Dynamics of Russian Forests and the Carbon Budget in 1961–1998: An Assessment Based on Long-Term Forest Inventory Data     

Anatoly Shvidenko  Sten Nilsson 《Climatic change》2002,55(1-2):5-37

Development trends of Russian forests and their impact on the global carbon budget were assessed at the national level on the basis of long-term forest inventory data (1961–1998). Over this period, vegetation of Russian forest lands are estimated as a carbon sink, with an annual average level of carbon sequestration in vegetational organic matter of 210 ± 30 Tg C · yr^–1 (soil carbon is not considered in this study), of which 153 Tg C · yr^–1 were accumulated in live biomass and 57 Tg C · yr^–1 in dead wood. The temporal variability of the sink is very large; for the five-year averages used in the analysis, the C sequestration varies from about 60 to above 300 Tg C· yr^–1. It is shown that long-term forest inventory data could serve as an important information base for assessing crucial indicators of full carbon accounting of forests.  相似文献   

Dew water collector for potable water in Ajaccio (Corsica Island, France)     

Marc Muselli  Daniel Beysens  Jacques Marcillat  Irina Milimouk  Torbjrn Nilsson  Alain Louche 《Atmospheric Research》2002,64(1-4)

We report on the development of an inexpensive radiative condenser for collecting atmospheric vapor. Based on the experience gained using a small working model in Grenoble (France), a prototype of 10×3 m² was established in Ajaccio (Corsica, France). The condensing surface is a rectangular foil made of TiO₂ and BaSO₄ microspheres embedded in polyethylene and has an angle of 30° with respect to horizontal. The hollow part of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Dew measurements were correlated with meteorological data and compared to dew condensed on a horizontal polymethylmethacrylate (PMMA, Plexiglas) reference plate. The plate served as a reference standard unit and was located nearby. Between July 22, 2000 and November 11, 2001 (478 days), there were 145 dew days for the reference plate (30%), but 214 dew days for the condenser (45%). This yield corresponds to 767 l (3.6 l, on average, per dew day). The maximum yield in the period was 11.4 l/day. Dew mass can be fitted to a simple model that predicts dew production from simple meteorological data (temperature, humidity, wind velocity, cloud cover). Chemical analyses of the water collected from the plate were performed from October 16, 1999 to July 16, 2000 and from the condenser, from July 17, 2000 to March 17, 2001. The following parameters were investigated: suspended solids, pH, concentration of SO₄²⁻, Cl⁻, K⁺, Ca²⁺ ions. Only Cl⁻ and SO₄²⁻ ions were sometimes found significant. Wind direction analyses revealed that Cl⁻ is due to the sea spray and SO₄²⁻ to the combustion of fuel by an electrical plant located in the Ajaccio Gulf. Except for a weak acidity (average pH≈6) and high concentration of suspended solids, dew water fits the requirements for potable water in France with reference to the above ions.  相似文献   

Duration of soil cadmium and lead pollution from shale-based alum production     

Bo Bergbck  Mats Eklund  Ulrik Lohm  John Svidn 《Journal of Geochemical Exploration》1997,58(2-3)

The scope of this study is to assess the present impact from an historical emission source, in order to provide information on the duration of this metal pollution problem.The present distribution of cadmium and lead, emitted from a Swedish alumworks between 1726–1840, was studied in soils, sediments and ground water. The soil data imply that cadmium has disappeared from the surface soils during the 150 to 250 years that have passed since the emissions ceased. Lead concentrations of the soil are elevated only within 200 m from the site of the works. Further away, the lead concentrations are almost at background level. A possible explanation for this pattern, is that lead dispersed in large particles has not yet fully disintegrated and leached down the soil profile, in contrast to the smaller particles deposited further away.The metal concentrations in the ground water wells are slightly higher than the Swedish average but probably governed by the pH of the water, rather than the occurrence of large amounts of metals. Elevated lead concentrations were found in a few sediment samples in the river mouth downstream from the works. These elevated concentrations coincided with the abundant occurrence of small particles of used shale, indicating their origin.Cadmium is not found, at present, in the soil around the alumworks in concentrations substantially above background levels. Consequently, it is likely that the cadmium deposited in the area, has leached through the upper layers of the soil profile on its way to the sea sediments. Likewise, the lead concentrations in the soil beyond 200 m from the alumworks are not above background levels which indicate that losses through leaching have occurred at a rate of 0.5 to 1.5% yr⁻¹.Finally, comparisons with other long-term perspective studies give an opportunity to discuss the rate for the disappearance of an environmental problem.  相似文献   

