首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 109 毫秒
1.
The adsorption behaviour of Diphenylamine (DPAM), napthylamine ( NAM), napthylamine ( NAM)and aniline on pyrolusite and activated carbon has been studied.Pyrolusite shows remarkable sorption capacity for DPAM and NAM as compared to aniline; (the adsorption followed theorder:Activated Carbon: DPAM = NAM > AnilinePyrolusite: DPAM: NAM > NAM> Aniline)The maximum adsorption of NAM occurred in theconcentration range 4–20 g mL-1 on pyrolusite (95%)and 4–50 g mL-1 on activated carbon (100%). Theeffect of various doses of activated carbon on the adsorption of NAM confirm Langmuir and Freundlich isotherms where asFreundlich isotherm is obeyed by pyrolusite. The adsorption of NAM on both the absorbents is not affected in presence ofDPAM over a wide range of their initial concentrations (20–60g mL-1). The desorption studies of NAM onpyrolusite was carried out by batch as well as column processes.Excellent results were obtained when a mixture of n-hexane andisopropanol (91:1) was used as eluent.  相似文献   

2.
Although exposure assessments cannot be completed remotely, remote sensing techniques provide an invaluable adjunct in exposure monitoring programs. Exposure can be defined as the summation over time, in all media, of the amount of a pollutant available at the exchange boundaries of the receptor during a specified period. This paper describes a few remote monitoring techniques that provide direct measurement input into an exposure assessment and several that furnish quantitative or qualitative information leading to decisions regarding how to monitor, such that the source-exposure-dose relationships can be fully defined. Two general classes of remote sensing systems are included in this discussion-passive and active. Passive systems depend on a measurement of the energy reflected or emitted by a target and active systems use an energy source, e.g., a laser to perform the environmental interrogation. Airborne as well as ground-based remote monitoring measurements or systems are also considered in this paper.  相似文献   

3.
An evaluation of benthic macroinvertebrate biomass methodology   总被引:2,自引:0,他引:2  
This study shows that biological assessments of water quality status using biomass estimates of wet, dry, and ash-free dry weights and counts of individual organisms from a small, headwater stream in southwestern Ohio provide essentially similar results concerning the impact of a sewage treatment plant discharge. Of the indices of biotic status for the stream segment employed for data evaluation; Diversity Index (D), Community Diversity Index (d), Trophic Condition Index (TCI), and Empirical Biotic Index (EBI), the latter two provided evaluations most consistent with benchmark water chemistry and physics information concerning the trophic status of the stream. In addition, the percent composition of macro-invertebrate taxa by pollutional category; clean water, facultative, and pollution tolerant, as ascribed using TCI and EBI ranges for individual taxa collected in combination of Ekman grab, rock-filled basket sampler and drift net samples, proves adequate for interpretation of biotic status.  相似文献   

4.
Tobacco plants (Nicotiana tabacum L. cv. Bel-W3) were exposed to ambient air for 25 weeks during the 1987 growing season next to an air pollution monitoring station in Brera (Milan, Italy). The research objective was to study the influence of selected environmental parameters on leaf damage in this plant, which is widely used as an ozone indicator. A multiple linear correlation model was estimated between leaf damage and available meteorological and air pollution data. Leaf injury was positively correlated with ozone integrated exposure and temperature, but negatively with vapour pressure deficit. A linear correlation model was used to estimate ozone integrated exposure from the leaf injury indexWork carried out as part of the research programme: ENEL's contribution to the knowledge of important environmental issues, research line: Effects of atmospheric pollution on the land.  相似文献   

5.
The Canadian forest environment is characterized by high spatial and temporal variability, especially in the west. Our forests vary according to climate, landform, and surficial geology, and according to the type, intensity, extent of, and the time since the last disturbance. Most Canadian forests have had a history of repeated acute, episodic disturbance from fire, insects, wind, diseases and/or logging, with a frequency of disturbance varying from a few decades to many centuries. These sources of variability have resulted in a complex and continually changing mosaic of forest conditions and stages of successional development.Monitoring the quality of this dynamic forested landscape mosaic is extremely difficult, and in most cases the concept of a relatively simple index of forest ecosystem quality or condition (i.e. an ecological indicator) is probably inappropriate. Such ecological indicators are better suited for monitoring chronic anthropogenically induced disturbances that are continuous in their effect (e.g. acid rain, heavy metal pollution, air pollution, and the greenhouse effect) in ecosystems that, in the absence of such chronic disturbance, exhibit very slow directional change (e.g. lakes, higher order streams and rivers). Monitoring the effects of a chronic anthropogenic disturbance to forest ecosystems to determine if it is resulting in a sustained, directional alteration of environmental quality will require a definition of the expected pattern of episodic disturbance and recovery therefrom (i.e. patterns of secondary succession in the absence of the chronic disturbance). Only when we have such a temporal fingerprint of forest ecosystem condition for normal patterns of disturbance and recovery can we determine if the ecosystem condition is being degraded by chronic human-induced alteration of the environment. Thus, degradation is assessed in terms of deviations from the expected temporal pattern of conditions rather than in terms of an instantaneous assessment of any particular condition. The concept of ecological rotation (the time for a given ecosystem to recover from a given disturbance back to some defined successional condition) is useful in the definition of these temporal fingerprints. This requires information on the intensity of disturbance, the frequency of disturbance, and the rate of successional recovery. Only when all three of these are known or estimated can statements be made as to whether the ecosystem is in a longterm sustainable condition or not.The somewhat overwhelming complexity of this task has led forest ecologists to use ecosystem-level computer simulation models. Appropriately structured and calibrated models of this type can provide predictions of the overall temporal patterns of ecosystem structure and functions that can be expected to accompany a given frequency and character of episodic disturbance. Such models can also be used to examine the long-term consequences of chronic disturbances such as acid rain and climatic change. Predictive ecosystem-level models should be used in conjunction with some method of stratifying the inherent spatial biophysical variability of the forest environment, such as the biogeoclimatic classification system of British Columbia.  相似文献   

