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1.
Anal Chem ; 94(11): 4584-4593, 2022 03 22.
Artículo en Inglés | MEDLINE | ID: mdl-35276040

RESUMEN

Synchrotron-based X-ray fluorescence microscopy (XFM) analysis is a powerful technique that can be used to visualize elemental distributions across a broad range of sample types. Compared to conventional mapping techniques such as laser ablation inductively coupled plasma mass spectrometry or benchtop XFM, synchrotron-based XFM provides faster and more sensitive analyses. However, access to synchrotron XFM beamlines is highly competitive, and as a result, these beamlines are often oversubscribed. Therefore, XFM experiments that require many large samples to be scanned can penalize beamline throughput. Our study was largely driven by the need to scan large gels (170 cm2) using XFM without decreasing beamline throughput. We describe a novel approach for acquiring two sets of XFM data using two fluorescence detectors in tandem; essentially performing two separate experiments simultaneously. We measured the effects of tandem scanning on beam quality by analyzing a range of contrasting samples downstream while simultaneously scanning different gel materials upstream. The upstream gels were thin (<200 µm) diffusive gradients in thin-film (DGT) binding gels. DGTs are passive samplers that are deployed in water, soil, and sediment to measure the concentration and distribution of potentially bioavailable nutrients and contaminants. When deployed on soil, DGTs are typically small (2.5 cm2), so we developed large DGTs (170 cm2), which can be used to provide extensive maps to visualize the diffusion of fertilizers in soil. Of the DGT gel materials tested (bis-acrylamide, polyacrylamide, and polyurethane), polyurethane gels were most suitable for XFM analysis, having favorable handling, drying, and analytical properties. This gel type enabled quantitative (>99%) transmittance with minimal (<3%) flux variation during raster scanning, whereas the other gels had a substantial effect on the beam focus. For the first time, we have (1) used XFM for mapping analytes in large DGTs and (2) developed a tandem probe analysis mode for synchrotron-based XFM, effectively doubling throughput. The novel tandem probe analysis mode described here is of broad applicability across many XFM beamlines as it could be used for future experiments where any uniform, highly transmissive sample could be analyzed upstream in the "background" of downstream samples.


Asunto(s)
Poliuretanos , Sincrotrones , Difusión , Geles , Suelo/química
2.
Environ Exp Bot ; 177: 104122, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-34103771

RESUMEN

Pteris vittata (PV) and Pteris quadriaurita (PQ) are reported to hyperaccumulate arsenic (As) when grown in Asrich soil. Yet, little is known about the impact of their unique As accumulation mechanisms on As transformations and cycling at the soil-root interface. Using a combined approach of two-dimensional (2D), sub-mm scale solute imaging of arsenite (AsIII), arsenate (AsV), phosphorus (P), manganese (Mn), iron (Fe) and oxygen (O2), we found localized patterns of AsIII/AsV redox transformations in the PV rhizosphere (AsIII/AsV ratio of 0.57) compared to bulk soil (AsIII/AsV ratio of ≤0.04). Our data indicate that the high As root uptake, translocation and accumulation from the As-rich experimental soil (2080 mg kg-1) to PV fronds (6986 mg kg-1) induced As detoxification via AsV reduction and AsIII root efflux, leading to AsIII accumulation and re-oxidation to AsV in the rhizosphere porewater. This As cycling mechanism is linked to the reduction of O2 and MnIII/IV (oxyhydr)oxides resulting in decreased O2 levels and increased Mn solubilization along roots. Compared to PV, we found 4-fold lower As translocation to PQ fronds (1611 mg kg-1), 2-fold lower AsV depletion in the PQ rhizosphere, and no AsIII efflux from PQ roots, suggesting that PQ efficiently controls As uptake to avoid toxic As levels in roots. Analysis of root exudates obtained from soil-grown PV showed that As acquisition by PV roots was not associated with phytic acid release. Our study demonstrates that two closely-related As-accumulating ferns have distinct mechanisms for As uptake modulating As cycling in As-rich environments.

