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981.
运用美国ISC3模型对北京京丰热电有限责任公司现状及采用电子束氨法烟气脱硫后的SO2和NOx排放对环境空气质量的影响进行了模拟.结果表明:该公司现状SO2排放的主要受影响地区在丰台西部和房山北部,石景山和门头沟南部局部地区也受到一定影响,对老城区的影响很小,SO2年均质量浓度最大值为6.10 μg/m\+3,占二级标准的10.2%,NOx的影响区域与SO2相似,年均质量浓度最大值为4.27 μg/m\+3,占二级标准的5.3%;采用电子束氨法脱硫技术后,燃煤含硫量分别为0.79%,2%和0.5%的情况下,SO2年均质量浓度最大值分别降到0.86,2.17,0.55 μg/m\+3,比现状降低了86%,64%,91%,NOx年均质量浓度最大值降到了3.42 μg/m3,比现状降低了20%. 相似文献
982.
The aim of this study is to empirically illustrate the importance of taking movement constraints into account when testing for habitat selection with telemetry data. Global Positioning System relocations of two Scandinavian brown bears were used to compare the results of two different tests of habitat selection by the bears within their home range. Both relied on the comparison of observed dataset with datasets simulated under the hypothesis of random habitat use. The first analysis did not take movement constraints into account (simulations were carried out by randomly distributing a set of points in the home range) whereas the second analysis accounted for these constraints (simulations were carried out by building random trajectories in the home range). The results for the two analyses showed contrasted results. Therefore, not accounting for movement constraints in analyses may result in a misleading biological interpretation. Autocorrelation between relocations is not undesirable: it contains information about ecological processes that should be integrated in habitat selection analyses. 相似文献
983.
This paper is to show that most discrete models used for population dynamics in ecology are inherently pathological that their predications cannot be independently verified by experiments because they violate a fundamental principle of physics. The result is used to tackle an on-going controversy regarding ecological chaos. Another implication of the result is that all dynamical systems must be modeled by differential equations. As a result it suggests that researches based on discrete modeling must be closely scrutinized and the teaching of calculus and differential equations must be emphasized for students of biology. 相似文献
984.
Incorporating anthropogenic variables into a species distribution model to map gypsy moth risk 总被引:1,自引:0,他引:1
Christopher D. Lippitt John Rogan James Toledano Florencia Sangermano J. Ronald Eastman Victor Mastro Alan Sawyer 《Ecological modelling》2008
This paper presents a novel methodology for multi-scale and multi-type spatial data integration in support of insect pest risk/vulnerability assessment in the contiguous United States. Probability of gypsy moth (Lymantria dispar L.) establishment is used as a case study. A neural network facilitates the integration of variables representing dynamic anthropogenic interaction and ecological characteristics. Neural network model (back-propagation network [BPN]) results are compared to logistic regression and multi-criteria evaluation via weighted linear combination, using the receiver operating characteristic area under the curve (AUC) and a simple threshold assessment. The BPN provided the most accurate infestation-forecast predictions producing an AUC of 0.93, followed by multi-criteria evaluation (AUC = 0.92) and logistic regression (AUC = 0.86) when independently validating using post model infestation data. Results suggest that BPN can provide valuable insight into factors contributing to introduction for invasive species whose propagation and establishment requirements are not fully understood. The integration of anthropogenic and ecological variables allowed production of an accurate risk model and provided insight into the impact of human activities. 相似文献
985.
Simulations provide an opportunity to examine how single or multiple perturbations may impact a specific species. The objectives of this study were to identify thresholds at which changes in stream peak flow, stream base flow, and/or chytrid fungus presence alter long-term Rana chiricahuensis populations. We used scenarios with varying peak flow mortality rates, base flow mortality rates, and chytrid fungus mortality rates. Sensitivity analysis was also conducted. Over 50 years, populations in six scenarios increased and 13 scenarios decreased. Eight scenarios resulting with fewer than 100 individuals included stochastic effects for at least two of three perturbations and the remaining scenarios included chronic effects of 30% or higher. Scenarios with population increases had either no chytrid fungus effect or chronic effects from perturbations totaling less than 30%. In the absence of chytrid fungus, populations increased and became stable. At a 10% annual death rate caused by chytrid fungus, the R. chiricahuensis population decreased 46.8%. At a 20% death rate, the population decreased 98.6%. Model scenarios were sensitive to peak flow death rates. As peak flow mortality increased to 10 and 20%, extinction rates increased to 91.7 and 99.9%, respectively. With model parameters and the no base flow mortality, R. chiricahuensis populations declined by 92% with a 3.2% extinction rate at 50 years. Models with base flow mortality rates of 10 and 20% resulted in population extinction rates of 48.7 and 96.1%, respectively. Scenario analysis of perturbations on a hypothetical R. chiricahuensis population provided a framework in which to view combined effects on a species. Analysis supports supposition that chytrid fungus is the proximate cause of many amphibian declines, but the added effect of base flow and peak flow has the potential to hasten declines. 相似文献
986.
