Ecosystem Functions of Tidal Fresh, Brackish, and Salt Marshes on the Georgia Coast   总被引：2，自引：0，他引：2  

Kazimierz Więski  Hongyu Guo  Christopher B. Craft  Steven C. Pennings 《Estuaries and Coasts》2010,33(1):161-169

We examined patterns of habitat function (plant species richness), productivity (plant aboveground biomass and total C), and nutrient stocks (N and P in aboveground plant biomass and soil) in tidal marshes of the Satilla, Altamaha, and Ogeechee Estuaries in Georgia, USA. We worked at two sites within each salinity zone (fresh, brackish, and saline) in each estuary, sampling a transect from the creekbank to the marsh platform. In total, 110 plant species were found. Site-scale and plot-scale species richness decreased from fresh to saline sites. Standing crop biomass and total carbon stocks were greatest at brackish sites, followed by freshwater then saline sites. Nitrogen stocks in plants and soil decreased across sites as salinity increased, while phosphorus stocks did not differ between fresh and brackish sites but were lowest at salty sites. These results generally support past speculation about ecosystem change across the estuarine gradient, emphasizing that ecosystem function in tidal wetlands changes sharply across the relatively short horizontal distance of the estuary. Changes in plant distribution patterns driven by global changes such as sea level rise, changing climates, or fresh water withdrawal are likely to have strong impacts on a variety of wetland functions and services.  相似文献   

Experimental metasomatism of monazite and xenotime: mineral stability, REE mobility and fluid composition   总被引：2，自引：0，他引：2  

Callum J. Hetherington  Daniel E. Harlov  Bartosz Budzyń 《Mineralogy and Petrology》2010,99(3-4):165-184

In this study a Th-bearing monazite from a Brazil beach sand, a low Th monazite from a Malawi carbonatite, and a xenotime from a pegmatite in northern Pakistan were experimentally metasomatised in a series of common metamorphic and igneous fluids at 600°C/500 MPa and 900°C/1000 MPa. Fluids included H₂O, NaCl, and KCl brines, CaF₂?+?H₂O, 1m and 2m HCl, 1m and 2m H₂SO₄, 1m NaOH, and Na₂Si₂O₅?+?H₂O. The monazite show a variety of responses to the fluids ranging from no reaction (KCl?+?H₂O) to small compositional changes and partial replacement of the monazite grain rim by Th-enriched monazite in the NaOH and (Na₂Si₂O₅?+?H₂O) experiments respectively. The other acid and brine fluids induced varying degrees of partial dissolution in the monazite and xenotime, but no compositional alteration. Partial replacement of monazite grain rims by Th-enriched monazite occurred only in the alkaline fluids as the result of a coupled dissolution-reprecipitation process.  相似文献   

Impact cratering of granular mixture targets made of H₂O Ice–CO₂ Ice–pyrophylite     

M. Arakawa  M. Higa  J. Leliwa-Kopysty ski  N. Maeno 《Planetary and Space Science》2000,48(15):715-1446

Experiments related to impacts onto three-component targets which could simulate cometary nucleus or planetary regolith cemented by ices are presented here. The impact velocities are from 133 to 632 m s⁻¹. The components are powdered mineral (pyrophylite), H₂O ice, and CO₂ ice mixed 1:1:0.74 by mass. The porosity of fresh samples is about 0.48. Two types of the samples were studied: nonheated samples and samples heated by thermal radiation. Within the samples a layered structure was formed. The cratering pattern strongly depended on the history of the samples. The craters formed in nonheated targets had regular shapes. The volume was easy to be determined and it was proportional to impact energy E. The crater depth scales as E^0.5. Impacts on the thermally stratified target led to ejection of a large amount of material from the loose sub-crustal layer. For some particular interval of impact velocity a cratering pattern can demonstrate unusual properties: small hole through the rigid crust and considerable mass transfer (radially, outward of the impact point) within sub-crustal layer.  相似文献   

The Influence of Fluctuations of the Solar Emission Line Profileon the Doppler Shift of Interplanetary HLyα Lines Observed by the Hubble–Space–Telescope     

