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8—COLLECTION OF WATER SAMPLESINTRODUCTIONAs part of its mission, the U.S. Geological Survey (USGS) collectsthe data needed to assess the quality of our Nation’s water resources.The National Field Manual for the Collection of Water-Quality Data(National Field Manual) describes protocols (requirements andrecommendations) and provides guidelines for USGS personnel whocollect those data on surface-water and ground-water resources.Chapter A4 provides information about the collection and qualitycontrol of water samples for investigations and assessments ofenvironmental water quality. Formal training and fieldapprenticeship are necessary in order to implement correctly theprocedures described in this chapter.The National Field Manual is Section A of Book 9 of the USGSpublication series "Techniques of Water-Resources Investigations"(TWRI) and consists of individually published chapters designed tobe used in conjunction with each other. Chapter numbers are precededby an “A” to indicate that the report is part of the National FieldManual. Other chapters of the National Field Manual are referred toin this report by the abbreviation "NFM" and the specific chapternumber (or chapter and section number). For example, NFM 6 refersto Chapter A6 on "Field Measurements" and NFM 6.4 refers to thesection on field measurement of pH.The procedures described in this chapter represent protocols thatgenerally are applicable to USGS studies involving the collection ofwater-quality data. Modification of required and recommendedprocedures to fulfill study objectives or to enhance data quality mustbe documented and published with the data and data interpretation.PURPOSE AND SCOPEThe National Field Manual is targeted specifically toward fieldpersonnel in order to (1) establish and communicate scientificallysound methods and procedures, (2) provide methods that minimizedata bias and, when properly applied, result in data that arereproducible within acceptable limits of variability, (3) encourageconsistent use of field methods for the purpose of producingnationally comparable data, and(4) provide citable documentation forUSGS water-quality data-collection protocols.U.S. Geological Survey TWRI Book 9Chapter A4. (Version 2.0, 9/2006)

COLLECTION OF WATER SAMPLES—9The purpose of this chapter of the National Field Manual is to providefield personnel and other interested parties with a description of therequirements, recommendations, and guidelines routinely used in USGSstudies involving the collection of water-quality samples from bodies ofsurface water and ground water. The information provided covers topicsfundamental to the collection of water samples that are representative ofthe ambient environment. The information provided does not attempt toencompass the entire spectrum of data-collection objectives, sitecharacteristics, environmental conditions, and technological advancesrelated to water-quality studies. Also beyond the scope of this chapter isdiscussion of procedures to collect samples for analysis of suspended orbiological materials. Collection of data related to onsite measurementssuch as pH and alkalinity is addressed in NFM 6, while collection ofbiochemical and microbiological data is addressed in NFM 7.REQUIREMENTS AND RECOMMENDATIONSAs used in the National Field Manual, the terms required andrecommended have USGS-specific meanings.Required (require, required, or requirements) pertains to USGSprotocols and indicates that USGS Office of Water Quality policy hasbeen established on the basis of research and (or) consensus of thetechnical staff and has been reviewed by water-quality specialists andother professionals who have the appropriate expertise. Technicalmemorandums or other documents that define the policy pertinent to suchrequirements are referenced in this chapter. USGS personnel areinstructed to use required equipment or procedures as described herein.Departure from or modifications to the stipulated requirements thatmight be necessary to accomplishing specific data-quality requirementsor study objectives must be based on referenced research and good fieldjudgment, and be quality assured and documented.Recommended (recommend, recommended, recommendation) pertainsto USGS protocols and indicates that, on the basis of research and (or)consensus, the USGS Office of Water Quality recognizes one or severalacceptable alternatives for selecting equipment or procedures. Specificdata-quality requirements, study objectives, or other constraints mightaffect the choice of recommended equipment or procedures. Selectionfrom among the alternatives must be based on referenced research andgood field judgment, and reasons for the selection should be documented.Departure from or modifications to recommended procedures must bequality assured and documented.Collection of Water Samples (Version 2.0, 9/2006)Introduction

