Sandy Loam Soil Columns Research Articles

Bromide Transport through Soil Columns in the Presence of Pumice

Solute transport parameters, similar to soil physical and chemical properties, can be affected by the presence of organic and mineral soil conditioners. In this study, the effect of different levels (0, 3, and 6 weight percent) of the inexpensive and easily accessible pumice conditioner on the parameters of bromide transport in sandy loam soil columns (diameter and height of 10 cm) was investigated. The transport parameters were estimated based on the breakthrough curves (BTCs) by the inverse modelling of the convection-dispersion equation (CDE) and the mobile-immobile model (MIM) using the CXTFIT software. The BTCs showed that bromide transport in the sandy loam soil columns, regardless of the presence of pumice, was mainly equilibrium, and the CDE was more efficient than the MIM, which is based on non-Fickian and non-equilibrium transport. The peak of the BTCs (maximum relative concentration) was lower in the treatments containing pumice and belonged to more pore volume than the controlled treatment did. This indicates a lack of preferential flow and thus, a reduction in the amount of bromide consumed in the treatments containing pumice. The increase of pumice content did not have a significant effect on the parameters of mobile water fraction (β) and mass transfer coefficient (ω) in the MIM, confirming the equilibrium transport of bromide. A 3% increase in the pumice content in the soil caused an increase and a decrease of 47% in dispersivity (λ) and Peclet number (Pe), respectively. In general, it can be concluded that the use of pumice in field conditions can prevent water loss and nutrients and reduce groundwater contamination by reducing the preferential paths.

Efficiency of Physical Equilibrium and Non-Equilibrium Models for Simulating Contaminant Transport in Laboratory-Scale

In order to better management of contaminant in porous media, it is essential to recognize their transport behavior using appropriate models. In this research, convection-dispersion equation (CDE) and mobile-immobile (MIM), as physical equilibrium and non-equilibrium models, respectively, were used to simulate the bromide transport (as a conservative contaminant) through undisturbed and saturated clay loam and sandy loam soil columns (diameter of 10 and height of 40 cm). To simulate the transport, CXTFIT2.1 software, in which the CDE and the MIM models are included, was used. The values of mass transfer coefficient (ω

Influence of commercial formulation on leaching of four pesticides through soil

Studies with small soil columns (2cm i.d.×5.4cm depth) compared leaching of four pesticides added either as technical material or as commercial formulations. Pesticides were selected to give a gradient of solubility in water between 7 and 93mgL−1, comprising azoxystrobin (emulsifiable concentrate, EC, and suspension concentrate, SC), cyproconazole (SC), propyzamide (SC) and triadimenol (EC). Columns of sandy loam soil were leached with 6 pore volumes of 0.01M CaCl2 either 1 or 7days after treatment. Separate experiments evaluated leaching of triadimenol to full breakthrough following addition of 18 pore volumes of 0.01M CaCl2. The mass of pesticide leached from columns treated with commercial formulation was significantly larger than that from columns treated with technical material for all compounds studied and for both leaching intervals (two-sided t-tests, p<0.001). This difference was conserved when triadimenol was leached to full breakthrough with 79±1.2 and 61±3.1% of applied triadimenol leached from columns treated with formulated and technical material, respectively. There were highly significant effects of formulation for all pesticides (two-way ANOVA, p<0.001), whereas leaching interval was only significant for azoxystrobin EC formulation and cyproconazole (p<0.001 and 0.021, respectively) with greater leaching when irrigation commenced 1day after treatment. Leaching of azoxystrobin increased in the order technical material (6.0% of applied pesticide)<SC formulation (8.5–9.1% of applied)<EC formulation (15.8–21.0% of applied). The relative difference between leaching of formulated and technical pesticide increased with pesticide solubility in water, increasing from a factor of 1.4 for the SC formulation of azoystrobin to 4.3 for the SC formulation of triadimenol. Experimental systems differ markedly from field conditions (small columns with intense irrigation). Nevertheless, results indicate the need to consider further the influence of co-formulants in pesticide formulations on behaviour of the active ingredient in soil.