3.
Environ Sci Technol ; 53(24): 14620-14629, 2019 12 17.
Artículo en Inglés | MEDLINE | ID: mdl-31738055

RESUMEN

Boron is a finite resource, which has been listed as a critical raw material in the EU since 2014. Glass, frits and ceramics production, as well as fertilizers are among the major uses of B. Moreover, about 50 000 t B have been applied as fire retardant and pest repellent in cellulose fiber insulation (CFI) in Europe since the 1980s. Here we propose the end-of-life utilization of borated CFI as B fertilizer, to decrease societal B consumption and to avoid costly and potentially environmentally harmful CFI incineration and deposition in landfills. In a case study, we show that CFI biochar can provide substantial amounts of B to rapeseed and sunflower, with the B plant-availability being comparable to sodium tetraborate, a conventional B fertilizer. The annual B fertilizer consumption of the EU is estimated at ∼4000 t B yr-1, which could be sustained by the B currently installed as CFI for >10 years. In addition, the annual use of B in CFI of 1100 t B yr-1 could cover ∼25% of the annual B fertilizer demand of the EU. Hence, conversion of CFI to B fertilizer provides a meaningful end-of-life strategy, which would contribute to a more resource-efficient and sustainable economy and to several of the UN Sustainable Development Goals.


Asunto(s)
Boratos , Fertilizantes , Europa (Continente) , Incineración , Reciclaje
4.
Environ Sci Technol ; 53(9): 5359-5368, 2019 05 07.
Artículo en Inglés | MEDLINE | ID: mdl-30994336

RESUMEN

Crops may require Si fertilization to sustain yields. Potential Si fertilizers include industrial byproducts (e.g., steel slags), mined minerals (CaSiO3), fused Ca-Mg-phosphates, biochar, ash, diatomaceous earth, and municipal sewage sludge. To date, no extraction method was shown to accurately predict plant availability of Si from such chemically diverse Si fertilizers. We tested a wide range of products in greenhouse experiments and related the plant Si content to Si extracted by several common Si fertilizer tests: 5-day extraction in Na2CO3-NH4NO3, 0.5 mol L-1 HCl, and Resin extraction. In addition, we tested a novel sink extraction approach for Si(OH)40 that utilizes a dialysis membrane filled with ferrihydrite ("Iron Bag"). Wheat straw biochars and ash exhibited equivalent or marginally higher Si solubility and availability compared to wheat straw. Thermo-chemically treated municipal sewage sludge, as well as diatomaceous earth, did not release substantial amounts of Si. The Resin and the Iron Bag extraction methods gave the best results to predict plant availability of Si. These methods better reproduce the conditions of fertilizer dissolution in soil and around the root by (1) buffering the pH close to neutral and (2) extracting the dissolved Si(OH)40 with ferrihydrite (Iron Bag method) for maximum quantitative extraction.


Asunto(s)
Fertilizantes , Silicio , Diálisis Renal , Aguas del Alcantarillado , Suelo , Triticum
5.
Ecotoxicology ; 28(6): 599-611, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-31140046

RESUMEN

Copper-based fungicides have been used for a long time in viticulture and have accumulated in many vineyard soils. In this study, incrementing Cu(OH)2-based fungicide application from 0.05 to 5 g Cu kg-1 on two agricultural soils (an acidic sandy loam (L, pH 4.95) and an alkaline silt loam (D, pH 7.45)) resulted in 5 times more mobile Cu in the acidic soil. The most sensitive parameters of alfalfa (Medicago sativa) growing in these soils were the root nodule number, decreasing to 34% and 15% of the control at 0.1 g Cu kg-1 in soil L and at 1.5 g Cu kg-1 in soil D, respectively, as well as the nodule biomass, decreasing to 25% and 27% at 0.5 g Cu kg-1 in soil L and at 1.5 g Cu kg-1 in soil D, respectively. However, the enzymatic N2-fixation was not directly affected by Cu in spite of the presence of Cu in the meristem and the zone of effective N2-fixation, as illustrated by chemical imaging. The strongly different responses observed in the two tested soils reflect the higher buffering capacity of the alkaline silt loam and showed that Cu mitigation and remediation strategies should especially target vineyards with acidic, sandy soils.


