sódio (0,0; 1,0; 3,0 e 6.0 g/l) nas concentrações de cortisol plasmático, glicemia, triglicerídios, proteínas total plasmática, hematócrito, hemoglobina, número de eritrócitos, glicogênio e lipídio hepáticos, e lipídio muscular em matrinxã Brycon amazonicum adultos após quatro horas de transporte e durante período de recuperação de 96 h. Amostras foram coletadas antes e depois do transporte, bem como 24 e 96 h após a chegada. O nível de cortisol plasmático estava mais elevado logo após o transporte quando comparado à condição inicial (pré-transporte), exceto para os peixes transportados com sal nas concentrações 3,0 e 6,0 g/l. Comportamento semelhante foi observado para a glicemia, porém os peixes dos tratamentos 0,0, 1,0 e 3,0 g/l necessitaram de período superior a 24 h para recuperar a condição inicial. Foram registrados níveis mais baixos de glicogênio hepático em peixes do tratamento controle (0,0 g/l). Os parâmetros hemoglobina, número de eritrócitos, proteína plasmática total e lipídio hepático não apresentaram alterações durante o período experimental. Os valores de hematócrito diminuíram logo após o transporte em todos os tratamentos, retornando aos níveis iniciais após 24 h. Todos os tratamentos apresentaram redução nos níveis de lipídio muscular e triglicerídios durante o período de recuperação. Os resultados sugerem que a adição de 6,0 g/l de sal na água de transporte reduz as alterações fisiológicas de estresse e que é necessário período de 96 h após o transporte para a recuperação da condição inicial de matrinxãs transportados sem a adição de sal.

Circulation and salt intrusion in the Piaçaguera Channel, Santos (SP)

A análise de dados termohalinos e correntes medidos em uma estação fixa no Canal de Piaçaguera (Estuário de Santos) no inverno foi feita em termos de condições cíclicas da maré (quadratura e sizígia) e quase-estacionária, com o objetivo de caracterizar a estratificação da massa de água estuarina, sua circulação e transporte de sal forçados pela modulação quinzenal da maré. Foram utilizados métodos clássicos de análise de dados observacionais horários e quase sinóticos e de simulações analíticas de perfis estacionários de salinidade e do componente longitudinal da velocidade. Durante o ciclo de maré de quadratura as velocidades de enchente (v<0) e vazante (v>0) variaram de -0.20 m/s a 0.30 m/s, associadas à pequena variação de salinidade entre a superfície e o fundo (26.4 psu a 30.7 psu). No ciclo de sizígia a velocidade aumentou de -0.40 m/s a 0.45 m/s, mas a estratificação de salinidade permaneceu praticamente a mesma. Os perfis estacionários teóricos de salinidade e de velocidade apresentaram boa concordância (Skill próximo a 1,0) quando comparados aos perfis observacionais. Durante a modulação quinzenal da maré não houve alteração na classificação do canal estuarino (tipo 2a-parcialmente misturado e fracamente estratificado), pois a taxa de aumento da energia potencial não foi suficiente para ocasionar a erosão da haloclina. Esses resultados, associados à alta estabilidade vertical (RiL >20) e ao número de Richardson estuarino (1,6), permitem as seguintes conclusões: i) o mecanismo que forçou a circulação e os processos de mistura foi principalmente o balanço da descarga fluvial com a maré, associado ao componente baroclínico da força de gradiente de pressão; ii) não houve variações nas principais características termohalinas e da circulação devido à modulação quinzenal da maré; e iii) os perfis quase estacionários de salinidade e da velocidade foram adequadamente simulados com um modelo analítico clássico.

HYDRODYNAMICS AND SUSPENDED SEDIMENT TRANSPORT IN THE CAMBORIU ESTUARY - BRAZIL: PRE JETTY CONDITIONS

Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Cambori estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Cambori estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Cambori estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments, periodically resuspended by the tidal currents. The advective salt and suspended sediment transport was different between neap and spring tides, being more complex at spring tide. The river discharge term was important under both tidal conditions. The tidal correlation term was also important, being dominant in the suspended sediment transport during the spring tide. The gravitational circulation and Stokes drift played a secondary role in the estuarine transport processes.

