Papers by Fernando Garrido
Chemosphere, 2006
In situ stabilization of toxic elements in contaminated soils by the addition of amendments is be... more In situ stabilization of toxic elements in contaminated soils by the addition of amendments is being considered as an effective technique for remediation. In this paper, we performed both kinetics and equilibrium-based sorption experiments of three toxic elements (As, Cd and Tl) in soils amended with two by-products (phosphogypsum and sugar foam, rich in gypsum and calcium carbonate, respectively) to ascertain the feasibility of their application for improving the sorption capacity of As, Cd and Tl from the soil at 25, 35 and 50°C. Kinetic studies indicated that the sorption follows a pseudo-second-order (PSO) kinetics and the sorption is a two-step diffusion process where both film and intraparticle diffusion played important roles in the sorption mechanisms of the elements. The Langmuir isotherms applied for sorption studies showed that the estimated maximum sorption capacity of the elements in control and amended soils decreased in the order of Cd > As > Tl. Using the thermodynamic equilibrium parameters obtained at different temperatures, the thermodynamic constants of sorption (DG, DH and DS) were also evaluated, indicating spontaneous and endothermic nature of the process, except Tl which was exothermic. An optimal scaling procedure was undertaken to determine the relationships between the kinetic and equilibrium sorption parameters. By means of statistical analysis it was seen that these inter-parametric relationships are dependent on the element nature.
European Journal of Soil Science, 2004
Lime, gypsum and various gypsum-like by-products have long been applied to soil surfaces as ameli... more Lime, gypsum and various gypsum-like by-products have long been applied to soil surfaces as ameliorants of soil acidity and aluminium and manganese toxicity. We examined changes in chemical and mineralogical properties at two different depths in two acid soils one year after the application of gypsum, phosphogypsum þ dolomitic residue, red gypsum þ dolomitic residue, sugar foam, and sugar foam þ mined gypsum. All treatments were found to increase the proportion of Ca 2þ and decrease those of Al 3þ and Mn 2þ in the exchange complex of the surface and subsurface horizons, thus reducing its effective Al and Mn saturation. However, the mined gypsum treatment resulted in losses of Mg 2þ from the Ap horizon of the soils, and the sugar foam treatment was not so effective with the AB horizons as the other treatments. The combined application of both gypsum-like by-products and the dolomitic residue proved the most effective choice with a view to reducing the effective Al and Mn saturation of the exchange complex in the Ap and AB horizons. In addition, both treatments reduced Mg 2þ losses at both depths. Finally, all treatments resulted in the formation and retention on mineral and organic surfaces of a large fraction of the Al 3þ released by exchange with Ca 2þ as Al polymers. This is quite consistent with the observed changes in the CuCl 2 -, oxalate-and DTPA-extractable Al contents as well as by SEM and EDS analyses. Based on these results, the use of the appropriate mixtures of these by-products is an effective alternative to that of mined gypsum and lime to alleviate soil acidity and reduce toxic concentrations of Al 3þ and Mn 2þ in agricultural acid soils.
Soil Science Society of America Journal, 2000
... Method for In Situ Field Calibration of Fiber Optic Miniprobes. Fernando Garrido,; Masoud Gho... more ... Method for In Situ Field Calibration of Fiber Optic Miniprobes. Fernando Garrido,; Masoud Ghodrati and; Chris G. Campbell. Division of Ecosystem Sci., Dep. of Environmental Science, Policy, and Management, Univ. of California, Berkeley, CA 94720-3110 USA. Abstract. ...
Geoderma, 2005
The bioavailability and ultimate fate of heavy metals in the environment are controlled by chemic... more 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. D
Soil Science Society of America Journal, 1999
Small-scale variations in transport parameters may have a profound influence on larger scale flow... more Small-scale variations in transport parameters may have a profound influence on larger scale flow processes. Fiber-optic miniprobes (FOMPs) provide the opportunity to continuously measure solute resident concentration in small soil volumes. A 20-channel multiplexed-FOMP ...