Asunto(s)
Cobre/metabolismo , Fungicidas Industriales/efectos adversos , Medicago sativa/efectos de los fármacos , Fijación del Nitrógeno/efectos de los fármacos , Nodulación de la Raíz de la Planta/efectos de los fármacos , Disponibilidad Biológica , Hidróxidos/metabolismo , Medicago sativa/crecimiento & desarrollo , Medicago sativa/microbiología
6.
Anal Bioanal Chem ; 408(29): 8333-8341, 2016 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-27687185

RESUMEN

A diffusive gradient in thin films (DGT) technique, based on a strongly basic anion exchange resin (Amberlite IRA-400), was successfully tested for 34S/32S analysis in labile soil sulfate. Separation of matrix elements (Na, K, and Ca) that potentially cause non-spectral interferences in 34S/32S analysis by MC ICP-MS (multi-collector inductively coupled plasma-mass spectrometry) during sampling of sulfate was demonstrated. No isotopic fractionation caused by diffusion or elution of sulfate was observed below a resin gel disc loading of ≤79 µg S. Above this threshold, fractionation towards 34S was observed. The method was applied to 11 different topsoils and one mineral soil profile (0-100 cm depth) and compared with soil sulfate extraction by water. The S amount and isotopic ratio in DGT-S and water-extractable sulfate correlated significantly (r 2 = 0.89 and r 2 = 0.74 for the 11 topsoils, respectively). The systematically lower 34S/32S isotope ratios of the DGT-S were ascribed to mineralization of organic S.

7.
Environ Sci Technol ; 49(10): 6109-16, 2015 May 19.
Artículo en Inglés | MEDLINE | ID: mdl-25877251

RESUMEN

Using numerical simulation of diffusion inside diffusive gradients in thin films (DGT) samplers, we show that the effect of lateral diffusion inside the sampler on the solute flux into the sampler is a nonlinear function of the diffusion layer thickness and the physical sampling window size. In contrast, earlier work concluded that this effect was constant irrespective of parameters of the sampler geometry. The flux increase caused by lateral diffusion inside the sampler was determined to be ∼8.8% for standard samplers, which is considerably lower than the previous estimate of ∼20%. Lateral diffusion is also propagated to the diffusive boundary layer (DBL), where it leads to a slightly stronger decrease in the mass uptake than suggested by the common 1D diffusion model that is applied for evaluating DGT results. We introduce a simple correction procedure for lateral diffusion and demonstrate how the effect of lateral diffusion on diffusion in the DBL can be accounted for. These corrections often result in better estimates of the DBL thickness (δ) and the DGT-measured concentration than earlier approaches and will contribute to more accurate concentration measurements in solute monitoring in waters.


Asunto(s)
Monitoreo del Ambiente/métodos , Modelos Teóricos , Contaminantes Químicos del Agua/análisis , Agua/química , Simulación por Computador , Difusión , Soluciones
8.
Environ Sci Technol ; 49(7): 4522-9, 2015 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-25782052

RESUMEN

A metal-accumulating willow was grown under greenhouse conditions on a Zn/Cd-polluted soil to investigate the effects of sulfur (S(0)) application on metal solubility and plant uptake. Soil porewater samples were analyzed 8 times during 61 days of growth, while DGT-measured metal flux and O2 were chemically mapped at selected times. Sulfur oxidation resulted in soil acidification and related mobilization of Mn, Zn, and Cd, more pronounced in the rooted compared to bulk soil. Chemical imaging revealed increased DGT-measured Zn and Cd flux at the root-soil interface. Our findings indicated sustained microbial S(0) oxidation and associated metal mobilization close to root surfaces. The localized depletion of O2 along single roots upon S(0) addition indicated the contribution of reductive Mn (oxy)hydoxide dissolution with Mn eventually becoming a terminal electron acceptor after depletion of O2 and NO3(-). The S(0) treatments increased the foliar metal concentrations (mg kg(-1) dwt) up to 10-fold for Mn, (5810 ± 593), 3.3-fold for Zn (3850 ± 87.0), and 1.7-fold for Cd (36.9 ± 3.35), but had no significant influence on biomass production. Lower metal solubilization in the bulk soils should translate into reduced leaching, offering opportunities for using S(0) as environmentally favorable amendment for phytoextraction of metal-polluted soils.


