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Geoengineering in lakes: welcome attraction or fatal distraction?
Mackay, E. ; Maberly, S.C. ; Pan, G. ; Reitzel, K. ; Lurling, M.F.L.L.W. - \ 2014
Inland Waters : Journal of the International Society of Limnology 4 (2014). - ISSN 2044-2041 - p. 349 - 356.
modified bentonite clay - phosphate adsorption - phosphorus release - shallow lakes - water-quality - sediment - nutrient - aluminum - removal - phoslock(r)
The use of geoengineering techniques for phosphorus management offers the promise of greater and quicker chemical and ecological recovery. It can be attractive when used with other restoration measures but should not be considered a panacea. The range of materials being proposed for use as well as the in-lake processes targeted for manipulation continues to grow. With increasing political imperatives to meet regulatory goals for water quality, we recommend a coordinated approach to the scientific understanding, costs, and integration of geoengineering with other approaches to lake management.
Description of the phosphorus sorption and desorption processes in lowland peaty clay soils
Schoumans, O.F. - \ 2013
Soil Science 178 (2013)6. - ISSN 0038-075X - p. 291 - 300.
semiarid altered wetland - acid soils - phosphate adsorption - agricultural land - organic-matter - flooded soils - iron-oxides - sandy soil - aluminum - release
To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron. A fraction of the maximum amount of sorbed P is bound reversibly (Q), which can be measured with an iron-impregnated paper. The fraction of the maximum reversibly sorbed P depends on the amount of oxalate-extractable aluminum and iron. In the topsoil, the maximum of the fraction of reversibly bound P (Qm) is about one third of maximum P sorption capacity; and in the subsoil, about two thirds. All sorption and desorption parameters are related to soil characteristics of peat samples.
Levels of lead, arsenic, mercury and cadmium in clays for oral use on the Dutch market and estimation of associated risks
Reeuwijk, N.M. ; Klerx, W.N.M. ; Kooijman, M. ; Hoogenboom, L.A.P. ; Rietjens, I.M.C.M. ; Martena, M.J. - \ 2013
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 30 (2013)9. - ISSN 1944-0049 - p. 1535 - 1545.
pregnant-women - trace-elements - contaminated soils - geophagy - bioaccessibility - bioavailability - supplementation - nutrition - aluminum - tanzania
Pregnant women in Africa, Asia and Suriname, and some immigrants in Western societies, traditionally consume clay products known by a variety of names such as mabele, calabash chalk, sikor and pimba. Furthermore, clay is used for health purposes in Western societies. Because certain clays can contain high levels of metals and metalloids, the aim of this study was to determine lead, arsenic, mercury and cadmium in clay products for oral use available on the Dutch market. Traditional clays originating from Africa (n = 10) and Suriname (n = 26), and health clays (n = 27) were sampled from 2004 up to and including 2012. Total metal and metalloid contents were measured by ICP-MS and showed maximum levels of lead, arsenic, mercury and cadmium of 99.7, 45.1, 2.2 and 0.75 mg kg(-1), respectively. In the absence of maximum limits for these type of clays, the potential exposure was estimated from the determined concentration, the estimated daily use level of the clays, and the estimated bioaccessibility of the different metals and arsenic. The intake estimates were compared with existing health-based guidance values. For lead, the use of 34 of the 36 traditional clays and two of the 27 health clays would result in intake levels exceeding the toxicological limit by up to 20-fold. Use of 15 of the 35 traditional clays and 11 of the 27 health clays would result in intake levels exceeding the toxicological limit for inorganic arsenic by up to 19-fold. Although limited bioaccessibility from the clay may limit the exposure and exceedance of the health-based guidance values, it was concluded that lead and arsenic intakes from some clay products could be of concern also because of their use by pregnant women and the potential developmental toxicity. As a result the use of these products, especially by pregnant women, should be discouraged
Human prophylactic vaccine adjuvants and their determinant role in new vaccine formulations
Perez, O. ; Batista-Duharte, A. ; Gonzalez, E. ; Zayas, C. ; Balbao, J. ; Cuello, M. ; Cabrera, O. ; Lastre, M. ; Schijns, V.E.J.C. - \ 2012
Brazilian Journal of Medical and Biological Research 45 (2012)8. - ISSN 0100-879X - p. 681 - 692.
