Solubility and Leaching of Boron from Borax and Colemanite in Flooded Acidic Soils

Boron (B) is a micronutrient essential for adequate plant growth. Borax (Na₂B₄O₇·10H₂O) and colemanite (Ca₂B₆O₁₁·5H₂O) are common B fertilizer materials, the former being widely used worldwide. Boron is completely water soluble and subjected to leaching. In this study, the dissolution kinetics of both borax and colemanite in deionized water and at pH 3.8, 5.2, 6.5, and 8.2 were determined. Soils incubated with minerals for 40 days and 80 pore volumes of leachates from repacked soil column treated with either surface-applied borax or colemanite (powdered and granular) were collected and analyzed for B contents. Two different soils, Chempaka (Typic paleudult) and Tepus (Typic Kandiaquult) series, taken from paddy-growing areas were used in leaching and incubation studies. Dissolution rate of borax was greater than that of colemanite, and complete dissolution was observed after 100 min, whereas complete dissolution of colemanite was not reached even after 300 min. There was no effect of pH on dissolution rate of borax and colemanite. Boron released from borax was hasty, and after 5 weeks no more B was released. In the case of colemanite, B released was steadily increased until the end of the incubation study. At the end of the study, there was no significant difference in B levels of both borax- and colemanite-applied soils. Particle size had a significant effect on the solubility and dissolution rate of colemanite. Boron dissolution rate and solubility from colemanite powder were significantly greater than those from granular colemanite. Leaching losses from borax were much greater than from colemanite as indicated by the breakthrough curves, which were earlier for borax than colemanite. After 60 pore volumes, no more B was leached out from borax, and in the leachates of colemanite some concentration was detected even after 80 pore volumes. Boron content in soil of columns after the completion of the experiment was greater in case of colemanite. Borax and colemanite fertilizers showed the same trend of leaching and B releasing in both Tepus and Chempaka soil series.     

Retarded leaching of nitrate in acid soils from the tropics: measurement of the effective anion exchange capacity

Delay in the leaching of nitrate was measured in laboratory columns of repacked soils (Oxisols, Alfisols, Ultisols and Inceptisols) from South America, Africa and South-East Asia. Between one and five pore volumes were required for the frontal displacement of chloride by nitrate (2 mM adjusted to the natural pH of the soil). The delay was in good agreement with that calculated from charge (0 to 1.7 cmol positive charge kg^?1). Measurement of charge by batch equilibration with 0.5 M and then 2 mM NH₄CI at the pH of the soil overestimated the effective charge, probably due to removal of sulphate in the washings. A leaching method using only 2 mM NH₄CI gave a better estimate.     

Lime application to reduce phosphorus release in different textured intact and small repacked soil columns

Purpose

Phosphorus (P) losses from agricultural fields through leaching are the main contributors to eutrophication of lakes and rivers in North America. Adoption of P-retaining strategies is essential to improve the environmental quality of water bodies. The main objective of this study is to evaluate lime as a soil amendment in reducing phosphorus concentration in the leachate from three common soil textures with neutral to alkaline pH.

Materials and methods

Phosphorus leaching from undisturbed soil columns (10 cm in diameter and 20 cm deep) as well as small repacked columns was investigated and compared in this study. Lime (high calcium hydrated lime) at the rate of 1% by air-dried soil mass was applied to the topsoil of the columns. Both sets of experiments followed a full factorial design with two factors of soil texture at three levels (sandy loam, loam, and clay loam) and treatment at two levels (control and limed) with three replicates. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was performed on the control and limed soil samples to confirm the formation of calcium phosphate compounds.

