BS 3680-2D-1993 Measurement of liquid flow in open channels - Dilution methods - Methods of measurement using fluorescent tracers《明渠流量测量 第2部分 稀释法 第2D节 荧光示踪测量方法》.pdf

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1、BRITISH STANDARD BS3680-2D: 1993 ISO9555-4: 1992 Measurement of liquid flow in open channels Part 2: Dilution methods Part 2D: Methods of measurement using fluorescent tracers UDC 532.574.8:532.543BS3680-2D:1993 This British Standard, having been prepared under the directionof the Industrial-process

2、 Measurement and Control Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 15 March1993 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference PCL/3 Draft for comment88/32447 DC ISBN 0 580 21655 1 Com

3、mittees responsible for this British Standard The preparation of this British Standard was entrusted by the Industrial-process Measurement and Control Standards Policy Committee (PCL/-) to Technical Committee PCL/3, upon which the following bodies were represented: Clyde River Purification Board Dep

4、artment of the Environment Institute of Measurement and Control Institution of Water and Environmental Management National Rivers Authority Water Services Association of England and Wales Welsh Office The following bodies were also represented in the drafting of the standard, through subcommittees a

5、nd panels: Institute of Hydrology Water Research Centre Amendments issued since publication Amd. No. Date CommentsBS3680-2D:1993 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Normative reference 1 3 Definitions 1 4 Tracers used

6、2 5 Tracer measurement 2 6 Environmental factors affecting tracers 6 7 Techniques for tracer injection 7 8 Sampling techniques 7 9 Analysis and computations 7 10 Special requirements 7 Annex A (normative) General characteristics of commonly used fluorescent tracers 8 Figure 1 Basic structure of most

7、 filter fluorimeters 3 Figure 2 Excitation and emission spectra 4 Figure 3 Temperature correction curves for acid yellow7, rhodamineWT,sulfo, rhodamine B and pyranine 7 List of references Inside back coverBS3680-2D:1993 ii BSI 07-1999 National foreword This Part of BS3680 has been prepared under the

8、 direction of the Industrial-process Measurement and Control Standards Policy Committee. It is identical with ISO9555-4:1992 Measurement of liquid flow in open channels Tracer dilution methods for the measurement of steady flow Part4: Fluorescent tracers, published by the International Organization

9、for Standardization (ISO). This is one of a series of Parts of BS3680 on dilution methods, as follows: Part2A: General 1)2) ; Part2B:1993: Radioactive tracers; Part2C 1) : Chemical tracers; Part2D:1993: Fluorescent tracers. These four Parts of BS3680 supersede BS3680-2A:1964, BS3680-2B:1986, and BS3

10、680-2C:1983 which are withdrawn. Cross-references. The Technical Committee has reviewed the provisions of ISO772:1988 and ISO9555-1 1)2) , to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related British Standard

11、to ISO772:1988 is BS3680-1:1991 Measurement of liquid flow in open channels Part1: Glossary of terms. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standar

12、d does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. T

13、his will be indicated in the amendment table on the inside front cover. 1) In preparation. 2) It is envisaged that, when ISO9555-1 is published, it will be implemented in the UK as BS3680-2A.ISO9555-4:1992(E) BSI 07-1999 1 Introduction The former standard series ISO555 was subdivided into parts on t

14、he basis of the method of field measurement, i.e.constant-rate injection method and integration (sudden injection) method. Since the choice of the type of tracer to be used in a field measurement will often depend on the expertise and the laboratory facilities available, this new series of standards

15、 ISO9555 is divided into pads based on the type of tracer used. This revision has enabled the unnecessary repetition of text of the various parts to be avoided and will, it is hoped, prove to be a more convenient form of presentation for the user. ISO9555 deals with the measurement of steady flow in

16、 open channels by dilution methods using tracers. The methods described may also be applied to the measurement of slowly varying flow, but they may only be used when flow conditions ensure adequate mixing of the injected solution throughout the flow. For the measurement of very large flows, tracer m

17、ethods can be onerous in terms of tracer costs and measurement times. However, the use of tracers often reduces danger to personnel during flood periods. ISO9555-1 presents the general principles of the methods of constant-rate injection and integration (sudden injection). ISO9555-2, ISO9555-3 and I

