Sediment-chemistry response to land-use change and pollutant loading in a hypertrophic lake, southern Sweden   总被引：3，自引：0，他引：3  

Siv Olsson  Joachim Regnéll  Anders Persson  Per Sandgren 《Journal of Paleolimnology》1997,17(3):275-294

Responses to recent land-use changes and pollutant loading in the sediment of a hypertrophic lake in southern Sweden were studied by comparison of geochemical, pollen and magnetic records with historical land-use data. A chronology was constructed for the last two centuries by correlating changes in the pollen diagram to major events in the land-use history. Sediment accumulation was low (mean c. 0.2 g cm^-2 yr^-1) prior to 1800 AD, when less than 25% of the catchment was arable land. Reorganization of the agrarian system during the 19th century increased the annually tilled area by 300%, which accelerated soil erosion and substantially increased the accumulation of allochtonous matter in the lake. Since the turn of the century 90% of the catchment has been ploughed every year. The deposition of clastic matter in the lake has, however, decreased due to a gradual rerouting of the drainage system, which has reduced the effective catchment area by c. 85%.Authigenic vivianite (Fe3(PO4)2.8H2O) is a major P phase in the preindustrial non-sulphidic sediments, which suggests that the sediments at that time served as a fairly efficient sink for P. The arable expansion, increased manuring and, eventually, the introduction of artificial fertilizers during the 19th century led to a massive influx of nutrients, which elevated primary production in the lake. Subsequent development of bottom water anoxia around 1900, in combination with an additional pollutant burden of sulphate within the lake basin, led to major alterations of the biogeochemical cycles. The most critical change in the post-1900 sediments involved the cycling of Fe and P. The linkage between the lacustrine P and Fe cycles can explain that FeS formation was paralleled by a release of P from the sedimentary pool. This supply of P to the lake basin must have supplemented the nutrient supply by modern agriculture and contributed to recent hypertrophication. The bacterial sulphate reduction also affected the generation of alkalinity which supported a significant calcite precipitation in the post-1900 sediments.S is enriched 10-fold in the post-1900 sediments compared to preindustrial values. Along with the rise in S, soot particles derived from fossil fuel combustion appear in the sediments for the first time. Therefore, Bussj¨osj¨on is thought to be a good example of how a well-buffered, highly productive lake may respond to the pollution by sulphur from acid rain.  相似文献   

Measuring surface-layer fluxes of heat and momentum using optical scintillation   总被引：2，自引：1，他引：2  

Reginald J. Hill  Gerard R. Ochs  James J. Wilson 《Boundary-Layer Meteorology》1992,58(4):391-408

An experiment is described showing that an optical scintillation instrument gives reliable values of heat and momentum fluxes in the surface layer, subject to the usual restrictions of homogeneity and steady state. This instrument measures the turbulence inner scale and refractive-index structure parameter, which are used to obtain the fluxes from Monin-Obukhov similarity relationships. The instrument gives space-averaged values over a propagation path that can range in length from tens to hundreds of meters. The history of the use of optical propagation to estimate fluxes is reviewed.  相似文献   

Analysis and interpretation of patterns within and between hydroclimatological time series in an alpine glacier basin     

A. M. Gurnell  M. J. Clark  C. T. Hill 《地球表面变化过程与地形》1992,17(8):821-839

This paper explores patterns within and between climatological and hydrological time series from an alpine glacier basin. Time series recorded in the basin of the Haut Glacier d'Arolla over the 1989 ablation season are subdivided into five subperiods. Box-Jenkins ARIMA (AutoRegressive Integrated Moving Average) and TFN (Transfer Function-Noise) models are estimated for each of the five subperiods and differences between the models are interpreted in the context of changing glacier hydrology, particularly the changing nature and extent of the glacier drainage network.  相似文献   

Heterogeneously nucleated calcite precipitation in Lake Constance. A short time resolution study     

Jonna Küchler-Krischun  Joachim Kleiner 《Aquatic Sciences - Research Across Boundaries》1990,52(2):176-197

