Quality Assurance Report for the 2018-19 National Rivers and Streams Assessment Fish Fillet Tissue Study


£%	United States

Environmental Protectio
^1 M^k. Agency

Office of Water

www.epa.gov	December 2022

Quality Assurance Report for the
2018-19 National Rivers and Streams
Assessment Fish Fillet Tissue Study

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U.S. Environmental Protection Agency
Office of Water
Office of Science and Technology (4305T)
Standards and Health Protection Division
1200 Pennsylvania Avenue, NW
Washington, DC 20460

EPA 820-F-22-008

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Table of Contents

Page

Acknowledgements	ii

Disclaimer	ii

Contact 	ii

Chapter 1 Introduction	1

Section 1.1 Background	1

Section 1.2 Study Design	1

Section 1.3 Study Participants	2

Section 1.4 Study Results	3

Chapter 2 Quality Assurance Program	5

Section 2.1 Quality Assurance Proj ect Plans	5

Section 2.2 Training	5

Section 2.3 Sample Preparation and Analysis QA/QC	6

Section 2.4 QA Oversight of Laboratory Operations	7

Chapter 3 Preparation and Analysis Methods	8

Section 3.1 Preparation of Fish Tissue Samples	8

Section 3.2 Analysis of Fish Tissue Samples for Mercury	8

Section 3.3 Analysis of Fish Tissue Samples for PCBs	9

Section 3.4 Analysis of Fish Tissue and Rinsate Samples for PFAS	9

Section 3.5 Analysis of Rinsates and Solvent Blanks	9

Section 3.6 Quality Control Procedures	10

Chapter 4 Data Quality Assessment	12

Section 4.1 Data Review	12

Section 4.2 Analysis of Blanks	14

Section 4.3 Analysis of Laboratory Control Samples	15

Section 4.4 Analysis of Matrix Spike and Laboratory Duplicate Samples	16

Section 4.5 Labeled Compounds	17

Section 4.6 Ion Abundance Ratios	18

Section 4.7 Other QC parameters	19

Section 4.8 Completeness	19

References	20

List of Tables

Page

Table 1.	Quality Control Activities for Analysis of Fish Tissue Samples	10

Table 2.	Quality Control Activities for Analysis of Rinsates	11

Table 3.	Individual SCC Codes Applied to the 2018-19 NRSA Results	13

Table 4.	Matrix Spike and Duplicate Sample Requirements by Analysis Type	17

List of Figures

Page

Figure 1.	2018-19 NRSA Fish Fillet Tissue Study sampling locations	2

Figure 2.	NRSA proj ect team organization	4

Figure 3.	Impacts of Blank Contamination on the PCB Results	15

Figure 4.	Impacts of LCS Recoveries on the PFAS Results	16

Figure 5.	Impacts of Labeled Compound Recovery on the PFAS Results	18

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Acknowledgements

This quality assurance report was prepared by the U.S. Environmental Protection Agency, Office of
Water (OW), Office of Science and Technology (OST), Standards and Health Protection Division
(SHPD). The EPA Project Manager for the study was Leanne Stahl, who provided overall project
coordination and technical direction. Tetra Tech, Inc. provided field support for the study under Contract
Number EP-C-14-016. Quality assurance and analytical subcontracting support was provided by General
Dynamics Information Technology (GDIT) and several predecessor organizations, including Computer
Science Government Solutions (CSGov) and CSRA, hereafter collectively referred to as GDIT, under
Contract Number EP-C-17-024. GDIT was responsible for production of this report under the direction
of Leanne Stahl and John Healey.

Disclaimer

The U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology has
approved this report for publication. Mention of trade names, commercial products, or services does not
constitute official EPA approval, endorsement, or recommendation for use.

Contact

Please address questions and comments to:

John Healey

Standards and Health Protection Division
Office of Science and Technology
Office of Water (4305T)

US Environmental Protection Agency
1200 Pennsylvania Ave, NW
Washington, DC 20460
healey.john@epa.gov

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Chapter 1
Introduction

This report documents the quality of data gathered during EPA's 2018-19 National Rivers and Streams
Assessment (NRSA), a probability-based survey designed to assess the condition of the nation's river and
stream resources. The 2018-19 NRSA included collection and analysis of physical, chemical, and
biological indicator data that will allow a statistically valid characterization of the condition of the
nation's rivers and streams. The Office of Wetlands, Oceans, and Watersheds (OWOW) within the
Office of Water (OW) was responsible for the overall planning and implementation of the 2018-19
NRSA.

One component of the 2018-19 NRSA is the Fish Fillet Tissue Study, which is designed to examine
national fish contamination trends in U.S. rivers. EPA's Office of Science and Technology (OST) within
OW collaborated with the Office of Research and Development Pacific Ecological Systems Division
(ORD-PESD) in Corvallis, Oregon, to plan and implement the fish fillet tissue study under the 2018-19
NRSA. By the end of the 2019 field sampling season, whole fish composite samples (for fillet analysis)
were collected from 290 sites. This report documents the quality of data gathered during the 2018-19
NRSA Fish Fillet Tissue Study.

Section 1.1 Background

Obtaining statistically representative occurrence data on multiple contaminants in fish tissue is a priority
area of interest for EPA. Since 1998, OW has collaborated with ORD to conduct a series of national- and
regional-scale assessments of contaminants in fish tissue through statistically based studies of U.S. lakes
and rivers. These EPA studies are referred to as the National Lake Fish Tissue Study, the 2008-09
NRSA, the 2013-14 NRSA, the Great Lakes Human Health Fish Tissue Study conducted under the 2010
National Coastal Condition Assessment (NCCA), and the Great Lakes Human Health Fish Fillet Tissue
Study conducted under the 2015 NCCA. The 2018-19 NRSA provided additional national data on the
occurrence and distribution of contaminants in the fillet tissue from river fish and, through comparison
with the 2013-14 NRSA fish tissue results, allowed EPA to examine temporal trends.

Section 1.2 Study Design

OST collaborated with OWOW and with ORD-PESD in Corvallis, Oregon, to plan and implement the
fish fillet indicator within the framework of the 2018-19 NRSA. Fish composite samples were collected
during June through September of 2018 and extended into November for the 2019 field season at a
statistical subset of approximately 290 sites in the NRSA framework (Figure 1). A total of 477 sites were
selected and scheduled for sampling; however, due to local restrictions and weather conditions, only 290
sites provided adequate samples for analysis.

