81 research outputs found
A Fractal Approach to Model Soil Structure and to Calculate Thermal Conductivity of Soils
Heat transport in soils depends on the spatial arrangement of solids, ice, air and water. In this study, we present a modified fractal approach to model the pore structure of soils and to describe its influence on the thermal conductivity. Three different fractal generators were sequentially applied to characterize a wide range of particle- and pore-size distributions. The given porosity and particle-size distribution of a clay, clay loam, silt loam and loamy sand were successfully modeled. The thermal conductivity of the fractal soil model was calculated using a network of resistors. We applied a renormalization approach to include the effects of smaller scale structures. The predictions were compared with the empirical Johansen' model (Johansen, 1975), that postulates a simple linear relationship between ice content and thermal conductivity. For high ice-saturated conditions, the calculated thermal conductivity agrees well with the empirical model. To describe partial ice saturation, we assumed that some pores were coated by ice films enclosing the air-filled center. In addition, we introduced a reduced heat exchange coefficient of the particles for unsaturated conditions. The ice-saturated and -unsaturated thermal conductivity calculated with this approach was very similar to that estimated by the empirical model. The variation of the thermal conductivities for different spatial arrangements of pores and particles in the prefractals were determined. Extreme values deviate more than 50% from the mean value
Evolution of an eruptive flare loop system
<p><b>Context:</b> Flares, eruptive prominences and coronal mass ejections are phenomena where magnetic reconnection plays an important role. However, the location and the rate of the reconnection, as well as the mechanisms of particle interaction with ambient and chromospheric plasma are still unclear.</p>
<p><b>Aims:</b> In order to contribute to the comprehension of the above mentioned processes we studied the evolution of the eruptive flare loop system in an active region where a flare, a prominence eruption and a CME occurred on August 24, 2002.</p>
<p><b>Methods:</b> We measured the rate of expansion of the flare loop arcade using TRACE 195 Ă… images and determined the rising velocity and the evolution of the low and high energy hard X-ray sources using RHESSI data. We also fitted HXR spectra and considered the radio emission at 17 and 34 GHZ.</p>
<p><b>Results:</b> We observed that the top of the eruptive flare loop system initially rises with a linear behavior and then, after 120 mn from the start of the event registered by GOES at 1–8 Å, it slows down. We also observed that the heating source (low energy X-ray) rises faster than the top of the loops at 195 Å and that the high energy X-ray emission (30–40 keV) changes in time, changing from footpoint emission at the very onset of the flare to being coincident during the flare peak with the whole flare loop arcade.</p>
<p><b>Conclusions:</b> The evolution of the loop system and of the X-ray sources allowed us to interpret this event in the framework of the Lin & Forbes model (2000), where the absolute rate of reconnection decreases when the current sheet is located at an altitude where the Alfvén speed decreases with height. We estimated that the lower limit for the altitude of the current sheet is km. Moreover, we interpreted the unusual variation of the high energy HXR emission as a manifestation of the non thermal coronal thick-target process which appears during the flare in a manner consistent with the inferred increase in coronal column density.</p>
Imaging Observations of Quasi-Periodic Pulsatory Non-Thermal Emission in Ribbon Solar Flares
