Transport and transformation of sulfadiazine in soil columns packed with a silty loam and a loamy sand

Concerning the transport of the veterinary antibiotic sulfadiazine (SDZ) little is known about its possible degradation during transport. Also its sorption behaviour is not yet completely understood. We investigated the transport of SDZ in soil columns with a special emphasis on the detection of transformation products in the outflow of the soil columns and on modelling of the concentration distribution in the soil columns afterwards. We used disturbed soil columns near saturation, packed with a loamy sand and a silty loam. SDZ was applied as a 0.57 mg L(-1) solution at a constant flow rate of 0.25 cm h(-1) for 68 h. Breakthrough curves (BTC) of SDZ and its transformation products 4-(2-iminopyrimidin-1(2H)-yl)aniline and 4-hydroxy-SDZ were measured for both soils. For the silty loam we additionally measured a BTC for an unknown transformation product which we only detected in the outflow samples of this soil. After the leaching experiments the (14)C-concentration was quantified in different layers of the soil columns. The transformation rates were low with mean SDZ mass fractions in the outflow samples of 95% for the loamy sand compared to 97% for the silty loam. The formation of 4-(2-iminopyrimidin-1(2H)-yl)aniline appears to be light dependent and did probably not occur in the soils, but afterwards. In the soil columns most of the (14)C was found near the soil surface. The BTCs in both soils were described well by a model with one reversible (kinetic) and one irreversible sorption site. Sorption kinetics played a more prominent role than sorption capacity. The prediction of the (14)C -concentration profiles was improved by applying two empirical models other than first order to predict irreversible sorption, but also these models were not able to describe the (14)C concentration profiles correctly. Irreversible sorption of sulfadiazine still is not well understood.     

Effect of seepage conditions on chemical attenuation of arsenic by soils across an abandoned mine site

The effect of seepage velocity on the As leaching/adsorption by soils collected from abandoned mine sites was evaluated under batch equilibrium and different seepage settings. The breakthrough curves (BTCs) of As leaching from the mine soil column initially displayed the peak export and gradually leveled off over the leaching experiment. A similar As peak was observed after a flow interruption period. Adsorption by downgradient soils was clearly nonlinear, as Freundlich N was <1. In the BTCs of the layered columns, where downgradient soils were overloaded above the mine soil, the extended lag period of As appearance and lower steady-state As concentration observed for slow seepage velocity supported the idea of kinetically limited As attenuation driven by soil adsorption. The perturbation of As concentration was insignificant when the intra-column As concentration gradient was higher. The As concentration drop and time to recovery were greater for less adsorptive soil and fast seepage velocity. Desorption of As from soils retrieved from both batch adsorption and column experiment demonstrate hysteric behavior. The results of this work demonstrated that the risk of As leaching from an abandoned mine site can be greatly attenuated by intermediate downgradient soils via chemical adsorption, which tends to be kinetically limited and energetically hysteric (i.e., non-identical energy pathway).     

Movement of metolachlor and terbuthylazine in core and packed soil columns

Movement of metolachlor and terbuthylazine including a bromide tracer was studied in core and packed soil columns in PVC pipes (80 mm diameter, 15 mm depth) with two German soil types viz: silt loam and loamy silt. The breakthrough curves (BTCs) for bromide indicated some preferential flow of water both under conventional tillage (CN) and no-till (NT) simulation with silt loam soil. The herbicides leached to a greater extent in NT columns than in CN columns. Leaching was higher in loamy silt soil than in silt loam soil under CN conditions. This result is in agreement with the higher sorption capacity of silt loam having higher organic carbon compared to loamy silt having low organic carbon. Adsorption strength of the herbicides did not affect their breakthrough time, but was reflected in the slope and maximum height of the BTCs. The BTCs showed the expected inverse relationship between leaching and adsorption with greater mobility of the weakly-sorbed metolachlor than the more strongly sorbed terbuthylazine. Maximum amounts of the applied herbicides were recovered from the top soil layer in intact columns. Metolachlor was more mobile in packed columns than in core columns.     

