Effect of time of application and continuity of rainfall on leaching of surface applied nutrients

Soil Research ◽  
1991 ◽  
Vol 29 (1) ◽  
pp. 1 ◽  
Author(s):  
CDA Mclay ◽  
KC Cameron ◽  
RG Mclaren
Keyword(s):  
Preferential Flow ◽  
Pore Space ◽  
Natural Soil ◽  
Sufficient Time ◽  
Undisturbed Soil ◽  
Time Of Application ◽  
Applied Pulse ◽  
Time Periods ◽  
Soil Lysimeters ◽  
Continuous Rainfall

The effect of time of rainfall relative to solute application, and the effect of rainfall continuity, was studied using undisturbed soil lysimeters. Immediate leaching with a surface-applied pulse of nitrate was compared with delayed (24 h) leaching of sulfate in a non-adsorbing soil. Preferential flow of water and solutes through natural soil macropores resulted in: (i) peak solute concentrations occurring before 1.0 pore volume of drainage, and (ii) incomplete leaching of applied solutes after 2.0 pore volumes of drainage. The immediate application of rainfall resulted in faster leaching rates compared with a delayed application. It is considered likely that the delay before rainfall allowed sufficient time for some solute to diffuse into intra- and inter-aggregate pore space and thus be bypassed by water flowing through soil macropores. Under intermittent rainfall, there was a series of time periods during which diffusion could occur into soil micropores and therefore the rate of leaching of surface-applied solute was slower than under continuous rainfall.

Influence of soil structure on sulfate leaching from a silt loam

Soil Research ◽  
1992 ◽  
Vol 30 (4) ◽  
pp. 443 ◽  
Author(s):  
CDA Mclay ◽  
KC Cameron ◽  
RG Mclaren
Keyword(s):  
Soil Structure ◽  
Packed Column ◽  
Breakthrough Curves ◽  
Natural Soil ◽  
Silt Loam ◽  
Soil Columns ◽  
Undisturbed Soil ◽  
Soil Monolith ◽  
Sulfate Leaching ◽  
Soil Lysimeters

The influence of soil structure on sulfate leaching from a silt loam soil was assessed by comparing the results of leaching experiments conducted using undisturbed soil monolith lysimeters and re-packed soil columns. A pulse application of sulfate solution was leached through both soil systems under non-ponded infiltration conditions. Breakthrough curves (BTCs) from the undisturbed soil lysimeters were poly-modal compared with the uni-modal curves observed in re-packed column experiments. The poly-modal BTC is considered to result from sulfate leached through isolated porosity regions within the undisturbed soil monolith. Sulfate leaching rates were faster through the undisturbed soil lysimeters and this was attributed to solute transport through the natural soil macropore system, which is retained in the undisturbed soil but lost in the repacked soil columns. Leaching through soil macropores therefore can result in considerable losses of sulfur from silt loam textured soils.

Chromium(VI) leaching from large undisturbed soil lysimeters following application of a simulated copper-chromium-arsenic (CCA) timber preservative

Soil Research ◽  
2002 ◽  
Vol 40 (2) ◽  
pp. 351 ◽  
Author(s):  
P. L. Carey ◽  
V. J. Bidwell ◽  
R. G. McLaren
Keyword(s):  
Organic Matter ◽  
Soil Profile ◽  
Sandy Loam ◽  
Soil Analysis ◽  
Rainfall Simulation ◽  
Soil Cores ◽  
Undisturbed Soil ◽  
First Order ◽  
Copper Chromium ◽  
Soil Lysimeters

Copper, chromium, and arsenic (CCA) solutions are commonly used in New Zealand as a means of preserving softwood timbers such as Pinus radiata. With stock working solutions of CCA salts in timber treatment plants frequently 10% w/v or more, there exists a potential for spillage and leaching of these compounds to groundwater. High concentrations of Cr(VI) (up to 52 mg Cr/L) were found in the leachates of large undisturbed soil lysimeters where a Templeton sandy loam (Immature Pallic) had received surface applications of a simulated copper, chromium, and arsenic (CCA) timber preservative. Leaching was produced by using a combination of natural and imposed rainfall simulation over the lysimeters for a period of 102 days after CCA application. An average of 26% of the applied chromium was collected in the leachates after 102 days. Of the mean 74% of Cr(VI) still retained within the soil profile after leaching ended, almost half was located in the top 100 mm of the profile. No copper or arsenic was detected in any of the lysimeter leachates, with soil analysis indicating that these elements had been retained within the soil profile. In an incubation study, soil cores sampled from the same Templeton sandy loam and split into alternate 50-mm segments (to 450 mm) were stored at 10˚C for 102 days after addition of an identical CCA solution. These were periodically extracted for available chromium. Results showed that the reduction of dichromate/chromate anions (Cr2O72–/CrO42–) to the strongly sorbed chromic cation (Cr3+) was largely first-order and greatest in surface layers where soil organic matter contents were largest. After 102 days, <1% of the added Cr(VI) was still extractable in the 0–50 mm soil cores whilst ≈60% of Cr(VI) in the 400–450 mm cores (or deeper) was still extractable after the same period. A linear systems model comprising a series of conceptual mixing cells was used to describe the individual and mean Cr(VI) leaching breakthrough curves (BTCs). This State-Space Mixing Cell model proved effective in simulating the Cr(VI) leaching using first-order kinetics to quantify rate-limited local solute adsorption coupled to advective-dispersive transport. The solute mass involved in the model process was ≈30%. The bulk of the remaining 70% of applied dichromate was assumed to have undergone reduction to the non-mobile chromium cation. This study shows that there exists a significant potential for Cr(VI) to be a serious threat to groundwater in the event of a large uncontained spillage of a concentrated CCA solution. This potential can be significantly lessened if the Cr(VI) is reduced after retention in an organic matter rich layer.