Using RHESSI and some auxiliary observations we examine possible connections
between spatial and temporal morphology of the sources of non-thermal hard
X-ray (HXR) emission which revealed minute quasi-periodic pulsations (QPPs)
during the two-ribbon flares on 2003 May 29 and 2005 January 19. Microwave
emission also reveals the same quasi-periodicity. The sources of non-thermal
HXR emission are situated mainly inside the footpoints of the flare arcade
loops observed by the TRACE and SOHO instruments. At least one of the sources
moves systematically both during the QPP-phase and after it in each flare that
allows to examine the sources velocities and the energy release rate via the
process of magnetic reconnection. The sources move predominantly parallel to
the magnetic inversion line or the appropriate flare ribbon during the
QPP-phase whereas the movement slightly changes to more perpendicular regime
after the QPPs. Each QPP is emitted from its own position. It is also seen that
the velocity and the energy release rate don't correlate well with the flux of
the HXR emission calculated from the sources. The sources of microwaves and
thermal HXRs are situated near the apex of the loop arcade and are not
stationary either. Almost all QPPs and some spikes of HXR emission during the
post-QPP-phase reveal the soft-hard-soft spectral behavior indicating separate
acts of electrons acceleration and injection, rather than modulation of
emission flux by some kinds of magnetohydrodynamic (MHD) oscillations of
coronal loops. In all likelihood, the flare scenarios based on the successively
firing arcade loops are more preferable to interpret the observations, although
we can not conclude exactly what mechanism forces these loops to flare up.Comment: 22 pages, 10 figure
Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers
"This is the peer reviewed version of the following article: Gottselig, N., W. Amelung, J. W. Kirchner, R. Bol, W. Eugster, S. J. Granger, C. Hernández-Crespo, et al. 2017. Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles 31 (10). American Geophysical Union (AGU): 1592 1607. doi:10.1002/2017gb005657, which has been published in final form at https://doi.org/10.1002/2017GB005657. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (similar to 1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 +/- 5% (Si) and 53 +/- 21% (Fe; mean +/- SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe-to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.The authors gratefully acknowledge the assistance of the following people in locating suitable sampling sites, contacting site operators, performing the sampling, and providing data: A. Avila Castells (Autonomous University of Barcelona), R. Batalla (University of Lleida), P. Blomkvist (Swedish University of Agricultural Sciences), H. Bogena (Julich Research Center), A.K. Boulet (University of Aveiro), D. Estany (University of Lleida), F. Garnier (French National Institute of Agricultural Research), H.J. Hendricks-Franssen (Research Center Julich), L. JacksonBlake (James Hutton Institute, NIVA), T. Laurila (Finnish Meteorological Institute), A. Lindroth (Lund University), M.M. Monerris (Universitat Politecnica de Valencia), M. Ottosson Lofvenius (Swedish University of Agricultural Sciences), I. Taberman (Swedish University of Agricultural Sciences), F. Wendland (Research Center Julich), T. Zetterberg (Swedish University of Agricultural Sciences and The Swedish Environmental Research Institute, IVL) and further unnamed contributors. The Swedish Infrastructure for Ecosystem Science (SITES) and the Swedish Integrated Monitoring, the latter financed by the Swedish Environmental Protection Agency, and ICOS Sweden have supported sampling and provided data for the Swedish sites. J.J.K. gratefully acknowledges the support from CESAM (UID/AMB/50017/2013), funded by the FCT/MCTES (PIDDAC) with cofunding by FEDER through COMPETE. N.G. gratefully acknowledges all those who contributed to organizing and implementing the continental sampling. The raw data can be found at http://hdl.handle.net/2128/14937. This project was partly funded by the German Research Foundation (DFG KL2495/1-1).Gottselig, N.; Amelung, W.; Kirchner, J.; Bol, R.; Eugster, W.; Granger, S.; Hernández Crespo, C.... (2017). Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles. 31(10):1592-1607. https://doi.org/10.1002/2017GB005657S159216073110Baken, S., Moens, C., van der Grift, B., & Smolders, E. (2016). Phosphate binding by natural iron-rich colloids in streams. Water Research, 98, 326-333. doi:10.1016/j.watres.2016.04.032Baken, S., Regelink, I. C., Comans, R. N. J., Smolders, E., & Koopmans, G. F. (2016). Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study. Water Research, 99, 83-90. doi:10.1016/j.watres.2016.04.060Benedetti, M. F., Van Riemsdijk, W. H., Koopal, L. K., Kinniburgh, D. G., Gooddy, D. C., & Milne, C. J. (1996). Metal ion binding by natural organic matter: From the model to the field. Geochimica et Cosmochimica Acta, 60(14), 2503-2513. doi:10.1016/0016-7037(96)00113-5Binkley, D., Ice, G. G., Kaye, J., & Williams, C. A. (2004). NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES. Journal of the American Water Resources Association, 40(5), 1277-1291. doi:10.1111/j.1752-1688.2004.tb01586.xBishop, K., Buffam, I., Erlandsson, M., Fölster, J., Laudon, H., Seibert, J., & Temnerud, J. (2008). Aqua Incognita: the unknown headwaters. Hydrological Processes, 22(8), 1239-1242. doi:10.1002/hyp.7049Bol, R., Julich, D., Brödlin, D., Siemens, J., Kaiser, K., Dippold, M. A., … Hagedorn, F. (2016). Dissolved and colloidal phosphorus fluxes in forest ecosystems-an almost blind spot in ecosystem research. Journal of Plant Nutrition and Soil Science, 179(4), 425-438. doi:10.1002/jpln.201600079Buffle, J., & Leppard, G. G. (1995). Characterization of Aquatic Colloids and Macromolecules. 2. Key Role of Physical Structures on Analytical Results. Environmental Science & Technology, 29(9), 2176-2184. doi:10.1021/es00009a005Celi, L., & Barberis, E. (s. f.). Abiotic stabilization of organic phosphorus in the environment. Organic phosphorus in the environment, 113-132. doi:10.1079/9780851998220.0113Dahlqvist, R., Benedetti, M. F., Andersson, K., Turner, D., Larsson, T., Stolpe, B., & Ingri, J. (2004). Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers. Geochimica et Cosmochimica Acta, 68(20), 4059-4075. doi:10.1016/j.gca.2004.04.007Darch, T., Blackwell, M. S. A., Hawkins, J. M. B., Haygarth, P. M., & Chadwick, D. (2014). A Meta-Analysis of Organic and Inorganic Phosphorus in Organic Fertilizers, Soils, and Water: Implications for Water Quality. Critical Reviews in Environmental Science and Technology, 44(19), 2172-2202. doi:10.1080/10643389.2013.790752Dynesius, M., & Nilsson, C. (1994). Fragmentation and Flow Regulation of River Systems in the Northern Third of the World. Science, 266(5186), 753-762. doi:10.1126/science.266.5186.753Erickson, H. P. (2009). Size and Shape of Protein Molecules at the Nanometer Level Determined by Sedimentation, Gel Filtration, and Electron Microscopy. Biological Procedures Online, 11(1), 32-51. doi:10.1007/s12575-009-9008-xEspinosa, M., Turner, B. L., & Haygarth, P. M. (1999). Preconcentration and Separation of Trace Phosphorus Compounds in Soil Leachate. Journal of Environmental Quality, 28(5), 1497-1504. doi:10.2134/jeq1999.00472425002800050015xFernández-MartĂnez, M., Vicca, S., Janssens, I. A., Sardans, J., Luyssaert, S., Campioli, M., … Peñuelas, J. (2014). Nutrient availability as the key regulator of global