Phosphorus leaching in soils amended with piggery effluent or lime residues from effluent treatment

Phosphorus (P) in wastes from piggeries may contribute to the eutrophication of waterways if not disposed of appropriately. Phosphorus leaching, from three soils with different P sorption characteristics (two with low P retention and one with moderate P retention) when treated with piggery effluent (with or without struvite), was investigated using batch and leaching experiments. The leaching of P retained in soil from the application of struvite effluent was determined. In addition, P leaching from lime residues (resulting from the treatment of piggery effluent with lime to remove P) was determined in comparison to superphosphate when applied to the same three soils. Most P was leached from sandy soils with low P retention when effluent with or without struvite was applied. More than 100% of the filterable P applied in struvite effluent was leached in sandy soils with low P retention. Solid, inorganic forms of P (struvite) became soluble and potentially leachable at pH<7 or were sorbed after dissolution if there were sufficient sorption sites. In sandy soils with low P retention, more than 39% of the total filterable P applied in recycled effluent (without struvite) was leached. Soil P increased mainly in surface layers after treatment with effluent. Sandy soils pre-treated with struvite effluent leached 40% of the P retained in the previous application. Phosphorus decreased in surface layers and increased at depth in the soil with moderate P retention after leaching the struvite effluent pre-treated soil with water. The soils capacity to adsorb P and the soil pH were the major soil properties that affected the rate and amount of P leaching, whereas the important characteristics of the effluent were pH, P concentration and the forms of P in the effluent. Phosphorus losses from soils amended with hydrated lime and lime kiln dust residues were much lower than losses from soils amended with superphosphate. Up to 92% of the P applied as superphosphate was leached from sandy soils with low P retention, whereas only up to 60% of the P applied in lime residues was leached. The P source contributing least to P leaching was the lime kiln dust residue. The amount of P leached depended on the water-soluble P content, neutralising value and application rate of the P source, and the pH and P sorption capacity of the soil.     

Evaluating equilibrium and non-equilibrium transport of bromide and isoproturon in disturbed and undisturbed soil columns

In this study, displacement experiments of isoproturon were conducted in disturbed and undisturbed columns of a silty clay loam soil under similar rainfall intensities. Solute transport occurred under saturated conditions in the undisturbed soil and under unsaturated conditions in the sieved soil because of a greater bulk density of the compacted undisturbed soil compared to the sieved soil. The objective of this work was to determine transport characteristics of isoproturon relative to bromide tracer. Triplicate column experiments were performed with sieved (structure partially destroyed to simulate conventional tillage) and undisturbed (structure preserved) soils. Bromide experimental breakthrough curves were analyzed using convective-dispersive and dual-permeability (DP) models (HYDRUS-1D). Isoproturon breakthrough curves (BTCs) were analyzed using the DP model that considered either chemical equilibrium or non-equilibrium transport. The DP model described the bromide elution curves of the sieved soil columns well, whereas it overestimated the tailing of the bromide BTCs of the undisturbed soil columns. A higher degree of physical non-equilibrium was found in the undisturbed soil, where 56% of total water was contained in the slow-flow matrix, compared to 26% in the sieved soil. Isoproturon BTCs were best described in both sieved and undisturbed soil columns using the DP model combined with the chemical non-equilibrium. Higher degradation rates were obtained in the transport experiments than in batch studies, for both soils. This was likely caused by hysteresis in sorption of isoproturon. However, it cannot be ruled out that higher degradation rates were due, at least in part, to the adopted first-order model. Results showed that for similar rainfall intensity, physical and chemical non-equilibrium were greater in the saturated undisturbed soil than in the unsaturated sieved soil. Results also suggested faster transport of isoproturon in the undisturbed soil due to higher preferential flow and lower fraction of equilibrium sorption sites.     

Impact of sewage sludge spreading on nickel mobility in a calcareous soil: adsorption–desorption through column experiments

A soil column adsorption–desorption study was performed on an agricultural calcareous soil to determine the impact of sewage sludge spreading on nickel mobility. Ni adsorption experiments were followed by desorption tests involving the following liquid extractants: water, calcium (100 mg/L), oxalic acid (525 mg/L equivalent to 100 mg carbon/L), and sludge extracts (0.5 and 2.5 g/L). Desorption tests were also conducted after sewage sludge spreading at three application rates (30, 75, and 150 t/ha). According to the breakthrough curve, Ni adsorption was irreversible and occurred mainly through interactions with calcite surface sites. Nickel desorption from the soil column was promoted in presence of significant dissolved organic carbon (DOC) concentration as observed with oxalic acid elution and sludge extract at 2.5 g/L. In sludge-amended soil columns, the maximum Ni levels occurred in first pore volumes, and they were positively correlated to the sludge application rate. The presence of DOC in leaching waters was the main factor controlling Ni desorption from the sludge-amended soil columns. This finding implies that DOC generated by sludge applied on calcareous soils might facilitate the leaching of Ni due to the formation of soluble Ni–organic complexes. Thus, sludge application can have potential environmental impacts in calcareous soils, since it promotes nickel transport by decreasing Ni retention by soil components.     

