ORCID Profile
0000-0002-4875-2944
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University of Adelaide Waite Campus
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Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.ACA.2010.04.047
Abstract: Complexes between dissolved organic matter (DOM) and copper (Cu) that dissociate very slowly can theoretically facilitate Cu leaching to the groundwater. Data on dissociation kinetics of Cu-DOM complexes present in soil and in soil amendments are limited. The dissociation kinetics of different Cu-DOM complexes from soil, wastewater, pig manure and sewage sludge was measured with the Competitive Ligand Exchange Method (CLEM) and Diffusive Gradient in Thin films (DGT) technique. The solutions were set at constant pH, Ca concentration and free Cu(2+) activity to allow comparison between the different s les. The average dissociation rate constant k(d) of the complexes, as measured by CLEM, was about 10(-3) s(-1) and the fractions of dissolved Cu that were undissociated after 8 h ranged from <1% to 25%. These fractions determined by CLEM were significantly correlated with the non-labile fractions (0-82%) determined in the DGT tests and data analysis show that DGT data can be predicted from CLEM data. The dissociation rates decreased when Cu-DOM complexes had been equilibrated at lower Cu(2+) activities. Increasing the Cu-DOM contact time (7-297 days) decreased the dissociation rate. The non-labile fractions were positively correlated with the specific UV absorbance suggesting that aromatic moieties in DOM hold non-labile Cu. All natural Cu-DOM complexes contained a detectable fraction with a dissociation rate constant k(d) lower than 10(-5)s(-1) which can theoretically lead to non-equilibrium conditions and leaching risks in soil.
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/EN06057
Abstract: Environmental Context. Toxic effects of trace metals are often related to the amount of metal that is internalized by the organism. Uptake of metals by biota is usually predicted with equilibrium models, which assume that transport of the metal from the solution to the biosurface does not limit uptake. In this study, uptake of cadmium by higher plants is shown to be limited by the transport of the free ions to the root surface under a range of conditions. Abstract. Uptake of cadmium (Cd) by spinach and wheat was higher in the presence of fast-dissociating complexes than in unbuffered solutions with the same free ion concentration. This contribution of metal complexes to metal uptake cannot be explained by equilibrium free-ion-based models, which assume that transport of the free ion to the biosurface is not limiting the uptake. To demonstrate diffusion limitations to metal uptake, we used an agar gel technique in which Cd and Zn concentrations around the roots, after 6 h of uptake, were compared with bulk concentrations. Metal depletion around the roots was clearly observed in agar where the ion activities were not buffered by complexes, whereas the depletion was less pronounced in buffered agar. Metal uptake by the plants in unbuffered media was greater as the degree of agitation increased (stirred solution unstirred solution agar), while no such dependence on hydrodynamic conditions was found in buffered media, which is in agreement with theoretical predictions.
Publisher: Springer Science and Business Media LLC
Date: 02-11-2008
Publisher: Wiley
Date: 21-02-2003
Publisher: American Chemical Society (ACS)
Date: 09-2007
DOI: 10.1021/ES0726106
Publisher: Springer Science and Business Media LLC
Date: 29-09-2023
Publisher: Wiley
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 15-09-2015
Publisher: Wiley
Date: 23-06-2004
Publisher: Wiley
Date: 19-11-2008
Publisher: Wiley
Date: 03-2012
Publisher: Wiley
Date: 19-11-2008
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/EN09010
Abstract: Environmental context. Total concentrations of mineral elements in soil bear little relation to their availability for plants. The DGT (diffusive gradients in thin-films) technique has been found to be a good predictor of trace metal uptake and P deficiency, though not consistently in all studies for all elements. This review examines the fundamental basis for the relation between DGT fluxes and plant uptake and assesses under which conditions this relation may break down. Abstract. In the DGT technique, elements are accumulated on a binding gel after their diffusive transport through a hydrogel. In this paper, we explore in more detail why – and under which conditions – DGT correlates with plant uptake. The theoretical considerations are illustrated with experimental results for metal uptake and toxicity, and for phosphorus deficiency. Strong correlations between DGT and plant uptake are predicted if the diffusive transport of the element from soil to the plant roots is rate-limiting for its uptake. If uptake is not limited by diffusive transport, DGT-fluxes and plant uptake may still correlate provided that plant uptake is not saturated. However, competitive cations may affect the plant uptake under these conditions, whereas they have no effect on the DGT flux. Moreover, labile complexes are not expected to contribute to the plant uptake if diffusion is not limiting, but they are measured with DGT. Therefore, if plant uptake is not limited by diffusion, interpretation of the observed correlation in terms of the labile species measured by DGT is inappropriate.
