Field and numerical study of solute transport under evaporation in a subtropical tidal wetland

2021 ◽  
Author(s):  
Yue Liu ◽  
Chenming Zhang ◽  
Xiaocheng Liu ◽  
Ling Li ◽  
Alexander Scheuermann ◽  
...  
Keyword(s):  
Solute Transport ◽  
Transport Model ◽  
Root Zone ◽  
Numerical Study ◽  
Soil Surface ◽  
Distribution Patterns ◽  
Tidal Wetland ◽  
Wetland Ecology ◽  
Salt Distribution ◽  
The Impact

<p>Tidal wetlands are critical intertidal ecosystem which accommodates a large range of flora and fauna species. The intertidal subsurface environment is subjected to continuous groundwater-seawater mixing which results in dynamic solute transport in the aquifer and to the ocean. Salt distribution and transport play a vital role in the wetland ecology and near-shore biogeochemical activities. While many field and simulation studies have been presented to characterize the salt distribution in the intertidal beach aquifer under the influence of tidal inundation, salt distribution in the tidal wetland subsurface system yet requires more investigation. Moreover, the impact of evaporation on porewater salt distribution could be essential in subtropical areas with numerous coastal wetlands as evaporation extracts porewater from the soil surface and leaves salt in the surface and wetland root zone. However, this parameter was commonly ignored by previous studies.</p><p>In this study, field monitoring was carried out to map the groundwater level and spatial salt distribution in a subtropical wetland located in Southeastern Queensland, Australia. Two dimensional, variable-density, saturated-unsaturated groundwater flow and solute transport model was used to examine the pore water flow and salt distribution patterns in a cross-shore section of the field site under the influences of the spring-neap tide and evaporation. Field and simulation results consistently showed that salinity is greatly impacted by evaporation and showed different distributions from the saline seawater intrusion patterns displayed by most of the former studies. </p>

scholarly journals Analytical and numerical study of the salinity intrusion in the Sebou river estuary (Morocco). Effect of the "Super Blood Moon" (total lunar eclipse) of 2015

2016 ◽  
Author(s):  
Soufiane Haddout ◽  
Mohammed Igouzal ◽  
Abdellatif Maslouhi
Keyword(s):  
Extreme Event ◽  
Transport Model ◽  
Numerical Study ◽  
Rapid Assessment ◽  
River Estuary ◽  
Lunar Eclipse ◽  
Salinity Intrusion ◽  
Salt Intrusion ◽  
Salinity Transport ◽  
The Impact

Abstract. The longitudinal variation of salinity and the maximum salinity intrusion length in an alluvial estuary are important environmental concerns for policy makers and managers since they influence water quality, water utilization and agricultural development in estuarine environments and the potential use of water resources in general. Total eclipses of Super-Moons are rare. According to NASA, they have only occurred five times in the 1900s – in 1910, 1928, 1946, 1964 and 1982. After the 28 September 2015 Total lunar eclipse, a Super-Bloodmoon eclipse will not recur before 8 October 2033. In this paper, for the first time, the impact of the total lunar eclipse (Super Blood Moon) on the salinity intrusion along an estuary is studied. The 28 September 2015 total lunar eclipse is focused by the study and the Sebou river estuary (Morocco) is taking as an application area. The Sebou estuary is an area with high agricultural potential, is becoming one of the most important industrial zones in Morocco and it is experiencing a salt intrusion problem. Hydrodynamic equations for tidal wave propagation coupled with (Savenije theory), and a numerical salinity transport model (HEC-RAS) are applied to study the impact of the total lunar eclipse on the salinity intrusion. Intensive salinity measurements during this extreme event were recorded along the Sebou estuary. Measurements showed a modification of the shape of axial salinity profiles and a notable water elevation rise, compared with normal situations. The two optimization parameters (Van Der Burgh's and dispersion coefficients) of the analytical model are estimated based on the Levenberg–Marquardt's algorithm (i.e. solving non-linear least squares problems). The salinity transport model was calibrated and validated using field data. The results show that the two models described very well salt intrusion during the total lunar eclipse day. A good-fit between computed salinity and measurements is obtained, as verified by statistical performance tests. These two models can give a rapid assessment of salinity distribution and consequently help to ensure the safety of water supply, even during such infrequent astronomical phenomenon.

