1、Designation: D6764 02 (Reapproved 2013)Standard Guide forCollection of Water Temperature, Dissolved-OxygenConcentrations, Specific Electrical Conductance, and pHData from Open Channels1This standard is issued under the fixed designation D6764; the number immediately following the designation indicat
2、es the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes procedures to collect cr
3、oss-sectional means of temperature, dissolved oxygen, specificelectrical conductance, and pH of water flowing in openchannels.1.2 This guide provides guidelines for preparation andcalibration of the equipment to collect cross-sectional means oftemperature, dissolved oxygen, specific electrical condu
4、ctance,and pH of water flowing in open channels.1.3 This guide describes what equipment should be used tocollect cross-sectional means of temperature, dissolvedoxygen, specific electrical conductance, and pH of waterflowing in open channels.1.4 This guide covers the cross-sectional means oftemperatu
5、re, dissolved oxygen, specific electrical conductance,and pH of fresh water flowing in open channels.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and hea
6、lth practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D888 Test Methods for Dissolved Oxygen in WaterD1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD1129 Terminology Relating to WaterD1293 Test Metho
7、ds for pH of WaterD4410 Terminology for Fluvial SedimentD4411 Guide for Sampling Fluvial Sediment in MotionD5464 Test Method for pH Measurement of Water of LowConductivity3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology D1129 and D4410.3.2 Definiti
8、ons of Terms Specific to This Standard:3.2.1 electronic temperature sensoran electrical devicethat converts changes in resistance to a readout calibrated intemperature units. Thermistors and resistance temperaturedetectors are examples of electronic temperature sensors.3.2.2 thermometerany device us
9、ed to measuretemperature, consisting of a temperature sensor and some typeof calibrated scale or readout device.4. Summary of Guide4.1 This guide establishes criteria and describes proceduresfor the collection of cross-sectional means of temperature,dissolved oxygen (DO), specific electrical conduct
10、ance (SC),and pH of water flowing in open channels.4.2 This guide provides only generic guidelines for equip-ment use and maintenance. Field personnel must be familiarwith the instructions provided by equipment manufacturers.There are a large variety of available field instruments and fieldinstrumen
11、ts are being continuously updated or replaced usingnewer technology. Field personnel are encouraged to contactequipment manufacturers for answers to technical questions.5. Significance and Use5.1 This guide describes stabilization criteria for recordingfield measurements of Temperature, DO, SC, and
12、pH.5.2 This guide describes the procedures used to calibrateand check meters to be used in the field to records thesemeasurements and the procedures to be use in the field toobtain these data.5.3 This guide describes quality assurance procedures to befollowed when obtaining cross-sectional means of
13、temperature,1This guide is under the jurisdiction of ASTM Committee D19 on Water and isthe direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology,and Open-Channel Flow.Current edition approved Jan. 1, 2013. Published January 2013. Originallyapproved in 2002. Last previous edition a
14、pproved in 2007 as D6764 02(2007).DOI: 10.1520/D6764-02R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Co
15、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1dissolved oxygen, specific electrical conductance, and pH ofwater flowing in open channels.5.4 Field measurement must accurately represent the waterflowing in the open channel being measur
16、ed. Methods need tobe used that will result in an accurate representation of themean of the parameter of interest. Procedures must be used thatwill take into consideration the variation in the parameteracross the sections and with depth.5.5 Temperature and DO must be measured directly in thewater in
17、 the open channel. SC and pH are often measured insitu, but also may be measured in a subsample of a compositesample collected using discharge-weighted methods.6. ProcedureGeneral Comments6.1 Field measurements should represent, as closely aspossible, the natural condition of the surface-water syste
18、m atthe time of sampling. Field teams must determine if theinstruments and method to be used will produce data of thetype and quality required to fulfill study needs. Experience andknowledge of field conditions often are indispensable fordetermining the most accurate field-measurement value.6.1.1 To
19、 ensure the quality of the data collected (1)3:6.1.1.1 Calibration is required at the field site for mostinstruments. Make field measurements only with calibratedinstruments.6.1.1.2 Each field instrument must have a permanent log-book for recording calibrations and repairs. Review the log-book befor
20、e leaving for the field.6.1.1.3 Test each instrument (meters and sensors) beforeleaving for the field. Practice your measurement technique ifthe instrument or measurement is new to you.6.1.1.4 Have backup instruments readily available and ingood working condition.6.1.2 Before making field measuremen
21、ts, sensors must beallowed to equilibrate to the temperature of the water beingmonitored. Sensors have equilibrated adequately when instru-ment readings have “stabilized,” that is, when the variabilityamong measurements does not exceed an established criterion.The criteria for stabilized field readi
22、ngs are defined operation-ally in Table 1, for a set of three or more sequential measure-ments. The natural variability inherent in surface water at thetime of sampling generally falls within these stability criteriaand reflects the accuracy that should be attainable with acalibrated instrument.6.1.