guillain-barre-syndrome - adaptive immunity - influenza vaccine - dendritic cells - subclass restriction - antibody-responses - innate immunity - t-cells - aluminum - inflammasome
Adjuvants have been considered for a long time to be an accessory and empirical component of vaccine formulations. However, accumulating evidence of their crucial role in initiating and directing the immune response has increased our awareness of the importance of adjuvant research in the past decade. Nevertheless, the importance of adjuvants still is not fully realized by many researchers working in the vaccine field, who are involved mostly in the search for better target antigens. The choice of a proper adjuvant can be determinant for obtaining the best results for a given vaccine candidate, but it is restricted due to intellectual property and know-how issues. Consequently, in most cases the selected adjuvant continues to be the aluminum salt, which has a record of safety, but predominantly constitutes a delivery system (DS). Ideally, new strategies should combine immune potentiators (IP) and DS by mixing both compounds or by obtaining structures that contain both IP and DS. In addition, the term immune polarizer has been introduced as an essential concept in the vaccine design strategies. Here, we review the theme, with emphasis on the discussion of the few licensed new adjuvants, the need for safe mucosal adjuvants and the adjuvant/immunopotentiating activity of conjugation. A summary of toxicology and regulatory issues will also be discussed, and the Finlay Adjuvant Platform is briefly summarized.
Comparing NaOH-extractable organic matter of acid forest soils that differ in their pedogenic trends: a pyrolysis-GC/MS study
Suarez Abelenda, M. ; Buurman, P. ; Camps Arbestain, M. ; Kaal, J. ; Martinez-Cortizas, A. ; Gartzia-Bengoetxea, N. ; Macias, F. - \ 2011
European Journal of Soil Science 62 (2011)6. - ISSN 1351-0754 - p. 834 - 848.
chromatography-mass-spectrometry - gas-chromatography - chemical-composition - humic acids - fractions - peat - chemistry - horizons - aluminum - andosols
Soil organic matter (SOM) in Alu-andic Andosols and Alu-humic Umbrisols is believed to accumulate because of the protection caused by binding to aluminium (Al). We investigated soils that differed in the abundance of organo-Al complexes to determine the effect of such binding on SOM chemistry. For this, the surface horizons of three types of acid soils in the Basque Country (northern Spain) under forest stands were studied: (i) Alu-andic Andosols (AND soils) on basalts and trachytes, (ii) Umbrisols or so-called ‘aluminic’(ALU) soils also on basalts and trachytes and (iii) soils with a podzolizing trend (POD), on quartzites. Values of Al extractable with sodium pyrophosphate (Alp) in the surface horizons of these soils ranged between 8.5 and 13.1, 1.9 and 9.3, and 0.8 and 3.7 g kg-1 dry weight, for the AND, ALU and POD soils respectively. For POD and ALU soils, surface horizons were sampled at two depths, 0–5 and 5–20 cm, whereas the AND soils were sampled at different depths down to the B horizon. NaOH-extractable SOM from three AND soils, 12 ALU soils and 12 POD soils was studied by pyrolysis-gas chromatography/mass spectrometry. The POD soils had the largest loads of plant-derived markers (lignin, long-chain alkanes and alkenes, methyl ketones, fatty acids); SOM of the AND soils had the smallest amounts of plant-derived SOM and the largest amounts of microbial products (microbial sugars and N-compounds) of the soils studied. ALU soils had an intermediate pattern, as expected. The results indicate that the SOM of Alu-andic Andosols, developed from basalt and trachyte rocks, is essentially dissimilar to that of soils derived from quartz-rich parent material, under the same climate conditions and similar forest stands. The dominance of secondary (microbial-derived) SOM in Alu-andic Andosols, also observed in previous research on Sil-andic Andosols (these are dominated by short-range ordered Si compounds in contrast to the dominance of organo-Al complexes in Alu-andic Andosols), reveals the small contribution of primary (plant-derived) material to SOM in soils with andic properties
Impacts of sampling design and estimation methods on nutrient leaching of intensively monitored forest plots in the Netherlands
Vries, W. de; Wieggers, H.J.J. ; Brus, D.J. - \ 2010
Journal of Environmental Monitoring 12 (2010). - ISSN 1464-0325 - p. 1515 - 1523.