Publisher: Wiley
Date: 18-04-2013
DOI: 10.1111/NPH.12276
Abstract: The fractionation of stable copper ( C u) isotopes during uptake into plant roots and translocation to shoots can provide information on C u acquisition mechanisms. Isotope fractionation ( 65 C u/ 63 C u) and intact tissue speciation techniques ( X ‐ray absorption spectroscopy, XAS ) were used to examine the uptake, translocation and speciation of C u in strategy I (tomato– S olanum lycopersicum ) and strategy II (oat – A vena sativa ) plant species. Plants were grown in controlled solution cultures, under varied iron ( F e) conditions, to test whether the stimulation of F e‐acquiring mechanisms can affect C u uptake in plants. Isotopically light C u was preferentially incorporated into tomatoes (Δ 65 C u whole plant‐solution = c. − 1‰), whereas oats showed minimal isotopic fractionation, with no effect of F e supply in either species. The heavier isotope was preferentially translocated to shoots in tomato, whereas oat plants showed no significant fractionation during translocation. The majority of C u in the roots and leaves of both species existed as sulfur‐coordinated C u( I ) species resembling glutathione/cysteine‐rich proteins. The presence of isotopically light C u in tomatoes is attributed to a reductive uptake mechanism, and the isotopic shifts within various tissues are attributed to redox cycling during translocation. The lack of isotopic discrimination in oat plants suggests that C u uptake and translocation are not redox selective.
Publisher: Wiley
Date: 12-08-2013
Publisher: Wiley
Date: 05-2021
DOI: 10.1002/SAJ2.20238
Abstract: Elemental sulfur (ES) is commonly used as a fertilizer S source but needs to be oxidized to sulfate to become plant‐available. We assessed how placement (surface applied or incorporated) affects the oxidation of ES fertilizers. The fertilizers included an ES powder, a suspension of biogenic ES particles, and three granular fertilizers: two ES–bentonite pastilles and one monoammonium phosphate fertilizer cogranulated with ES. The fertilizers were applied either on the surface (broadcast) or incorporated into two different soils in a column experiment, incubated at 25 °C. Prior to broadcasting, the granular fertilizers were dispersed in water for 48 h to simulate the effect of 30 to 40 mm of precipitation. The columns were leached weekly and the concentration of sulfates derived through ES oxidation was measured in the leachates. The half‐lives of oxidation for the ES powder were 76 and 111 d for the incorporation and broadcast applications, respectively. The diluted biological ES suspension showed faster oxidation (8 and 30 d for incorporated and broadcast), probably because of its smaller particle size. Unlike the ES particles, the ES oxidation rates of the granular fertilizers were higher for the broadcast application than when incorporated in soil, particularly when they dispersed easily. One type of ES pastille showed little dispersion and its estimated half‐life of oxidation was ,000 d even when broadcast. Overall, the results show that ES oxidation depends on the degree of dispersion in the soil and that this is strongly affected by the fertilizer type and application method.
Publisher: Springer Science and Business Media LLC
Date: 19-10-2006
Publisher: American Chemical Society (ACS)
Date: 09-05-2008
DOI: 10.1021/ES703061T
Abstract: Antimony trioxide (Sb2O3) is a widely used chemical that can be emitted to soil. The fate and toxicity of this poorly soluble compound in soil is insufficiently known. A silt-loam soil (pH 7.0, background 0.005 mmol Sb kg(-1)) was amended with Sb2O3 at various concentrations. More than 70% of Sb in soil solution was present as Sb(V) (antimonate) within 2 days. The soil solution Sb concentrations gradually increased between 2 and 35 days after Sb2O3 amendment but were always below that of soils amended with the more soluble SbCl3 at the lower Sb concentrations. The soil solution Sb concentrations in freshly amended SbCl3 soils (7 days equilibration) were equivalent to those in Sb2O3-amended soils equilibrated for 5 years at equivalent total soil Sb. Our data indicate that the Sb solubility in this soil was controlled by a combination of sorption on the soil surface, Sb precipitation at the higher doses, and slow dissolution of Sb2O3, the latter being modeled with a half-life ranging between 50 and 250 days. Toxicity of Sb to plant growth (root elongation of barley, shoot biomass of lettuce) or to nitrification was found in soil equilibrated with Sb2O3 (up to 82 mmol Sb kg(-1)) for 31 weeks with 10% inhibition values at soil solution Sb concentrations of 110 microM Sb or above. These concentrations are equivalent to 4.2 mmol Sb per kg soil (510 mg Sb kg(-1)) at complete dissolution of Sb2O3 in this soil. No toxicity to plant growth or nitrification was evident in toxicity tests starting one week after soil amendment with Sb2O3, whereas clear toxicity was found in a similar test using SbCl3. However, these effects were confounded by a decrease in pH and an increase in salinity. It is concluded that the Sb(V) toxicity thresholds are over 100-fold larger than background concentrations in soil and that care must be taken to interpret toxicity data of soluble Sb(III) forms due to confounding factors.