Hydrological Processes, 2002
The natural heterogeneity of water and solute movement in hillslope soils makes it difficult to a... more The natural heterogeneity of water and solute movement in hillslope soils makes it difficult to accurately characterize the transport of surface-applied pollutants without first gathering spatially distributed hydrological data. This study examined the application of time-domain reflectometry (TDR) to measure solute transport in hillslopes. Three different plot designs were used to examine the transport of a conservative tracer in the first 50 cm of a moderately sloping soil. In the first plot, which was designed to examine spatial variability in vertical transport in a 1·2 m2 plot, a single probe per meter was found to adequately characterize vertical solute travel times. In addition, a dye and excavation study in this plot revealed lateral preferential flow in small macropores and a transport pattern where solute is focused vertically into preferential flow pathways. The bypass flow delivers solute deeper in the soil, where lateral flow occurs. The second plot, designed to capture both vertical and lateral flow, provided additional evidence confirming the flow patterns identified in the excavation of the first plot. The third plot was designed to examine lateral flow and once again preferential flow of the tracer was observed. In one instance rapid solute transport in this plot was estimated to occur in as little as 3% of the available pore space. Finally, it was demonstrated that the soil anisotropy, although partially responsible for lateral subsurface transport, may also homogenize the transport response across the hillslope by decreasing vertical solute spreading. Copyright © 2002 John Wiley & Sons, Ltd.
Applied Geochemistry, 2006
Metal pollution in soils is a world-wide problem requiring new tools for environmental management... more Metal pollution in soils is a world-wide problem requiring new tools for environmental management. This study investigated the transport processes of metals (Cd, Cu and Pb) in undisturbed soil columns of an acid soil amended with phosphogypsum, sugar foam, and phosphoric rock (PG, SF and PR). Sorption mechanisms have been examined in a companion paper using sequential extraction methods. This investigation focused on how these sorption mechanisms relate to transport parameters estimated from metal breakthrough curves using temporal moment analysis. The application of the 3 soil amendments significantly reduced the total metal mass leached from all the columns. Metal travel times were also longer with the addition of the amendments, although retardation values were much lower than those reported in batch studies. Retardation (R) values for Cd, Cu and Pb averaged 1.6, 1.8 and 1.7, respectively, for all treated columns. These R values for the control columns were 1.2, 1.3 and 1.4 for Cd, Cu and Pb, respectively. Additional observations of Al, Ca and SO 2À 4 leaching from the columns revealed the existence of fast exchange and precipitation-dissolution reactions included in the transport of metals through the soil. Under the conditions of this study, it is estimated that the mass of Cd, Cu and Pb leached from the soil would be reduced by more than 60-99% with the addition of the amendments. Therefore, all 3 amendments (PG, SF, and PR) appear to have reasonable potential to be applied to reduce metal leaching in polluted agricultural soils.
Journal of Environmental Quality, 2000
A fibre optic mini probe (FOMP) system has been recently developed, capable of measuring solute b... more A fibre optic mini probe (FOMP) system has been recently developed, capable of measuring solute breakthrough curves (BTCs) in situ and in real time at a single point within the soil matrix. We have multiplexed this system to allow continuous operation of up to 20 of these ...
Applied Geochemistry, 2005
In situ stabilization of metals in contaminated soils by addition of industrial by-products is an... more In situ stabilization of metals in contaminated soils by addition of industrial by-products is an attractive remediation technique. In this work, mixtures of metal-spiked (Cd, Cu and Pb) samples from the Ap horizons of two acid soils and solid samples of 4 industrial by-products (red gypsum, phosphogypsum, sugar foam and dolomitic residue) were incubated in order to assess the efficiency of the by-products for the in situ remediation of contaminated soils. Single (DTPA extraction and TCLP test) and sequential chemical extraction procedures were used to examine the availability and potential mobility of the metals retained as a result of the treatments. Both the sugar foam and dolomitic residue reduced the availability and mobility of Cd, Cu and to a lesser extent, Pb. On the other hand, red gypsum and phosphogypsum proved effective in immobilizing Pb and, to a lesser extent, Cu. However, both gypsum-like by-products were not so effective in reducing Cd availability and mobility.