forest carbon balance. Nature Climate Change, 4(6), 471-476. doi:10.1038/nclimate2177Giddings, J., Yang, F., & Myers, M. (1976). Flow-field-flow fractionation: a versatile new separation method. Science, 193(4259), 1244-1245. doi:10.1126/science.959835Gimbert, L. J., Andrew, K. N., Haygarth, P. M., & Worsfold, P. J. (2003). Environmental applications of flow field-flow fractionation (FIFFF). TrAC Trends in Analytical Chemistry, 22(9), 615-633. doi:10.1016/s0165-9936(03)01103-8Gottselig, N., Bol, R., Nischwitz, V., Vereecken, H., Amelung, W., & Klumpp, E. (2014). Distribution of Phosphorus-Containing Fine Colloids and Nanoparticles in Stream Water of a Forest Catchment. Vadose Zone Journal, 13(7), vzj2014.01.0005. doi:10.2136/vzj2014.01.0005Gottselig, N., Nischwitz, V., Meyn, T., Amelung, W., Bol, R., Halle, C., … Klumpp, E. (2017). Phosphorus Binding to Nanoparticles and Colloids in Forest Stream Waters. Vadose Zone Journal, 16(3), vzj2016.07.0064. doi:10.2136/vzj2016.07.0064Hagedorn , A. G. 2006 EG-Sicherheitsdatenblatt (Gemäß 2001/58/EG)Hart, B. T., Douglas, G. B., Beckett, R., Van Put, A., & Van Grieken, R. E. (1993). Characterization of colloidal and particulate matter transported by the magela creek system, Northern Australia. Hydrological Processes, 7(1), 105-118. doi:10.1002/hyp.3360070111Hassellöv, M., LyvĂ©n, B., Haraldsson, C., & Sirinawin, W. (1999). Determination of Continuous Size and Trace Element Distribution of Colloidal Material in Natural Water by On-Line Coupling of Flow Field-Flow Fractionation with ICPMS. Analytical Chemistry, 71(16), 3497-3502. doi:10.1021/ac981455yHassellov, M., & von der Kammer, F. (2008). Iron Oxides as Geochemical Nanovectors for Metal Transport in Soil-River Systems. Elements, 4(6), 401-406. doi:10.2113/gselements.4.6.401Hens, M., & Merckx, R. (2001). Functional Characterization of Colloidal Phosphorus Species in the Soil Solution of Sandy Soils. Environmental Science & Technology, 35(3), 493-500. doi:10.1021/es0013576Hill, D. M., & Aplin, A. C. (2001). Role of colloids and fine particles in the transport of metals in rivers draining carbonate and silicate terrains. Limnology and Oceanography, 46(2), 331-344. doi:10.4319/lo.2001.46.2.0331Jarvie, H. P., Neal, C., Rowland, A. P., Neal, M., Morris, P. N., Lead, J. R., … Hockenhull, K. (2012). Role of riverine colloids in macronutrient and metal partitioning and transport, along an upland–lowland land-use continuum, under low-flow conditions. Science of The Total Environment, 434, 171-185. doi:10.1016/j.scitotenv.2011.11.061Jiang, X., Bol, R., Nischwitz, V., Siebers, N., Willbold, S., Vereecken, H., … Klumpp, E. (2015). Phosphorus Containing Water Dispersible Nanoparticles in Arable Soil. Journal of Environmental Quality, 44(6), 1772-1781. doi:10.2134/jeq2015.02.0085Kögel-Knabner, I., & Amelung, W. (2014). Dynamics, Chemistry, and Preservation of Organic Matter in Soils. Treatise on Geochemistry, 157-215. doi:10.1016/b978-0-08-095975-7.01012-3Krám, P., Hruška, J., & Shanley, J. B. (2012). Streamwater chemistry in three contrasting monolithologic Czech catchments. Applied Geochemistry, 27(9), 1854-1863. doi:10.1016/j.apgeochem.2012.02.020LyvĂ©n, B., Hassellöv, M., Turner, D. R., Haraldsson, C., & Andersson, K. (2003). Competition between iron- and carbon-based colloidal carriers for trace metals in a freshwater assessed using flow field-flow fractionation coupled to ICPMS. Geochimica et Cosmochimica Acta, 67(20), 3791-3802. doi:10.1016/s0016-7037(03)00087-5Marschner, B., & Kalbitz, K. (2003). Controls of bioavailability and biodegradability of dissolved organic matter in soils. Geoderma, 113(3-4), 211-235. doi:10.1016/s0016-7061(02)00362-2Martin, J.-M., Dai, M.