scholarly journals Effects of large macropores on soil evaporation in salt marshes

2020 ◽  
Author(s):  
Tingzhang Zhou ◽  
Pei Xin ◽  
Jirka Jirka Šimůnek
Keyword(s):  
Water Flow ◽  
Salt Marshes ◽  
Evaporation Rate ◽  
Preferential Flow ◽  
Soil Surface ◽  
Soil Evaporation ◽  
Infrared Light ◽  
Soil Conditions ◽  
Set Up ◽  
The Impact

<p>The occurrence of macropores in salt marsh sediments is a natural and ubiquitous phenomenon. Although they are widely assumed to significantly affect water flow in salt marshes, the effects are not well understood. We conducted physical laboratory experiments and numerical simulations to examine the impact of macropores on soil evaporation. Soil columns packed with either sand or clay and with or without macropores were set up with water tables in the columns set at different levels. A high potential evaporation rate was induced by infrared light and a fan. The results showed that in the soil with a low saturated hydraulic conductivity (and thus a low transport capacity), macropores behaved as preferential flow paths, delivering water from the groundwater towards the soil surface and maintaining a high evaporation rate in comparison with the soil without macropores. This effect was more pronounced for sediments with lower hydraulic conductivities and shallower groundwater tables. These results not only improve our understanding of water flow and soil conditions in salt marshes but also shed light on soil evaporation in other hydrological systems.</p>

scholarly journals A 2D model for simulating heterogeneous mass and energy fluxes through melting snowpacks

2016 ◽  
Author(s):  
Nicolas R. Leroux ◽  
John W. Pomeroy
Keyword(s):  
Water Flow ◽  
Liquid Water ◽  
Preferential Flow ◽  
Initial Conditions ◽  
Surface Fluxes ◽  
Porous Media Flow ◽  
Accurate Estimation ◽  
Flow Paths ◽  
Preferential Flow Paths ◽  
The Impact

Abstract. Accurate estimation of the water flux through melting snowpacks is of primary importance for runoff prediction. Lateral flows and preferential flow pathways in porous media flow have proven critical for improving soil and groundwater flow models, but though many physically-based layered snowmelt models have been developed, only 1D matrix flow over level ground is currently accounted for in snow models. Snowmelt models that include these processes may improve snowmelt discharge timing and contributing area calculations in hydrological models. A two-dimensional snow model (SMPP – Snowmelt Model with Preferential flow Paths) is presented that simulates heat and water flows through both snowpack matrix and preferential flow paths, as well as snowmelt and refreezing of meltwater. The model assumes thermodynamic equilibrium between solid and liquid phases and uses the latest improvements made in snow science to estimate snow hydraulic and thermal properties. A finite volume method is applied to solve for the 2D heat and water equations. The use of a water entry pressure for dry snow combined with consideration of the impact of heterogeneities in surface fluxes and internal snow properties – density, grain size and layer thickness – allowed calculation of the formation of preferential flow paths in the snowpack. The simulation of water flow through preferential flow paths resulted in liquid water reaching the base of the snowpack earlier than for a homogeneous wetting front. Moreover, the preferential flow paths in the model increased the exchange of energy between the snow surface and the internal snowpack, resulting in faster warming of the snowpack. A sensitivity analysis, conducted on the snow internal properties showed that initial conditions such as density and temperature, should be carefully measured in the field to accurately estimate liquid water percolating through the snowpack. Furthermore, two empirical coefficients used in the water flow equation were showed to greatly impact model outputs. This heterogeneous flow model is an important tool to help understand snowmelt flow processes in complex and level terrains and to demonstrate how uncertainty in snowmelt-derived runoff calculations might be reduced.

scholarly journals Leaching of microplastics by preferential flow in earthworm (Lumbricus terrestris) burrows

2019 ◽  
Vol 16 (1) ◽  
pp. 31 ◽  
Author(s):  
Miao Yu ◽  
Martine van der Ploeg ◽  
Esperanza Huerta Lwanga ◽  
Xiaomei Yang ◽  
Shaoliang Zhang ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Soil Depth ◽  
Soil Column ◽  
Soil Surface ◽  
Lumbricus Terrestris ◽  
Soil Samples ◽  
Average Weight ◽  
Soil Layers ◽  
Groundwater Systems ◽  
Set Up

Environmental contextMicroplastics found in soil pose several potential environmental risks. This study shows that microplastics on the soil surface can be ingested by earthworms and transported to the lower soil layers. In this way, microplastics may enter the food chain and find their way into groundwater systems, especially in cases where the water table is shallow. AbstractIn the current study, we examine how the activities of earthworms (Lumbricus terrestris) affect microplastic (MP) distribution and concentration in soil, with a focus on low density polyethylene (LDPE). We also want to determine if MPs can be flushed out with water. We used a laboratory sandy soil column (polyvinyl chloride tube) experimental set-up and tested five different treatments: (1) treatment with just soil (control) to check if the saturated conductivity (Ksat) could be impacted by MP, (2) treatment with MP, (3) treatment with MP and litter, (4) treatment with earthworms and litter as a second control for treatment 5 and (5) treatment with MPs, earthworms and litter. Each treatment consisted of eight replicates. For the treatments with MP, the concentration of MP added at the start of the experiment was 7% by weight (3.97g, polyethylene, 50% 1mm–250µm, 30% 250µm–150µm and 20% <150µm) based on 52.78g of dry litter from Populus nigra. In the treatments using earthworms, two adult earthworms, with an initial average weight of (7.14±0.26) g, were placed in each column. Results showed that LDPE particles could be introduced into the soil by the earthworms. MP particles were detected in each soil sample and within different soil layers for the earthworm treatments. Earthworms showed a tendency to transport the smaller MP particles and that the amount of MPs in size class <250μm increased in soil samples with increasing soil depth in comparison to the other size classes. After leaching, MPs were only detected in the leachate from the treatments with the earthworms, and the MP had similar size distributions as the soil samples in the 40–50cm layer of the treatment with MP, earthworms and litter. The results of this study clearly show that biogenic activities can mobilise MP transport from the surface into the soil and even be leached into drainage. It is highly likely that biogenic activities constitute a potential pathway for MPs to be transported into soil and groundwater.

