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排序方式: 共有6520条查询结果,搜索用时 750 毫秒
741.
本文提出一种利用静电场的印染废水处理方法,印染废水中的污染颗粒在电场的作用下,朝一定的方向迁移,从而发生“强制电中和”作用,这种电中和作用的场能消耗极小,而被中和的污染物颗粒由于凝聚作用,则会不断长大而易于通令过滤去除,这一处理工艺在经“自数”预处理之后,可继续使COD和色度的去除百分数分别达60%和63%以上。 相似文献
742.
William P. Carey 《Journal of the American Water Resources Association》1984,20(2):261-265
ABSTRACT: A technique for weighing bedload samples that was developed for laboratory use has been modified for field application. The technique involves determining the submerged weight of bedload samples as they are collected. The submerged weights are converted to dry weights from a knowledge of the specific gravity of the bedload material. The technique makes bedload transport data available immediately and eliminates costly and time-consuming steps involved with saving samples for laboratory analysis. Only samples designated for particle-size or other lab analyses need to be saved. 相似文献
743.
744.
本文介绍了遥感技术在滑坡的现状调查和防治中的应用.提出了航天、航空遥感图像上滑坡现状、规模、易滑地点、稳定性评价等的直接和间接判读标志;并展望了遥感技术在滑坡动态监测中的应用前景. 相似文献
745.
Vernal pools are vulnerable to loss through development and agricultural and forestry practices owing to their isolation from open water bodies and their small size. Some vernal pool-dependent species are already listed in New England as Endangered, Threatened, or Species of Special Concern. Vernal pool creation is becoming more common in compensatory mitigation as open water ponds, in general, may be easier to create than wooded wetlands. However, research on vernal pool creation is limited. A recent National Research Council study (2001) cites vernal pools as challenging to recreate. We reviewed documentation on 15 vernal pool creation projects in New England that were required by federal regulatory action. Our purpose was to determine whether vernal pool creation for compensatory mitigation in New England replaced key vernal pool functions by assessing project goals and documentation (including mitigation plans, pool design criteria, monitoring protocols, and performance standards). Our results indicate that creation attempts often fail to replicate lost pool functions. Pool design specifications are often based on conjecture rather than on reference wetlands or created pools that function successfully. Project monitoring lacks consistency and reliability, and record keeping by regulatory agencies is inadequate. Strengthening of protection of isolated wetlands in general, and standardization across all aspects of vernal pool creation, is needed to ensure success and to promote conservation of the long-term landscape functions of vernal pools. 相似文献
746.
Clow David W. Striegl Robert G. Nanus Leora Mast M. Alisa Campbell Donald H. Krabbenhoft David P. 《Water, Air, & Soil Pollution: Focus》2002,2(2):139-164
A chemical survey of 69 high-altitude lakes in seven national parks in the western United States was conducted during the fallof 1999; the lakes were previously sampled during the fall of 1985, as part of the Western Lake Survey. Lakes in parks in the Sierra/southern Cascades (Lassen Volcanic, Yosemite, Sequoia/Kings Canyon National Parks) and in the southern RockyMountains (Rocky Mountain National Park) were very dilute; medianspecific conductance ranged from 4.4 to 12.2 S cm-1 andmedian alkalinity concentrations ranged from 32.2 to 72.9 eqL-1. Specific conductances and alkalinity concentrations were substantially higher in lakes in the central and northernRocky Mountains parks (Grand Teton, Yellowstone, and GlacierNational Parks), probably due to the prevalence of more reactivebedrock types. Regional patterns in lake concentrations of NO3 and SO4 were similar to regional patterns in NO3 and SO4 concentrations in precipitation, suggestingthat the lakes are showing a response to atmospheric deposition.Concentrations of NO3 were particularly high in Rocky Mountain National Park, where some ecosystems appear to be undergoing nitrogen saturation. 相似文献
747.
The Information Cycle as a Framework for Defining Information Goals for Water-Quality Monitoring 总被引:2,自引:0,他引:2
/ The necessity to tailor information becomes increasingly urgent as the information revolution continues to generate ever-increasing flows of data and so-called information. From European experiences, a new approach for monitoring system design is suggested in this paper. In this approach, careful and detailed specification of information needs is a major contributing factor to the effectiveness of information products. To develop better specifications for information products, the process of collecting and transforming data into useful information requires careful thought and guidance. A dialogue between information users on one hand and information producers on the other is essential. This dialogue can be based on the information cycle, describing the continuous process from specifying information needs for water management and a strategy to collect information through data collection and data analysis up to utilization of information by water management. By following the respective steps in the information cycle, the process of information gathering can be completed. The cyclic character provides a quantitative means of connecting monitoring system design and operations with the information expectations and/or products required by management. 相似文献
748.
J. L. Bardasano J. Álvarez-Ude I. Gutiérrez M. Raposo R. Goya 《The Environmentalist》2007,27(4):519-523
Objectives This paper aims to provide evidence of an inductive electromagnetic bioeffect on the human brain, which is independent from
sound waves and produced by mobile phones, in proximal field, through correlating the EEG data obtained from electrodes placed
on both normal and cochlear deaf individuals.
Methods Two groups of subjects are placed under controlled electromagnetic conditions inside a Faraday chamber, 12 healthy and another
12 suffering from cochlear deafness). Each is sitting on a chair, fitted with additional support, and holding a cellular phone
2 cm away form the right auricular, in order to avoid a thermal effect as much as possible. All of them, relaxed and with
their eyes closed, are EEG recorded in a basal state with their mobile phones off. Then, each of them is again recorded under
the same conditions but with the mobile on and listening to the same conversation. In order to assess the observed EEG changes,
a statistical analysis by means of the FFT (Fast Fourier Transform) was carried out.
Results For both, healthy and cochlear deaf, assimilation or integration of the mobile phone signal by some electrodes is to be found.
This is due to the increase of amplitudes for alpha and theta waves, whereas the signal is not integrated in other electrodes.
By correlating the spectra of frequencies of corresponding EEG records for the same brain areas, we have not observed significative
differences for both groups.
Conclusions A possible electromagnetic direct inductive, non-thermal, bioeffect on the human brain is observed. This effect is produced
by the use of mobile phones and it bears no relation to the sound waves. 相似文献
749.
Illinois has been operating an ambient water quality network of almost 600 stations for several years. In 1977 changes in program emphasis toward intensive monitoring, the need for improved procedures and quality control in monitoring operations, and the desire to create a single data base of all Illinois State monitoring data, resulted in a redesign of the ambient monitoring program.A unique cooperative program between the Illinois Environmental Protection Agency and the US Geological Survey provides for their monitoring a portion of the network. The Survey provides flow data at most network stations as well as extensive manpower training, equipment, data processing, and program quality control. Informal agreements with other agencies have permitted a great reduction in the monitoring effort required by the Illinois Environmental Protection Agency. 相似文献
750.