Publisher: Springer Science and Business Media LLC
Date: 25-02-2015
Publisher: American Chemical Society (ACS)
Date: 10-06-2015
Publisher: Wiley
Date: 07-2016
Publisher: American Chemical Society (ACS)
Date: 21-12-2005
DOI: 10.1021/ES050894T
Abstract: Dissolved trace metals are present in the environment as free ions and as complexes. Commonly used models to predict metal bioavailability consider the free ion as the major bioavailable species. However, increases in metal availability in the presence of metal complexes have repeatedly been found. We measured the uptake of cadmium (Cd) by spinach (Spinacia oleracea) from solution in absence or presence of synthetic ligands. At the same free ion concentration, the uptake of Cd ranged over almost 3 orders of magnitude and was largest in treatments with fast dissociating (i.e. labile) complexes. Similar results were found for the diffusional fluxes in these solutions, as measured with the DGT technique. The observed effect of Cd complexes on the plant uptake was in agreement with model calculations in which plant uptake was assumed to be governed by the diffusional flux. These results strongly suggest that Cd uptake is rate-limited by diffusion of the free ion to the root surface, even in stirred solutions. As a result, dissolved Cd complexes can increase Cd uptake, resulting in apparent exceptions from the free ion activity model. The magnitude of this increase depends both on the concentration and on the lability of the complexes. The free ion concept should therefore be reconsidered when transport limitations of the metal ion to the uptake site prevail.
Publisher: Oxford University Press (OUP)
Date: 04-04-2018
DOI: 10.1105/TPC.17.00864
Publisher: Wiley
Date: 18-10-2013
Publisher: Wiley
Date: 10-09-2003
Publisher: Wiley
Date: 14-11-2015
Publisher: Springer Science and Business Media LLC
Date: 15-11-2008
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.JCIS.2022.07.149
Abstract: Layered double hydroxide (LDH) loaded with orthophosphate (PO Adsorption capacities were compared between PO The P adsorption capacities were 1.25-1.60 fold larger for P
Publisher: Wiley
Date: 30-08-2016
Publisher: Elsevier BV
Date: 05-2018
Publisher: Wiley
Date: 17-12-2010
Publisher: Wiley
Date: 2015
Publisher: Elsevier BV
Date: 06-2012
DOI: 10.1016/J.SCITOTENV.2012.03.044
Abstract: The Free Ion Activity Model (FIAM) predicts that metal uptake in biota is related to the free ion activity in the external solution and that metal complexes do not contribute. However, studies with plants have shown that labile metal complexes enhance metal bioavailability when the uptake is rate-limited by transport of the free ion in solution to the uptake site. Here, the role of labile complexes of Cd on metal bioavailability was assessed using Caco-2 cells, the cell model for intestinal absorption. At low Cd(2+) concentration (1 nM), the CdCl(n)(2-n) complexes contributed to the uptake almost to the same extent as the free ion. At large Cd(2+) concentration (10 μM), the contribution of the complexes was much smaller. At constant Cd(2+) concentration, Cd intake in the cells from solutions containing synthetic ligands such as EDTA increased as the dissociation rate of the cadmium complexes increased, and correlated well with the Cd diffusion flux in solution measured with the Diffusive Gradient in Thin Films technique (DGT). The Cd intake fluxes in the cells were well predicted assuming that the specific uptake is limited by diffusion of the free Cd(2+) ion to the cell surface. Our results underline that speciation of Cd has a major effect on its uptake by intestinal cells, but the availability is not simply related to the free ion concentration. Labile complexes of Cd enhance metal bioavailability in these cells, likely by alleviating diffusive limitations.