Potentiometrically measured Eh in groundwaters from the Scandinavian Shield     

L. Auqué  M.J. Gimeno  J. Gómez  A.-C. Nilsson 《Applied Geochemistry》2008

Measurement and interpretation of electrochemical Eh values in natural reducing groundwaters is a complex task. SKB, the company in charge of disposal of nuclear fuel wastes in Sweden, has developed a refined methodology for the determination of this parameter in packered sections in boreholes. The methodology consists of the simultaneous use of three different electrodes (Pt, Au and C) both at depth and at the surface, and maintaining continuous logging over a long period of time. Apart from Eh, the logging also includes other parameters such as pH, dissolved O₂, conductivity and temperature. This methodology has been used since the 80s in the framework of the hydrogeochemical characterisation programs supported by SKB at different sites in the Scandinavian Shield. All the existing databases have been revisited in this work using a uniform set of criteria to select Eh values of the Swedish groundwaters as a function of depth.  相似文献   

Migration pattern of juvenile cod (Gadus morhua) on the Swedish west coast     

Pihl  Leif; Ulmestrand  Mats 《ICES Journal of Marine Science》1993,50(1):63-70

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MtDNA and microsatellite variation in Baltic Atlantic salmon   总被引：5，自引：0，他引：5  

Nilsson  J. 《ICES Journal of Marine Science》1997,54(6):1173-1176

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Field compaction of bentonite-based backfilling   总被引：1，自引：0，他引：1  

Jan Nilsson 《Engineering Geology》1985,21(3-4):367-376

This report describes the application and field compaction of a tunnel backfill, which consists of a mixture of commercial Na bentonite (MX 80) powder and suitably graded ballast material. The ballast material consists of quartz-rich sand and feldspar rich filler. Important characteristics for the tunnel backfill are low permeability, low compressibility and a certain swelling potential.  相似文献   

On the influence of kriging parameters on the cartographic output—A study in mapping subglacial topography     

Ute C. Herzfeld  Mats G. Eriksson  Per Holmlund 《Mathematical Geosciences》1993,25(7):881-900

Geostatistics provides a suite of methods, summarized as kriging, to analyze a finite data set to describe a continuous property of the Earth. Kriging methods consist of moving window optimum estimation techniques, which are based on a least-squares principle and use a spatial structure function, usually the variogram. Applications of kriging techniques have become increasingly wide-spread, with ordinary kriging and universal kriging being the most popular ones. The dependence of the final map or model on the input, however, is not generally understood. Herein we demonstrate how changes in the kriging parameters and the neighborhood search affect the cartographic result. Principles are illustrated through a glaciological study. The objective is to map ice thickness and subglacial topography of Storglaciären, Kebnekaise Massif, northern Sweden, from several sets of radio-echo soundings and hot water drillings. New maps are presented.  相似文献   

Dormant bacteria in lake sediments as palaeoecological indicators     

Ingemar Renberg  Mats Nilsson 《Journal of Paleolimnology》1992,7(2):127-135

Lake sediments contain viable allochthonous bacteria that can be cultured and used for palaeoecological studies. To be a good palaeoindicator, a bacterium must be able to survive in sediments for long periods of time, but also be unable to reproduce in the lake bottom. Bacteria can survive the unfavourable environmental conditions in lake sediments as resting cells. The endospore is the most specialized form and gives the bacterium an extreme longevity. The oldest viable endospores isolated from lake sediments that we are aware of are about 9000 years old.Several species, mainly in the genera Thermoactinomyces, Bacillus and Clostridium, form endospores. Clostridium perfringens has been used as palaeoindicator for sewage pollution, while Thermoactinomyces vulgaris is an indicator for past agricultural activity in the boreal forest zone and a potential climatic indicator in other vegetation zones. Although isolation and enumeration of bacterial endospores from lake sediments is rather easy and has considerable potential as a powerful tool in palaeoecology, the number of studies using palaeoecological approaches is limited.  相似文献   

Field characterization of vertical bromide transport in a fractured glacial till     

William G. Harrar  Lawrence C. Murdoch  Bertel Nilsson  Knud Erik S. Klint 《Hydrogeology Journal》2007,15(8):1473-1488

A study of the fracture distribution, hydraulic properties, groundwater levels and the transport of bromide was conducted to characterize vertical transport in the oxidized and reduced zones of a fractured glacial till. Detailed vertical profiles of groundwater levels and solute concentrations were obtained over a 4.5-year period. Vertical migration occurred at several time scales, as a low concentration front was rapidly transported at rates of 100–500 m/year ahead of a slower moving main plume, which advanced at rates of 0.2–0.8 m/year. Concentrations in the leading edge of the plume displayed a high degree of spatial variability over short vertical distances through day 1,000. Late in the test, the influence of matrix diffusion became apparent as concentration patterns developed from being irregular to more uniform distributions. Calculations show that the mass within the low concentration plume front accounts for less than 1% of the total solute mass. Simulation of the breakthrough curves using a simple one-dimensional advection-dispersion model of transport in porous media indicates that vertical transport is dominated by advection. Furthermore, the results indicate that vertical transport of solutes in oxidized and reduced zones of the till can be adequately simulated using an equivalent porous media.  相似文献