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591.
Vrchotová N Tríska J Urban O Peknic L 《Environmental pollution (Barking, Essex : 1987)》2004,131(1):55-59
The amount of catechin and 4-hydroxyacetophenone in the methanolic extract of the Norway spruce needles at the locality Bíly Kríz (Moravian-Silesian Beskydy Mts.) was found in the range 2.8-12.1 mg g(-1) (dry weight) and 0.2-17.7 mg g(-1) (dry weight), respectively. Total amount of catechin (sum of the last three needle year-classes) is statistically higher (p<0.01) in the sparse areas compared to the dense ones and similar trends were recorded for catechin content in current and one-year-old needles. These results may support an idea about primary control of phenolic production by the incident solar radiation, which depends on the social position of the tree and canopy closure degree. 相似文献
592.
Multivariate statistical methods including pattern recognition (Principal Component Analysis--PCA) and modeling (Multiple Linear Regression--MLR, Partial Least Squares--PLS, as well as Principal Component Regression--PCR) methods were carried out to evaluate the state of ambient air in Miskolc (second largest city in Hungary). Samples were taken from near the ground at a place with an extremely heavy traffic. Although PCA is not able to determine the significance of variables, it can uncover their similarities and classify the cases. PCA revealed that it is worth to separate day and night data because different factors influence the ozone concentrations during all day. Ozone concentration was modeled by MLR and PCR with the same efficiency if the conditions of meteorological parameters were not changed (i.e. morning and afternoon). Without night data, PCR and PLS suggest that the main process is not a photochemical but a chemical one. 相似文献
593.
Reactions of lead sorption onto soil are largely affected by properties and composition of soil and its solution. In this study, the lead sorption onto regosol eutric soil from Francisco I. Madero, Zacatecas, Mexico is evaluated at different pH values. Soil samples were suspended in lead solutions of 10, 25, 50, 100, 150, 200, 300, and 400 mg/l (as Pb(NO3)2). The pH was adjusted at 2, 3, 4, and 5.5 with nitric acid for each of the lead solution concentrations. In all the cases the ionic strength was I=0.09 M with calcium nitrate. The solid-liquid-ratios were fixed in 1:100 and 1:200 g/ml. The results show that lead sorption increases when pH increases. Experimental isotherms were adjusted by both Langmuir and Freundlich models. The Langmuir affinity parameter, K, indicates that the lead sorption capacity of Francisco I. Madero soils is largely perceptible to pH changes. 相似文献
594.
Lalah JO Schramm KW Henkelmann B Lenoir D Behechti A Günther K Kettrup A 《Environmental pollution (Barking, Essex : 1987)》2003,122(2):195-203
A single tertiary isomer which is believed to be one of the major branched isomers of the isomeric nonylphenol was synthesized for use in investigations on its metabolism and estrogenicity in aquatic organisms. The physico-chemical properties of the isomer were determined to enable the prediction of its behaviour in aquatic environments. From laboratory investigations on its dissipation and distribution in lake water, which are reported in this paper, it was found that it had a half-life of dissipation of 38.1 days and 20.1 days in an open lake water and in an open lake water/ sediment system, respectively, and to be rapidly partitioned in to sediment giving a high concentration factor of 1.76 after 28 days with an initial dose concentration of 2.52 ppm. The main dissipation route was found to occur through volatilization and co-distillation. The isomer was, however, found to be resistant to biodegradation in both the lake water and sediment, showing only a slight 9% loss (after 56 days) and 4.2% loss (after 28 days), of the 14C-residues in lake water and lake water/sediment systems, respectively, by microbial activity. Transformation to other more polar metabolites possibly by hydroxylation was also found to be minimal in both lake water and sediment samples after 14 days by HPLC analysis. After 7 days, only 2.25 and 7.4% transformation to a more polar metabolite was detected in lake water and sediment samples, respectively. 相似文献
595.
Gorbunov AV Frontasyeva MV Kistanov AA Lyapunov SM Okina OI Ramadan AB 《Journal of environmental science and health. Part. B》2003,38(2):181-192
This article presents basic data on the content of Cr, Fe, Ni, Cu, Zn, As, Cd, Sb, Hg, and Pb in staple foodstuffs and agriproduct grown in Russia (Astrakhan region and the town of Belovo) and Egypt (Helwan region). The dependence of the concentration of metals in agriproducts on the content and chemical form of existence in irrigation water and soils is indicated. 相似文献
596.