Results and discussions

For both intact and repacked columns, dissolved reactive phosphorus (DRP) concentrations in the leachates from limed sandy loam and limed loam soil columns was significantly reduced, while DRP in the limed clay loam column leachates was not changed. Elemental mapping demonstrated that in limed sandy loam and loam soils, the calcium loadings on the soil surface were always linked with phosphorus. The formation of calcium phosphate compounds and the increased phosphate adsorption on the soil surface through Ca bridging could be the two main phosphorus-lime retention mechanisms. Total dissolved phosphorus (TDP) in the leachates of limed loam and limed clay loam indoor intact and repacked columns was reduced, while there was no change in that of the sandy loam soil. In finer textured soils, lime can increase TDP retention through the immobilization of organic phosphates.

Conclusions

The impact of lime application on DRP and TDP varied with the soil texture. The lime-induced reduction in the DRP and TDP was variable between the intact and repacked columns demonstrating the importance of soil structure on phosphorus and lime interactions in the soil. Overall, lime application at the studied rate can be considered a promising soil amendment in mitigating phosphorus loss from non-calcareous neutral to alkaline soils.

     

Arsenate Displacement from Fly Ash in Amended Soils

Arsenic (As) is the biggest environment contaminant in most of the soils where fly ash is applied. Usually, it is not mobile and strongly adsorbed on to soil particles. However, in gypsum and phosphorus amended soils As may be much more mobile. A study in repacked columns was conducted to determine whether or not As becomes mobile when Ca(H₂PO₄)₂and CaSO₄are used as leaching solutions, and to compare the competitive interactions between PO₄-AsO₄and SO₄-AsO₄. Arsenic concentration in leachate was found to be approximately ten times greater when Ca(H₂PO₄)₂was used to leach the columns as compared to CaSO₄. A maximum concentration of 800 μg As L^-1was found in the leachate in this case, which is much higher than the groundwater limit of 50 μg L^-1for drinking water established by the United States Environmental Protection Agency. In fly ash, the portion of arsenate non-specifically adsorbed is believed to be much lower than that of specifically adsorbed. Sulfate anions were able to displace only non-specifically adsorbed arsenate. In this case the concentration of As in leachate was found to be within acceptable limits. On the other hand, phosphate can compete with arsenate for all available adsorption sites, non-specific and specific. Phosphate displacement of both forms of arsenates increases As mobility in both control and fly ash treatments.     

第四纪红色粘土发育的红壤中营养元素的淋失

A red soil derived from Quaternary red clay was employed to study nutrient leaching with soil columns repacked in laboratory. The objective was to identify the effects of fertilization practices on leaching patterns and magnitudes of Ca²⁺, Mg²⁺, K⁺, NH₄⁺, and NO₃^-. The treatments were CK (as a control), CaCO₃, CaSO₄, MgCO₃, Ca(H₂PO₄)₂, urea, KCl, and multiple (a mixture of the above-mentioned fertilizers). The fertilizers were added to the bare surface of the soil columns, and then the columns were leached with 120 mL deionized water daily through peristaltic pumps over a period of 92 days. Leaching processes of NH₄⁺, and NO₃^- were only measured in CK, urea, and multiple treatments which were directly related to N leaching. Results showed that sole application of CaSO₄, and Ca(H₂PO₄)₂ scarcely had any effect on the leaching losses of Ca²⁺, Mg²⁺, and K⁺; the application of MgCO₃ stimulated the leaching of Mg²⁺; the application of CaCO₃ promoted the leaching of Ca²⁺, Mg²⁺ and K⁺; urea treatment also promoted the leaching of K⁺ and NH₄⁺, and NO₃^- leaching mainly occurred at late stage of leaching process in particular; under KCl treatment, leaching of Ca²⁺, Mg²⁺, and K⁺ was promoted to a large extent; under multiple treatment, leaching of Ca²⁺, Mg²⁺, K⁺, NH₄⁺, and NO₃^- was all increased and NO₃^- was mainly leached at the end of leaching process and still had a trend of increase.     

