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.

Effect of salinity on soil structure and soil hydraulic characteristics

2020 ◽  
pp. 1-12
Author(s):  
Shengqiang Tang ◽  
Dongli She ◽  
Hongde Wang
Keyword(s):  
Soil Salinity ◽  
Soil Structure ◽  
Hydraulic Properties ◽  
Saline Water ◽  
Silty Clay ◽  
Silt Loam ◽  
Aggregate Formation ◽  
Soil Columns ◽  
Retention Capacity ◽  
Primary Particles

Revealing the influences of soil salinity on soil structure and hydraulic properties contributes to understanding the mechanism of salinity restraining rehabilitation of saline sodic soil in coastal area. After being passed through a 1 mm sieve, silt loam and silty clay were irrigated with saline water to achieve different soil salinities to highlight the effect of irrigation salinity on aggregate formation from primary particles. Three irrigation events with different saline water were conducted in the same 2 mo interval in soil columns; the soil columns were subjected to natural evaporation during the interval. The soil salinity, soil structure, soil–water characteristic curve, and saturated hydraulic conductivity (Ks) results were determined after the end of the third drying subprocess. The results showed that the proportion of water-stable macroaggregates (0.25–2 mm) in the silt loam and silty clay increased as the soil salt content (SSC) increased. Under the same matric suction, the retention capacity and plant-available water capacity (PAWC) of the silt loam first increased and then decreased, with the SSC increasing to a maximum of approximately 14.5 g kg−1. The retention capacity of the silty clay increased with the SSC, whereas the PAWC decreased with the SSC. The Ks of the silt loam increased with SSC. This study reveals the effects of soil salinity on aggregate formation from primary particles in wetting–drying cycles and describes the corresponding changes in hydraulic properties, which influence the rehabilitation of saline sodic soils in coastal areas.

Leaching of copper, chromium, and arsenic through some free-draining New Zealand soils

Soil Research ◽  
1996 ◽  
Vol 34 (4) ◽  
pp. 583 ◽  
Author(s):  
PL Carey ◽  
RG Mclaren ◽  
KC Cameron ◽  
JR Sedcole
Keyword(s):  
New Zealand ◽  
Chemical Properties ◽  
Physical Structure ◽  
Breakthrough Curves ◽  
Undisturbed Soil ◽  
Soil Monolith ◽  
Copper Chromium ◽  
Growth Differences ◽  
Physical And Chemical ◽  
Parameter Values

Concentrated toxic solutions of copper, chromium, and arsenic (CCA) are used extensively in the New Zealand timber preservation industry. A 2% w/v solution containing cupric, dichromate, and arsenate ions was leached through undisturbed soil monolith lysimeters containing the surface and subsurface horizons of 2 free-draining New Zealand soils. The resulting breakthrough curves were successfully modelled using the Gompertz equation for biomass growth. Differences between soil horizons in the fitted Gompertz parameter values were related to differences in soil physical and chemical properties affecting leaching. Results were compared to those from a previous study investigating pulse leaching of a concentrated CCA solution of similar ion ratio using the same soils. Generally, solution leaching produced breakthrough curves influenced more by the soil's physical structure and less by kinetic processes (i.e. sorption and diffusion). This was in part due to the high metal concentrations of the CCA solution and the decreased contact time between soil and solute in the solution leaching experiment. The relative ease of solute ion breakthrough increased in the order copper < arsenate < dichromate. The study suggests that further research is required to assess management implications for spills of these heavy metal ions to soils to prevent leaching or runoff to ground and surface water.

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.

Solute movement through two unsaturated soils

Soil Research ◽  
1995 ◽  
Vol 33 (4) ◽  
pp. 585 ◽  
Author(s):  
GN Magesan ◽  
I Vogeler ◽  
DR Scotter ◽  
BE Clothier ◽  
RW Tillman
Keyword(s):  
Unsaturated Soils ◽  
Sandy Loam ◽  
Breakthrough Curves ◽  
Dead Volume ◽  
Silt Loam ◽  
Soil Columns ◽  
Concentration Data ◽  
Fine Sandy Loam ◽  
Solute Movement ◽  
Structured Soil

Simple and inexpensive apparatus is described for studying the solute movement during unsaturated water flow through intact soil columns. A preset pressure head is maintained at the top and bottom of the soil. The applied solution is easily changed, and there is negligible 'dead volume' both above and beneath the soil. Columns 37-150 mm long, carved from the A horizons of a well structured silt loam and a weakly structured fine sandy loam, were used in the apparatus. After the soil was preleached with calcium sulfate solution, solid potassium nitrate was applied, followed by a solution of potassium chloride. Nitrate and chloride concentrations in the effluent, and in the soil after leaching, were measured. With the imposed pressure heads of between -40 and -150 mm, flow rates ranged from 0 . 5 to 9 mm/h. The convection dispersion equation (CDE) with the appropriate boundary conditions was found to adequately describe the flow of chloride and nitrate in both soils. The outflow concentration data indicated all the soil water participated in the solute transport, and the chloride breakthrough curves scaled with column length as predicted by the CDE rather than by stochastic-convective theory. The dispersivity values for the well structured silt loam were 15 and 19 mm. The values for the weakly structured fine sandy loam were 68 and 27 mm. The dispersivity may be a useful structure index, as well as being the key parameter needed to describe solute movement. The resident concentration data indicated all the water in the well structured soil was mobile, but about 15% of the water in the weakly structured soil was relatively immobile.

scholarly journals Bacteria transport and retention in intact calcareous soil columns under saturated flow conditions