scholarly journals Improving Preferential Flow Modules by Experimentation

1994 ◽  
Author(s):  
Tammo S. Steenhuis ◽  
Israela Ravina ◽  
Jean-Yves Parlange ◽  
Rony Wallach ◽  
Larry D. Geohring
Keyword(s):  
Management Practices ◽  
Preferential Flow ◽  
Pore Space ◽  
The United States ◽  
Solute Concentration ◽  
Nonpoint Sources ◽  
The Matrix ◽  
Fast Transport ◽  
Salt Affected Soils ◽  
Field Drainage

Preferential flow is the process whereby water and solutes move by preferred pathways. During preferential flow, local wetting fronts propagate to considerable depths in the soil profile, essentially bypassing the matrix pore space. Under such conditions classical methods, such as the convective-dispersive equation, for quantifying flow of water and solutes in uniform soils are not valid. This project set out to develop methods to predict fast and early breakthrough of solutes. To facilitate understanding of these processes, several field drainage studies were conducted in the United States and Israel. In both countries, solutes moved rapidly down and could be found below 1 m depth soon after application. Based on these experiments, we developed and validated a number of modules to predict the solute concentration of the preferentially moving water in the vadose zone. We also successfully simulatd the initial high solute concentration in agriculturel tile lines shortly after the chemical was applied. The understanding gained on fast transport of agri-chemicals is instrumental in developing management practices to reduce the nonpoint sources and to increase the leaching efficiency of salt affected soils.

scholarly journals Novel rapid measurement system of undisturbed soils water characteristics curve utilizing the continuous pressurization method

2019 ◽  
Vol 92 ◽  
pp. 07008 ◽  
Author(s):  
Adel Alowaisy ◽  
Noriyuki Yasufuku ◽  
Ryohei Ishikura ◽  
Masanori Hatakeyama ◽  
Shuu Kyono
Keyword(s):  
Soil Water ◽  
Unsaturated Soils ◽  
Natural Soil ◽  
Undisturbed Soil ◽  
Water Characteristics ◽  
Undisturbed Samples ◽  
In Situ Conditions ◽  
Undisturbed Soils ◽  
Short Time

Through this paper, a sampling methodology and a novel full automatic system adopting the continuous pressurization method which is capable of determining the Soil Water Characteristics Curve (SWCC) for both remoulded and undisturbed samples in a very short time were developed. The proposed system was validated by comparing the SWCCs of standard testing soils obtained using the developed system to the SWCCs obtained using a conventional method. Remoulded and undisturbed natural soil samples were tested, where the degree of disturbance influence on the obtained SWCC was discussed. In addition, the undisturbed samples containing moulds material influence on the obtained SWCC was investigated. It was found that remoulded samples do not properly represent the in-situ conditions with significant error that should be carefully considered when conducting analysis and proposing countermeasures against unsaturated soils related Geo-disasters. In addition, the material which the containing mould is made from has minor influence on the obtained SWCC which can be neglected. Finally, it can be concluded that the developed undisturbed soil water characteristics curve obtaining system is direct, rapid, reliable and simple. In addition, the proposed undisturbed sampling and testing methodology can be used to accurately evaluate the spatial variations of the SWCC regardless the heterogeneity of the soil profile.

scholarly journals Effects of Cemented Porous Media on Temporal Mixing Behavior of Conservative Solute Transport

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1204 ◽  
Author(s):  
Zhi Dou ◽  
Xueyi Zhang ◽  
Zhou Chen ◽  
Yun Yang ◽  
Chao Zhuang ◽  
...  
Keyword(s):  
Porous Media ◽  
Solute Transport ◽  
Preferential Flow ◽  
Early Stage ◽  
Pore Space ◽  
Negative Influence ◽  
Velocity Variation ◽  
Scalar Dissipation ◽  
Mixing Behavior ◽  
Conservative Solute Transport

