1、Designation: D 6764 02 (Reapproved 2007)Standard Guide forCollection of Water Temperature, Dissolved-OxygenConcentrations, Specific Electrical Conductance, and pHData from Open Channels1This standard is issued under the fixed designation D 6764; the number immediately following the designation indic
2、ates 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes procedures to collect
3、 cross-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 co
4、nductance,and pH of water flowing in open channels.1.3 This guide describes what equipment should be used tocollect cross-sectional means of temperature, dissolved oxy-gen, specific electrical conductance, and pH of water flowing inopen channels.1.4 This guide covers the cross-sectional means of tem
5、pera-ture, dissolved oxygen, specific electrical conductance, and pHof 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
6、and health practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D 888 Test Methods for Dissolved Oxygen in WaterD 1125 Test Methods for Electrical Conductivity and Re-sistivity of WaterD 1129 Terminology Relating to WaterD 1293
7、 Test Methods for pH of WaterD 4410 Terminology for Fluvial SedimentD 4411 Guide for Sampling Fluvial Sediment in MotionD 5464 Test Methods for pH Measurement of Water of LowConductivity3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this guide, refer toTerminology D 1129 and D
8、4410.3.2 Definitions 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 thermom
9、eterany device used to measure tempera-ture, consisting of a temperature sensor and some type ofcalibrated 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
10、 electrical conductance (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
11、 and fieldinstruments 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 Temper
12、ature, DO, SC, and 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-
13、sectional means of temperature,dissolved oxygen, specific electrical conductance, and pH ofwater flowing in open channels.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.Curr
14、ent edition approved June 15, 2007. Published July 2007. Originallyapproved in 2002. Last previous edition approved in 2002 as D 6764 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume i
15、nformation, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Field measurement must accurately represent the waterflowing in the open channel being measured. Methods
16、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 the open ch
17、annel. 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 system atthe time
18、 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 ensure the
19、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 before leaving fo
20、r 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 measurements, sensors
21、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 readings are defi
22、ned 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.6.1.3 Allow at l
23、east 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 Locating Points
24、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.6.2.2 To obtain
25、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 Terminology
26、 D 4410 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 verticals along t
27、he 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 every 2 year
28、s 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 EWI method
29、.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 in that in
30、crement 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.)6.2.3.2 Select either the in situ or subsample
31、 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 multiple depths) in the vertical. Repeat ateach vertical. The value recorded at each vertical represents the3The boldf
32、ace numbers in parentheses refer to the list of references at the end ofthis guide.TABLE 1 Stabilization Criteria for Recording FieldMeasurements (1)NOTE6, plus or minus value shown; C, degrees Celsius;#less thanor equal to values shown; S/cm microsiemens at 25C, , greater thanvalue shown; unit, sta
33、ndard pH unit; mg/L milligram per liter.Standard DirectField MeasurementStabilization Criteria for Measurements(Variability Should Be Within the Value Shown)Temperature:Electronic Temperature SensorLiquid-in-glass thermometer60.2C60.5CSpecific Electrical Conductance:when # 100 mS/cmwhen 100 mS/cm65%
34、65%pH:Meter displays to 0.01 60.1 unitDissolved oxygen:Amperometric method 60.3 mg/LD 6764 02 (2007)2median 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 eq
35、ual-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 indiv
36、idual 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 the
37、 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 corr
38、ect 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 repo
39、rted 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 ofwidth (
40、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 are w
41、ithdrawn 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-weight
42、ed 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-inte
43、grated sample at the midpoint of each equal-width incre-ment, emptying each sample into a compositing device. Use ofthe 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 R
44、ecord 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 f
45、or 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. Note
46、 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 normal
47、ly 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 situmeasurement
49、can be repeated if stream discharge is highlyvariable and measurement points need to be located at incre-ments of equal discharge. However, in situ measurements arepoint samples, and, thus, are not depth integrated.6.3.2 Measurements made directly (in situ) in the surface-water body are preferable in order to avoid changes that resultfrom removing a water sample from its source. In situmeasurement is necessary to avoid changes in chemical prop-erties of anoxic water.TABLE 2 Example of Field Notes for a Discharge-Weighted Conductivity MeasurementNOTEft/sec,