Modelling of the impact of future climate changes on salt accumulation in paddocks of different soil types due to recycled water irrigation

2015 ◽  
Vol 16 (3) ◽  
pp. 653-666 ◽  
Author(s):  
Muhammad Muhitur Rahman ◽  
Dharma Hagare ◽  
Basant Maheshwari ◽  
Peter Dillon ◽  
Golam Kibria
Keyword(s):  
Transport Model ◽  
Root Zone ◽  
Global Climate Model ◽  
Salt Transport ◽  
Loamy Sand ◽  
Recycled Water ◽  
Salt Accumulation ◽  
Loam Soil ◽  
The Impact

Recycled water contains elevated amounts of salt compared with irrigation water originating from surface water sources. As such, recycled water, if used for irrigation over a long period of time may increase the root zone salinity. However, the phenomenon depends on variability of climatic condition and soil characteristics. In this study, a salt transport model, HYDRUS 1D, was used to predict long-term salt accumulation in two paddocks containing loamy sand and loam soil. The paddocks are located within Western Sydney University, Hawkesbury campus. Impact of rainfall on salt accumulation was studied with the data from the Global Climate Model for the years 2021–2040. The long-term (20 years) salt accumulation showed a cyclical pattern because of variation in rainfall and evapotranspiration. It was found that soil water electrical conductivity (ECSW) was 24% higher in loam soil paddock compared with that of loamy sand. Amount of leachate in the loamy sand paddock was 27% more than the amount leached from that of loam, which may pose a salinity risk to the groundwater if there is a perched aquifer in the field at a depth <1 m. Results from this study indicate that salt accumulation depends on soil type which seems to be more pronounced under low rainfall condition.

A Numerical Study of the Impact of Tunnel Depth on Surface Displacement in Shield Tunnel Construction

2013 ◽  
Vol 423-426 ◽  
pp. 1248-1252
Author(s):  
Hui Ting Zhan ◽  
Hong Yuan ◽  
Jia Yu Wu ◽  
Yu Sen Yuan
Keyword(s):  
Numerical Study ◽  
Surface Displacement ◽  
Soil Surface ◽  
Rate Of Change ◽  
Shield Tunnel ◽  
Tunnel Construction ◽  
Displacement Curve ◽  
3D Finite Element Method ◽  
Tunnel Depth ◽  
The Impact

Using 3d finite element method can simulate the process of shield tunnel construction. The paper studies the impact of different tunnel depth on the deformation of soil, when considering different excavation steps in the process of tunnel construction. The results show that the shallower the tunnel depth, and the greater the amount of the surface displacement during the tunnel construction. In the process of the tunnel excavation, the soil surface displacement in front of the shield machine is the result of superposition of the uplift and subsidence. When the tunnel depth increases, the surface displacement curve becomes smoother, and the rate of change becomes slower.

Numerical assessment of chemical species infiltration in the Prosecco area

2020 ◽  
Author(s):  
Leonardo Costa ◽  
Stefano Mazzega Ciamp ◽  
Alessandra Cardinali ◽  
Laura Carretta ◽  
Nicola Dal Ferro ◽  
...  
Keyword(s):  
Field Experiments ◽  
Transport Model ◽  
Root Zone ◽  
Chemical Species ◽  
Agricultural Practices ◽  
Laboratory Analysis ◽  
Subsurface Water ◽  
Human Consumption ◽  
North East ◽  
The Impact

<p>The multidisciplinary research project SWAT - Subsurface Water quality and Agricultural pracTices monitoring - has been set up to assess pesticides contamination risks for groundwater in the hills of Prosecco in the north-east of Italy. The unconfined aquifer underneath the typical Glera grape-variety vineyards of Valdobbiadene and Conegliano is used as water supply resource for human consumption. The principal aim of the project SWAT is to obtain a thorough information on the impact of contaminants coming from agricultural practices and infiltrating in the soil of well protection areas. Based on specifically designed field experiments, a study on water and solutes infiltration process is developed to understand the movement and evolution of chemical species in the vadose zone. A one-dimensional transport model for unsaturated media (BRTSim - Maggi, 2015) is used to simulate solute infiltration and estimate the soil hydraulic parameters. Monitoring activities started in November 2018 in two experimental sites (the Settolo site in Valdobbiadene and the Colnù site in Conegliano) near supply wells surrounded by vineyards. A mixture of Bromide and Glyphosate was identically applied on two parcels of 25 m<sup>2</sup> for each experimental site to obtain information about spatial heterogeneity and to collect independently water and soil quality measurements. Porous cups, for the collection of infiltrating water, and capacitive sensors, to gauge temperature and Volumetric Water Content (VWC), were installed beneath the sectors at three depths (-0.1, -0.3, -0.7 m). In each site meteorological station provides hydrological data. At first, laboratory analysis on soil samples collected at the same depths gave a vertical distribution of the sector-specific soil texture that was used as input for Rosetta to obtain initial estimations of retention curve behaviour and the saturated hydraulic conductivity. These data allowed us to develop an open-loop simulation using the early meteorological observations as hydrological forcing. As the laboratory analysis on soil and water samples proceed and the number of in-situ measurements increases, different data windows are tested to improve the performances of the calibration procedure performed using PEST. In all tests a spin-up procedure is applied to mitigate the dependency of the results on the imposed initial data by repeating the first month of hydrological forcing three times. The results of the transport model using Rosetta parameters are already satisfactory in terms of VWC trends even if they are considerably shifted respect to the measured values. The calibration reduces the gap between model results and observations, but the behaviour seems to get worse in dry conditions. Improvements are achieved in the upper layer (-0.3 m) applying evapotranspiration along the root zone. The Bromide simulations agree with the infiltration behaviour: its movement is well represented up to -0.3 m, while at -0.7 m the observed values are overestimated. Ongoing investigations on the glyphosate dispersion process show limited infiltrating mass in the water collected samples.</p>

