Modelling nitrogen dynamics for a mesoscale catchment using a minimum information requirement (MIR) concept / Modélisation des dynamiques de l'azote pour un bassin versant de taille moyenne,utilisant le concept de besoin minimum d'information

Abstract

Based on the water balance model LARSIM (Large Area Simulation Model), a model for the simulation of nitrogen transport was developed in a mesoscale catchment in southwest Germany. To meet the needs and constraints in river basin management, the nitrogen model was developed following the concept of minimum information requirement (MIR). The modelling concept uses only few calibration parameters and only easily accessible input data. Water balance, runoff generation and nitrogen transport were simulated on a 1-km² grid of sub-areas in which different land-use classes and soil characteristics were accounted. Temporal variability of the storage of mobile nitrogen were described using a monthly based mass balance. Nitrogen mobilization and transport was simulated using monthly values of different runoff components and data for soil properties, topography, hydrogeology and river network. The simulation was calibrated and validated using streamflow from two gauging stations and observed nitrogen concentrations at the catchment outlet, showing reasonable results for both streamflow and nitrogen dynamics. The results of the model application are discussed in the context of uncertainty problems and their implications for water management.     

Kriging: a method of interpolation for geographical information systems

Geographical information systems could be improved by adding procedures for geostatistical spatial analysis to existing facilities. Most traditional methods of interpolation are based on mathematical as distinct from stochastic models of spatial variation. Spatially distributed data behave more like random variables, however, and regionalized variable theory provides a set of stochastic methods for analysing them. Kriging is the method of interpolation deriving from regionalized variable theory. It depends on expressing spatial variation of the property in terms of the variogram, and it minimizes the prediction errors which are themselves estimated. We describe the procedures and the way we link them using standard operating systems. We illustrate them using examples from case studies, one involving the mapping and control of soil salinity in the Jordan Valley of Israel, the other in semi-arid Botswana where the herbaceous cover was estimated and mapped from aerial photographic survey.     

REJECTING VIOLENCE ON THE LANDSCAPE IN LAWRENCE,KANSAS*

ABSTRACT. Lawrence, Kansas, survived a tumultuous beginning. The young town endured attacks twice, in 1856 and 1863. The second raid, by the guerrilla William Quantrill's troop of more than 400 men, resulted in the deaths of 143 citizens. Lawrence serves as an example of how Americans memorialize unconventional warfare, targeted at citizens, in a material and permanent fashion on the landscape. Small and obscurely placed memorials fill the town, to the point that they have become ordinary. The memorialized landscapes of these tragedies thus display ambivalence toward the past and symbolically reject the loss of lives despite this era's high position in the literature and archival history of the town. Additionally, Lawrence has found alternative sources for its historical identity that do not reflect these tragedies but instead celebrate the city's pioneer establishment. In this article I use a set of methods for reading the memorialized landscape that includes archival and landscape analysis and uncovers the processes that have led to this town's understated and ambivalent memorialization and identity.     

MEXICAN URBAN COLONIAS IN THE SALT RIVER VALLEY OF ARIZONA

The history of the Salt River Valley is often characterized as a boomtown narrative that highlights the exploding Anglo population and rapid suburban sprawl that followed World War II. Frequently overlooked is the fundamental role that Mexicans played in the early suburbanization process through the formation of urban colonias, or suburban Mexican settlements. Early Mexican suburbs, despite their rural atmosphere, were connected to the pre–World War II urbanization process in the Salt River Valley. Our research seeks to amend and clarify the urban historical record by documenting the diverse and dispersed array of Mexican suburban settlements, a process generated by industrial agriculture, decentralization, and residential segregation.     

Reaction Between Ultramafic Rock and Fractionating Basaltic Magma II. Experimental Investigation of Reaction Between Olivine Tholeiite and Harzburgite at 1150-1050?C and 5 kb

