Phosphate sorption in some representative soils of Bangladesh

An experiment was conducted to observe the phosphate sorption potential of some soils of Bangladesh. Three soil series of calcareous origin, namely Sara (Aquic Eutrochrept), Gopalpur (Aquic Eutrochrept) and Ishurdi (Aeric Haplaquept), and two soil series of non-calcareous origin, namely Tejgaon (Rhodic Paleustult) and Ghatail (Aeric Haplaquept), were selected. The soils were equilibrated with dilute solution of calcium chloride containing graded concentrations of phosphate (0, 1, 2, 5, 10, 25 and 50?μg?P?mL^?1), and the amount of phosphate sorbed or desorbed was determined. Although all the soils showed potential for sorbing phosphate from applied phosphorus, their ability to sorb phosphorus differed. Increasing rates of phosphate application increased the amount of P sorption but reduced phosphate sorption percentage in all soils except Tejgaon. Phosphate was sorbed by the soils in the order: Tejgaon > Ghatail > Ishurdi > Gopalpur > Sara at 50?μg?P?mL^?1 application. Soils possessing higher amounts of free iron oxide and clay sorbed more phosphate from applied phosphorus.     

Copper and zinc sorption on some B horizons of Quebec soils

Abstract

The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases.

During the pH‐dependent sorption of Cu and Zn on six B horizons of Quebec soils, it was found that ions were released into solution thus altering the charge generated by the soil at low pH and the sorption behavior of Cu and Zn. The solid phase most likely to control the level of ions in solution is believed to be the amorphous and oxide forms of Al and Fe. The dissolution of these metal oxide or hydrous oxide materials also releases cations adsorbed on, or occluded in, the amorphous material.     

Effect of liming on hexazinone sorption and desorption behavior in various soils

Liming is a practice commonly used to modify soil acidity, neutralize aluminum, and increase calcium and magnesium in the soil. Liming can change herbicide retention processes and consequently weed control and potential environmental contamination. The effects of liming on the sorption and desorption of hexazinone in different soils were evaluated. Samples from seven Brazilian soils were collected and separated into two subsamples, with and without limestone incubation. Hexazinone was quantified using ultra high-performance liquid chromatography. The sorption and desorption coefficients were determined in soils using Freundlich isotherms. Increasing the pH did not alter the sorption kinetics of hexazinone in the same soil class. The shortest sorption time of hexazinone occurred in soils with higher organic matter (OM) and clay content. Liming reduced the sorption and increased the desorption of hexazinone in the soils, which was caused by the increase in pH and reduction of OM content. Although the application of limestone increased desorption, the rate at which this process occurred was less than the sorption rate of hexazinone in most cases. In alkaline soils, the recommended dose of hexazinone for pre-emergence application should be low to avoid leaching and reduce the contamination of groundwater resources.     

Effect of heating on phosphate sorption and availability in some north-east Nigerian soils

Studies on phosphate sorption and availability in some north-east Nigerian soils showed that phosphate adsorption and inorganic-P concentrations increased considerably after the soil was heated either in a furnace or during the field-burning of straw. The increase in phosphate adsorption after heating was thought to be caused by an increase in free Fe and A1 oxides, whereas the high contents of exchangeable Ca and possibly carbonates and hydroxyl ions in the ash were probably responsible for the increase in phosphate sorption after field-burning of straw. Investigations into the availability of P to maize over a 7-d period of growth showed that there was no significant nutritional benefit from the P released after soil heating. The effect of heating was to increase P sorption and so reduce P in solution and P availability.     

Effect of liming on phosphate sorption by acid soils

The sorption of phosphate (P) by four strongly acid Fijian soils from 0.01 M CaCl₂ decreased with increasing pH up to pH 5.5–6.0 and then increased again. The initial decrease in P sorption with increasing pH appears to result from an interaction between added P, negative charge, and the electrostatic potential in the plane of sorption. The results of a sorption study, involving KCl or CaCl₂ of varying concentrations as the background electrolyte and using Nadroloulou soil incubated with KOH or Ca(OH)₂, suggested that the increase in P sorption at pH values > 6.0 was caused by the formation of insoluble Ca-P compounds. For some soils this is consistent with the results of an isotopic-exchange study in which incubation with lime caused marked reductions in the amounts of exchangeable P at high pH.     