原状土与装填土热特性的比较

土壤热特性是研究土壤—植物—大气系统中能量传输的必要参数。目前的研究集中在室内装填土柱上热特性与含水率、质地、温度和体积质量(容重)等因素的关系,田间条件下土壤结构对热特性影响的报道很少。该研究通过比较2种质地土壤田间原状土和室内装填土热特性的差异,初步探讨了不同含水率范围内结构形成对土壤热特性的影响。采集田间原状土,在室内利用热脉冲技术测定其热容量、热导率和热扩散率;然后将样品磨碎、过2mm土筛,填装后得到相同体积质量和含水率的装填土壤样品,并测定其热特性。结果表明,装填土和原状土的热容量基本一致;在中等含水率区域(砂壤土:0.07～0.24m3/m3;壤土:0.15～0.31m3/m3),重新装填后砂壤土和壤土的热导率分别降低了9.7%和9.8%。另外,结构形成增加了土壤热扩散率,在中等含水率区域尤其明显;在接近饱和区域,原状土与装填土的热扩散率趋于一致。因此,土壤结构形成对土壤热容量没有显著影响,但提高了中等含水率区域土壤的热导率和热扩散率。     

石灰土壤原状土柱上硼和锌的迁移

Leaching of boron （B） and zinc （Zn） can be significant in some pedomorphic conditions, which can cause contamination of shallow groundwater and economic losses. Boron and Zn adsorption and transport was studied using 8.4 cm diameter × 28 cm long intact columns from two calcareous soil series with differing clay contents and vadose zone structures： Lyallpur soil series, clay loam （fine-silty, mixed, hyperthermic Ustalfic Haplargid）, and Sultanpur soil series, sandy loam （coarse-silty, mixed, hyperthermic Ustollic Camborthid）. The adsorption isotherms were developed by equilibrating soil with 0.01 tool L^-1 CaCl2 aqueous solution containing varying amounts of B and Zn and were fitted to the Langmuir equation. The B and Zn breakthrough curves were fitted to the two-domain convective-dispersive equation. At the end of the leaching experiment, 0.11 L 10 g L^-1 blue dye solution was also applied to each column to mark the flow paths. The Lyallpur soil columns had a slightly greater adsorption partition coefficient both for B and Zn than the Sultanpur soil columns. In the Lyallpur soil columns, B arrival was immediate but the peak concentration ratio （the concentration in solution at equilibrium/concentration applied） was lower than that in the Sultanpur soil columns. The breakthrough of B in the Sultanpur soil columns occurred after about 10 cm of cumulative drainage in both the columns; the rise in effluent concentration was fast and the peak concentration ratio was almost 1. Zinc leaching through the soil columns was very limited as only one column from the Lyallpur soil series showed Zn breakthrough in the effluent where the peak concentration ratio was only 0.05. This study demonstrates the effect of soil structure on B transport and has implications for the nutrient management in field soils.     

Boron availability to plants from coal combustion by-products

Agronomic use of coal combustion by-products is often associated with boron (B) excess in amended soils and subsequently in plants. A greenhouse study with corn (Zea mays L.) as test plant was conducted to determine safe application rates of five fly ashes and one flue gas desulfurization gypsum (FDG). All by-products increased soil and corn tissue B concentration, in some cases above toxicity levels which are 5 mg hot water soluble B (hwsB) kg^?1 soil and 100 mg B kg^?1 in corn tissue. Acceptable application rates varied from 4 to 100 Mg ha^? for different by-products. Leaching and weathering of a high B fly ash under ponding conditions decreased its B content and that of corn grown in fly ash amended soil, while leaching of the same fly ash under laboratory conditions increased fly ash B availability to corn in comparison to the fresh fly ash. Hot water soluble B in fly ash or FDG amended soil correlated very well with corn tissue B. Hot water soluble B in fly ash amended soil could be predicted based on soil pH and B solubility in ash at different pH values but not so in the case of FDG. Another greenhouse study was conducted to compare the influence of FDG and Ca(OH)₂ on B concentration in spinach (Spinacia oleracea L.) leaves grown in soil amended with the high B fly ash. The Ca(OH)₂ significantly decreased tissue B content, while FDG did not affect B uptake from fly ash amended soil.     