Effects of land use on concentrations of metals in surface soils and ecological risk around Guanting Reservoir,China 总被引:7,自引:0,他引:7
Luo W Lu Y Giesy JP Wang T Shi Y Wang G Xing Y 《Environmental geochemistry and health》2007,29(6):459-471
It is accepted that the historical routine use of agrochemicals may have resulted in undesirable concentrations of metals
in the environment. To investigate and assess the effects of land use on concentrations of heavy metals around the Guanting
Reservoir in China, 52 surface soil samples (depth of 2–10 cm) were taken from areas where four types of land use were practiced
(including arable land, woodland, bare land, orchard land). The metals and metalloids (As, Cr, Ni, Cu, Zn, Cd, and Pb) were
analyzed using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Significant accumulation of As, Cd, and
Cr was found in soils of arable land. Based on correlation and cluster analysis, it can be concluded that Cd and Zn originate
mainly from phosphate fertilizer, Pb from the use of insecticides, fertilizers, and sewage sludge as well as air deposition,
and Cu from copper-based fungicides, while As, Ni and Cr might come from parent soil material. According to an ecological
risk analysis of metals based on the ecological index suggested by Hakanson, the four types of land can be ranked by severity
of ecological risk as follows: arable land > woodland > bare land > orchard land, with a high ecological risk of Cd for all
four types. Management measures for land use planners for avoiding water, soil, and sediment pollution caused by metals around
the Guanting Reservoir are presented. 相似文献
987.
988.
河流生态基流量整合计算模型 总被引:19,自引:2,他引:17
针对北方地区流域水域生态系统人工化明显和河流断流的现状,提出了河流生态基流量的概念,并分析了其内涵.河流生态基流量包括河道生态基流量、河口生态基流量和湿地生态基流量.河流生态基流量计算应考虑流域内不同水系、不同河段生态环境的差异性和时空变化规律.通过改进生态环境需水量的计算方法,分析河流的空间结构特征、各河段的相互关系以及流域的水特征,提出了整合计算模型.整合计算模型分为2类:不同水系和同一水系的整合.同一水系整合计算模型又分为:河流生态基流量整合模型、河流与湿地生态基流量的整合以及河道生态基流量的整合模型.其中最为复杂的河道生态基流量的整合模型共分为6种形式:简单式、汇流式、分流式、组合式、交叉式和河口式.研究结果表明:各子系统的生态基流量是河流生态基流量整合计算的基础;河流生态基流量保证系数是计算的重要参数,其值在确定基数的基础上,通过恢复模式和空间优化配置这2个影响因子进行调整而得到,取值范围为[0,1];整合计算模型需要明确消耗性生态基流量和非消耗性生态基流量,消耗性生态基流量不受保证系数的影响,非消耗性生态基流量因保证系数取值的不同而变化. 相似文献
989.
Control of sludge age and mixed liquid suspended solids concentration in the activated sludge process is critical for ensuring effective wastewater treatment. A nonlinear dynamic model for a step-feed activated sludge process was developed in this study. The system is based on the control of the sludge age and mixed liquor suspended solids in the aerator of last stage by adjusting the sludge recycle and wastage flow rates respectively. The simulation results showed that the sludge age remained nearly constant at a value of 16 d in the variation of the influent characteristics. The mixed liquor suspended solids in the aerator of last stage were also maintained to a desired value of 2500 g/m^3 by adjusting wastage flow rates. 相似文献
990.