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  • Moldrup, Per  (206)
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  • 1
    Language: English
    In: Chemosphere, 2011, Vol.83(11), pp.1475-1479
    Description: Photodegradation on dried loamy sand was measured for OTNE and triclosan, and the shading effect was proved to be important and related to soil properties. ► Photodegradation of chemical compounds on dried loamy sand surfaces was measured. ► Photodegradation was not restricted by diffusion in soil but by the shading effect of light. ► The shading effect was quantified from the concentration decrease profile. Fragrances such as OTNE (marketed as Iso-E-Super®) and bactericides such as triclosan (marketed as Igrasan) are present in waste water and thus finally sorbed to sewage sludge. With that sludge they can reach agricultural fields where they potentially can undergo photodegradation processes. In this study the photodegradation of OTNE and triclosan on dried loamy sand was measured under artificial sunlight conditions in laboratory experiments. These compounds were artificially added with concentrations of 1 μg g on pre-rinsed dried loamy sand. The decrease in concentration with light irradiation was measured for 32 d in comparison to soil samples without light irradiation. The estimated light source intensity was 27 W m . Within the experiment, the apparent half-life was 7 and 17 d for OTNE and triclosan respectively. The decrease did not simply follow first-order kinetics. The apparent rate constant decreased in the latter stage of reaction, suggesting that part of the chemicals were inaccessible for degradation. Two models, i.e., a diffusion-limited model, and a light penetration-limited model, were used in comparison to the measured data to explain the observed degradation limitations in the latter stages of the experiments. Comparing the hereby obtained model parameters with estimated physico-chemical parameters for the soil and the two chemical compounds, the light penetration-limited model, in which the degradation in the soil surface layer is assumed to be limited due to the shading effect of light in the upper thin soil layer, showed to be the most realistic in describing the photodegradation.
    Keywords: Otne ; Triclosan ; Soil ; Photodegradation ; Chemistry ; Ecology
    ISSN: 0045-6535
    E-ISSN: 1879-1298
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  • 2
    Language: English
    In: Journal of Hydrology, Oct 10, 2013, Vol.502, p.120(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.08.031 Byline: T.K.K. Chamindu Deepagoda, Jose Choc Chen Lopez, Per Moldrup, Lis Wollesen de Jonge, Markus Tuller Abstract: acents Water and oxygen availability for soilless plant growth substrates were determined. acents Integral water storage and energy concepts were expanded to dual-porosity media. acents An analog integral oxygen diffusivity parameter was introduced. Article History: Received 28 June 2013; Revised 13 August 2013; Accepted 21 August 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of J. A imA[macron]nek, Associate Editor
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Agriculture, Ecosystems and Environment, Sept 15, 2012, Vol.159, p.9(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agee.2012.06.021 Byline: Emmanuel Arthur (a), Per Moldrup (b), Martin Holmstrup (c), Per Schjonning (a), Anne Winding (d), Philipp Mayer (d), Lis W. de Jonge (a) Keywords: Soil contamination; Dehydrogenase activity; Clay dispersibility; Air permeability; Compression; Resilience Abstract: a* Microbial activity decreased significantly at copper concentration [approximately equal to]500mgkg.sup.-1. a* Soil compression resistance had an increasing trend with copper concentration. a* Copper contaminated soils had higher amounts of water dispersible clay. a* Clay dispersibility correlated with microbial activity in a copper contaminated field. Author Affiliation: (a) Department of Agroecology, Faculty of Science and Technology, Aarhus University, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele, Denmark (b) Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark (c) Department of Bioscience, Aarhus University, Vejlsovej 25, DK-8600 Silkeborg, Denmark (d) Department of Environmental Science, Faculty of Science and Technology, Aarhus University. Frederiksborgvej 399, DK-4000 Roskilde, Denmark Article History: Received 23 February 2012; Revised 1 June 2012; Accepted 15 June 2012
    Keywords: Soil Pollution ; Permeability ; Soil Microbiology ; Universities And Colleges
    ISSN: 0167-8809
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Water Research, 01 May 2016, Vol.94, pp.120-127
    Description: Global warming and urbanization together with development of subsurface infrastructures (e.g. subways, shopping complexes, sewage systems, and Ground Source Heat Pump (GSHP) systems) will likely cause a rapid increase in the temperature of relatively shallow groundwater reservoirs (subsurface thermal pollution). However, potential effects of a subsurface temperature change on groundwater quality due to changed physical, chemical, and microbial processes have received little attention. We therefore investigated changes in 34 groundwater quality parameters during a 13-month enhanced-heating period, followed by 14 months of natural or enhanced cooling in a confined marine aquifer at around 17 m depth on the Saitama University campus, Japan. A full-scale GSHP test facility consisting of a 50 m deep U-tube for circulating the heat-carrying fluid and four monitoring wells at 1, 2, 5, and 10 m from the U-tube were installed, and groundwater quality was monitored every 1–2 weeks. Rapid changes in the groundwater level in the area, especially during the summer, prevented accurate analyses of temperature effects using a single-well time series. Instead, Dual-Well Analysis (DWA) was applied, comparing variations in subsurface temperature and groundwater chemical concentrations between the thermally-disturbed well and a non-affected reference well. Using the 1 m distant well (temperature increase up to 7 °C) and the 10 m distant well (non-temperature-affected), the DWA showed an approximately linear relationships for eight components (B, Si, Li, dissolved organic carbon (DOC), Mg , NH , Na , and K ) during the combined 27 months of heating and cooling, suggesting changes in concentration between 4% and 31% for a temperature change of 7 °C.