红壤交换性钙、镁和钾的分布及施肥对其影响

A leaching experiment was Carried out with repacked soil columns in laboratory to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices.The treatments were CK(as a control),CaCO3,CaSO4,MgCO3,Ca(H2PO4)2,Urea,KCl,Multiple(a mixture of the above mentioned fertilizers) and KNO3,The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through perstaltic pumps over a period of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles ,i.o.,of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles,I.e.0-5cm,5-10cm,10-20cm,20-40cm,and 40-60cm,The results showed when applying Ca,Mg,and K to the bare surface of the soil columns,exchangeable Ca^2 ,Mg^2 ,and K^ in the upper layer of the soil profile increased correspondingly,with an extent depending mainly on the application rates of Ca,Mg,and K and showing a downward trend,CaCO3,CaSO4,MgCO3,and Ca(H2PO4)2 treatments had scarcely and effect on movement of exchangeable K^ ,while CaCO3,and CaSO4 treatments singnificantly promoted the downward movement of exchangealble Mg^2 although these two treatments had no obvious effect on leaching losses of Mg,The fact that under Urea treatment,exchangeable Ca^2 and Mg^2 ,were higher as compared to CK treatment showed urea could prevent leaching of exchangeable Ca^2 and Mg^2 ,the obvious downward movement of exchangeable Ca^2 and Mg^2 was noticed in KCl treatment ,In Multiple treatment,the downward movement of exchangeable Ca^2 and Mg^2 was evident,while that of K^ was less evident,Application of KNO3 strongly promoted the downward movement of exchangeable Ca^2 and Mg^2 in the soil profile.     

The estimation of losses of potassium and magnesium from chalky soils in southern England: laboratory studies

Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.
The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.
When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.
Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.     

Removal of Arsenic, Boron, and Selenium from Excavated Rocks by Consecutive Washing

This paper describes the leaching behavior and release mechanisms of arsenic (As), boron (B), and selenium (Se) from excavated rocks using sequential extraction for solid-phase fractionation, batch experiments with pH variation, and consecutive batch experiments with changes in the solid?Cliquid mixing ratios. Arsenic in the excavated rock was mostly found with the sulfides/organic matter fraction while majority of the leachable B and Se were associated with the exchangeable phases. The leaching of As was strongly pH dependent, Se was pH dependent only around the acidic region, and B was pH independent. Consecutive washing technique with deionized water effectively lowered the B and Se concentrations in the leachate below the drinking water standards of Japan, but was inefficient in the removal of As. Arsenic exhibited non-conservative leaching behavior and its movement was affected by processes like dissolution, precipitation, and pyrite oxidation. In contrast, B and Se behaved more conservatively, resulting in their easy removal from the excavated rock by simple washing and dilution.     

Differential leaching of cations and sulfate in gypsum amended soils

Abstract

An adequate supply of available Ca in the soil solution of the pegging zone during fruit development is required for production of high yields of high quality peanuts (Arachis hypogaea L.). On low Ca soils, application of gypsum during early bloom is recommended in order to ascertain adequate availability of Ca. Reaction of gypsum in soils under leaching conditions vary considerably and play an important role in fruit development and yield of peanuts. A laboratory study was conducted in leaching soil columns to investigate the effects of one gypsum amendment on leaching of Ca, K, Mg, and SO₄ to a depth of 8 cm (fruiting zone of peanut). Six soils of varying physical and chemical properties representative of major peanut growing soils in Georgia were utilized. Following leaching with 15 cm water through gypsum‐amended soil columns, 50% to 56% and 74% to 77% of applied Ca and SO₄, respectively, were leached below 8 cm in the sandy‐Carnegie, Dothan, Fuquay and Tifton soils. The respective values for the sandy clay loam‐Greenville and Faceville soils were 28% to 36% and 58% to 69%. Lower initial Ca status and greater leaching of Ca from the applied gypsum in the sandy soils as compared to sandy clay loam soils suggest greater beneficial effects of supplemental gypsum application for peanut production in the former soils than in the latter soils. Leaching of K or Mg (as percentage of Mehlich 1 extractable K or Mg) in gypsum‐amended treatment was considerably greater in sandy soils than that in the sandy clay loam soils. In view of the reported adverse effects of high concentrations of soil K and Mg in the fruiting zone on the yield and quality of peanuts, greater leaching of K and Mg from the fruiting zone in gypsum amended sandy soils enable them to maintain a favorable cation balance for the production of high yields of quality peanuts.     