23、3 Allow at least 60 s (or follow the manufacturersguidelines) for sensors to equilibrate with sample water. Takeinstrument readings until the stabilization criteria in Table 1 aremet. Record the median of the final three or more readings asthe value to be reported for that measurement point.6.2 Loca
24、ting Points of Measurement in Cross-Section:6.2.1 The location and the number of field measurementsdepend on study objectives. Generally, a single set of field-measurement data is used to represent an entire stream crosssection at a sampling site and can be useful when calculatingchemical loads.6.2.
25、2 To obtain data representative of the section, thevariability of discharge and field measurements across thestream must be known. This information is used to determineif the equal-discharge-increment (EDI) or equal-width-increment (EWI) method of locating field-measurement pointsshould be used. See
26、 Terminology D4410 for definitions ofthese terms.6.2.2.1 Check the cross-sectional profile data of the streamsite to determine the variability of discharge per unit width ofthe stream and of field-measurement values across the section.Make individual measurements at a number of equally-spaced vertic
27、als along the cross section and at multiple depthswithin each vertical; or, consult previous records for the site.Make in situ (see 6.2.3.3) field measurements for theprofile.Field-measurement profiles of stream variability areneeded for low- and high-flow conditions and should beverified at least e
28、very 2 years or as study objectives dictate.6.2.2.2 Select the EDI or EWI method to locate points ofmeasurement (see reference (2) for information on EDI andEWI methods) to select and execute the appropriate method.If stream depth and velocities along the cross section arerelatively uniform, use the
29、 EWI method.If stream depth and velocities along the cross section arehighly variable, use the EDI method.In a small and well-mixed stream, a single point at thecentroid of flow may be used to represent the cross section. Thecentroid of flow is defined as the point in the increment atwhich discharge
30、 in that increment is equal on both sides of thepoint.6.2.3 Use the following procedure when making a fieldmeasurement using the EDI method.6.2.3.1 Divide the cross section into equal increments ofdischarge (see reference (1) for details on how to properly dothis.)3The boldface numbers in parenthese
31、s refer to the list of references at the end ofthis guide.TABLE 1 Stabilization Criteria for Recording FieldMeasurements (1)NOTE 1, plus or minus value shown; C, degrees Celsius; lessthan or equal to values shown; S/cm microsiemens at 25C, , greaterthan value shown; unit, standard pH unit; mg/L mill
32、igram per liter.Standard DirectField MeasurementStabilization Criteria forMeasurements(Variability Should BeWithin the Value Shown)Temperature:Electronic Temperature SensorLiquid-in-glass thermometer0.2C0.5CSpecific Electrical Conductance:when # 100 mS/cmwhen 100 mS/cm5 %5 %pH:Meter displays to 0.01
33、0.1 unitDissolved oxygen:Amperometric method0.3 mg/LD6764 02 (2013)26.2.3.2 Select either the in situ or subsample method andfollow the instructions in 6.3 or 6.4.6.2.3.3 In Situ MethodGo to the centroid of the firstequal-discharge increment. Using submersible sensors, mea-sure at mid-depth (or mult
34、iple depths) in the vertical. Repeat ateach vertical. The value recorded at each vertical represents themedian of values observed within approximately 60 s aftersensor(s) have equilibrated with stream water.6.2.3.4 Subsample MethodCollect an isokinetic depth-integrated sample at the centroid of each
35、 equal-dischargeincrement, emptying the increment sample into a compositingdevice. Measure field parameters either in the sample collectedat each increment or in a subsample taken from the compositeof all the increment samples.6.2.3.5 The final field-measurement value is the mean of thein situ or in
36、dividual increment-sample value for all the EDIverticals in the section (the composite subsample yields asingle value). Note for pH it is necessary to calculate the meanby (1) converting each pH measurement to its antilogarithmtimes minus one (10-(pH), (2) using these transformed values tocalculate