Soil Science, 2004
It has been suggested that the leaf litter layer influences soil infiltration processes in hillsl... more It has been suggested that the leaf litter layer influences soil infiltration processes in hillslopes. This paper examines the effect of the presence of the leaf litter layer in an oak woodland on conservative tracer transport measured in situ using time domain reflectometry (TDR) probes. This was done using repeated tracer miscible displacement studies, first with the litter layer intact and then again after removal of the litter layer. Tracer transport, as measured breakthrough curves (BTCs), was characterized using temporal moment analyses. These plot scale studies, performed at a field location in northern California, did not identify consistent changes in tracer transport patterns in the vertical transport plots before and after litter layer removal. In contrast, downslope lateral tracer displacement in the upper 20 cm of the soil did change after litter removal. However, no differences were evident deeper in the soil (30-50 cm) in temporal moments before and after litter removal during lateral tracer transport. This result demonstrates that the litter layer had a localized (near soil surface) influence on lateral transport. This influence may be explained by vertical anisotropy in effective soil hydraulic conductivity on the direction of lateral flow relative to the soil surface in the hillslope plots. It was demonstrated that the litter presence promotes a more vertical direction for the lateral flow in the first 20 cm of the soil. Despite the small changes in the first 20 cm observed in tracer transport after litter removal, the physical presence of the leaf litter layer was not found to be a major influence on tracer transport at the 30-to 50-cm depth in this hillslope soil where most of the lateral flow occurs. (Soil Science 2004;Volume 169:100-114)
Geochimica Et Cosmochimica Acta, 2009
The bioavailability and fate of heavy metals in the environment are often controlled by sorption ... more The bioavailability and fate of heavy metals in the environment are often controlled by sorption reactions on the reactive surfaces of soil minerals. We have developed a non-electrostatic equilibrium model (NEM) with both surface complexation and ion exchange reactions to describe the sorption of Pb and Cd in single-and binary-metal systems over a range of pH and metal concentration. Mineralogical and exchange properties of three different acidic soils were used to constrain surface reactions in the model and to estimate surface densities for sorption sites, rather than treating them as adjustable parameters. Soil heterogeneity was modeled with >FeOH and >SOH functional groups, representing Fe-and Al-oxyhydroxide minerals and phyllosilicate clay mineral edge sites, and two ion exchange sites (X À and Y À ), representing clay mineral exchange. An optimization process was carried out using the entire experimental sorption data set to determine the binding constants for Pb and Cd surface complexation and ion exchange reactions.
Soil Science Society of America Journal, 1999
Many water flow and solute transport studies require accurate measurement of water content within... more Many water flow and solute transport studies require accurate measurement of water content within small soil volumes. We have examined the feasibility of using fiber optic mini-probes (FOMPs) for in situ measurement of water content in relatively small soil volumes (<15-20 ...
Journal of Environmental Quality, 2001
data at high resolution, which may be used to validate solute transport models such as two-phase ... more data at high resolution, which may be used to validate solute transport models such as two-phase models, the There is a necessity for improved physical understanding of solute convection dispersion equation (CDE), or the stochastic transport processes in heterogeneous soil systems. In situ nondestructive techniques like time domain reflectometry (TDR) and fiber optic convective lognormal transfer function (CLT) (Jury and miniprobes (FOMPs) permit the collection of unique measurements Sposito, 1985). For example, TDR has become an acof solute transport processes in soils for the purposes of model develcepted method for estimating in situ transport parameters opment and validation. This study examined the application of TDR for models like the CDE
European Journal of Soil Science, 2004
In situ stabilization of heavy metals in contaminated soils by the addition of various types of s... more In situ stabilization of heavy metals in contaminated soils by the addition of various types of soil amendment is an attractive technique for remediation. We investigated the potential of three industrial by-products (phosphogypsum, red gypsum and dolomitic residue) for boosting the heavy metal sorption capacity of an acid soil (patents pending, Spanish applications no 200201704 and 200201375) by using sorption isotherm experiments. The three by-products were found substantially to increase the retention of lead, cadmium and copper on the solid components of the soil. The increase in lead retention of the soil horizons upon the addition of both phosphogypsum and red gypsum was dominated by the formation of anglesite minerals. The dolomitic residue increased the metal retention capacity of the soil horizons through the precipitation of laurionite-type minerals as well as cadmium and copper hydroxy-chlorides. In addition to the batch sorption study, we used scanning electron microscopy to investigate the metal sorption processes in the soil by the effect of the treatments. Lead was frequently found to be linked to the edge charges of kaolinite minerals. The three metals were found to be associated with organic matter in the Ap horizon treated with the three by-products. Finally, the three metals were found to be associated with undissolved dolomitic residue particles.
Geoderma, 2004
The bioavailability and ultimate fate of heavy metals in the environment are controlled by chemic... more 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. D
Geoderma, 2009
A series of incubation and leaching experiments were performed to assess the feasibility of two i... more A series of incubation and leaching experiments were performed to assess the feasibility of two industrial byproducts (phosphogypsum -PGand sugar foam -SF-, rich in gypsum and calcium carbonate, respectively) to reduce the potential leachability of As, Cd, and Tl in an acidic soil. The effectiveness of the treatments (SF and PG + SF) was evaluated in response to the addition of a chelating agent (DTPA solution) or weak acidification (acetic acid at pH 4.93, TCLP solution) and the resulting sorption mechanisms as a function of treatment was estimated through the application of a sequential extraction procedure. Both amendments induced a significant increment in the soil retention capacity of the three elements. The subsequent leaching tests indicated that those columns treated with SF and PG + SF significantly reduced the amount of element leached regardless the experiments were performed with DTPA or an acidifying solution. The results of the sequential extraction procedure revealed that amending contaminated soils with both SF and PG + SF results in a redistribution of the three toxic elements from soluble and exchangeable pools (FI) to the Al, Fe and Mn (hydr)oxide (FII) fraction Overall, the addition of these amendments to an acid soil contaminated with As, Cd, and Tl reduced their mobility and potential leachability.
