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  • 1
    Language: English
    In: Environmental science & technology, 20 May 2014, Vol.48(10), pp.5700-8
    Description: Multi-surface models are widely used to assess the potential ecotoxicological risk in metal-contaminated soils. Their accuracy in predicting metal speciation in soils with low metal levels was not yet tested. Now highly sensitive analytical techniques are available to experimentally validate such models at low concentration levels. The objective of this study was to test the accuracy of a multi-surface model to predict the Zn(2+) concentration and to improve our understanding of Zn bioavailability in low-Zn soils. High-Zn soils were included as controls. Model parameters were determined independently on the basis of earlier peer-reviewed publications. Model output was validated against free Zn(2+) concentrations determined with the soil column Donnan membrane technique in a range of soils varying in potentially available Zn, organic matter, clay silicate, and iron (hydr)oxide contents and pH. Deviations between predicted Zn(2+) concentrations and experimentally determined values over the whole Zn concentration range were less or equal to the experimental standard error, except for one low-Zn soil. The Zn(2+) concentration was mainly controlled by adsorption, where organic matter was predicted to be the dominant soil sorbent. The predicted Zn(2+) concentration depends more sensitively upon changes of the reactive Zn pool (application of 0.6, 1.2, 2.4, and 3.6 mg of Zn kg(-1) of soil) and organic matter content (± 0.2 and 0.4%) than pH changes (± 0.5 and 1 pH unit).
    Keywords: Models, Theoretical ; Soil -- Chemistry ; Zinc -- Analysis
    ISSN: 0013936X
    E-ISSN: 1520-5851
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  • 2
    Language: English
    In: Plant and Soil, 12/2014, Vol.385(1-2), pp.395-397
    Description: Erratum to: Plant Soil (2013) 373:919–930 DOI 10.1007/s11104-013-1845-3 There were errors in the presented 0.01 M CaCl2 extracted Zn (second column in Table 2) due to a mistake in the conversion from mass to mol. The molecular weight of Zn (65.38) was wrongly used as 56.38. The correction of this mistake has influence on the fourth column of Table 2, Eq. 6, and Figs. 3, 4 and 5. The corrected values of the table and equation and of the figures are shown below in red. The changes have, however, no influence on the text and conclusion of the paper. Table 2 Zn concentrations in the DTPA and the CaCl2 soil extracts, Zn2 concentrations and the proportion of Zn2+ concentration to the total Zn concentration (means and standard error; n = 3) #Determined with the Donnan Membrane Technique ‡Proportion of Zn2+ concentration to the total Zn concentration in the CaCl2 extract Equation 6: ...
    Keywords: Agriculture ; Botany;
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 3
    Language: English
    In: Plant and Soil, 1 December 2013, Vol.373(1/2), pp.919-930
    Description: Aim Our aim was to improve the prediction of Zn bioavailability to wheat grown on low-Zn soils. The classical approach that directly relates Zn in a certain soil extract to Zn uptake has been shown to be inadequate in many cases. We tested a stepwise approach where the steps of the uptake process are characterized with, respectively, Zn solid-solution distribution, adsorption of Zn to root surface, Zn uptake into root and Zn translocation to shoot. Methods Two pot experiments were done with wheat grown on nine low-Zn soils varying widely in pH, clay and organic matter content. Soluble Zn concentrations in two soil extracts (DTPA and CaCl₂) were measured. Free Zn ion concentrations in CaCl₂ soil extracts were determined with the Donnan Membrane Technique. These Zn concentrations were then related to plant Zn uptake following both the direct and the stepwise approach. Results In the direct approach, Zn in the DTPA extract was a better predictor for shoot Zn uptake than Zn in the CaCl₂ extract. In the stepwise approach, the relationship between Zn in CaCl₂ extracts and the root surface adsorbed Zn was pH-dependent and nonlinear. Root surface adsorbed Zn was linearly related to root Zn uptake, and the latter was linearly related to the shoot Zn uptake. The stepwise approach improved the Zn uptake prediction compared to the direct approach and was also validated for different wheat cultivars. Conclusions The adsorption of Zn on the root surface is pH dependent and nonlinear with respect to the soil Zn concentration, and a useful proxy for bioavailable Zn over a wide range of soils.