Lattice Boltzmann model for agrochemical transport in soils

Agrochemical transport in soils is complicated and involves physical, chemical and biochemical reactions; its mathematical modelling remains a challenging task. This paper presents a lattice Boltzmann model to simulate the agrochemical movement. The lattice Boltzmann model is a microscopic and process-based model, simulating the transport process by tracking chemical particles. The model presented in this paper is for one-dimensional vertical leaching and assumes that the chemical particles at the microscopic level move in five directions: one stagnant, two in vertical direction and two in an internal horizontal direction bounded by two reactive walls. Reactions at the walls are assumed to take place at two different rates, one in fast rate where the chemicals in the solution and on the wall are in an instant equilibrium, and the other in slow rate where the mass exchange rate between the chemicals in the solution and on the wall is a first-order kinetic. The reactions on both walls are assumed to occur instantly when the chemical particles moving in the internal direction hit the walls. To test the model, we measured the leaching of atrazine through soil columns in the laboratory. The results simulated with the lattice Boltzmann model are compared with the measured breakthrough curves and the non-equilibrium two-site convection-dispersion model; they all show close agreement. The transport parameters needed in the models are obtained from the measurement of adsorption isotherm of atrazine, bromide leaching in the same soil columns and calibration.     

Multi-process herbicide transport in structured soil columns: experiments and model analysis

Model predictions of pesticide transport in structured soils are complicated by multiple processes acting concurrently. In this study, the hydraulic, physical, and chemical nonequilibrium (HNE, PNE, and CNE, respectively) processes governing herbicide transport under variably saturated flow conditions were studied. Bromide (Br-), isoproturon (IPU, 3-(4-isoprpylphenyl)-1,1-dimethylurea) and terbuthylazine (TER, N2-tert-butyl-6-chloro-N4-ethyl-1,3,5-triazine-2,4-diamine) were applied to two soil columns. An aggregated Ap soil column and a macroporous, aggregated Ah soil column were irrigated at a rate of 1 cm h(-1) for 3 h. Two more irrigations at the same rate and duration followed in weekly intervals. Nonlinear (Freundlich) equilibrium and two-site kinetic sorption parameters were determined for IPU and TER using batch experiments. The observed water flow and Br- transport were inversely simulated using mobile-immobile (MIM), dual-permeability (DPM), and combined triple-porosity (DP-MIM) numerical models implemented in HYDRUS-1D, with improving correspondence between empirical data and model results. Using the estimated HNE and PNE parameters together with batch-test derived equilibrium sorption parameters, the preferential breakthrough of the weakly adsorbed IPU in the Ah soil could be reasonably well predicted with the DPM approach, whereas leaching of the strongly adsorbed TER was predicted less well. The transport of IPU and TER through the aggregated Ap soil could be described consistently only when HNE, PNE, and CNE were simultaneously accounted for using the DPM. Inverse parameter estimation suggested that two-site kinetic sorption in inter-aggregate flow paths was reduced as compared to within aggregates, and that large values for the first-order degradation rate were an artifact caused by irreversible sorption. Overall, our results should be helpful to enhance the understanding and modeling of multi-process pesticide transport through structured soils during variably saturated water flow.     

Transport of silver nanoparticles (AgNPs) in soil

The effect of soil properties on the transport of silver nanoparticles (AgNPs) was studied in a set of laboratory column experiments, using different combinations of size fractions of a Mediterranean sandy clay soil. The AgNPs with average size of ∼30 nm yielded a stable suspension in water with zeta potential of −39 mV. Early breakthrough of AgNPs in soil was observed in column transport experiments. AgNPs were found to have high mobility in soil with outlet relative concentrations ranging from 30% to 70%, depending on experimental conditions. AgNP mobility through the column decreased when the fraction of smaller soil aggregates was larger. The early breakthrough pattern was not observed for AgNPs in pure quartz columns nor for bromide tracer in soil columns, suggesting that early breakthrough is related to the nature of AgNP transport in natural soils. Micro-CT and image analysis used to investigate structural features of the soil, suggest that soil aggregate size strongly affects AgNP transport in natural soil. The retention of AgNPs in the soil column was reduced when humic acid was added to the leaching solution, while a lower flow rate (Darcy velocity of 0.17 cm/min versus 0.66 cm/min) resulted in higher retention of AgNPs in the soil. When soil residual chloride was exchanged by nitrate prior to column experiments, significantly improved mobility of AgNPs was observed in the soil column. These findings point to the importance of AgNP-soil chemical interactions as a retention mechanism, and demonstrate the need to employ natural soils rather than glass beads or quartz in representative experimental investigations.     

