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91.
Jan Willem Erisman Arjan Hensen Wim de Vries Hans Kros Tamme van de Wal Wim de Winter Jan Erik Wien Mark v. Elswijk Matthijs Maat Kaj Sanders 《Ambio-人类环境杂志》2002,31(2):190-196
利用计算机模拟的方法,我们为第二届国际氮会议研制开发了一个游戏形式的氮决策支持系统.研制这一系统的目的是:①使科学工作者和决策者们都能认识到荷兰氮污染问题的复杂性,因为荷兰是一个农业、工业和运输业活动密集的区域;②探索以最低的社会经济代价解决氮污染的最佳方案.NitroGenius由有关时空范围内的氮流动模型组成,其中包括氨和氮氧化合物的释放及其对地表水和地下水的污染.NitroGenius中还包括了一个经济模型,它描述了各个重要经济部门之间的关系,以及不同氮排放控制措施对国民生产总值(GDP)、失业率、能源消耗和环境的影响.在第二次国际氮会议期间,大约有50个研究组对NitroGenius进行了测试,结果表明,如果认真进行计划并选择适当的治理措施,就能够以适当的代价解决荷兰的氮污染问题. 相似文献
92.
The rain forests of Tanzania occupy small areas, mostly confined to isolated mountains. Except for some isolated volcanic mountains (Mt. Kilimanjaro, Mt. Meru, the Ngorongoro Crater), most of the rain forests are confined to the so-called Eastern Arc mountains with old crystalline bedrocks. The Eastern Arc rain forests are characterized by high biodiversity, and have large numbers of endemic and rare taxa of plants and animals. The submontane and montane rain forests are extremely important water catchments, providing water for major cities and densely populated rural areas. Most of the rain forest catchments are forest reserves, but still the human impact around and inside the reserves is considerable. Intensive cultivation due to heavy population pressure affects the reserves from all sides, leaving the forests isolated, fragmented ‘islands’ surrounded by the cultural landscape. Former timber production and logging programs initiated by the State and some foreign development organizations have depleted large areas of rain forests, e.g. in the Usambara Mountains. Extensive, destructive, legal and illegal activities such as, e.g. logging, pit-sawing and grazing have taken place inside most of the forest reserves. Some research programs on rain forest catchments are now being carried out in Tanzania, forming a basis for future management and monitoring of the forest reserves. The forest authorities are currently much concerned about the problems, giving catchment forest management highest priority in the Tropical Forestry Action Plan. 相似文献
93.
Theoretical study of invasion dynamics has suggested that spatial heterogeneity should strongly influence the rate and extent of spreading organisms. However, empirical support for this prediction is scant, and the importance of understanding heterogeneity for real-world systems has remained ambiguous. This study quantified the influence of host and environmental heterogeneity on the dynamics of a 19-year disease invasion by the exotic and fatal pathogen, Phytophthora lateralis, within a stream population of its host tree, Port Orford cedar (Chamaecyparis lawsoniana). Using dendrochronology, we reconstructed the invasion history along a 1350-m length of infected stream, which serves as the only route of pathogen dispersal. Contrary to theoretical predictions, the temporal progression of the disease invasion was not related to a host's downstream spatial position, but instead was determined by two sources of heterogeneity: host size and proximity to the stream channel. These sources of heterogeneity influenced both the epidemic and endemic dynamics of this pathogen invasion. This analysis provides empirical support for the influence of heterogeneity on the invasion dynamics of a commercially important forest pathogen and highlights the need to incorporate such natural variability into both invasion theory and methods aimed at controlling future spread. 相似文献
94.
A submodel for anaerobic mud-water exchange of phosphate is obtained from experiments in the laboratory. Phosphorus in the sediment can be divided into exchangeable and non-exchangeable phosphorus. The exchangeable phosphorus is decomposed in accordance with a first-order reaction. The phosphorus moves, after the decomposition process, from the interstitial water to the water phase, in accordance with a diffusion expression. The yearly increase of the sediment was determined by means of the lead concentration as a function of the depth. 相似文献
95.
A model for the accumulation of CO2 in the atmosphere has been set up, taking into consideration: (1) the global cycle of nitrogen and phosphorus: (2) the CO2-diffusion in the oceans with means of a multilayer ?ea model; (3) the ability of the oceans to take up CO2; (4) the influence of the CO2-concentrations and of the temperature on this ability; (5) different growth rates for the consumption of fossil fuel including logistic growth; (6) the natural climatic variation.It is shown to be essential to include all these factors. The inclusion of factors (4) and (6), which have been omitted in many previous publications, is very essential to the model. 相似文献
96.
97.