Modeling Bromide Transport in Undisturbed Soil Columns with the Continuous Time Random Walk

Nowadays, mathematical models are commonly used as efficient tools in solute transport studies and management in porous media. In this paper, we evaluated the continuous time random walk (CTRW) theory for its capability to characterize bromide transport in one-dimensional saturated undisturbed clay loam and sandy loam soil columns (10 cm in diameter and 40 cm long). The transport process was also simulated by using the advection–dispersion equation (ADE) for comparison. The values of CTRW parameter, β, for clay loam and sandy loam soil columns were derived at 1.71 and 1.73, respectively. This indicated that the bromide transport behavior within the clay loam and sandy loam soil columns was anomalous transport or non-Fickian transport and CTRW model was more suitable for simulation of bromide transport through undisturbed clay loam and sandy soil columns compared to ADE model with Fickian diffusion law basis. The graphical and statistical analysis confirmed the efficiency of CTRW model for simulation of bromide transport.

Reclamation of highly calcareous saline-sodic soil using low quality water and phosphogypsum

The efficiency of two amendments in reclaiming saline sodic soil using moderately saline (EC) and moderate sodium adsorption ratio (SAR) canal water was investigated. Phosphogypsum (PG) and reagent grade calcium chloride were applied to packed sandy loam soil columns and leached with canal water (SAR = 4, and EC = 2.16 dS m−1). Phosphogypsum was mixed with top soil prior to leaching at application rates of 5, 10, 15, 20, 25, 35, 40 Mg ha−1, whereas calcium chloride was dissolved directly in water at equivalent rates of 4.25, 8.5, 12.75, 17.0, 21.25, 29.75, and 34 Mg ha−1, respectively. Both amendments efficiently reduced soil salinity and sodicity. Calcium chloride removed 90 % of the total Na and soluble salts whereas PG removed 79 and 60 %, respectively. Exchangeable sodium percentage was reduced by 90 % in both amendments. Results indicated that during cation exchange reactions most of the sodium was removed when effluent SAR was at maximum. Phosphogypsum has lower total costs than calcium chloride and as an efficient amendment an application of 30 Mg ha−1 and leaching with 4 pore volume (PV) of canal water could be recommended to reclaim the studied soil.

The Fate of Cryptosporidium Parvum Oocysts in Reclaimed Water Irrigation-history and Non-history Soils Irrigated with Various Effluent Qualities

The present study aimed to look at the fate of protozoan parasite Cryptosporidium parvum oocysts applied through surface drip irrigation on reclaimed water irrigation-history and non-history sandy-loam (Hamra) soil columns. A new and simple isolation method for recovery of oocysts from soil samples was developed and used along this study. The new soil isolation method of oocysts is based on the "two phase separation method" formerly used to recover Clostridium perfringens spores from sedi- ments and soil samples with minor modifications. The range recovery achieved by this method was 64-95% (mean 61.2±17.4). The objectives of the second part of this study were to investigate several physical and chemical factors governing transport and survival of C. parvum oocysts in sandy-loam soil columns by breakthrough curves. Comparison of fresh water and reclaimed water irrigation revealed that reclaimed water irrigated-history soil was more hydrophobic allowingwater flowthrough channelswith poor oocysts retention and fast flow. Examination of the organic matter effect (originating from reclaimed water irriga- tion) on oocysts breakthrough revealed that their soil infiltration increased. Calculations of oocysts concen- tration at different columns depths showed that most of the oocysts were retained in the first 5 cm of soil column. In the present study, comparing the two soil types (history and non-history of effluents irrigation) beside the surface electrostatic charge, one of the main elements found to affect oocysts infiltration and transport in soil columns was soil hydrophobicity caused by soluble organic matter originating from reclaimed water irrigation. Therefore, prior to applica- tion in soil irrigation, reclaimed water should be treated to high quality (i.e. membrane technology as the best option) to prevent enhanced transport of various pathogens through those irrigated soils.

