Wyniki wyszukiwania - Biblioteka Nauki

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Seasonal and diurnal variation of outdoor radon (222Rn) concentrations in urban and rural area with reference to meteorological conditions

100%

Podstawczyńska A. , Kozak K. , Pawlak W. , Mazur J.

Nukleonika

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2010

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tom Vol. 55, No. 4

543-547

EN

The objective of the study was to investigate temporal variability of outdoor radon (222Rn) concentration registered in the center of Łódź (urban station), at Ciosny (rural station) and Kraków (suburban station) in relation to meteorological parameters (i.e. air temperature, temperature vertical gradient, wind speed, soil heat flux, volumetric water content in soil) with special consideration of urban-rural differences. Continuous measurements of 222Rn concentration (at 60 min intervals) were performed at a height of 2 m above the ground using AlphaGUARDŽ PQ2000PRO (ionization chamber) from January 2008 to May 2009. 222Rn levels were characterized by a diurnal cycle with an early morning maximum and a minimum in the afternoon. The well-marked 24 h pattern of radon concentration occurred in summer at anticyclonic weather with cloudless sky, light wind and large diurnal temperature ranges. The urban measurement site was characterized by the lowest atmospheric 222Rn concentration and an urban-rural differences of radon levels increased from winter to summer and during the nighttime periods. The maximum contrasts of 222Rn levels between Łódź and Ciosny, reaching – 30 Bqźm–3, were registered in June and July during the urban heat island (UHI) phenomenon (a positive thermal anomaly of a city if compared to rural area) and strong thermal inversion near the ground in the rural area.

2

Ultrastructural studies on diurnal variations in mitochondria in various regions of the hepatic lobule

86%

Cieciura L. , Okroj W. , Krakowski G. , Godlewski W.

Folia Histochemica et Cytobiologica

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1985

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tom 23

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nr 3

3

Diurnal variations in carbon isotope composition of dissolved inorganic carbon [DIC] in a freshwater dam reservoir

86%

Orion-Jedrysek M. , Kurasiewicz M. , Trojanowska A. , Lewicka D. , Omilanowska A. , Kaluzny A. , Izydorczyk K. , Drzewicki W. , Zalewski M.

International Journal of Ecohydrology and Hydrobiology

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2006

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tom 06

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nr 1-4

53-59

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Adaptive strategy to drought conditions: diurnal variation in water use of a Central Asian desert shrub

72%

Wang S.-S. , Chen X. , Zhou K.-F. , Wang Q.

Polish Journal of Ecology

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2015

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tom 63

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nr 1

EN

Water availability is one of the most important factors limiting photosynthetic assimilation of carbon dioxide and growth of individual plants in terrestrial ecosystems. It is especially important for desert shrubs because the diurnal water availability is particularly sensitive to climate change in arid ecosystems. Water use efficiency (WUE) is an indicator of water availability and is frequently used to assess plant performance in various ecosystems, particularly in arid ecosystems. The WUE of plants has been widely assessed using ecological methods and field measurements; however, these approaches are impractical to obtain numerous near-simultaneous estimates of plant water status at the landscape-scale. Consequently, landscape-scale assessments of plant water status are practically pursued through modeling. In this study, measurement and modeling of the diurnal variations of WUE were conducted for a native dominant desert shrub, Tamarix ramosissima, in its original habitat on the periphery of the Gurbantunggut Desert, China. The diurnal net photosynthesis (An), stomatal conductance (gs), and transpiration (Tr) were measured for each individual using a portable photosynthesis system. A coupled model of stomatal conductance, photosynthesis, and transpiration was applied to simulate the diurnal dynamics of An, gs, Tr, and WUE. The model explained 83, 47, 83, and 55% of the variance in the measured An, gs, Tr, and WUE values, respectively, for this desert ecosystem in which T. ramosissima is sparsely distributed. The results demonstrated that the coupled photosynthesis-stomatal conductance-transpiration model strategy is a promising approach to estimate water availability in desert ecosystems in Central Asia.

5

Diurnal variations in nitrogen, phosphorus and iron compounds in the Southern Baltic Sea

72%

Sikorowicz G. , Falkowska L. , Burska D. , Dunajska D. , Pryputniewicz D. , Magulski R. , Lewandowska A.

Oceanologia

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2005

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tom 47

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nr 2

EN

In order to assess their short-term variability, nutrient concentrations were measured at standard depths at 2 h intervals in the deepest region of the Gdańsk Deep during the first ten days of June 2001. The mean concentrations of nutrients in the euphotic zone were: NN (NO2 −, NO3 −, NH4 +) – 1.93 μmol dm−3, PO4 3− – 0.12 μmol dm−3 and Fetot – 0.11 μmol dm−3. During daylight hours, when the rate of assimilation was fastest, concentrations of nitrogen, phosphorus and iron compounds were very low. The phosphate concentration fell to a minimum (0.03 μmol dm−3) between 04:00 and 10:00 hrs, while total iron dropped to 0.01 μmol dm−3 between 10:00 and 16:00 hrs. Both levels were below the limiting values for phosphorus and iron. At night, concentrations of NO3 − and PO4 3− rose by 25%, those of NH4 + and Fetot by 35%. The mean molar ratios of NN:PO4 3− and Fetot:PO4 3− in the surface layer were subject to significant daily fluctuations. The molar NN:PO4 3− ratio was higher than the optimum value established for the Baltic Sea. Below the halocline, the concentrations of dissolved iron and phosphorus rose as a result of diffusion from sediments in response to changing redox conditions.