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251.
Jandl R Herman F Smidt S Butterbach-Bahl K Englisch M Katzensteiner K Lexer M Strebl F Zechmeister-Boltenstern S 《Environmental pollution (Barking, Essex : 1987)》2008,155(3):512-516
The dominant nitrogen (N) fluxes were simulated in a mountain forest ecosystem on dolomitic bedrock in the Austrian Alps. Based on an existing small-scale climate model the simulation encompassed the present situation and a 50-yr projection. The investigated scenarios were current climate, current N deposition (SC1) and future climate (+2.5 degrees C and +10% annual precipitation) with three levels of N deposition (SC2, 3, 4). The microbially mediated N transformation, including the emission of nitrogen oxides, was calculated with PnET-N-DNDC. Soil hydrology was calculated with HYDRUS and was used to estimate the leaching of nitrate. The expected change of the forest ecosystem due to changes of the climate and the N availability was simulated with PICUS. The incentive for the project was the fact that forests on dolomitic limestone stock on shallow Rendzic Leptosols that are rich in soil organic matter are considered highly sensitive to the expected environmental changes. The simulation results showed a strong effect due to increased temperatures and to elevated levels of N deposition. The outflux of N, both as nitrate (6-25kg Nha(-1)yr(-1)) and nitrogen oxides (1-2kg Nha(-1)yr(-1)), from the forest ecosystem are expected to increase. Temperature exerts a stronger effect on the N(2)O emission than the increased rate of N deposition. The main part of the N emission will occur as N(2) (15kg Nha(-1)yr(-1)). The total N loss is partially offset by increased rates of N uptake in the biomass due to an increase in forest productivity. 相似文献
252.
Steven M. Bromberg Gerald G. Akland John C. Puzak 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1073-1076
The Quality Control Branch of the Quality Assurance and Environmental Monitoring Laboratory, National Environmental Research Center, Research Triangle Park, N. C, coordinated a nationwide interlaboratory study which surveyed the ability of participating laboratories to analyze simulated ambient sulfur dioxide samples. The purposes of the study were (1) to provide participating laboratories with a means for self evaluation of their performance, and (2) to begin to acquire information which indicates the quality of ambient SO2 data being reported. Sample vials of sodium sulfite in mannitol were distributed to 134 laboratories throughout the country that routinely analyze for atmospheric SO2. No restrictions were placed on the method of analysis other than that the normal absorbing solution used with the analysis be a tetrachloromercurate II solution. Each sample set contained five separate vials. Each vial, when mixed properly with absorbing reagent, simulated a 24 hour bubbler sample. The range of concentrations in each set extended from approximately the lower detectable limit of the pararosaniline method to approximately the alert level as described in Federal Regulations. 相似文献
253.
Ulrike Hirt Judith Mahnkopf Mathias Gadegast Lukas Czudowski Ute Mischke Claudia Heidecke Gerald Schernewski Markus Venohr 《Regional Environmental Change》2014,14(3):1123-1138
We introduce an approach for establishing reference conditions (RC) for rivers of the German Baltic Sea catchment, based on predictive modelling. An extensive data set of statistics from the year 1880 was coupled with literature data, providing a comprehensive basis for the calculation of regional historical nutrient emissions into rivers, river nutrient concentrations, and nutrient loading into the sea. Four different scenarios were calculated: scenario 1 assumed RC following previously established criteria for lakes (Poikane et al. in Environ Manag 45(6):1286–1298, 2010), scenario 4 applied the nutrient emission conditions of 1880 (considering non-intensive land usage, the presence of tile drainage systems, sewer systems, and the human population from 1880), and scenarios 2 and 3 considered intermediate conditions. Our results showed that nutrient emissions from scenario 1 accounted for approximately one-tenth of the currently observed total nitrogen (TN) and total phosphorus (TP) emissions. The nutrient emissions calculated for 1880 (scenario 4) were found to be 47 % (TN) and 55 % (TP) higher than those calculated considering reference lake conditions (scenario 1). Our results suggest that RC nutrient concentrations in rivers in the German Baltic Sea catchment were clearly below 0.05 mg/l for TP and 1 mg/l for TN. This range is in accordance with historical and calculated pristine nutrient concentrations from other rivers in similar catchments. 相似文献
254.
255.
Anke Günther Gerald Jurasinski Vytas Huth Stephan Glatzel 《Environmental monitoring and assessment》2014,186(4):2151-2158
Closed chamber measurements for methane emission estimation are often carried out with opaque chambers to avoid heating of the headspace. However, mainly in wetlands, some plants possess an internal convective gas transport which quickly responds to changes in irradiation. These plants have also been found to often channel a large part of the released methane in temperate fens. We compare methane fluxes derived from transparent versus opaque chambers on Carex-, Phragmites-, and Typha-dominated stands of a temperate fen. Transparent chamber fluxes almost doubled opaque chamber fluxes in the convective transporting Phragmites stand. In Typha, a trend of higher fluxes determined with the transparent chambers was detectable, whereas in Carex, transparent and opaque chamber fluxes did not differ significantly. Thus, opaque chambers bias the outcome of methane measurements, depending on dominant vegetation. We recommend the use of transparent chambers when determining emissions of convective plants or extrapolating fluxes to larger scales. 相似文献
256.