6.
The adsorption and desorption of three volatile organic compounds (1,2- dichloroethane, 1,1,2- trichloroethane and 1,1,2,2-tetrachloroethane) from a previously uncontaminated clayey soil sample from a Superfund site in North Baton Rouge,Louisiana was studied. In the linear range of the adsorption isotherm, the partition constants were not affected by the presence of the co-solutes. The adsorption isotherms over a wide concentration range on the soil followed the nonlinearFreundlich isotherm. The desorption of the compounds showedsignificant hysteresis at all concentrations studied. Approximately 20 to 70% of the adsorbed mass of organic compounds resisted the desorption even after five months ofsuccessive desorption steps. The desorption of four compounds(1,2-dichloroethane, 1,1,2-trichloroethane, 1,4-dichlorobenzeneand hexachlorobutadiene) from a contaminated soil sample fromthe same site was also studied. The aqueous concentration declined as the successive desorption steps progressed. For hexachlorobutediene the desorption can be visualized as occurring in two stages. The first stage involved a loosely bound or reversible fraction and the second stage involveda tightly bound or resistant fraction.  相似文献   

7.
Assessing the major atmospheric issues – acidic deposition, climatechange, ozone depletion, smog, hazardous airpollutants and suspended particulate matter – together rather than individually provides many advantages. But to be successful, this integration requires a common method for relating theseissues to one another. This is a scientific question.In order to successfully resolve the atmospheric issues (a policy question) requires communication of the relevant science to non-scientists in plain language. Non-scientists need to be part of the development of the structure of the communications vehicle. The objective for multi-issueassessment, and thus for the development of an index to trackthe state of the environment in an integrated way, is of courserelated to the desire to achieve environmentally sustainable development.Sustainability can be represented by a 3-legged stool and is an aptsymbol of the struggle of Canadians to balance their ecological,economic and social needs. Although the environment is the basisof all life, humankind has created society and has defined how thatsociety will function (the economy). The three legs of the stool(ecosystem, economy, society) represent the three parts of thesustainability balance. The seat of the stool represents thegovernance process and the three legs are deeply embedded in thisgovernance process because it is the governance which ensures thestability of the system over time. The challenge then is to measure the stability of the stool in a waywhich all can understand. This measure of sustainability must respondto individual and collective actions which improve or degrade the environment. This paper presents such a framework for a sustainability index andoutlines the next steps that need to be taken.The framework starts from the premise that ecosystem, economy andsociety are equal parts of sustainability. Ecosystem indices arerepresentative measures of the state of the environment while economicindices are representative measures of the state of the economy. Socialindices in some way have to measure the state of society. The trick,for a successful sustainability index, will be to ensure that the importantaspects of the ecosystem, the economy and society, are included. The overall index must berelatively stable but must be responsive to changes.  相似文献   

8.
We present a planning framework that structures thelarge amount of interrelated information involved indeveloping regional monitoring programs. By regionalwe mean programs that recognize the importance ofprocesses that occur on larger geographic scales andthat cut across more than one ecosystem component. Theframework helps visualize functional relationshipsamong qualitative ingredients such as public concernsand more concrete details such as individual dataelements. It portrays the flow of information amongthe components of a regional program and ties eachaspect of the program to management decision-makingneeds. This makes it easier, during the planningprocess, to ensure that monitoring will actuallyproduce useful information. Further, the frameworksnovel, graphically oriented, and readily accessibleformat makes key information equally available to thewide range of participants (regulators, scientists,managers, public) whose input and support arenecessary for program success.  相似文献   

9.
The simultaneous behaviour of seven ecological indices(Hurlberts, Margalefs, Menhinicks, Shannons,species number, Jaccards and saprobic index) wasstudied based on phytoplankton data close to the shoreon the East coast of Sweden during the summer 1998.The sampling stations had a similar eutrophicationlevel and were located in bays. Standard phytoplanktondatabases were used in calculating the indices, whichwere later compared using cluster analysis.Hurlberts, Margalefs, Menhinicks, Shannons andspecies number indices, as measure of communitydiversity, produced similar trends which oftendiffered from those based on Jaccards index ofsimilarity. However, the simultaneous use of theseindices was found meaningful as a possible part of themonitoring close to the shore. The application of asaprobic index lead to erroneous conclusions in thestudied case.  相似文献   

10.
This report presents the results of an ozone monitoring experience performed with tobacco indicator plants (Nicotiana tabacum L. cv. Bel-W3). These bioindicators were exposed to ambient air in 23 sites in Northern Italy from 27 April 1987 to 21 October 1987. Typical ozone-induced leaf necrosis was observed in every site. The percentage increase in injured leaf area was estimated weekly and a Leaf Injury Index (LII) was calculated. The weekly series of LIIs were statistically inspected for spatial and temporal relationships. Sample correlation coefficients were statistically significant for almost every possible pair of sites. The time series properties of ten series of LIIs with no missing data were analyzed using Box-Jenkins models. An autoregressive first order model, or AR(1), was selected to remove the autocorrelation from these series. Linear correlation coefficients between prewhitened (i.e. from which autocorrelation had been removed) pairs of LII series were statistically significant. Hence synchronous variations in leaf necrosis could only be related to the regional diffusion of tropospheric ozone.Work carried out as part of the research programme: ENEL's contribution to the knowledge of important environmental issues, Research line; Effects of atmospheric pollution on the land.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号