We present results of experiments on mixtures of olivine tholeiiteand mantle harzburgite, at 5 kb and 1050–1150?C, underconditions of controlled hydrogen fugacity. The basalt end-memberwas Kilauea 1921 olivine tholeiite+3 wt.% H₂O, and the harzburgiteend-member was a mixture of olivine and orthopyroxene mineralseparates made from a mantle-derived lherzolite xenolith. Theexperiments on mixtures of basalt and harzburgite difl not reachequilibrium in runs ranging from 12 to 200 h duration. Relativelylarge concentration gradients persisted in both liquid and solidphases in mixed samples, whereas ‘control’ samplescontaining only basalt were reasonably homogeneous and wereprobably close to equilibrium. Compositions of solid phases produced, measured by electronmicroprobe, show a regular increase in Mg/(Mg+Fe) with increasingproportion of harzburgite at constant temperature, but olivineand clinopyroxene in mixed samples were not in Fe-Mg exchangeequilibrium. Modes measured for each sample show that the fractionof liquid relative to the amount of basalt in the sample wasconstant at constant temperature, and independent of bulk composition:reaction between 1921 basalt and harzburgite does not changethe mass of liquid in the system. Average experimental liquidcompositions for each sample were obtained by mass balance.Using Kds defined by the ‘control’ sample for eachtemperature, and mass balance constraints, phase assemblages(solid- and liquid-phase compositions and proportions) werecalculated for all mixtures. Whether samples included harzburgite or not, all average experimentalliquid compositions, and all predicted liquid compositions,for samples run at 1050?C, are high-alumina basalts by the definitionof Kuno (1960). By the criteria of Irvine & Baragar (1971),all but two average experimental liquid compositions in basalt-harzburgitemixtures, and all predicted liquid compositions in basalt-harzburgitemixtures, are calc-alkaline basalts and basaltic andesites,whereas liquids in samples containing only basalt are tholeiiticbasalts. Combined crystallization and reaction with harzburgitein the upper mantle will produce calc-alkaline derivative liquidsfrom an olivine tholeiite liquid under conditions of temperature,pressure, water and oxygen fugacity, and initial bulk compositionwhich would produce a tholeiitic liquid line of descent by crystallizationin a closed system. ^*Present address: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543Present address: Grant Institute of Geology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK     

Holocene deposits from Neptune's Cave, Nordland, Norway: Environmental interpretation and relation to the deglacial and emergence history of the Velfjord–Tosenfjord area

Neptune's Cave in the Velfjord–Tosenfjord area of Nordland, Norway is described, together with its various organic deposits. Samples of attached barnacles, loose marine molluscs, animal bones and organic sediments were dated, with radiocarbon ages of 9840 ± 90 and 9570 ± 80 yr BP being derived for the barnacles and molluscs, based on the superseded but locally used marine reservoir age of 440 years. A growth temperature of c . 7.5 °C in undiluted seawater is deduced from the δ¹³C and δ¹⁸O values of both types of marine shell, which is consistent with their early Holocene age. From the dates, and an assessment of local Holocene uplift and Weichselian deglaciation, a scenario is constructed that could explain the situation and condition of the various deposits. The analysis uses assumed local isobases and sea-level curve to give results: that are consistent with previous data, that equate the demise of the barnacles to the collapse of a tidewater glacier in Tosenfjord, and that constrain the minimum extent of local Holocene uplift. An elk fell into the cave in the mid-Holocene at 5100 ± 70 yr BP, after which a much later single 'bog-burst' event at 1780 ± 70 yr BP could explain the transport of the various loose deposits further into the cave.     

New discoveries of the Vedde Ash in southern Sweden and Scotland

The Vedde Ash (c. 10 300 ¹⁴ C BP) provides a key time-parallel marker horizon within the Younger Dryas chronozone or GS-1 event of the GRIP stratigraphy. Until recently, the known distribution of wind-blown Vedde Ash outside Iceland was restricted to the west coast of Norway, off-shore sequences close to the Outer Hebrides and the Greenland summit GRIP ice core. The first discoveries of the Vedde Ash in Scotland were reported in 1997, following the development of a new technique for extracting rhyolitic micro-tephra particles from minerogenic deposits. Here we report on the discovery of the Vedde Ash at additional sites in Scotland and at sites in southern Sweden. The concentration of tephra particles in sediments is highest in sites in western Norway, but is also relatively high in sites in southwestern Sweden, suggesting that the main ash cloud travelled eastwards from its volcanic source of Katla, in southern Iceland. Electron microprobe analyses do not indicate any clear geochemical evolution within the samples reported here.     

Torques exerted by a shallow fluid on a non-spherical, rotating planet

A general derivation is given for the torque exerted on a non-spherical planet by a shallow fluid, presenting in a unified form a number of results which are currently scattered through the literature, and deriving those results in a new way. This shows how the sum of gravitational and pressure torques can be rewritten as a 'centrifugal' torque plus a topographic torque due to pressure acting on topography measured relative to the geoid. This clarifies the physics behind the use of spherical coordinate atmosphere and ocean models for calculating torques on the earth. It also shows why the total torque due to the earth's equatorial bulge can be calculated as if it were a pressure torque on an 'effective bulge' of approximately 11 km, the gravitational torque partially offsetting the actual pressure torque on the earth's 21 km bulge.