    Keywords: Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Biology -- Botany ; Biological sciences -- Biology -- Botany ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Biological sciences -- Agriculture -- Agricultural sciences ; Physical sciences -- Chemistry -- Chemical elements ; Health sciences -- Medical sciences -- Pharmacology ; Physical sciences -- Chemistry -- Chemical reactions
    ISSN: 0032079X
    E-ISSN: 15735036
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  • 4
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(3), p.e91748
    Description: Raised bogs have accumulated more atmospheric carbon than any other terrestrial ecosystem on Earth. Climate-induced expansion of trees and shrubs may turn these ecosystems from net carbon sinks into sources when associated with reduced water tables. Increasing water loss through tree evapotranspiration could potentially deepen water tables, thus stimulating peat decomposition and carbon release. Bridging the gap between modelling and field studies, we conducted a three-year mesocosm experiment subjecting natural bog vegetation to three birch tree densities, and studied the changes in subsurface temperature, water balance components, leaf area index and vegetation composition. We found the deepest water table in mesocosms with low tree density. Mesocosms with high tree density remained wettest (i.e. highest water tables) whereas the control treatment without trees had intermediate water tables. These differences are attributed mostly to differences in evapotranspiration. Although our mesocosm results cannot be directly scaled up to ecosystem level, the systematic effect of tree density suggests that as bogs become colonized by trees, the effect of trees on ecosystem water loss changes with time, with tree transpiration effects of drying becoming increasingly offset by shading effects during the later phases of tree encroachment. These density-dependent effects of trees on water loss have important implications for the structure and functioning of peatbogs.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 5
    Language: English
    In: The New phytologist, July 2014, Vol.203(1), pp.70-80
    Description: Northern peatlands represent a large global carbon store that can potentially be destabilized by summer water table drawdown. Precipitation can moderate the negative impacts of water table drawdown by rewetting peatmoss (Sphagnum spp.), the ecosystem's key species. Yet, the frequency of such rewetting required for it to be effective remains unknown. We experimentally assessed the importance of precipitation frequency for Sphagnum water supply and carbon uptake during a stepwise decrease in water tables in a growth chamber. CO2 exchange and the water balance were measured for intact cores of three peatmoss species (Sphagnum majus, Sphagnum balticum and Sphagnum fuscum) representative of three hydrologically distinct peatland microhabitats (hollow, lawn and hummock) and expected to differ in their water table-precipitation relationships. Precipitation contributed significantly to peatmoss water supply when the water table was deep, demonstrating the importance of precipitation during drought. The ability to exploit transient resources was species-specific; S. fuscum carbon uptake increased linearly with precipitation frequency for deep water tables, whereas carbon uptake by S. balticum and S. majus was depressed at intermediate precipitation frequencies. Our results highlight an important role for precipitation in carbon uptake by peatmosses. Yet, the potential to moderate the impact of drought is species-specific and dependent on the temporal distribution of precipitation.
    Keywords: Sphagnum Physiology ; Climate Change ; Desiccation Tolerance ; Mires ; Moisture Stress ; Photosynthesis ; Rain Variability ; Water Balance ; Carbon Cycle ; Droughts ; Sphagnopsida -- Metabolism ; Water -- Physiology
    ISSN: 0028646X
    E-ISSN: 1469-8137
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  • 6
    Language: English
    In: Global change biology, June 2015, Vol.21(6), pp.2309-20
    Description: Boreal peatlands store large amounts of carbon, reflecting their important role in the global carbon cycle. The short-term exchange and the long-term storage of atmospheric carbon dioxide (CO2 ) in these ecosystems are closely associated with the permanently wet surface conditions and are susceptible to drought. Especially, the single most important peat forming plant genus, Sphagnum, depends heavily on surface wetness for its primary production. Changes in rainfall patterns are expected to affect surface wetness, but how this transient rewetting affects net ecosystem exchange of CO2 (NEE) remains unknown. This study explores how the timing and characteristics of rain events during photosynthetic active periods, that is daytime, affect peatland NEE and whether rain event associated changes in environmental conditions modify this response (e.g. water table, radiation, vapour pressure deficit, temperature). We analysed an 11-year time series of half-hourly eddy covariance and meteorological measurements from Degerö Stormyr, a boreal peatland in northern Sweden. Our results show that daytime rain events systematically decreased the sink strength of peatlands for atmospheric CO2 . The decrease was best explained by rain associated reduction in light, rather than by rain characteristics or drought length. An average daytime growing season rain event reduced net ecosystem CO2 uptake by 0.23-0.54 gC m(-2) . On an annual basis, this reduction of net CO2 uptake corresponds to 24% of the annual net CO2 uptake (NEE) of the study site, equivalent to a 4.4% reduction of gross primary production (GPP) during the growing season. We conclude that reduced light availability associated with rain events is more important in explaining the NEE response to rain events than rain characteristics and changes in water availability. This suggests that peatland CO2 uptake is highly sensitive to changes in cloud cover formation and to altered rainfall regimes, a process hitherto largely ignored.