european forests - regional assessment - acid deposition - output fluxes - ecosystems - nitrate - aluminum - soils - stand
Element fluxes through forest ecosystems are generally based on measurements of concentrations in soil solution at regular time intervals at plot locations sampled in a regular grid. Here we present spatially averaged annual element leaching fluxes in three Dutch forest monitoring plots using a new sampling strategy in which both sampling locations and sampling times are selected by probability sampling. Locations were selected by stratified random sampling with compact geographical blocks of equal surface area as strata. In each sampling round, six composite soil solution samples were collected, consisting of five aliquots, one per stratum. The plot-mean concentration was estimated by linear regression, so that the bias due to one or more strata being not represented in the composite samples is eliminated. The sampling times were selected in such a way that the cumulative precipitation surplus of the time interval between two consecutive sampling times was constant, using an estimated precipitation surplus averaged over the past 30 years. The spatially averaged annual leaching flux was estimated by using the modeled daily water flux as an ancillary variable. An important advantage of the new method is that the uncertainty in the estimated annual leaching fluxes due to spatial and temporal variation and resulting sampling errors can be quantified. Results of this new method were compared with the reference approach in which daily leaching fluxes were calculated by multiplying daily interpolated element concentrations with daily water fluxes and then aggregated to a year. Results show that the annual fluxes calculated with the reference method for the period 2003–2005, including all plots, elements and depths, lies only in 53% of the cases within the range of the average ±2 times the standard error of the new method. Despite the differences in results, both methods indicate comparable N retention and strong Al mobilization in all plots, with Al leaching being nearly equal to the leaching of SO4 and NO3 with fluxes expressed in molc ha-1 yr-1. This illustrates that Al release, which is the clearest signal of soil acidification, is mainly due to the external input of SO4 and NO3.
Uncertainties in critical loads and target loads of sulphur and nitrogen for European forests: Analysis and quantification
Reinds, G.J. ; Vries, W. de - \ 2010
Science of the Total Environment 408 (2010)8. - ISSN 0048-9697 - p. 1960 - 1970.
soil acidification model - quantifying uncertainty - terrestrial ecosystems - atmospheric deposition - bayesian calibration - acid deposition - aluminum - sensitivity - solubility - horizons
An analysis of the uncertainties in critical loads and target loads of sulphur (S) and nitrogen (N) for 182 European forest soils was carried out using the Very Simple Dynamic (VSD) model. The VSD model was calibrated with a Bayesian approach using prior probability functions for model parameters based on literature data, data from 200 Dutch forest sites and from simulated denitrification rates from a detailed ecosystem model. The calibration strongly improved the fit of the model to observed soil and soil solution concentrations, especially for pH and base saturation. Calibration also narrowed down the ranges in input parameters. The uncertainty analysis showed which parameters contribute most to the uncertainty in the critical loads and target loads. Base cation weathering and deposition and the parameters describing the H–Al equilibrium in the soil solution determine the uncertainty in the maximum critical loads for S, CLmax(S), when based on the aluminium to base cation (Al/Bc) criterion. Uncertainty in CLmax(S) based on an acid neutralizing capacity (ANC) criterion is completely determined by base cation inputs alone. The denitrification fraction is the most important source of uncertainty for the maximum critical loads of N, CLmax(N). N uptake and N immobilisation determine the uncertainties in the critical load for N as a nutrient, CLnut(N). Calibration of VSD reduced the uncertainty: the coefficient of variation (CV) was reduced for all critical loads and criteria. After calibration, the CV for CLmax(S) was below 0.4 for almost all plots; however for CLmax(N) high values occurred for plots with high denitrification rates. Model calibration also improved the robustness of target load estimates: after calibration, no target loads were needed in any of the simulations for 40% of the plots, with the uncalibrated model there was a positive probability for the need of a target load for almost all plots
Phosphorus removal from soil using Fe oxide-impregnated paper: Processes and applications
Los, A.M.D. ; Temminghoff, E.J.M. ; Schenkeveld, W.D.L. ; Hiemstra, T. ; Riemsdijk, W.H. van - \ 2009
Geoderma 151 (2009)3-4. - ISSN 0016-7061 - p. 282 - 289.
