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161.
Elevated particulate matter concentrations in urbanlocations have normally been associated with local trafficemissions. Recently it has been suggested that suchepisodes are influenced to a high degree by PM10sources external to urban areas. To further corroboratethis hypothesis, linear regression was sought betweenPM10 concentrations measured at eight urban sites inthe U.K., with particulate sulphate concentration measuredat two rural sites, for the years 1993–1997. Analysis ofthe slopes, intercepts and correlation coefficientsindicate a possible relationship between urban PM10and rural sulphate concentrations. The influences of winddirection and of the distance of the urban from the ruralsites on the values of the three statistical parametersare also explored. The value of linear regression as ananalysis tool in such cases is discussed and it is shownthat an analysis of the sign of the rate of change of theurban PM10 and rural sulphate concentrations providesa more realistic method of correlation. The resultsindicate a major influence on urban PM10 concentrations from the eastern side of the UnitedKingdom. Linear correlation was also sought using PM10 data from nine urban sites in London and nearby ruralRochester. Analysis of the magnitude of the gradients andintercepts together with episode correlation analysisbetween the two sites showed the effect of transportedPM10 on the local London concentrations. This articlealso presents methods to estimate the influence of ruraland urban PM10 sources on urban PM10 concentrations and to obtain a rough estimate of thetransboundary contribution to urban air pollution from thePM10 concentration data of the urban site. 相似文献
162.
Valentina Krysanova Frank Wechsung Alfred Becker Werner Poschenrieder Jan Gräfe 《Environmental Modeling and Assessment》1999,4(4):259-271
Hydrological processes and crop growth were simulated for the state of Brandenburg (Germany) using the hydrological/vegetation/water quality model SWIM, which can be applied for mesoscale river basins or regions. Hydrological validation was carried out for three mesoscale river basins in the area. The crop growth module was validated regionally for winter wheat, winter barley and maize. After that the analysis of climate change impacts on hydrology and crop growth was performed, using a transient 1.5 K scenario of climate change for Brandenburg and restricting the crop spectrum to the three above mentioned crops. According to the scenario, precipitation is expected to increase. The impact study was done comparing simulation results for two scenario periods 2022–2030 and 2042–2050 with those for a reference period 1981–1992. The atmospheric CO2 concentrations for the reference period and two scenario periods were set to 346, 406 and 436 ppm, respectively. Two different methods – an empirical one and a semi-mechanistic one – were used for adjustment of net photosynthesis to altered CO2. With warming, the model simulates an increase of evapotranspiration (+9.5%, +15.4%) and runoff (+7.0%, +17.2%). The crop yield was only slightly altered under the climate change only scenario (no CO2 fertilization effect) for barley and maize, and it was reduced for wheat (–6.2%, –10.3%). The impact of higher atmospheric CO2 compensated for climate-related wheat yield losses, and resulted in an increased yield both for barley and maize compared to the reference scenario. The simulated combined effect of climate change and elevated CO2 on crop yield was about 7% higher for the C3 crops when the CO2 and temperature interaction was ignored. The assumption that stomatal control of transpiration is taking place at the regional scale led to further increase in crop yield, which was larger for maize than for wheat and barley. The regional water balance was practically not affected by the partial stimulation of net photosynthesis due to higher CO2, while the introduction of stomatal control of regional transpiration reduced evapotranspiration and enlarged notably runoff and ground water recharge. 相似文献
163.
Stephen Chambal Mark Shoviak Alfred E. Thal Jr. 《Environmental Modeling and Assessment》2003,8(1):25-34
Value-focused thinking, a decision analysis technique, is used to produce a multiple-objective model that captures a site's municipal solid waste (MSW) management goals, objectives, and concerns in order to facilitate the evaluation of competing strategies. The model ranks competing MSW alternatives based on how well they meet the decision maker's strategic objective, a 20-year compliant MSW system. Sensitivity analysis is incorporated in the model to assess and illustrate the effects of changes in model objective weights and changes in model parameters. Overall, the model provides decision-makers with a decision tool to make a better decision when choosing a new MSW management strategy. The entire process is applied to a case study using Earekson Air Station, a remote U.S. Air Force installation. 相似文献
164.
Rainer Haas Alfred Krippendorf Torsten C. Schmidt Klaus Steinbach und Eberhard v. L?w 《Umweltwissenschaften und Schadstoff-Forschung》1998,10(5):289-293
Zusammenfassung Arsenkampfstoffe sind in der Umwelt persistent und kontaminieren bis heute Boden und Grundwasser. In diesem Beitrag werden
die chemischen Reaktionen der Arsenkamptstoffe Diphenylarsinchlorid (CLARK I), Phenylarsindichlorid (PFIFFIKUS), Ethylarsindichlorid
(DICK) sowie von Chlorvinylarsinverbindungen (LEWISITE) dargestellt. Die M?glichkeiten der chemisch-analytischen Erfassung
dieser chemischen Kampfstoffe als Originalsubstanzen und als Thiol-Derivate werden pr?sentiert.
相似文献
165.
166.
The Science of Nature - 相似文献
167.
Alfred Kühn 《Die Naturwissenschaften》1955,42(19):529-530
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