CIRCULATION AND SALT INTRUSION IN THE PIACAGUERA CHANNEL, SANTOS (SP)

Analysis of thermohaline properties and currents sampled at an anchor station in the Piacaguera Channel (Santos Estuary) in the austral winter was made in terms of tidal (neap and spring tidal cycles) and non-tidal conditions, with the objective to characterize the stratification, circulation and salt transport due to the fortnightly tidal modulation. Classical methods of observational data analysis of hourly and nearly synoptic observations and analytical simulations of nearly steady-state salinity and longitudinal velocity profiles were used. During the neap tidal cycle the flood (v<0) and ebb (v>0) velocities varied in the range of -0.20 m/s to 0.30 m/s associated with a small salinity variation from surface to bottom (26.4 psu to 30.7 psu). In the spring tidal cycle the velocities increased and varied in the range of -0.40 m/s to 0.45 m/s, but the salinity stratification remained almost unaltered. The steady-state salinity and velocity profiles simulated with an analytical model presented good agreement (Skill near 1.0), in comparison with the observational profiles. During the transitional fortnightly tidal modulation period there was no changes in the channel classification (type 2a - partially mixed and weakly stratified), because the potential energy rate was to low to enhance the halocline erosion. These results, associated with the high water column vertical stability (RiL > 20) and the low estuarine Richardson number (RiE = 1.6), lead to the conclusions: i) the driving mechanism for the estuary circulation and mixing was mainly balanced by the fresh water discharge and the tidal forcing associated with the baroclinic component of the gradient pressure force; ii) there was no changes in the thermohaline and circulation characteristics due to the forthnigtly tidal modulation; and iii) the nearly steady-state of the vertical salinity and velocity profiles were well simulated with a theoretical classical analytical model.

Circulation and salt intrusion in the Piaçaguera Channel, Santos (SP)

Analysis of thermohaline properties and currents sampled at an anchor station in the Piaçaguera Channel (Santos Estuary) in the austral winter was made in terms of tidal (neap and spring tidal cycles) and non-tidal conditions, with the objective to characterize the stratification, circulation and salt transport due to the fortnightly tidal modulation. Classical methods of observational data analysis of hourly and nearly synoptic observations and analytical simulations of nearly steady-state salinity and longitudinal velocity profiles were used. During the neap tidal cycle the flood (v<0) and ebb (v>0) velocities varied in the range of -0.20 m/s to 0.30 m/s associated with a small salinity variation from surface to bottom (26.4 psu to 30.7 psu). In the spring tidal cycle the velocities increased and varied in the range of -0.40 m/s to 0.45 m/s, but the salinity stratification remained almost unaltered. The steady-state salinity and velocity profiles simulated with an analytical model presented good agreement (Skill near 1.0), in comparison with the observational profiles. During the transitional fortnightly tidal modulation period there was no changes in the channel classification (type 2a - partially mixed and weakly stratified), because the potential energy rate was to low to enhance the halocline erosion. These results, associated with the high water column vertical stability (RiL >20) and the low estuarine Richardson number (RiE=1.6), lead to the conclusions: i) the driving mechanism for the estuary circulation and mixing was mainly balanced by the fresh water discharge and the tidal forcing associated with the baroclinic component of the gradient pressure force; ii) there was no changes in the thermohaline and circulation characteristics due to the forthnigtly tidal modulation; and iii) the nearly steady-state of the vertical salinity and velocity profiles were well simulated with a theoretical classical analytical model.

Electrolyte transport in the mammalian colon: mechanisms and implications for disease Kunzelmann and Marcus Mall

