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  • 1
    Language: English
    In: Water, Air, & Soil Pollution, 2014, Vol.225(9), pp.1-13
    Description: Biochar, a by-product resulting from the pyrolysis of biomass, is considered to be an anthropogenic carbonaceous sorbent. Despite a worldwide increase in the application of biochar on agricultural fields to improve crop productivity over the past few decades, there have been few studies on their influences on the sorption of environmental contaminants. In a field-based study at two experimental sites in Denmark, we investigated the effect of birch wood-derived biochar ( Skogans kol ) on the sorption of phenanthrene in soils with different properties. The soil sorption coefficient, K d (L kg −1 ), of phenanthrene was measured on sandy loam and loamy sand soils which have received from zero up to 100 t ha −1 of biochar. Results show that birch wood biochar had a higher K d compared to soils. Furthermore, the application of birch wood biochar enhanced the sorption of phenanthrene in agricultural soils, and the enhancement effect increased with an increasing biochar application rate. Aging, repeated application, and higher clay content suppressed the biochar enhancement effect on the sorption of phenanthrene. Phenanthrene K d was found to be strongly and positively correlated with both total and non-complexed organic carbon, while negatively correlated with clay content. The results also revealed that biochar–mineral interactions play an important role in the sorption of phenanthrene in biochar-amended soil.
    Keywords: Phenanthrene ; Biochar ; Sorption ; Organic carbon
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 2
    Language: English
    In: Environmental Earth Sciences, 2016, Vol.75(7), pp.1-9
    Description: Effects of soil temperature on the solute diffusion process in soils are important since subsurface temperature variation affects solute transport such as a fertilizer movement, leaching of salt, and pollutant movement to groundwater aquifers. However, the temperature dependency on the solute diffusion process in soils has been poorly understood and rarely documented. In this study, solute diffusion experiments as well as equilibrium adsorption experiments using pure kaolin clay were conducted under different temperature conditions. The experiments of K + adsorption on kaolin clay showed more enhanced adsorption of K + at elevated temperature likely because surface charge characteristics were affected at different temperature conditions for the kaolin clay. The temperature dependent solute diffusion showed that the solute diffusion coefficient at 40 °C was around two times higher than that at 6 °C for Cl − and K + . Overall, Arrhenius equation describing temperature dependent solute diffusion was applicable for both ions in samples at different bulk densities. At 40 °C, the liquid-phase impedance factor decreased, while liquid-phase pore-network tortuosity increased, suggesting changes in chemical surface activity towards the solute or pore structure changes of the clay fabric at the elevated temperature.
    Keywords: Temperature effect ; Solute diffusion ; Kaolin clay ; Adsorption
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 3
    Language: English
    In: Biology and Fertility of Soils, 2014, Vol.50(7), pp.1087-1097
    Description: Biochar added to agricultural soils may sequester carbon and improve physico-chemical conditions for crop growth, due to effects such as increased water and nutrient retention in the root zone. The effects of biochar on soil microbiological properties are less certain. We addressed the effects of wood-based biochar on soil respiration, water contents, potential ammonia oxidation (PAO), arylsulfatase activity (ASA), and crop yields at two temperate sandy loam soils under realistic field conditions. In situ soil respiration, PAO, and ASA were not significantly different in quadruplicate field plots with or without biochar (20 Mg ha −1 ); however, in the same plots, volumetric water contents increased by 7.5 % due to biochar ( P  = 0.007). Crop yields (oat) were not significantly different in the first year after biochar application, but in the second year, total yields of spring barley increased by 11 % ( P  〈 0.001), though the increase in grain yield was not significant. Field plots with cumulative biochar rates of up to 100 Mg ha −1 , applied during two consecutive years, substantiated that biochar was not inhibitory to PAO and ASA as reference plots consistently showed lowest activities. For PAO, it was found that soil pH, rather than biochar rates, was a driving environmental variable. For ASA, the methodological approach was challenged by product sorption, but results did not suggest that biochar significantly stimulated the enzyme activity. Crop yields of maize in field experiments with 10–100 Mg biochar ha −1 were unaffected by biochar except for a negative effect of the highest annual rates of 50 Mg ha −1 in the first year after application. In conclusion, the present wood-based biochar poorly affected the measured microbial processes and generally resulted in similar crop yields in reference and biochar-amended soil plots.
