Mobility and Transport of Nd Isotopes in the Vadose Zone During Weathering of Granitic Till in a Boreal Forest     

Björn Öhlander  Magnus Land  Johan Ingri  Anders Widerlund 《Aquatic Geochemistry》2014,20(1):1-17

There is a broad correlation between the ε_Nd values for rivers (including both the water and the particulate material it carries) and the age of the source terrain. This paper presents Nd isotope distribution data for soil, soil water, groundwater, and stream water samples gathered in a small catchment in northern Sweden. The results show that the release of Nd and Sm from boreal forests into streams and, eventually, into the oceans is more complicated than previously realized. The weathering of till causes changes in both the Nd isotopic composition and Sm/Nd ratios. Both the Sm/Nd ratio and ε_Nd were higher in strongly weathered soils horizons than in less weathered till, since minerals with high Sm/Nd ratios were, on average, more resistant to weathering than those with low Sm/Nd ratios. In contrast to the situation for the main minerals and the major elements, the weathering of rare earth elements (REE) was not restricted to the E-horizon: the measured REE concentrations continued to increase with depth in the C-horizon. In addition, REE released by weathering in the upper parts of the soil profile were partly secondarily retained at deeper levels. Therefore, the dissolved Nd released by weathering in the upper soil horizons was trapped and did not enter the groundwater directly. Rather, the Nd in the groundwater largely originated from weathering within the groundwater zone. However, this was not the only source of Nd in the stream water. The Nd isotope composition and Sm/Nd ratio were determined by the mixing between of Nd and Sm in the groundwater and REE-carrying organic material washed out of the soil profile. The groundwater close to the stream reaches the upper soil horizons during high discharge events such as snowmelts, and organic matter carrying Nd and Sm is washed out of the soils and thus released into the stream. Therefore, the Nd exported from catchment is derived from both the weathering within the groundwater zone, and the organic matter washed out from the soil. If longer timescales with more advanced weathering stages in the groundwater zone are considered, it cannot be ruled out that there will be a shift towards more radiogenic values in the exported Nd. Recorded shifts in the Nd isotopic composition in the ocean may thus not only reflect changed source regions, but also the weathering history of the same source region.  相似文献   

Towards Better WMS Maps Through the Use of the Styled Layer Descriptor and Cartographic Conflict Resolution for Linear Features     

Ionuţ Iosifescu Enescu  Nadia H. Panchaud  Magnus Heitzler  Cristina M. Iosifescu Enescu  Lorenz Hurni 《The Cartographic journal》2013,50(2):125-136

Abstract

Mercator depicted Croatia on several general maps. In accordance with the level of geographical knowledge, map scales and technical possibilities of the time, Mercator provided a relatively detailed depiction of basic geographical features on these maps. His interest in mapping Croatia was probably motivated by the fact that the Venetian Republic, the Habsburg Monarchy and the Ottoman Empire had fought over this area in the sixteenth century, contributing to the fragmentation of the medieval Croatian State, while at the same time facilitating economic, religious, linguistic, artistic and scientific communication between Central, South East and Mediterranean Europe. Mercator paid special attention to toponyms that enabled geographical objects to be identified and the decoding of cartographic contents. Research into Mercator’s maps has shown that geographical names, among other things, clearly indicate the sources of spatial data that he used. Additionally, geographical names on Mercator’s maps are significant indicators of the linguistic and cultural contacts that were particularly prominent in border areas, for example, along the eastern Adriatic coast, or the courses of the Danube, Sava and Drava.  相似文献   

Effects of hysteresis,rainfall dynamics,and temporal resolution of rainfall input data in solute transport modelling in uncropped soil     

Magnus Persson  Alan Saifadeen 《水文科学杂志》2013,58(5):982-990

  相似文献   

Groundwater contamination risks from conservative point source pollutants in a future climate     

Magnus Persson  Tarek Selim  Jonas Olsson 《水文科学杂志》2013,58(13):1659-1671

ABSTRACT

The groundwater contamination risk in future climates was investigated at three locations in Sweden. Solute transport penetration depths were simulated using the HYDRUS-1D model using historical data and an ensemble of climate projections including two global climate models (GCMs), three emission scenarios and one regional climate model. Most projections indicated increasing precipitation and evapotranspiration until mid-century with a further increase at end-century. Results showed both increasing and decreasing groundwater contamination risks depending on emission scenario and GCM. Generally, the groundwater contamination risk is likely to be unchanged until mid-century, but higher at the end of the century. Soil and site specific relationships between Δ(P – PET) (i.e. change in the difference between precipitation, P, and potential evapotranspiration, PET) and changes in solute transport depths were determined. Using this, changes in solute transport depths for other climate projections can be assessed.  相似文献   

Contracts for Contentious Politics: Day Labor Hall Practices and the City of Cincinnati     