Asunto(s)
Metales/metabolismo , Salix/metabolismo , Contaminantes del Suelo/metabolismo , Suelo/química , Sulfatos/metabolismo , Azufre/metabolismo , Biodegradación Ambiental , Concentración de Iones de Hidrógeno , Espectrometría de Masas , Oxígeno/metabolismo , Rizosfera , Solubilidad
9.
Environ Sci Technol ; 49(3): 1594-602, 2015 Feb 03.
Artículo en Inglés | MEDLINE | ID: mdl-25579402

RESUMEN

Although the analytical performance of the diffusive gradients in thin films (DGT) technique is well investigated, there is no systematic analysis of the DGT measurement uncertainty and its sources. In this study we determine the uncertainties of bulk DGT measurements (not considering labile complexes) and of DGT-based chemical imaging using laser ablation - inductively coupled plasma mass spectrometry. We show that under well-controlled experimental conditions the relative combined uncertainties of bulk DGT measurements are ∼10% at a confidence interval of 95%. While several factors considerably contribute to the uncertainty of bulk DGT, the uncertainty of DGT LA-ICP-MS mainly depends on the signal variability of the ablation analysis. The combined uncertainties determined in this study support the use of DGT as a monitoring instrument. It is expected that the analytical requirements of legal frameworks, for example, the EU Drinking Water Directive, are met by DGT sampling.


Asunto(s)
Técnicas de Química Analítica/métodos , Técnicas de Química Analítica/instrumentación , Difusión , Diseño de Equipo/normas , Espectrometría de Masas/métodos , Incertidumbre
10.
New Phytol ; 203(4): 1161-1174, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-24890330

RESUMEN

For the first time, phytosiderophore (PS) release of wheat (Triticum aestivum cv Tamaro) grown on a calcareous soil was repeatedly and nondestructively sampled using rhizoboxes combined with a recently developed root exudate collecting tool. As in nutrient solution culture, we observed a distinct diurnal release rhythm; however, the measured PS efflux was c. 50 times lower than PS exudation from the same cultivar grown in zero iron (Fe)-hydroponic culture. Phytosiderophore rhizosphere soil solution concentrations and PS release of the Tamaro cultivar were soil-dependent, suggesting complex interactions of soil characteristics (salinity, trace metal availability) and the physiological status of the plant and the related regulation (amount and timing) of PS release. Our results demonstrate that carbon and energy investment into Fe acquisition under natural growth conditions is significantly smaller than previously derived from zero Fe-hydroponic studies. Based on experimental data, we calculated that during the investigated period (21-47 d after germination), PS release initially exceeded Fe plant uptake 10-fold, but significantly declined after c. 5 wk after germination. Phytosiderophore exudation observed under natural growth conditions is a prerequisite for a more accurate and realistic assessment of Fe mobilization processes in the rhizosphere using both experimental and modeling approaches.


Asunto(s)
Exudados de Plantas/metabolismo , Raíces de Plantas/metabolismo , Sideróforos/metabolismo , Suelo , Triticum/crecimiento & desarrollo , Triticum/metabolismo , Ácido Azetidinocarboxílico/análogos & derivados , Ácido Azetidinocarboxílico/metabolismo , Biomasa , Carbono/metabolismo , Cobre/metabolismo , Conductividad Eléctrica , Concentración de Iones de Hidrógeno , Hierro/metabolismo , Brotes de la Planta/metabolismo , Rizosfera , Suelo/química , Solubilidad , Soluciones , Especificidad de la Especie , Agua , Zinc/metabolismo
11.
Environ Sci Technol ; 48(15): 8498-506, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24967508

RESUMEN

In wetland-adapted plants, such as rice, it is typically root apexes, sites of rapid entry for water/nutrients, where radial oxygen losses (ROLs) are highest. Nutrient/toxic metal uptake therefore largely occurs through oxidized zones and pH microgradients. However, the processes controlling the acquisition of trace elements in rice have been difficult to explore experimentally because of a lack of techniques for simultaneously measuring labile trace elements and O2/pH. Here, we use new diffusive gradients in thin films (DGT)/planar optode sandwich sensors deployed in situ on rice roots to demonstrate a new geochemical niche of greatly enhanced As, Pb, and Fe(II) mobilization into solution immediately adjacent to the root tips characterized by O2 enrichment and low pH. Fe(II) mobilization was congruent to that of the peripheral edge of the aerobic root zone, demonstrating that the Fe(II) mobilization maximum only developed in a narrow O2 range as the oxidation front penetrates the reducing soil. The Fe flux to the DGT resin at the root apexes was 3-fold higher than the anaerobic bulk soil and 27 times greater than the aerobic rooting zone. These results provide new evidence for the importance of coupled diffusion and oxidation of Fe in modulating trace metal solubilization, dispersion, and plant uptake.