Competitive sorption of cadmium and lead in acid soils of Central Spain

The bioavailability and ultimate fate of heavy metals in the environment are controlled by chemical sorption. To assess competitive sorption of Pb and Cd, batch equilibrium experiments (generating sorption isotherms) and kinetics sorption studies were performed using single and binary metal solutions in surface samples of four soils from central Spain. For comparisons between soils, as well as, single and binary metal solutions, soil chemical processes were characterized using the Langmuir equation, ionic strength, and an empirical power function for kinetic sorption. In addition, soil pH and clay mineralogy were used to explain observed sorption processes. Sorption isotherms were well described by the Langmuir equation and the sorption kinetics were well described by an empirical power function within the reaction times in this study. Soils with higher pH and clay content (characterized by having smectite) had the greatest sorption capacity as estimated by the maximum sorption parameter (Q) of the Langmuir equation. All soils exhibited greater sorption capacity for Pb than Cd and the presence of both metals reduced the tendency for either to be sorbed although Cd sorption was affected to a greater extent than that of Pb. The Langmuir binding strength parameter (k) was always greater for Pb than for Cd. However, these k values tended to increase as a result of the simultaneous presence of both metals that may indicate competition for sorption sites promoting the retention of both metals on more specific sorption sites. The kinetic experiments showed that Pb sorption is initially faster than Cd sorption from both single and binary solutions although the simultaneous presence of both metals affected the sorption of Cd at short times while only a minor effect was observed on Pb. The estimated exponents of the kinetic function were in all cases smaller for Pb than for Cd, likely due to diffusion processes into micropores or interlayer space of the clay minerals which occurs more readily for Cd than Pb. Finally, the overall sorption processes of Pb and Cd in the smectitic soil with the highest sorption capacity of the studied soils are slower than in the rest of the soils with a clay mineralogy dominated by kaolinite and illite, exhibiting these soils similar sorption rates. These results demonstrate a significant interaction between Pb and Cd sorption when both metals are present that depends on important soil properties such as the clay mineralogy.     

Effects of heating and autoclaving on sorption and desorption of phosphorus in some forest soils

A number of biological and chemical processes may affect soil phosphorus availability when forest fires occur, partly as a result of heating. We describe here a laboratory experiment to study the effects of soil heating on changes in sorption and desorption of P. Autoclaving was also included as an additional treatment of moist heating under pressure. Five forest soils (two Podzols, one Arenosol, one Luvisol and one Alisol) were heated to 60°C, 120°C and 250°C or autoclaved for 30 min. They were repeatedly extracted with Bray I and analysed for inorganic and organic P fractions. The desorbed P data were fitted to an asymptotic exponential equation to obtain the desorption rate and capacity parameters. Podzol and Arenosol soils showed a quick P desorption after heating, while Luvisol and Alisol soils showed a slow desorption rate. The immediate increase in available P that occurred after heating or autoclaving originated mostly from solubilisation of microbial metabolites and soil organic components. Autoclaving decreased P sorption capacity in all soils, but the effects of heating on P sorption differed among soils. Except for one of the soils, the low P-fixing soils (Podzol and Arenosol) showed a decrease in P sorption when heated to high temperatures, whereas the high P-fixing soils (Luvisol and Alisol) showed little changes after heating. Fire intensity and soil characteristics are important factors determining short-term and long-term soil P dynamics.     

Partition of Cd,Cu, Pb and Zn among mineral particles during their sorption in soils

Journal of Soils and Sediments - Heterogeneity of soil mineral particles may lead to the misinterpretation of bulk sorption data on their role in metal sorption, which may be resolved through the...     

Parameterization and regionalization of Cd sorption characteristics of sandy soils. I. Freundlich type parameters

Cd sorption isotherms (n = 24) were established for arable, sandy soils of the ‘Fuhrberger Feld’ catchment area northeast of Hannover (Germany) using 0.01 M_c Ca(NO₃)₂ solution with Cd additions ranging from 0 to 44 μM_c Cd. Alternative fractions of initially (prior to analysis) sorbed Cd (S₀) were added to the amount sorbed during the experiments. The Freundlich equation was fitted to the resulting isotherms. The obtained retention parameters k and M varied with respect to the different S₀ fractions. Isotherms corrected with Cd_EDTA as S₀ fraction were nonlinear in their log-form. The highest degree of log-linearity is obtained if S₀ is characterized by 40% of the agua regia extractable Cd. The corresponding k values ranged from 36 to 1275 g^1-M L^M kg^?1 (mean 338 g^1-M L^M kg^?1, cv = 92%). The Freundlich exponent M showed less variation (0.7 to 1.1, cv = 12%) with a mean of 0.88. Functions based on these parameters predicted Cd concentrations in Ca(NO₃)₂?soil suspensions well (r² = 0.96) but were hardly related to Cd concentrations of ‘fresh’ soil solutions (r² = 0.20).     