p-i test - filter-paper - available phosphorus - ionic-strength - phosphate - adsorption - goethite - desorption - extraction - aluminum
Fe oxide-impregnated paper (Pi-paper) is used as an artificial Phosphorus (P) sink to study P availability in soils and runoff. Pi-papers were introduced as they would mimic P uptake by plant roots by decreasing the P concentration in solution to negligibly low levels and thus enhancing P desorption from the soils solid phase. The rate of transfer of P from soil to Pi-paper would thus be limited by the soil P desorption rate. The maximum desorption rate is indeed achieved when the original method is used in which (at least) four Pi-papers per gram soil are placed in a soil suspension (soil–solution ratio of 0.025 kg L- 1). In several studies this method has however been adapted depending on the research question of interest without investigating the effect of this adaptation to the processes involved in the transfer of P from soil to Pi-paper. The aim of this study is to improve our understanding of the processes that occur in the Pi-paper–solution–soil system and so to extend the theoretical basis of this method. Insight is gained in these processes by comparing the experimentally determined P transfer from soil to Pi-paper with P transfer that is modeled based on the measured P concentration in solution and the (kinetic) Langmuir equation of the Pi-paper. P adsorption by a Pi-paper from standard solutions is not instantaneous but can be described with a kinetic Langmuir equation that is a characteristic of the Pi-paper. Over time, the Pi-paper reaches equilibrium with the solution, and the kinetic Langmuir equation can be rewritten to a Langmuir equation. Regardless if there is equilibrium or not, P adsorption to the Pi-paper is a function of the P concentration in solution. By adding Pi-paper to a soil suspension, a re-distribution of P takes place between the reactive surface area of the soil and the new reactive surface area of the Pi-paper that initially contains no adsorbed phosphate. As opposed to the original method where the desorption rate was limiting the overall P transfer, the adsorption rate to the Pi-paper is limiting when one Pi-paper per gram soil is placed in a soil suspension (soil–solution ratio of 0.1 kg L- 1). In this situation, the P concentration in solution is found to be in equilibrium with the soil's solid phase. With increasing contact time (> ~ 24 h) the whole system approaches equilibrium. With each successive Pi-paper newly added, more P is removed from the soil system and the decrease of P in solution will be governed by the soil P desorption isotherm. Varying the number of Pi-papers and the soil to solution ratio thus has a large effect on the transfer rate between soil and Pi-paper and if either the soil desorption rate, the Pi-paper adsorption rate or a combination limits this transfer rate. With increased insight in the P transfer between soil and Pi-paper sink, it becomes possible to tailor the experimental design to help answer the research question one is interested in.
The effect of naturally acidified irrigation water on agricultural volcanic soils. The case of Asembagus, Java, Indonesia
Los, A.M.D. ; Vriend, S.P. ; Bergen, M.J. ; Gaans, R.F.M. - \ 2008
Journal of Geochemical Exploration 96 (2008)1. - ISSN 0375-6742 - p. 53 - 68.
mine tailings - forest soils - acidification - netherlands - deposition - aluminum - elements - sulfate - river - iron
Acid water from the Banyuputih river (pH similar to 3.5) is used for the irrigation of agricultural land in the Asembagus coastal area (East Java, Indonesia), with harmful consequences for rice yields. The river water has an unusual composition which is caused by seepage from the acidic Kawah Ijen crater lake into the river. This unique irrigation setting allows the study of soil acidification in situ. This paper assesses the effects of volcanogenically contaminated irrigation water on the chemical properties of the agricultural soils. The changes in soil properties were evaluated by comparing samples taken from the topsoil and sub-soil (1-3 m depth) from areas irrigated with acid water and areas irrigated with neutral water. The field survey thus resulted in four soil categories. Bulk soil composition, organic matter content, moisture content and particle size distribution were determined. Reactive phases were quantified with the selective extractions 1 M KCl, 0.1 M Na-pyrophosphate and 0.2 M acid ammonium oxalate (AAO). By comparing the four soil categories it is shown that the use of the naturally polluted irrigation water has had a large influence on the chemical composition of the topsoil. The composition of the soil solution has changed over the entire investigated soil profile. Furthermore the acid irrigation water has strongly modified the composition of the reactive phases, extracted as KCl, pyrophosphate, and AAO extractable elements, and also the bulk soil composition has been significantly modified. Overall this has resulted in the net dissolution of some elements and the net precipitation of others. The changes in the reactive phases and bulk soil composition are only apparent in the topsoil (0-20 cm) but not in the deeper soil.
