ORCID Profile
0000-0003-3054-2444
Current Organisation
KU Leuven
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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: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.SCITOTENV.2015.12.107
Abstract: Biochar sequesters carbon (C) in soils because of its prolonged residence time, ranging from several years to millennia. In addition, biochar can promote indirect C-sequestration by increasing crop yield while, potentially, reducing C-mineralization. This laboratory study was set up to evaluate effects of biochar on C-mineralization with due attention to source appointment by using (13)C isotope signatures. An arable soil (S) (7.9 g organic C, OC kg(-1)) was amended (single dose of 10 g kg(-1) soil) with dried, grinded maize stover (leaves and stalks), either natural (R) or (13)C enriched (R*), and/or biochar (B/B*) prepared from the maize stover residues (450 °C). Accordingly, seven different combinations were set up (S, SR, SB, SR*, SB*, SRB*, SR*B) to trace the source of C in CO2 (180 days), dissolved organic-C (115 days) and OC in soil aggregate fractions (90 days). The application of biochar to soil reduced the mineralization of native soil organic C but the effect on maize stover-C mineralization was not consistent. Biochar application decreased the mineralization of the non-enriched maize stover after 90 days, this being consistent with a significant reduction of dissolved organic C concentration from 45 to 18 mg L(-1). However, no significant effect was observed for the enriched maize stover, presumably due to differences between the natural and enriched materials. The combined addition of biochar and enriched maize stover significantly increased (twofold) the presence of native soil organic C or maize derived C in the free microaggregate fraction relative to soil added only with stover. Although consistent effects among C sources and biochar materials remains elusive, our outcomes indicate that some biochar products can reduce mineralization and solubilization of other sources of C while promoting their physical protection in soil particles.
Publisher: American Chemical Society (ACS)
Date: 09-2007
DOI: 10.1021/ES0726106
Publisher: Wiley
Date: 23-06-2004
Publisher: Wiley
Date: 19-11-2008
Publisher: Wiley
Date: 19-11-2008
Publisher: American Chemical Society (ACS)
Date: 04-11-2016
Abstract: Iron oxyhydroxide nanoparticles (Fe-NPs) are natural vectors of phosphate (PO
Publisher: Elsevier BV
Date: 03-2005
Publisher: Wiley
Date: 03-2018
Abstract: The enrichment of P in surface waters has been linked to P runoff from agricultural fields amended with fertilizers. Novel slow-release mineral fertilizers, such as struvite and P-exchanged layered double hydroxides (LDHs), have received increasing attention for P recycling from waste streams, and these fertilizers may potentially reduce the risk of runoff losses. Here, a rainfall simulation experiment was performed to evaluate P runoff associated with the application of recycled slow-release fertilizers relative to that of a soluble fertilizer. Monoammonium phosphate (MAP), struvite, and LDH granular fertilizers were broadcasted at equal total P doses on soil packed in trays (5% slope) and covered with perennial ryegrass ( L.). Four rainfall simulation events of 30 min were performed at 1, 5, 15, and 30 d after the fertilizer application. Runoff water from the trays was collected, filtered, and analyzed for dissolved P. For the MAP treatment, P runoff losses were high in the first two rain events and leveled off in later rain events. In total, 42% of the applied P in the MAP treatment was lost due to runoff. In the slow-release fertilizer treatments, P runoff losses were limited to 1.9 (struvite) and 2.4% (LDH) of the applied doses and were more similar over the different rain events. The use of these novel P fertilizer forms could be beneficial in areas with a high risk of surface water eutrophication and a history of intensive fertilization.
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: Brill | Wageningen Academic
Date: 2007
Publisher: Elsevier BV
Date: 08-2013
DOI: 10.1016/J.CHEMOSPHERE.2013.03.013
Abstract: Although aging processes are important in risk assessment for metals in soils, the aging of Ni added to soils has not been studied in detail. In this study, after addition of water soluble Ni to soils, the changes over time in isotopic exchangeability, total concentrations and free Ni(2+) activity in soil pore water, were investigated in 16 European soils incubated outdoors for 18 months. The results showed that after Ni addition, concentrations of Ni in soil pore water and isotopic exchangeability of Ni in soils initially decreased rapidly. This phase was followed by further decreases in the parameters measured but these occurred at slower rates. Increasing soil pH increased the rate and extent of aging reactions. Semi-mechanistic models, based on Ni precipitation/nucleation on soil surfaces and micropore diffusion, were developed and calibrated. The initial fast processes, which were attributed to precipitation/nucleation, occurred over a short time (e.g. 1h), afterwards the slow processes were most likely controlled by micropore diffusion processes. The models were validated by comparing predicted and measured Ni aging in three additional, widely differing soils aged outdoors for periods up to 15 months in different conditions. These models could be used to scale ecotoxicological data generated in short-term studies to longer aging times.