The following were the key design components for the 2018-19 NRSA fish fillet tissue study:

• Sampling approximately 290 randomly selected sites during 2018 and 2019, subject to local
conditions and restrictions.

• Collecting one fish composite sample for human health applications (i.e., five similarly sized
adult fish of the same species that are commonly consumed by humans) from each site.

• Shipping whole fish samples to a commercial laboratory for storage and fish sample preparation,
which includes collection of tissue plug samples for mercury analysis before filleting the fish,
removing both fillets from each fish, homogenizing the fillet tissue composites, and preparing

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fillet tissue aliquots for analysis of mercury, per- and poh fluoroalkyl substances (PFAS) and
polychlorinated biphenyls (PCBs).

• Analyzing all the fillet tissue samples for mercury (total), PCBs, and PFAS.

EPA stored the 2018-19 NRSA whole fish samples in freezers leased by GDIT at Microbac Laboratories
in Baltimore, Maryland, prior to transporting them to the sample preparation laboratory. Tetra Tech's
Center for Ecological Sciences in Owings Mills, Maryland, was the sample preparation laboratory
preparing the homogenized fish fillet tissue samples and rinsates for analysis as outlined in the fourth
bullet above. The sample preparation laboratory prepared aliquots of fillet tissue for mercury, PCBs,
PFAS, and archive tissue samples to allow for further analysis of 2018-19 NRSA samples in the future.
Commercial environmental laboratories analyzed the 2018-19 NRSA fish fillet tissue samples for
mercury, PCB congeners, and PFAS, under project-specific purchase orders issued by GDIT. Procedures
for handling and shipping homogenized fish tissue samples to Microbac and the analysis laboratories are
described in Appendix B of the Quality Assurance Project Plan for Preparation of Fish Fillet Tissue
Samples for the 2018-19 National Rivers and Streams Assessment (USEPA 2018b).

Note: Unless othem'ise modified, all references to "fish " and "samples " in this report refer to
homogenized fish fillet tissue samples prepared by Tetra Tech.

Section 1.3 Study Participants

The 2018-19 NRSA project team consisted of managers, scientists, statisticians, and QA personnel in
OST, and ORD-WED, along with contractors providing scientific and technical support to OST from
GDIT and Tetra Tech, Inc. (Figure 2). Project team members from OST provided support for developing

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and reviewing technical and program information related to all aspects of the study, including training
materials, standard operating procedures, QAPPs, analytical QA reports, briefings and reports on study
results, and outreach materials. Key members of the project team are listed below.

• Leanne Stahl, OST NRSA fish fillet tissue study Technical Leader and OST Project Manager,
provided overall direction for planning and implementation of this fillet tissue study being
conducted under the NRSA.

• Marion Kelly, OST Quality Assurance Officer, was responsible for reviewing and approving all
QAPPs that involve scientific work being conducted by OST with support from Bill Kramer, the
Standards and Health Protection Division QA Coordinator.

• Blaine Snyder, Tetra Tech Project Leader, was responsible for managing all aspects of the
technical support being provided by Tetra Tech staff for the NRSA fish fillet tissue study.

• Susan Lanberg was the Tetra Tech QA Officer.

• Yildiz Chambers-Velarde, GDIT Work Assignment Lead, was responsible for managing all
aspects of the technical support being provided by GDIT staff for the 2018-19 NRSA fish fillet
tissue study.

• Harry McCarty, GDIT Project Leader, was responsible for managing all aspects of the technical
support being provided by GDIT staff for the NRSA fish fillet tissue study.

• Marguerite Jones was the GDIT QA Officer.

• Tony Olsen, Senior Statistician at ORD-WED in Corvallis, Oregon, supported the NRSA fish
fillet tissue study by providing technical expertise for study planning and implementation.

Two commercial laboratories analyzed the 2018-19 NRSA fish tissue samples for mercury, PCBs, and
PFAS, under purchase orders issued by GDIT, as shown below and in Figure 2.

Laboratory Analysis Type

ALS-Environmental Mercury

SGS-AXYS Analytical PCB congeners

SGS-AXYS Analytical PFAS

Section 1.4 Study Results

EPA posted the final analytical results for all of the samples in this study in MS Excel files at:

https://www.epa.gov/fish-tech/2018-2019-national-rivers-and-streams-assessment-fish-tissue-study

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Figure 2. NRSA project team organization

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Chapter 2
Quality Assurance Program

At the beginning of the study, EPA managers recognized that data gathered from the study would be used
extensively by individuals responsible for making environmental, economic, and policy decisions.
Environmental measurements always contain some level of uncertainty. Decision makers, therefore, must
recognize (and have the means to assess) the uncertainty associated with the data on which their decisions
are based. In recognition of this, the study managers established a quality assurance (QA) program to
ensure that data produced under the study would meet defined standards of quality.

Section 2.1 Quality Assurance Project Plans

Three separate Quality Assurance Project Plans (QAPPs) are associated with this study. In 2018, OWOW
developed the National Rivers and Streams Assessment 2018-2019: Quality Assurance Project Plan
(USEPA 2018a) that contains elements of the overall project management, data quality objectives,
measurement and data acquisition, and information management for the NRSA, and is based on the
guidelines developed and followed in the Western Environmental Monitoring and Assessment Program
(EMAP).

Also in 2018, OST developed the Quality Assurance Project Plan for Preparation of Fish Fillet Tissue
Samples for the 2018-19 National Rivers and Streams Assessment that described the procedures for
preparing composite fish tissue samples (USEPA 2018b).

On August 1, 2019, OST developed the Quality Assurance Project Plan for Sample Analysis for the
2018-19 National Rivers and Streams Assessment Fish Fillet Indicator that described the requirements for
mercury analysis (USEPA 2019a). On August 27, 2019, the first revision to the OST QAPP was released
to include the requirements for PCB analysis (USEPA 2019b). The second and final revision to the
QAPP was issued later in November 2019, which added the requirements for PFAS analysis (USEPA
2019c).

Section 2.2 Training

Fish Tissue Sample Preparation

Specialized training was provided for the laboratory technicians who prepared fish tissue fillets,
homogenates, and rinsates for the study. Training workshops were conducted at Tetra Tech Biological
Research Facility in Owings Mills, Maryland for all laboratory staff involved with 2018-19 NRSA fish
tissue sample preparation, to accomplish the following objectives:

•	present NRSA fish tissue preparation, homogenization and distribution procedures described in
Appendix B to the QAPP,

•	demonstrate filleting and homogenizing techniques with fish from invalid 2018-19 NRSA samples,
and

•	provide hands-on opportunities for fish preparation laboratory staff to become proficient at filleting
and homogenizing fish samples.

