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61.
Mateusz Ruszkowski 《Astrophysics and Space Science》2003,288(1-2):133-142
I discuss the transfer of polarized synchrotron radiation in relativistic jets. I argue that the main mechanism responsible for the circular polarization properties of compact synchrotron sources is likely to be Faraday conversion and that, contrary to common expectation, a significant rate of Faraday rotation does not necessarily imply strong depolarization. The long-term persistence of the sign of circular polarization, observed in some sources, is most likely due to a small net magnetic flux generated in the central engine, carried along the jet axis and superimposed on a highly turbulent magnetic field. I show that the mean levels of circular and linear polarizations depend on the number of field reversals along the line of sight and that the gradient in Faraday rotation across turbulent regions can lead to`correlation depolarization'. The model is potentially applicable to a wide range of synchrotron sources. In particular, I demonstrate how the model can naturally explain the excess of circular over linear polarization in the Galactic Center (SgrA*) and the low-luminosity AGN M81*. 相似文献
62.
Activity coefficients of 137Cs determined during culminating flood waters in August 1997 in the estuary of the Oder River, discharging to the Pomeranian Bay as well as in the coastal and open-seawaters of the Bay, did not show enhanced levels of the nuclide as compared to those measured before the flood. It is thus concluded that the flood did not contribute to releasing the nuclide from eroded soil particles. The bioconcentration factors of 137Cs in the riverine plankton has been found to be one to two orders of magnitude higher than those determined in the Pomeranian Bay plankton. 相似文献
63.
Strontium isotope identification of water mixing and recharge sources in a river system (Oder River,central Europe): A quantitative approach
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Mateusz Zieliński Jolanta Dopieralska Zdzislaw Belka Aleksandra Walczak Marcin Siepak Michał Jakubowicz 《水文研究》2018,32(16):2597-2611
This study uses Sr isotope composition (87Sr/86Sr) and Sr content of waters of the Oder, one of the largest rivers in central Europe, to fingerprint natural and anthropogenic contributions to its Sr budget and to evaluate water mixing processes in its hydrological system. It also demonstrates a simple method of quantifying natural and anthropogenic Sr inputs in the watershed. The method has potential for environmental and archaeological research because past Sr geochemistry of river water can easily be reconstructed. For the first time, a catchment‐scale impact of anthropogenic sources on the Sr budget of a middle‐size river is shown in a quantitative way. The water of the Oder is characterized by a relatively uniform Sr isotope composition, from 0.7100 to 0.7108, contrasting with strong variations in Sr concentration, from 0.25 to 1.27 mg/L. There is a general seasonal trend in variability, with waters becoming more radiogenic and dilute with respect to the Sr in the spring time. This Sr systematics differs significantly from the Sr budgets of the majority of the Oder tributaries that exhibit more radiogenic composition and systematically lower Sr concentrations. A mixing scenario in the Oder involves Sr contribution from four principal water sources: (a) shallow ground waters with Sr derived from near‐surface weathering of silicates, (b) moderately radiogenic mine waters from the Upper Silesian Coal Basin, (c) unradiogenic mine waters from the Permian sequence of the copper district, and (d) unradiogenic ground waters from shallow‐seated Palaeogene, Neogene, and Mesozoic aquifers. The Sr budget of the Oder is primarily controlled by inputs of dissolved Sr from anthropogenic sources, which overprint the natural background, controlled by geology. Thus, about 47.5% of Sr originates from agriculture, industrial, and municipal additions, 31.5% from mine water inputs, and only 21% from natural sources, that is, rock weathering and atmospheric precipitation. Reconstruction of the past Sr chemistry of the Oder reveals that its present‐day Sr isotope composition is temporary and significantly different from that of the preindustrial times. 相似文献
64.
Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project 总被引:1,自引:1,他引:0
Zbigniew W. Kundzewicz Markus Stoffel Ryszard J. Kaczka Bartłomiej Wyżga Tadeusz Niedźwiedź Iwona Pińskwar Virginia Ruiz-Villanueva Ewa Łupikasza Barbara Czajka Juan Antonio Ballesteros-Canovas Łukasz Małarzewski Adam Choryński Karolina Janecka Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641
The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness. 相似文献
65.
Żaneta Polkowska Mieczysław Sobik Marek Błaś Kamila Klimaszewska Barbara Walna Jacek Namieśnik 《Journal of Atmospheric Chemistry》2009,62(1):5-30
Hoarfrost and rime analysis was based on the collection of samples between 2003 and 2006 from 8 sites, which represent both
lowland (northern) and mountainous (southern) parts of Poland. On the other hand 4 of these sites belong to “urban” and 4
to “rural” category. pH, conductivity, SO42−, NO3−, Cl−, H+, NH4+, Ca2+, Mg2+, Na+, K+ have been determined in order to study the chemistry of hoarfrost and rime. Higher total inorganic ionic content (TIC) in
hoarfrost and rime (2.46 meq·l−1 and 1.23 meq·l−1 respectively) was observed when compared with precipitation (0.37 meq·l−1). Large variability of TIC and chemical composition of individual samples were typical at each of the measurement sites depending
on emission patterns, atmospheric conditions and local terrain topography. Higher concentrations of both hoarfrost and rime
occurred in southern (mountainous) rather than in northern (lowland) part of Poland which can be explained by worse pollutant
dispersion conditions in the south. The surprisingly low hoarfrost concentrations in urban coastal stations in the area of
the Bay of Gdansk were attributed to the cleaning effect of nocturnal breeze-type circulation, best pronounced in cool part
of the year. Due to relatively high pollutant concentration and long duration, hoarfrost and rime are at least significant
factors in environmental processes in different ecosystems in Poland. 相似文献
66.
Krzysztof Sośnica 《Acta Geophysica》2015,63(4):1181-1203
Satellite Laser Ranging (SLR) to LAGEOS has a remarkable contribution to high-precise geodesy and geodynamics through deriving and validating various global geophysical models. This paper validates ocean tide models based on the analysis of satellite altimetry data, coastal tide gauges, and hydrodynamic data, i.e., CSR3.0, TOPEX4.0, CSR4.0A, FES2004, GOT00.2, and the CSRC Schwiderski model. LAGEOS orbits and SLR observation residuals from solutions based on different ocean tide models are compared and examined. It is found that LAGEOS orbits are sensitive to tidal waves larger than 5 mm. The analysis of the aliasing periods of LAGEOS orbits and tidal waves reveals that, in particular, the tidal constituent S2 is not well established in the recent ocean tide models. Some of the models introduce spurious peaks to empirical orbit parameters, which can be associated with S2, Sa, and K2 tidal constituents, and, as a consequence, can be propagated to fundamental parameters derived from LAGEOS observations. 相似文献
67.
Isotope and hydrochemical data of the thermal water system in Cieplice
laskie Zdrój (Spa) indicate the existence of two subsystems that greatly differ in volume and which meet at the fault zones of a granitic horst, where they discharge at an altitude of about 340m. One of the subsystems is very small (about 4 × 103 m3) as indicated by the tritium age of the order of 10 years and a low outflow rate. Its recharge area found from the δ18O and δD values, is about 200m above the springs, most probably on the slopes of the foothills of the Karkonosze Mountains south-southwest of the spa. The large subsystem contains water which is free of tritium and whose 14C content is from 1 to 8 pmc with δ13C = −8.0 to −9.2‰. The isotopic composition of this water reflects either the climatic effect (low-altitude recharge during a cooler pre-Holocene climate) or the altitude effect (recharge in the early Holocene period at about 1000m at the heights of the Karkonosze assuming that the 14C concentration is strongly reduced by exchange with calcite in veins). For the former hypothesis, the recharge area of this water is probably either at the foot of the southeastern slopes of the Kaczawa Mountains or/and at the foot of the Rudawy Janowickie Mountains, to the east of Cieplice. The noble gas temperatures are more consistent with the pre-Holocene recharge. Similarly, the 4He excess and 40Ar/36Ar ratio support the hypothesis of a pre-Holecene age. The constant 3He/4He ratio of 26 × 10−8 for highly different helium contents indicates crustal origin of helium. For the pre-Holocene age of water its volume is calculated at >- 109m3 (stagnant water in micropores and mobile water in fractures) and the hydraulic conductivity of the host granite massif is estimated at about 7 × 10−8 ms−1. Two outflows from this subsystem have different and variable fractions of a modern water component (bomb age), most probably originating from the bank infiltration of a nearby stream. 相似文献
68.
