September 2012



# Environmental Technology Verification Report

Pall Corporat ion

Xact 625 Particulate Metals Monitor

Prepared by

Under a cooperativ e agreement with

U.S. Environmental Protection Agency EPA/600/R-12/68 0i EPA/600/R-12/680

September 2012



# Environment al Technology Verification Report

ETV Advanced Monitoring Systems Center

Pall Corporation

Xact 625 Particulate Metals Monitor

By

Thomas Kelly and Amy Dindal , Battelle John McKernan, U.S. EPA

Battell e Columbus, Ohio 43201ii Notice

The U.S . Environmental Protection Agency (EPA), through its Office of Research and Development, has financially supported and collaborated in the extramural program

described here. This document has been peer reviewed by the Agency. Mention of trade

name s or commercial products does not constitute endorsement or recommendation by the

EPA for use.

This r eport was prepared by Battelle to summarize testing supported by EPA ’s Region 5 and Office of Air Quality Planning and Standards (OAQPS), and conducted in collaboration with the Ohio EPA (OEPA). Neither Battelle

, EPA, OEPA nor any person acting on behalf of those organizations

(a) Makes any warranty of representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately-owned rights; or

(b) Ass umes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in this report.

Referen ce herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply i ts endorsement, recommendation, or favoring; nor do the views and opinions of authors expressed herein necessarily state or reflect those of the EPA or OEPA

.iii Foreword

The EPA is charged by Congress with protecting the nation’s air, water, and land resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, the EPA’s Office of Research and Development provides data and science support that can be used to solve environmental problems and to build the scientific knowledge base needed to manage our ecological resources wisely, to understand how pollutants affect our health, and to prevent or

reduce environmental risks.

The Envi ronmental Technology Verification (ETV) Program has been established by the EPA to verify the performance characteristics of innovative environmental technology across all media and to report this objective information to permitters, buyers, and us ers of the technology, thus substantially accelerating the entrance of new environmental technologies into the marketplace. Verification organizations oversee and report verification activities based on testing and quality assurance (QA) protocols develop ed with input from major stakeholders and customer groups associated with the technology area. ETV consists of six environmental technology centers. Information about each of these centers can be found on the Internet at http://www.epa.gov/etv/.

Effect i ve verifications of monitoring technologies are needed to assess environmental quality and to supply cost and performance data to select the most appropriate technology for that

assessment. Under a cooperative agreement, Battelle has received EPA funding to plan, coordinate, and conduct such verification tests for “Advanced Monitoring Systems for Air, Water, and Soil” and report the results to the community at large. Information concerning this specific environmental technology area can be found on the Int ernet at http://www.epa.gov/etv/centers/center1.html.iv Acknowledgments

The authors wish to acknowledge the support of all those who helped plan and conduct the verification test, analyze the data, and prepare this repor t. QA support was provided by Laurel Staley of EPA /ORD ’s National Risk Management Research Laboratory, Rebecca Shircliff of Neptune and Company, Inc., and Zachary Willenberg of Battelle. The efforts of Darren Machuga, Steve Lowry, Dean Ponchak , Mi chael Mu rphy, and William Colon of the

OEPA in conducting the field test are greatly appreciated. Finally, the authors thank Dennis Mikel of EPA’s OAQPS

, Rudy Eden of California’s South Coast Air Quality Management

District , and Emily Snyder of EPA’s Office of Research and Development for their review of this verification report.v 

### Contents

Notice

........................................................................................................................................ ii

Foreword

.................................................................................................................................. iii Acknowledgments .................................................................................................................... iv List of Figures .......................................................................................................................... vi

List of Tables ............................................................................................................................ vi

List of Abbreviations ............................................................................................................... vii

Chapter 1: Background ............................................................................................................. 1

Chapter 2: Technology Description ......................................................................................... 2

Chapter 3: Test Design and Procedures ................................................................................... 4

3.1 Introduction ................................................................................................................... 4

3.2 Test Procedures ............................................................................................................. 5

3.2.1 Field Installation ................................................................................................ 5

3.2.2 R eference Sampling and Analysis ..................................................................... 6

3.2.3 Verification Sites and Schedule ........................................................................ 7

Chapter 4: Quality Assurance/Quality Control ........................................................................ 9

4.1 Amendments/Deviations ............................................................................................... 9

4.2 Reference Methods ........................................................................................................ 9 4.3 Review of Xact 625 QC Data ...................................................................................... 10

4.4 Audits .......................................................................................................................... 10

4.4.1 Technical Systems Audit ................................................................................. 10

4.4.2 Performance Evaluation Audit ........................................................................ 10

4.4.3 Data Quality Audit .......................................................................................... 12

4.5 QA/QC Reporting ........................................................................................................ 12

4.6 Data Review ................................................................................................................ 12

Chapter 5: Statistical Methods ............................................................................................... 13

5.1 Averaging of Xact 625 Hourly Data ........................................................................... 13

5.2 Comparability .............................................................................................................. 15

5.3 Correlation ................................................................................................................... 15

5.4 Bias .............................................................................................................................. 15

5.5 Data Completeness ...................................................................................................... 15

Chapter 6: Test Results ........................................................................................................... 17

6.1 Xact 625 Ambient Metals Results ............................................................................... 17

6.2 Comparability and Correlation .................................................................................... 23

6.3 Bias .............................................................................................................................. 25

6.4 Data Completeness ...................................................................................................... 26

6.5 Operational Factors ..................................................................................................... 27

Chapter 7: Performance Summary ......................................................................................... 29vi Chapter 8: References ............................................................................................................ 31



### List of Figures

Figure 2 -1. Xact 625 Installed in Field Trailer for Testing ..................................................... 3 Figure 3 -1. Field trailer used in verification test, showing Xact 625 PM 10 inlet,

reference PM 10 automated sampler, and meteorol ogical sensors on the

roof ....................................................................................................................... 6 Figure 3 -2. Map view of Marietta, Ohio area showing location of OVESC sampling site (white triangle near top of figure) and of suspected metals emission source (red triangle at left center of figure) .......................................................... 8 Figure 6 -1. Xact 625 hourly monitoring data for Mn, K, Fe, and Zn in Marietta, OH from December 10, 2011 to February 27, 2012 ................................................. 18 Figure 6 -2. Example of elevated metals concentrations over a period of several

hours ................................................................................................................... 18 Figure 6 -3. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Ca ................................................................................................... 20 Figure 6 -4. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Cu ................................................................................................... 21 Figure 6 -5. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Mn .................................................................................................. 21 Figure 6 -6. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Pb ................................................................................................... 22 Figure 6 -7. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Se ................................................................................................... 22 Figure 6 -8. Linear regression of Xact 625 daily averages against ICP/MS daily averages for Zn ................................................................................................... 23 Figure 6 -9. Percent bias results for Pb as a function of the reference concentration ............ 26