European Journal of Soil Science, 2003
Lime, mined gypsum and some gypsum-like by-products have been frequently applied to soil to count... more Lime, mined gypsum and some gypsum-like by-products have been frequently applied to soil to counter acidity. We have examined the changes in the chemical and mineralogical properties of three acid soils resulting from the application of three industrial by-products (phosphogypsum, red gypsum and sugar foam). We did so in laboratory experiments on suspensions of soil in saturated solutions of the by-products. A sizeable fraction of the Al released by exchange with Ca of the amendments remained on the mineral surfaces as Al polymers, as suggested by changes in the CuCl2-, oxalic–oxalate- and DTPA-extractable Al contents. Polymerization of Al was promoted by corresponding neutral and basic pH of red gypsum and sugar foam saturated solutions, respectively. Sorption of these Al polymers was particularly favourable in those horizons with more clay fraction and variable-charge clay minerals. On the other hand, in most cases there was little or no detectable sorption of sulphate, thus excluding precipitation of crystalline or amorphous basic Al sulphates to alleviate Al toxicity. Based on the reduction of the Al saturation of the exchange complex in the soils, as well as on the small contents of heavy metals and natural radionuclides of the three by-products, these can be considered effective alternatives to mined gypsum and lime for alleviating soil acidity and reducing toxic concentrations of Al in agricultural, acid soils.
Applied Geochemistry, 2007
To asses the efficiency of two by-products (phosphogypsum (PG) and sugar foam (SF), rich in gypsu... more To asses the efficiency of two by-products (phosphogypsum (PG) and sugar foam (SF), rich in gypsum and calcium carbonate, respectively) in the immobilization of three toxic elements (As, Cd and Tl) in an acidic soil, batch-scale sorption and desorption experiments were conducted after 18 months of in situ amendment application. The Langmuir isotherms applied for sorption studies showed that the estimated maximum sorption capacity of the elements was highest in the SFtreated samples. The amount of element retained and the percentage of extraction after TCLP tests indicated that those samples amended with sugar foam (SF and PG + SF) had the potential to immobilize As, Cd and Tl in an acidic soil with low sorptive capacity. In addition to sorption and desorption experiments, scanning electron microscopy in back-scattered electron mode (SEM-BSE) showed the formation of Al-hydroxy polymers which provides the soil with additional sorption capacity. The three target elements were associated with the Al-hydroxy polymers, probably through direct coordination or the formation of ternary complexes. By means of statistical analysis it has been found that sorption processes of As, Cd and Tl in this soil mainly depend on the treatment, whereas desorption is an element-dependent process.
European Journal of Soil Science, 2006
When acid soil has been contaminated by metals as a result of industrial discharges, accidental s... more When acid soil has been contaminated by metals as a result of industrial discharges, accidental spills, or acid mine drainage it may be desirable to retain the metals in the soil rather than allow them to leach away. We have investigated the potential of phosphogypsum (PG), sugar foam (SF), and phosphoric rock (PR) to regulate the availability and mobility of Pb, Cd and Cu. We have also identified changes in attenuation during incubation for 1 year and the effect of aging on metal speciation in amended soils. We studied miscible displacement in columns of undisturbed soil previously treated with solutions of the amendments and soluble metals and, subsequently, single and sequential chemical metal extractions. All amendments increased the soil's metal retention capacity. This, in turn, increased the amount of metal extractable by diethylenetriaminepentaacetic acid (DTPA). However, over time the amounts of DTPA-extractable metal decreased, particularly for Cu and Pb. Both Cu and Cd were held preferentially within the acetic acid-extractable fraction (operationally defined exchangeable fraction – EX fraction), whereas Pb was associated mainly with the hydroxylammonium-extractable fraction (operationally defined bound to Fe and Al hydroxides – OX fraction). Both Pb and Cu in the oxide and organic fractions increased in the PG- and SF-treated soils. In general, the distribution of metal did not change in the PR-treated columns after the incubation. Finally, scanning electron microscopy in back-scattered electron mode (SEM–BSE) showed the formation of Al-hydroxy polymers which provides the soils with additional cation sorption capacity. In the PG- and PR-treated columns, P and S were associated with these formations. The three metals were associated with the Al polymers, probably through direct coordination or the formation of ternary complexes with the inorganic ligands phosphate and sulphate.
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Papers by Fernando Garrido