Evaluation of numerical techniques applied to soil solution speciation including cation exchange

Batch and leaching cell approaches were used to study the effect of a range of inorganic and organic ligands on the distribution of aluminium (Al) between the exchangeable and solution phase and to assess the ability of the ligands to mobilise aluminium in an acidic red earth (Calcic Rhodoxeralf). Anions were chosen to represent a range of potential abilities to form complexes with Al. They included chloride, fluoride, citrate, salicylate, 2,3-dihydroxybenzoic acid, catechol, and 2 different coal-derived fulvates. Batch experiments, using a 1 : 5 soil : solution ratio, showed that citrate, 2,3-dihydroxybenzoic acid, and fluoride had a similar effect on Al sorption and speciation. These anions were effective in decreasing the amount of exchangeable and sorbed Al and increased the amount of complexed Al in solution. In the soil solution, very little Al was in the uncomplexed toxic form (Al3+). Results from the batch experiments may not necessarily give a good indication of the behaviour of Al in the soil at realistic moisture contents. Therefore, those anions that showed the best capacity to remove exchangeable Al and decrease the concentration of toxic Al3+ in the solution were used in leaching cell experiments. These results showed that citrate, 2,3-dihydroxybenzoic acid, and the coal-derived fulvates can significantly decrease exchangeable Al, citrate being the most effective. Citrate and 2,3-dihydroxybenzoic acid resulted in significant amounts of Al being leached from the soil, whereas fluoride and the fulvates resulted in only slightly more Al leaching than chloride. Although the fulvates can remove some of the exchangeable Al, it was not leached from the soil. Both the batch and leaching cell techniques do allow the screening of compounds to decrease the concentration of toxic Al3+on the cation exchange complex of the soil.

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Soil-solution speciation by MINEQL+4.6 model and plant uptake of Cd and Zn by barley (Hordeum vulgare L.) after application of different phosphate fertilizers

Journal of Plant Nutrition and Soil Science ◽

10.1002/jpln.201100123 ◽

2012 ◽

Vol 175 (4) ◽

pp. 560-571 ◽

Cited By ~ 2

Author(s):

Ahmed Mohamed Mahdy

Keyword(s):

Hordeum Vulgare ◽

Soil Solution ◽

Plant Uptake ◽

Phosphate Fertilizers ◽

Hordeum Vulgare L ◽

Solution Speciation

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Prediction of the soil saturated paste extract salinity from extractable ions, cation exchange capacity, and anion exclusion

Soil Research ◽

10.1071/sr12197 ◽

2012 ◽

Vol 50 (7) ◽

pp. 536 ◽

Cited By ~ 7

Author(s):

Fernando Visconti ◽

José Miguel de Paz

Keyword(s):

Cation Exchange ◽

Soil Solution ◽

Cation Exchange Capacity ◽

Model Development ◽

Exchange Capacity ◽

Diffuse Double Layer ◽

Co2 Partial Pressure ◽

Anion Exclusion ◽

Ion Contents

Process-based models could be used to predict the soil saturated extract salinity from extractable ion contents. However, a rigorous validation of such models for this purpose had not been carried out. A process-based model to predict the main inorganic ion composition, electrical conductivity, and pH of the saturated paste extract from extractable ion contents was developed step by step. The model development started from the principle of matter conservation in the soil solution as it concentrates from the 1 : 5 to the saturated paste extract. The need to include new hypotheses in the model was studied through calculation and analysis of standardised differences between measurements and model predictions. Therefore, best estimates of saturation paste extract properties occurred after taking into account the following: (i) free equilibration of the soil solution with the minerals calcite and gypsum under CO2 partial pressure of the saturated paste; (ii) further equilibration of the soil solution with the exchange complex; and (iii) determination of salt contents within the diffuse double layer (DDL) of the soil colloids, i.e. the anion exclusion. The last was necessary because the extracts where the determination of soil extractable anions (1 : 5 extracts), cations, and cation exchange capacity (CEC) were carried out were separated from their suspensions through centrifugation. Therefore, the reliable prediction of soil saturated paste extract salinity demands data on soil extractable ion contents, CEC, and the quantification of salts within the DDL.

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Soil solution chemistry of contrasting soils amended with heavy metals

Soil Research ◽

10.1071/sr98055 ◽

1999 ◽

Vol 37 (5) ◽

pp. 993 ◽

Cited By ~ 20

Author(s):

H. J. Percival ◽

T. W. Speir ◽

A. Parshotam

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Metal Ions ◽

Cation Exchange ◽

Soil Solution ◽

Solution Chemistry ◽

Percentage Increase ◽

Soil Solution Chemistry ◽

Soil Solutions ◽

Wide Range

The soil solution chemistry of heavy metal amended soils is of great importance in assessing the bioavailability of heavy metals and their toxicity to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II), Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100 mmol/kg. This concentration range was chosen to encompass a wide range of effects on sensitive soil biochemical properties as part of a larger project. Soil solutions were extracted and analysed for pH, and for concentrations of heavy metals, and major cations and anions. Heavy metal speciation was calculated with the GEOCHEM-PC model. Heavy metal concentrations in the soil solutions increased both in absolute terms and as a percentage of added heavy metal as amendment rates increased. This observation is due to decreasing specific adsorption (caused by decreasing pH induced by the amendments), and to increasing saturation of cation exchange sites. For all 3 soils, the percentage increase commonly follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The percentage of each metal held in the soil solution increased from soil to soil as cation exchange capacity, and therefore sorptivity, decreased. Both the concentration and activity of free heavy metal ions were substantially lower than the corresponding total metal concentration. This was ascribed to ion-pairing of metal ions with anions, particularly nitrate introduced in the amending solutions, as well as to increases in ionic strength as a result of amendment. Metal-anion species were mainly inorganic but where Cu and Pb were relatively low in concentration because of strong adsorption by the soils, organic complexation was likely to be significant. Speciation trends were similar for the 3 soils but different in magnitude.

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Influence of sodium and potassium fertilization on the sodium concentration of timothy

Agricultural and Food Science ◽

10.23986/afsci.72789 ◽

1997 ◽

Vol 6 (3) ◽

pp. 259-268 ◽

Cited By ~ 1

Author(s):

Tommi Peltovuori ◽

Markku Yli-Halla

Keyword(s):

Cation Exchange ◽

Soil Solution ◽

Sodium Concentration ◽

Clay Loam ◽

Forage Crops ◽

Soil Potassium ◽

Potassium Fertilization ◽

K Concentration ◽

Sodium And Potassium ◽

K Fertilization

Sodium (Na) concentration of forage crops grown in Finland, particularly that of timothy, is much lower than is recommended in the feed of cattle. A pot experiment was carried out on clay, loam and organogenic soils to find out the effect of Na application (0, 200 or 400 mg dm-3 of soil, one application) on the concentration of Na, K, Ca and Mg of timothy and the effect of K fertilization (0, 100 and 200 mg dm-3 for each three harvests) on the efficiency of Na application. Added Na elevated the Na concentration in all harvests on all soils. The magnitude of the effect (organogenic soils≥loam>clay) was opposite to the K supplying power of the soil. Potassium fertilization suppressed the effect of Na application substantially and Na concentration was elevated remarkably only when the K concentration of the plants fell to or below the deficiency level (approximately 15 g kg-1). According to a cation exchange experiment, nearly all added Na remained in the soil solution. Still, the apparent utilization of added Na remained below 4% on all soils, demonstrating the natrophobic nature of timothy. Sodium fertilization of timothy seems to be an ineffective way of increasing the Na content of forage at least on soils of a good K status or when applied with ample K fertilization.

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