### List of Tables

Table 4 -1. Summary of PE Audits of Reference Analytical Method .................................. 11

Table 5 -1. Calculation of the Xact 625 Daily QL for Elements Reported in Ambient Air at the Marietta Site and Comparison to ICP/MS Detection

Limits .................................................................................................................. 14

Table 6 -1. Summary of Hourly Values of All Metals Reported by the Xact 625 in Marietta, Ohio from December 10, 2011 to February 27, 2012 ......................... 19

Table 6 -2. Results of Linear Regression of Xact 625 and Reference Data ......................... 24

Table 6 -3. Bias of Xact 625 Results Relative to Reference Results .................................... 25

Table 6 -4. Data Completeness for the Xact 625 .................................................................. 27

Table 7 -1. Quantitative Performance Results for the Xact 625 ........................................... 29vii 

### List of Abbreviations

AMS Adva nced Monitoring Systems

As arsenic

Ba barium

°C degrees Centigrade

Ca calcium

Cd cadmium

CES Cooper Environmental Services LLC

CI confidence interval

Co cobalt

Cr chromium

Cu copper DC data completeness

EDXRF energy -dispersive X- ray fluorescence

EPA U.S. Environmental Protection Agency

ETV Environmental Technology V erification

Fe iron

HF hydrofluoric acid Hg mercury ICP /MS inductively coupled plasma mass spectrometry K potassium

L/min liter per minute

mm Hg millimeter of mercury

m 3 /hr cubic meter per hour

MDL method detection limit μg/L microgram per liter

μm micrometer

Mn manganese Mo molybdenum ng/m 3 nanograms per cubic meter

Ni nickel

NIST National Institute of Science and Technology OAQPS Office of Air Quality Planning and Standards

OEPA Ohio Environmental Protection Agency

OVESC Ohio Valley Educat ional Service Center

Pb lead

Pd palladium

PE performance evaluation

PM particulate matter

PM 10 particulate matter of aerodynamic diameter ≤ 10 micrometers QA quality assurance QAPP quality assurance project plan QC quality control QL quantitation limitviii QMP quality management plan

r 2 coefficient of determination

Rb rubidium

RSD relative standard deviation

SAT School Air Toxics

Sb antimony

SD standard deviation

Se selenium

SEDO Southeast District Office

Sr

strontium

Th thorium

Tl thallium

TSA technical systems audit

XRF X- ray fluorescence

Zn zinc1 

### Chapter 1 Background

The U.S. Envi ronmental Protection Agency (EPA) supports the Environmental Technology Verification (ETV) Program to facilitate the deployment of innovative environmental technologies through performance verification and dissemination of information. The go al of the ETV Program is to further environmental protection by accelerating the acceptance and use of improved and cost- effective technologies. ETV seeks to achieve this goal by providing high- quality, peer -reviewed data on technology performance to those involved in the design, distribution, financing, permitting, purchase, and use of environmental technologies.

ETV w orks in partnership with recognized testing organizations; with stakeholder groups consisting of buyers, vendor organizations, and permitt ers; and with the full participation of individual technology developers. The program evaluates the performance of innovative technologies by developing test plans that are responsive to the needs of stakeholders, conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing peer

- reviewed reports. All evaluations are conducted in accordance with rigorous quality assurance and quality control (QA/QC ) protocols to ensure that data of known and adequate quality are generated and that the results are defensible.

The EPA’s National Risk Management Research Laboratory and its verification organization partner, Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center recently evaluated the pe rformance of the Xact 625 Particulate Metals Monitor produced by Pall Corporation at an ambient air quality monitoring site in Marietta, Ohio

. S ystems for monitoring of metals in atmospheric particulate matter (PM) were identified as a priority technology category for verification through the AMS Center stakeholder process.2 

### Chapter 2 Technology Description

The object ive of the ETV AMS Center is to verify the performance characteristics of environmental monitoring technologies for air, water, and soil. This report provides results

f rom verification testing of the Xact 625 Particulate Metals Monitor , which was developed and previously manufactured by Cooper Environmental Services LLC (CES) (Portland, OR). Commercial rights to the Xact 625 technology are now owned by Pall Corporation (Port Washington, NY). The following is a description of the Xact 625 , based on information provided by the vendor. The information provided below was not verified in this test.

The X act 625 , shown in Figure 2-1, determines metals in airborne PM less than 10 micrometers (μm) in aerodynamic diameter (PM 10 ). Metals deter mination by the Xact 625 is based on the principle of X-ray fluorescence (XRF), in which X- rays from a source cause removal of an electron from an inner electronic shell of a metal atom in a sample. The vacancy in the inner shell is then filled by an elec tron from an outer shell, with resulting

emission of an X- ray with a wavelength longer than that of the original excitation and characteristic of the metal in question. The Xact 625 uses energy

- dispersive XRF (EDXRF),

in which the detector and electronics resolve emitted X -rays based on their energy. The EDXRF approach allows use of a relatively simple optical path and a relatively low power X-ray source, and thus reduces the instrument cost. The EDXRF approach also provides acquisition of the entire X-ray spectrum very rapidly, so that many elements in the periodic

table can be detected within a few seconds.