-H., & Cauwet, G. (1995). Significance of colloids in the biogeochemical cycling of organic carbon and trace metals in the Venice Lagoon (Italy). Limnology and Oceanography, 40(1), 119-131. doi:10.4319/lo.1995.40.1.0119Mattsson, T., Kortelainen, P., Laubel, A., Evans, D., Pujo-Pay, M., Räike, A., & Conan, P. (2009). Export of dissolved organic matter in relation to land use along a European climatic gradient. Science of The Total Environment, 407(6), 1967-1976. doi:10.1016/j.scitotenv.2008.11.014Missong, A., Bol, R., Willbold, S., Siemens, J., & Klumpp, E. (2016). Phosphorus forms in forest soil colloids as revealed by liquid-state31P-NMR. Journal of Plant Nutrition and Soil Science, 179(2), 159-167. doi:10.1002/jpln.201500119Montalvo, D., Degryse, F., & McLaughlin, M. J. (2015). Natural Colloidal P and Its Contribution to Plant P Uptake. Environmental Science & Technology, 49(6), 3427-3434. doi:10.1021/es504643fNeubauer, E., Köhler, S. J., von der Kammer, F., Laudon, H., & Hofmann, T. (2013). Effect of pH and Stream Order on Iron and Arsenic Speciation in Boreal Catchments. Environmental Science & Technology, 47(13), 7120-7128. doi:10.1021/es401193jNeubauer, E., v.d. Kammer, F., & Hofmann, T. (2011). Influence of carrier solution ionic strength and injected sample load on retention and recovery of natural nanoparticles using Flow Field-Flow Fractionation. Journal of Chromatography A, 1218(38), 6763-6773. doi:10.1016/j.chroma.2011.07.010Nischwitz, V., & Goenaga-Infante, H. (2012). Improved sample preparation and quality control for the characterisation of titanium dioxide nanoparticles in sunscreens using flow field flow fractionation on-line with inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectrometry, 27(7), 1084. doi:10.1039/c2ja10387gRan, Y., Fu, J. ., Sheng, G. ., Beckett, R., & Hart, B. . (2000). Fractionation and composition of colloidal and suspended particulate materials in rivers. Chemosphere, 41(1-2), 33-43. doi:10.1016/s0045-6535(99)00387-2Regelink, I. C., Koopmans, G. F., van der Salm, C., Weng, L., & van Riemsdijk, W. H. (2013). Characterization of Colloidal Phosphorus Species in Drainage Waters from a Clay Soil Using Asymmetric Flow Field-Flow Fractionation. Journal of Environmental Quality, 42(2), 464-473. doi:10.2134/jeq2012.0322Regelink, I. C., Voegelin, A., Weng, L., Koopmans, G. F., & Comans, R. N. J. (2014). Characterization of Colloidal Fe from Soils Using Field-Flow Fractionation and Fe K-Edge X-ray Absorption Spectroscopy. Environmental Science & Technology, 48(8), 4307-4316. doi:10.1021/es405330xRegelink, I. C., Weng, L., & van Riemsdijk, W. H. (2011). The contribution of organic and mineral colloidal nanoparticles to element transport in a podzol soil. Applied Geochemistry, 26, S241-S244. doi:10.1016/j.apgeochem.2011.03.114RICHARDSON, C. J. (1985). Mechanisms Controlling Phosphorus Retention Capacity in Freshwater Wetlands. Science, 228(4706), 1424-1427. doi:10.1126/science.228.4706.1424Roth , C. 2011 Sicherheitsdatenblatt Gemäß Verordnung (EG) Nr. 1907/2006 RepSchmitt, D., Taylor, H. E., Aiken, G. R., Roth, D. A., & Frimmel, F. H. (2002). Influence of Natural Organic Matter on the Adsorption of Metal Ions onto Clay Minerals. Environmental Science & Technology, 36(13), 2932-2938. doi:10.1021/es010271pSix, J., Elliott, E. T., & Paustian, K. (1999). Aggregate and Soil Organic Matter Dynamics under Conventional and No-Tillage Systems. Soil Science Society of America Journal, 63(5), 1350-1358. doi:10.2136/sssaj1999.6351350xStolpe, B., Guo, L., Shiller, A. M., & Hassellöv, M. (2010). Size and composition of colloidal organic matter and trace elements in the Mississippi River, Pearl River and the northern Gulf of Mexico, as characterized by flow field-flow fractionation. Marine Chemistry, 118(3-4), 119-128. doi:10.1016/j.marchem.2009.11.007Tipping, E., & Hurley, M. . (1992). A unifying model of cation