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471.
Yongnian Ni Lin Wang Serge Kokot 《Journal of environmental science and health. Part. B》2013,48(4):328-335
A novel differential pulse voltammetry method (DPV) was researched and developed for the simultaneous determination of Pendimethalin, Dinoseb and sodium 5-nitroguaiacolate (5NG) with the aid of chemometrics. The voltammograms of these three compounds overlapped significantly, and to facilitate the simultaneous determination of the three analytes, chemometrics methods were applied. These included classical least squares (CLS), principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural networks (RBF-ANN). A separately prepared verification data set was used to confirm the calibrations, which were built from the original and first derivative data matrices of the voltammograms. On the basis relative prediction errors and recoveries of the analytes, the RBF-ANN and the DPLS (D – first derivative spectra) models performed best and are particularly recommended for application. The DPLS calibration model was applied satisfactorily for the prediction of the three analytes from market vegetables and lake water samples. 相似文献
472.
环境监测工作是环境保护工作的基础工作,在新的形势下,如何做好环境监测工作,是环保工作必须面对的一个重要课题。本文通过总结研究淮北市在环境监测工作中一些富有创造性的做法和所取得的成效,经验,提出了一些有独立见解的工作思路和建议,对广大环保工作者特别是环境监测工作者,有一定的借鉴意义。 相似文献
473.
474.
Numerical site-specific chemical and biological criteria were established to assess the impact of a pilot dredging project
on water quality at the New Bedford Harbor, Massachusetts, USA, Superfund site. Because most existing chemical concentrations
in the water column and indigenous biota exceeded federal and state water quality limits, the derivation of site-specific
criteria was required. Prior to any operational phases of the project (i.e., dike construction, dredging), criteria values
were developed from background concentrations of PCBs and metals in water and biota, as well as for the toxic effects of water
quality on the biota. During each operational phase of the project, water samples were collected, analyzed within 16 h, and
the data supplied to a management committee in order to assess the environmental impact of the previous days' operation. The
ambient unfiltered water concentration of PCBs and metals were the only chemical or biological criteria exceeded. Modification
of the next days' operations resulted in a return of these concentrations to background levels. The combined use of site-specific
criteria and a real-time decision making management process allowed for successful completion of this project with a minimal
effect on water quality. 相似文献
475.
Thomas A. Fontaine 《Journal of the American Water Resources Association》1991,27(3):509-520
ABSTRACT: The areal mean precipitation (AMP) over a catchment is normally calculated using point measurements at rainfall gages. Error in AMP estimates occurs when an insufficient number of gages are used to sample precipitation which is highly variable in space. AMP error is investigated using historic, severe rainfalls with a set of hypothetical catchments and raingage networks. The potential magnitude of error is estimated for typical gage network densities and arrangements. Possible sources of error are evaluated, and a method is proposed for predicting the magnitude of error using data that are commonly available for severe, historic rainfall. 相似文献
476.
477.
我国环境问题日趋严重,环境污染和生态破坏已成为社会发展的制约因素。然而,有些企业忽视环境保护工作,取消或合并环境监测站,削弱环境监测力量。针对这种情况,从行业环境监测站的任务、作用和不可取代性方面阐述了强化行业环境监测站建设的必要性。 相似文献
478.
Malcolm J. R. Clark Paul H. Whitfield 《Journal of the American Water Resources Association》1994,30(6):1063-1079
ABSTRACT: Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left-censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left-censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives. 相似文献
479.
Richard A. Herbert Darrell D. Carlson Gregg J. Wiche 《Journal of the American Water Resources Association》1985,21(6):953-965
The crest-stage gage program in Louisiana was evaluated to determine if the data were adequate for use in developing regional flood-frequency equations and to determine if any crest-stage gage stations could be discontinued. An abundance of data at many crest-stage gage stations and a lack of data for urban areas and flat-slope areas indicated a need for a shift in the number, type, and locations of gages. Correlations and comparisons of annual peak discharges and watershed characteristics of 96 existing stations resulted in the elimination of 72 stations and the addition of one new station, reducing the total network to 25 stations that could be used for future flood-frequency analyses. The adequacy of the reduced network for development and verification of regional flood-frequency equations was tested by comparing a set of regional flood-frequency equations developed using data from the full network with a set developed using data from the reduced network. The results indicate that the crest-stage gage network can be reduced to 25 stations and still provide adequate information for future flood-frequency analyses. 相似文献
480.
The present study tested the separate and the interactive pollution effects of cadmium and mercury on the electrophoretically detected allelic isozyme frequencies of the enzyme phosphoglucose isomerase for two species of littoral marine gastropods —Littorina punctata andL. neritoides — and the enzyme amino peptidase forL. neritoides. Our results indicate differential survivorship of allelic isozyme genotypes specific for each type of pollutant and for their interaction, as well as trends common to all pollutants. Theoretically the results reflect the adaptive nature of at least some allozymic genotypes in these marine gastropods and seem inconsistent with the neutral theory of allozyme polymorphisms. Practically, the results reinforce earlier conclusions that changes in the frequency of allelic isozymes may be used as a genetic monitor of pollution. 相似文献