18、SO9555-4 deal with the specific aspects of the use of radioactive, chemical and fluorescent tracers, respectively, as well as specific analytical procedures. This approach has been adopted for the following reasons: to facilitate subsequent updating, additions or revisions which concern only ISO9555

19、-2, ISO9555-3 or ISO9555-4; to provide a more practical document for the user, who is often obliged to choose the tracer best suited to the available analytical equipment. 1 Scope This part of ISO9555 deals with the use of fluorescent tracers in discharge measurements by the dilution method. Apparat

20、us and methods of general application are set out in ISO9555-1 and are not repeated here, with the exception of those relating specifically to fluorescent tracers. The use of fluorescent tracers is attractive because of the small amounts of tracer needed to make a discharge measurement. Certain fluo

21、rescent tracers can be measured at concentrations of less than14g/l. Fluorescent tracers are easy to handle and their concentrations can be readily determined. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this part o

22、f ISO9555. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO9555 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and

23、 ISO maintain registers of currently valid International Standards. ISO772:1988, Liquid flow measurement in open channels Vocabulary and symbols. 3 Definitions For the purposes of this part of ISO9555, the definitions given in ISO772:1988 and the following definitions apply. 3.1 fluorescence the emi

24、ssion of electromagnetic waves of characteristic energy when atoms or molecules decay from an excited state to a lower energy state. The excitation may be induced by subjecting the substance to radiation of slightly higher energy (shorter wavelength) than that of the characteristic emission, and it

25、ceases as soon as the external source is removed 3.2 fluorimeter; filter fluorimeter instrument equipped with a lamp or other means of exciting fluorescent radiation in a sample, with filters and with a detector to measure relative fluorescent intensities caused by variations in concentration of the

26、 substance under examination. If the wavelengths are determined using a monochromator, the instrument is called a spectrofluorimeter 3.3 fluorescence quenching the reduction of fluorescence intensity, due to an interaction of the dye molecules with other chemicals present in the water. Concentration

27、 quenching is a phenomenon which appears to be similar to fluorescence quenching but is not a true quenching. Instead, it is a reduction in the rate of increase of the flowmeter readout with increasing dye concentration due to the increasing optical density of the dye itself. Concentration quenching

28、 occurs only at very high concentrationsISO9555-4:1992(E) 2 BSI 07-1999 4 Tracers used 4.1 General A number of fluorescent dyes have been used as tracers for measuring open-channel flow. Stream waters generally have lower background fluorescence in the orange than in the green and blue wavelengths.

29、Consequently, the orange wavebands allow for greater sensitivities than do the green and blue wavebands. Six fluorescent dyes are discussed for use in discharge measurements: fluorescein and rhodamine B (see4.2 and4.3) have been used extensively in the past but are no longer recommended for use in m

30、aking discharge measurements. The other four tracers: acid yellow7, sulfo rhodamine B, pyranine and rhodamine WT (see4.4 to4.7) have good properties for making discharge measurements and will be discussed further in this part of ISO9555. Other tracers such as eosine (acid red87) have not yet been wi

31、dely studied but might be used in the future. The general characteristics of commonly used fluorescent tracers are given in Annex A. 4.2 Fluorescein Fluorescein, also known as sodium fluorescein, was one of the earliest dyes used as a tracer in water. However, it is highly susceptible to photochemic

32、al decay and its fluorescence response is subject to changes at pH values less than6,5. Also, many streams exhibit high background fluorescence similar to that of fluorescein. Therefore, this dye is not recommended for the measurement of flow in open channels. 4.3 Rhodamine B Rhodamine B has been ex

33、tensively used as a tracer in water. However, it is readily adsorbed onto sediments, sample bottles and test equipment. Also, it has been shown to be somewhat toxic to aquatic organisms under certain conditions. Generally, however, the high concentrations of dye required to produce toxicity problems

34、 exist only for insignificant periods of time at the point of dye injection in an open channel during the measurement of flow. Rhodamine B is not recommended for discharge measurement, primarily because of its high losses as a result of adsorption. 4.4 Acid yellow7 Acid yellow7 is also known as liss