    Keywords: Subsurface Thermal Pollution ; Ground Source Heat Pump (Gshp) Systems ; Long-Term Heating and Cooling ; Confined Marine Aquifer ; Dual-Well Analysis (Dwa) ; Groundwater Quality ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 5
    Language: English
    In: Journal of Hazardous Materials, 2010, Vol.179(1), pp.573-580
    Description: Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused on the shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16 m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analysed values of essential soil properties. The subsurface of the site was highly layered, resulting in an accumulation of pollution within coarse sandy lenses. Air-filled porosity, readily available phosphorous, and the first-order rate constant ( ) of benzene obtained from slurry biodegradation experiments were found to depend on geologic sample characterization ( 〈 0.05), while inorganic nitrogen was homogenously distributed across the soil stratigraphy. Semivariogram analysis showed a spatial continuity of 4–8.6 m in the vertical direction, while it was 2–5 times greater in the horizontal direction. Values of displayed strong spatial autocorrelation. Even so, the soil potential for biodegradation was highly variable, which from autoregressive state-space modeling was partly explained by changes in soil air-filled porosity and gravimetric water content. The results suggest considering biological heterogeneity when evaluating the fate of contaminants in the subsurface.
    Keywords: Biological Heterogeneity ; Petroleum Vapors ; Spatial Variability ; Semivariogram Analysis ; State-Space Modeling ; Engineering ; Law
    ISSN: 0304-3894
    E-ISSN: 1873-3336
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  • 6
    Language: English
    In: Journal of Hydrology, 2015, Vol.521, p.498(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2014.12.018 Byline: Dan Karup Jensen, Markus Tuller, Lis W. de Jonge, Emmanuel Arthur, Per Moldrup Abstract: * We present a new approach to predict the entire SWC using limited data. * The approach considers capillarity and adsorptive contributions to obtain the SWC. * We obtained accurate prediction of SWC regardless of soil texture. * Clay, silt and organic matter contribute significantly to water adsorption. Article History: Received 23 July 2014; Revised 10 December 2014; Accepted 11 December 2014 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of J. Simunek, Associate Editor
    Keywords: Soil Moisture
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Journal of Hydrology, February 2015, Vol.521, pp.498-507
    Description: The present study proposes a new two-step approach to prediction of the continuous soil water characteristic (SWC) from saturation to oven-dryness from a limited number of measured textural data, organic matter content and dry bulk density. The approach combines dry- and wet-region functions to obtain the entire SWC by means of parameterizing a previously developed continuous equation. The dry region function relates gravimetric soil fractions to adsorptive forces and the corresponding water adsorbed to soil particles. The wet region function converts the volumetric particle size fractions to pore size fractions and utilizes the capillary rise equation to predict water content and matric potential pairs. Twenty-one Arizona source soils with clay and organic carbon contents ranging from 0.01 to 0.52 kg kg and 0 to 0.07 kg kg , respectively, were used for the model development. The SWCs were measured with Tempe cells, a WP4-T Dewpoint Potentiameter, and a water vapor sorption analyzer (VSA). The model was subsequently tested for eight soils from various agricultural fields in Denmark with clay contents ranging from 0.05 to 0.41 kg kg . Test results clearly revealed that the proposed model can adequately predict the SWC based on limited soil data. The advantage of the new model is that it considers both capillary and adsorptive contributions to obtain the SWC from saturation to oven-dryness.