Lead ion adsorption on montmorillonite-Al hydroxide polymer systems
Janssen, R.P.T. ; Bruggenwert, M.G.M. ; Dijk, G. van; Riemsdijk, W.H. van - \ 2007
European Journal of Soil Science 58 (2007)5. - ISSN 1351-0754 - p. 1136 - 1144.
hydroxyaluminum-montmorillonite - aluminum - cadmium - complexes - zinc - equilibria - exchange
Clay¿Al hydroxide polymer systems (CAlHO) can bind heavy metals effectively. Their adsorption behaviour depends on the type of metal. We studied the dependence of Al-loading and pH on the adsorption of Pb to Na-saturated montmorillonite¿Al hydroxide polymer systems. The available binding sites on the Al hydroxide polymers (AlHO) had a strong affinity for Pb ions, whereas a minor amount of Pb was bound to the clay surface. The pH had a pronounced effect on the Pb binding to the AlHO. At pH 6.0, AlHO effectively adsorbed Pb. The amount of Pb adsorbed to the AlHO, expressed per mole Al, increased with increasing amount of AlHO fixed. Lead bound to the AlHO could easily be removed by exchange and is therefore reversibly bound to the AlHO. Probably, Pb is outer-sphere bound to the AlHO and an electrostatic bonding mechanism is involved. At pH 5.0 there was almost no adsorption of Pb to the AlHO, and the adsorption of Pb to the clay surface was limited because Al3+ ions competed with Pb2+ for exchangeable sites. At pH 6.6 and relatively large Pb concentrations, separate precipitates of Pb(OH)2 and Al(OH)3 were formed. Results from experiments in pure clay systems suggest that the Pb(OH)2 precipitate was present as positively charged Pb polymers.
Element fluxes through intensively monitored forest ecosystems in Europe and their relationships with stand and site characteristics.
Vries, W. de; Salm, C. van der; Reinds, G.J. ; Erisman, J.W. - \ 2007
Environmental Pollution 148 (2007)2. - ISSN 0269-7491 - p. 501 - 513.
regional assessment - acidic deposition - output fluxes - aluminum - soils
This paper describes a European wide assessment of element budgets, using available data on deposition, meteorology and soil solution chemistry at 121 Intensive Monitoring plots. Input fluxes from the atmosphere were derived from fortnightly or monthly measurements of bulk deposition and throughfall, corrected for canopy uptake. Element outputs from the forest ecosystem were derived by multiplying fortnightly or monthly measurements of the soil solution composition at the bottom of the root zone with simulated unsaturated soil water fluxes. Despite the uncertainties in the calculated budgets, the results indicate that: (i) SO4 is still the dominant source of actual soil acidification despite the generally lower input of S than N, due to the different behaviour of S (near tracer) and N (strong retention); (ii) base cation removal due to man-induced soil acidification is limited; and (iii) Al release is high in areas with high S inputs and low base status.
Soil chemical properties under kauri (Agathis australis) in The Waitakere Ranges, New Zealand
Jongkind, A.G. ; Velthorst, E.J. ; Buurman, P. - \ 2007
Geoderma 141 (2007)3-4. - ISSN 0016-7061 - p. 320 - 331.
pyrophosphate extracts - humus complexes - forest remnants - iron - fe - al - aluminum - oxalate - carbon - forms
Kauri is known to cause low soil pH and loss of Al from the Al-hydroxy-interlayers from interlayered vermiculite. Kauri is also associated with intense podzolisation and therefore we studied the Al and Fe phases in soil under kauri and under adjacent broadleaf/treefern vegetation for comparison. Kauri accumulates significantly higher amounts of organic matter, which cause a significantly lower soil pH. This lower soil pH under kauri results in increased breakdown of alumino-silicates relative to broadleaf/treefern vegetation. At the same time, the larger amount of organic carbon in soils under kauri causes higher amounts of bound Al and Fe. In Ah-horizons under kauri, sesquioxides appear to be protected by organic matter, which renders them inaccessible to oxalate extraction. The distribution of pyrophosphate-extractable Fe and Al suggests podzolisation, but is due to a combination of transport and local weathering and complexation. The effect of kauri on the soil, as compared to adjacent tree species, appears to be generated by its longevity: large amounts of litter and leachates on one site, rather than its litter quality.