scholarly journals Analytical and numerical study of the salinity intrusion in the Sebou river estuary (Morocco) – effect of the “Super Blood Moon” (total lunar eclipse) of 2015

2016 ◽  
Vol 20 (9) ◽  
pp. 3923-3945 ◽  
Author(s):  
Soufiane Haddout ◽  
Mohammed Igouzal ◽  
Abdellatif Maslouhi
Keyword(s):  
Extreme Event ◽  
Transport Model ◽  
Numerical Study ◽  
Rare Event ◽  
River Estuary ◽  
Lunar Eclipse ◽  
Salinity Intrusion ◽  
Salt Intrusion ◽  
Salinity Transport ◽  
The Impact

Abstract. The longitudinal variation of salinity and the maximum salinity intrusion length in an alluvial estuary are important environmental concerns for policy makers and managers since they influence water quality, water utilization and agricultural development in estuarine environments and the potential use of water resources in general. The supermoon total lunar eclipse is a rare event. According to NASA, they have only occurred 5 times in the 1900s – in 1910, 1928, 1946, 1964 and 1982. After the 28 September 2015 total lunar eclipse, a Super Blood Moon eclipse will not recur before 8 October 2033. In this paper, for the first time, the impact of the combination of a supermoon and a total lunar eclipse on the salinity intrusion along an estuary is studied. The 28 September 2015 supermoon total lunar eclipse is the focus of this study and the Sebou river estuary (Morocco) is used as an application area. The Sebou estuary is an area with high agricultural potential, is becoming one of the most important industrial zones in Morocco and it is experiencing a salt intrusion problem. Hydrodynamic equations for tidal wave propagation coupled with the Savenije theory and a numerical salinity transport model (HEC-RAS software "Hydrologic Engineering Center River Analysis System") are applied to study the impact of the supermoon total lunar eclipse on the salinity intrusion. Intensive salinity measurements during this extreme event were recorded along the Sebou estuary. Measurements showed a modification of the shape of axial salinity profiles and a notable water elevation rise, compared with normal situations. The two optimization parameters (Van der Burgh's and dispersion coefficients) of the analytical model are estimated based on the Levenberg–Marquardt's algorithm (i.e., solving nonlinear least-squares problems). The salinity transport model was calibrated and validated using field data. The results show that the two models described very well the salt intrusion during the supermoon total lunar eclipse day. A good fit between computed salinity and measurements is obtained, as verified by statistical performance tests. These two models can give a rapid assessment of salinity distribution and consequently help to ensure the safety of the water supply, even during such infrequent astronomical phenomenon.

HOW CLIMATE CHANGE CAN INFLUENCE THE AGRICULTURE IN UKRAINE: A REVIEW

2020 ◽  
Author(s):  
N. Maidanovych ◽  
Keyword(s):  
Climate Change ◽  
Crop Yields ◽  
Soil Surface ◽  
Winter Period ◽  
Negative Consequences ◽  
Resource Saving ◽  
Impact Of Climate Change ◽  
Positive Effects ◽  
Average Annual Temperature ◽  
The Impact