37、the mean, and (3) converting the mean value to alogarithm multiplied by minus one (refer to 6.8.4.5).6.2.3.6 Enter data on a field form.6.2.3.7 ExampleTable 2 is an example of how meanconductivity measured in situ is calculated using the equal-discharge-increment method.6.2.3.8 In the example, the c
38、orrect value for the discharge-weighted mean conductivity is 163 S/cm, calculated from 815divided by 5 (the sum of the recorded median values divided bythe number of median measurements). Note that at the mid-point of the center centroid of flow (increment 3) the medianconductivity would have been r
39、eported as 155 S/cm; ifconductivity had been measured near the left edge of the water(increment 1), the conductivity would have been reported as185 S/cm.6.2.4 Use the following procedure when making a fieldmeasurement using the EWI method.6.2.4.1 Divide the cross section into equal increments ofwidt
40、h (see reference (1) for details on how to properly do this.)6.2.4.2 In situ field measurements are made at the midpointsof each increment. Area-weighted concentrations can be com-puted from these measurements (Table 3).6.2.4.3 Subsample field measurements are made in discretesamples that usually ar
41、e withdrawn from a composite samplecollected using an isokinetic sample and isokinetic depth-integrating method. The volume of the isokinetic sample mustbe proportional to the amount of discharge in each incrementand measurements in subsamples taken from the compositingdevice result in discharge-wei
42、ghted values.6.2.4.4 Select either the in situ or subsample method andfollow the instructions in 6.3 or 6.4.6.2.4.5 In Situ MethodMeasure at the midpoint of eachequal-width increment. Using submersible sensors, measure atmid-depth in the vertical.6.2.4.6 Subsample MethodCollect an isokinetic depth-i
43、ntegrated sample at the midpoint of each equal-widthincrement, emptying each sample into a compositing device.Use of the correct sampling equipment is critical to execute thismethod successfully: standard samplers cannot meet isokineticrequirements when stream velocity is less than 1.5 ft/s.6.2.4.7
44、Record a value for each field measurement for eachvertical. The value recorded represents the stabilized valuesobserved within approximately 60 s after the sensor(s) haveequilibrated with the stream or subsample water.6.2.4.8 ExampleTable 3 provides an example of an area-weighted median measurement
45、for conductivity measured insitu. In the example, the area-weighted median conductivityequals 130 S/cm. To calculate an area-weighted median,multiply the area of each increment by its corresponding fieldmeasurement, sum the products of all the increments, anddivide by total cross-sectional area. Not
46、e that if the conductiv-ity reported was selected at mid-depth of the vertical ofcentroid of flow (Section 10), it would have been reported as125 S/cm; if the conductivity reported was near the left edgeof water, it would have been reported as 150 S/cm.6.2.4.9 The final field-measurement value norma
47、lly is cal-culated as the mean of the values recorded at all EWIincrements, resulting in an area-weighted mean (for pH it isnecessary to calculate the mean by (1) converting each pHmeasurement to its antilogarithm times minus one (10-(pH), (2)using these transformed values to calculate the mean, and
48、 (3)converting the mean value to a logarithm multiplied by minusone.)6.3 In Situ Measurement Procedures :6.3.1 In situ measurement (Fig. 1), made by immersing afield-measurement sensor directly in the water body, is used todetermine a profile of variability across a stream section. In situTABLE 2 Ex
49、ample of Field Notes for a Discharge-Weighted Conductivity MeasurementNOTE 1ft/sec, feet per second; ft, feet; ft2, square feet; ft3/s, cubic feet per second; S/cm, microsiemens per centimeter at 25C; LEW, left edgeof water; , not available; REW, right edge of water.Equal DischargeIncrementPercent of Flowin IncrementMean Velocity,in ft/sWidth ofIncrement,in ftDepth ofIncrement,in ftArea of Increment,in ft2Increment Discharge,in ft3/sMedian Conductivity,in S/cmLEW 0 1 20 2.0 22 5.7 125 250 1852 20 2.2 11 10.4 114 250 1703 20 2.3 9 1