Analysis of Fish Tissue Samples

All laboratory staff involved in the analysis of fish tissue samples were required to be proficient in the
associated tasks, as required by each analytical laboratory's existing quality system. All GDIT staff

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involved in analytical data review and assessment were already proficient in data review, therefore no
specialized training was required for data reviewers for this project.

Section 2.3 Sample Preparation and Analysis QA/QC

EPA integrated various QA/QC activities into the study to ensure data comparability and generate
analytical data of known quality during preparation and analysis of the fish tissue samples and evaluation
of analytical data quality. There were separate QA/QC activities associated with the preparation of the
fish fillet samples and the analyses of those samples.

Following is a summary of the critical QA/QC components associated with the sample preparation
process:

•	Development and implementation of the sample preparation activities QAPP (USEPA 2018b)

•	Use of one laboratory for sample preparation (filleting, tissue homogenization, and preparation of
tissue aliquots)

•	Requirement for triplicate lipid analyses to test for tissue homogeneity during sample preparation

•	Requirement for preparation equipment rinsate samples and solvent blanks with each batch fish fillet
tissue samples prepared

•	Requirement for analyses of the rinsate samples and solvent blanks for mercury, selected PCB
congeners, and PFAS

•	Review and acceptance of mercury and PCB rinsate results by EPA before proceeding with
preparation of additional samples

Following is a summary of the critical QA/QC components associated with the sample analysis process:

•	Development and implementation of the analytical activities QAPP (USEPA 2019a, 2019b, and
2019c)

•	Use of one laboratory for the analyses of a given class of analytes

•	Identification of quantifiable measurement quality objectives

•	Use of pure and traceable reference standards

•	Demonstration of instrument calibration and system performance

•	Periodic calibration verification

•	Analysis of QC samples to assess performance of analytical methods

•	Specification of method detection limits (MDLs) and method/chemical QC acceptance criteria that
applied throughout the study

•	Use of a standardized data quality assessment process

The general measurement quality objective (MQO) for the study was to satisfy method-specific
performance criteria. The analytical activities QAPP provides a summary of the method performance
criteria and specifies MQOs and QC acceptance criteria to assess the bias and precision associated with
the analytical methods used for this study. Chapter 4 of this report describes the process for data quality
assessment and presents the results of these assessments, which includes data from the following
laboratory QC samples or measures: blanks, recoveries for isotopically labeled compounds spiked into
field-based tissue samples, matrix spike (MS) samples, laboratory duplicate samples, laboratory control
samples, and calibration verifications. Chapter 4 also includes a discussion of data completeness for the
study.

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Section 2.4 QA Oversight of Laboratory Operations

The GDIT Project Leader scheduled and tracked all analytical work performed by laboratories for
mercury, PCB, and PFAS analyses. The GDIT Project Leader also coordinated with staff at Tetra Tech
regarding fish tissue sample shipments.

When samples were shipped to an analytical laboratory, the GDIT Project Leader contacted designated
laboratory staff by email to notify them of the forthcoming shipment(s) and request that they contact
GDIT if the shipments did not arrive intact, as scheduled. Within 24 hours of scheduled sample receipt,
GDIT contacted the laboratory to verify that the samples arrived in good condition, and if problems were
noted, GDIT worked with the laboratory and EPA to resolve any problems as quickly as possible to
minimize data integrity problems.

GDIT communicated periodically with laboratory staff by telephone or email to monitor the progress of
analytical sample preparation, sample analysis, and data reporting. If any technical problems were
encountered during sample preparation and analysis, GDIT identified a technical expert within GDIT to
assist in resolving the problem, and work with EPA to identify and implement a solution to the problem.
In cases in which the laboratory failed to deliver data on time, or if the laboratory notified GDIT of
anticipated reporting delays, GDIT notified the EPA Project Manager. To the extent possible, GDIT
adjusted schedules and shifted resources within GDIT as necessary to minimize the impact of any
laboratory delays on EPA schedules. GDIT also immediately notified the Project Manager of any
laboratory delays that were anticipated to affect EPA schedules.

Finally, the GDIT Project Leader monitored the progress of the data quality audits (data reviews) and
database development to ensure that each laboratory data submission was reviewed in a timely manner. If
dedicated staff were not able to meet EPA schedules, GDIT identified additional staff who were qualified
and capable of reviewing the data so that EPA schedules could be met. In cases when such resources
could not be identified, and if training new employees was not feasible, GDIT met with the EPA Project
Manager to discuss an appropriate solution.

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Chapter 3
Preparation and Analysis Methods

To control variability among tissue sample results, all samples collected during the study were analyzed
by a single set of methods, and all analyses performed with a given method were performed by only one
laboratory. Further control of variability was ensured by utilizing a single laboratory to prepare,
composite, homogenize, and aliquot samples in a strictly controlled, contaminant-free environment. The
methods employed by the sample preparation laboratory and by the three analysis laboratories are
described below.

Section 3.1 Preparation of Fish Tissue Samples

Tetra Tech served as the fish sample preparation laboratory for the study. In this role, Tetra Tech was
responsible for filleting each valid fish sample, homogenizing the fillet tissue, preparing the required
number of fish tissue aliquots for analysis and archive, shipping the fish tissue aliquots for each analysis
to the designated analytical laboratory, and storing archived fish tissue samples in a freezer at its facility.
The specific procedures for all 2018-19 NRSA fish sample preparation activities are described in
Appendix B of the 2018-19 NRSA fish fillet sample preparation QAPP (USEPA 2018b).

Fish were prepared by trained technicians, using thoroughly cleaned utensils and cutting boards (cleaning
procedures are detailed in the sample preparation QAPP for the study). Each fish was weighed to the
nearest gram wet weight, rinsed with deionized water, and filleted on a glass cutting board. Fillets from
both sides of each fish were prepared with scales removed, skin on, and belly flap (ventral muscle and
skin) attached. Fillets were composited using the "batch" method, in which all of the individual
specimens that comprise the sample were homogenized together, regardless of each individual specimen's
proportion to one another (as opposed to the "individual" method, in which equal weights of each
specimen are added together).

