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41.
On experimental setup in bioelectromagnetics 总被引:1,自引:1,他引:0
Bioeffects created by electromagnetic field (EMF) are the subject of intensive studies. This paper critically considers estimations
of exposure to EMF in bioelectromagnetic experiments. Results of calculations presented herein show the significant role of
the presence of conducting bodies (the exposure system) near an object under test on EMF energy absorption as well as mutual
interactions between simultaneously exposed objects. Our aims herein are twofold: firstly to find a way to refer measurement
results to free-space conditions in order to enable comparison of results obtained in different laboratories, and secondly
to show that EMF energy absorption in any exposed object is different and that this difference is a function of the size of
the exposure system, the number of exposed objects, and the particular properties (i.e., the electromagnetic structure) of
the objects. In the authors’ opinion the existence of interactions caused by the presence of the exposure system and other
exposed objects is a reason why remarkable differences are observed between experiments performed even under supposedly identical
conditions. The presented considerations and conclusion suggest wider participation of physicists and engineers in bioelectromagnetic
experiments in order to ensure the correctness of metrological aspects of these experiments. 相似文献
42.
Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach 总被引:1,自引:0,他引:1
The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result
in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research,
an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing
with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers
primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth
of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater
has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation
Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological
characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban
growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further,
remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization
and its impact on groundwater system. 相似文献
43.
Martin Christian Heinz Mathias ngel Lorenz M. 《Journal of environmental management》2009,90(11):3498-3511
With the intention of bridging the ‘digital divide’ many programmes have been launched to provide computers for educational institutions, ranging from refurbishing second hand computers to delivering low cost new computers. The fast and economical provision of large quantities of equipment is one of the many challenges faced by such programmes. If an increase is to be achieved in the sustainability of computer supplies for schools, not only must equipment be provided, but also suitable training and maintenance delivered. Furthermore, appropriate recycling has to be ensured, so that end-of-life equipment can be dealt with properly. This study has evaluated the suitability of three computer supply scenarios to schools in Colombia: (i) ‘Colombian refurbishment’, -refurbishment of computers donated in Colombia, (ii) ‘Overseas refurbishment’, -import of computers which were donated and refurbished abroad, and (iii) ‘XO Laptop’, -purchase of low cost computers manufactured in Korea. The methods applied were: Material Flow Assessment, -to assess the quantities-, Life Cycle Assessment, -to assess the environmental impacts, and the application of the Multiple Attribute Utility Theory, -to analyse, evaluate and compare different scenarios. The most sustainable solution proved to be the local refurbishment of second hand computers of Colombian origin to an appropriate technical standard. The environmental impacts of such practices need to be evaluated carefully, as second hand appliances have to be maintained, require spare parts and sometimes use more energy than newer equipment. Providing schools with second hand computers from overseas and through programmes such as ‘One Laptop Per Child’ has the disadvantage that the potential for social improvements – such as creation of jobs and local industry involvement – is very low. 相似文献
44.
Biofiltration of waste gases is cost-effective and environment-friendly compared to the conventional techniques for treating large flow rates of gas streams with low concentrations of pollutants. Pulp and paper industry off-gases usually contain reduced sulfur compounds, such as hydrogen sulfide and a wide range of volatile organic compounds (VOCs), e.g., methanol. It is desirable to eliminate both of these groups of compounds. Since the co-treatment of inorganic sulfur compounds and VOCs in biotrickling filters is a relatively unexplored area, the simultaneous biotreatment of H2S and methanol as the model VOC was investigated. The results showed that, after adaptation, the elimination capacity of methanol could reach around 236 g m(-3) h(-1) with the simultaneous complete removal (100%) of 12 ppm H2S when the empty bed residence time is 24 s. The pH of the system was around 2. Methanol removal was hardly affected by the presence of hydrogen sulfide, despite the low pH. Conversely, the presence of the VOC in the waste gas reduced the efficiency of H2S biodegradation. The maximal methanol removal decreased somewhat when increasing the gas flow rate. This is the first report on the degradation of methanol at such low pH in a biotrickling filter and on the co-treatment of H2S and VOCs under such conditions. 相似文献
45.