Publisher: Wiley
Date: 21-10-2010
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.ENVPOL.2010.11.009
Abstract: Long-term applications of small concentrations of surfactants in soil via wastewater irrigation or pesticide application may enhance trace metal solubility. Mechanisms by which anionic surfactants (Aerosol 22, SDS and Biopower) affect trace metal solubility were assessed using batch, incubation and column experiments. In batch experiments on seven soils, the concentrations of Cu, Cd, Ni and Zn in the dissolved fraction of soils increased up to 100-fold at the high application rates, but increased less than 1.5-fold below the critical micelle concentration. Dissolved metal concentrations were less than 20% affected by surfactants in long-term incubations (70 days) up to the largest dose of 200 mg C kg(-1) soil. Leaching soil columns with A22 (100-1000 mg C L(-1)) under unsaturated conditions increased trace metal concentrations in the leachates 2-4 fold over the control. Correlation analysis and speciation modelling showed that the increased solubility of metals upon surfactant application was more related to the solubilisation of soil organic matter from soil than to complexation of the metals with the surfactant. Organic matter from soil was solubilised in response to a decrease of solution Ca(2+) as a result of Ca-surfactant precipitation. At environmentally relevant concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility.
Publisher: American Chemical Society (ACS)
Date: 02-06-2011
DOI: 10.1021/AC200748E
Abstract: The speciation of P in environmental s les is operationally defined, since it depends on the analytical method used. In this study, we compared four methods to measure P in solution: ion chromatography (IC), the malachite green colorimetric method (CM), the diffusive gradient in thin films technique (DGT) and, for total dissolved P, optical inductively coupled plasma (ICP). These methods were compared on three sets of solutions (filtered over <0.45 μm): solutions with model organic P compounds, suspensions of synthesized inorganic Fe and Al colloids loaded with P, and environmental s les. The environmentally relevant organic P compounds were only marginally detected by CM and IC. Substantial fractions of certain organic P compounds contributed to the DGT measurement. Colorimetric analysis of DGT eluates detected in general less P than ICP analysis, indicating that these organic P compounds sorbed on the zero sink layer. Phosphorus associated with inorganic colloids was completely recovered by CM, but not by IC and least by DGT. Measurements on a wide set of 271 environmental s les (soil pore waters, groundwaters, and surface waters) suggest that surface water P is largely present as orthophosphate and phosphate sorbed onto inorganic colloids, whereas organic P contributes more in groundwaters.
Publisher: Elsevier BV
Date: 07-2010
Publisher: Wiley
Date: 29-05-2021
DOI: 10.1002/JEQ2.20236
Abstract: Losses of phosphorus (P) from fertilized fields may result in degradation of water quality. Various initiatives are under evaluation to minimize water contamination, including the adoption of less soluble or coated P fertilizer formulations aiming to mitigate losses of P in runoff. Field‐based rainfall simulators are traditionally used to evaluate P runoff, but using these is time consuming, labor intensive, and costly given the complex apparatus and analyses involved. We hypothesized that laboratory‐based methods could be useful to evaluate the risk of P runoff from fertilizers. In order to identify a rapid, inexpensive, and efficient screening process, we compared two laboratory‐scale measurements, one in water (based on electrical conductivity measurements) and one in soil (based on visualization of P diffusion in soil), with runoff results from field‐, glasshouse‐, and laboratory‐based rainfall simulators, using coated soluble phosphate fertilizers. The laboratory‐based methods assessing the P release rate in water and in soil correlated closely ( r ≥ .96) with the losses of P obtained in the three rainfall simulators regardless of the type of coating or solubility of the fertilizer. The faster and inexpensive electrical conductivity and diffusion visualization methodologies were useful to rank the fertilizers by P release to runoff. Hence, these tools may be useful for screening fertilizer formulations with respect to their runoff risk.
Publisher: American Chemical Society (ACS)
Date: 11-07-2014
DOI: 10.1021/ES500764X
Abstract: As copper (Cu) stable isotopes emerge as a tool for tracing Cu biogeochemical cycling, an understanding of how Cu isotopes fractionate during complexation with soluble organic ligands in natural waters and soil solutions is required. A Donnan dialysis technique was employed to assess the isotopic fractionation of Cu during complexation with the soluble synthetic ligands ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA) and desferrioxamine B (DFOB), as well as with Suwannee River fulvic acid (SRFA). The results indicated enrichment of the heavy isotope ((65)Cu) in the complexes, with Δ(65)Cu complex-free values ranging from +0.14 to +0.84‰. A strong linear correlation was found between the logarithms of the stability constants of the Cu complexes and the magnitudes of isotopic fractionation. These results show that complexation of Cu by organic ligands can affect the isotopic signature of the free Cu ion. This free Cu is considered the most bioavailable species, and hence, our results highlight the importance of understanding fractionation processes in the uptake medium when using Cu isotopes to study the uptake mechanisms of organisms. These data contribute a vital piece to the emerging picture of Cu isotope cycling in the natural environment, as organic complexation plays a key role in the Cu cycle.