Publisher: Springer Netherlands
Date: 16-11-2012
Publisher: Wiley
Date: 04-06-2016
DOI: 10.1111/PCE.12749
Abstract: Several studies have suggested that the majority of iron (Fe) and zinc (Zn) in wheat grains are associated with phytate, but a nuanced approach to unravel important tissue-level variation in element speciation within the grain is lacking. Here, we present spatially resolved Fe-speciation data obtained directly from different grain tissues using the newly developed synchrotron-based technique of X-ray absorption near-edge spectroscopy imaging, coupling this with high-definition μ-X-ray fluorescence microscopy to map the co-localization of essential elements. In the aleurone, phosphorus (P) is co-localized with Fe and Zn, and X-ray absorption near-edge structure imaging confirmed that Fe is chelated by phytate in this tissue layer. In the crease tissues, Zn is also positively related to P distribution, albeit less so than in the aleurone. Speciation analysis suggests that Fe is bound to nicotianamine rather than phytate in the nucellar projection, and that more complex Fe structures may also be present. In the embryo, high Zn concentrations are present in the root and shoot primordium, co-occurring with sulfur and presumably bound to thiol groups. Overall, Fe is mainly concentrated in the scutellum and co-localized with P. This high resolution imaging and speciation analysis reveals the complexity of the physiological processes responsible for element accumulation and bioaccessibility.
Publisher: Springer Netherlands
Date: 19-11-2012
Publisher: Springer Science and Business Media LLC
Date: 19-10-2006
Publisher: American Chemical Society (ACS)
Date: 25-05-2004
DOI: 10.1021/ES0352597
Abstract: Effective concentrations (CE) of Zn measured by the technique of DGT (diffusive gradients in thin films) were compared, along with total concentrations of Zn and the concentrations of Zn in soil solutions, to Zn concentrations in plants. Soils variously contaminated with Zn were collected in the vicinity of two galvanized electrical transmission towers (pylons) and two motorway crash barriers. Lepidium sativum was grown in each soil and in corresponding control soils amended with ZnCl2 to similar total Zn concentrations. CE, concentrations in soil solution, and total Zn were measured in all soils, and total Zn was measured in the plant shoots. The CE values, soil solution Zn, and shoot Zn concentrations were all larger in ZnCl2 amended soils than in field contaminated soils at corresponding total Zn. Correlations between the concentration of Zn in the plants and the measured soil parameter followed the order CE > soil solution > total Zn. The low scatter in the plot of log plant concentration versus log CE revealed a relationship with two distinct features. Plant Zn was between 100 and 300 mg/kg up to an effective Zn concentration of about 2 mg/L, above which plant Zn increased steadily with increasing CE. Use of a dynamic model to interpret the DGT measurement suggests that the intrinsic rate of release of Zn from solid phase to solution, expressed as a rate constant, is much higher for soils that receive fresh supplies of Zn. This finding provides a mechanistic basis for reconciling laboratory experiments, where metal is freshly amended, to data obtained in the field. The potential of DGT as a surrogate for metal availability to plants is further confirmed by this work.