Podzolisation and soil organic matter dynamics
Buurman, P. ; Jongmans, A.G. - \ 2005
Geoderma 125 (2005)1-2. - ISSN 0016-7061 - p. 71 - 83.
methylation-mass spectrometry - podzol formation - southern queensland - chemical properties - size fractions - forest soils - bh horizons - aluminum - carbon - podzolization
Present models of podzolisation emphasize the mobilization and precipitation of dissolved organic matter. together with Al(-silicates) and Fe. Such models cannot explain the dominance of pellet-like organic matter in most boreal podzols and in well-drained podzols outside the boreal zone, and the discrepancy between the chemistry of percolating organic matter (DOC) and the organic matter accumulated in well-drained podzol-B horizons. The present paper offers an amended podzolisation theory, in which relative contribution of illuviated organic matter and root litter together with organic matter dynamics provide an explanation for the large variation in podzol morphology, It is suggested that fast organic matter dynamics as occurs on nutrient-rich parent materials in the boreal zone causes small accumulation of organic matter, mainly derived from roots. In such soils. the colors of Fe components dominate in the B horizon. Slow organic matter dynamics, as occurs on nutrient-poor parent materials and under hydromorphic circumstances, favors large organic matter accumulations in the B horizon. and a larger abundance of DOC-derived organic matter coatings. The latter group includes tropical podzols. (C) 2004 Elsevier B.V. All rights reserved.
Phosphorus mobilization in agroforestry: Organic anions, phosphatase activity and phosphorus fractions in the rhizosphere
Radersma, S. ; Grierson, P.F. - \ 2004
Plant and Soil 259 (2004)1-2. - ISSN 0032-079X - p. 209 - 219.
lupinus-albus l - soil-root interface - competitive adsorption - plant-roots - acids - aluminum - solubilization - hexaphosphate - availability - excretion
In agroforestry systems on Ferralsols in the tropics, maize crop yields are low owing to a lack of P. However, some agroforestry tree species adapted to P-fixing soils may be able to utilize less available P sources and concurrently increase P availability to adjacent crops. Adaptations for enhanced P acquisition from P-fixing soils include exudation of low molecular weight (LMW) organic anions (OA) and phosphatase enzymes. We identified major organic anions, and measured acid phosphatase activity and P fractions in the rhizosphere soil of maize (Zea mays L.), as well as in the perennial species Grevillea robusta A. Cunn., Cassia spectabilis DC. (syn. Senna spectabilis (DC.) H.S. Irwin and R.C. Barneby), Tithonia diversifolia (Hemsl.) A. Gray, Eucalyptus grandis W. Hill ex Maiden and Cedrella serrata Royle. Maize and trees were grown simultaneously at field sites and in large pots. Rhizosphere soil of C. spectabilis contained at least 29 mol oxalate g¿1 soil, derived from a high exudation rate in the range of at least 5¿10 mol oxalate m¿1 root day¿1. Incubation of Ferralsols with much lower concentrations of citrate increased labile P fractions, but there was no clear relation between OA concentration and an increase in labile P fractions in rhizosphere soils, where P mobilization and P uptake occur at the same time. Acid phosphatase activity in rhizosphere soil of all species was two to five times greater in rhizosphere soil compared with bulk soil, and correlated in rhizosphere soil of G. robusta with a shift from organic P to inorganic P in soil P fractions. We conclude that organic anion exudation and acid phosphatase activity of tree roots may increase mobilization of P in the rhizosphere, the extent of which depends on the species, the organic anion and pH. However, it is unlikely that the extent of P mobilization will benefit adjacent crop plants unless crop roots exert insufficient P-mobilization effects themselves, and grow in the rhizosphere of tree roots.
Feldspar weathering as the key to understanding soil acidification monitoring data; a study of acid sandy soils in the Netherlands
Mol, G. ; Vriend, S.P. ; Gaans, P.F.M. van - \ 2003
Chemical Geology 202 (2003)39541. - ISSN 0009-2541 - p. 417 - 441.