Publisher: Wiley
Date: 03-2006
DOI: 10.1897/05-026R.1
Abstract: Laboratory experiments have been performed with 3-cm soil columns simulating the fate of corrosion-induced copper runoff in contact with soil. The investigation simulates approximately 30 years (assuming an infiltration surplus of 25 cm/year) of continuous percolation of copper containing runoff water of a concentration realistic at the immediate release situation (4.8 mg/L) into four soils representative of urban conditions. Two of the three investigated topsoils reached their breakthrough of copper within the simulated time, while the third topsoil did not show a breakthrough. The subsoil reached a breakthrough after approximately 10 years of simulated exposure. To simulate more realistic outdoor scenarios, the laboratory-obtained breakthrough curves were modeled with Hydrus-1D using a Langmuir-Freundlich model to describe copper sorption, the parameters of which were estimated from soil properties (pH, organic carbon content). The model predicts longer breakthrough times with increasing pH and organic content of the soil and with decreasing concentrations of copper and dissolved organic carbon in the runoff water. The time span for copper in runoff water (at concentrations of 0.01-10 mg/L) to reach a soil depth of 50 cm varied between 170 and more than 8,000 years for the predicted field scenarios.
Publisher: MDPI AG
Date: 17-07-2020
Abstract: Field trials with labeled fertilizers can be used to provide information on fertilizer efficiency, residual value, and nutrient fate. We assessed the uptake from elemental S (ES) and sulfate S (SO4-S) in S-fortified monoammonium phosphate fertilizers by various crops at three sites in Argentina, Brazil, and Canada. The S sources were labeled with 34S, and the 34S abundance in the plant tissue was analyzed at an early stage and at maturity over two consecutive years. At the sites in Argentina and Canada, the recovery of ES in the crop was smaller than that of SO4-S in the first year, while the opposite was true in the second year. At the Brazilian site, the recovery of ES was similar to that of SO4-S in the first year, but higher in the second year. In the Argentina and Canada sites, the cumulative recovery of SO4-S was % and that of ES was 20−25%. In the Brazilian site, the cumulative recovery of SO4-S was 9% and that of ES 16%. The higher recovery of ES than of SO4-S in the Brazilian site was attributed to leaching of added SO4-S and relatively fast oxidation of ES due to the warm climate. These results suggest that ES may be more suitable than SO4-S as a fertilizer S source in warm humid climates, while inclusion of SO4-S in the fertilizer is recommended in colder climates as slow oxidation limits the initial availability of ES.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2012
Publisher: Wiley
Date: 03-2016
Publisher: American Chemical Society (ACS)
Date: 15-11-2021
Publisher: Wiley
Date: 20-02-2015
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/SR14128
Abstract: The application of pure boron (B) fertilisers, independent of other macronutrients, is impractical due to the increased cost of dual handling and spreading. Bulk blending of B with other micronutrients is also an unattractive option as the relatively low rates of B required results in poor nutrient distribution in the field. Co-granulating B with other macronutrients such as mono-ammonium phosphate (MAP) may overcome these problems. Five B sources (boron phosphate (BPO4) synthesised at 500 and 800°C for 1 h, colemanite, ulexite and borax) were co-granulated with MAP to targeted B contents of 0.5, 1.0 and 2.0%. The co-granulated BPO4 had lower water solubility than co-granulated colemanite, ulexite and borax. Boron released from co-granulated borax, ulexite and colemanite was remarkably greater than co-granulated BPO4 products. Over a 4-week soil incubation period with weekly leaching of one pore volume of water, the cumulative B release from co-granulated ulexite, borax and colemanite was 97, 75 and 58%, respectively, but only 16 and 4% for the co-granulated BPO4 synthesised at 500 and 800°C, respectively. Co-granulated BPO4 products have potential as a high quality fertiliser to increase crop yield with slow B release.
Publisher: Wiley
Date: 13-07-2009
Publisher: Oxford University Press (OUP)
Date: 03-08-2012
Abstract: It has long been recognized that diffusive boundary layers affect the determination of active transport parameters, but this has been largely overlooked in plant physiological research. We studied the short-term uptake of cadmium (Cd), zinc (Zn), and nickel (Ni) by spinach (Spinacia oleracea) and tomato (Lycopersicon esculentum) in solutions with or without metal complexes. At same free ion concentration, the presence of complexes, which enhance the diffusion flux, increased the uptake of Cd and Zn, whereas Ni uptake was unaffected. Competition effects of protons on Cd and Zn uptake were observed only at a very large degree of buffering, while competition of magnesium ions on Ni uptake was observed even in unbuffered solutions. These results strongly suggest that uptake of Cd and Zn is limited by diffusion of the free ion to the roots, except at very high degree of solution buffering, whereas Ni uptake is generally internalization limited. All results could be well described by a model that combined a diffusion equation with a competitive Michaelis-Menten equation. Direct uptake of the complex was estimated to be a major contribution only at millimolar concentrations of the complex or at very large ratios of complex to free ion concentration. The true K m for uptake of Cd 2+ and Zn 2+ was estimated at & nm, three orders of magnitude smaller than the K m measured in unbuffered solutions. Published Michaelis constants for plant uptake of Cd and Zn likely strongly overestimate physiological ones and should not be interpreted as an indicator of transporter affinity.