10—COLLECTION OF WATER SAMPLESFIELD MANUAL REVIEW AND REVISIONChapters of the National Field Manual are reviewed, revised, and reissuedperiodically to correct any errors, incorporate technical advances, andaddress additional topics. Comments or corrections can be mailed toNFM-QW, USGS, 412 National Center, Reston, VA 20192 (or by e-mail tonfm-owq@usgs.gov). Newly published and revised chapters are posted onthe USGS Web page "National Field Manual for the Collection ofWater-Quality Data." The URL for this page is:http://pubs.water.usgs.gov/twri9A/. The page contains links to an erratapage and to the chapters of the National Field Manual. Informationregarding the status and any errata of this or other chapters can be foundnear the beginning of the Web page for each chapter. Near the bottom ofeach chapter’s Web page are links to archived versions.ACKNOWLEDGMENTSThe information included in this chapter of the National Field Manual isbased on earlier manuals, various reference documents, and a broadspectrum of colleague expertise. Individuals in the USGS too numerous tomention by name developed the field and training manuals that providedthe foundation for information on the collection and processing of watersamples, and others have contributed through peer and editorial reviews tothe technical quality of this document. Editorial assistance provided by IrisM. Collies and production assistance from Loretta J. Ulibarri have beenindispensible in maintaining and enhancing the quality of this report.The current editor owes a debt of gratitude to the original team of authors:Dean B. Radtke, Rick T. Iwatsubo, Jacob Gibs, Wayne W. Webb and RogerW. Lee, and to the following scientists who provided technical review, andwho contributed significantly to the accuracy, quality, and usability of thisreport: Andrew Arnsberg, Bruce A. Bernard, William L. Cunningham, RonG. Fay, Sarah Flanagan, Jacob Gibs, Kathleen K. Fitzgerald, Henry M.Johnson, Michael S. Lico, Jeffrey D. Martin, Timothy D. Oden, Kevin D.Richards, David A. Saad, Terry L. Schertz, Allen M. Shapiro, and StanleyC. Skrobialowski. Special thanks go to Timothy L. Miller for providing thesupport needed to produce a national field manual for water-quality studies.Franceska D. WildeManaging EditorU.S. Geological Survey TWRI Book 9Chapter A4. (Version 2.0, 9/2006)

COLLECTION OF WATER SAMPLES—11COLLECTION OF A4.WATER SAMPLESThis chapter of the National Field Manual (NFM) describes standardUSGS methods (sampling strategies, techniques, requirements, andrecommendations) for the routine collection of representative watersamples. Sample collection forms a continuum with sampleprocessing; therefore, the information in this chapter overlaps withsome of the information in NFM 5, Processing of Water Samples.SAMPLING:The act of collecting a portion ofmaterial for analytical purposes thataccurately represents the materialbeing sampled with respect tostated objectives.Modified from Standard Methods, 1060A(APHA and others, 2001)Before sample collection begins, field personnel must take steps toensure that the samples collected will be representative of the aqueoussystem being investigated. A representative sample is one that typifies(“represents”) in time and space that part of the aqueous system to bestudied, and is delineated by the objectives and scope of the study.Chapter A4. Collection of Water SamplesU.S. Geological Survey TWRI Book 9