    Keywords: Arylsulfatase ; Biochar ; Crop yield ; Nitrification ; Respiration ; Soil enzyme
    ISSN: 0178-2762
    E-ISSN: 1432-0789
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  • 4
    Language: English
    In: Water, Air, & Soil Pollution, 2015, Vol.226(8), pp.1-13
    Description: The large spatial heterogeneity in soil physico-chemical and microbial parameters challenges our ability to predict and model pesticide leaching from agricultural land. Microbial mineralization of pesticides is an important process with respect to pesticide leaching since mineralization is the major process for the complete degradation of pesticides without generation of metabolites. The aim of our study was to determine field-scale variation in the potential for mineralization of the herbicides glyphosate, bromoxyniloctanoate, diflufenican, and bentazone and to investigate whether this variation can be predicted by variations in basic soil parameters. Sixty-five soil samples were sampled from an agricultural, loamy field in Silstrup, Denmark, from a 60 × 165 m rectangular grid. The mineralization potential of the four pesticides was determined using a 96-well microplate 14 C-radiorespirometric method. Initial mineralization rates were determined using first-order kinetics for glyphosate and bromoxyniloctanoate and zero-order kinetics for diflufenican and bentazone. The mineralization rates of the four pesticides varied between the different pesticides and the different soil samples, but we could not establish correlations between the pesticide mineralization rates and the measured soil parameters. Only the glyphosate mineralization rates showed slightly increasing mineralization potentials towards the northern area of the field, with increasing clay and decreasing OC contents. The mineralization potentials for glyphosate and bentazone were compared with 9-years leaching data from two horizontal wells 3.5 m below the field. The field-scale leaching patterns, however, could not be explained by the pesticide mineralization data. Instead, field-scale pesticide leaching may have been governed by soil structure and preferential flow events.
    Keywords: Field-scale variation ; Pesticide mineralization ; Soil characterization ; Correlation analysis ; Pesticide leaching
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 5
    Language: English
    In: Water, Air, & Soil Pollution, 2015, Vol.226(3), pp.1-13
    Description: Sorption is commonly agreed to be the major process underlying the transport and fate of polycyclic aromatic hydrocarbons (PAHs) in soils. However, there is still a scarcity of studies focusing on spatial variability at the field scale in particular. In order to investigate the variation in the field of phenanthrene sorption, bulk topsoil samples were taken in a 15 × 15-m grid from the plough layer in two sandy loam fields with different texture and organic carbon (OC) contents (140 samples in total). Batch experiments were performed using the adsorption method. Values for the partition coefficient K d (L kg −1 ) and the organic carbon partition coefficient K OC (L kg −1 ) agreed with the most frequently used models for PAH partitioning, as OC revealed a higher affinity for sorption. More complex models using different OC compartments, such as non-complexed organic carbon (NCOC) and complexed organic carbon (COC) separately, performed better than single K OC models, particularly for a subset including samples with Dexter n  〈 10 and OC 〈0.04 kg kg −1 . The selected threshold revealed that K OC -based models proved to be applicable for more organic fields, while two-component models proved to be more accurate for the prediction of K d and retardation factor ( R ) for less organic soils. Moreover, OC did not fully reflect the changes in phenanthrene retardation in the field with lower OC content (Faardrup). Bulk density and available water content influenced the phenanthrene transport mechanism phenomenon.
    Keywords: Sorption ; Soil organic carbon ; Complexed organic carbon ; Non-complexed organic carbon ; Phenanthrene ; Field-scale ; Leaching risk
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 6
    Language: English
    In: Water, Air, & Soil Pollution, 2016, Vol.227(6), pp.1-12
    Description: Despite a contemporary interest in biochar application to agricultural fields to improve soil quality and long-term carbon sequestration, a number of potential side effects of biochar incorporation in field soils remain poorly understood, e.g., in relation to interactions with agrochemicals such as pesticides. In a field-based study at two experimental sites in Denmark (sandy loam soils at Risoe and Kalundborg), we investigated the influence of birch wood biochar with respect to application rate, aging (7–19 months), and physicochemical soil properties on the sorption coefficient, K d (L kg −1 ), of the herbicide glyphosate. We measured K d in equilibrium batch sorption experiments with triplicate soil samples from 20 field plots that received biochar at different application rates (0 to 100 Mg ha −1 ). The results showed that pure biochar had a lower glyphosate K d value as compared to soils. Yet, at the Kalundborg soils, the application of biochar enhanced the sorption of glyphosate when tested after 7–19 months of soil–biochar interaction. The relative enhancement effect on glyphosate sorption diminished with increasing biochar application rate, presumably due to increased mineral–biochar interactions. In the Risoe soils, potential biochar effects on glyphosate sorption were affected by a distinct gradient in soil pH (7.4 to 8.3) and electrical conductivity (0.40–0.90 mS cm −1 ) resulting from a natural CaCO 3 gradient. Thus, glyphosate K d showed strong linear correlation with pH and EC. In conclusion, the results show that biochar, despite initially being a poor sorbent for glyphosate, can increase glyphosate sorption in soil. However, the effect of biochar on glyphosate sorption is depends on prevailing soil physicochemical properties.