An electric meat grinder was used to homogenize the fillet tissue. Entire fillets (with skin and belly flap)
from both sides of each fish were homogenized, and the entire homogenized volume of all fillets from the
fish sample was used to prepare the tissue sample. Tissues were mixed thoroughly until they were
completely homogenized as evidenced by a fillet homogenate that consisted of a fine paste of uniform
color and texture. Homogeneity was confirmed by conducting triplicate analyses of the lipid content in
one of every twenty samples. The collective weight of the homogenized tissue from each sample was
recorded to the nearest gram (wet weight) after processing. Tetra Tech prepared fillet tissue aliquots
according to the specifications listed in the fish sample preparation procedures in Appendix B of the
2018-19 NRSA fish fillet sample preparation QAPP (USEPA 2018b).

Section 3.2 Analysis of Fish Tissue Samples for Mercury

Fish tissue samples were prepared and analyzed by ALS-Environmental (Kelso, WA), using Procedure I
from "Appendix to Method 1631, Total Mercury in Tissue, Sludge, Sediment, and Soil by Acid Digestion
and BrCl Oxidation" from Revision B of Method 1631 (1631B) for sample preparation (USEPA 2001),
and Revision E of Method 1631 (163 IE) for the analysis of mercury in fish tissue samples (USEPA
2002). This laboratory utilized approximately 0.5 g of tissue for analysis. The sample was digested with
a combination of nitric and sulfuric acids. The mercury in the sample was oxidized with bromine
monochloride (BrCl) and analyzed by cold-vapor atomic fluorescence spectrometry. Tissue sample
results were reported based on the wet weight of the tissue sample, in nanograms per gram (ng/g).

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Section 3.3 Analysis of Fish Tissue Samples for PCBs

The PCB samples were prepared and analyzed by SGS-AXYS Analytical Services Ltd. (Sidney, BC,
Canada), in general accordance with EPA Method 1668C (USEPA 2010) and as detailed in the
laboratory's SOP. The samples were analyzed for all 209 PCB congeners and reported as either
individual congeners or coeluting groups of congeners. The SGS-AXYS SOP deviated from the
published EPA method in several aspects, including:

• An anthropogenic isolation column was not used for cleanup

• The Soxhlet extraction apparatus was cleaned with toluene instead of dichloromethane

• The CALVER solution contained all 209 PCB congeners instead of only the 27 PCB congeners in
Table 4 of Method 1668C.

The entire list of modifications is presented in detail in the 2018-19 NRSA sample analysis QAPP. These
changes fall within the method's established allowance for flexibility, and EPA accepted these deviations
from Method 1668C for the purposes of the study.

The laboratory utilized approximately 10 g of tissue for the analysis. The samples were extracted with
methylene chloride and analyzed by high resolution gas chromatography-mass spectrometry
(HRGC/MS). Tissue sample results were reported based on the wet weight of the tissue sample, in
nanograms per gram (ng/g).

Section 3.4 Analysis of Fish Tissue and Rinsate Samples for PFAS

At the time of this study, there were no formal analytical methods from EPA or any voluntary consensus
standard bodies for the PFAS analyses of tissue samples. Therefore, fish tissue samples were analyzed by
SGS-AXYS (Sidney, BC, Canada) using procedures developed, tested, and documented in that
laboratory. The SOP for the procedure is considered proprietary by the laboratory. However, the SOP
was reviewed by GDIT, and the analytical procedure is briefly described below.

Approximately 2 g of fish tissue was required for analysis. If matrix-related analytical problems were
identified during the analysis of a given fish tissue sample, a sample aliquot of 1 g was used to minimize
those problems. The samples were spiked with 24 isotopically labeled standards and extracted by shaking
in a caustic solution of methanol, water, potassium hydroxide, and acetonitrile. The hydroxide solution
breaks down the tissue and allows the PFAS analytes to be extracted into the solution.

After extraction, the solution was centrifuged to remove the solids and the supernatant liquid diluted with
reagent water and processed by solid-phase extraction (SPE) on a weak anion exchange sorbent. The
PFAS analytes were eluted from the SPE cartridge and the eluant spiked with additional labeled recovery
standards and analyzed by high performance liquid chromatography with tandem mass spectrometry.

The concentration of each PFAS analyte is determined using the responses from one of the 13C- or
deuterium-labeled standards added prior to sample extraction, applying the technique known as isotope
dilution. As a result, the target analyte concentrations are corrected for the recovery of the labeled
standards, thus accounting for extraction efficiencies and losses during cleanup. Tissue sample results
were reported based on the wet weight of the tissue sample, in nanograms per gram (ng/g).

Section 3.5 Analysis of Rinsates and Solvent Blanks

As noted in Section 2.3, Tetra Tech prepared equipment rinsate samples with each batch of fish fillet
tissue samples. Aqueous rinsates were prepared for mercury and PFAS, and hexane rinsates were
prepared for PCBs. Paired rinsate and solvent blank samples were analyzed for mercury and PCBs by

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subcontract laboratories under the control of Tetra Tech. ALS (Kelso, WA) analyzed the rinsate and
solvent blank samples for mercury using EPA Method 245.1 (USEPA 1983), while ALS (Burlington,
Ontario) analyzed the rinsate and solvent blank samples for PCBs using EPA Method 1668C. Results for
mercury were reported in micrograms per liter ((.ig/L). and PCBs were reported in picograms per milliliter
(pg/mL), which is equivalent to nanograms per liter (ng/L).

Tetra Tech stored the aqueous rinsate and solvent blank samples for PFAS analyses until EPA obtained
the funding for the tissue analysis laboratories. PFAS rinsate and solvent blank samples were analyzed by
AXYS Analytical Services (Sydney, BC, Canada) at the same time as the analyses of the fish fillet tissue
samples, but with an extraction step based on EPA Method 537 from the Office of Ground Water and
Drinking Water (USEPA 2009). Results for PFAS were reported in ng/L.

Section 3.6 Quality Control Procedures

Fish Tissue Analyses

The analytical procedures applied by the laboratories designated for analysis of 2018-19 NRSA fish tissue
samples included many of the traditional EPA analytical quality control activities. For example, all
samples were analyzed in batches and each batch included:

•	up to 20 samples, including both field samples and QC samples

•	blanks - 5% of the samples within a batch are method blanks

Other quality control activities for fish tissue samples varied by the analysis type, as described in Table 1.