Leaching of the organophosphorus nematicide fosthiazate

Fosthiazate is an organophosphorus nematicide which was recently included in Annex I of the Directive 91/414/EEC under the clause that it should be used with special care in soils vulnerable to leaching. Thus, the leaching of fosthiazate was investigated in columns packed with three different soils which represented situations of high (site 2), intermediate (site 1) and low (site 3) leaching potential. The recommended dose of fosthiazate was applied at the surface of the soil columns and fosthiazate fate and transport was investigated for the next two months. Fosthiazate concentrations in the leachate collected from the bottom of the columns packed with soil from site 2 exceeded 0.1 microgl(-1) in most cases. This soil was characterized as acidic, indicating longer fosthiazate persistence, with low organic matter content, indicating weak adsorption, thus representing a situation vulnerable to leaching. In contrast, the lowest concentrations of fosthiazate in the leachate were evident in the columns packed with soil from site 3. This soil was characterized as alkaline, indicating faster degradation, with higher organic matter content, indicating stronger adsorption, thus representing a situation not favoring leaching of fosthiazate. The highest concentration of fosthiazate in the leachate from the columns packed with soil from site 2 was 3.44 microgl(-1) compared to 1.17 and 0.16 microgl(-1), which were the corresponding maximum values measured in columns packed with soil from sites 1 and 3, respectively. The results of the current study further suggest that fosthiazate is mobile in soil and can leach under conducive soil conditions like acidic soils with low organic matter content.     

Transport of anthracene and benz(a)anthracene through iron-quartz and three aquifer materials in laboratory columns

In groundwater systems, dissolved natural organic matter (NOM) can influence the mobility of organic contaminants by altering the contaminant behavior in water and solid phases. The transport of anthracene and benz(a)anthracene (B(a)A) was studied in the presence and absence of NOM and/or soil organic matter (SOM) in column experiments. The results show that sorption are related to the properties of polycyclic aromatic hydrocarbons (PAHs), NOM and SOM. In the Fe-quartz media, the amount of NOM (20 mg/l) in solution had a little effect on increasing the apparent solubility of anthracene and countering increased anthracene sorption. In the natural (Bemidji) soil, Suwannee river fulvic acid (SRFA, 20 mg/l) and Suwannee river humic acid (SRHA) in water did not compete with SOM for anthracene, indicating that SOM has higher partition efficiency for anthracene. It was also observed that slow diffusion through an organic phase apparently caused most of the observed tailing in column breakthrough curves (BTCs). Even though the fOC of washed Bemidji sediment was very low, the transport of B(a)A was retarded significantly, however, and the transport of B(a)A was shown to be facilitated by dissolved NOM.     

Reduced downward mobility of metribuzin in fly ash-amended soils

Metribuzin, a triazine herbicide, is poorly sorbed in the soils, therefore leaches to lower soil profile. Fly ash amendment, which enhanced metribuzin sorption in soils, may play a significant role in reducing the downward mobility of herbicide. Therefore, the present study reports the effect of Inderprastha fly ash amendment on metribuzin leaching in three soil types. Fly ash was amended at 1, 2 and 5% levels in the upper 15 cm of 30 cm long packed soil columns. Results suggested a significant reduction in the leaching losses of metribuzin in fly ash-amended columns of all the three soil types and effect increased with increase in the level of fly ash. Even after percolating water equivalent to 362 mm rainfall no metribuzin was recovered in the leachate of 5% fly ash-amended columns. Fly ash application affected both metribuzin breakthrough time and its maximum concentration in the leachate. Further, it resulted in greater retention of metribuzin in the application zone and better effect was observed in the organic carbon poor soils.     