Colleen McTague  Per Jansen 《Urban geography》2013,34(4):474-495

Using an empirical study of a political protest, this paper examines a set of interdependent contracts symbolizing both the nodes of scalar interaction and the hegemonic nodes of resistance. The study focuses on a contentious political campaign aimed at the City of Cincinnati, a recycling facility, and a day labor temp agency initiated by contracted day laborers who hand-sorted garbage from recycling materials and suffered from adverse working conditions and alleged wage violations. A discussion of the rise of contingent labor through implementation of neoliberal deregulation policies is integrated with Jürgen Habermas' concepts of the lifeworld and the system providing an explanatory framework for understanding lifeworld colonization through flexible labor practices and the subsequent impetus behind the contentious political campaign. Using survey data, the shared lifeworld of day laborers is described. The study also examines how the position of protest participants affected the tactics and outcomes of the contestation. [Key words: day labor, contingent labor, living wage ordinances, Habermas.]  相似文献   

Research on geographical education     

Jan Ketil Rød  Per Jarle Sætre  Michael Jones 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):117-119

  相似文献   

Fault displacement modelling using 3D vector fields     

Frode Georgsen  Per R?e  Anne Randi Syversveen  Oddvar Lia 《Computational Geosciences》2012,16(2):247-259

In history matching and sensitivity analysis, flexibility in the structural modelling is of great importance. The ability to easily generate multiple realizations of the model will have impact both on the updating workflow in history matching and uncertainty studies based on Monte Carlo simulations. The main contribution to fault modelling by the work presented in this paper is a new algorithm for calculating a 3D displacement field applicable to a wide range of faults due to a flexible representation. This gives the possibility to apply this field to change the displacement and thereby moving horizons and fault lines. The fault is modelled by a parametric format where the fault has a reference plane defined by a centre point, dip and strike angles. The fault itself is represented as a surface defined by a function z = f(x,y), where x, y and z are coordinates local to the reference plane, with the z-axis being normal to the plane. The displacement associated with the fault outside the fault surface is described by a 3D vector field. The displacement on the fault surface can be found by identifying the intersection lines between horizons and the fault surface (fault lines), and using kriging techniques to fill in values at all points on the surface. Away from the fault surface the displacement field is defined by a monotonic decreasing function which ensures zero displacement at a specified distance from the fault. An algorithm is developed where the displacement can be increased or decreased according to user-defined parameters. This means that the whole displacement field is changed and points on horizons around the fault can be moved accordingly by applying the modified displacement field on them. The interaction between several faults influencing the same points is taken care of by truncation rules and the ordering of the faults. The method is demonstrated on a realistic synthetic case based on a real reservoir.  相似文献   

Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic   总被引：1，自引：0，他引：1  

Rina Argelia Andersson  Philip Meyers  Edward Hornibrook  Peter Kuhry  Carl‐Magnus Mörth 《第四纪科学杂志》2012,27(6):545-552

A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (～2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss‐dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water‐saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. δ¹⁵N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in δ¹³C values appear to reflect mainly changes in plant assemblages. Positive shifts in both δ¹⁵N and δ¹³C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed ¹⁵N‐enrichment. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Do warming and humic river runoff alter the metabolic balance of lake ecosystems?     

Patricia Rodríguez  Pär Byström  Erik Geibrink  Per Hedström  Francisco Rivera Vasconcelos  Jan Karlsson 《Aquatic Sciences - Research Across Boundaries》2016,78(4):717-725

  相似文献   

Arctic Ocean manganese contents and sediment colour cycles   总被引：5，自引：0，他引：5  

Ludvig Löwemark  Martin Jakobsson  Magnus Mörth  & Jan Backman 《Polar research》2008,27(2):105-113

Cyclical variations in colour and manganese content in sediments from the central Arctic Ocean have been interpreted to represent climatically controlled changes in the input of Mn from the Siberian hinterland, and/or variations in the intermediate and deep water ventilation of the Arctic basins, although a diagenetic origin has not been excluded. A reinvestigation of core 96/12-1pc using an Itrax X-ray fluoresence (XRF) core scanner confirms that these colour cycles are indeed controlled by variations in Mn content, although changes in the source region of the sediment may override the Mn colour signal in certain intervals. The prominent Mn cycles show no correspondence to any of the other measured elements. This decoupling of Mn and the bulk chemistry of the sediment is taken to indicate that the cycles observed are caused by variations in water column ventilation and riverine input, rather than variations in sediment source or diagenesis. We therefore conclude that the Mn maxima do represent warm phases with increased ventilation and/or riverine input, and that they therefore could be used for chronostratigraphic correlation between cores from the central Arctic Ocean, where traditional isotope stratigraphy is difficult or impossible to establish because of the lack of calcareous microfossils.  相似文献