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101.
Income and distance-decay effects on willingness to pay estimated by the contingent valuation method
Jongyearn Lee 《Journal of Environmental Planning and Management》2016,59(11):1957-1981
This study suggests a methodology for enhancing accuracy in evaluating amenity by the contingent valuation method when household's willingness to pay (WTP) is dependent to its income and the distance between a respondent's residence and the location of a target facility. Using a linear city model, this study demonstrates the influences of income and distance-decay effects on WTP. Simulations are performed to check the validity of the model, as well as to predict consequences when income and distance-decay effects are not properly treated. Finally, the suggested methodology is applied to two real cases. The estimation results from a structural model show that the calculated total benefit varies largely when income and distance-decay effects exist and are ignored. Also, an ad hoc model generates significantly different estimates from the utility difference model this study adopted. The difference in estimates suggests that the total benefit has to be estimated by a structural model. 相似文献
102.
Naveen K. Shrivastava Shashikant B. Thombre Kailas L. Wasewar 《International Journal of Green Energy》2016,13(2):213-228
In order to understand the complex transport phenomena in a passive direct methanol fuel cell (DMFC), a theoretical model is essential. The analytical model provides a computationally efficient framework with a clear physical meaning. For this, a non-isothermal, analytical model for the passive DMFC has been developed in this study. The model considers the coupled heat and mass transport along with electrochemical reactions. The model is successfully validated with the experimental data. The model accurately describes the various species transport phenomena including methanol crossover and water crossover, heat transport phenomena, and efficiencies related to the passive DMFC. It suggests that the maximum real efficiency can be achieved by running the cell at low methanol feed concentration and moderate current density. The model also accurately predicts the effect of various operating and geometrical parameters on the cell performance such as methanol feed concentration, surrounding temperature, and polymer electrolyte membrane thickness. The model predictions are in accordance with the findings of the other researchers. The model is rapidly implementable and can be used in real-time simulation and control of the passive DMFC. This comprehensive model can be used for diagnostic purpose as well. 相似文献
103.
三峡库区重庆段土壤保持服务时空分布格局研究 总被引:4,自引:0,他引:4
土壤保持是生态系统服务与功能的重要组成,在防止土壤侵蚀、减少径流泥沙与农业面源污染等方面具有至关重要的作用。以对国家生态安全具有重要作用的土壤保持生态功能区——三峡库区重庆段为研究区域,研究得到了2000~2013年时间序列区域土壤保持服务"流量"结果,结果表明:(1)三峡库区重庆段多年平均土壤保持量为604.39 t/hm~2·a,沿长江干流自西向东逐渐增强,区域差异显著;(2)三峡库区的土壤保持服务存在明显的垂直分异特征,随着高程的增加,以300 m与900 m为节点,出现递减-递增-递减的分段规律,与人类活动存在明显的相关关系;(3)增加森林覆被面积是改善区域土壤保持、减少水土流失的重要举措。同时,在三峡库区开展坡改梯工程,减少坡耕地的数量能够有效控制区域水土流失; 相似文献
104.
农业机械化、非农就业与农民的承包地退出意愿 总被引:2,自引:0,他引:2
刘同山 《中国人口.资源与环境》2016,(6):62-68
工业化和城镇化必然要求部分农民与农村土地"人地分离",农业生产方式的转变加快了上述进程。理论分析表明,农业机械的广泛使用,不仅可能对农民的承包地退出意愿直接产生正负两种作用,还可能会通过非农就业这一中介变量间接影响农民的退地意愿。为了考察当前我国农民的农村土地退出意愿以及农业机械化、非农就业对其造成的影响,本文首先采用两阶段随机抽样法,对河北、山东、河南三省九县(市、区)620个农户进行了问卷调查,发现相当一部分农民愿意有偿退出农村承包地,且对不同的退出方式有不同的选择偏好。利用上述农户调查数据,本文将农村承包地退出划分为"换工资收入"、"直接出售"和"被政府征用"三种具体方式,通过构建mvprobit模型,计量分析了农业机械化、非农就业与农民的承包地退出意愿之间的联系。研究发现,农业机械使用比例的提高会强化农民以承包地换养老保险等工资性收入的意愿,而农民对农机作业服务满意程度的提升,则会抑制其直接出售承包地或用之换养老保险等工资性收入的意愿。整体来看,农业机械化对农民"弃地进城"有显著的积极作用。非农就业是农业机械化影响农民退地意愿的中介变量,但它对退地意愿的作用不显著。成员非农就业较稳定的农户家庭,更愿意以一次性卖断(直接出售或被政府征用)的方式处置承包地。为了避免陷入"日韩陷阱",推动农业转型发展和农民市民化,需要实施农民的承包地退出制度,尽快为有意愿、有能力的进城农户彻底放弃农村土地提供制度出口。 相似文献
105.