    Keywords: Biochar ; Glyphosate ; Sorption ; Soil properties
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 7
    Language: English
    In: Environmental Earth Sciences, 2015, Vol.74(7), pp.5525-5539
    Description: Capillary barrier cover systems (CBCSs) are useful and low-cost earthen cover systems for preventing water infiltration and controlling seepage at solid waste landfills. A possible technique to enhance the impermeable properties of CBCSs is to make water repellent grains by mixing the earthen cover material with a hydrophobic agent (HA). In this study, six different grains with different geometries and sizes were used to prepare dry hydrophobized grains by mixing with different contents of oleic acid as a HA. Wet hydrophobized grains were prepared by adjusting the water content ( θ g ; kg kg −1 ) of dry hydrophobized grains. To characterize the water repellency (WR) of dry and wet hydrophobized grains, initial solid-water contact angles ( α i ) were measured using the sessile drop method (SDM). Based on SDM results from the α i –HA content and α i – θ g curves, useful WR indices were introduced as “Area_ dry ” and “Area_ wet ” (areas under the α i –HA content and α i – θ g curves, respectively), “HA_ zica ” and “θ g_zica ” (maximum HA content and θ g at which WR disappears, respectively), and “α i,peak ” and “HA_ αi,peak ” (peak α i in the α i –HA content curve and corresponding HA content to α i,peak , respectively). Pearson correlation analysis was performed to identify correlations between proposed WR indices and basic grain properties. Results showed that WR indices correlated well to d 50 and coefficient of uniformity ( C u ) and regression equations for WR indices were obtained as functions of d 50 and C u ( r 2  〉 0.7).
    Keywords: Water repellency ; Hydrophobized grains ; Capillary barrier cover system ; Grain size
    ISSN: 1866-6280
    E-ISSN: 1866-6299
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  • 8
    Language: English
    In: Water, Air, & Soil Pollution, 2013, Vol.224(4), pp.1-11
    Description: Polyaromatic hydrocarbon (PAH) sorption to soil is a key process deciding the transport and fate of PAH, and potential toxic impacts in the soil and groundwater ecosystems, for example in connection with atmospheric PAH deposition on soils. There are numerous studies on PAH sorption in relatively low organic porous media such as urban soils and groundwater sediments, but less attention has been given to cultivated soils. In this study, the phenanthrene partition coefficient, K D (liter per kilogram), was measured on 143 cultivated Danish soils (115 topsoils, 0–0.25-m soil depth and 28 subsoils, 0.25–1-m depth) by the single-point adsorption method. The organic carbon partition coefficient, K OC (liter per kilogram) for topsoils was found generally to fall between the K OC values estimated by the two most frequently used models for PAH partitioning, the Abdul et al. (Hazardous Waste & Hazardous Materials 4(3):211–222, 1987) model and Karickhoff et al. (Water Research 13:241–248, 1979) model. A less-recognized model by Karickhoff (Chemosphere 10:833–846, 1981), yielding a K OC of 14,918 L kg −1 , closely corresponded to the average measured K OC value for the topsoils, and this model is therefore recommended for prediction of phenanthrene mobility in cultivated topsoils. For lower subsoils (0.25–1-m depth), the K OC values were closer to and mostly below the estimate by the Abdul et al. (Hazardous Waste & Hazardous Materials 4(3):211–222, 1987) model. This implies a different organic matter composition and higher PAH sorption strength in cultivated topsoils, likely due to management effects including more rapid carbon turnover. Finally, we applied the recent Dexter et al. (Geoderma 144:620–627, 2008) theorem, and calculated the complexed organic carbon and non-complexed organic carbon fractions (COC and NCOC, grams per gram). Multiple regression analyses showed that the NCOC-based phenanthrene partition coefficient ( K NCOC ) could be markedly higher than the COC-based partition coefficient ( K COC ) for soils with a clay/OC ratio 〈10. This possibly higher PAH sorption affinity to the NCOC fraction needs further investigations to develop more realistic and accurate models for PAH mobility and effects in the environment, also with regard to colloid-facilitated PAH transport.