Publisher: Wiley
Date: 03-2012
DOI: 10.2134/JEQ2011.0317
Abstract: Metals in soils amended with sewage sludge are typically less available compared with those in soils spiked with soluble metal salts. However, it is unclear if this difference remains in the long term. A survey of copper (Cu) availability was made in soils amended with sewage sludge, manure, and compost, collectively named organic amendments. Paired sets of amended and control soils were collected from 22 field trials where the organic amendments had aged up to 112 yr. Amended soils had higher total Cu concentrations (range, 2-220 mg Cu kg median, 15 mg Cu kg) and organic C (range, 1-16 g kg median, 4 g kg) than control soils. All s les were freshly spiked with CuCl, and the toxicity of added Cu to barley was compared between amended and control soils. The toxicity of added Cu was significantly lower in amended soils than in control soil in 15 sets by, on average, a factor of 1.4, suggesting that aged amendments do not largely increase Cu binding sites. The fraction of added Cu that is isotopic exchangeable Cu (labile Cu) was compared between control soils freshly spiked with CuCl and amended soils with both soils at identical total Cu concentrations. Copper derived from amendments was significantly less labile (on average 5.9-fold) than freshly added Cu in 18 sets of soils. This study shows that Cu availability after long-term applications of organic amendments is lower than that of freshly added Cu salts, mainly because of its lower availability in the original matrix and ageing reactions than because of increased metal binding sites in soil.
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: American Chemical Society (ACS)
Date: 20-01-2015
DOI: 10.1021/JF5055485
Abstract: The distribution of minerals in (pearled) wheat grains was measured by synchrotron X-ray fluorescence, and the impact of pearling (0, 3, 6, 9, and 12% by weight) on the mineral composition of flour, shorts, and bran was identified by ICP-MS. The xylem mobile elements (Mn, Si, Ca, and Sr) dominated in the outermost bran layers, while the phloem mobile elements (K, Mg, P, Fe, Zn, and Cu) were more concentrated in the aleurone. Pearling lowered the concentrations of xylem mobile elements and increased the concentrations of most phloem mobile elements in the pearled grains. Molybdenum, Cd, and especially Se were more evenly distributed, and pearling affected their concentrations in milling products less. Pearling (3%) increased the concentration of several nutrients (P, Zn, Cu) in the flour because the bran fractions reaching the flour are enriched in aleurone. The correlations of concentrations of Mg, Fe, Zn, and Cu with that of P suggested their association with phytate.
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: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.JCIS.2018.11.010
Abstract: Layered double hydroxides (LDH) have been proposed for phosphate (PO
Publisher: Wiley
Date: 10-09-2003
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/EN15086
Abstract: Environmental context In order to assess the potential risks of elevated molybdenum concentrations in soil due to anthropogenic activities, toxicity thresholds must be known and environmental criteria defined. Setting such criteria for metals is not straightforward because of varying natural background concentrations and differences in toxicity between typical laboratory and field conditions and across soil types. Toxicity data and models were derived that account for these parameters so that soil quality criteria can be derived based on total molybdenum concentrations in soil. Abstract An extensive testing programme on the toxicity of sodium molybdate dihydrate in soil was initiated to comply with the European REACH Regulation. The molybdate toxicity was assayed with 11 different bioassays, 10 different soils, soil chemical studies on aging reactions, and toxicity tests before and after 1-year equilibration in field conditions. Differences in molybdate toxicity among soils were best explained by soil pH and clay content. A correction factor of 2.0 was selected to account for the difference in molybdate toxicity between laboratory and field conditions due to leaching and aging processes. Toxicity thresholds were determined as the HC5–50 (median hazardous concentration for 5% of the species, i.e. median 95% protection level) derived from the species sensitivity distribution of ecotoxicity data after bioavailability corrections. Uncertainty analysis illustrated that the HC5–50 provides a robust and ecologically relevant predicted no-effect concentration (PNEC) for risk characterisation. The 10th and 90th percentiles for site-specific PNEC values in European agricultural soil are 10.7 and 168mgMokg–1 dry weight respectively based on a large survey of metal concentrations and soil properties in arable land soils. Total soil Mo concentrations in these soils are below corresponding PNEC values at most locations, suggesting no regional risks of molybdate to soil organisms at this scale. The information presented can be used in the EU risk-assessment framework as well as for national and international regulatory purposes for the setting of soil quality criteria based on total molybdenum concentrations, soil pH and clay content.