有机无机磷肥配施对蔬菜地土壤磷素淋失的影响

利用土柱淋溶模拟实验研究化肥、有机肥以及有机无机P肥配施对蔬菜地土壤P素淋失的影响,结果表明,有机肥可明显提高土壤的有机P含量,促进土壤P素的淋失;在施P量相同的情况下,有机P肥所占的比例越大,淋出液总P、溶解总P、溶解有机P的浓度和累积淋失量就越高.在评价蔬菜地土壤P对水环境影响时,应把有机P作为评价指标.     

第四纪红粘土发育的红壤在施用石灰和石膏后元素的淋溶特征

本文利用模拟土柱试验研究了施用石灰和石膏对第四纪红粘土发育的红壤中元素淋溶过程的影响。结果表明,施用石灰后１０ｃｍ土层中除Ｃａ＾２＋以外的阳离子元素的淋失量减少,而ＳＯ４＾２－和ＨＣＯ３＾－的淋失量增加;施用石膏后１０ｃｍ土层中所有阳离子元素,特别是ＡＩ＾３＋的淋失量增加。红壤中Ｃａ＾２＋的淋失以自由态为主,施用石膏后与ＳＯ４＾２－结合的比例增加,不同处理中３０ｃｍ土层处铝的淋失以自由态为离,１０     

Comparing chloride transport in undisturbed and disturbed soil columns under turfgrass conditions

Abstract

Transport of surface applied chloride (Cl) in undisturbed soil columns with intact macropores was compared to disturbed, repacked columns of the same soil. The total amount of Cl that leached from 20 cm deep soil columns was 2.0 times higher for the undisturbed columns than for the disturbed columns, and the total quantity of leachate was 1.4 times higher for undisturbed columns than for the disturbed columns. Chloride recovered (mass basis) in layer #2 (6.7 to 13.4 cm) was 1.79 times higher and in layer #3 (13.4 to 20.0 cm) was 2.72 times higher for the disturbed soils than for the undisturbed. For the plant and thatch layer (0.0 to 2.0 cm) the opposite was observed, total Cl recovered from the undisturbed columns was 2.4 times higher than in the disturbed columns.     

The retention of nitrate in acid soils from the tropics

Abstract. In most soils of temperate regions nitrate is not held on soil surfaces and moves freely in solution. But when soils carry positive charges, nitrate is held as an exchangeable anion. As a result, leaching of nitrate is delayed relative to the movement of water. The delay can be predicted provided the anion exchange capacity (AEC) can be measured and the concentration of counter-anions is known. For soils with variable charge, the AEC varies with both pH and ionic strength, and the effective AEC should be determined under conditions similar to those in soil solution. A simple leaching method is described which satisfies this requirement. Delays in the leaching of nitrate measured in columns of repacked soil were strongly related to the AEC.     