Electrolyte Transport in the Mammalian Colon: Mechanisms and Implications for Disease. Physiol. Rev. 82: 245-289, 2002.The colonic epithelium has both absorptive and secretory functions. The transport is characterized by a net absorption of NaCl, short-chain fatty acids (SCFA), and water, allowing extrusion of a feces with very little water and salt content. In addition, the epithelium does secret mucus, bicarbonate, and KCl. Polarized distribution of transport proteins in both luminal and basolateral membranes enables efficient salt transport in both directions, probably even within an individual cell. Meanwhile, most of the participating transport proteins have been identified, and their function has been studied in detail. Absorption of NaCl is a rather steady process that is controlled by steroid hormones regulating the expression of epithelial Na+ channels (ENaC), the Na+-K+-ATPase, and additional modulating factors such as the serum- and glucocorticoid-regulated kinase SGK. Acute regulation of absorption may occur by a Na+ feedback mechanism and the cystic fibrosis transmembrane conductance regulator (CFTR). Cl- secretion in the adult colon relies on luminal CFTR, which is a cAMP-regulated Cl- channel and a regulator of other transport proteins. As a consequence, mutations in CFTR result in both impaired Cl- secretion and enhanced Na+ absorption in the colon of cystic fibrosis (CF) patients. Ca2+- and cAMP-activated basolateral K+ channels support both secretion and absorption of electrolytes and work in concert with additional regulatory proteins, which determine their functional and pharmacological profile. Knowledge of the mechanisms of electrolyte transport in the colon enables the development of new strategies for the treatment of CF and secretory diarrhea. It will also lead to a better understanding of the pathophysiological events during inflammatory bowel disease and development of colonic carcinoma.

Sodium chloride added to transport water and physiological responses of Matrinxã Brycon amazonicus (Teleost: Characidae)

A adição de sal à água tem sido utilizada para a mitigação de estresse e aumento da taxa de sobrevivência em peixes. O presente estudo avaliou o efeito do cloreto de sódio (0,0; 1,0; 3,0 e 6.0 g/l) nas concentrações de cortisol plasmático, glicemia, triglicerídios, proteínas total plasmática, hematócrito, hemoglobina, número de eritrócitos, glicogênio e lipídio hepáticos, e lipídio muscular em matrinxã Brycon amazonicum adultos após quatro horas de transporte e durante período de recuperação de 96 h. Amostras foram coletadas antes e depois do transporte, bem como 24 e 96 h após a chegada. O nível de cortisol plasmático estava mais elevado logo após o transporte quando comparado à condição inicial (pré-transporte), exceto para os peixes transportados com sal nas concentrações 3,0 e 6,0 g/l. Comportamento semelhante foi observado para a glicemia, porém os peixes dos tratamentos 0,0, 1,0 e 3,0 g/l necessitaram de período superior a 24 h para recuperar a condição inicial. Foram registrados níveis mais baixos de glicogênio hepático em peixes do tratamento controle (0,0 g/l). Os parâmetros hemoglobina, número de eritrócitos, proteína plasmática total e lipídio hepático não apresentaram alterações durante o período experimental. Os valores de hematócrito diminuíram logo após o transporte em todos os tratamentos, retornando aos níveis iniciais após 24 h. Todos os tratamentos apresentaram redução nos níveis de lipídio muscular e triglicerídios durante o período de recuperação. Os resultados sugerem que a adição de 6,0 g/l de sal na água de transporte reduz as alterações fisiológicas de estresse e que é necessário período de 96 h após o transporte para a recuperação da condição inicial de matrinxãs transportados sem a adição de sal.

Repair mortars for rammed earth constructions

Proceedingsof the XII DBMC – 12th International Conference on Durability of Building Materials and Components, Vol.2, Porto, FEUP, March 2011, p.689-696

Decadal predictions of the cooling and freshening of the North Atlantic in the 1960s and the role of ocean circulation

In the 1960s North Atlantic sea surface temperatures (SST) cooled rapidly. The magnitude of the cooling was largest in the North Atlantic subpolar gyre (SPG), and was coincident with a rapid freshening of the SPG. Here we analyze hindcasts of the 1960s North Atlantic cooling made with the UK Met Office’s decadal prediction system (DePreSys), which is initialised using observations. It is shown that DePreSys captures—with a lead time of several years—the observed cooling and freshening of the North Atlantic SPG. DePreSys also captures changes in SST over the wider North Atlantic and surface climate impacts over the wider region, such as changes in atmospheric circulation in winter and sea ice extent. We show that initialisation of an anomalously weak Atlantic Meridional Overturning Circulation (AMOC), and hence weak northward heat transport, is crucial for DePreSys to predict the magnitude of the observed cooling. Such an anomalously weak AMOC is not captured when ocean observations are not assimilated (i.e. it is not a forced response in this model). The freshening of the SPG is also dominated by ocean salt transport changes in DePreSys; in particular, the simulation of advective freshwater anomalies analogous to the Great Salinity Anomaly were key. Therefore, DePreSys suggests that ocean dynamics played an important role in the cooling of the North Atlantic in the 1960s, and that this event was predictable.