Żaneta Polkowska Kamila Skarżyńska Tadeusz Górecki Jacek Namieśnik 《Journal of Atmospheric Chemistry》2006,53(3):211-236
Formaldehyde levels were determined in various forms of atmospheric precipitation (rain, snow, road and roof runoff, throughfall) and deposition (rime, hoarfrost, dew) collected over twelve months at various locations in two large urban agglomerations and along two highways. HCHO was found in 303 of 500 samples analyzed, with concentrations ranging from 0.05 to 10.7 mg/dm3. The results confirmed the significant effect of vehicular traffic on formaldehyde levels in various forms of wet deposition. Correlations of formaldehyde levels with other parameters commonly monitored in precipitation and/or deposition were also examined. No correlation was found between HCHO levels and rain volume. On the other hand, positive correlations were found for hydrogen peroxide, non-sea-salt sulphate, nitrate, ammonia, and total organic carbon (TOC). In addition, the effect of selected meteorological parameters (temperature, wind speed, wind direction, rainfall) on the concentration of formaldehyde in various forms of precipitation and runoff (road runoff, roof runoff, throughfall) was studied. The only correlation found was that between HCHO concentration and daily rainfall. 相似文献
69.
Heavy metals in sediments as evidence for recent pollution and quasi-estuarine processes: an example from Lake Druzno,Poland 总被引:1,自引:0,他引:1
Wojciech Tylmann Roman Gołębiewski Piotr Paweł Woźniak Karolina Czarnecka 《Environmental Geology》2007,53(1):35-46
This article presents the results of a geochemical investigation of sediments from Lake Druzno (northern Poland), a reservoir
fed by freshwater from the catchment, with periodic input of brackish water from Vistula Lagoon. This study analyzed the spatial
variation in heavy metal content in surface sediments as well as the temporal changes in metal content in two sediment cores
dated using the 210Pb method. In the surface sediments, the highest metal concentrations were recorded in the northern part of the lake, with
lower concentrations in the central and southern parts. Absolute values of metal concentrations in the cores were low, but
normalization with respect to Al showed an increase during the second half of the 20th century. Mean enrichment factors (EF)
in sediments from the second half of the 20th century ranged from insignificant (1–1.2) for Fe to (1.55–3.3) for Cu, Cd, Pb
and Zn. The sediments deposited before 1950 had lower EF values (>1.5) and had low variability. Results from both the surface
sediments and the cores indicate that the main source of lake pollution is brackish water intrusion from the Vistula Lagoon
via the contaminated River Elbląg. 相似文献
70.
The sediment trap technique was used to study the sedimentation processes in two parts of Lake Goci, central Poland, the deep of the main basin and the shallow bay area. From field and lab data was noted that seasonal and annual deposition of pollen grains on the lake bottom was disturbed in the main basin by an increase in water mass dynamics and by resuspension and focusing. Greater concordance between pollen sedimentation and the flowering periods of plants was found in the bay area, where sediment resuspension took place sporadically and with less intensity, compared to the main basin. Futhermore, it is suggested that resuspension of pollen can occur even if laminated sediments are formed, a process which therby diminishes the chronostratigraphic value of sediments and pollen analyses. 相似文献