Adsorption and desorption of Cd on humic acid fraction of soils

The adsorption of ionic Cd has been investigated on three humic acids isolated from podzol, rendzina and brown Mediterranean soils of Tuscany. The adsorption isotherms have been determined at 5 and 25°C. Cadmium adsorption was described by the Langmuir adsorption equation. Langmuir parameters were related to the functional groups content of humic acids and decreased in the following order: rendzina>brown Mediterranean soil>podzol. Adsorption was independent on temperature and increased with pH. Desorption experiments with 0.1 N NH₄OAc and 0.25 M Cu (OAc)₂ proved that Cd is adsorbed on humic acid about 50% in an exchangeable form and 50% in coordination complexes.     

几种典型酸性旱地土壤磷吸附的关键影响因素

以几种典型的酸性旱地土壤为研究对象,测定了土壤磷的等温吸附曲线,描述土壤磷的吸附特征,分析土壤最大吸磷量与土壤理化性质之间的关系,通过通径分析等方法明确了影响磷吸附的关键土壤因素。结果表明:土壤粘粒、游离态氧化铝(Al_d)、非晶质氧化铝(Al_o)及有机络合态铝(Al_p)的含量均与最大吸磷量(X_m)呈极显著正相关(P0.01),土壤pH值与X_m呈极显著负相关(P0.01);非晶质铁铝氧化物含量(Feo+Al_o)与X_m有显著的正相关关系(r=0.62,P=0.01);而土壤有机质、游离态氧化铁(Fe_d)、非晶质氧化铁(Fe_o)及有机络合态铁(Fe_p)的含量对X_m均无显著影响(P0.05)。即在本研究区域内,pH值越低,粘粒含量越高的土壤,其铝氧化物、非晶质铁铝氧化物(Fe_o+Al_o)含量越高,土壤的固磷能力越强。粘粒含量可能是影响土壤吸磷能力的一个最关键因素,其次为游离态氧化铝Al_d、非晶质氧化铝Al_o、有机络合态铝Al_p及土壤pH值等,其中各形态氧化铝对X_m的影响效应主要是通过与粘粒的间接作用来实现。     

Zinc sorption by acid tropical soils as affected by cultivation

The sorption of zinc (Zn) by two acid tropical soils, Mazowe clay loam (kaolinitic, coarse, Rhodic Kandiustalf) and Bulawayo clay loam (coarse, kaolinitic, Lithic Rodustalf), was studied over a wide range of Zn solution concentrations. Samples of the two soils used in the experiments were collected at both uncleared, uncultivated (virgin) sites and cultivated sites. The two virgin soils showed similar abilities to bind Zn. Mazowe soil (40 g organic matter kg^?1) presented the highest affinity for Zn. Yet, Bulawayo soil (23.5 g organic matter kg^?1) sorbed almost the same amount. Bulawayo soil had higher pH and Fe and Mn-oxide content than Mazowe soil. Once cultivated, the two soils behaved quite differently. After 50 years, Mazowe soil had lost 60% of its organic matter and effective cation exchange capacity (ECEC). In this soil, Zn sorption capacity had also been decreased by 60%. Clearing and 10 years under cultivation had affected neither the organic matter content nor the ECEC of Bulawayo soil. For this soil, Zn sorption was even higher in the cultivated soil, presumably due to an increase in the amount of Fe and Mn oxide from subsoiling. Zinc sorption was dependent upon pH, with retention dramatically increasing in the pH range 6–7. Sorption occurred at pH values below the point of zero charge (PZC), indicating that the sorption reaction can proceed even in the presence of electrostatic repulsion between the positively charged soil surface and the cation. In the two soils, the reversibility of the sorption reaction was very low. More than 90% of the sorbed Zn was apparently strongly bonded.     