The practice of leaching boron and soluble salts from fly ash-amended soils

The leachability of B and salts from two fly ash-amended soils was conducted in a column leaching experiment. Fly ash was applied to the surface 3 cm of a Baywood (acid) sand and an Arizo (calcareous) sandy, loam at 5% by weight; the columns were continously leached with Colorado River water at two different pH's. Boron from fly ash was solubilized more readily in the Baywood than in the Arizo soil. Addition of fly ash increased B levels in the leachates from 0.25 to 2.35 μg ml^?1 (Baywood) and 0.93 μg ml^?1 (Arizo). Acidified leaching water had no significant effect on B leaching patterns but resulted in leaching higher soluble salts. Approximately 348 and 161 cm of water for the Arizo and the Baywood soils respectively, would be required to reduce the B concentration below a critical limit for B sensitive crops. It is suggested that crops planted when fly ash is applied for disposal/recycling on land should be both salt and B tolerant.     

Effects of earthworms on nitrogen mineralization

The influence of earthworms (Lumbricus terrestris and Aporrectodea tuberculata) on the rate of net N mineralization was studied, both in soil columns with intact soil structure (partly influenced by past earthworm activity) and in columns with sieved soil. Soil columns were collected from a well drained silt loam soil, and before the experiment all earthworms present were removed. Next, either new earthworms (at the rate of five earthworms per 1200 cm³, which was only slightly higher than field numbers and biomass) were added or they were left out. At five points in time, the columns were analyzed for NH ₄ ⁺ , NO ₃ ^– , and microbial biomass in separate samples from the upper and lower layers of the columns. N mineralization was estimated from these measurements. The total C and N content and the microbial biomass in the upper 5 cm of the intact soil columns was higher than in the lower layer. In the homogenized columns, the C and N content and the microbial biomass were equally divided over both layers. In all columns, the concentration of NH ₄ ⁺ was small at the start of the experiment and decreased over time. No earthworm effects on extractable NH ₄ ⁺ were observed. However, when earthworms were present, the concentration of NO ₃ ^– increased in both intact and homogenized cores. The microbial biomass content did not change significantly with time in any of the treatments. In both intact and homogenized soil, N mineralization increased when earthworms were present. Without earthworms, both type of cores mineralized comparable amounts of N, which indicates that mainly direct and indirect biological effects are responsible for the increase in mineralization in the presence of earthworms. The results of this study indicate that earthworm activity can result in considerable amounts of N being mineralized, up to 90 kg N ha^–1 year^–1, at the density used in this experiment.     

Remediation of Lead Contaminated Soil by EDTA. I. Batch and Column Studies

Extraction using ethylenediaminetetraacetic acid (EDTA), and other chelates has been demonstrated to be an effective method of removal of Pb from many contaminated soils. However, column leaching of Pb from alkaline soils with EDTA has been problematic due to extremely low soil permeability. The first purpose of this study was to develop batch extraction procedures and methods of analysis of batch extraction data to provide Pb solubility information which can be used to model the column extraction of Pb from soils. The second purpose was to determine the effect of the addition of KOH and CaCl₂ to K₂H₂EDTA extract solution on both hydraulic conductivity and Pb removal. A Pb-contaminated soil sample was collected from an abandoned battery recycling facility. Both batch shaker extractions and column leaching experiments were completed using 5 different EDTA extract solutions. When only CaCl₂ was added to EDTA no change in the amount of Pb removed by batch extraction was observed. As expected, lead solubility was observed to decrease as pH was increased by the addition of KOH. However, Pb solubility was only slightly decreased by the addition of both CaCl₂ and KOH. The amount of time required to leach 6.0 L of extraction solution through the soil columns varied from 2 to 33 days. The addition of CaCl₂ and/or KOH resulted in increased soil hydraulic conductivity relative to the EDTA-only solution. The hydraulic conductivity was related to residual calcium carbonate content, suggesting that dissolution of CaCO₃ and subsequent production of CO₂ gas in the soil pores was partially responsible for the observed reductions in soil permeability. However, Pb removal was diminished with the addition of CaCl₂ and KOH because of the decreased Pb solubility and also kinetic limitations associated with the shorter residence time of the extract solution in the column.