Bian Liu Gerald J. Keeler J. Timothy Dvonch James A. Barres Mary M. Lynam Frank J. Marsik Joy Taylor Morgan 《Atmospheric environment (Oxford, England : 1994)》2010,44(16):2013-2023
Measurements of gaseous elemental mercury (GEM), particulate mercury (Hgp), and reactive gaseous mercury (RGM) were concurrently recorded at an urban site in Detroit and a rural site in Dexter, both in Michigan for the calendar year 2004. Their average concentrations (±standard deviation) for the urban area were 2.5 ± 1.4 ng m?3, 18.1 ± 61.0 pg m?3, and 15.5 ± 54.9 pg m?3, respectively, while their rural counterparts were 1.6 ± 0.6 ng m?3, 6.1 ± 5.5 pg m?3, and 3.8 ± 6.6 pg m?3, respectively. The medians of urban-to-rural ratios of Hg concentrations indicate approximately 1-fold, 2-fold, and 3-fold gradients between Detroit and Dexter for GEM, Hgp, and RGM, respectively. The urban–rural differences in Hg also varied considerably on different temporal scales and with wind flow patterns, which was most evident in RGM. Our results show that while Hg at both sites was impacted by regional sources, meteorological conditions, and photochemical transformations, the extent of variations in the observed urban-to-rural gradients, particularly in RGM, cannot be fully accounted for by these processes. Both analyses of the annual data and case studies indicate that the more variable and episodic nature of Hg, particularly RGM, seen in Detroit compared with Dexter, was the result of direct impact from local anthropogenic sources. 相似文献
257.
Schnitzer MI Monreal CM Jandl G Leinweber P Fransham PB 《Journal of environmental science and health. Part. B》2007,42(1):79-95
The initial chicken manure and the three fractions derived from it by fast pyrolysis, that is, the two biooils Fractions I and II as well as the residual char were analyzed by Curie-point pyrolysis-gas chromatography/mass spectrometry (Cp Py-GC/MS). The individual compounds identified were grouped into the following six compound classes: (a) N-heterocyclics; (b) substituted furans; (c) phenol and substituted phenols; (d) benzene and substituted benzenes; (e) carbocyclics; and (f) aliphatics. Of special interest were the relatively high concentrations of N-heterocyclics in biooil Fraction II which was obtained in the highest yield and had the highest calorific value. Prominent N-heterocyclics in biooil Fraction II were methyl-and ethyl-substituted pyrroles, pyridines, pyrimidine, pyrazines, and pteridine. Also noteworthy was the high abundance of aliphatics in biooil Fraction I and the char. The alkanes and alkenes in biooil Fraction I ranged from n-C7 to n-C18 and C7:1 to C18:1, respectively, and those in the char from n-C7 to n-C19 and C7:1 to C19:1, respectively. The N-heterocyclics in the two biooil Fractions came from the chicken manure, from proteinaceous materials during fast pyrolysis or were formed during the fast pyrolysis manure conversion by the Maillard reaction which involved the formation of N-heterocyclics by amino acids interacting with sugars. 相似文献
258.
Frank-Albert Pitten Gerald Müller Peter König Dieter Schmidt Axel Kramer 《Environmental Sciences Europe》1998,10(2):75-80
The risk assessment of former ammunition factories, where chemical weapons consisting of diphenylarsenic compounds have been produced or stored is difficult because of the lack of data concerning bioavailability and metabolism of the residues of these sternutators. In order to estimate the contamination of fodder plants by typical pollutants of the former Heeresmunitionsanstalt Löcknitz, the total concentration of arsenic was determined in 186 samples of wild plants. The total arsenic concentration in plants of high feed value did not exceed 1 ppm, whereas 15% of the samples of plants of middle and little value in regard to animal fodder showed arsenic concentrations above 1ppm. The uptake of arsenic by wild plants, however, appears to be comparably low taken the high-grade contamination of the soil into account. A final toxicological evaluation of the risk potential is not yet possible because it requires the characterization of the anorganic and organic arsenic compounds in these plants. 相似文献
259.
Yiran Gerald A. B. Stringer Lindsay C. Attua Emmanuel M. Evans Andrew J. Challinor Andy J. Gyasi Edwin A. 《Regional Environmental Change》2017,17(3):665-676
Regional Environmental Change - The interior savannah ecosystem in Ghana is subjected to a number of hazards, including droughts, windstorms, high temperatures and heavy rainfall. The frequency and... 相似文献
260.