To monito r metals in atmospheric PM, the Xact 625 uses an automated moveable filter tape system, in which sample air is drawn through a small spo t on the tape, collecting and concentrating PM 10 onto that spot. T he tape then advances, placing the collected sample spot in the X-ray excitation and analysis section of the instrument and initiating sampling onto a previously unexposed spot on the tape. The sequence of sampling and analysis can continue automatically, limited only by the supply of filter tape. The duration of sample collection at each spot can be set at a constant interval, or varied to maintain detection performance in the face of varying atmospheric PM 10 levels. The Xact 625 samples ambient air at a constant

fl ow rate of 16.7 liter s per minute ( L/min ), i.e., 1 cubic meter per hour (m 3 /hr). The Xact

625 ’s sample inlet is designed to provide uniform sample deposition, and the instrument analyze s approximately 90% of the sample spot area to minimize effects of sample inhomogeneity. The Xact 625 incorporates sensors for temperature and atmospheric pressure, and uses those data to maintain a constant volumetric sample flow and3 consequently an accurate PM 10 inlet size cut. In addition for this verification the vendor of

the Xact 625 programmed the monitor to perform the following automatic internal QC checks on a daily basis to assure data quality :

• Internal energy alignment check, performed by XRF analysis of a copper (Cu) rod

, conducted over a 15-minute period starting at midnight each day

,

• Upscale rod check, performed by XRF analysis of a metal rod containing chromium (Cr) , lead (Pb) , and cadmium (Cd) , conducted once per day over a 15-minute period,

• Flow check, conducted at the same time as the upscale rod chec k, to determine the Xact 625 sample air flow by insertion of a second mass flow meter into the flow path,

• Palladium (Pd) rod stability check, conducted by XRF analysis of a Pd rod in every ambient sample analysis

.

Figure 2-1. Xact 625 installed in field trailer for testing; top to bottom are the control panel/X -ray source, computer, XRF analysis

module with sampling tape drive

, modem , and datalogg er

.4 

### Chapter 3 Test Design and Procedures

3.1 Introdu ction

I ndus trial communities are often impacted by emissions of toxic metals such as Pb

, manganese (Mn) , and Cd. For example, EPA’s S chool A ir T oxics (SAT) Monitoring

Initiative 1 has reported that Mn, a neurotoxic metal, is one of the pollutants of greatest potential risk near schools in industrialized locations. Standard monitoring methods for metals in airborne PM have significant limitations , in that samples are collected on filters

over a 24-hour time period and must be submitted for laboratory analy sis, from which results may not be available for several weeks. In contrast, c ommercially

- developed metals

monitors can potentially determine 10 or more toxic metals simultaneously in ambient PM 10 with time resolution of 1 hour or less. The relatively fast response afforded by such monitors

can provide advantages such as :

• Improv ed ability to associate variations in metals concentrations with time of day or meteorological conditions, and thus to attribute metals risk to a particular source

• Ability to compile dataset s large enough to conduct source/receptor modeling, and

• Cost reduction and time savings due to the generation of metals data onsite without waiting for laboratory analysis. Thus, continuous metals monitoring may lead to better characterization of environmental

metals exposures and more effective source identification, allowing decision

- makers to quickly target industries for enforcement action or voluntary emissions reduction.

This ve rification test was conducted according to a peer

- reviewed quality assurance project plan (QAPP)

, 2 and conformed to the quality system defined in the ETV 3 and AMS Center 4
Quality Management Plans (QMPs). As indicated in the QAPP 2 the testing satisfied EPA QA Category III requirements. The QAPP and this verification report were reviewed by:

• Rudy Eden, South Coast Air Quality Management District

• Dennis Mikel, U.S. EPA Office of Air Quality Planning and Standards ( OAQPS ).

The purpos e of this verification test was to generate performance data on metals monitoring technologies to inform users about the potential benefits of such technologies. The verification results reported here are from test ing that involved the continuous operation of a Xact 625 monitor at an ambient air monitoring site in Marietta, Ohio , operated by the Southeast District Office (SEDO) of the Ohio Environmental Protection Agency ( OEPA)

. The PM 10 metals data produced hourly by the Xact 625 were averaged and compared to
metals data from reference method samples collected daily and analyzed in the laboratory.5 The Xact 625 was verified by evaluating the following performance parameters.

• Comparability

• Correlation

• Bias

• Data completeness

• Operational factors

Compar ability, correlation, and bias were assessed by comparison of Xact 625 results to those from inductively coupled plasma/mass spectrometry (ICP/MS) analysis of samples collected by a reference sampling method . D ata completeness was determined from the number of hourly periods the metals monitor provided readings of PM 10 metals concentrations. Data completeness was determined both relative to the entire field test period

and relative to each 24-hou r reference sampling period. Each of these performance factors

w as evaluated separately for those target metals detect ed by both the Xact 625 and the

reference sampling/ICP

- MS approach . O perational performance factors such as maintenance requirements , ease of use, and effectiveness of data acquisition were determined from observations by the field testing staff. This test wa s not intended to simulate long- term performance of the metals monitor at a monitoring site , but rather to assess the feasibility of its use for ambient metals monitoring in near -source locations. In long- term use, metals monitoring procedures might be tailored to address the specific conditions, metals concentrations, and sourc es for a given site.

3.2 Test Procedures

3.2.1 Fiel d Installation The Xact 625 used in this testing was purchas ed in 2011 by EPA’s OAQPS as a stand- alone monitoring system, designed and built by CES per EPA specifications. The Xact 625

monitor was installed in an environmentally controlled trailer specially designed for field deployment of the monitor. Figure 3-1 sh ows an external view of the trailer at the Marietta

test site with the Xact PM 10 inlet, reference sampler (see Section 3.2.2) and meteorological sensors located atop the trailer. A view of the Xact 625 installed in the trailer is shown above in Figure 2-1.

The P M 10 inlet of the Xact 625 extended through the roof of the trailer and was positioned approximately 1.5 m (5 ft) from the inlet of the PM 10 reference sampler, as shown in Figure 3-1. A contractor employed by EPA/OAQPS transported and installed th e Xact 625 trailer in the field, and performed startup checks on the Xact 625 monitor. The vendor of the Xact 625 (Pall Corporation) trained OEPA staff in operation of the monitor, and those OEPA staff oversaw operation of the monitor during the field testing. The automated internal QC checks of the Xact 625 were programmed to take place between midnight and 12:30 am each day. As a result, on each test day, the Xact 625 reported 23 one-hour averages and one half-hour average measurement of metals in ambient PM 10 . All Xact 625 measurement data and QC results were recorded by the monitor’s datalogger, downloaded by EPA/OAQPS, and transferred to Battelle for use in data comparisons.6 Figure 3- 1. Field trailer used in verification test, showing Xact 625 PM 10 inlet,

reference PM 10 automated sampler , and meteorological sensors on the roof.

