The Daisy agroecological system model: A physically based model for preferential water flow and solute transport in drained agricultural fields

<p>Preferential water flow and solute transport in agricultural systems affects not only the quality of groundwater but also the quality of surface waters like streams and lakes. This is due to the rapid transport of agrochemicals, immediately after application, through subsurface drainpipes and surface water. Experimental evidence attributes this to the occurrence of continuously connected pathways, connecting the soil surface directly with the drainpipes. We developed a physically-based model describing preferential flow and transport in biopores and implemented it in the agroecological model Daisy. The model simulates the often observed rapid transport of chemicals from   the upper soil layers to the drainpipes or to deeper layers of the soil matrix. Based on field investigations, biopores with specific characteristics can be parameterized as classes with different vertical and horizontal distributions. The model was tested against experimental data from a column experiment with an artificial biopore and showed good results in simulating preferential flow dynamics. We illustrate the performance of the new approach, by conducting five simulations assuming a two-dimensional simulation domain with different biopore parametrizations, from none to several different classes. The simulation results agreed with experimental observations reported in the literature, indicating rapid transport from the soil to the drainpipes. Furthermore, the different biopore parametrizations resulted in distinctly different leaching patterns, raising the expectation that biopore properties could be estimated or constrained based on observed leaching data and direct measurements.</p>

May macropores increase contaminant retention?

<p>Preferential flow is quite usual in natural environments. Non-uniform and preferential flows co-exist or alternate, impacting water transport and contaminant transfer through the vadose zone. In this study, we investigated how macropore-induced flow affects manufactured nanoparticles, as emerging contaminants reactive transfer. Previous studies showed that the presence of a macropore into water-saturated soil columns can foster preferential water flow within the macropore. One could expect that this preferential flow may increase contaminant transfer and reduce retention by the matrix in the case of contaminant, as previously reported. In this study, we injected pulses of silver nanoparticles to assess their transfer through sand columns with and without a macropore. Both systems (with and without macropore) were studied under similar conditions. An unexpected result was obtained: more nanoparticles were retained in the system with a macropore, i.e., with a preferential flow. This result is quite counter-intuitive. It appears that the relation between flow homogeneity and contaminant retention is not straightforward. Some possible explanations, related to chemical and physical kinetics, are put forward to explain the experimental results.</p>

Preferential water remediation of cationic dyes using structurally engineered novel organoselenium based self-assembled constructs

Selenide derivatives of imidazo[1, 2-a]pyridyl heterocyclic system have been investigated for their potential to generate novel and diverse self-assembled architectures. The effect of structural modification as well as insertion of...

Determination of Sorptivity, Infiltration Rate and Hydraulic Conductivity of Loamy Sand using Tension Infiltrometer and Double-Ring Infiltrometer

This study was conducted to assess the effectiveness and accuracy of tension infiltrometer (TI) over double ring infiltrometer (DI) for determining infiltration rate (I) of loamy sand. Sorptivity (S), infiltration rate and hydraulic conductivity (K) are soil properties that govern the rate of entry of water into the soil and its movement within the soil. The ease and accurate measurement of these properties depend on the instruments used. DI operates by ponding water and could be affected by preferential water flow during infiltration test which could not be avoided especially on a fertile soil. DI and TI at water potentials of -0.02, -0.04, -0.05 and -0.06 m were used to determine infiltration rate of the soil. The mean values of sorptivity for DI and TI at water potentials of -0.02, -0.04, -0.05 and -0.06 m were 847.02, 63.50, 33.15, 29.90 and 19.46 mm/h1/2, respectively. Mean values of infiltration rates for DI and TI at -0.02, -0.04, -0.05 and -0.06 m water potentials were 471.26, 176.84, 73.73, 71.32 and 37.73 mm/h, respectively. Mean values of hydraulic conductivity for DI and TI at -0.02, -0.04, -0.05 and -0.06 m were 344.45, 22.42, 18.61and 16.83 mm/h, respectively. DI required 100-150 litres for the infiltration test, difficult where water is very scarce and gave higher values of infiltration rate. TI saved water (2-3 litres), controlled preferential water flow and values of S, I and K were within the range obtained by other researchers. TI is more effective for measuring hydraulic properties soil than DI.Keywords:Double ring infiltrometer, tension infiltrometer, sorptivity, infiltration rate, hydraulic conductivity