国外流域管理的成功经验对雅砻江流域管理的启示 总被引:2,自引:0,他引:2
世界各国对流域管理的不断探索,大大丰富了流域管理的理论和实践,流域管理已成为国家和地区水资源管理的一种行之有效的模式。我国的流域管理尚处于最初的探索阶段,如何借鉴国外流域管理的成功经验,形成有效的流域管理模式已成为我国水资源管理的主要任务之一。为了给国内流域管理实践提供一些有益的借鉴,分析总结了具有代表性的美国田纳西河流域管理模式、澳大利亚墨累 达令河流域管理模式和英国泰晤士河流域管理模式的成功经验和存在的问题。以雅砻江流域水电开发为实例,在对该流域的实际情况进行全面分析的基础上,将该流域与上述三条流域进行比较,充分借鉴三条流域管理模式成功经验,提出了雅砻江流域管理的相关对策和建议。 相似文献
106.
Long-range atmospheric transport of three toxaphene congeners across Europe. Modeling by chained single-box FATEMOD program 总被引:1,自引:1,他引:0
Jaakko Paasivirta Seija Sinkkonen Vladimir Nikiforov Fedor Kryuchkov Erkki Kolehmainen Katri Laihia Arto Valkonen Manu Lahtinen 《Environmental science and pollution research international》2009,16(2):191-205
Background, aims, and scope Since toxaphene (polychlorocamphene, polychloropinene, or strobane) mixtures were applied for massive insecticide use in the
1960s to replace the use of DDT, some of their congeners have been found at high latitudes far away from the usage areas.
Especially polychlorinated bornanes have demonstrated dominating congeners transported by air up to the Arctic areas. Environmental
fate modeling has been applied to monitor this phenomenon using parallel zones of atmosphere around the globe as interconnected
environments. These zones, shown in many meteorological maps, however, may not be the best way to configure atmospheric transport
in air trajectories. The latter could also be covered by connecting a chain of simple model boxes. We aim to study this alternative
approach by modeling the trajectory chain using catchment boxes of our FATEMOD model. Polychlorobornanes analyzed in biota
of the Barents Sea offered one case to study this modeling alternative, while toxaphene has been and partly still is used
massively at southern East Europe and around rivers flowing to the Aral Sea.
Materials and methods Pure model substances of three polychlorobornanes (toxaphene congeners P26, P50, and P62) were synthesized, their environmentally
important thermal properties measured by differential scanning calorimetry, as evaluated from literature data, and their temperature
dependences estimated by the QSPR programs VPLEST, WATSOLU, and TDLKOW. The evaluated property parameters were used to model
their atmospheric long-range transport from toxaphene heavy usage areas in Ukraine and Aral/SyrDarja/AmuDarja region areas,
through East Europe and Northern Norway (Finnmarken) to the Barents Sea. The time period used for the emission model was June
1997. Usual weather conditions in June were applied in the model, which was constructed by chaining FATEMOD model boxes of
the catchment’s areas along assumed maximal air flow trajectories. Analysis of the three chlorobornanes in toxaphene mixtures
function as a basis for the estimates of emission levels caused by its usage. High estimate (A) was taken from contents in
a Western product chlorocamphene and low estimate (B) from mean contents in Russian polychloroterpene products to achieve
modeled water concentrations. Bioaccumulation to analyzed lipid of aquatic biota at the target region was estimated by using
statistical calculation for persistent organic pollutants in literature.
Results The results from model runs A and B (high and low emission estimate) for levels in sea biota were compared to analysis results
of samples taken in August 1997 at Barents Sea. The model results (ng g−1 lw): 4–95 in lipid of planktovores and 7–150 in lipid of piscivores, were in fair agreement with the analysis results from
August 1997: 21–31 in Themisto libellula (chatka), 26–42 in Boreocadus saida (Polar cod), and 5–27 in Gadus morhua (cod) liver.