3.2.2 Refere nce Sampling and Analysis

A mbient PM 10 samples for reference metals analysis were collected according to EPA

Method IO -3.1 5 using a Partisol Plus 2025 Sequential Ambient Particulate Sampler (Thermo Scientific, Hopkinton, MA) equipped with a PM 10 size

- selective inlet. This sampler is designated by EPA as Reference Method RFPS -1298-127 for sampling of ambient PM 10

. The Partisol Plus 2025 us es 47 mm diameter Teflon ® sample filters which are exchanged automatically after a pre- set sampling interval . The Partisol Plus 2025 can hold up to 16 filter cassettes, sufficient for more than two weeks of unattended daily sampling. Sample air is pulled by an internal pump through the filter currently being sampled, with the sample air flow regulated by a mass flow controller

. Ambient temperature and pressure readings are used along with mass flow control to maintain a constant volumetric sampling rate of 16.7

L/min . Previously sampled and yet- to

- be

- sampled filters are sealed off within the Partisol Plus 2025 to prevent contamination

. The sampler stores sampling and meteorological data in internal memory, including the average ambient temperature, ambient pressure, and average ambient relative humidity for each filter sample

.

The Par tisol Plus 2025 sampler was installed on the roof of the field trailer as shown in Figure 3-1 and was operated by OEPA personnel. Samples were collected every day Partisol Plus 2025 Reference Sampler Xact 625 PM 10 Inlet Meteorological

Sensors7 throughout the field period with a 23.5 hour sampling duration, chosen so that reference sampling did not take place during the 0.5 hours per day when the Xact 625 perform ed its

internal QC checks. Thus , the reference and Xact 625 sampling intervals we re identical throughout the test period.

The ICP/MS laboratory contracted by EPA/OAQPS delivered blank 47 mm Teflon ® filters to the field site in individual pre

- labeled containers accomp anied by chain of custody forms. Collected filter samples were removed from the Partisol Plus 2025 sampler approximately once per week without interruption of sampling. Collected samples were then shipped to the

ICP/MS laboratory for extraction and analysis approximately every 2 weeks

.

The r eference PM 10 filter samples were extracted and analyzed by the ICP/MS laboratory for

metals content according to the procedures of EPA Method IO-3.5, 6 but using a modified acid digestion that included hydrofluoric acid (HF) to improve digestion for some elements.

Th e extraction and analysis w ere performed according to Standard Operating Procedures that are incorporated into the laboratory ’s QAPP for samplin g and analysis in EPA’s national monitoring programs. 7 The QC requirements of Method IO-3.5 6 were followed, including the use of blanks, QC samples, laboratory fortified blanks, internal standards, and tuning solutions. An instrument performance demonstration program included duplicate samples, standards, blanks, interference check standards, continuing calibration blanks and verification standards, and laboratory control and matrix spikes. 7 The ICP/MS laboratory’s stated

detection limits for the PM 10 me tals are summarized in Table 5 -1 in Section 5.1.

3.2.3 Verification Sites and Schedule

The Xact 625 operated from August 19 to November 3, 2011 at an OEPA field site in East Liverpool, Ohio. Battelle conducted a technical systems audit (TSA) of the field procedures and a performance evaluation (PE) audit of the Partisol Plus 2025 reference sampler at the East Liverpool site that confirmed both adherence to the fi eld procedures and valid reference sampler operation. However, during operation at the East Liverpool site

, clearly erroneous

ambient temperature and pressure readings were reported by the Xact 625 sensors . Because of those readings it was determin ed tha t the reliability of the monitor’s sample flow (and consequently its PM 10 particle size cut) was questionable. The temperature and pressure sensors in the Xact 625 were not rep aire d until the end of the sampling period in East Liverpool, and therefore it was concluded that none of the Xact 625 data from the East Liverpool site were of sufficient quality to be used for performance verification. It should be

noted that the failure of th ose sensors was not caused by a fault in the Xact 625 itself, but by the exposed location of the wiring connections for th ose sensors on the roof of the field

trailer in which the Xact 625 was installed. The design of those connections was subsequently corrected by installation of more durable and weather resistant connections.

Follow ing repair of the ambient temperature and pressure sensors in the Xact 625, the field

trailer and Partisol Plus 2025 reference sampler were installed at an OEPA site at the Ohio Valley Educational Service Center (OVESC) in Marietta, Ohio. The Xa ct 625 operated continuously at the Marietta site from December 10, 2011 to February 2 7, 2012, and with minor interruptions daily reference samples were collected with the Partisol Plus 2025 sampler from December 23, 2011 through February 25, 2012. Thus, data for comparison of8 Xact 625 and reference results were obtained over a 65 -day period, within an approximately 80-day period of continuous operation of the Xact 625. The daily reference method samples

were collected over 23.5-hour sampling intervals, i.e., from 12:30 am to midnight each day. This sampling schedule synchronized the reference and Xact 625 sampling periods and avoided reference sampling during the half hour each day when the Xact 625 performed its internal QC checks. Throughout the peri od in which the Xact 625 was operating at the Marietta site, t he monitor’s automated QC check results were reviewed frequently and

confirm ed proper operation of th e instrument.

Both th e East Liverpool and Marietta air quality monitoring sites were locate d in industrialized areas near the Ohio River characterized by restricted air flow due to local terrain. Both sites were chosen in part based on elevated levels of Mn and other metals found in ambient total suspended particulate in EPA’s SAT Monitoring In itiative. Figure 3 -2 shows a map view of the Marietta area, indicating the location of the OVESC sampling site

and of an industrial facility thought to be a key source of metals emissions in the area.

Figure 3

- 2. Map view of Marietta, Ohio area showing location of OVESC sampling site (white triangle near top of figure) and of suspected metals emission source (red triangle at left center of figure)

. OVESC9 

### Chapter 4 Quality Assurance/Quality Control

QA/QC procedures and all verification testing were performed in accordance with the QAPP

for this verification test and the QMP for the AMS Center except where noted below. QA/QC procedures and results are described below.