伊朗西部地区碱性土壤中共离子对Zn吸附的影响

Zinc(Zn) is essential to plant growth and relatively mobile in soils.This study was conducted to assess the effect of common ions(Ca 2+,K +,Na +,NH + 4,Cl,NO 3,and H 2 PO 4) on sorption of Zn in surface samples of ten calcareous soils from western Iran using 10 mmol L 1 KCl,KNO 3,KH 2 PO 4,Ca(NO 3) 2,NaNO 3,and NH 4 NO 3 solutions as background electrolytes.The results indicated that both NH + 4,K +,and Ca 2+ equally decreased Zn sorption as compared to Na +.Zinc sorption was decreased by H 2 PO 4 as compared to NO 3 and Cl.The Langmuir and Freundlich equations fitted closely to the sorption data of all ions.The Langmuir maximum,bonding energy constant,and Freundlich distribution coefficient for Zn sorption differed among the various ionic background electrolytes.Langmuir sorption parameters showed that the presence of H 2 PO 4 decreased the maximum Zn adsorbed,but increased the bonding energy.Although K + and NH + 4 equally influenced maximum Zn adsorbed,they differed in their effect on the distribution coefficient of Zn in soils.Values of saturation index calculated using Visual MINTEQ indicated that at the low Zn concentration,Zn solubility was controlled by sorption reactions and at the high Zn concentration,it was mainly controlled by sorption and mineral precipitation reactions,such as precipitation of Zn 3(PO 4) 2.4H 2 O,Zn 5(OH) 6(CO 3) 2,and ZnCO 3.For most ionic background electrolytes,soil pH,CaCO 3,and cation exchange capacity(CEC) were significantly correlated with sorption parameters.     

几种铵盐对土壤吸附Cd2+和Zn2+的影响

采用平衡吸附法,研究了不同铵盐对潮褐土、红壤吸附Cd2+、Zn2+的影响。结果表明,土壤对Cd2+、Zn2+的吸附量随平衡溶液中Cd2+、Zn2+浓度的增加而增加;潮褐土和红壤对Cd2+、Zn2+的最大吸附量为:Zn2+ Cd2+,且潮褐土红壤;随NH4HCO3浓度的增加,两种土壤对Cd2+、Zn2+的吸附率显著提高,NH4Cl、NH4NO3和(NH4)2SO4抑制红壤对Cd2+、Zn2+的吸附及潮褐土对Cd2+的吸附,对潮褐土Zn2+的吸附率影响不显著;铵盐浓度相同时,红壤对Cd2+吸附率为:NH4HCO3NH4ClNH4NO3≈ (NH4)2SO4,红壤对Zn2+吸附率为:NH4HCO3NH4Cl NH4NO3(NH4)2SO4。     

The sorption of Cd and Zn by different soils in the presence of dissolved organic matter from sludge

Dissolved organic matter (DOM) is one of the important factors affecting metal mobility and phytotoxicity in the soils receiving sewage sludge. The aim of this study was to investigate the effects of DOM from anaerobically digested dewatered sludge on Cd and Zn sorption by three different soil types (calcareous clay loam, calcareous sandy loam and acidic sandy loam) of different physico-chemical properties through batch studies. The addition of DOM significantly reduced the Cd and Zn sorption capacity by a factor of 2.1–5.7 for Cd and 2.3–13.7 for Zn for these three soils as seen by their K values in the Freundlich equation compared to the control receiving no DOM, suggesting that DOM had a stronger inhibitory effect on Zn sorption than that of Cd. The reduction in metal sorption caused by DOM was very apparent in the pH range of 5 to 8, with a maximum inhibition on metal sorption occurring at pH 7–7.5 especially for Zn but the effect was minimal at lower pH. At a DOM concentration of < 200 mg C l^− 1, Cd and Zn sorption by all the three soils decreased with an increase in DOM concentration. At each given DOM concentration, the inhibition of metal sorption of the different soil types increased in the following order: acidic sandy loam < calcareous sandy loam < calcareous clay loam. DOM derived from sludge would significantly reduce metal sorption and increase its mobility through the formation of soluble DOM–metal complexes and poses risk of metal leaching and phytotoxicty in near-neutral and alkaline soils.     

Adsorption and translocation of sulfur in some tropical acid soils

In view of growing concern about sulfur (S) deficiency, we attempted to study the effect of soil characteristics on the adsorption and translocation of S in soils. Laboratory experiments were conducted with five surface soils collected from three regions in the state of Orissa (Eastern India). In an adsorption study, all the soils were equilibrated with graded doses of potassium sulfate (K₂SO₄). Freundlich adsorption isotherms provided good fit to S adsorption data. Free Fe₂O₃ and Al₂O₃ in the soils were primarily responsible for retaining added S in soils. Further, studies on the movement of sulfate‐S in 30‐cm plexiglass columns, where radio‐labeled S along with water (5 cm) was applied as gypsum and K₂SO₄, showed that K₂SO₄‐S migrated deeper than gypsum‐S. Sulfur moved deeper in case of initially water‐saturated soils than in initially air‐dry soils.     

