scholarly journals Understanding the Relative Importance of Vertical and Horizontal Flow in Ice-Wedge Polygons

2019 ◽  
Author(s):  
Nathan A. Wales ◽  
Jesus D. Gomez-Velez ◽  
Brent D. Newman ◽  
Cathy J. Wilson ◽  
Baptiste Dafflon ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Horizontal Flow ◽  
Relative Importance ◽  
Water Fluxes ◽  
Field Scale ◽  
Flow And Transport ◽  
Hydrological Characteristics ◽  
Warming Climate ◽  
Conservative Tracer ◽  
Ice Wedge

Abstract. Ice-wedge polygons are common Arctic landforms. The future of these landforms in a warming climate depends on the bidirectional feedback between the rate of ice-wedge degradation and changes in hydrological characteristics. This work aims to better understand the relative roles of vertical and horizontal water fluxes in the subsurface of polygonal landscapes, providing new insights and data to test and calibrate hydrology models. Field-scale investigations were conducted at an intensively-instrumented location on the Barrow Environmental Observatory (BEO) near Utqiaġvik, AK, USA. Using a conservative tracer, we examined controls of microtopography and the frost table on subsurface flow and transport within a low-centered and a high-centered polygon. Bromide tracer was applied at both polygons in July 2015 and transport was monitored through two thaw seasons. Samplers arrays placed in polygon centers, rims, and troughs were used to monitor tracer concentrations. In both polygons, the tracer first infiltrated vertically until encountering the frost table, then was transported horizontally. Horizontal flow occurred in more locations and at higher velocities of fluxes in the low-centered polygon than in the high-centered polygon. Preferential flow, influenced by frost table topography, was significant between polygon centers and troughs. Estimates of horizontal hydraulic conductivity were within the range of previous estimates of vertical conductivity, highlighting the importance of horizontal flow in these systems. This work forms a basis for understanding complexity of flow in polygonal landscapes.

scholarly journals Understanding the relative importance of vertical and horizontal flow in ice-wedge polygons

2020 ◽  
Vol 24 (3) ◽  
pp. 1109-1129 ◽  
Author(s):  
Nathan A. Wales ◽  
Jesus D. Gomez-Velez ◽  
Brent D. Newman ◽  
Cathy J. Wilson ◽  
Baptiste Dafflon ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Horizontal Flow ◽  
Relative Importance ◽  
Hydrological Models ◽  
Water Fluxes ◽  
Flow And Transport ◽  
Hydrological Characteristics ◽  
Warming Climate ◽  
Conservative Tracer ◽  
Ice Wedge

Abstract. Ice-wedge polygons are common Arctic landforms. The future of these landforms in a warming climate depends on the bidirectional feedback between the rate of ice-wedge degradation and changes in hydrological characteristics. This work aims to better understand the relative roles of vertical and horizontal water fluxes in the subsurface of polygonal landscapes, providing new insights and data to test and calibrate hydrological models. Field-scale investigations were conducted at an intensively instrumented location on the Barrow Environmental Observatory (BEO) near Utqiaġvik, AK, USA. Using a conservative tracer, we examined controls of microtopography and the frost table on subsurface flow and transport within a low-centered and a high-centered polygon. Bromide tracer was applied at both polygons in July 2015 and transport was monitored through two thaw seasons. Sampler arrays placed in polygon centers, rims, and troughs were used to monitor tracer concentrations. In both polygons, the tracer first infiltrated vertically until encountering the frost table and was then transported horizontally. Horizontal flow occurred in more locations and at higher velocities in the low-centered polygon than in the high-centered polygon. Preferential flow, influenced by frost table topography, was significant between polygon centers and troughs. Estimates of horizontal hydraulic conductivity were within the range of previous estimates of vertical conductivity, highlighting the importance of horizontal flow in these systems. This work forms a basis for understanding complexity of flow in polygonal landscapes.

scholarly journals Field experimental design for pesticide leaching – a modified large-scale lysimeter