Table 1. Quality Control Activities for Analysis of Fish Tissue Samples

Analyte Type

Quality Control Sample

Frequency

Mercury

Bubbler blank

3 blanks run during calibration and with each analytical batch of
up to 20 field samples

Method blank

3 method blanks per batch of up to 20 field samples, with
analyses interspersed among the samples in the analysis batch

Laboratory control sample

Once per batch of up to 20 field samples, prior to the analysis of
any field samples, and again at the end of each analytical batch,
spiked at 4.0 ng

Matrix spike and matrix
spike duplicate samples

Once per every 10 field samples (e.g., twice per 20 samples in a
preparation batch)

PCBs

Method blank

One per sample batch

Laboratory control sample

One per sample batch

Duplicate sample

One per sample batch

Labeled compounds

Spiked into every field sample and QC sample

PFAS

Method blank

One per sample batch

Laboratory control sample

One per sample batch

Duplicate sample

One pair per sample batch

Labeled compounds

Spiked into every field and QC sample

Rinsate and Solvent Blank Analyses

The quality control activities associated with the rinsate and solvent blank analyses were generally similar
to those for the tissue analyses, with the following exceptions. First, the rinsate analyses for mercury and
PCBs were prepared and analyzed individually, not in batches of up to 20, in order to provide timely
feedback on the cleanliness of the homogenization equipment. The rinsates for PFAS were held for later
analyses and therefore were grouped together in batches, each with its own associated QC activities.

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Secondly, because the rinsates for PCBs were prepared in solvent, there were no sample extraction
procedures required, so the typical QC procedures relevant to the sample extraction procedure were
modified. The common quality control activities for rinsate samples are described in Table 2.

Table 2. Quality Control Activities for Analysis of Rinsates

Analyte Type

Quality Control Sample

Frequency

Mercury

Instrument blank

With each rinsate sample

Laboratory control sample

With each rinsate sample

PCBs

Instrument blank

With each rinsate sample

Labeled compounds

Added to every rinsate sample

PFAS

Method blank

With each batch of rinsate samples

Laboratory control sample

With each batch of rinsate samples

Labeled compound recovery

Every rinsate sample

Because the mercury rinsates and the PFAS rinsates were prepared in reagent water, there was little
chance of a "matrix effect" and the laboratory control sample, which was also prepared in reagent water,
provided sufficient information on the performance of the method and the laboratory, so a separate matrix
spike sample was not required.

Because the rinsates for PCBs were prepared from hexane and no sample extraction was required, "matrix
effects" were not possible. Therefore, matrix spike and duplicate samples were not required for the
rinsate samples.

GDIT reviewed the results for the mercury and PCB rinsates as soon as they were available from Tetra
Tech and its subcontracted laboratories and relayed the review findings to EPA within hours of receipt of
the results. Mercury was never detected above the laboratory's MDL in any of the rinsate or aqueous
(solvent) blank samples from the study. However, in making its assessments of the rinsate results, GDIT
took a conservative approach and assumed that mercury could be present in the rinsate sample at exactly
the MDL. Based on this assumption, GDIT calculated the total mass of mercury that theoretically might
be transferred to the smallest bulk homogenized tissue sample in the sample batch (due to inadequate
cleaning of the homogenization equipment). That "worst case" estimate was then compared to the MDL
for mercury in tissues and was always at least 6 times lower than the tissue sample MDL. Therefore, in
no instance was there any risk that the mercury reported in the fish tissue samples was the result of
inadequate equipment cleaning, and EPA authorized Tetra Tech to continue processing fish samples.

A similar review approach was utilized for the PCB rinsates and solvent blanks. Because the PCB
rinsates and blanks were analyzed using the very sensitive procedures in EPA Method 1668C (USEPA
2010a), each of the 10 of the PCB congeners of interest was detected sporadically among the 15 pairs of
rinsates and solvent blanks. The amounts reported in the rinsates and solvent blanks generally were
hundreds to thousands of times below the concentration that might be detected in a tissue sample.

The PFAS rinsate and solvent blank samples were analyzed after the end of the preparation of all of the
fish samples and thus were not used to determine if Tetra Tech could proceed with preparing additional
batches of fish. The only PFAS detected in any of the rinsates and solvent blanks was 6:2 FTS, which
was reported in 1 of the 15 of the solvent blanks, but not in the associated rinsate sample. Therefore, in
no instance was there any risk that the PFAS results reported in the fish tissue samples were the result of
inadequate equipment cleaning.

Overall, the rinsate results demonstrate that the equipment cleaning procedures employed for the study
were more than adequate to ensure that cross contamination between tissue samples was not occurring
during processing.

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Chapter 4
Data Quality Assessment

Section 4.1 Data Review

All the data from the study were subjected to two levels of review. First, all laboratory results and
calculations were reviewed by the respective laboratory manager for that analysis prior to submission.
Any errors identified during this peer review were returned to the analyst for correction prior to
submission of the data package. Following correction of the errors, the laboratory manager verified that
the final package was complete and compliant with the contract, and then signed each data submission to
certify that the package was reviewed and determined to be in compliance with the terms and conditions
of the GDIT subcontract.

For the second level of review, GDIT data reviewers examined the results for each field-based tissue
sample and the available quality control data to assess and document the quality of the data relative to the
objectives of the study. Each data package was thoroughly reviewed by GDIT to ensure the following:

•	All samples were analyzed, and results were provided for each sample analyzed, including results for
any dilutions and re-analyses, and for all associated QC samples.

•	All required QC samples were analyzed, and these QC samples met specified acceptance criteria.

•	Data reporting forms and/or electronically formatted data were provided for each of the field-based
tissue samples and/or associated QC analyses.

•	Raw data associated with each field-based tissue sample and QC sample were provided with each
data package, and the instrument output (peak height, area, or other signal intensity) was traceable
from the raw data to the final result reported.

•	Any problems encountered and corrective actions taken were clearly documented.

When anomalies were identified, GDIT contacted the laboratory and asked them to provide the missing
data, clarifications, and/or explanations so that a comprehensive data review could be performed to verify
the quality of their results.

GDIT developed a database to capture results for each sample and entered results of the data reviews
directly in the database through the application of standardized data qualifier flags and descriptive
comments concerning the reliability of the flagged results. Table 3 contains the individual data qualifiers
that were applied to results from the study and provides an explanation of the implications of each
qualifier for the use of the data.

Note: The presence of data qualifiers is not intended to suggest that data are not useable; rather, the
qualifiers are intended to caution the user about an aspect of the data that does not meet the
acceptance criteria established in the project QAPP.

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Table 3. Individual SCC Codes Applied to the 2018-19 NRSA Results

SCC Code

Comments

Implication

B, RMAX

Blank

Contamination,
Result is a
Maximum Value

Blank contamination was observed, and the target analyte was reported in
the sample at a concentration between 5 and 10 times higher than the
blank value. The result was considered to be of acceptable quality, but
data users are cautioned that it may be a maximum value due to possible
influence of contamination.