Cadmium sorption by two acid soils as affected by clearing and cultivation

Abstract

The objective of this study was to determine the effect of clearing and cultivation on the sorption of cadmium (Cd) by two acid soils from Zimbabwe with differing cultivation stories. In their original state, not cleared‐not cultivated (virgin soils), the two soils exhibited noticeable and similar capacities to sorb Cd. The Mazowe soil contains the highest level of organic matter (40 g kg^‐1) and a effective cation exchange capacity (ECEC) of 144 mmol_c kg^‐1. Yet, Bulawayo soil (23.5 g kg^‐1 organic matter and ECEC of 146 mmol_c kg^‐1) has higher pH and Mn and Fe oxide content and these characteristics seemed to counteract the effect of lower organic matter. After 50 years of cultivation, The Mazowe soil has lost 60% of its organic matter and ECEC, and consequently the ability of its soil matrix to bind Cd has proportionally decreased. In Bulawayo (cleared in 1983 and first ploughed in 1984), on the contrary, the organic matter and ECEC of the cultivated soil remains over 95% of the values on its virgin counterpart. In this soil, the retaining ability for Cd has not still been affected. In the two soils Cd sorption was highly pH‐dependent. The extent of sorption was minimal under acidic conditions and increased sharply as the pH was raised. The immediate reversibility of the sorption process proved to be very low. When sorption and desorption data were compared it was clear that soil characteristics like high organic matter and oxide content which showed to enhanced Cd sorption, contributed at the same time to slow down the backward reaction.     

Forms of aluminium in some acid permanent grassland soils

The more labile forms of aluminium in a range of soils from areas of permanent grassland were determined with a number of selective extractants. The amounts of exchangeable A1 extracted with molar KCl were dependent upon pH, while the amounts exchangeable with 0.3 M LaCl³, although much greater, were not well correlated with pH. There were good correlations between soil organic C content and A1 extracted by (i) 0.5 M EDTA and (ii) 0.1 M potassium pyrophosphate. Pyrophosphate extracted greater amounts than any of the other extractants (sodium citrate/dithionite, ammonium oxalate (dark), acid oxalate (UV radiation), as well as those already mentioned). It was concluded that much of the extractable A1 in soils was associated with organic matter. Addition of lime to one of the soils reduced the amount of A1 extracted by all reagents except dithionite and acid oxalate solutions. There were considerable differences between soils in their release of A1 to continuous leaching with 0.01 M CaCl². Despite these differences between the soils in organically bound extractable Al, the differences in the amounts and patterns of release of A1 with CaCl² did not appear to be related to organic matter contents, nor to the other determined properties.     

Differences in sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid on artificial soils as a function of soil pre-aging

Purpose

The sorption behavior of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) to three different artificial soil mixtures was investigated. Artificial soils serve as model systems for improving understanding of sorption phenomena.

Materials and methods

The soils consisted of quartz, ferrihydrite, illite, montmorillonite, and charcoal. In a previous study, several selected mixtures had been inoculated with organic matter, and microbial aging (incubation) had been performed for different periods of time (3, 12, and 18?months) before conducting the sorption experiments. The effect of this pre-incubation time on the sorption behavior was determined. Interaction of MCPA with soil surfaces was monitored by aqueous phase sorption experiments, using high-performance liquid chromatography/ultraviolet and in selected cases Fourier-transformed infrared spectroscopy.

Results and discussion

The sorption behavior showed large differences between differently aged soils; Freundlich and linear sorption model fits (with sorption constants K _f , 1/n exponents, and K _d values, respectively) were given for pH?=?3 and the unbuffered pH of ??7. The largest extent of sorption from diluted solutions was found on the surfaces with a pre-incubation time of 3?months. Sorption increased at acidic pH values.

Conclusions

Regarding the influence of aging of artificial soils, the following conclusions were drawn: young artificial soils exhibit stronger sorption at lower concentrations, with a larger K _f value than aged soils. A correlation with organic carbon content was not confirmed. Thus, the sorption characteristics of the soils are more influenced by the aging of the organic carbon than by the organic carbon content itself.