12—COLLECTION OF WATER SAMPLESObtaining representative samples is of primary importance for a relevantdescription of the environment. In order to collect a representative samplethat will yield the information required, (1) study objectives, includingdata-quality requirements,1 must be understood in the context of thewater system to be sampled, and (2) artifacts of the sampling processmust be minimized.2 Field personnel must be alert to conditions thatcould compromise the quality of a sample.XCollect a representative sample. Use appropriate methods andquality-assurance measures to ensure that the field sites selectedand the samples collected accurately represent the environmentintended for study and can fulfill data-quality objectives.XThink contamination! To ensure the integrity of the sample, beaware of possible sources of contamination. Contaminationintroduced during each phase of sample collection (andprocessing) is additive and usually is substantially greater thancontamination introduced elsewhere in the sample-handlingand -analysis process. Therefore, collect a sufficient number ofquality-control samples, appropriately distributed in time andspace, to ensure that data-quality objectives and requirementsare met (section 4.3).1Asused in this report, data-quality requirements refer to that subset of data-qualityobjectives pertaining to the analytical detection level for concentrations of targetanalytes and the variability allowable to fulfill the scientific objectives of the study.2 The degree to which a sample can be considered representative of a water bodydepends on many interrelated factors including, for example, temporal and spatialhomogeneity of the water body, sample size, and the method and manner of samplecollection.Collection of Water Samples, Version 2.0 (9/2006)U.S. Geological Survey TWRI Book 9

COLLECTION OF WATER SAMPLES—134.0RESPONSIBILITIES, FIELDPREPARATIONS,AND PREVENTINGSAMPLE CONTAMINATIONThis section of the NFM presents guidelines, requirements, and recommendations for USGS field personnel as they prepare for sample collection at field sites. Collecting comparable data over the duration of thesampling effort and among sampling sites is necessary for a valid analysisand interpretation of the data. This usually requires consistent use of themethods and equipment selected and collection of sufficient quality-control data to verify the quality and comparability of the data collected.USGS data-collection efforts often take a whole-system approach,meaning that the data-collection methods used are designed so that theentire stream reach or aquifer volume is represented. A modifiedapproach is needed for studies in which samples are representative of aspecific portion or aspect of an aqueous system; for example, a study ofaquatic ecology may establish nearshore boundaries on the system ofstudy, and an oil-spill study may target only the surface of a water-tableaquifer.XWhat do your data represent? Data collectors need to know whatquestions the data being collected are meant to address, andunderstand the level of accuracy and precision that are needed in thedata to answer those questions. The data are no better than theconfidence that can be placed in how well the sample represents theaqueous system (Horowitz and others, 1994). Therefore,understand the purpose for which the various types of data will becollected and the aqueous system that each sample shouldrepresent.XAre your data of appropriate quality? Quality-control samplesyield information by which confidence brackets can be applied tothe environmental data. Field quality control is vital for datainterpretation and assessment and yields different information thanlaboratory-performed quality-control checks.Chapter A4. Collection of Water SamplesU.S. Geological Survey TWRI Book 9

14—COLLECTION OF WATER SAMPLESData quality begins before the first sample is collected,by taking care to use proper equipment, being aware ofdata-quality requirements, and being alert to potentialsources of sample contamination.4.0.1RESPONSIBILITIES AND FIELDPREPARATIONSField personnel are responsible for their safety and for the quality ofthe work performed.XNever compromise the safety of field personnel. Be familiarwith the safety requirements and recommendations described inNFM 9. Get the appropriate training and certification needed ifyou will be working at sites designated as hazardous.XCollect data of known quality. Fundamental to water-qualitysampling is the fact that the quality of the analytical results canbe no better than the quality ofthe sample on which the analyseswere performed. The sample collector has primaryresponsibility for the quality and integrity of the sample up tothe time that the sample is delivered to the analyzing laboratoryor office. Data quality is determined from analysis of qualitycontrol data.XKnow what you need to do. Before departing for field work,review the workplan, and plan for the types of measurementsand samples specified.— Be thoroughly familiar with your study objectives andrequirements. Sampling plans, including quality-assuranceand equipment requirements, need to be prepared andreviewed in advance. Some programs r

Chapter A4. (Version 2.0, 9/2006) U.S. Geological Survey TWRI Book 9 U.S. DEPARTMENT OF THE INTERIOR DIRK KEMPTHORNE, Secretary U.S. GEOLOGICAL SURVEY Mark D. Myers, Director Any use of