The purpose of this work is to review and analyze the main results of modern research on the impact of climate change on the agro-sphere of Ukraine. Results. Analysis of research has shown that the effects of climate change on the agro-sphere are already being felt today and will continue in the future. The observed climate changes in recent decades have already significantly affected the shift in the northern direction of all agro-climatic zones of Europe, including Ukraine. From the point of view of productivity of the agro-sphere of Ukraine, climate change will have both positive and negative consequences. The positives include: improving the conditions of formation and reducing the harvesting time of crop yields; the possibility of effective introduction of late varieties (hybrids), which require more thermal resources; improving the conditions for overwintering crops; increase the efficiency of fertilizer application. Model estimates of the impact of climate change on wheat yields in Ukraine mainly indicate the positive effects of global warming on yields in the medium term, but with an increase in the average annual temperature by 2 ° C above normal, grain yields are expected to decrease. The negative consequences of the impact of climate change on the agrosphere include: increased drought during the growing season; acceleration of humus decomposition in soils; deterioration of soil moisture in the southern regions; deterioration of grain quality and failure to ensure full vernalization of grain; increase in the number of pests, the spread of pathogens of plants and weeds due to favorable conditions for their overwintering; increase in wind and water erosion of the soil caused by an increase in droughts and extreme rainfall; increasing risks of freezing of winter crops due to lack of stable snow cover. Conclusions. Resource-saving agricultural technologies are of particular importance in the context of climate change. They include technologies such as no-till, strip-till, ridge-till, which make it possible to partially store and accumulate mulch on the soil surface, reduce the speed of the surface layer of air and contribute to better preservation of moisture accumulated during the autumn-winter period. And in determining the most effective ways and mechanisms to reduce weather risks for Ukrainian farmers, it is necessary to take into account the world practice of climate-smart technologies.

scholarly journals Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils

2020 ◽  
Vol 18 (1) ◽  
pp. 232-238
Author(s):  
Zhihong Zhang ◽  
Gailei Tian ◽  
Lin Han
Keyword(s):  
Solute Transport ◽  
Transport Model ◽  
Fluid Velocity ◽  
Diffusion Mechanism ◽  
Clay Material ◽  
Chemical Osmosis ◽  
Advection Diffusion Equation ◽  
Test Study ◽  
Proposed Model ◽  
Membrane Effect

AbstractSolute transport through the clay liner is a significant process in many waste landfills or unmanaged landfills. At present, researchers mainly focus on the test study about semi-membrane property of clay material, however, the influence of chemical osmosis caused by membrane effect on solute transport and fluid velocity is insufficient. In this investigation, based on the classical advection-diffusion equation, a one-dimensional solute transport model for low-permeable clay material has been proposed, in which the coupled fluid velocity related with hydraulic gradient and concentration gradient is introduced, and the semi-membrane effect is embodied in the diffusion mechanism. The influence of chemical osmosis on fluid velocity and solute transport has been analyzed using COMSOL Multiphysics software. The simulated results show that chemical osmosis has a significant retarded action on fluid velocity and pollutant transport. The proposed model can effectively reveal the change in process of coupled fluid velocity under dual gradient and solute transport, which can provide a theoretical guidance for similar fluid movement in engineering.

scholarly journals Development of a Component-Level Hydrogen Transport Model with OpenFOAM and Application to Tritium Transport Inside a DEMO HCPB Breeder

2021 ◽  
Vol 11 (8) ◽  
pp. 3481
Author(s):  
Volker Pasler ◽  
Frederik Arbeiter ◽  
Christine Klein ◽  
Dmitry Klimenko ◽  
Georg Schlindwein ◽  
...  
Keyword(s):  
Transport Model ◽  
Tritium Concentration ◽  
Minor Role ◽  
Specific Rate ◽  
Component Level ◽  
Diffusion Limited ◽  
Purge Gas ◽  
Choice Of Species ◽  
The Impact ◽  
Tritium Transport

This work continues the development of a numerical model to simulate transient tritium transport on the breeder zone (BZ) level for the EU helium-cooled pebble bed (HCPB) concept for DEMO. The basis of the model is the open-source field operation and manipulation framework, OpenFOAM. The key output quantities of the model are the tritium concentration in the purge gas and in the coolant and the tritium inventory inside the BZ structure. New model features are briefly summarized. As a first relevant application a simulation of tritium transport for a single pin out of the KIT HCPB design for DEMO is presented. A variety of scenarios investigates the impact of the permeation regime (diffusion-limited vs. surface-limited), of an additional hydrogen content of 300 Pa H2 in the purge gas, of the released species (HT vs. T2), and of the choice of species-specific rate constants (recombination constant of HT set twice as for H2 and T2). The results indicate that the released species plays a minor role for permeation. Both permeation and inventory show a considerable dependence on a possible hydrogen addition in the purge gas. An enhanced HT recombination constant reduces steel T inventories and, in the diffusion-limited case, also permeation significantly. Scenarios with 80 bar vs. 2 bar purge gas pressure indicate that purge gas volumetric flow is decisive for permeation.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

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