Effect of soil amendments on sorption and mobility of metribuzin in soils

Metribuzin (4-amino-6- tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one), is weakly sorbed to soil therefore, leaches easily to lower soil profiles. Soil amendments play a significant role in the management of leaching losses of pesticides. Therefore, present study reports the effect of organic manure and fly ash amendments on metribuzin downward mobility in sandy loam soil columns. Application of animal manure [T-1(OM) and T-2(OM)] and fly ash [T-1(FA) and T-2(FA)] at 2.5% and 5.0% levels increased the metribuzin retention in the soil. Freundlich constant [ K f(1/ n)] values of metribuzin for treatments T-1(OM) and T-2(OM) were 0.70 and 1.11, respectively, which were significantly higher than the value (0.27) in natural soil (T-0). The respective values for treatments T-1(FA) and T-2(FA) were 1.80 and 4.61. Downward mobility of metribuzin was studied in packed soil columns [300 mm (l) × 59 mm (i.d.)]. Both the amendments significantly reduced the downward mobility of metribuzin and affected breakthrough time and maximum concentration of metribuzin in the leachate. Leaching losses of metribuzin were decreased from 97% in natural soil (T-0) column to 64% [T-1(OM)] and 42% [T-2(OM)] for animal manure-amended columns and 26% [T-1(FA)] to 100% [T-2(FA)] for fly ash-amended columns, as metribuzin did not leach out of 5% fly ash-amended column. Study indicates that both animal manure and fly ash were quite effective in reducing the downward mobility of metribuzin in packed soil columns of a sandy loam soil.

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

Vadose Zone J. 2:715–727 (November 2003)

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

The transport of Cl− and Li+ was investigated in 90 undisturbed soil columns (28‐cm diam., 35 cm deep) representing two soil series: structured silt loam (Hudson; fine, illitic, mesic Glossaquic Hapludalfs) and unstructured sandy loam (Arkport; coarse‐loamy, mixed, active, mesic Lamellic Hapludalfs). The columns had previously been operated with two cropping cycles, including two applications of a variety of sewage sludges (biosolids) at agronomic rates. With soil columns at field capacity and with no crops present, a pulse of 3.55 mM LiCl was added in the equivalent of 5.8 cm of water over the surface of the columns, followed by several irrigations (11.6 cm total depth) of deionized water and multiple subsequent irrigations with synthetic acid rain. Tracer concentrations in the outflow water increased almost immediately after application, with the Li+ concentrations an order of magnitude less than Cl− Although there was a great deal of variation in initial Cl− concentrations among the individual columns, the overall pattern was consistent for each soil after the initial 10 cm of flow (when variable preferential flow effects dominated) and was independent of the sludge applications. Outflow Li+ concentrations were extremely variable among columns. Lithium adsorption partition coefficients (kd) from batch equilibrations were lower than those derived from outflow concentrations. Solute losses were described with a simple preferential flow model. Apparent water contents fit a normal distribution for Cl− while Li+ apparent kd values were lognormally distributed. Outliers (i.e., columns with transport parameters very different from the mean) had transport velocities that were slower than would be predicted by the respective distributions. Probabilistic approaches can be used to select the number of experimental columns required to meet a desired level of probability that soils columns with a meaningful range of transport velocities will be represented in the experimental set.

Effect of Water Flux on Solute Velocity and Dispersion

A systematic analysis of the effect of displacement length, soil texture, and steady state water flux (q) on solute transport was performed on saturated repacked loam and sandy loam soil columns to identify the simplest possible description that was consistent with the observations across all of the breakthrough curves (BTCs) for each data set. All 39 BTCs obtained from loam and 21 from sandy loam soils, with column lengths of 10, 20, and 30 cm, and a two‐order magnitude variation in measured pore water velocity (vm), were fitted simultaneously and global estimates of parameters [dispersivity (λ) and molecular diffusion coefficient (D0)] were obtained. We showed that a two‐parameter global dispersion relationship (D = λvm + D0, where D is the apparent diffusion coefficient) accurately represents the spreading process for all 39 loam soil BTCs (r2 &gt; 0.99), whereas a single global parameter (D = λvm) was all that was required for the sandy soil (r2 &gt; 0.98). The globally fitted λ was independent of displacement length and vm D remained independent of vm in the lower velocity ranges; however, a linear relationship between vm and fitted D was obtained for vm &gt; 0.1 cm h−1 The results of this study illustrated the importance of molecular diffusion. In addition, we identified a nonlinear relationship between vm and average solute velocity (vs), which suggested that the anion exclusion volume decreased with increasing vm

Chloride and Lithium Transport in Large Arrays of Undisturbed Silt Loam and Sandy Loam Soil Columns