Schröder P Scheer CE Diekmann F Stampfl A 《Environmental science and pollution research international》2007,14(2):114-122
Background, Aim and Scope
Numerous herbicides and xenobiotic organic pollutants are detoxified in plants to glutathione conjugates. Following this enzyme
catalyzed reaction, xenobiotic GS-conjugates are thought to be compartmentalized in the vacuole of plant cells. In the present
study, evidence is presented for long range transport of these conjugates in plants, rather than storage in the vacuole. To
our knowledge this is the first report about the unidirectional long range transport of xenobiotic conjugates in plants and
the exudation of a glutathione conjugate from the root tips. This could mean that plants possess an excretion system for unwanted
compounds which give them similar advantages as animals.
Materials and Methods:
Barley plants (Hordeum vulgare L. cv. Cherie) were grown in Petri dishes soaked with tap water in the greenhouse.
- Fluorescence Microscopy. Monobromo- and Monochlorobimane, two model xenobiotics that are conjugated rapidly in plant cells
with glutathione, hereby forming fluorescent metabolites, were used as markers for our experiments. Their transport in the
root could be followed sensitively with very good temporal and spatial resolution. Roots of barley seedlings were cut under
water and the end at which xenobiotics were applied was fixed in an aperture with a thin latex foil and transferred into a
drop of water on a cover slide. The cover slide was fixed in a measuring chamber on the stage of an inverse fluorescence microscope
(Zeiss Axiovert 100).
- Spectrometric enzyme assay. Glutathione S-transferase (GST) activity was determined in the protein extracts following established
methods. Aliquots of the enzyme extract were incubated with 1-chloro-2,4-dinitrobenzene (CDNB), or monochlorobimane. Controls
lacking enzyme or GSH were measured.
- Pitman chamber experiments. Ten days old barley plants or detached roots were inserted into special incubation chambers, either
complete with tips or decapitated, as well as 10 days old barley plants without root tips. Compartment A was filled with a
transport medium and GSH conjugate or L-cysteine conjugate. Compartments B and C contained sugar free media. Samples were
taken from the root tip containing compartment C and the amount of conjugate transported was determined spectro-photometrically.
Results:
The transport in roots is unidirectional towards the root tips and leads to exsudation of the conjugates at rates between
20 and 200 nmol min-1. The microscopic studies have been complemented by transport studies in small root chambers and spectroscopic
quantification of dinitrobenzene-conjugates. The latter experiments confirm the microscopic studies. Furthermore it was shown
that glutathione conjugates are transported at higher rates than cysteine conjugates, despite of their higher molecular weights.
This observation points to the existence of glutathione specific carriers and a specific role of glutathione in the root.
Discussion:
It can be assumed that long distance transport of glutathione conjugates within the plant proceeds like GSH or amino acid
transport in both, phloem and xylem. The high velocity of this translocation of the GS-X is indicative of an active transport.
For free glutathione, a rapid transport-system is essential because an accumulation of GSH in the root tip inhibits further
uptake of sulfur. Taking into account that all described MRP transporters and also the GSH plasmalemma ATPases have side activities
for glutathione derivatives and conjugates, co-transport of these xenobiotic metabolites seems credible.
- On the other hand, when GS-B was applied to the root tips from the outside, no significant uptake was observed. Thus it can
be concluded that only those conjugates can be transported in the xylem which are formed inside the root apex. Having left
the root once, there seems to be no return into the root vessels, probably because of a lack of inward directed transporters.
Conclusions:
Plants seem to possess the capability to store glutathione conjugates in the vacuole, but under certain conditions, these
metabolites might also undergo long range transport, predominantly into the plant root. The transport seems dependent on specific
carriers and is unidirectional, this means that xenobiotic conjugates from the rhizosphere are not taken up again. The exudation
of xenobiotic metabolites offers an opportunity to avoid the accumulation of such compounds in the plant.
Recommendations and Perspectives:
The role of glutathione and glutathione related metabolites in the rhizosphere has not been studied in any detail, and only
scattered data are available on interactions between the plant root and rhizosphere bacteria that encounter such conjugates.