H. Scherer  H.J. Fahr  M. Bzowski  D. Ruciński 《Astrophysics and Space Science》2000,274(1-2):133-141

In an earlier research the employment of a radiation transport model with angle-dependent partial frequency redistribution, self-absorption by interplanetary hydrogen, realistic solar H_Lyαemission profile, and a time dependent `hot' hydrogen model to analyze 5 interplanetary H_Lyα glow spectra obtained with theHubble–Space–Telescope–GHRS spectrometer, has not resulted in unequivocal determination of a set of thermodynamical parameters of the interstellar hydrogen The residual discrepancies between the model and the data concern the observations performed within an interval of 1 year close to the solar minimum from very similar lines of sight. In this paper we investigate by calculating interplanetary H_Lyα lines with the use of a one hydrogen distribution and several solar H_Lyα line profiles whether this residual may be caused by possible variations in time of the shape of the solar H_Lyα emission line profile which cause variable illuminations of the interplanetary gas. These variations of illuminations cause variations in Doppler shift of the resonant interplanetary H_Lyα line that can amount to ≃ 4 km s^-1in the line peak. Consequently we conclude that without adequate knowledge of the solar H_Lyα emission line profile during spectral observations of the interplanetary hydrogen gas it is impossible to obtain an agreement between models and observations better than by this value. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Distribution of compact object mergers around galaxies     

Tomasz Bulik  Krzysztof Belczy&#;ski  Wojciech Zbijewski 《Monthly notices of the Royal Astronomical Society》1999,309(3):629-635

Compact object mergers are one of the currently favoured models for the origin of gamma-ray bursts (GRBs). The discovery of optical afterglows and identification of the nearest, presumably host, galaxies allow the analysis of the distribution of burst sites with respect to these galaxies. Using a model of stellar binary evolution we synthesize a population of compact binary systems which merge within the Hubble time. We include the kicks in the supernovae explosions and calculate orbits of these binaries in galactic gravitational potentials. We present the resulting distribution of merger sites and discuss the results in the framework of the observed GRB afterglows.  相似文献   

Influence of a Multipurpose Retention Reservoir on Extreme River Flows,a Case Study of the Nielisz Reservoir on the Wieprz River (Eastern Poland)     

Krzysztof Raczyński 《Water Resources》2020,47(1):29-40

Water Resources - The objective of this paper is the assessment of the effect of a multifunctional mid-size retention reservoir on the occurrence of floods and low flows. The study object was...  相似文献   

Health risk assessment related to an effect of sample size fractions: methodological remarks     

Kicińska  Alicja 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1867-1887

Contents of As, Cd, Co, Cr, Cu, Ni, Pb and Zn were determined in the material collected in sandboxes of seven spa resorts located in S Poland (CCE) and their results used to establish a health risk of children. After sieving out grains > 2 mm, the bulk samples were quantitatively separated into four grain fractions: 2000–1000, 1000–200, 200–63 and < 63 µm. In each of them were determined: the mineral composition, the total contents of the elements, and the distribution of the elements among the fractions distribution factor. In the bulk material < 2 mm, the totals of the elements are 5–64 times lower than in the finest fractions (< 63 µm). Considering that the finest fractions are enriched in clay minerals such as clinochlore, illite and kaolinite, which can adsorb and desorb metals, this material is most dangerous for children, staying both permanently and temporarily in the spas. The total health risks HI resulting from non-carcinogenic elements present in the fractions < 63 µm are 1.26 and 0.94, for the children-residents 3 and 6 years old, respectively. The figures are disturbing as one of them exceeds and the other is close to a permissible limit of 1. The highest contribution (93.4%) into the total HI is caused by inadvertent swallowing the soil “dirt”: the ingestion path HQ _ing for the 3 years old residents is 1.17, and for the 6-year olds 0.88. With respect to the elements, the highest is the risk resulting from Pb: HQ _in values of the residents are 4.71E−01 and 3.54E−01 for the 3-year olds and the 6-year olds. Slightly lower are the HQ _ing values calculated for both age groups: in the case of Cr—3.12E−01 and 2.34E−01 and As—2.92E−01 and 2.19E−01). The dermal path (HQ _dermal ) contributes to the total HI much less as it equals 6.5%, while the contribution of the inhalation path (HQ _inhal ) is considerably the lowest and equals only 0.1%. The Risk indexes determined in the case of cancerogenic components for both age groups of the spa residents are lower than the permissible limit 10E−5 and equal 6.48E−06 and 9.72E−06, respectively. Considering the children that only visit the spas, all the calculated indexes, i.e., HI and Risk, are significantly lower than those determined for the children-residents.