atmospheric deposition - woodland soils - forest soil - compositional variation - geochemical record - aluminum - water - ecosystem - rates - neutralization
Monitoring activities pose special demands on the type of survey results needed. In the early 1990s a soil acidification monitoring methodology was adopted in the Netherlands that leaned heavily on methods developed in more fundamental research, most notably the use of proton budgets. Consequently, various controversies still not resolved in the scientific debate reflect on the current practice of soil acidity monitoring and complicate interpretation of the monitoring results. In a pilot study we address the most pressing issues: capacity versus intensity parameters, choice of monitoring objective, and natural variation in the compartment to be monitored. Focus is on the major source of buffering, the possible usefulness of the historic approach, and the regional patterns present in the sandy soils of the Netherlands. In a field campaign 92 locations in sandy regions all over the country were sampled at two depths. The solid phase, the displaced soil solution, and solid phase extractions with 0.01 M CaCl2 and 0.43 M HNO3, for the 184 samples were analyzed by a variety of methods. Aluminum release is the major source of buffering and is shown to contribute substantially to acid buffering already under natural conditions. The predominant Al bearing phases in Dutch sandy soils are feldspars and secondary Al minerals; feldspars are found to be the determinative phase in acid buffering. Application of the historic approach using the subsoil as a proxy for the initial composition of the topsoil proved feasible for this regional dataset. The average depletion of the ANC(s) of 230 mmolc kg¿1 in the topsoil matches well with estimates of the total proton load since the last ice age, with the anthropogenic contribution being between 20% and 50%. Fuzzy c-means cluster analyses of the solid phase and soil solution data show a distinct regionality that was also reflected in the parameters generally used to indicate the acidity status of soils, ¿ANC(s) and Al/BC ratios. A combined insight into both solid phase and soil solution, based on a comprehensive set of parameters, proves essential for interpreting soil acidity monitoring data.
Zinc ion adsorption on montmorillonite-Al hydroxide polymer systems
Janssen, R.P.T. ; Bruggenwert, M.G.M. ; Riemsdijk, W.H. van - \ 2003
European Journal of Soil Science 54 (2003)2. - ISSN 1351-0754 - p. 347 - 355.
aluminum - cadmium
Clay¿Al hydroxide polymers (CAlHO) can bind heavy metals effectively and may play an important role in the adsorption behaviour and metal binding capacity of soils. We studied the dependence of Al loading and pH on the adsorption of Zn on Na-saturated montmorillonite¿Al hydroxide polymer systems. The available binding sites on Al hydroxide polymers (AlHO) had a very strong affinity for Zn ions. Zinc binding on the clay surface became important when the binding sites on the AlHO were nearly all occupied. The pH had a very strong effect on the Zn binding. At pH 6.6 much more Zn could be adsorbed to the AlHO than at pH 5.0. The effect of the Al:clay ratio on Zn binding was influenced by pH. At pH 6.6, Zn binding to the AlHO, expressed per mole AlHO, was independent of the Al:clay ratio, whereas at pH 5.0 this relation was dependent. This is related to the constant charge of the AlHO at pH 6.6, whereas at pH 5.0 the charge decreases with increasing Al:clay ratio. If clay¿Al hydroxide polymers are present in the soil their Zn binding to the AlHO will strongly influence the availability of the Zn.
Effect of hydroxide polymenrs on cation exchange of montmorillonite
Janssen, R.P.T. ; Bruggenwert, M.G.M. ; Riemsdijk, W.H. van - \ 2003
European Journal of Soil Science 54 (2003)2. - ISSN 1351-0754 - p. 335 - 345.
trace amounts - adsorption - aluminum - complex - systems - calcium - copper - iron
Al hydroxide polymers (AlHO) can significantly influence the cation exchange behaviour of clays. We have determined the effect of synthesized AlHO on Ca¿Na, Zn¿Na and Pb¿Na exchange for a series of exchanger compositions and two Al loadings at pH 6.0 and an ionic strength of 0.01 m. The preference for Ca on the siloxane surface of the clay¿AlHO system (CAlHO) was greater than for the pure clay, and the average KV (Vanselow selectivity coefficient) was determined to be 2.16 and 1.24, respectively. The selectivity coefficients for the exchange reactions Zn¿Na and Pb¿Na were not directly determined in CAlHO systems, because heavy-metal ions bind as well to the clay surface as to the AlHO over a wide range of pH. We have estimated the effect of the presence of AlHO on the selectivity coefficients of Zn¿Na and Pb¿Na exchange by extrapolation of the experimental results of Ca¿Na, Zn¿Na and Pb¿Na exchange for pure clay and Ca¿Na exchange for CAlHO. The average KV was increased by the presence of the AlHO from 1.23 to 2.16 for Zn¿Na exchange and from 1.59 to 2.77 for Pb¿Na exchange. The increase in the preference for the divalent cations is probably caused by parallel alignment of clay platelets by sorption of AlHO. Increasing the amount of AlHO did not change the selectivity for Ca¿Na exchange, and probably the structure of the system or the arrangement of the clay platelets and AlHO particles was not substantially changed. This was supported by the linear reduction of the cation exchange capacity with amount of AlHO present at pH 6.6. It seems likely that the selectivity coefficients for Ca¿Na, Zn¿Na and Pb¿Na exchange that we found apply in naturally occurring montmorillonite¿AlHO systems.