    Keywords: Capillarity ; Adsorption ; Unsaturated Soil ; Water Retention ; Soil Moisture ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 8
    Language: English
    In: Journal of Hydrology, 06 May 2014, Vol.512, pp.388-396
    Description: The saturated hydraulic conductivity ( ) is an essential effective parameter for the development of improved distributed hydrological models and area-differentiated risk assessment of chemical leaching. Basic soil properties such as the particle size distribution or, more recently, air permeability are commonly used to estimate . Conversely, links to soil gas diffusivity ( / ) have not been fully explored even though gas diffusivity is intimately linked to the connectivity and tortuosity of the soil pore network. Based on measurements for a coarse sandy soil, potential relationships between and / were investigated. A total of 84 undisturbed soil cores were extracted from the topsoil of a field site, and / and were measured in the laboratory. Water-induced and solids-induced tortuosity factors were obtained by applying a two-parameter / model to measured data, and subsequently linked to the cementation exponent of the well-established Revil and Cathles predictive model for saturated hydraulic conductivity. Furthermore, a two-parameter model, analogue to the Kozeny–Carman equation, was developed for the − / relationship. All analyses implied strong and fundamental relationships between and / .
    Keywords: Soil Gas Diffusivity ; Tortuosity ; Saturated Hydraulic Conductivity ; Porosity ; Particle Size Distribution ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
    Source: ScienceDirect Journals (Elsevier)
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  • 9
    In: Soil Science Society of America Journal, January 2012, Vol.76(1), pp.51-60
    Description: Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water‐filled pores. The solute diffusivity in intact soil samples from two different tillage treatments (soil from below the depth of a harrow treatment and soil from within a moldboard plowed plow layer) was estimated based on concentration profiles using a newly developed method. The method makes use of multiple tracers (two sets of counterdiffusing tracers) for a better determination of the diffusivity. The diffusivity was higher in the below‐till soil than the plowed soil at the same soil water matric potential due to higher water content but also due to higher continuity and lower tortuosity of the soil pores. We measured identical solute diffusivities independent of the tracer set used. We analyzed the whole data set using Archie's law and found a linear relation between Archie's exponent and the logarithm of the soil water matric suction in centimeters of water (pF). An analysis of seven data sets from the literature showed that this was a general trend for soils with moderate to low clay contents.
    Keywords: Clay ; Data Collection ; Soil Water Content ; Soil Pore System ; Soil Treatment ; Solutes ; Soil Sampling ; Soil Water ; Plowing ; Tracer Techniques ; Plant Growth ; Water Content ; Harrows ; Diffusivity;
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 10
    Language: English
    In: Soil Science Society of America journal, 2012, Vol.76(5), pp.1509-1517
    Description: The gas diffusion coefficient (Ds,g) and solute diffusion coefficient (D(s,l)) and their dependencies on fluid content (κ) (equal to soil–air content θ for D(s,g) and soil–water content ɛ for D(s,l)) are controlling factors for gas and solute transport in variably saturated soils. In this study, we propose unified, predictive models for D(s,g)(ɛ) and D(s,l)(θ) based on modifying and extending the classical Maxwell model at fluid saturation with a fluid-induced reduction term including a percolation threshold (ɛ(th) for D(s,g) and θ(th) for D(s,l)). Different percolation threshold terms adopted from recent studies for gas (D(s,g)) and solute (D(s,l)) diffusion were applied. For gas diffusion, ɛth was a function of bulk density (total porosity), while for solute diffusion θ(th) was best described by volumetric content of finer soil particles (clay and organic matter), FINES(vol). The resulting LIquid and GAs diffusivity and tortuosity (LIGA) models were tested against D(s,g) and D(s,l) data for differently-textured soils and performed well against the measured data across soil types. A sensitivity analysis using the new Maxwell’s Law based LIGA models implied that the liquid phase but not the gaseous-phase tortuosity was controlled by soil type. The analyses also suggested very different pathways and fluid-phase connectivity for gas and solute diffusion in unsaturated soil. In conclusion, the commonly applied strategy of using the same, soil-type-independent model for gas and solute diffusivity in analytical and numerical models for chemical transport and fate in variably-saturated soils appears invalid, except for highly sandy soils. The unified LIGA model with differing percolation thresholds for diffusion in the liquid and gaseous phases solves this problem. ; p. 1509-1517.
    Keywords: Clay ; Sandy Soils ; Bulk Density ; Solutes ; Mathematical Models ; Organic Matter ; Porosity ; Diffusivity
    ISSN: 0361-5995
    E-ISSN: 14350661
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