Publisher: Springer Science and Business Media LLC
Date: 16-10-2023
Publisher: American Chemical Society (ACS)
Date: 08-03-2007
DOI: 10.1021/ES062166R
Abstract: Copper is mobilized in soil by dissolved organic matter (DOM) but the role of DOM quality in this process is unclear. A one-step resin-exchange method was developed to measure the Cu-Mobilizing-Potential (CuMP) of DOM at pCu 11.3 and pH 7.0, representing background values. The CuMP of DOM was measured in soil solutions of 13 uncontaminated soils with different DOM extraction methods. The CuMP, expressed per unit dissolved organic carbon (DOC), varied 10-fold and followed the order water extracts > 0.01 M CaCl2 extracts > pore water. Soil solutions, obtained from soils that were stored air-dry for a long time or were subjected to drying-wetting cycles, had elevated DOC concentration, but the DOM had a low CuMP. Prolonged soil incubations decreased the DOC concentration and increased the CuMP, suggesting that most of the initially elevated DOM is less humified and has lower Cu affinity than DOM remaining after incubation. A significant positive correlation between the specific UV-absorption of DOM (indicating aromaticity) and CuMP was found for all DOM s les (R(2) = 0.58). It is concluded that the DOC concentration in soil is an insufficient predictor for the Cu mobilization and that DOM s les isolated from air-dried soils are distinct from those of soils kept moist.
Publisher: Wiley
Date: 25-04-2012
DOI: 10.1111/J.1365-3040.2012.02509.X
Abstract: Diffusion towards the root surface has recently been shown to control the uptake of metal ions from solutions. The uptake flux of phosphorus (P) from solutions often approaches the maximal diffusion flux at low external concentrations, suggesting diffusion-controlled uptake also for P. Potential diffusion limitation in P uptake from nutrient solutions was investigated by measuring P uptake of Brassica napus from solutions using P-loaded Al(2) O(3) nanoparticles as mobile P buffer. At constant, low free phosphate concentration, plant P uptake increased up to eightfold and that of passive, diffusion-based s lers up to 40-fold. This study represents the first experimental evidence of diffusion-limited P uptake by plant roots from nutrient solution. The Michaelis constant of the free phosphate ion obtained in unbuffered solutions (K(m) = 10.4 µmol L(-1) ) was 20-fold larger than in the buffered system (K(m) ∼0.5 µmol L(-1) ), indicating that K(m) s determined in unbuffered solutions do not represent the transporter affinity. Increases in the P uptake efficiency of plants by increasing the carrier affinity are therefore unlikely, while increased root surface area or exudation of P-solubilizing compounds are more likely to enhance P uptake. Furthermore, our results highlight the important role natural nanoparticles may have in plant P nutrition.
Publisher: American Chemical Society (ACS)
Date: 08-03-2007
DOI: 10.1021/ES061995+
Abstract: The inhibitory effect of Zn on the nitrification process in ZnCl2 spiked soils (12 soils, pH range 4.8-7.5) was compared to toxic effects of Zn on the nitrification by Nitrosospira sp. in soilless solutions with varying pH (pH 6-8) and ionic composition. The nitrification was reduced by 20% at Zn solution concentrations (EC20) ranging between 7 and 1200 microM Zn in the soil pore water and between 5 and 150 microM Zn in the soilless solutions. Protective effects of H+, Ca2+, and Mg2+ against Zn2+ toxicity were observed in both systems. Zinc speciation was determined, and 60-90% of the Zn in the soils and 35-80% of the Zn in the soilless solutions was present as Zn2+. A biotic ligand model and a Freundlich-type model, incorporating the competition of Zn2+ ions with H+, Ca2+, and Mg2+ for binding on the biotic ligands, were used to model the results. The Zn2+ activities resulting in 20% reduction of the nitrification were well predicted using the same parameters for both (soil and soilless) systems, indicating that microorganisms in soil are exposed to zinc through the free zinc ion in soil pore water.