scholarly journals Mapping Soil Surface Macropores Using Infrared Thermography: An Exploratory Laboratory Study

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
João L. M. P. de Lima ◽  
João R. C. B. Abrantes ◽  
Valdemir P. Silva ◽  
M. Isabel P. de Lima ◽  
Abelardo A. A. Montenegro
Keyword(s):  
Infrared Thermography ◽  
Water Flow ◽  
Exploratory Study ◽  
Hydraulic Properties ◽  
Preferential Flow ◽  
Soil Surface ◽  
Small Scale ◽  
Nonequilibrium Flow ◽  
Study Laboratory

Macropores and water flow in soils and substrates are complex and are related to topics like preferential flow, nonequilibrium flow, and dual-continuum. Hence, the quantification of the number of macropores and the determination of their geometry are expected to provide a better understanding on the effects of pores on the soil’s physical and hydraulic properties. This exploratory study aimed at evaluating the potential of using infrared thermography for mapping macroporosity at the soil surface and estimating the number and size of such macropores. The presented technique was applied to a small scale study (laboratory soil flume).

scholarly journals Interplay between Fingering Instabilities and Initial Soil Moisture in Solute Transport through the Vadose Zone

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 917
Author(s):  
Luis Cueto-Felgueroso ◽  
María José Suarez-Navarro ◽  
Xiaojing Fu ◽  
Ruben Juanes
Keyword(s):  
Spatial Distribution ◽  
Solute Transport ◽  
Soil Water ◽  
Water Flow ◽  
Vadose Zone ◽  
Preferential Flow ◽  
Solute Diffusion ◽  
Wetting Front ◽  
Initial Soil ◽  
The Impact

Modeling water flow and solute transport in the vadose zone is essential to understanding the fate of soil pollutants and their travel times towards groundwater bodies. It also helps design better irrigation strategies to control solute concentrations and fluxes in semiarid and arid regions. Heterogeneity, soil texture and wetting front instabilities determine the flow patterns and solute transport mechanisms in dry soils. When water is already present in the soil, the flow of an infiltration pulse depends on the spatial distribution of soil water and on its mobility. We present numerical simulations of passive solute transport during unstable infiltration of water into sandy soils that are prone to wetting front instability. We study the impact of the initial soil state, in terms of spatial distribution of water content, on the infiltration of a solute-rich water pulse. We generate random fields of initial moisture content with spatial structure, through multigaussian fields with prescribed correlation lengths. We characterize the patterns of water flow and solute transport, as well as the mass fluxes through the soil column. Our results indicate a strong interplay between preferential flow and channeling due to fingering and the spatial distribution of soil water at the beginning of infiltration. Fingering and initial water saturation fields have a strong effect on solute diffusion and dilution into the ambient water during infiltration, suggesting an effective separation between mobile and inmobile transport domains that are controlled by the preferential flow paths due to fingering.

scholarly journals Straw Removal Effects on Sugarcane Root System and Stalk Yield

Agronomy ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1048
Author(s):  
Paul L. A. Melo ◽  
Maurício R. Cherubin ◽  
Tamara C. A. Gomes ◽  
Izaias P. Lisboa ◽  
Lucas S. Satiro ◽  
...  
Keyword(s):  
Root System ◽  
Soil Surface ◽  
Dry Mass ◽  
Soil Conditions ◽  
Root Mass ◽  
Moderate Amount ◽  
Straw Mulch ◽  
Root Regrowth ◽  
Stalk Yield ◽  
The Impact

The sugarcane (Saccharum spp. L.) mechanical harvesting system leaves a large amount of straw mulch on the soil surface. The straw mulch may affect soil conditions, root regrowth, and sugarcane yield. Thus, this study assessed the response of sugarcane root system growth and stalk yield to different rates of straw removal. An experiment was conducted in a Rhodic Kandiudox with sand clay loam texture to test the impact of four rates of straw removal: no removal (18.9 Mg ha−1 of dry mass); moderate removal (8.7 Mg ha−1); high removal (4.2 Mg ha−1) and total removal on sugarcane root system and stalk yield. Higher concentrations of roots (60%) were found in the first 40 cm of soil. Moderate straw removal resulted in higher root mass (3.6 Mg ha−1) and stalk production (23 Mg ha−1 of dry mass). However, no straw removal reduced root mass by <40% (2099 kg ha−1) and reduced stalk yield by >20% (105 Mg ha−1). Through regression analysis, it was estimated that retaining between 8.5 and 13 Mg ha−1 of straw resulted in the highest root mass and stalk yield. Managing straw removal to retain a moderate amount enables producers to sustain suitable soil conditions for sugarcane root growth and stalk production while providing straw for industrial use.

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