    Keywords: Sphagnum ; Climate Change ; Cloud Cover ; Drought ; Ecosystem Primary Productivity ; Eddy Covariance ; Peatlands ; Precipitation ; Rain ; Sunlight ; Carbon Dioxide -- Metabolism ; Sphagnopsida -- Metabolism
    ISSN: 13541013
    E-ISSN: 1365-2486
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  • 7
    Language: English
    In: Environmental science & technology, 15 September 2005, Vol.39(18), pp.7176-84
    Description: The aim of this study is to predict the solid-solution partitioning of heavy metals in river flood plain soils. We compared mechanistic geochemical modeling with a statistical approach. To characterize the heavy metal contamination of embanked river flood plain soils in The Netherlands, we collected 194 soil samples at 133 sites distributed in the Dutch part of the Rhine and Meuse river systems. We measured the total amounts of As, Cd, Cr, Cu, Ni, Pb, and Zn in the soil samples and the metal fraction extractable by 2.5 mM CaCl2. We found a strong correlation between heavy metal contamination and organic matter content, which was almost identical for both river systems. Speciation calculations by a fully parametrized model showed the strengths and weaknesses of the mechanistic approach. Cu and Cd concentrations were predicted within one log scale, whereas modeling of Zn and Pb needs adjustment of some model parameters. The statistical fitting approach produced better results but is limited with regard to the understanding it provides. The log RMSE for this approach varied between 0.2 and 0.32 for the different metals. The careful modeling of speciation and adsorption processes is a useful tool for the investigation and understanding of metal availability in river flood plain soils.
    Keywords: Arsenic -- Analysis ; Environmental Monitoring -- Methods ; Metals, Heavy -- Analysis ; Soil -- Analysis ; Soil Pollutants -- Analysis ; Water Pollutants -- Analysis
    ISSN: 0013-936X
    E-ISSN: 15205851
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  • 8
    In: Environmental Science & Technology, April, 1997, Vol.31(4), p.1109(7)
    Description: The mobility of copper in copper-contaminated soils is sensitive to pH and calcium concentration in a medium where dissolved organic material is present. The experiment was conducted to enable the modeling of copper mobility under the non-ideal competitive adsorption (NICA) model. This would enable researchers to predict copper concentrations using soil copper content, pH and solid/dissolved organic materials concentration as parameters.
    Keywords: Soil Chemistry -- Environmental Aspects ; Copper (Metal) -- Environmental Aspects ; Hazardous Wastes -- Control ; Absorption -- Research ; Soil Science -- Research ; Pollution Control Research
    ISSN: 0013-936X
    E-ISSN: 15205851
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  • 9
    Language: English
    In: Environmental science and pollution research international, 2014, Vol.21(15), pp.8897-913
    Description: This paper gives an overview of management considerations required for better control of deicing chemicals in the unsaturated zone at sites with winter maintenance operations in cold regions. Degradable organic deicing chemicals are the main focus. The importance of the heterogeneity of both the infiltration process, due to frozen ground and snow melt including the contact between the melting snow cover and the soil, and unsaturated flow is emphasised. In this paper, the applicability of geophysical methods for characterising soil heterogeneity is considered, aimed at modelling and monitoring changes in contamination. To deal with heterogeneity, a stochastic modelling framework may be appropriate, emphasizing the more robust spatial and temporal moments. Examples of a combination of different field techniques for measuring subsoil properties and monitoring contaminants and integration through transport modelling are provided by the SoilCAM project and previous work. Commonly, the results of flow and contaminant fate modelling are quite detailed and complex and require post-processing before communication and advising stakeholders. The managers' perspectives with respect to monitoring strategies and challenges still unresolved have been analysed with basis in experience with research collaboration with one of the case study sites, Oslo airport, Gardermoen, Norway. Both scientific challenges of monitoring subsoil contaminants in cold regions and the effective interaction between investigators and management are illustrated.
    Keywords: Cold Temperature ; Models, Theoretical ; Organic Chemicals ; Environmental Pollution -- Prevention & Control
    ISSN: 09441344
    E-ISSN: 1614-7499
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  • 10
    Language: English
    In: Environmental science and pollution research international, 2014, Vol.21(15), pp.8893-6
    Description: Previously, conventional techniques for characterizing contaminated sites were often applied with limited strategic planning, resulting in time-consuming and cost-intensive investigation campaigns, which did not effectively support decision-making. The need for remediation, and the optimal way of doing so in terms of environmental beneficial effect and cost effectiveness, involves problem owners, the authorities, and consultants. Each of these stakeholders has to deal with lack of knowledge and broad-bands of uncertainty regarding subsurface contaminant distribution and processes. The primary cause is the spatiotemporal variability both of the subsurface, its structure and processes such as flow, transport, and biodegradation, and the pollution event. This variability leads to highly erratic patterns of contaminant concentrations, which cannot be captured experimentally with conventional techniques that provide point measurements. An obvious solution to deal with the ‘invisible subsoil ...
    Keywords: Environmental Monitoring ; Soil Pollutants -- Analysis
    ISSN: 09441344
    E-ISSN: 1614-7499
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