The transport of Cl− and Li+ was investigated in 90 undisturbed soil columns (28-cm diam., 35 cm deep) representing two soil series: structured silt loam (Hudson; fine, illitic, mesic Glossaquic Hapludalfs) and unstructured sandy loam (Arkport; coarse-loamy, mixed, active, mesic Lamellic Hapludalfs). The columns had previously been operated with two cropping cycles, including two applications of a variety of sewage sludges (biosolids) at agronomic rates. With soil columns at field capacity and with no crops present, a pulse of 3.55 mM LiCl was added in the equivalent of 5.8 cm of water over the surface of the columns, followed by several irrigations (11.6 cm total depth) of deionized water and multiple subsequent irrigations with synthetic acid rain. Tracer concentrations in the outflow water increased almost immediately after application, with the Li+ concentrations an order of magnitude less than Cl− Although there was a great deal of variation in initial Cl− concentrations among the individual columns, the overall pattern was consistent for each soil after the initial 10 cm of flow (when variable preferential flow effects dominated) and was independent of the sludge applications. Outflow Li+ concentrations were extremely variable among columns. Lithium adsorption partition coefficients (kd) from batch equilibrations were lower than those derived from outflow concentrations. Solute losses were described with a simple preferential flow model. Apparent water contents fit a normal distribution for Cl− while Li+ apparent kd values were lognormally distributed. Outliers (i.e., columns with transport parameters very different from the mean) had transport velocities that were slower than would be predicted by the respective distributions. Probabilistic approaches can be used to select the number of experimental columns required to meet a desired level of probability that soils columns with a meaningful range of transport velocities will be represented in the experimental set.

Effect of Water Flux on Solute Velocity and Dispersion

A systematic analysis of the effect of displacement length, soil texture, and steady state water flux (q) on solute transport was performed on saturated repacked loam and sandy loam soil columns to identify the simplest possible description that was consistent with the observations across all of the breakthrough curves (BTCs) for each data set. All 39 BTCs obtained from loam and 21 from sandy loam soils, with column lengths of 10, 20, and 30 cm, and a two-order magnitude variation in measured pore water velocity (vm), were fitted simultaneously and global estimates of parameters [dispersivity (λ) and molecular diffusion coefficient (D0)] were obtained. We showed that a two-parameter global dispersion relationship (D = λvm + D0, where D is the apparent diffusion coefficient) accurately represents the spreading process for all 39 loam soil BTCs (r2 > 0.99), whereas a single global parameter (D = λvm) was all that was required for the sandy soil (r2 > 0.98). The globally fitted λ was independent of displacement length and vm D remained independent of vm in the lower velocity ranges; however, a linear relationship between vm and fitted D was obtained for vm > 0.1 cm h−1 The results of this study illustrated the importance of molecular diffusion. In addition, we identified a nonlinear relationship between vm and average solute velocity (vs), which suggested that the anion exclusion volume decreased with increasing vm

Particle‐Facilitated Transport of Prochloraz in Undisturbed Sandy Loam Soil Columns

AbstractThe mobility of strongly sorbing pesticides in soils may be higher than formerly assumed, due to facilitated transport along with mobilized colloids. Our objective was to verify whether facilitated transport enhances the vertical movement of prochloraz (N‐propyl‐N‐[2‐(2,4,6‐trichlorophenoxy)ethyl] imidazole‐1‐carboxamide). Experiments were carried out using 20 cm diam. by 20 cm long undisturbed soil columns taken from the topsoil (sandy loam, Typic Hapludalf) from a field under barley/grass (Hordeum vulgare L/Lolium perenne L.) cultivation near Rogen, Denmark. Prochloraz was applied to the surface as a pulse in solution. The irrigation intensity was 10 mm h−1, and the lower boundary of the columns was at atmospheric pressure. Three treatments each with four replicates were performed to study the effect of ionic strength and pH on pesticide and particle transport. Leaching of particles and pesticide was promoted by decreasing the ionic strength of the irrigation solution, and increasing pH by ammonia application. This is in line with the theory of electrostatic interactions. Preferential flow and particle transport were the two most important factors determining the amount of pesticide leached. A large variability in amount leached was observed among the replicates (standard deviations of 38–141%) mainly due to differences in water transport in the columns. Particle‐facilitated transport was significant, but did not dominate prochloraz transport. Depending on the pH and ionic strength of the applied solution, 2.5 to 13.1% of the leached pesticide was sorbed to particles with diameter d &gt; 0.24 µm, and 3 to 9% to particles with 0.02 &lt; d &lt; 0.24 µm.