Influence of methanol on retention of hydrophobic organic chemicals in soil leaching column chromatography

The influence of methanol in methanol-water mixed eluents on the capacity factor (k'), an important parameter which could depict leaching potential of hydrophobic organic chemicals (HOCs) in soil leaching column chromatography (SLCC), was investigated. Two reference soils, GSE 17201 obtained from Bayer Landwirtschaftszentrum, Monheim, Germany and SP 14696 from LUFA, Spencer, Germany, were used as packing materials in soil columns, and isocratic elution with methanol-water mixtures at different volume fractions of methanol (phi) were tested. Short-term exposure of the column (packed with the GSE 17201 soil) to the eluents increased solute retention by a certain (23% log-unit) degree evaluated through a correlation with the retention on the same soil column but unpreconditioned by methanol-containing eluents. Long-term exposure of soil columns to the eluents did not influence the solute retention. A log-linear equation, log k' = log k'(w) - S(phi), could well and generally describe the retention of HOCs in SLCC. For the compounds of homologous series, logk'(w) had good linear relationship with S, indicating the hydrophobic partition mechanism existing in the retention process.     

Soil attenuation of As(III,V) and Se(IV,VI) seepage potential at ash disposal facilities

Leachate from ash landfills is frequently enriched with As and Se but their off-site movement is not well understood. The attenuation potential of As and Se by soils surrounding selected landfills during leachate seepage was investigated in laboratory column studies using simulated ash leachate. As(III, V) and Se(IV, VI) concentrations as well as pH, flow rate, and a tracer were monitored in influent and effluent for up to 800 pore volumes followed by sequential desorption, extraction, and digestion of column segments. Column breakthrough curves (BTCs) were compared to predictions based on previously measured sorption isotherms. Early As(V) breakthrough and retarded As(III) breakthrough relative to predicted BTCs are indicative of oxidative transformation during seepage. For Se(VI), which exhibits linear sorption and the lowest sorption propensity, measured BTCs were predicted fairly well by equilibrium sorption isotherms, except for the early arrival of Se(IV) in one site soil, which in part, may be due to higher column pH values compared to batch isotherms. Most of the As and Se retained by soils during leaching was found to be strongly sorbed (60–90%) or irreversibly bound (10–40%) with <5% readily desorbable. Redox potential favoring transformation to the more sorptive valence states of As(V) and Se(IV) will invoke additional attenuation beyond equilibrium sorption-based predictions. With the exception of Se(IV) on one site soil, results indicate that attenuation by down-gradient soils of As and Se in ash landfill seepage will often be no less than what is predicted by equilibrium sorption capacity with further attenuation expected due to favorable redox transformation processes, thus mitigating contaminant plumes and associated risks.     

Evaluating non-equilibrium solute transport in small soil columns

Displacement studies on leaching of bromide and two pesticides (atrazine and isoproturon) were conducted under unsaturated steady state flow conditions in 24 small undisturbed soil columns (5.7 cm in diameter and 10 cm long) each collected from two sites differing in soil structure and organic carbon content in North Germany. There were large and irregular variabilities in the characteristics of both soils, as well as in the shapes of breakthrough curves (BTCs) of different columns, including some with early breakthrough and increased tailing, qualitatively indicating the presence of preferential flow. It was estimated that one preferential flow column (PFC) at site A, and four at site B, contributed, respectively to 11% and 58% of the accumulated leached fraction and to more than 80% of the maximum observed standard deviation (SD) in the field-scale concentration and mass flux of pesticides at two sites. The bromide BTCs of two sites were analyzed with the equilibrium convection-dispersion equation (CDE) and a non-equilibrium two-region/mobile-immobile model. Transport parameters of these models for individual BTCs were determined using a curve fitting program, CXTFIT, and by the time moment method. For the CDE based equilibrium model, the mean values of retardation factor, R, considered separately for all columns, PFCs or non-preferential flow columns (NPFCs) were comparable for the two methods; significant differences were observed in the values of dispersion coefficients of two sites using the two estimation methods. It was inferred from the estimated parameters of non-equilibrium model that 5-12% of water at site A, and 12% at site B, was immobile during displacement in NPFCs. The corresponding values for PFCs of two sites were much larger, ranging from 25% to 51% by CXTFIT and from 24% to 72% by the moment method, suggesting the role of certain mechanisms other than immobile water in higher degrees of non-equilibrium in these columns. Peclet numbers in PFCs of both sites were consistently smaller than five, indicating the inadequacy of the non-equilibrium model to incorporate the effect of all forms of non-equilibrium in PFCs. Overall, the BTCs of individual NPFCs, PFCs and of field average concentration at the two sites were better reproduced with parameters obtained from CXTFIT than by the moment method. The moment method failed to capture the peak concentrations in PFCs, but tended to describe the desorption and tail branches of BTCs better than the curve fitting approach.     