Publisher: American Chemical Society (ACS)
Date: 15-03-2011
DOI: 10.1021/ES103532A
Abstract: Dissolved organic matter (DOM) in surface waters affects the fate and environmental effects of trace metals. We measured variability in the Cd, Cu, Ni, and Zn affinity of 23 DOM s les isolated by reverse osmosis from freshwaters in natural, agricultural, and urban areas. Affinities at uniform pH and ionic composition were assayed at low, environmentally relevant free Cd, Cu, Ni, and Zn activities. The C-normalized metal binding of DOM varied 4-fold (Cu) or about 10-fold (Cd, Ni, Zn) among s les. The dissolved organic carbon concentration ranged only 9-fold in the waters, illustrating that DOM quality is an equally important parameter for metal complexation as DOM quantity. The UV-absorbance of DOM explained metal affinity only for waters receiving few urban inputs, indicating that in those waters, aromatic humic substances are the dominant metal chelators. Larger metal affinities were found for DOM from waters with urban inputs. Aminopolycarboxylate ligands (mainly EDTA) were detected at concentrations up to 0.14 μM and partly explained the larger metal affinity. Nickel concentrations in these surface waters are strongly related to EDTA concentrations (R2=0.96) and this is underpinned by speciation calculations. It is concluded that metal complexation in waters with anthropogenic discharges is larger than that estimated with models that only take into account binding on humic substances.
Publisher: American Chemical Society (ACS)
Date: 07-08-2002
DOI: 10.1021/ES025567P
Abstract: Tire debris contains significant quantities of zinc (Zn), and there is concern about the diffuse Zn contamination of soils from tire wear. An experiment was set up to quantify the fate and effect of Zn from tire debris in soil. Two different soils were mixed with the 0.05) more Zn than control soils except for a 3-fold increase in one soil amended with cartire debris. The increase in Zn leaching due to tire debris was only 3% of the corresponding increase in the ZnSO4 treatment at the same total Zn in soil. Tire debris application increased the soil nitrification potential, whereas ZnSO4 application, at corresponding or smaller total Zn concentration, decreased nitrification potential. An increase in soil pH was observed in all soils treated with tire debris and explains the increased nitrification potential. About 10-40% of the Zn from tire debris was isotopically exchangeable in soil s led after 1 year weathering. It is concluded that a significant fraction of Zn is released from the rubber matrix within 1 year, but the parallel increase in soil pH limits the mobilization of Zn in soil.
Publisher: Springer Science and Business Media LLC
Date: 21-07-2016
Publisher: Elsevier
Date: 2016
Publisher: Wiley
Date: 05-2014
Publisher: American Chemical Society (ACS)
Date: 11-03-2020
Publisher: Wiley
Date: 31-01-2007
Publisher: American Chemical Society (ACS)
Date: 23-11-2021
Abstract: Molybdenum (Mo) is an essential plant micronutrient. Despite low plant Mo requirements, deficiencies are not uncommon and soluble Mo fertilizers are often applied. However, soluble Mo may result in poor Mo use efficiency due to strong sorption (acid weathered soils) or leaching (lighter-textured soils). Here, ZnAl layered double hydroxides (LDHs), loaded with molybdate (MoO
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/EN11060
Abstract: Environmental contextUptake of metal ions by plants is often predicted with equilibrium models, which assume that the rate limiting step is trans-membrane uptake of the metal in the roots rather than the transport of the metal ion towards the site of uptake. Evidence is given that uptake of cadmium by plants is under strong transport control at environmentally relevant concentrations, whereas nickel uptake borders between transport and plant control. This explains the lack of ion competition effects for Cd uptake, whereas both proton and Mg ions were found to compete with Ni uptake. AbstractEquilibrium models for metal uptake by biota assume that the uptake is rate limited by the internalisation of the metal across the cell membrane (plant control). However, evidence has been found that Cd uptake by plants is controlled by the diffusive transport of the free ion to the root at low Cd2+ activities. In this study, the uptake of Cd and Ni by tomato and spinach in nutrient solution was compared to assess whether Ni uptake is under plant or transport control. The diffusive gradient in thin films (DGT) technique was used to measure the maximal diffusive flux. In unbuffered solutions, the uptake flux of Ni was approximately three-fold smaller than that of Cd at free ion concentrations below 1 µM. Stirring the solution increased the uptake of Cd, but not that of Ni at low free ion concentration. The presence of DGT-labile complexes increased the uptake of Cd, but not that of Ni, except at high pH (pH 7). Increasing the solution pH increased Cd uptake only when solution Cd2+ activities were strongly buffered. Overall, the results indicated that the Cd uptake was strongly diffusion limited and that uptake is likely to be under transport control in natural environments. Uptake of nickel, on the other hand, appears to be at the border between plant and transport control. This finding has practical applications, e.g. competition effects at the root have little effect on Cd uptake and chelator-assisted phytoextraction is expected to have less effect for Ni than for Cd.