Generic NICA-Donnan model parameters for metal-ion binding by humic substances
Milne, C.J. ; Kinniburgh, D.G. ; Riemsdijk, W.H. van; Tipping, E. - \ 2003
Environmental Science and Technology 37 (2003)5. - ISSN 0013-936X - p. 958 - 971.
conditional stability-constants - fulvic-acid complexes - selective electrode - proton binding - humate interactions - cadmium-binding - organic-matter - cation binding - cu(ii) ion - aluminum
A total of 171 datasets of literature and experimental data for metal-ion binding by fulvic and humic acids have been digitized and re-analyzed using the NICA-Donnan model. Generic parameter values have been derived that can be used for modeling in the absence of specific metal-ion binding measurements. These values complement the previously derived generic descriptions of proton binding. For ions where the ranges of pH, concentration, and ionic strength conditions are well covered by the available data, the generic parameters successfully describe the metal-ion binding behavior across a very wide range of conditions and for different humic and fulvic acids. Where published data for other metal ions are too sparse to constrain the model well, generic parameters have been estimated by interpolating trends observable in the parameter values of the well-defined data. Recommended generic NICA-Donnan model parameters are provided for 23 metal ions (Al, Am, Ba, Ca, Cd, Cm, Co, CrIII, Cu, Dy, Eu, FeII, FeIII, Hg, Mg, Mn, Ni, Pb, Sr, ThIV, UVIO2, VIIIO, and Zn) for both fulvic and humic acids. These parameters probably represent the best NICA-Donnan description of metal-ion binding that can be achieved using existing data
Intensive monitoring of forest ecosystems in Europe; 2: atmospheric deposition and its impacts on soil solution chemistry
Vries, W. de; Reinds, G.J. ; Vel, E.M. - \ 2003
Forest Ecology and Management 174 (2003)1-3. - ISSN 0378-1127 - p. 97 - 115.
ammonium-sulfate - aluminum - netherlands - throughfall - nitrogen - acidification - model
In order to gain a better understanding of the effects of air pollution and other stress factors on forests, a Pan-European programme for intensive and continuous monitoring of forest ecosystems has been implemented in 1994. Results of this intensive monitoring programme presented in this paper are related to the surveys on atmospheric deposition and soil solution chemistry, focusing on data for 1997. Both bulk deposition and throughfall of N was higher than that of S at nearly all the plots, especially in Western Europe. The average calculated total N deposition was approximately twice as large as S. Approximately, 55% of the considered plots received an N input above 1000 molc ha-1 yr-1 (14 kg ha-1 yr-1), being a deposition level above which the species diversity of the ground vegetation may decrease. The total input of acidity ranged mostly between 200 and 4000 molc ha-1 yr-1. The deposition of sulphate, nitrate and calcium was significantly higher in the central/eastern part of Europe, but NH4 was slightly higher in western Europe. A highly significant positive correlation of atmospheric deposition and rainfall was observed for most ions. The concentrations of nitrate in soil solution exceeded the EU ground water quality criterion of 800 mmolcm-3 in the subsoil at 9% of the plots. Al/(Ca Mg K) ratios exceeded a critical ratio of 1.0 in approximately 30-39% of the plots, depending on the layer considered. The concentration of potentially toxic Al in the subsoil was strongly related to the concentration of sulphate and nitrate in soils with a base saturation below 25% or a pH below 4.5, indicating that Al release is the dominant buffering process in acid soils. Above a base saturation of 25% and a pH level of 4.5, there was a strong relationship between Ca and strong acid anions, indicating that the acidity is mainly neutralised by the release of base cations in less acidified soils. The variation in concentrations of major ions in the soil solution could be, to a large extent, explained by differences in atmospheric deposition and meteorological conditions.