Asunto(s)
Arsénico/análisis , Hierro/análisis , Plomo/análisis , Oryza , Raíces de Plantas , Contaminantes del Suelo/análisis , Difusión , Concentración de Iones de Hidrógeno , Oxidación-Reducción , Oxígeno
12.
Anal Chem ; 85(24): 12028-36, 2013 Dec 17.
Artículo en Inglés | MEDLINE | ID: mdl-24256092

RESUMEN

We report on a novel gel based on diffusive gradients in thin films (DGT) for the simultaneous measurement of cations and anions and its suitability for high resolution chemical imaging by using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The new high resolution mixed binding gel (HR-MBG) is based on zirconium-hydroxide and suspended particulate reagent-iminodiacetate (SPR-IDA) as resin materials which are embedded in an ether-based urethane polymer hydrogel. The use of this polymer hydrogel material allows the production of ultrathin, highly stable and tear-proof resin gel layers with superior handling properties compared to existing ultrathin polyacrylamide gels. The gel was characterized regarding its uptake kinetics, the anion and cation capacities, and the effects of pH, ionic strength, and aging on the performance of the HR-MBG. Our results demonstrate the capability of this novel gel for concomitant sampling of anions and cations. The suitability of this new gel type for DGT chemical imaging at submm spatial resolution in soils using LA-ICPMS is shown. 2D images of P, As, Co, Cu, Mn, and Zn distributions around roots of Zea mays L. demonstrate the new opportunities offered by the HR-MBG for high-resolution mapping of solute dynamics in soil and sediment hotspots, such as the rhizosphere, by simultaneous observation of anionic and cationic solute species.


Asunto(s)
Técnicas de Química Analítica/métodos , Calibración , Difusión , Geles , Concentración de Iones de Hidrógeno , Hidróxidos/química , Iminoácidos/química , Cinética , Límite de Detección , Concentración Osmolar , Rizosfera , Suelo/química , Factores de Tiempo , Circonio/química
13.
Appl Environ Microbiol ; 79(17): 5094-103, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23793627

RESUMEN

The bioavailability of metals in soil is often cited as a limiting factor of phytoextraction (or phytomining). Bacterial metabolites, such as organic acids, siderophores, or biosurfactants, have been shown to mobilize metals, and their use to improve metal extraction has been proposed. In this study, the weathering capacities of, and Ni mobilization by, bacterial strains were evaluated. Minimal medium containing ground ultramafic rock was inoculated with either of two Arthrobacter strains: LA44 (indole acetic acid [IAA] producer) or SBA82 (siderophore producer, PO4 solubilizer, and IAA producer). Trace elements and organic compounds were determined in aliquots taken at different time intervals after inoculation. Trace metal fractionation was carried out on the remaining rock at the end of the experiment. The results suggest that the strains act upon different mineral phases. LA44 is a more efficient Ni mobilizer, apparently solubilizing Ni associated with Mn oxides, and this appeared to be related to oxalate production. SBA82 also leads to release of Ni and Mn, albeit to a much lower extent. In this case, the concurrent mobilization of Fe and Si indicates preferential weathering of Fe oxides and serpentine minerals, possibly related to the siderophore production capacity of the strain. The same bacterial strains were tested in a soil-plant system: the Ni hyperaccumulator Alyssum serpyllifolium subsp. malacitanum was grown in ultramafic soil in a rhizobox system and inoculated with each bacterial strain. At harvest, biomass production and shoot Ni concentrations were higher in plants from inoculated pots than from noninoculated pots. Ni yield was significantly enhanced in plants inoculated with LA44. These results suggest that Ni-mobilizing inoculants could be useful for improving Ni uptake by hyperaccumulator plants.