35、amine FF, lissamine yellow FP, brilliant sulfo flavine FF, and brilliant acid yellow8G. 4.5 Sulfo rhodamine B Sulfo rhodamine B is also known as pontacyl brilliant pink B, lissamine red4B, kiton rhodamine B, acid rhodamine B , kenacid-G, and aminorhodamine-g extra. 4.6 Pyranine Pyranine is also know

36、n as solvent green7. 4.7 Rhodamine WT Rhodamine WT has been widely used as a water tracer while sulfo rhodamine B, acid yellow7 and pyranine have less use as a tracer in water. 5 Tracer measurement 5.1 Principles Fluorimetric analysis, or fluorimetry, is based on the physical phenomenon called fluor

37、escence. Fluorescence is a result of an almost instantaneous sequence of events as follows: a) absorption of energy from an outside source such as the sun or an ultraviolet lamp; b) excitation of some of the electrons of the fluorescent substance, resulting in enlarged electron orbits, called the “e

38、xcited state”; c) emission of energy in the form of photons (light), as the excited electrons return to their normal positions or the “ground state”. The emitted (fluoresced) energy nearly always has longer wavelengths and lower frequencies than the absorbed energy, because some energy is lost in th

39、e process (Stokes law). It is this property of dual spectra, i.e.the different specific combination of excitation and emission spectra for each fluorescent substance, which is utilized in fluorimetry to make it an accurate and sensitive analytical tool. Most substances are at least mildly fluorescen

40、t, and most fluorescence occurs in the200nm to800nm range of wavelengths, i.e.ultraviolet and visible light. Strongly fluorescent substances convert a high percentage of absorbed energy into emitted energy. Fortunately, most strongly fluorescent substances fluoresce in the ultraviolet-to-green part

41、of the spectrum, while fewer substances, including the tracer dyes recommended for use in flow measurements, fluoresce in the yellow-orange band. These dyes are strongly fluorescent in dilute solutions. Fluorescent materials likely to be found in some streams include algae and other naturally occurr

42、ing organics, certain minerals, and man-made pollutants such as paper and textile treated with optical cleaning agents, certain petroleum products and laundry detergent brighteners.ISO9555-4:1992(E) BSI 07-1999 3 Fluorescence intensity is affected in varying degrees by certain physical and chemical

43、factors, such as the type of solvent, the concentration, the temperature, the pH, photochemical decay and fluorescence quenching. The fluorimeter, or filter fluorimeter, is the basic piece of equipment used to measure fluorescence. The fluorimeter is an instrument which gives a relative measure of i

44、ntensity of light emitted by a sample containing a fluorescent substance; the intensity of fluorescent light is proportional to the amount of fluorescent substance present. A fluorimeter consists of six basic components as shown in Figure 1. All commercial fluorimeters have the same basic structure.

45、 Figure 1 Basic structure of most filter fluorimetersISO9555-4:1992(E) 4 BSI 07-1999 Figure 2 Excitation and emission spectraISO9555-4:1992(E) BSI 07-1999 5 The sensitivity of a fluorimeter determines the lower limit of detectability of a dye. For a given fluorimeter and dye, instrument sensitivity

46、and hence dye detectability depend on the characteristics and interrelationships of the optical components of the instrument. Usually, the sensing device in a fluorimeter is fixed, or not easily replaced, but the energy (or light) source and the colour filters can be selected to best match the dye t

47、hat is to be used. It should be noted that when sensitivity of the instrument is increased, undesirable effects, such as background interference, may also be increased. For any contemplated change in optical components to be useful, it must be favourable to dye detectability. The objective in both l

48、amp and colour filter selection is to obtain as much sensitivity to the dye as possible without sacrificing selectivity. Selectivity is the capability of isolating a portion of the fluorescence spectrum of the dye from potentially interfering background fluorescence. The purpose of colour filters in

49、 a fluorimeter is to limit the light reaching the sensing devices as far as possible to that fluoresced by the dye. Filter selection shall be based on: the useful output spectrum of the lamp; the spectral fluorescence characteristics of the dye; potential interference from fluorescence of materials present in the stream; potential interference from light scattered by the sample. Figure 2 shows the excitation and emission spectra of dyes referred to in this pad of ISO9555. Selected dyes and their maximum excitation and emission wavele