Trimethylbenzoic acids as metabolite signatures in the biogeochemical evolution of an aquifer contaminated with jet fuel hydrocarbons 总被引:1,自引:0,他引:1
Namocatcat JA Fang J Barcelona MJ Quibuyen AT Abrajano TA 《Journal of contaminant hydrology》2003,67(1-4):177-194
Evolution of trimethylbenzoic acids in the KC-135 aquifer at the former Wurtsmith Air Force Base (WAFB), Oscoda, MI was examined to determine the functionality of trimethylbenzoic acids as key metabolite signatures in the biogeochemical evolution of an aquifer contaminated with JP-4 fuel hydrocarbons. Changes in the composition of trimethylbenzoic acids and the distribution and concentration profiles exhibited by 2,4,6- and 2,3,5-trimethylbenzoic acids temporally and between multilevel wells reflect processes indicative of an actively evolving contaminant plume. The concentration levels of trimethylbenzoic acids were 3-10 orders higher than their tetramethylbenzene precursors, a condition attributed to slow metabolite turnover under sulfidogenic conditions. The observed degradation of tetramethylbenzenes into trimethylbenzoic acids obviates the use of these alkylbenzenes as non-labile tracers for other degradable aromatic hydrocarbons, but provides rare field evidence on the range of high molecular weight alkylbenzenes and isomeric assemblages amenable to anaerobic degradation in situ. The coupling of actual tetramethylbenzene loss with trimethylbenzoic acid production and the general decline in the concentrations of these compounds demonstrate the role of microbially mediated processes in the natural attenuation of hydrocarbons and may be a key indicator in the overall rate of hydrocarbon degradation and the biogeochemical evolution of the KC-135 aquifer. 相似文献
597.
In this study, organic pollutants in sandy soils are detected using a time domain relectrometry (TDR) probe system and eigendecomposition technique. As a demonstration, four types of organic fluids (motor oil, diesel oil, methanol and ethanol) were examined. Samples were prepared with different combinations of deionized water and organic fluid contents. For each experiment, reflected signals were captured by an oscilloscope, and their characteristics were identified using eigendecomposition technique. Autoregressive modeling and singular value decomposition methods were utilized for calculating the eigenvalues. The most significant eigenvalues were then identified based on their relative magnitude. Experimental results indicated that the presented system is sensitive to both water and pore fluid organic contents. For saturated conditions, signature curves were determined for identification of organic and/or water contents in soil pore fluids. 相似文献
598.
D. Melas H. D. Kambezidis J. L. Walmsley N. Moussiopoulos R. D. Bornstein O. Klemm D. N. Asimakopoulos F. A. Schiermeier 《Atmospheric environment (Oxford, England : 1994)》1995,29(24)
The NATO/CCMS Pilot Study “Air pollution transport and diffusion over coastal urban areas” held an international workshop in Athens, 3–5 May 1993. The objective of this workshop was to develop guidelines for it reference experiment in a coastal urban area. It was intended that the guidelines would be sufficiently general that they could be applied to any coastal urban area, but Athens was bome in mind as a suitable candidate location. On the first day of the workshop, invited speakers delivered their lectures on different issues of dispersion in urban coastal areas. The second day was devoted to discussions in working groups focusing on key issues, such as, emissions' inventory, meteorological measurements, surface pollutant concentration measurements, aircraft measurements, remote sensing and model evaluation. On the final half-day the rapporteur from each working group reported on its work. Their reports are briefly summarized in the present paper. 相似文献
599.
Major and trace elements in precipitation on Western Switzerland 总被引:1,自引:0,他引:1
Rain and snow samples from different sites, varying in altitude, in western Switzerland were taken from January 1990 to November 1991. The samples were collected with ultraclean material and analysed for the major elements Na, Cl, NO3, SO4, K, Si, Ca, Mg and the trace elements B, V, Cr, Mn, Ni, Fe, Zn, Cu, Pb, Rb, Sr, and Ba content. A comparison with published data shows that the measured concentration and fluxes are typical for slightly contaminated rural European regions. Analysis of variance suggests that the region is fairly homogeneous for atmospheric deposition although the sites differ in altitude and human influence. Enrichment factors indicate that most of the elements are originating from seawater or continental crust and that the elements released by human activities are submitted to long-range transport. Temporal evolution in concentrations and differences between rain and snow composition could originate from the general atmospheric circulation. 相似文献
600.
Adsorption and chlorination reactions for dibenzo-p-dioxin (DD) and 1-chlorodibenzo-p-dioxin (1-MCDD) on fly ash were characterized quantitatively using laboratory-based simulation of stack emissions with air and HCl-air atmospheres. Influences of contact time and temperature were studied and results showed behavior of DD and 1-MCDD consistent with that for 1,2,3,4-tetrachlorodibenzo-p-dioxin. Di-, tri-, and tetra-chlorinated dioxins were major compounds produced from heterogenous phase reactions of DD and 1-MCDD with HCl in air. Total conversion through reactions alone were as high as 81% and 58% respectively. 相似文献