Luc A. Wauters Simon A. de Crombrugghe Nadia Nour Erik Matthysen 《Behavioral ecology and sociobiology》1995,37(3):189-193
In polygynous roe deer Capreolus capreolus, males are only slightly heavier than females and the overall sex ratio at birth is close to unity. We studied offspring sex ratio and litter size (range 1–4, n = 74) of culled females, in utero, which provided an opportunity to examine responses of sex ratio to maternal condition. Male embryos were heavier than their sisters, and male fawns (9 months old) heavier than female fawns, suggesting a higher growth rate in males. There was no evidence for differential mortality between the sexes from birth to 9 months old. Heavier adult females produced larger embryos than lighter, or primiparous females. The overall sex ratio of embryos did not differ from unity, but adult does had more male embryos (55%) than primiparous does (32%), and the proportion of male embryos in a litter increased with the mother's body mass. Litter size also tended to increase with maternal age and body mass. We argue that this pattern reflects adaptive variation in offspring sex ratio. 相似文献
98.
Gunschera J Fuhrmann F Salthammer T Schulze A Uhde E 《Environmental science and pollution research international》2004,11(3):147-151
GOAL, SCOPE AND BACKGROUND: Complaints by residents of frame-houses about musty odour in the houses has become an increasing problem within the last years. An additional problem is that the odour is transferred to clothes and skin. The persons themselves do not recognize the smell after a while because of adaptation. Serious social problems are the result. For a long time, the smell was explained to be from mould due to construction-based humidity problems. However, in an increasing number of houses, no indications were found for elevated levels of mould growth. METHODS: Air and material samples were taken from 5 houses, which show typical musty odours, and analysed with respect to chlorophenols and chloroanisoles. Additionally, some samples were analysed for lindane and its metabolites, because lindane was commonly used together with pentachlorophenol (PCP) for wood protection. RESULTS AND DISCUSSION: Meticulous analysis resulted in the identification of chloroanisoles, mainly 2,3,4,6-tetrachloroanisole. These substances are known from corky wines and from contamination of food from pentachlorophenol (PCP) treated pallets and result from microbiological metabolic processes. Pentachlorophenol was commonly used to protect wood from fungi in Germany mainly in the later 60s and 70s. Details of these processes, as well as effective methods to identify chloroanisoles in the problem houses, are described. CONCLUSIONS: Chloroanisoles formed by metabolism of PCP have been well known to contaminate food or wine. Here, they were identified and are probably responsible for the musty odours in the frame houses. Since it is quite clear that these substances were not components of building materials used in the houses, an explanation for chloroanisole formation is proposed. Localized dampness probably favours microbial growth associated with metabolic conversion of chlorophenols to the corresponding chloroanisoles, primarily 2,3,4,6-tetrachloroanisol, which spread throughout the buildings, resulting in the observed odours. RECOMMENDATIONS AND OUTLOOK: The group of chloroanisoles has been recognized as important indoor pollutants as they possess musty odours at extremely low concentrations, e.g. for 2,4,6-trichloroanisole in a range of 5-10 ppt in air (Staples 2000). On the basis of currently available toxicological data, exposure of the occupants to the concentrations of chloroanisoles measured is not associated with a health risk. No correlation could be observed between concentrations of chloroanisoles and PCP in house dust and indoor air. However, chloroanisoles are good indicators for possible PCP-treatment of wood in frame houses and their detection should initiate investigations on PCP contamination. Research is continuing to identify the microorganisms involved and to devise a remediation procedure for affected houses. 相似文献
99.
Priming effects on PAH degradation and ecotoxicity during a phytoremediation experiment 总被引:4,自引:0,他引:4
Joner EJ Hirmann D Szolar OH Todorovic D Leyval C Loibner AP 《Environmental pollution (Barking, Essex : 1987)》2004,128(3):429-435
An experiment was conducted to distinguish priming effects from the effects of phytoremediation of a creosote-polluted soil. The concentration of 13 polycyclic aromatic hydrocarbons (PAHs), and their combined soil toxicity (using four bioassays), was determined on recently excavated, homogenized soil and on such soil subjected to a time-course phytoremediation experiment with lucerne. The results showed a high priming effect, with minor positive and synergistic effects of planting and fertilization on PAH degradation rates. At the end of the experiment, PAH degradation reached 86% of the initial 519 mg PAHs kg(-1). Two of the four toxicity tests (bioluminescence inhibition and ostracod growth inhibition) corroborated the chemical data for residual PAHs, and indicated a significant reduction in soil toxicity. We conclude that priming effects can easily surpass treatment effects, and that an unintentional pre-incubation that ignores these effects can jeopardize the full quantitative assessment of in situ bioremediation of contaminated soil. 相似文献
100.