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: Elsevier BV
Date: 05-2018
Publisher: Wiley
Date: 17-12-2010
Publisher: Wiley
Date: 11-2003
DOI: 10.1897/02-503
Abstract: Soil microbial processes are readily disturbed by added zinc (Zn) in laboratory ecotoxicity tests. This study compares Zn toxicity between freshly spiked soils and soils that have been contaminated with Zn in the field. Soils were s led in three transects ( 0.05) or increased significantly with soil Zn concentrations in the transect soils. These increases could not be explained by soil pH or % soil organic carbon. Leaching soils after spiking significantly lowered the toxic effects of Zn on nitrification or on substrate-induced respiration. The soil solution Zn concentrations of field soils were always smaller than in spiked soils at equivalent total Zn. Highest soil solution Zn concentrations were always lower than the soil-solution EC50s of spiked soils. It is concluded that there is a large discrepancy in microbial responses to elevated Zn between spiked soils (unleached) and field-contaminated soils and there is a need to explain this discrepancy in terms of Zn availability, adaptation processes, and additional soil factors controlling the microbial processes.
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: 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: 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: 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: Springer Science and Business Media LLC
Date: 16-03-2012
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.FOODCHEM.2018.04.125
Abstract: Chelation of iron and zinc in wheat as phytates lowers their bio-accessibility. Steeping and germination (15 °C, 120 h) lowered phytate content from 0.96% to only 0.81% of initial dry matter. A multifactorial experiment in which (steeped/germinated) wheat was subjected to different time (2-24 h), temperature (20-80 °C) and pH (2.0-8.0) conditions showed that hydrothermal processing of germinated (15 °C, 120 h) wheat at 50 °C and pH 3.8 for 24 h reduced phytate content by 95%. X-ray absorption near-edge structure imaging showed that it indeed abolished chelation of iron to phytate. It also proved that iron was oxidized during steeping, germination and hydrothermal processing. It was further shown that zinc and iron bio-accessibility were respectively 3 and 5% in wheat and 27 and 37% in hydrothermally processed wheat. Thus, hydrothermal processing of (germinated) wheat paves the way for increasing elemental bio-accessibility in whole grain-based products.
Publisher: Springer Science and Business Media LLC
Date: 23-04-2009
Abstract: Biological ammonia oxidation had long been thought to be mediated solely by discrete clades of beta- and gamma-proteobacteria (ammonia-oxidizing bacteria AOB). However, ammonia-oxidizing Crenarchaeota (ammonia-oxidizing archaea AOA) have recently been identified and proposed to be the dominant agents of ammonia oxidation in soils. Nevertheless, the dynamics of AOB versus AOA, and their relative contribution to soil ammonia oxidation and ecosystem functioning on stress and environmental perturbation, remain unknown. Using a 3-year longitudinal field study and the amoA gene as a molecular marker, we demonstrate that AOB, but not AOA, mediate recovery of nitrification after zinc (Zn) contamination. Pristine soils showed approximately equal amoA gene copy numbers and transcript levels for AOB and AOA. At an intermediate Zn dose (33.7 mmol Zn per kg), ammonia oxidation was completely inhibited, and the numbers of AOB and AOA amoA gene copies and gene transcripts were reduced. After 2 years, ammonia oxidation in the field soils was fully restored to preexposure levels, and this restoration of function was concomitant with an increase of AOB amoA gene copy and gene transcript numbers. Analysis of the restored community revealed domination by a phylogenetically distinct Zn-tolerant Nitrosospira sp. community. In contrast, the numbers of AOA amoA gene copies and gene transcripts remained 3- and 10(4)-fold lower than recovered AOB values, respectively. Thus, although recent findings have emphasized a dominant role of archaea in soil-borne ammonia oxidation, we demonstrate that a phylogenetic shift within the AOB community drives recovery of nitrification from Zn contamination in this soil.
Publisher: Springer Science and Business Media LLC
Date: 26-04-2016
DOI: 10.1038/SREP25127
Abstract: The use of biochar can contribute to carbon (C) storage in soil. Upon addition of biochar, there is a spatial reorganization of C within soil particles, but the mechanisms remain unclear. Here, we used Fourier transformed infrared-microscopy and confocal laser scanning microscopy to examine this reorganization. A silty-loam soil was amended with three different organic residues and with the biochar produced from these residues and incubated for 237 d. Soil respiration was lower in biochar-amended soils than in residue-amended soils. Fluorescence analysis of the dissolved organic matter revealed that biochar application increased a humic-like fluorescent component, likely associated with biochar-C in solution. The combined spectroscopy-microscopy approach revealed the accumulation of aromatic-C in discrete spots in the solid-phase of microaggregates and its co-localization with clay minerals for soil amended with raw residue or biochar.The co-localization of aromatic-C:polysaccharides-C was consistently reduced upon biochar application. We conclude that reduced C metabolism is an important mechanism for C stabilization in biochar-amended soils.
