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791.
大型梯级水库通常具有较大的调节库容,水库运行使坝下河道自然的流量过程受到较大扰动,一些具有重要生态意义的流量组的特征被改变,如洪水、高流量脉动、低流量和极端低流量。基于BRAIN等提出的河流生态流量影响研究理论,结合金沙江屏山断面的水文与河流生态的关系,选取水平年组对高流量脉动和极端低流量组的判别参数进行率定,确定自然条件下屏山断面生态流量组指标值。模拟金沙江下游梯级建成后的逐日流量过程,求得各生态流量组指标值并与自然条件下的指标值进行对比,分析金沙江下游“乌东德-白鹤滩-溪洛渡-向家坝”梯级水库建成后可能对屏山断面生态流量过程的影响。研究结果表明:建库后屏山断面将可能出现“极端低流量消失、低流量提高、高流量脉动散化、洪水基本保持”的变化特点. 相似文献
792.
基于物质流分析的江苏省区域生态效率评价 总被引:2,自引:0,他引:2
物质流分析被认为是适用于生态效率评价的重要工具和方法之一,但应用于区域生态效率评价的研究尚较少。根据生态效率理论、物质流分析理论与方法,建立了基于物质流账户的3个层面的区域生态效率评价指标:区域直接生态效率、区域总生态效率、整体生态效率。以江苏省为例,全面评价了 1995~2005年江苏省不同层面的生态效率,结果表明:(1)江苏省区域直接生态效率远高于我国同期水平。区域总生态效率和整体生态效率相对较低,分别仅为区域直接生态效率 15%~22%和 7%~8%左右;(2)1995~2005年,区域直接生态效率呈先上升后下降趋势,原因在于物质生产率未有显著提高以及近年来重工业在产业结构中比重的增加;(3)整体生态效率的变化趋势与区域直接生态效率类似,原因主要是近年江苏省对区外物质和资源的进口量显著增加;(4)区域总生态效率则表现为先快速上升后缓慢上升的趋势。在对研究结果及成因进行分析和讨论的基础上,提出了提高区域生态效率的建议. 相似文献
793.
Manfred Fehr 《Environment, Development and Sustainability》2009,11(2):319-328
As biodegradable material represents approximately 70% of household waste in Brazil, any strategy to divert appreciable waste
quantities from landfills of necessity has to include valorization and recycling of this material. A societal change of attitude
is required to perceive this challenge. Experiments in an urban apartment building are described that produced this change
of attitude with a success factor of 80%. Divided waste collection was implemented that separated at the source biodegradable
from inert material. Correct collection, handling and display procedures were established. Composting of biodegradable material
was carried out under the rooftop of the building as an alternative to using it as animal feed. Half of the inert material
entered the reverse logistics chain and was also diverted from the landfill. Waste related material flow through the building
is completely quantified, food intake and waste production are related, diversion of both biodegradable and inert waste components
from the landfill is measured and the composting process is described. The landfill diversion stands at 61%, mass reduction
through the composting process is 80% and matured compost is returned to residents for use in flower cages. The system has
been operational for two years and stands out as a precedent in successful decentralized household waste management supported
by material flow analysis.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
794.
In order to effectively conserve the non-renewable resource phosphorus (P), flows and stocks of P must be known at national, regional and global scales. P is a key non-renewable resource because its use as fertilizer cannot be substituted posing a constraint on the global food production in the long-term. This paper presents a methodology to establish country-wide P balances that emphasises resource use. We develop a material flow analysis (MFA) model that comprises all relevant flows and stocks of P in five subsystems, seven processes and 36 material flows. For quantification, statistical data from economic and agricultural sources as well as available information about P partitioning in natural and anthropogenic processes are used. Special attention is paid to data gaps and uncertainties. The model was tested in two case studies on P management in Turkey and Austria. MFA appears to be a tool well suited for establishing country-wide P balances, provided that national statistics are well-structured and accessible. If a common approach is used for modelling P-flows and stocks, regional and national balances can be compared and linked towards larger scale P balances for an improved management of the resource. 相似文献
795.
796.
采用穿透渗漏实验方法研究了经水泥固化的重金属废物的长期渗漏行为。用由Pb^2+、Zn^2+、Cu^2+、Ni^2+和Cr^6+5种重金属组成的合成废物样品进行2组实验。实验研究了渗漏实验液流速、PH的变化和金属渗漏能力对固体废物长期渗漏行为的影响。 相似文献
797.
F. Stagnitti G. Allinson M. Morita M. Nishikawa H. Il T. Hirata 《Environmental Modeling and Assessment》2000,5(4):229-236
Temporal moments analysis of solute breakthrough curves is used to investigate the preferential leaching of chloride, nitrate and phosphate through an Australian soil. Recent studies have shown that current models and methods do not adequately describe the leaching of nutrients through soil, often underestimating the risk of groundwater contamination by surface-applied chemicals, and overestimating the concentration of resident solutes. This inaccuracy results primarily from ignoring soil structure and non-equilibrium between soil constituents, water and solutes. Therefore simple models are required to accurately characterise solute transport in natural and agricultural soils under non-equilibrium conditions. A multiple sample percolation system, consisting of 25 individual collection wells was constructed to study the effects of localised soil heterogeneities on the transport of nutrients (NO3
–, Cl–, PO4
3
–) in the vadose zone of an agricultural soil predominantly dominated by clay. Using data collected from the multiple sample percolation experiments, this paper compares and contrasts the performance of temporal moments analysis with two mathematical models for predicting solute transport, the advective-dispersion model with a reaction term (ADR) and a two-region preferential flow model (TRM) suitable for modelling preferential transport. The values for solute transport parameters predicted by temporal moments analysis were in excellent agreement with experimental data and results from ADR and TRM. It is concluded that temporal moments analysis when applied with other physical models such as the ADR and TRM, provide an excellent means of obtaining values for important solute transport parameters and gaining insight of preferential flow. These results have significant ramifications for modelling solute transport and predicting nutrient loadings. 相似文献
798.
799.
An approach is developed to simulate leaching of a dissolved chemical constituent in the vadose zone of an aquifer. Specifically,
nitrate loading at the water table for different water table depths, for a range of aquifer permeability values, and for different
cases of heterogeneity of the aquifer, are considered. Models from the literature are first used to derive soil–water characteristic
curves (water retention and hydraulic conductivity) from a grain size distribution curve for unsaturated conditions. Given
infiltration from the surface, the initial conditions for the chemical concentration, and the water content profile, leaching
of the chemical in the vadose zone is simulated as a function of both time and depth. The methodology is illustrated for a
permeable aquifer. Simulations are undertaken using a finite element code for saturated and unsaturated flow. Different scenarios
are simulated depending on the heterogeneity of the aquifer and the depth of the water table. Modeling results show that in
the example case studied, nitrate concentration loading at the water table does not depend strongly on the position of the
water table, but rather on the material properties of the aquifer. The contribution of this endeavor resides in the methodology
which allows a prediction of nitrate leaching using only the grain size property of the aquifer. It allows practitioners to
obtain a first assessment of leaching with limited data. 相似文献
800.
崂山风景区旅游环境容量研究 总被引:5,自引:0,他引:5
通过对历年游客流量调查,分析了崂山风景区客流时间和空间分布特征。计算了景区9条步道游线,3条索道和7个人文景观区的日容量、月容量和年容量,并分析了景区旅游环境容量的利用强度,发现2004年景区各条步道游线、各条索道和各个人文景观区的日、月、年容量利用强度均为适载,但第一、第二和第三高峰日已严重超载。最后,制定了游客流量宏观调控对策及微观调控措施。 相似文献