4.1 Amendments/ Deviations

T hree d eviations to the test/QA plan were prepared , approved , and retained in the test

documentation . Th o se deviations collectively established the following modifications and corrections to the test/QA plan and the test procedures:

• The period of testing at the East Liverpool site was shortened due to startup difficulties with the Partisol Plus 2025 sampler

.

• At the request of the analytical laboratory, reference filter samples were shipped from

the field site to the analytical laboratory every 2 weeks, rather than every week as stated in the QAPP , to provide more efficient handling and analysis of each batch of samples.

• Testing was conducted at one site ( Marietta) rather than two sites as originally planned, due to the failure of the Xact 625’s ambient temperature and pressure sensors at the East Liverpool site, as noted in Section 3.2.3.

• The filters used in the Partisol Plus 2025 sampler were not weighed before shipment

to the field because determination of PM 10 mass concentration was not needed.

• The analytical laboratory returned ICP/MS analysis results withi n 7 days of the end of the week in which samples were received, rather than within 7 days of sampl e receipt.

• The sample extraction procedure used by the analytical laboratory was modified slightly from the procedure in Method IO-3.5, by the inclusion of HF in the digestion reagent. This fact was specified in the laboratory’s standard operating procedure but

was not stated in the QAPP.

These deviations are not considered to have had any significant effects on the verification

data obtained at the Marietta site.

4.2 Reference Methods

The Q A/QC procedures for the reference metals sampling and ICP/MS analysis adhered to the requirements of the methods used. 5-7 The QC results were reported to EPA/OAQPS by the analytical laboratory as part of the analytical data package for the reference samples.10 4.3 Review of Xact 625 QC Data

The res ults of the automated daily internal QC checks performed by the Xact 625 were

reviewed approximately weekly, each time data were downloaded from the instrument.

Th os e results showed stability in Xact 625 operations throughout the entire period of operation at both the East Liverpool and Marietta sites. Over that entire period the relative

standard deviation (R SD) of the Pd internal standard readings determined in every Xact 625 XRF analysis was 2.04%. The instrument’s average flow error was -0.69% (± 0.004%), where the value in parentheses is the standard deviation (SD) of the daily flow check results.

T he av erage accuracy relative to upscale rod check standards analyzed daily was 100.21% (±0.004%) for Cr , 100.55% (±0.013%) for Cd, and 99.79% (±0.007%) for Pb , where accuracy of 100% represents perfect agreement with the upscale rod check standard

.

4.4 Audits

Three t ypes of audits were performed during the verification test: a TSA of the verification test performance, a PE audit of the reference method sampling and analysis

, and a data quality audit. Audit procedures are described further below.

4.4.1 Technical Systems Audit

The Battelle QA Officer performed two TSA s as part of this verification test. The field TSA was performed at the East Liverpool test site on October 6, 2011, and focused on observation of the sampling material handling, Xact 625 oversight, reference method sampling, and field data recording procedures. The first two deviations listed in Section 4.1 were noted in that

TSA. The second Battelle TSA consisted of a visit on February 23, 2012 to the analytical laboratory contracted by EPA/OAQPS to conduct the ICP/MS analyses. That TSA focused on laboratory QA/QC, chain of custody, and analytical procedures. No significant findings

resulted from the laborator y TSA.

An E PA QA representative also conducted a field TSA at the East Liverpool site on October 13, 2011. Two findings from that audit addressed communication among the several organizations involved in the test, and the failures of the temperature and pressure sensors in

the Xact 625 that are described in Section 3.2.3. Those sensor failures were the cause of the third deviation listed in Section 4.1. Both of these findings were addressed prior to the start of testing at the Marietta site, the former by instituting regular conference calls among all parties, and the latter by replacement of the temperature and pressure sensor and confirmation of their correct operation.

4.4.2 Performance Evaluation Audit

A PE audit of the Partisol Plus 2025 reference method sampler w as performed at the East Liverpool site on December 2, 2011, prior to moving the field test to the Marietta site. The

PE flow audit was conducted by measuring the sample air flow rate through the sampl er by

means of a National Institute of Science and Technology ( NIST )- traceable flow transfer

standard (BIOS DryCal, Serial No. 103777). The results of th at PE audit showed that the Partisol 2025 sample flow rate was within 1.9% of the target rate of 16.7 L/min

, well within11 the target ±5% tolerance of the flow rate. The PE audit of the ambient temperature and pressure sensors of the Partisol Plus 2025 sampler was conducted using a Kestrel ® Model 4500 Pocket Weather Tracker (Nielsen -Kellerman, Boothwyn, PA) obtained from Battelle’s Instrumentation Services Laboratory (No. LN -269475). Th e PE audit showed that the Partisol Plus 2025 temperature and pressure sensors agreed with the PE audit device within

0.3 degrees Centigrade ( °C) and 1 millimeter of mercury (mm Hg ) pressure, respectively. These PE audit results were well within the target tolerances of ± 2 °C and ± 4 mm Hg (i.e.,

± 5 .3 millibars) , respectively

.

Battell e also conducted a PE audit of the reference metals analysis by submitting sample

solutions of eight target metals to the reference laboratory for analysis. Th o se PE audit samples were prepared by Battelle by dilution of individual aqueous metals standards

traceable to NIST. The metals concentrations in the PE aud it samples were unknown to the

reference laboratory. Two PE audit samples containing different levels of the eight metals were submitted for analysis, and the reference laboratory analyzed each sample both with and

without dilution. The results from thos e two analyses agreed closely for each target metal in each of the two PE audit samples, so the average of the undiluted and diluted sample results was used for comparison to the spike value for each metal. The acceptance criterion for the

PE audit wa s th at the concentrations reported by the laboratory should be within ±10% of the prepared concentrations. T he results of the laboratory PE audit are summarized in Table 4 -1, and show that the reference analyses met that acceptance criterion for all metals in both PE

audit samples

.