2005 ◽  
Vol 7 ◽  
pp. 41-44
Author(s):  
Bertel Nilsson ◽  
Jens Aamand ◽  
Ole Stig Jacobsen ◽  
René K. Juhler
Keyword(s):  
Large Scale ◽  
Preferential Flow ◽  
Fracture Network ◽  
Transport Processes ◽  
Natural Fracture ◽  
Field Scale ◽  
Flow Paths ◽  
Undisturbed Soil ◽  
Flow And Transport ◽  
Preferential Flow Paths

Recent research on Danish groundwater has focused on clarifying the fate and transport of pesticides that leach through clayey till aquitards with low matrix permeability. Previously, these aquitards were considered as protective layers against contamination of underlying groundwater aquifers due to their low permeability characteristics. However, geological heterogeneities such as fractures and macropores have been recognised as preferential flow paths within low permeable clayey till (e.g. Beven & Germann 1982). The flow velocities within these preferential flow paths can be orders of magnitude higher than in the surrounding clay matrix and pose a major risk of transport of contaminants to the underlying aquifers (e.g. Nilsson et al. 2001). Previous studies of transport in fractured clayey till have focused on fully saturated conditions (e.g. Sidle et al. 1998; McKay et al. 1999). However, seasonal fluctuations of the groundwater table typically result in unsaturated conditions in the upper few metres of the clay deposits, resulting in different flow and transport conditions. Only a few experiments have examined the influence of unsaturated conditions on flow and solute (the dissolved inorganic and organic constituents) transport in fractured clayey till. These include smallscale laboratory column experiments on undisturbed soil monoliths (e.g. Jacobsen et al. 1997; Jørgensen et al. 1998), intermediate scale lysimeters (e.g. Fomsgaard et al. 2003) and field-scale tile drain experiments (e.g. Kjær et al. 2005). The different approaches each have limitations in terms of characterising flow and transport in fractured media. Laboratory studies of solute transport in soils (intact soil columns) are not exactly representative of field conditions due to variations in spatial variability and soil structure. In contrast, field studies hardly allow quantification of fluxes and mechanisms of transport. Column and lysimeter experiments are often limited in size, and tile-drain experiments on field scale do not provide spatial resolution and often have large uncertainties in mass balance calculations. Thus, in order to represent the overall natural fracture network systems on a field scale with respect to acquiring insights into flow and transport processes, the lysimeter needs to be larger than normal lysimeter size (< 1 m3). A modified large-scale lysimeter was therefore constructed by the Geological Survey of Denmark and Greenland (GEUS) at the Avedøre experimental field site 15 km south of Copenhagen (Fig. 1). This lysimeter consisted of an isolated block (3.5 ×3.5 ×3.3 m) of unsaturated fractured clayey till with a volume sufficient to represent the overall preferential flow paths (natural fracture network) within lowpermeable clayey till at a field scale.

Field-scale variation of preferential flow as indicated from dye coverage

2002 ◽  
Vol 257 (1-4) ◽  
pp. 164-173 ◽  
Author(s):  
P Öhrström ◽  
M Persson ◽  
J Albergel ◽  
P Zante ◽  
S Nasri ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Field Scale ◽  
Scale Variation

Characterization of hydraulic properties in the upper vadose zone for two aquifers in Slovenia

2021 ◽  
Author(s):  
Vesna Zupanc ◽  
Matjaž Glavan ◽  
Miha Curk ◽  
Urša Pečan ◽  
Michael Stockinger ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Soil Water ◽  
Water Flow ◽  
Vadose Zone ◽  
Hydraulic Properties ◽  
Isotope Composition ◽  
Transport Processes ◽  
Precipitation Event ◽  
Water Fluxes ◽  
Flow And Transport