Asunto(s)
Arthrobacter/crecimiento & desarrollo , Arthrobacter/metabolismo , Brassicaceae/crecimiento & desarrollo , Brassicaceae/metabolismo , Níquel/metabolismo , Microbiología del Suelo , Biomasa , Medios de Cultivo/química , Minerales/metabolismo , Modelos Teóricos , Compuestos Orgánicos/análisis , Brotes de la Planta/química , Brotes de la Planta/crecimiento & desarrollo , Oligoelementos/análisis
14.
Soil Biol Biochem ; 60(100): 182-194, 2013 May.
Artículo en Inglés | MEDLINE | ID: mdl-23645938

RESUMEN

Phytoextraction makes use of trace element-accumulating plants that concentrate the pollutants in their tissues. Pollutants can be then removed by harvesting plants. The success of phytoextraction depends on trace element availability to the roots and the ability of the plant to intercept, take up, and accumulate trace elements in shoots. Current phytoextraction practises either employ hyperaccumulators or fast-growing high biomass plants; the phytoextraction process may be enhanced by soil amendments that increase trace element availability in the soil. This review will focus on the role of plant-associated bacteria to enhance trace element availability in the rhizosphere. We report on the kind of bacteria typically found in association with trace element - tolerating or - accumulating plants and discuss how they can contribute to improve trace element uptake by plants and thus the efficiency and rate of phytoextraction. This enhanced trace element uptake can be attributed to a microbial modification of the absorptive properties of the roots such as increasing the root length and surface area and numbers of root hairs, or by increasing the plant availability of trace elements in the rhizosphere and the subsequent translocation to shoots via beneficial effects on plant growth, trace element complexation and alleviation of phytotoxicity. An analysis of data from literature shows that effects of bacterial inoculation on phytoextraction efficiency are currently inconsistent. Some key processes in plant-bacteria interactions and colonization by inoculated strains still need to be unravelled more in detail to allow full-scale application of bacteria assisted phytoremediation of trace element contaminated soils.

15.
Heliyon ; 9(11): e21284, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37954342

RESUMEN

Reliable data on SOC stocks in forest soils is required in the context of climate change and soil health assessments but still limited by input data availability (e.g., bulk density) and methods used for stock calculation. Relatively few studies have investigated the stability of SOC in forest soils. We investigated SOC stocks and fractionation in soils beneath Norway spruce forests and grasslands in the montane zone along a gradient of mean annual precipitation (MAP). We sampled soil cores volumetrically to 40 cm depth and measured SOC in the fractions <2 mm (fine earth), >200 µm and 200-20 µm (coarse and fine POM), and <20 µm (MAOM) along with potential pedogenic controls. Total SOC stocks beneath forests in the study region, calculated by the equivalent soil mass (ESM) approach to 40 cm depth, amount to 79.0 ± 29.9 (mean ± standard deviation) Mg ha-1 (n = 20) in the mineral soil, and to 92.9 ± 30.6 Mg ha-1 including the litter layer, with a share of 55 % associated with POM. MAOM makes up ∼41 % of SOC in the uppermost mineral layer (0-5 cm) and increases to 71 % in the subsoil (20-40 cm). Multiple regression models show that MAOM is largely controlled by ammonium oxalate extractable Al (Alo) in the forest subsoils (20-40 cm), and increases with MAP in the topsoil layers (0-20 cm). Soils on carbonate rock stand out with ∼80-100 % larger shares of MAOM in the uppermost soil layers (0-10 cm) which is likely connected to higher soil pH and MAP, supporting microbial transformation and subsequent stabilisation of organic matter, which is reflected in narrower C:N ratios in MAOM and SOC. Including the litter layers, ESM-based total SOC stocks in forest soils tend to exceed those beneath grassland (80.2 ± 21.9 Mg ha-1; n = 31) by 16 %, but only by 6.4 % if calculated by the conventional fixed-depth (FD) approach. In contrast to the forest soils, SOC stocks beneath grasslands are dominated by MAOM (75.6 %). We conclude that (coniferous) forest soils are a poor reference for establishing sequestration potentials for stable SOC. The observed large proportion of POM in forest topsoils and its increase with declining MAP (indicating water availability) suggests a risk of SOC losses in response to increasing droughts due to climate change.