Table 4 -1. Summary of PE Audits of Reference Analytical Method

Sample Metal Standard

Concentration
( μ g/L) a Measured

Concentration
( μ g/L) Percent

Difference

# 1 As 8 .0 8. 2 7 3.4

Cd 2 .0 2. 06 2.8

Cr 8 .0 8. 34 4.2

Mn 2 .0 1.9 7

- 1.3

Ni 2 .0 2.1 4 6. 9

Pb 2 .0 2.06 3.0

Sb 2 .0 1. 86

- 7.0

Se 8 .0 8.77 9.6

# 2 As 30 3 0.3 1.1

Cd 7 .0 7. 3 6 5.1

Cr 30 30.4 1.3

Mn 7 .0 7. 12 1.7

Ni 7 .0 7.3 7 5.3

Pb 7 .0 7. 21 3.0

Sb 7 .0 6. 73

- 3.9

Se 30 3 2.9 9.7

a: μg/ L = microgram per liter12 4.4.3 Data Quality Audit
At least 10% of the data acquired during the verification test were audited. Battelle’s QA

Officer traced the data from the acquisition, through reduction and statistical analysis, to final reporting, to ensure the integrity of the reported results. All calculations performed on the data undergoing the audit were checked. Only minor and readily correctable data issues were noted in the data quality audit, with no effect on the overall quality of the verification results.

4.5 QA/QC Reporting

Each aud it was documented in accordance with Sections 3.3.4 and 3.3.5 of the QMP for the

ETV AMS Center. The Battelle Verification Test Coordinator prepared formal responses to all audit findings and observations, including any corrective actions taken. The results of the audits and Battelle’s corrective actions were reviewed, approved, and submitted to EPA.

4.6 Data Review

All data received from EPA for the Xact 625 and the reference method underwent 100%

review and validation by Battelle technical staff before being used for any statistical calculations. Records generated in the verification test received a one -over- one review before these records were used to calculate, evaluate, or report verification results. Data were reviewed by a Battelle technical staff member involved in the verification test.13 

### Chapter 5

Statistical Methods

The statistic al methods used to evaluate the quantitative performance factors listed in Section

3.1 are described in this chapter. All results from the Xact 625 monitor and from th e reference sampling and ICP/MS analysis were reported as ambient metals concentrations in nanograms per cubic meter ( ng/m 3 ) of ai r at ambient (i.e., not standard) conditions. Non

detect results from the reference method for any metal were flagged as such, and excluded from any data comparisons.

5.1 Averagi ng of Xact 625 Hourly Data

The Xact 625 readings on each test day consisted of one half-hour measurement and 23 onehour measurements, with all sampling done at the same flow rate (i.e., 16.7 L/min). Consequently, integration of the Xact 625 results over a daily 23.5-hour time period required simple arithmetic averaging of the 24 total concentration results, but with the 0.5-hour result given half the weight of the 23 1-hour results, i.e.:

23.5 Hour Aver age = (0.5c 1 + c 2 + ...c 24 )/23.5 (1)

where c 1 , c 2 , ...c 24 are the metals concentrations reported each hour by the Xact 625.

B efore the resulting daily average results from the Xact 625 monitor were compared to the corresponding daily integrated sample results from the reference method

, they were compared to a daily quantitation limit (QL) of the Xact 625 for each target metal. The QL is a defined value for each target metal and roughly corresponds to 10% uncertainty in an

interference

- free situation. 8 Three distinct hourly QL values were applicable to the Xact 625 data for each metal, and were used to determine the daily QL value for each metal . Those three hourly QL values were:

• The normal hourly QL value for a Xact 625 sample collected over 1 hou r and analyzed by XRF over the following hour. This QL value applies to 22 of the 24 hourly readings reported each day by the Xact 625.

• The QL value for an Xact 625 sample collected between 11:00 pm and midnight,

which wa s collected over 1 hour but only analyzed by XRF for 0.5 hour (due to the internal QC checks performed by the Xact 625 between midnight and 12:30 am). This QL value equal s the normal hourly QL value times √2 (i.e., times 1.414).14 • The QL value for a Xact 625 sample collected between 12:30 am and 1:00 am, which

wa s collected for 0.5 hou r (due to the internal QC checks performed by the Xact 625 between midnight and 12:30 am) b ut analyzed by XRF for 1 h our. This QL value equals the normal hourly QL value times 2.

Daily QL values for each metal reported by the Xact 625 were determined as the appropriately weighted average of the three different hourly QL values. Table 5 -1 list s the three hourly QL values for each of the 23 metal s reported by the Xact 625, along with the resulting daily QL value . A footnote to the table illustrates the calculation procedure used. Daily average Xact 625 result s for any metal that we re less than the Xact 625 daily QL for

that metal were excluded from the statistical calculations summarized below

. For comparison, the detection limits reported by the ICP/MS analysis laboratory for each metal

are also shown in the last column of Table 5-1.

Tabl e 5 -1. Calculation of the Xact 625 D aily QL for Elements Reported in Ambient Air

at the Marietta Site and Comparison to ICP/MS Detection Limits

Element Xact 625 Quantitation Limits Laboratory

ICP/MS

Detection Limit (ng/m 3 ) Normal 1

- hour QL (ng/m 3 ) a 11:00 pm to Midnight QL (ng/m 3 ) b 12:30 to 1:00 am QL (ng/m 3 ) c Calculated Daily QL (ng/m 3 ) d

As 0.81 1.14 1.62 0.84 0.17

Ba 6.68 9.45 13. 4 6.95 0.66

Br 1.31 1.85 2.61 1.35 e

Ca 6.38 9.02 12. 8 6.62 113

Cd 40.6 57. 5 81. 3 42.2 0.01

Co 2.24 3.17 4.48 2.32 0.03

Cr 2.04 2.88 4.08 2.12 24.2

Cu 1.89 2.67 3.78 1.96 2.51

Fe 5.37 7.59 10.7 5.57 e
Hg 1.33 1.89 2.67 1.38 0.05

K 16.7 23. 7 33. 5 17. 4 e

Mn 2.00 2.83 4.00 2.08 0.32

Mo 6.94 9.81 13. 9 7.21 0.19

Ni 1.60 2.26 3.19 1.66 0.40

Pb 1.54 2.18 3.09 1.60 0.07

Rb 2.43 3.44 4.86 2.52 0.02

Sb 4.69 6.63 9.38 4.88 0.28

Se 0.99 1.41 1.99 1.03 0.35

Sr 3.16 4.47 6.33 3.29 0.09

Th 11. 3 1 6.0 22. 6 11.7 0.01

Ti 2.69 3.80 5.37 2.80 e

Tl 1.30 1.84 2.60 1.35 0.003

Zn 1.64 2.31 3.27 1.70 5.93
a: Sample collected over 1 hour and analyzed by XRF over 1 hour; b: Sample collected over 1 hour an d analyzed by XRF over 0.5 hour; c: Sample collected over 0.5 hour and analyzed by XRF over 1 hour. d: Calculated as (22 × Normal QL + (11 pm to midnight QL) + 0.5 × (12:30 to 1:00 am QL))/23.5; e.g., for A s daily QL = (22 × 0.81 + 1.14 + 0.5 × 1.62)/23. 5 = 0.84 ng/m 3

.

e : Element not reported from ICP/MS analysis.15 5.2 Comparability

For e ach target metal, comparability was determin ed by a linear regression of the data using the reference method results as the independent variable and the Xact 625 results as the dependent variable, as follows.