B, RNAF

Blank

Contamination,
Result is Not
Affected

Blank contamination was present but was not considered to adversely
impact the sample result. The presence of the analyte in the blank is not
considered to adversely affect the data in cases where the sample results
are more than 10 times the associated blank results or where the analyte is
not detected in associated samples.

B, RNON

Blank

Contamination,
Result Reported
as Non-detect

When the sample result is less than five times the blank result, there are no
means by which to ascertain whether or not the presence of the analyte
may be attributed to contamination. Therefore, the result is reported in the
database as a non-detect at the MDL, adjusted for sample size and
dilution.

HLBL, J

High Labeled
Compound
Recovery,
Estimated

The labeled analog of the target analyte was recovered above acceptance
criteria, suggesting the possible presence of matrix interferences. Isolated
instances of high recovery are not uncommon, and patterns across multiple
samples are more of a concern.

HLBL, RNAF

High Labeled
Compound
Recovery, Result
is Not Affected

The labeled analog of the target analyte was recovered above acceptance
criteria, suggesting the possible presence of matrix interferences. Isolated
instances of high recovery are not uncommon, and patterns across multiple
samples are more of a concern. If the analyte was not detected in a field
sample, there is no concern and the RNAF is added to the HLBL flag.

HLCS

High Lab Control
Sample Recovery

The lab control sample (LCS) was a clean reference matrix. If recovery in
the LCS was high, there may be a high bias for that analyte.

HLCS, RNAF

High Lab Control
Sample Recovery,
Result is Not
Affected

The recovery in the LCS was high, but the analyte was not detected in the
associated tissue sample, so there was no high bias concern and the RNAF
flag was applied.

HRPD, J

High RPD,
Estimated

The relative percent difference (RPD) between the results in the parent
sample and the laboratory duplicate is above the acceptance limit. This
may be due to inhomogeneity in the bulk sample or analytical variability.
When high RPD was observed for an analyte, all the detected results for
that analyte in any of the samples in the batch with the duplicate sample
were qualified as estimated values.

HRPD, RNAF

High RPD, Result
is Not Affected

The relative percent difference (RPD) between the results in the parent
sample and the laboratory duplicate is above the acceptance limit. This
may be due to inhomogeneity in the bulk sample or analytical variability.
However, when high RPD was observed for an analyte, the non-detected
results for that analyte were not affected, and the RNAF flag was applied.

HVER, J

High CALVER,
Estimated

The results for the calibration verification associated with the analyte were
above the acceptance limit, suggesting a possible high bias. Detected
analytes also are considered estimated values.

J

Estimated

When applied alone, this code indicates that the result is at or above the
MDL, but below the QL. This flag also may be applied in conjunction
with other flags to indicate the potential for greater uncertainty.

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Table 3. Individual SCC Codes Applied to the 2018-19 NRSA Results

SCC Code

Comments

Implication

LLBL

Low Labeled

Compound

Recovery

The labeled analog of the target analyte was recovered below acceptance
criteria, suggesting the possible presence of matrix interferences or
incomplete recovery of both the labeled compound and target analyte
during the extract cleanup processes used in the analytical procedure. The
use of isotope dilution quantitation automatically corrects the results for
the target analyte. (Non-detects)

LLBL, J

Low Labeled
Compound
Recovery, Result
is an Estimate

LLCS

Low LCS result

The lab control sample (LCS) was a clean reference matrix. If recovery in
the LCS was low, there may be a low bias for that analyte. When low LCS
recovery was observed for an analyte, the results for that analyte were
qualified in all of the samples in the batch with the LCS.

LMI, J

Lock-Mass
Interference,
Result Estimated

There was an interference with the lock ion mass. The detected result is
considered an estimated value.

LMI, RNAF

Lock-Mass
Interference,
Result Not
Affected

There was an interference with the lock ion mass. The associated target
compound was not detected; therefore, the result is not affected.

LND, NQ

Labeled
compound Not
Detected, Not
Quantitated

The labeled compound associated with the target compound was not
detected; therefore, the target compound could not be quantitated.

NDP, RNON

No definitive peak
shoulder for co-
eluter, Result
Reported as Non-
detect

The coeluting peak did not have a definitive peak shoulder. The result was
reported as a non-detect.

RRT, J

RRT outside of

window,

Estimated

Relative retention time is outside the acceptable range, the result is
considered an estimated value.

RTI, RMAX

Retention Time
Interference,
Result is a
Maximum Value

There was an interference within the target compound retention time. The
result is considered a maximum value.

Section 4.2 Analysis of Blanks

Blanks are used to verify the absence of contamination that may occur at any point in the measurement
process. The data reviewers evaluated each sample result in comparison to the result for that analyte in
the method blank prepared in the same extraction batch. For those analytes reported as present in the
method blank, the data reviewers applied the 5x and lOx rules (described in the first three SCC codes of
Table 3) to determine the potential impact of the blank contamination on the study results. The impacts
of blank contamination are discussed separately for each analyte class in Sections 4.2.1 to 4.2.3.

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4.2.1 Blanks for Mercury Analysis

Mercury was never detected above the QC acceptance limit of 0.4 nanograms (ng) in any of the three
method blanks associated with each batch of samples. Therefore, no method blank qualifiers were
applied to the mercury results for the study.

4.2.2 Blanks for PCB Analysis

As shown in Figure 3, more than 99% of the PCB
results were not affected by blank contamination,
either because the analyte was not detected in the
blank (93.93%) or because the concentration in the
sample was more than 10 times the level observed
in the blank (4.81%). For 0.35% of the results, the
data reviewers judged that the sample result is
likely a maximum value (RMAX) because there is
some chance that the sample result was inflated by
the background contamination from the laboratory
that is evident in the blank. Only 0.91% of the PCB
results were changed to non-detects (RNON) due
to concerns about blank contamination.

4.2.3 Blanks for PFAS Analysis

Overall, there were few data quality issues with the blanks from the PFAS analyses. As shown in Figure 4,
more than 99% of the PFAS results were not affected by blank contamination, either because the analyte
was not detected in the blank (99.33%) or because the concentration in the sample was more than 10 times
the level observed in the blank (0.15%). For 0.05% of the results, the data reviewers judged that the sample
result is likely a maximum value (RMAX) because there is some chance that the sample result was inflated
by the background contamination from the laboratory that is evident in the blank. The remaining 0.47% of
the PFAS results were changed to non-detects (RNON) because of concerns about blank contamination.
Given that such small percentage of results were affected by blank contamination, a pie chart has not been
included in this section because the tiny sliver of affected results would not be visible.