16.
Sci Total Environ ; 882: 163554, 2023 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-37088395

RESUMEN

Tungsten (W)-based shots are considered more environmentally safe than lead (Pb)-based shots, but knowledge about the W-shot fate in the soil environment is still limited, especially in terms of minor constituents such as iron, copper, and nickel (Ni). Contaminant behaviour in soil strongly depends on pH; in turn, the corrosion of metal composites may affect the pH locally. The aim of this study was to compare Pb- and W-shot weathering dynamics in soil (silt loam, pH 6.3) and reveal the interplay of shot weathering-induced pH-changes on the mobility of elements using in situ chemical imaging (Diffusive gradients in thin films for labile elements, planar optodes for soil pH) and batch incubation experiments over time (16 months). Despite our expectation to find acidification due to W oxidation, we observed a pH increase by 0.2 units in extracted soil solutions and by 0.6 units in the soil around W-shots as Ni dissolved from the binder phase of the shot. After 10 weeks, release of labile Ni was 3-times higher compared to W despite the low Ni content in the shot (7 %, m/m). Pb-shot oxidation increased soil solution pH by 0.5 units which likely supported mobility of Pb-shot-derived antimony (Sb). Steep gradients of labile W and Pb and soil solution concentrations <0.8 µmol L-1 indicated that transfer from shot to soil was low. Contrastingly, labile Ni and Sb were found up to ~4 mm from the shot surface and in higher soil solution concentrations as suggested by the shot constitution, indicating higher mobility of minor as compared to major shot constituents. After 16 months, 36 % of total Ni were dissolved in the soil solution highlighting the environmental relevance of minor shot constituents in Pb-shot alternatives after short term weathering in soil.

17.
Plant Cell Environ ; 35(9): 1558-66, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22452489

RESUMEN

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 samplers 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.


Asunto(s)
Brassica napus/metabolismo , Fósforo/metabolismo , Raíces de Plantas/metabolismo , Transporte Biológico , Tampones (Química) , Difusión , Cinética , Nanopartículas , Soluciones
19.
Sci Total Environ ; 806(Pt 2): 150486, 2022 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-34601180

RESUMEN

In the framework of the circular economy, new P fertilizers produced from diverse secondary raw materials are being developed using various technologies. Standard extraction methods (neutral ammonium citrate (NAC) and H2O) provide limited information about the agronomic efficiency of these often heterogenous new products. Here, we compared these extractions with two alternative methods: 0.5 mol L-1 NaHCO3 and a sink extraction driven by phosphate adsorption onto ferrihydrite ("Iron Bag") on 79 recycled and mineral reference fertilizers. We compared their capacity to predict shoot biomass and P content of rye (S. cereale L.) grown in a greenhouse on three soils of contrasting pH with a subset of 42 fertilizers. The median extracted P (% of total P) was H2O (1%) < NaHCO3 (25%) < Iron Bag (67%) < NAC (85%). The NaHCO3 extraction stood out as a cost-effective and reliable method to predict plant shoot biomass and P content (R2 ranging between 0.65 and 0.86 in the slightly acidic and alkaline soil). Notwithstanding, the other methods provide complementary information for a more detailed characterization of how P solubility may be impacted by e.g. soil pH, granulation, or time. The implications of this work are therefore significant for fertilizer production, regulation, and use.


Asunto(s)
Fertilizantes , Fósforo , Fosfatos , Plantas , Suelo
20.
Plant Soil ; 478(1-2): 273-281, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36277077

RESUMEN

Purpose: Root exudates are key components driving belowground interaction between plant, microbes and soil. High-end analytical approaches provide advanced insights into exudate metabolite diversity, however, the amount of total carbon (C) released by roots should always be determined as the most basic parameter when characterizing root exudation as it (i) provides quantitative information of C exuded into the surrounding soil and (ii) allows to relate the abundance of individual exudate compounds to total C released. Here we propose a simple and quick, spectrophotometry-based method to quantify total dissolved organic carbon (DOC) concentration in exudation samples that is based on measuring the absorption of a pre-filtered but otherwise untreated exudate sample at 260 nm (DOC260). Method: Exudate samples collected from different grass genotypes (Zea mays, Oryza sativa, Hordeum vulgare) grown in various experimental settings (soil, hydroponic) were analysed with the DOC260 assay and results were compared with C concentrations obtained by liquid TOC-analyser. Conclusion: We demonstrated that the DOC260 method allowed for quick and inexpensive measurements of total dissolved organic carbon concentrations in exudate samples from grass species grown under nutrient sufficient as well as under P deficient conditions. Interestingly, DOC260 failed to predict DOC concentrations in exudate samples from plants grown under Zn and Fe deficiency suggesting a strong shift in metabolite composition under micronutrient deficiency. Even though the applicability of the DOC260 method remains to be tested on exudate samples originating from dicots and plants exposed to other environmental stresses (e.g. pathogen attack, heavy metal stress, etc), it will help to increase our understanding of root exudation and related rhizosphere processes in the future.

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