C i = ( m • R i ) + b (2)

w here R i is the ith daily reference measurement, C i is the average of the Xact 625

measurements over the same 2 3.5-hour time period, and m and b are the slope and intercept of the linear regression, respectively. Comparability is reported in terms of the m and b values obtained from the linear regression for each metal determined by the Xact 625 and the

reference method. Comparability results also indicate whether each reported slope or intercept value is significantly different from 1.0 or from zero, respectively (i.e., whether the

95% confidence interval [ CI ] excludes a slope of 1.0 or an intercept of zero, respectively).

5.3 Correlat ion

The de gree of correlation between the Xact 625 results and the reference method results was determined by the coefficient of determination (r 2 ) of the linear regression between the daily reference method results and the corresponding daily averages of the Xact 625 measurements over the same time perio ds. The r 2 value was determined separately for each metal

measured.

5.4 Bias

The bi as of the Xact 625 readings was evaluated in terms of the percent difference of the daily average Xact 625 readings relative to the corresponding daily average reference method

result s . That is, for each target metal (i) in each 2 3.5-hour reference method period (j), bias for that metal in that period ( B i, j ) was calculated as:

B i,j = (Average Monitor Readi ng - Reference Reading) × 100 (3 )

Reference R eading

The bi as results are reported in terms of t he mean, median, range, and SD of the individual

B i,j results for each metal. Also, the individual B i,j results for each metal were compared to

the ambient metal concentration s to determine whether bias is a function of the ambient

concentration of the metal.

5.5 Data Completeness

Data com pleteness (DC) was determined in two ways. The first was as the percentage of all hours in the field period in which the metals monitor report ed ambient metals data, relative to the total number of hours in the field period:

DC1 = (# Hour s data return/Total hours in period) × 100 (4)16 DC w as also calculated as the percentage of all 23.5- hour reference measurement periods during which the monitor report ed at least 12 hours of monitoring data (i.e., produced data

for at least half of the reference monitoring period):

DC2 = (# P eriods with ≥ 12 hours monitor data/# Reference periods) × 100 (5)

Both for ms of DC were calculated for each target metal.17 

### Chapter 6

Test Results

This c hapter summarizes the metals monitoring results from the Xact 625 at the Marietta site, and the comparisons of those results to the corresponding results of the reference sampling and ICP/MS analysis . Section 6.1 shows illustrative results from the Xact 625 and the reference method, and Sections 6.2 through 6.4 show results for the quantitative performance parameters identified in Section 3.1. Section 6.5 summarizes observations on operational

factors of the Xact 625.

6.1 Xact 625 Ambient Metals Results

Mn wa s the predominant toxic metal determined in ambient air during the field period in Marietta, OH. To illustrate the ambient levels observed, Figure 6-1 shows the hourly Xact 625 readings of Mn, potassium (K), iron ( Fe ), and zinc ( Zn ) from December 10, 2011 to February 27, 2012. Although most hourly Mn concentrations were below 10 ng/m 3 , Figure 6-1 shows approximately 20 hourly Mn concentrations exceeding 1 μg/m 3 , with a maximum hourly reading of 5.9 μg/m 3 on February 7. K, Fe, and Zn are shown in Figure 6- 1 because analysis of the Xact 625 data showed those metals to have the highest degree of correlation with the Mn data. Figure 6-1 shows that K and Fe concentrations were similar , and that peak concentrations of these metals often, but not always, coincided with peak concentrations of Mn. The peak concentrations of Mn usually exceeded the simultaneous concentrations of Fe and K. The median hourly Zn concentration was 12 ng/m 3 , but the maximum Zn concentration was 965 ng/m 3 , and occurred on February 7, coincident with the maximum hourly Mn concentration. The concentrations of other metals in Marietta were much lower in this time period. For example, Pb exhibited mean and medi an concentrations of 5.2 and 3.9 ng/m 3 , respecti vely, with a maximum hourly reading of 98 ng/m 3

.

The epi sodes of elevated Xact 625 metals readings in Marietta did not typically consist of single hourly spikes, but rather were periods of elevated concentrations lasting from a few

hours to several hours. As an example, Figure 6 -2 shows the period from February 5 to 7, 2012, in which the highest Mn levels were observed. Figure 6-2 shows that those levels occurred as two separate peaks in an episode that lasted approximately 12 hours.

Table 6- 1 summarize s the 1,829 hourly readings of the 23 metals reported by the Xact 625 in continuous operation at the Marietta site. That table shows the mean, median, maximum, and minimum hourly reading of each metal, and for comparison the Xact 625’s hourly method

detec tion limit (MDL) and hourly QL for each metal, in ng/m 3

.18 0 1000 2000 3000 4000 5000 6000

12/7 12/17 12/27 1/6 1/16 1/26 2/5 2/15 2/25Concentration, ng/m3 Mn

Fe

K

Zn

Figure 6 -1. Xact 625 hourly monitoring data for Mn, K, Fe, and Zn in Marietta, OH from December 10, 2011 to February 27, 2012.