Evaporation from soil in relation to residue rate, mixing depth, soil texture and evaporativity

The role of crop residues as a surface mulch on evaporation has been widely studied. But information on evaporation and its reduction by crop residues mixed in surface soil to different depths particularly in relation to soil texture and evaporativity ( E o ) is lacking. We studied the effect of four rates of paddy straw, viz. 0, 2, 4 and 8 Mg ha −1 used as mulch and mixed in top soil layer to two depths (2 and 5 cm) under two evaporativities ( E o 's) viz. 2.0 ± 0.5 and 8.7 ± 1.5 mm day −1 in silty clay loam and sandy loam soil columns of 0.95 m length and 0.1 m diameter. Cumulative evaporation was predicted from water transmission properties of the soil and E o as influenced by these variables. The otherwise short-lived benefit of evaporation reduction with mulch per se, which peaked after a few days, plateaued when residue was mixed with soil at peak reduction, and as a result the benefit was prolonged. The maximum reduction achieved was more and sustained for a longer period in finer textured soil, and a higher rate of mulch mixed to a greater depth. Mixing of residue in the surface soil layer not only reduced evaporation but also resulted in higher water content in the near surface soil after drying.

Predicting sodification of calcium-saturated soil columns on leaching with sodic waters

SummaryDepth accumulation of exchangeable Na+ was measured in Ca-saturated sandy loam soil columns (length 50 cm; diameter 5 cm) after percolating 500, 1000, 1500 and 2000 ml of 013 M Na+, as NaCl, NaHCO3, Na2SO4 and Na2CO3 solutions. The values of exchangeable sodium percentage (ESP) increased gradually with the increase in the volumes of the solution percolated. Two conceptual layer models, based on whether solutions were added to the topmost soil layer in one lot (M-I) or in splits equal to the saturation deficit (M-II), were used to predict the depth distribution of ESP of soil. The chemical processes considered in the models were the formation of ion pairs and the exchange equilibria of Na+ and Ca2+. The predicted values of ESP were considerably higher for model M-II than model M-I. The consideration of ion-pair formation and the accompanying anion had only negligible effect on the predicted ESP. The model M-II over-predicted the experimental ESP throughout the soil columns, whereas the model M-I under-predicted it for the upper layer(s) and over-predicted for the lower layers. On the basis of average ESP of the whole columns, the less realistic model M-I predicted experimental results better than model M-II. This was attributed to the presence of mobile and immobile zones for the flowing solutions.

Leaching and Degradation ofdl-Strigol in Soil

Leaching ofdl-strigol at six rates between 0.3 and 4.5 kg/ha through columns of sandy loam soil was estimated using a witchweed [Striga asiatica(L.) Kuntze # STRLU] germination bioassay. After 21 days of leaching daily with 1.27 cm of simulated rainfall, about 86% of the applied chemical remained in the top 2.5 cm of the soil, about 6% in the zone between 2.5 and 7.5 cm, and less than 1% in the soil at depths between 7.5 and 30 cm. However, even with the lowest rate of the chemical application, sufficientdl-strigol was leached to a soil depth between 22.5 and 30 cm to cause most, if not all, of the witchweed seeds to germinate. These results suggest thatdl-strigol has a potential for use as an effective tool for a witchweed control or eradication program. No significant degradation of the chemical occurred in moist soil during the 21-day period.

Anaerobic digestion of free volatile fatty acids in soils below waste tips

Leachate from a waste tip in the acidification stage contains a lot of volatile fatty acids. Soil column experiments showed that the removal of these acids in soil by CH4-fermentation can be quite effective, especially in soils with a high buffering capacity. In sandy loam soil columns, where the retention time was only 17 days, the fatty acids were removed completely, even at a high concentration level of 6500 mg l−1 acetic acid equivalents. In sandy soils with a low buffering capacity the CH4-fermentation was already limited at rather low acid concentrations.

Persistence and movement of terbacil in peach orchard soil after repeated annual applications*

Summary:Terbacil (5‐chloro‐6‐methyl‐3‐butyluracil) residues did not accumulate in peach orchard soil after seven consecutive annual spring applications of the herbicide at the rate of 4.5 kg/ha although carry‐over of terbacil from year to year occurred. Terbacil was lost by degradation and leaching and the time required for a 50% decrease in surface soil concentration was 5–7 months in the sandy loam soil. The major part of the residues was found in the upper 15 cm of the soil profile and smaller amounts were detected to a depth of 60 cm. Terbacil leached readily in prepared columns of sandy loam soil in proportion to the amount of water added. The residual levels of terbacil in the orchard were phytotoxic to oats planted 3 years after the last application.