Section 4.3 Analysis of Laboratory Control Samples

A laboratory control sample (LCS) is a mass or volume of a clean reference matrix into which the
laboratory spikes the analytes of interest. In some EPA methods, LCS is also known as the ongoing
precision and recovery (OPR) sample. The laboratory analyzes the LCS or OPR using the same sample
preparation and analysis techniques that are applied to the field samples and compares the results to
method- or project-specific acceptance criteria to demonstrate that the laboratory can perform the analysis
acceptably in the absence of matrix-specific interferences.

The QAPP for the 2018-19 NRSA study required that each laboratory performing analyses of fish tissue
samples prepared and analyzed one LCS for each batch of 20 or less field samples. The impacts of LCS
results are discussed separately for each analyte class in Sections 4.3.1 to 4.3.3.

4.3.1 Mercury L CS Results

The LCS results associated with each batch of samples analyzed for mercury met the QC acceptance
limit. Therefore, no LCS qualifiers were applied to the mercury results for the study.

4.81%

0.35% 0.91%

• No Blank Qualifier

• Results Not
Affected

¦ Results Considered
a Maximum Value

¦ Results Changed to
Non-Detect

Figure 3. Impacts of Blank Contamination on the
PCB Results

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4.3.2 PCB LCS Results

The LCS results associated with each batch of samples analyzed for PCBs met the QC acceptance limit.
Therefore, no LCS qualifiers were applied to the PCB results for the study.

4.3.3 PFAS LCS Results

There were a few data quality issues with the LCS
results for the PFAS analyses. However, as shown
in Figure 5, 96.31% of the PFAS results not
affected by LCS issues. Another 1.96% were
qualified due to high LCS results; however, the
compounds were not detected in the associated
samples and therefore those results were not
affected. A total of 1.72% of the PFAS results were
qualified because of a low LCS result that might
reflect a low bias in the results, while 0.10% of the
results were qualified due to a high LCS result that
might reflect a high bias in the results.

Section 4.4 Analysis of Matrix Spike and Laboratory Duplicate Samples

A matrix spike sample (MS) is a mass or volume of a field sample into which the laboratory spikes the
analytes of interest. The laboratory analyzes the MS using the same sample preparation and analysis
techniques that are applied to the field samples and compares the results to method- or project-specific
acceptance criteria to provide information on the effects of the sample matrix on method performance.

A laboratory duplicate sample is a second aliquot of one field sample that is prepared and analyzed to
provide information on the precision of the analytical method. Laboratory duplicate samples are routinely
used for analytes such as metals that are expected to be found in most or all samples. However, other
types of analytes, particularly organic contaminants, are not detected as frequently in field samples, and
the analysis of an unspiked duplicate sample often will not yield useful data on analytical precision when
both the original sample and the duplicate are reported as "not detected." Therefore, EPA methods for
organic contaminants often require that a second spiked aliquot of the sample matrix be prepared as a
matrix spike duplicate (MSD). By spiking the analytes into both, the MS and MSD aliquots, there is a
greater chance of generating useful data on method and laboratory precision.

Alternatively, some EPA methods, such as the one used for the PCBs, and the procedure used for the
PFAS, call for spiking labeled compounds into every sample and the results for those labeled compounds
provide sample-specific data on method performance, as opposed to the batch-specific data generated
from one MS/MSD pair per batch. For these methods, only a laboratory duplicate sample per batch is
analyzed. A duplicate sample is a second aliquot of a field sample that is prepared and analyzed to
provide information on the precision of the analytical method by comparing the results of the original
analysis of the sample and the analysis of the laboratory duplicate sample.

The analytical QAPP for the study (USEPA 2019a) required that the laboratories performing analyses of
fish tissue samples prepare and analyze MS/MSD or duplicate samples with each batch of field samples
as follows.

1.96%

0.10% 1.72%

' No Qualifier

¦ High Laboratory
Control Sample,
Result Not Affected

High Laboratory
Control Sample,
Result Biased High
Low Laboratory
Control Sample,
Result Biased Low

Figure 4. Impacts of LCS Recoveries on the PFAS
Results

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Table 4. Matrix Spike and Duplicate Sample Requirements by Analysis Type

Analysis Type

MS/MSD

Duplicate

Mercury

PCBs

PFAS

The data reviewers evaluated the results for each MS/MSD and laboratory duplicate sample. The impacts
are discussed separately for each analyte class in Sections 4.4.1 to 4.4.3.

4.4.1 Mercury Matrix Spike and Matrix Spike Duplicate Sample Results

The matrix spike and matrix spike duplicate sample results associated with each batch of samples
analyzed for mercury met the QC acceptance limit. Therefore, no data qualifiers for recovery or
precision were applied to the mercury results for the study.

4.4.2 PCB Duplicate Sample Results

The laboratory duplicate sample results associated with each batch of samples analyzed for PCBs met the
QC acceptance limit. Therefore, no duplicate sample qualifiers were applied to the PCB results for the
study.

4.4.3 PFAS Duplicate Sample Results

As shown in Figure 6, the PFAS laboratory duplicate analyses exhibited excellent precision, with 99.78%
of the PFAS results not affected by duplicate issues, with 0.33% of those results where the associated target
compound was not detected. Only 0.22% of results were qualified due to high RPD values, with the results
considered estimates.

Section 4.5 Labeled Compounds

The methods for PCBs and PFAS use analogs of the target analytes that contain a stable (nonradioactive)
isotope of one or more of the atoms that make up the contaminant. These compounds are referred to as
"labeled compounds" and often incorporate multiple atoms of naturally occurring, but less common
isotopes such as 13C, 180, or 37C1. For example, because 13C makes up 1.1% of the carbon in nature, some
PCBs in the environment may contain a single occurrence of 13C among the 12 carbon atoms that make
up the basic PCB structure. However, if the labeled compound is synthesized with all 12 atoms of the
more common isotope 12C replaced by 13C, there is virtually no chance that the 13Ci2-labeled compound
will be present in an environmental sample. Therefore, the labeled compound is ideally suited for use as a
quantitation reference standard during the analysis of PCBs.

The labeled compounds in such methods serve two functions. First, their responses can be used to
quantify the responses for the unlabeled target analytes in each sample through the technique known as
isotope dilution. Secondly, the measured recovery of each labeled compound provides information about
the overall extraction and analysis process applied to each sample. Other labeled compounds are often
added to each sample extract before any cleanup steps to provide information on the performance of those
cleanups as well.