    Keywords: Phenanthrene ; PAH ; Sorption ; Organic carbon ; Agricultural soils
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 9
    Language: English
    In: Water, Air, & Soil Pollution, 2017, Vol.228(1), pp.1-12
    Description: Soil texture and soil organic carbon (OC) influence the bacterial microenvironment and also control herbicide sorption. A field-scale exploratory study was conducted to investigate the potential interaction between soil texture parameters, herbicides, and soil bacterial richness and diversity. Glyphosate and bentazon were used to evaluate the herbicidal effect on bacterial community under different conditions created by clay and OC gradients in a loamy field. Metabarcoding by high-throughput sequencing of bacterial rDNA was used to estimate bacterial richness and diversity using OTUs, abundance-based coverage (ACE), Shannon diversity index, and phylogenetic diversity. In general, bacterial richness and diversity increased after bentazon application and decreased after glyphosate application. There was no significant effect for field locations with Dexter n (the ratio between clay and OC) values below 4.04 (the median of the values in the field study). The correlation coefficient ( r ) between bacterial richness and clay decreased after bentazon application, but increased after glyphosate application. Correlations between Dexter n and bacterial indices followed the same pattern, decreasing after bentazon application and increasing after glyphosate application. This indicated that the specific chemical nature of individual herbicides affected bacterial communities. This study reinforced the importance of including soil physical and chemical characteristics to explain the influence of pesticides on the variation in soil bacterial communities in agroecosystems.
    Keywords: Bentazon ; Glyphosate ; ACE ; Shannon ; Soil texture ; Metabarcoding
    ISSN: 0049-6979
    E-ISSN: 1573-2932
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  • 10
    Language: English
    In: International Journal on Digital Libraries, 2015, Vol.16(3-4), p.267(16)
    Description: Byline: Bolette Ammitzboll Jurik (1), Asger Askov Blekinge (1), Rune Bruun Ferneke-Nielsen (1), Per Moldrup-Dalum (1) Keywords: Digital preservation; Digital repository; Preservation action; Preservation policies; Scalability; Integration; File characterisation; JPEG 2000; Apache Hadoop Abstract: Integrating large-scale processing environments, such as Hadoop, with traditional repository systems, such as Fedora Commons 3, has long proved to be a daunting task. In this paper, we will show how this integration can be achieved using software developed in the scalable preservation environments (SCAPE) project, and also how it can be achieved using a local more direct implementation at the Danish State and University Library inspired by the SCAPE project. Both allow full use of the Hadoop system for massively distributed processing without causing excessive load on the repository. We present a proof of concept SCAPE integration and an in-production local integration based on repository systems at the Danish State and University Library and the Hadoop execution environment. Both use data from the Newspaper Digitisation Project, a collection that will grow to more than 32 million JP2 images. The use case for the SCAPE integration is to perform feature extraction and validation of the JP2 images. The validation is done against an institutional preservation policy expressed in the machine readable SCAPE Control Policy vocabulary. The feature extraction is done using the Jpylyzer tool. We perform an experiment with various-sized sets of JP2 images, to test the scalability and correctness of the solution. The first use case considered from the local Danish State and University Library integration is also feature extraction and validation of the JP2 images, this time using Jpylyzer and Schematron requirements translated from the project specification by hand. We further look at two other use cases: generation of histograms of the tonal distributions of the images and generation of dissemination copies. We discuss the challenges and benefits of the two integration approaches when having to perform preservation actions on massive collections stored in traditional digital repositories. Author Affiliation: (1) State and University Library, Victor Albecks Vej 1, 8000, Aarhus C, Denmark Article History: Registration Date: 09/05/2015 Received Date: 02/12/2014 Accepted Date: 10/05/2015 Online Date: 29/05/2015 Article note: This work was partially supported by the SCAPE Project. The SCAPE project is co-funded by the European Union under FP7 ICT-2009.4.1 (Grant Agreement number 270137).
    Keywords: Library & Information Science;
    ISSN: 1432-5012
    E-ISSN: 14321300
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