Leaching of terbumeton and terbumeton-desethyl from mini-columns packed with soil aggregates in laboratory conditions

Leaching of terbumeton (TER) and terbumeton-desethyl (TED) from mini-columns packed with natural soil aggregates was investigated. Five soil samples from the Champagne area (France) with different physicochemical parameters were used. The soil samples were hand-packed into a 50 mm column in laboratory conditions. An aqueous solution of TER or TED was percolated through the column and collected effluents were analyzed for TER or TED using HPLC-DAD. The leaching experiments showed that TER and TED were moderately mobile. TED was more mobile than TER, possibly because of its higher polarity. The proportion of organic matter affected the mobility of TER and TED through soil columns (r=0.971) and leaching was lowest for soil having the highest organic matter content (5.9%). TER and TED were not significantly influenced by leaching solution composition (deionized water or CaCl(2) solution), but were strongly affected by soil packing. Packing resulted in less rapid release of compounds suggesting that unpacking may have contributed to preferential pathways through the soil columns. Increasing contact time between TER and soils before leaching decreased the mobility of TER and increased its persistence in soils. Indeed, 76% of TER was released when leaching started after a 15 h contact time whereas it was down to 26% after an aging treatment of 360 h. A proportion of TER (from 8% to 32%) and TED (from 8% to 17%) remained in soil. Associated to its high stability in soils this could in part account for a very slow transfer over the years towards the groundwater.     

Influence of organic acids on the transport of heavy metals in soil

Vegetation historically has been an important part of reclamation of sites contaminated with metals, whether the objective was to stabilize the metals or remove them through phytoremediation. Understanding the impact of organic acids typically found in the rhizosphere would contribute to our knowledge of the impact of plants in contaminated environments. Heavy metal transport in soils in the presence of simple organic acids was assessed in two laboratory studies. In the first study, thin layer chromatography (TLC) was used to investigate Zn, Cd, and Pb movement in a sandy loam soil as affected by soluble organic acids in the rhizosphere. Many of these organic acids enhanced heavy metal movement. For organic acid concentrations of 10mM, citric acid had the highest R(f) values (frontal distance moved by metal divided by frontal distance moved by the solution) for Zn, followed by malic, tartaric, fumaric, and glutaric acids. Citric acid also has the highest R(f) value for Cd movement followed by fumaric acid. Citric acid and tartaric acid enhanced Pb transport to the greatest degree. For most organic acids studied, R(f) values followed the trend Zn>Cd>Pb. Citric acid (10mM) increased R(f) values of Zn and Cd by approximately three times relative to water. In the second study, small soil columns were used to test the impact of simple organic acids on Zn, Cd, and Pb leaching in soils. Citric acid greatly enhanced Zn and Cd movement in soils but had little influence on Pb movement. The Zn and Cd in the effluents from columns treated with 10mM citric acid attained influent metal concentrations by the end of the experiment, but effluent metal concentrations were much less than influent concentrations for citrate <10mM. Exchangeable Zn in the soil columns was about 40% of total Zn, and approximately 80% total Cd was in exchangeable form. Nearly all of the Pb retained by the soil columns was exchangeable.     

Mobility of Zn, Cd and Pb in soils as affected by poultry litter extract--II. Redistribution among soil fractions

The application of poultry litter to metal-contaminated soils may influence metal leaching and distribution of metals among soil fractions. Soil columns (one uncontaminated control, one metal-amended, and two metal-contaminated soils) were leached with H2O, CaCl2, EDTA, and poultry litter extract (PLE) solutions. After leaching, the soil samples in the columns were sequentially extracted for water soluble (WS), exchangeable (EXC), organic matter (OM), Mn oxide (MNO), amorphous Fe oxide (AFEO), crystalline Fe oxide (CFEO) and residual (RES) fractions. The OM fraction showed high retention for Zn from the PLE. The EDTA redistributed Zn, Cd and Pb from the EXC, OM and MNO fractions to the WS fraction. The PLE usually solubilized more Zn and Cd from the EXC fraction than CaCl2. Neither PLE nor CaCl2 mobilized Pb. The application of poultry litter on metal-contaminated soils might cause Zn and Cd redistribution from the EXC to the WS fraction and enhance metal mobility.