&lt;p&gt;Environmental tracers, present in the environment and provided by nature, provide integrative information about both water flow and transport. For studying water flow and solute transport, the hydrogen and oxygen isotopes are of special interest, as their ratios provide a tracer signal with every precipitation event and are seasonally distributed. In order to follow the seasonal distribution of stable isotopes in the soil water and use this information for identifying hydrological processes and hydraulic properties, soil was sampled three times in three profiles, two on Kr&amp;#353;ko polje aquifer in SE Slovenia and one on Ljubljansko polje in central Slovenia. Isotope composition of soil water was measured with the water-vapor-equilibration method. Based on the isotope composition of soil water integrative information about water flow and transport processes with time and depth below ground were assessed. Porewater isotopes were in similar range as precipitation for all three profiles. &amp;#160;Variable isotope ratios in the upper 60 cm for the different sampling times indicated dynamic water fluxes in this upper part of the vadose zone. Results also showed more evaporation at one sampling location, Brege. The information from stable isotopes will be of importance for further analyzing the water fluxes in the vadose zone of the study sties.&amp;#160;&lt;br&gt;This research was financed by the ARRS BIAT 20-21-32 and IAEA CRP 1.50.18 Multiple isotope fingerprints to identify sources and transport of agro-contaminants. &amp;#160;&lt;/p&gt;

Preferential Flow and Transport of Cryptosporidium parvum Oocysts through the Vadose Zone: Experiments and Modeling

2004 ◽  
Vol 3 (2) ◽  
pp. 736-736 ◽  
Author(s):  
Christophe J.G. Darnault ◽  
Tammo S. Steenhuis ◽  
Patricia Garnier ◽  
Young-Jin Kim ◽  
Michael Jenkins ◽  
...  
Keyword(s):  
Cryptosporidium Parvum ◽  
Vadose Zone ◽  
Preferential Flow ◽  
Flow And Transport ◽  
Cryptosporidium Parvum Oocysts

Transport of Nanoplastic under groundwater aquifer flow and transport conditions

2020 ◽  
Author(s):  
Sascha Müller ◽  
Tonci Balic-Zunic ◽  
Nicole R. Posth
Keyword(s):  
Preferential Flow ◽  
Particle Diameter ◽  
Steric Interaction ◽  
Colloidal Transport ◽  
Flow And Transport ◽  
Aquifer Material ◽  
Transport Behavior ◽  
Groundwater Aquifers ◽  
Groundwater Aquifer ◽  
Aquifer Flow

&lt;p&gt;In terrestrial environments soils are hypothesized sinks for plastic particles. Nonetheless, due to the existence of preferential flow paths as well as a variety of geochemical and microbiological processes, this sink may only be temporary. A vertical translocation from soils to groundwater aquifers eventually occurs along different pathways. In these conditions Nanoplastic transport characteristics are similar to colloidal transport behavior. Therby the magnitude of plastic transport is eventually governed by complex interplay between the particle with its surrounding media (particle-particle, particle-solvent, particle- porous media) masked by different hydro-geochemical and microbiological conditions. The physical entrapment of particles (straining) may be significant when the particle diameter exceeds 5% of the median grain size diameter. Below that size additional electrostatic, van der Waals or steric interaction become increasingly important.&lt;/p&gt;&lt;p&gt;We present a preliminary dataset on the interaction between Nano-sized Polystyrene (PS) with different surface coatings and a variety of common minerals occurring in groundwater aquifers under the presence of Natural Organic Matter (NOM). The reference aquifer material is based on the Danish subsurface structure of Quaternary and Miocene aquifer material, e.g. quartz, calcite and pyrite among others. In our study, batch scale interactions are up-scaled in column flow and transport experiments, simulating different groundwater aquifer flow conditions in the presence of selected minerals and NOM.&lt;/p&gt;&lt;p&gt;This aims to clarify transport behavior of plastic pollutant in the subsurface environment. Furthermore, it serves as guide in qualitatively assessing and quantifying the vulnerability of groundwater aquifers to Nanoplastic pollution.&lt;/p&gt;

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