Publisher: Springer Netherlands
Date: 10-11-2010
Publisher: Wiley
Date: 03-2005
DOI: 10.1897/04-036R.1
Abstract: Abstract-Elevated metal concentrations in soils can disturb the soil ecosystem thus, researchers strive to identify the most sensitive assay for detection of the early signs of toxicity. The purpose of the present study was to compare eight different ecotoxicological endpoints on the same set of metal-contaminated soils that were collected from seven series of soils s led during field trials. The endpoints are based on three microbial assays (potential nitrification rate [PNR], substrate-induced respiration [SIR], and basal respiration [BR]) and two plant growth tests, one of which included symbiotic N fixation. The overall sensitivity of the endpoints to detect statistically significant adverse effects ranked as follows: PNR > SIR (lag time) > plant yield and N fixation > SIR (respiration after 24 and 48 h) > BR. The lowest adverse effect concentrations were found with the PNR at 7 mg kg(-1) of Cd and 107 mg kg(-1) of Zn. The variability of these endpoints among different uncontaminated soils was additionally assessed on 14 soil s les. That variability showed a strong correlation with sensitivity scores, illustrating that metal-sensitive endpoints have a large natural variability. We question the ecological relevance of highly sensitive microbial assays, because they tend to have a large natural variability. The identification of toxicity in the field requires endpoints that are highly sensitive and that do not vary greatly among soils (i.e., robust) however, no such endpoint was found in the present study. The endpoints that combined average sensitivity and robustness were SIR (lag time), clover yield, and N fixation in clover.
Publisher: Wiley
Date: 11-2004
DOI: 10.1897/04-27
Abstract: The effects of soil properties and zinc (Zn) availability on the toxicity of Zn to soil microbial processes are poorly understood. Three soil microbial processes--potential nitrification rate (PNR), substrate (glucose)-induced respiration (SIR), and a maize residue respiration (MRR)--were measured in 15 European topsoils (pH 3.0-7.5 total Zn 7-191 mg/kg) that were freshly spiked with ZnCl2. The Zn toxicity thresholds of 20 to 50% effective concentrations (EC20s and EC50s) based on total concentrations of Zn in soil varied between 5- and 26-fold among soils, depending on the assay. The Zn toxicity thresholds based on Zn concentrations in soil solution varied at least 10-fold more than corresponding total metal thresholds. Soil pH had no significant effect on soil total Zn toxicity thresholds, whereas significant positive correlations were found between these thresholds and background Zn for the PNR and SIR test (r = 0.74 and 0.71, respectively log-log correlations). No such trend was found for the MRR test. Soil solution-based thresholds showed highly significant negative correlations with soil pH for all assays that might be explained by competition of H+ for binding sites, as demonstrated for aquatic species. The microbial assays were also applied to soils collected under galvanized pylons (three sites) where concentrations of total Zn were up to 2,100 to 3,700 mg Zn/kg. Correlations between concentrations of total Zn and microbial responses were insignificant at all sites even though spiking reference s les to equivalent concentrations reduced microbial activities up to more than 10-fold. Differences in response between spiked and field soils are partly but not completely attributed to the large differences in concentrations of Zn in soil solution. We conclude that soil pH has no significant effect on Zn toxicity to soil microbial processes in laboratory-spiked soils, and we suggest that community tolerance takes place at both background and elevated Zn concentrations in soil.