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Sibsonian and non-Sibsonian natural neighbour interpolation of the total electron content value     

Kacper Kotulak  Adam Froń  Andrzej Krankowski  German Olivares Pulido  Manuel Henrandez-Pajares 《Acta Geophysica》2017,65(1):13-28

In radioastronomy the interferometric measurement between radiotelescopes located relatively close to each other helps removing ionospheric effects. Unfortunately, in case of networks such as LOw Frequency ARray (LOFAR), due to long baselines (currently up to 1500 km), interferometric methods fail to provide sufficiently accurate ionosphere delay corrections. Practically it means that systems such as LOFAR need external ionosphere information, coming from Global or Regional Ionospheric Maps (GIMs or RIMs, respectively). Thanks to the technology based on Global Navigation Satellite Systems (GNSS), the scientific community is provided with ionosphere sounding virtually worldwide. In this paper we compare several interpolation methods for RIMs computation based on scattered Vertical Total Electron Content measurements located on one thin ionospheric layer (Ionospheric Pierce Points—IPPs). The results of this work show that methods that take into account the topology of the data distribution (e.g., natural neighbour interpolation) perform better than those based on geometric computation only (e.g., distance-weighted methods).  相似文献   

Changes of snow cover in Poland   总被引：2，自引：2，他引：0  

Małgorzata Szwed  Iwona Pińskwar  Zbigniew W. Kundzewicz  Dariusz Graczyk  Abdelkader Mezghani 《Acta Geophysica》2017,65(1):65-76

The present paper examines variability of characteristics of snow cover (snow cover depth, number of days with snow cover and dates of beginning and end of snow cover) in Poland. The study makes use of a set of 43 long time series of observation records from the stations in Poland, from 1952 to 2013. To describe temporal changes in snow cover characteristics, the intervals of 1952–1990 and of 1991–2013 are compared and trends in analysed data are sought (e.g., using the Mann–Kendall test). Observed behaviour of time series of snow-related variables is complex and not easy to interpret, for instance because of the location of the research area in the zone of transitional moderate climate, where strong variability of climate events is one of the main attributes. A statistical link between the North Atlantic Oscillation (NAO) index and the snow cover depth, as well as the number of snow cover days is found.  相似文献   

Free core nutation period inferred from the gravity measurements at Józefosław     

Marcin Rajner  Aleksander Brzeziński 《Studia Geophysica et Geodaetica》2017,61(4):639-656

The Free Core Nutation (FCN) is an important eigenmode which affects both Earth rotation and body tide. The FCN parameters, the resonance period and the quality factor are important for understanding the dynamics of the Earth at nearly diurnal periods. Those parameters are usually estimated either from the Very Long Baseline Interferometry (VLBI) observations of nutation, or from the tidal gravity measurements. In this paper we investigate the determination of the FCN parameters from gravity records covering a period of more than three years, collected with the use of a LaCoste&Romberg Earth Tide no. 26 gravimeter, located at Józefos?aw observatory near Warsaw. From the resonant enhancements of gravimetric factors and phases of diurnal tidal gravity waves, we could infer the FCN period to be equal to 430 sidereal days. This result is in very good agreement with previous gravimetric and VLBI nutation results, confirming the discrepancy in the dynamic flattening of the outer liquid core from its theoretical value based on the hydrostatic equilibrium assumption. The estimated FCN quality factor (Q ≈ 1300) is considerably smaller than the VLBI nutation result, which confirms that the local gravity measurements are more sensitive than VLBI global analyses to site-dependent phenomena (such as atmospheric and indirect ocean tidal effects). We also investigated the importance of gravimetric corrections in the FCN analysis, including numerical tests and simulations. This allowed us to estimate the uncertainty of FCN parameters due to improper or incomplete set of environmental corrections. We took also into account the impact of gravimetric factor errors and tidal wave selection on estimated FCN parameters. We demonstrated that despite relatively noisy measurements due to unfavorable gravimeter location, we were able to obtain very good results in case when proper correction and tidal wave selection were applied.  相似文献