Discussion The modeling results indicate that the application of chained simple multimedia catchment boxes on predicted trajectory is
a useful method for estimation of volatile airborne persistent chemical exposures to biota in remote areas. For hazard assessment
of these pollutants, their properties, especially temperature dependences, must be estimated by a reasonable accuracy. That
can be achieved by using measurements in laboratory with pure model compounds and estimation of properties by thermodynamic
QSPR methods. The property parameters can be validated by comparing their values at an environmental temperature range with
measured or QSPR-estimated values derived by independent methods. The chained box method used for long-range air transport
modeling can be more suitable than global parallel zones modeling used earlier, provided that the main airflow trajectories
and properties of transported pollutants are predictable enough.
Conclusions Long-range air transport modeling of persistent, especially photo-resistant organic compounds using a chain of joint simple
boxes of catchment’s environments is a feasible method to predict concentrations of pollutants at the target area. This is
justified from model results compared with analytical measurements in Barents Sea biota in August 1997: three of six modeled
values were high and the other three low compared to the analysis results. The order of magnitude level was similar in both
modeled (planktovore and piscivore) and observed (chatka and polar cod) values of lipid samples. The obtained results were
too limited to firm validation but are sufficient to justify feasibility of the method, which prompts one to perform more
studies on this modeling system.
Recommendations and perspectives For assessment of the risk of environmental damages, chemical fate determination is an essential tool for chemical control,
e.g., for EU following the REACH rules. The present conclusion of applicability of the chained single-box multimedia modeling
can be validated by further studies using analyses of emissions and target biota in various other cases. To achieve useful
results, fate models built with databases having automatic steps for most calculations and outputs accessible to all chemical
control professionals are essential. Our FATEMOD program catchments at environments and compound properties listed in the
database represent a feasible tool for local, regional, and, according our present test results, for global exposure predictions.
As an extended use of model, emission estimates can be achieved by reversed modeling from analysis results of samples corresponding
to the target area.
This article is dedicated to the memory of Professor Alexander B Terentiev (who passed away in November 2006), our true friend.
With his Institute of Organo-Element Compounds, Russian Academy of Science, Moscow, he was an important main organizer of
the six joint Finnish–Russian seminars (every third year since 1989) on the field (‘Chemistry and Ecology of Organo-Element
Compounds’). He prompted us especially to search properties and environmental fates for various polyhalogen compounds. We
remember him for his friendly character and great sense of humor. 相似文献
107.
The wide application of new information and communication technologies (ICTs) has been argued to be critical to business success of small and medium-sized enterprises (SMEs), especially to those in the developing countries. Drawing upon existing literature, this article will examine the determinants of ICTs application in SMEs in China based on data collected from interviews with top managers and/or owners of 70 SMEs. We identify 20 factors affecting ICTs application in SMEs in China and divide them into four broad categories, namely pressures, firm specific factors, technical factors and local milieu. We also pay special attention to the Chinese business environment affecting ICTs application. Our analysis shows that local ICT infrastructure, external pressures from competitors and ICT knowledge of employees are the determinants of Internet application by SMEs, while product characteristics and market target are important factors of e-commerce adoption. 相似文献
108.
Model evaluation of the phytoextraction potential of heavy metal hyperaccumulators and non-hyperaccumulators 总被引:3,自引:0,他引:3
Hong-Ming Liang Jeng-Min Chiou 《Environmental pollution (Barking, Essex : 1987)》2009,157(6):1945-1952
Evaluation of the remediation ability of zinc/cadmium in hyper- and non-hyperaccumulator plant species through greenhouse studies is limited. To bridge the gap between greenhouse studies and field applications for phytoextraction, we used published data to examine the partitioning of heavy metals between plants and soil (defined as the bioconcentration factor). We compared the remediation ability of the Zn/Cd hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri and the non-hyperaccumulators Nicotiana tabacum and Brassica juncea using a hierarchical linear model (HLM). A recursive algorithm was then used to evaluate how many harvest cycles were required to clean a contaminated site to meet Taiwan Environmental Protection Agency regulations. Despite the high bioconcentration factor of both hyperaccumulators, metal removal was still limited because of the plants' small biomass. Simulation with N. tabacum and the Cadmium model suggests further study and development of plants with high biomass and improved phytoextraction potential for use in environmental cleanup. 相似文献
109.
110.