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: 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/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: 26-03-2015
DOI: 10.1111/GCBB.12250
Publisher: Wiley
Date: 07-04-2015
DOI: 10.1002/ETC.2902
Abstract: To incorporate metal mixture toxicity effects into risk-assessment procedures, more information is needed about combined and interactive effects of metal mixtures during chronic exposure. The authors investigated the toxicity of binary Ni-Zn mixtures in 2 independent full-factorial experiments using standard chronic (21-d) Daphnia magna reproduction toxicity tests. Global statistical analysis (i.e., when considering all investigated mixture treatments simultaneously) showed noninteractive effects according to the concentration addition model and significant synergistic effects according to the independent action model. However, treatment-specific statistical analysis revealed that both occurrence and type of interactive effect were dependent on the effect size at which Ni and Zn were combined in the mixture. Only noninteractive or weakly antagonistic effects occurred in mixture treatments in which each of the in idual metals produced only weak adverse effects on its own (i.e., ≤20% reduction of reproductive performance). On the other side of the spectrum, synergistic mixture effects occurred in all mixture treatments where both metals already caused a > 20% (for independent action) and a > 40% (for concentration addition) effect on reproduction on their own. Because low effect sizes are the most relevant in most regulatory frameworks, the authors' data suggest that the concentration addition and independent action mixture toxicity models can both serve as conservative models for predicting effects of Ni-Zn mixtures. The present study highlights the importance of investigating metal mixture toxicity at low effect sizes and warns against extrapolating conclusions about metal mixture interactions from high to low effect sizes.
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: Elsevier BV
Date: 02-2013
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: Wiley
Date: 31-01-2007
Publisher: Elsevier BV
Date: 04-2004
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: Wiley
Date: 21-12-2009
DOI: 10.1002/ETC.16
Abstract: Adaptation of soil microbial communities to elevated copper (Cu) concentrations has been well documented. However, effects of long-term Cu exposure on adaptation responses associated with functional stability and structural composition within the nitrifying community are still unknown. Soils were s led in three field sites (Denmark, Thailand, and Australia) where Cu gradients had been established from 3 to 80 years prior to s ling. In each field site, the potential nitrification rate (PNR) decreased by over 50% with increasing soil Cu, irrespective of a 20 to >200-fold increase in Cu tolerance (at the highest soil Cu) among the nitrifying communities. This increased tolerance was associated with decreasing numbers (15-120-fold) of ammonia-oxidizing bacteria (AOB), except in the oldest contaminated field site, decreasing numbers of ammonia-oxidizing archaea (AOA 10-130-fold) and differences in the operational taxonomic unit (OTU) composition of the AOB and, to a lesser extent, AOA communities. The sensitivity of nitrifying communities, previously under long-term Cu exposure, to additional stresses was assessed. Nitrification in soils from the three field sites was measured following acidification, pesticide addition, freeze-thaw cycles, and dry-rewetting cycles. Functional stability of the nitrification process was assessed immediately after stress application (resistance) and after an additional three weeks of incubation (resilience). No indications were found that long-term Cu exposure affected the sensitivity to the selected stressors, suggesting that resistance and resilience were unaffected. It was concluded that the nitrifying community changed structurally in all long-term Cu-exposed field sites and that these changes were associated with increased Cu tolerance but not with a loss of functional stability.
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: Springer Science and Business Media LLC
Date: 06-03-2013
Publisher: American Chemical Society (ACS)
Date: 03-08-2017
Abstract: Layered double hydroxides (LDHs) used to recover P from wastewater have recently been proposed as new slow-release fertilizers. Here, the use of P-exchanged Mg-Al LDHs as powdered or granulated fertilizer is explored and compared with monoammonium phosphate (MAP), a fully water-soluble fertilizer, and with struvite, a recycled phosphate fertilizer with lower solubility. First, these three fertilizers were compared in a 100-day incubation experiment using P diffusion visualization and chemical analysis to assess P release from either granules or powdered fertilizer in three different soils. By the end of the incubation, 74-90% of P remained within the LDH granule, confirming a slow release. Second, a pot experiment was performed with wheat (Triticum aestivum) in an acid and a calcareous soil. The granular treatment resulted in a considerably higher P uptake for MAP compared to LDH and struvite. For the powder treatments, the P uptake was less than for granular MAP and was largely unaffected by the chemical form. The LDHs and struvite showed a lower agronomic effectiveness than granular MAP, but the benefits of their use in P recycling, potential residual value, and environmental benefits may render these slow-release fertilizers attractive.
Publisher: Wiley
Date: 11-04-2005
Publisher: Wiley
Date: 31-01-2007
Publisher: American Chemical Society (ACS)
Date: 12-05-2023
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.
No related grants have been discovered for Erik Smolders.