Publisher: Wiley
Date: 12-01-2004
Publisher: Springer Science and Business Media LLC
Date: 12-09-2015
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.ACA.2006.06.070
Abstract: The evaluation of the ecotoxicological risk of nickel (Ni) in surface water is h ered by a lack of speciation data. Six surface waters were s led and speciation of Ni(II) was measured by the Donnan membrane technique (DMT) combined with radiochemical determination of 63Ni. The free Ni2+ ion fraction in the dissolved ( two-fold), even when assuming that all dissolved organic matter (DOM) was present as fulvic acid (FA). The impact of several model parameters affecting the prediction of Ni speciation were evaluated, including the solubility product of Fe(OH)3, which affects the Fe competition for complexation by DOM. The best fit (R2=0.88) was obtained by increasing only the distribution term DeltaLK2, which modifies the binding strength of multi-dentate sites, to accommodate the observed dependence of free ion fraction on Ni concentration.
Publisher: Wiley
Date: 21-10-2014
Publisher: Springer Science and Business Media LLC
Date: 06-03-2013
Publisher: Wiley
Date: 11-04-2005
Publisher: Springer Science and Business Media LLC
Date: 09-04-2021
DOI: 10.1007/S10705-021-10137-6
Abstract: In previous studies, we assessed sulfur (S) uptake by crops from elemental S (ES) and sulfate-S (SO 4 -S) in S-fortified monoammonium phosphate fertilizers over two years. The recovery by the crop ranged from 16 to 28% for ES and from 9 to 86% for SO 4 -S. Here, we used a model which takes into account organic S cycling, SO 4 -S leaching and ES oxidation to explain the observed recoveries. Higher recoveries of ES than SO 4 -S in two of the four sites could be explained by partial leaching of SO 4 -S and relatively fast oxidation of ES, due to a warm climate and high S-oxidizing soils. The same model was used for longer-term (5-year) predictions, and a sensitivity analysis was carried out. The size of the labile soil S pool and total S uptake strongly affected the recovery of both SO 4 -S and ES. Predicted recoveries after 5 years were over threefold higher for a small than for a large labile organic S pool and for a high-uptake than for a low-uptake scenario. Leaching mainly affected SO 4 -S, with predicted recoveries halved under a high-leaching scenario. Slow oxidation resulted in recoveries in the first year being fourfold lower for ES than for SO 4 -S or even lower in case of a long lag-time. However, it is predicted that total recoveries of ES will eventually reach those of SO 4 -S or exceed them if there is SO 4 -S leaching. Our model demonstrates that long-term trials are needed to evaluate the true effectiveness of a slow-release fertilizer source such as ES.
Publisher: American Chemical Society (ACS)
Date: 08-2003
DOI: 10.1021/ES034075P
Abstract: The technique of diffusive gradients in thin films (DGT) has been suggested to s le an available fraction of metals in soil. The objectives of this study were to compare DGT measurements with commonly measured fractions of Zn in soil, viz, the soil solution concentration and the total Zn concentration. The DGT technique was used to measure fluxes and interfacial concentrations of Zn in three series of field-contaminated soils collected in transects toward galvanized electricity pylons and in 15 soils amended with ZnCl2 at six rates. The ratio of DGT-measured concentration to pore water concentration of Zn, R, varied between 0.02 and 1.52 (mean 0.29). This ratio decreased with decreasing distribution coefficient, Kd, of Zn in the soil, which is in agreement with the predictions of the DGT-induced fluxes in soils (DIFS) model. The R values predicted with the DIFS model were generally larger than the observed values in the ZnCl2-amended soils at the higher Zn rates. A modification of the DIFS model indicated that saturation of the resin gel was approached in these soils, despite the short deployment times used (2 h). The saturation of the resin with Zn did not occur in the control soils (no Zn salt added) or the field-contaminated soils. Pore water concentration of Zn in these soils was predicted from the DGT-measured concentration and the total Zn content. Predicted values and observations were generally in good agreement. The pore water concentration was more than 5 times underpredicted for the most acid soil (pH = 3) and for six other soils, for which the underprediction was attributed to the presence of colloidal Zn in the soil solution.
Publisher: American Chemical Society (ACS)
Date: 12-05-2023
Publisher: Wiley
Date: 31-01-2007
No related grants have been discovered for Fien Degryse.