The PCB laboratory added known amounts of 32 13C-labeled PCBs to each sample before extraction. The
PFAS laboratory added known amounts of 18 13C-labeled PFAS and six deuterium-labeled PFAS
standards to each sample before extraction. The QAPP for the study includes acceptance criteria for the

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recoveries of the various labeled compounds. The impacts of the labeled compound results are discussed
separately for each analyte class in Sections 4.5.1 and 4.5.2.

No labeled compounds were employed for the mercury analyses.

4.5.1 PCB Labeled Compound Recoveries

Virtually all (99.61%) of the labeled compound recoveries for the PCB samples met the QC acceptance
limits. Of the 0.39% of the results that were affected by low labeled compound recoveries, 0.13% did not
have the associated target compounds detected and therefore were technically not affected, while 0.22%
of the results were detected and were considered estimates. There were also 17 instances (0.037%) in
which the labeled compounds were not detected due to matrix interferences; therefore, the target
congeners associated with these labeled compounds could not be quantified. A pie chart has not been
included in this section because the tiny sliver of affected results would not be visible.

4.5.2 PFAS Labeled Compound Recoveries

Overall, 96% of the labeled compound recoveries
for the PFAS samples met the QC acceptance
limits. As shown in Figure 7, 1.89% of the results
were affected by high labeled compound
recoveries. Of those, 1.86% did not have the target
analytes associated with those labeled compounds
detected in the samples and therefore, the results
were not affected, while 0.031% of the results had
the associated target compounds detected and
those results were considered estimated values.

Approximately 2.08% of the results were affected
by low labeled compound recoveries. Of those,

0.91% did not have the target analytes associated
with those labeled compounds detected in the
samples and therefore the results were not affected,
while 1.17% of the results had the associated target compound detected and those results were considered
estimated values. A total of 0.031% of the results (17 instances) had an issue where the labeled compound
was not detected; therefore, the associated target compounds could not be quantified.

Section 4.6 Ion Abundance Ratios

The instruments used for PCBs and PFAS analyses monitor the signals from two ions produced for each
analyte. The resolution of the mass spectrometer is sufficient to distinguish ions that differ in mass by a
few ten-thousandths of an atomic mass unit. The ratio of the abundances of these two ions is used as one
of four criteria to identify the analyte. The methods include QC acceptance criteria for the ion abundance
ratio (IAR) for each target analyte that are based on the theoretical occurrence of each of the component
atoms in nature, plus and minus some percentage (e.g., ± 15%).

In some cases, the observed IAR may fall outside of the consensus-based acceptance limit. That does not
mean that the analyte is not present, but it suggests that there may be some contribution to the response
from an ion with a very similar mass produced by an interference. A higher-than-expected IAR suggests
an interference with the ion in the pair for the target analyte with the smaller mass, while a lower-than-
expected IAR suggests an interference with the ion in the pair for the target analyte with the larger mass.

0.03% 0.91%
1.86% \ /

• No Qualifier

¦ High Labeled Compound
Recovery, Result Not
Affected

j High Labeled Compound
Recovery, Result
Estimated

Low Labeled Compound,
Result Not Affected

• Low Labeled Compound,
Result Estimated

¦ Labeled Compound Not
Detected

Figure 5. Impacts of Labeled Compound
Recovery on the PFAS Results

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When the exceedance from the acceptance limit is small (e.g., a few percent), the method for PCB allows
the analyst to report the results in such instances with a qualifier flag that alerts the data user to the
situation.

During the data review process, any results reported with an IAR issue are reviewed in more depth. If all
other identification criteria in the method are met, the results are reported for the analyte with the
appropriate qualifier flag. The impacts of the IAR are discussed separately for each analyte class in
Sections 4.6.1 and 4.6.2.

4.6.1 PCB Ion Abundance Ratios

Overall, 99.14% of the PCB results were not qualified because of ion abundance ratio concerns. As
shown in Figure 8, higher-than-expected IARs were observed on 0.75% of the results while lower-than-
expected IARs were observed in 0.11% of the results. The slightly higher distribution of high ion ratios
suggests that the interferences being extracted from the fish tissue for the affected samples systematically
influenced the numerical results in one direction more than the other.

4.6.2 PFAS Ion Abundance Ratios

The IARs for sample results associated with each batch of samples analyzed for PFAS met the acceptance
limit. Therefore, no IAR qualifiers were applied to the PFAS results for the study.

Section 4.7 Other QC parameters

As evidenced by the list of individual SCC data qualifier codes in Table 3, the data review effort
identified instances where the calibration verifications for the PCB analyses did not always meet the
acceptance criteria (see Table 3). However, the frequencies were very low, with only 0.026% of the PCB
calibration verification results falling outside of the acceptance criteria. Given these very low
occurrences, a pie chart has not been included in this section because the tiny slivers of affected results
would not be visible.

Section 4.8 Completeness

Completeness is a measure of the amount of data that are collected and deemed to be acceptable for use
the intended purpose. The completeness goal established in the QAPP in this study is to obtain valid
measurements from 95% of the samples analyzed. For multi-analyte methodologies, analytical
completeness is best calculated based on the number of possible sample/analyte combinations. Otherwise,
a problem with a single analyte could be seen as invalidating an entire field sample.

Combining the number of target analytes for the three types of analyses (mercury, PCBs, and PFAS)
yields a total of 193 measured results for each sample (based on 159 results that cover all 209 PCB
congeners). For the 290 field samples analyzed, the total number of sample/analyte combinations would
be 55,970.

Despite the data quality concerns outlined in this report, all the available and intended samples were
successfully analyzed for all the target analytes. Following an intensive review of the project data, none
of the results were excluded from consideration based on data quality concerns. Therefore, analytical
completeness is 100%, and OST met its completeness goal.

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Analysis of Water and Wastes (MCAWW) EPA/600/4-79-020 - Revised March 1983. U.S.

Environmental Protection Agency, Office of Water, Washington, DC.

USEPA. 2001. Appendix to Method 1631 Total Mercury in Tissue, Sludge, Sediment, and Soil by Acid
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USEPA. 2002. Method 1631, Revision E: Mercury in Water by Oxidation, Purge and Trap, and Cold
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USEPA. 2019b. Quality Assurance Project Plan for Sample Analysis for the 2018-19 National Rivers
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USEPA. 2019c. Quality Assurance Project Plan for Sample Analysis for the 2018-19 National Rivers
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