The cementation of porous media leads to the variation of the pore space and heterogeneity of the porous media. In this study, four porous media (PM1, PM2, PM3, and PM4) with the different radii of solid grains were generated to represent the different cementation degrees of the porous media. The direct simulations of flow and conservative solute transport in PM1–4 were conducted to investigate the influence of the cemented porous media and Peclet number (Pe) on the temporal mixing behavior. Two metrics, scalar dissipation rates (SDR) and dilution index, were employed to quantify the temporal mixing behavior. It was found that the spatial velocity variability of the flow field was enhanced as cementation degree increased. The results of the coefficient of velocity variation ( C V U ) increased from 0.943 to 2.319 for PM1–4. A network consisted of several preferential flow paths was observed in PM1–4. The preferential flow enhanced the mixing of the conservative solute but had a negative influence on the mixing of the solute plume when the cemented solid grains formed several groups, and there were some stagnant regions where the flow was almost immobile. As the Pe increased, for PM1–3, the exponent of the best-fitting power law of the global SDR decreased. At the case of Pe = 400, the slope of the global SDR reduced to around −1.9. In PM4 where the preferential flow was enhanced by the cemented solid grains, the slope of the global SDR increased as the Pe increased. The global SDR results indicated that the temporal mixing behavior followed a Fickian scaling ( S D R ∝ p v − 1.5 ) in the early stage (Pv < 0.05), while the mixing behavior turned to be non-Fickian in the late stage. The transition time from the Fickian scaling to the non-Fickian scaling was found to be sensitive to the cementation degree of the porous media.

Corrigendum to: Chromium(IV) leaching from large undisturbed soil lysimeters following application of a simulated copper-chromium-arsenic (CCA) timber preservative

Soil Research ◽  
2002 ◽  
Vol 40 (4) ◽  
pp. 715 ◽  
Author(s):  
P. L. Carey ◽  
V. D. Bidwell ◽  
R. G. McLaren
Keyword(s):  
Organic Matter ◽  
Soil Profile ◽  
Sandy Loam ◽  
Soil Analysis ◽  
Rainfall Simulation ◽  
Soil Cores ◽  
Undisturbed Soil ◽  
First Order ◽  
Copper Chromium ◽  
Soil Lysimeters

Copper, chromium, and arsenic (CCA) solutions are commonly used in New Zealand as a means of preserving softwood timbers such as Pinus radiata. With stock working solutions of CCA salts in timber treatment plants frequently 10&percnt; w&sol;v or more, there exists a potential for spillage and leaching of these compounds to groundwater. High concentrations of Cr(VI) (up to 52 mg Cr&sol;L) were found in the leachates of large undisturbed soil lysimeters where a Templeton sandy loam (Immature Pallic) had received surface applications of a simulated copper, chromium, and arsenic (CCA) timber preservative. Leaching was produced by using a combination of natural and imposed rainfall simulation over the lysimeters for a period of 102 days after CCA application. An average of 26&percnt; of the applied chromium was collected in the leachates after 102 days. Of the mean 74&percnt; of Cr(VI) still retained within the soil profile after leaching ended, almost half was located in the top 100 mm of the profile. No copper or arsenic was detected in any of the lysimeter leachates, with soil analysis indicating that these elements had been retained within the soil profile. In an incubation study, soil cores sampled from the same Templeton sandy loam and split into alternate 50-mm segments (to 450 mm) were stored at 10&ring;C for 102 days after addition of an identical CCA solution. These were periodically extracted for available chromium. Results showed that the reduction of dichromate&sol;chromate anions (Cr2O72–&sol;CrO42–) to the strongly sorbed chromic cation (Cr3&plus;) was largely first-order and greatest in surface layers where soil organic matter contents were largest. After 102 days, &lt;1&percnt; of the added Cr(VI) was still extractable in the 0–50 mm soil cores whilst ≈60&percnt; of Cr(VI) in the 400–450 mm cores (or deeper) was still extractable after the same period. A linear systems model comprising a series of conceptual mixing cells was used to describe the individual and mean Cr(VI) leaching breakthrough curves (BTCs). This State-Space Mixing Cell model proved effective in simulating the Cr(VI) leaching using first-order kinetics to quantify rate-limited local solute adsorption coupled to advective-dispersive transport. The solute mass involved in the model process was ≈30&percnt;. The bulk of the remaining 70&percnt; of applied dichromate was assumed to have undergone reduction to the non-mobile chromium cation. This study shows that there exists a significant potential for Cr(VI) to be a serious threat to groundwater in the event of a large uncontained spillage of a concentrated CCA solution. This potential can be significantly lessened if the Cr(VI) is reduced after retention in an organic matter rich layer.

Colloid Mobilization and Transport in Undisturbed Soil Columns. II. The Role of Colloid Dispersibility and Preferential Flow

2004 ◽  
Vol 3 (2) ◽  
pp. 424-433 ◽  
Author(s):  
C. Kjaergaard ◽  
P. Moldrup ◽  
L. W. de Jonge ◽  
O. H. Jacobsen
Keyword(s):  
Preferential Flow ◽  
Soil Columns ◽  
Undisturbed Soil ◽  
Colloid Mobilization

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.

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