The final fate of these compounds in the root zone has also not been addressed so far. It will be interesting to study effects
of the exuded metabolites on the biology of rhizosphere bacteria and fungi. 相似文献
46.
Aishah S. A. K. Sharifah Hanafiah Zainal Abidin Mohamad R. Sulaiman Kheng H. Khoo Hairi Ali 《Journal of Material Cycles and Waste Management》2008,10(2):116-123
Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems
of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely
affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one
possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration
of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal
solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment
may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate
the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW
collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and
chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in
the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable
for treating MSW. 相似文献
47.
48.
Reiner Schroll Sabine Grundmann Ulrike Dörfler Bernhard Ruth Jean Charles Munch 《Water, Air, & Soil Pollution: Focus》2008,8(2):209-216
Several lysimeter scenarios and approaches exist to study the fate of agro-chemicals or contaminants from deposition in soil
columns. In many systems just transport and leaching of the parent compound is followed, in some systems the leaching and
transport of the metabolites is investigated as well. In more sophisticated lysimeter systems the volatilization and also
the mineralization of the applied chemicals can be additionally monitored. Depending on the lysimeter system used and on the
fact whether the applied chemicals are 14C-labeled or not, different results and various interpretations of the results might be achieved. Different lysimeter systems
are described in this paper and a real dataset of a specific lysimeter experiment was transferred and evaluated in a virtual
approach in the different lysimeter systems in order to show the advantages and disadvantages of the various systems. 相似文献
49.
Bauer RD Maloszewski P Zhang Y Meckenstock RU Griebler C 《Journal of contaminant hydrology》2008,96(1-4):150-168
Various abiotic and biotic processes such as sorption, dilution, and degradation are known to affect the fate of organic contaminants, such as petroleum hydrocarbons in saturated porous media. Reactive transport modeling of such plumes indicates that the biodegradation of organic pollutants is, in many cases, controlled by mixing and therefore occurs locally at the plume's fringes, where electron donors and electron-acceptors mix. Herein, we aim to test whether this hypothesis can be verified by experimental results obtained from aerobic and anaerobic degradation experiments in two-dimensional sediment microcosms. Toluene was selected as a model compound for oxidizable contaminants. The two-dimensional microcosm was filled with quartz sand and operated under controlled flow conditions simulating a contaminant plume in otherwise uncontaminated groundwater. Aerobic degradation of toluene by Pseudomonas putida mt-2 reduced a continuous 8.7 mg L(-1) toluene concentration by 35% over a transport distance of 78 cm in 15.5 h. In comparison, under similar conditions Aromatoleum aromaticum strain EbN1 degraded 98% of the toluene infiltrated using nitrate (68.5+/-6.2 mg L(-1)) as electron acceptor. A major part of the biodegradation activity was located at the plume fringes and the slope of the electron-acceptor gradient was steeper during periods of active biodegradation. The distribution of toluene and the significant overlap of nitrate at the plume's fringe indicate that biokinetic and/or microscale transport processes may constitute additional limiting factors. Experimental data is corroborated with results from a reactive transport model using double Monod kinetics. The outcome of the study shows that in order to simulate degradation in contaminant plumes, detailed data sets are required to test the applicability of models. These will have to deal with the incorporation of existing parameters coding for substrate conversion kinetics and microbial growth. 相似文献
50.
A choice experiment is used to estimate how Vietnamese households value a flood risk reduction. The empirical analysis is conducted on a sample of households located in the Nghe An Province, one of the provinces which is the most affected by floods in Vietnam. The results reveal that there is a high level of heterogeneity in preferences across households. We compute the willingness to pay (WTP) for a flood risk reduction, and we identify how it relates to different attributes of flood management policies (reduction of economic losses, reduction of human losses, political level in charge of implementing the flood management policy). In particular, the marginal WTP for reducing the flood fatality rate, which can be interpreted as the value of statistical life (VSL), varies from 2 517 million VND (approximately 120,818 USD) to 3 590 million VND (approximately 172,323 USD) depending on the model considered. The VSL represents between 77 and 111 times the annual household average income in our sample, a result in line with previous estimates in similar countries. 相似文献