binding by humic substances. Geochimica et Cosmochimica Acta, 56(10), 3627-3641. doi:10.1016/0016-7037(92)90158-fTombácz, E., Libor, Z., IllĂ©s, E., Majzik, A., & Klumpp, E. (2004). The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles. Organic Geochemistry, 35(3), 257-267. doi:10.1016/j.orggeochem.2003.11.002Trostle, K. D., Ray Runyon, J., Pohlmann, M. A., Redfield, S. E., Pelletier, J., McIntosh, J., & Chorover, J. (2016). Colloids and organic matter complexation control trace metal concentration-discharge relationships in Marshall Gulch stream waters. Water Resources Research, 52(10), 7931-7944. doi:10.1002/2016wr019072U.S. Department of Agriculture 1993 Soil survey manual, chapter 3. Selected chemical propertiesVitousek, P. (1982). Nutrient Cycling and Nutrient Use Efficiency. The American Naturalist, 119(4), 553-572. doi:10.1086/283931Wells, M. L., & Goldberg, E. D. (1991). Occurrence of small colloids in sea water. Nature, 353(6342), 342-344. doi:10.1038/353342a0Wen, L.-S., Santschi, P., Gill, G., & Paternostro, C. (1999). Estuarine trace metal distributions in Galveston Bay: importance of colloidal forms in the speciation of the dissolved phase. Marine Chemistry, 63(3-4), 185-212. doi:10.1016/s0304-4203(98)00062-0Zirkler, D., Lang, F., & Kaupenjohann, M. (2012). «Lost in filtration»—The separation of soil colloids from larger particles. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 399, 35-40. doi:10.1016/j.colsurfa.2012.02.02
Current and future role of instrumentation and monitoring in the performance of transport infrastructure slopes
The DZHK research platform: maximisation of scientific value by enabling access to health data and biological samples collected in cardiovascular clinical studies
The German Centre for Cardiovascular Research (DZHK) is one of the German Centres for Health Research and aims to conduct early and guideline-relevant studies to develop new therapies and diagnostics that impact the lives of people with cardiovascular disease. Therefore, DZHK members designed a collaboratively organised and integrated research platform connecting all sites and partners. The overarching objectives of the research platform are the standardisation of prospective data and biological sample collections among all studies and the development of a sustainable centrally standardised storage in compliance with general legal regulations and the FAIR principles. The main elements of the DZHK infrastructure are web-based and central units for data management, LIMS, IDMS, and transfer office, embedded in a framework consisting of the DZHK Use and Access Policy, and the Ethics and Data Protection Concept. This framework is characterised by a modular design allowing a high standardisation across all studies. For studies that require even tighter criteria additional quality levels are defined. In addition, the Public Open Data strategy is an important focus of DZHK. The DZHK operates as one legal entity holding all rights of data and biological sample usage, according to the DZHK Use and Access Policy. All DZHK studies collect a basic set of data and biosamples, accompanied by specific clinical and imaging data and biobanking. The DZHK infrastructure was constructed by scientists with the focus on the needs of scientists conducting clinical studies. Through this, the DZHK enables the interdisciplinary and multiple use of data and biological samples by scientists inside and outside the DZHK. So far, 27 DZHK studies recruited well over 11,200 participants suffering from major cardiovascular disorders such as myocardial infarction or heart failure. Currently, data and samples of five DZHK studies of the DZHK Heart Bank can be applied for
A fractal approach to model soil structure and to calculate thermal conductivities of soils
- …