2015 ◽  
Vol 63 (2) ◽  
pp. 102-109 ◽  
Author(s):  
Ahmad Farrokhian Firouzi ◽  
Mehdi Homaee ◽  
Erwin Klumpp ◽  
Roy Kasteel ◽  
Wolfgang Tappe
Keyword(s):  
Calcium Carbonate ◽  
Calcareous Soil ◽  
Reduction Rate ◽  
Breakthrough Curves ◽  
Bacterial Transport ◽  
Soil Columns ◽  
Undisturbed Soil ◽  
Bacteria Transport ◽  
Site Model ◽  
Soil Calcium

Abstract Study of bacterial transport and retention in soil is important for various environmental applications such as groundwater contamination and bioremediation of soil and water. The main objective of this research was to quantitatively assess bacterial transport and deposition under saturated conditions in calcareous soil. A series of leaching experiments was conducted on two undisturbed soil columns. Breakthrough curves of Pseudomonas fluorescens and Cl were measured. After the leaching experiment, spatial distribution of bacteria retention in the soil columns was determined. The HYDRUS-1D one- and two-site kinetic models were used to predict the transport and deposition of bacteria in soil. The results indicated that the two-site model fits the observed data better than one-site kinetic model. Bacteria interaction with the soil of kinetic site 1 revealed relatively fast attachment and slow detachment, whereas attachment to and detachment of bacteria from kinetic site 2 was fast. Fast attachment and slow detachment of site 1 can be attributed to soil calcium carbonate that has favorable attachment sites for bacteria. The detachment rate was less than 0.02 of the attachment rate, indicating irreversible attachment of bacteria. High reduction rate of bacteria was also attributed to soil calcium carbonate.

Helical piles in unsaturated structured soil: a case study

2016 ◽  
Vol 53 (1) ◽  
pp. 103-117 ◽  
Author(s):  
Cristina de Hollanda Cavalcanti Tsuha ◽  
João Manoel Sampaio Mathias dos Santos Filho ◽  
Thiago da Costa Santos
Keyword(s):  
Soil Structure ◽  
Load Test ◽  
Bottom Plate ◽  
Natural Soil ◽  
Residual Soil ◽  
Compression Tests ◽  
Undisturbed Soil ◽  
Cone Penetration Tests ◽  
Helical Piles ◽  
Load Tests

The use of helical piles as tower foundations in Brazil has increased considerably during the last 5 years. A number of these piles are installed in unsaturated structured soils that cover a significant part of the Brazilian territory. However, the installation of helical piles in such soils produces a breakdown of the natural soil structure, which affects the pile performance for tension applications. This scenario motivates the present work, in which a comprehensive pile load-test program was carried out on helical piles composed of a single helix or multi-helices, installed in an unsaturated tropical residual soil. Eleven full-scale pile axial load tests were carried out, including two compression and nine tension tests. In addition, cone penetration tests were performed close to the piles after installation, and undisturbed soil samples were collected at the depth of the helices. The aim of these additional tests was to contribute to the understanding of the effect of helical pile installation on soil structure. The results of the tension load tests showed that the changes in the structure of the porous tested soil result in particularly low pile uplift capacities. In contrast, the load–settlement curves of the pile compression tests indicate a peculiar failure mechanism due to the sensitive soil structure associated with the high void ratio of the intact soil beneath the bottom plate.

AN IMPROVED METHOD TO STUDY SOLUTE LEACHING IN LARGE UNDISTURBED SOIL COLUMNS NEAR FIELD CAPACITY TOWARD THE GROUNDWATER IN VARIOUS ENVIRONMENTS

2020 ◽  
Vol 15 (1) ◽  
pp. 93-102
Author(s):  
Cristian PĂLTINEANU ◽  
◽  
Andrei VRINCEANU ◽  
Anca-Rovena LĂCĂTUȘU ◽  
Radu LĂCĂTUŞU ◽  
...  
Keyword(s):  
Near Field ◽  
Field Capacity ◽  
Improved Method ◽  
Soil Columns ◽  
Undisturbed Soil ◽  
Solute Leaching

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

2004 ◽  
Vol 3 (1) ◽  
pp. 316
Author(s):  
M. Saleem Akhtar ◽  
Tammo S. Steenhuis ◽  
Brian K. Richards ◽  
Murray B. McBride
Keyword(s):  
Sandy Loam ◽  
Sandy Loam Soil ◽  
Silt Loam ◽  
Soil Columns ◽  
Lithium Transport ◽  
Loam Soil

SOIL MORPHOLOGY AND SOIL PHYSICAL PROPERTIES. I. SOIL AERATION

1972 ◽  
Vol 52 (3) ◽  
pp. 311-321 ◽  
Author(s):  
K. W. AYRES ◽  
R. G. BUTTON ◽  
E. DE JONG
Keyword(s):  
Soil Structure ◽  
Regression Coefficient ◽  
The Other ◽  
Soil Morphology ◽  
Soil Horizons ◽  
Undisturbed Soil ◽  
Soil Aeration ◽  
Structural Types ◽  
Highly Correlated ◽  
Undisturbed Soil Cores

The relation between soil structure and soil aeration was investigated on undisturbed soil cores from soil horizons exhibiting six distinct kinds of soil structure (prismatic, columnar, blocky, granular, platy, massive) over a broad range of soil texture. Soil aeration was characterized at ⅓ atm suction by measurements of air porosity, relative diffusivity (D/Do) and the rate of oxygen diffusion to a platinum microelectrode (ODR). Aeration was adequate in most of the Chernozemic soil horizons studied; however, aeration in many of the Bnt horizons of the Solonetzic soils was inadequate. Air porosity and D/Do were highly correlated. The regression coefficient for D/Do vs. air porosity for blocky structures was significantly different from that found for the other five structural types. For granular structures a negative correlation was found for ODR vs. air porosity compared with a low positive correlation found for the other structure types.

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