Calcite precipitation in spring 1988 in Lake Constance was studied by measuring physical, chemical and biological parameters in daily intervals. Algae triggering calcite precipitation in spring after an induction period of 1 day wereStephanodiscus hantzschii andChlorella spp. whereas no time lag concerning maximum saturation index was observed. Number and size distribution of crystals were determined by microscopical methods. Simple equations were given for estimation of the precipitated mass of calcite by approximating the volume of calcite crystals by simple geometric bodies and multiplying by crystal numbers. Particulate calcium was analysed after dissolving suspended matter and amounted to 90% of inorganic dry weight. Crystals were observed for the first time after dissolved phosphorus was no more detectable.  相似文献   

IGU Commission on geographical education presents an international symposium     

Professor A. David Hill 《GeoJournal》1990,21(3):303-304

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Sulfur redox reactions: Hydrocarbons,native sulfur,Mississippi Valley-type deposits,and sulfuric acid karst in the Delaware Basin,New Mexico and Texas     

C. Hill 《Environmental Geology》1995,25(1):16-23

Hydrocarbons, native sulfur, Mississippi Valley-type (MVT) deposits, and sulfuric acid karst in the Delaware Basin, southeastern New Mexico, and west Texas, USA, are all genetically related through a series of sulfur redox reactions. The relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light ( ³⁴S = -22 to -12) H₂S and bioepigenetic limestone (castiles). This light H₂S was then oxidized at the redox interface to produce economic native sulfur deposits ( ³⁴S = -15 to +9) in the castiles, paleokarst, and along graben-boundary faults. This isotopically light H₂S also migrated from the basin into its margins to accumulate in structural (anticlinal) and stratigraphic (Yates siltstone) traps, where it formed MVT deposits within the zone of reduction ( ³⁴S = -15 to +7). Later in time, in th zone of oxidation, this H₂S reacted with oxygenated water to produce sulfuric acid, which dissolved the caves (e.g., Carlsbad Cavern and Lechuguilla Cave, Guadalupe Mountains). Massive gypsum blocks on the floors of the caves ( ³⁴S = -25 to +4) were formed as a result of this reaction. The H₂S also produced istopically light cave sulfur ( ³⁴S = -24 to -15), which is now slowly oxidizing to gypsum in the presence of vadose drip water.  相似文献   

The SiO bond and electron density distributions     

G. V. Gibbs  F. C. Hill  M. B. Boisen Jr. 《Physics and Chemistry of Minerals》1997,24(3):167-178

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The pattern and structure of one-person households in England and Wales and France     

Hall R  Ogden PE  Hill C 《International journal of population geography : IJPG》1997,3(2):161-181

"This paper examines the increase of one-person households during the 1980s in England and Wales and France set within the broader context of household change in Europe as a whole....One-person households vary geographically by age, with younger one-person households found especially in larger urban areas; older one-person households have a more varied distribution, although rural and traditional retirement areas have particular concentrations. Increases in numbers are a result of both compositional changes in the population (increasing numbers of divorced and never-marrieds as well as increasing numbers of elderly) and also an increasing propensity to live alone, especially among younger age groups."  相似文献   

Comparison of ground temperature response of energy pile and borehole heat exchanger during thermal response tests     

Jin Luo  Haifeng Zhao  Shuqiqang Gui  Wei Xiang  Joachim Rohn 《Environmental Earth Sciences》2016,75(22):1463

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Big Data Analytics for Earth Sciences: the EarthServer approach   总被引：1，自引：0，他引：1  

Peter Baumann  Paolo Mazzetti  Joachim Ungar  Roberto Barbera  Damiano Barboni  Alan Beccati 《International Journal of Digital Earth》2016,9(1):3-29

Big Data Analytics is an emerging field since massive storage and computing capabilities have been made available by advanced e-infrastructures. Earth and Environmental sciences are likely to benefit from Big Data Analytics techniques supporting the processing of the large number of Earth Observation datasets currently acquired and generated through observations and simulations. However, Earth Science data and applications present specificities in terms of relevance of the geospatial information, wide heterogeneity of data models and formats, and complexity of processing. Therefore, Big Earth Data Analytics requires specifically tailored techniques and tools. The EarthServer Big Earth Data Analytics engine offers a solution for coverage-type datasets, built around a high performance array database technology, and the adoption and enhancement of standards for service interaction (OGC WCS and WCPS). The EarthServer solution, led by the collection of requirements from scientific communities and international initiatives, provides a holistic approach that ranges from query languages and scalability up to mobile access and visualization. The result is demonstrated and validated through the development of lighthouse applications in the Marine, Geology, Atmospheric, Planetary and Cryospheric science domains.  相似文献