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671.
Subbiah Seenivasan NarayananNair Muraleedharan 《Environmental monitoring and assessment》2011,176(1-4):365-371
Tea is considered as a ‘health beverage’ due its antioxidant properties and resultant beneficial effects on human health. Such a beverage should be free from toxic elements such as pesticide residues and heavy metals. A large scale survey of teas produced in the tea factories of south India had been carried out for a period of three years from 2006 to 2008 and 912 tea samples were analysed for the residues of certain pesticides such as dicofol, ethion, quinalphos, hexaconazole, fenpropathrin, fenvalerate and propargite which are used for pest and disease control in tea in this part of the country. The analytical data proved that only less than 0.5 percentage of tea samples had residues of these pesticides. However, residues of pesticides were below their maximum limits in tea, stipulated by the European Union, Codex Alimentarius Commission of FAO/WHO and Prevention of Food Adulteration Act of Govt. of India. 相似文献
672.
A Method for Ensemble Wildland Fire Simulation 总被引:1,自引:0,他引:1
Mark A. Finney Isaac C. Grenfell Charles W. McHugh Robert C. Seli Diane Trethewey Richard D. Stratton Stuart Brittain 《Environmental Modeling and Assessment》2011,16(2):153-167
An ensemble simulation system that accounts for uncertainty in long-range weather conditions and two-dimensional wildland
fire spread is described. Fuel moisture is expressed based on the energy release component, a US fire danger rating index,
and its variation throughout the fire season is modeled using time series analysis of historical weather data. This analysis
is used to characterize the seasonal trend in ERC, autocorrelation of residuals, and daily standard deviation and stochastically
generate artificial time series of afternoon fuel moisture. Daily wind speed and direction are sampled stochastically from
joint probabilities of historical wind speed and direction for the date range of the fire simulation period. Hundreds or thousands
of fire growth simulations are then performed using the synthetic fire weather sequences. The performance of these methods
is evaluated in terms of the number of ensemble member simulations, one- versus two-dimensional fire spread simulations, and
comparison with results from 91 fires occurring from 2007 to 2009. Simulations were found to be in consistent agreement with
observations, but trends indicate that the ensemble average of simulated fire sizes were consistently larger than actual fires
whereas the farthest extent burned by fires was underestimated. 相似文献
673.
Armando A. Rodriguez Oguzhan Cifdaloz John Martin Anderies Marco A. Janssen Jeffrey Dickeson 《Environmental Modeling and Assessment》2011,16(1):15-36
This paper presents a framework for the study of policy implementation in highly uncertain natural resource systems in which
uncertainty cannot be characterized by probability distributions. We apply the framework to parametric uncertainty in the
traditional Gordon–Schaefer model of a fishery to illustrate how performance can be sacrificed (traded-off) for reduced sensitivity
and hence increased robustness, with respect to model parameter uncertainty. With sufficient data, our robustness–vulnerability
analysis provides tools to discuss policy options. When less data are available, it can be used to inform the early stages
of a learning process. Several key insights emerge from this analysis: (1) the classic optimal control policy can be very
sensitive to parametric uncertainty, (2) even mild robustness properties are difficult to achieve for the simple Gordon–Schaefer
model, and (3) achieving increased robustness with respect to some parameters (e.g., biological parameters) necessarily results
in increased sensitivity (decreased robustness) with respect to other parameters (e.g., economic parameters). We thus illustrate
fundamental robustness–vulnerability trade-offs and the limits to robust natural resource management. Finally, we use the
framework to explore the effects of infrequent sampling and delays on policy performance. 相似文献
674.
In several branches of science and technology a gaseous phase is dispersed into a liquid in the form of bubbles, a gaseous
component then dissolves into the liquid and subsequently undergoes chemical reaction. The overall process performance can
be improved substantially when the area of gas–liquid contact is increased. By subjecting the liquid phase to low frequency
vibrations, the bubbles are shown to suffer significant breakage, induced by resonance. When the vibration is properly tuned,
the interfacial area is found to increase by a factor of 1.8–2.4, depending on the properties of the liquid. Resonance-induced
bubble breakage phenomena have a great potential for improving the rates of chemical processes involving fast reactions, with
minimal energy input.
Received: 7 July 2000 / Accepted in revised form: 28 August 2000 相似文献
675.
Laperdina T. G. Melnikova M. V. Koval A. T. Sidorov Y. F. Nagorny V. A. Ostapchuk V. I. 《环境科学学报(英文版)》2000,(Z1)
IntroductionSiberiaandtheFarEastaretheoldestandtherichestgold miningareasofRussia .Intensivegold miningherestartedinthebeginningofthe 19thcentury(Vyazelshchikov ,1963) .Forthemostpartgold bearingoresandsandswereprocessedwiththeuseofamalgamationmethodforgolde… 相似文献
676.
Jeffrey I. Zink 《Die Naturwissenschaften》1981,68(10):507-512
Triboluminescence is the light emitted when mechanical energy is applied to a crystal. Many common substances such as sugar and copper sulfate are triboluminescent. The origin of the light and the mechanical, chemical, and crystallographic requirements of the phenomenon are described in this paper. 相似文献
677.
678.
Recent drinking water regulations have lowered the disinfection by-product standards as well as added new disinfection by-products for regulation. Natural organic matter (NOM) plays a major role in the formation of undesirable organic by-products following disinfection/oxidation of drinking water. It is suspected that most precursors to disinfection by-products are humic, although nonhumic substances are also suspected of contributing to these by-products. Many of the disinfection by-products have adverse health effects in humans (i.e., carcinogenic or mutagenic effects). The primary chlorinated disinfection by-products of concern include trihalomethanes, haloacetic acids, and haloacetonitrile. Fluorescence spectroscopy was used to study humic and fulvic acids. The two fractions of humic substances, humic and fulvic acids, were characterized by a double-peak phenomena in an overlapping fluorescing region. Disinfection by-product formation potentials of humic and fulvic acids have been correlated with total organic carbon, UV absorbance at 254 nm, specific absorbance and fluorescence. River humic and fulvic acid was found to have the highest reactivity to disinfection by-product formation as compared to soil and peat humic and fulvic acid. Fluorescence spectroscopy has shown to be a rapid and predictive tool for disinfection by-products formation potential of humic and fulvic acids. 相似文献
679.
Aarif H. El-Mubarak Ahmed I. Rushdi Khalid F. Al-Mutlaq Abdulqader Y. Bazeyad Staci L. M. Simonich Bernd R. T. Simoneit 《Environmental science and pollution research international》2014,21(1):558-567
In an effort to assess the occurrence and sources of polycyclic aromatic hydrocarbons (PAHs) in the ambient air of Riyadh, Saudi Arabia, PM10 samples were collected during December 2010. Diagnostic PAH concentration ratios were used as a tool to identify and characterize the PAH sources. The results reflect high PM10 and PAH concentrations (particulate matter (PM)?=?270–1,270 μg/m3). The corresponding average PAH concentrations were in the range of 18?±?8 to 1,003?±?597 ng/m3 and the total concentrations (total PAHs (TPAHs) of 17 compounds) varied from 1,383 to 13,470 ng/m3 with an average of 5,871?±?2,830 ng/m3. The detection and quantification limits were 1–3 and 1–10 ng/ml, respectively, with a recovery range of 42–80 %. The ratio of the sum of the concentrations of the nine major non-alkylated compounds to the total (CPAHs/TPAHs) was 0.87?±?0.10, and other ratios were determined to apportion the PM sources. The PAHs found are characteristic for emissions from traffic with diesel being a predominant source. 相似文献
680.