Figu re 6 -2. Example of elevated metals concentrations over a period of several hours

. 0 1000 2000 3000 4000 5000 6000

2/5/2012 15:00 2/6/2012 3:00 2/6/2012 15:00 2/7/2012 3:00 2/7/2012 15:00Concentration, ng/m3 Mn

Fe

K

Zn19 Table 6 -1. Summary of Hourly Values of All Metals Reported by the Xact 625 in Marietta, Ohio from December 10, 2011 to February 27, 2012

Metal Ambient Concentration a ( ng/m 3 ) MDL b
( ng/m 3 ) QL b
( ng/m 3 ) Mean Median Maximum Minimum

As 0.15 < MDL 31.5 < MDL 0.11 0.81

Ba 1.82 < MDL 148 < MDL 0.95 6.68

Br 4.09 3.22 126 < MDL 0.18 1.31

Ca 212 142 1,830 < MDL 0.90 6.38

Cd < MDL < MDL 21.1 < MDL 5.75 40.64

Co < MDL < MDL 0.43 < MDL 0.32 2.24

Cr 0.73 < MDL 106 < MDL 0.29 2.04

Cu 3.11 2.37 450 0.77 0.27 1.89

Fe 126 95.1 1,711 7.91 0.76 5.37 Hg < MDL < MDL 0.62 < MDL 0.19 1.33

K 158 122 4,970 49.8 2.37 16.7

Mn 95.5 6.45 5,910 < MDL 0.28 2.00

Mo c 11.8 11.3 37.3 9.02 0.98 6.94

Ni 0.48 0.30 31.2 < MDL 0.23 1.60

Pb 5.21 3.92 97.7 0.79 0.22 1.54

Rb 0.36 < MDL 26.9 < MDL 0.34 2.43

Sb < MDL < MDL 3.65 < MDL 0.66 4.69

Se 1.28 0.95 11.6 < MDL 0.14 0.99

Sr 1.33 1.07 37.7 < MDL 0.45 3.16

Th < MDL < MDL 4.68 < MDL 1.60 11.3

Ti 9.64 5.93 491 < MDL 0.38 2.69

Tl < MDL < MDL 2.78 < MDL 0.18 1.30

Zn 19.2 12.0 965 1.25 0.23 1.64
a: Based on 1,829 hourly readings.

b: MDL = method detection limit, QL = quantitation limit, for normal hourly data. QL corresponds to 10% uncertainty in an interference

- free situation. 8 MDL corresponds to ±1 SD interference free, consistent with

EPA Method IO 3.3. 8,9

c : See text.

Of t he 23 metals reported by the Xact 625 , 19 were also determined by the ICP / MS analysis of reference samples. For those 19 metals, the daily 23.5-hour averages of the Xact 625 data

were calculated as described in Section 5.1 and compared to the respective daily QL values

listed in Table 5 -1. For 1 2 of those 19 metals ( arsenic [ As ], barium [ Ba ], Cd, cobalt [ Co ] , Cr, mercury [ Hg ], nickel [ Ni ], rubidium [ Rb ], antimony [ Sb ], strontium [ Sr ], thorium [ Th ], and thallium [ Tl ]), the resulting daily average s of the Xact 625 hourly data were almost always below the respective daily QL values of the Xact 625, and consequently no statistical comparison could be made to the reference metals data.

Also , the Xact 625 reported ambient molybdenum ( Mo ) conc entrations that were almost always approximately 12 ng/m 3 throughout the entire field period. This observation is

illustrated in Table 6 -1, in that the minimum hourly Mo value was over 9 ng/m 3 , and the mean and median were 11.8 and 11.3 ng/m 3 , respectively. Th ose Xact 625 Mo results were

identified as a detection artifact by the vendor through inspection of Xact 625 spectral data. Although the Mo data from the field test were affected by this artifact and cannot be used for20 comparison to ref erence data, the vendor indicates that in the future this artifact can be prevented by narrowing the X-ray energy window used for determination of Mo.

For the remaining six metals determined by the Xact 625 ( calcium [ Ca ], Cu, Mn, Pb, selenium [ Se ], and Zn) quantitative comparisons could be made between the daily average Xact 625 results and the daily ICP/MS results. Figure s 6-3 through 6-8 show the linear regression of Xact 625 daily average results against the ICP/MS method results for Ca, Cu, Mn, Pb, Se, and Zn, respectively

. Each of these figures also shows the linear regression equation and r 2 value.

Figu re 6 -3. Linear regression of Xact 625 daily averages against ICP/MS daily averages

for Ca. y = 0.8219x - 30.635
R2 = 0.9792

0 100 200 300 400 500 600 700 800

0 200 400 600 800 1000 1200Xact 625 Result, ng/m3

ICP/MS Result, ng/m 321 Figure 6

- 4. Linear regression of Xact 625 daily averages against ICP/MS daily averages

for Cu.

y = 1.0377x - 0.0938
R2 = 0.9985

0 200 400 600 800 1000 1200

0 200 400 600 800 1000 1200Xact 625 Result, ng/m3

ICP/MS Result, ng/m 3 Excluded

Figure 6

- 5. Linear regression of Xact 625 daily averages against ICP/MS daily averages

for Mn. y = 0.3039x + 2.0701
R2 = 0.3408

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

0.0 2.0 4.0 6.0 8.0 10.0Xact 625 Result, ng/m3

ICP/MS Result, ng/m 322 Figure 6 -6. L inear regression of Xact 625 daily averages against ICP/MS daily averages

for Pb.

y = 0.9862x + 0.0116
r2 = 0.9264

0 0.5

1 1.5

2 2.5

3

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50Xact 625 Result, ng/m3

ICP/MS Result, ng/m 3

Figure 6

- 7. Linear regression of Xact 625 daily averages against ICP/MS daily averages

for Se. y = 1.0595x + 1.5557
R2 = 0.943

0 2 4 6 8 10 12 14 16 18 20

0 2 4 6 8 10 12 14 16 18Xact 625 Result, ng/m3

ICP/MS Result, ng/m 323 Figure 6 -8. Linear regression of Xact 625 daily averages against ICP/MS daily ave rages for Zn.

It shoul d be noted that one data point for Mn in Figure 6-5 has been excluded from the linear regression calculation shown in that figure. That data point is from January 9, 2012, on

which day the Xact 625 reported only 13 hourly readings, for reasons that are described in Section 6.4. This data po int is marked ly offset from all other Mn results in Figure 6 -5, and

has a substantial effect if included in the regression . It is likely given the great variability observed in Mn concentrations that the 13 hourly values report ed by the Xact 625 on Januar y 9 do not adequately indicate the daily average Mn over that entire day, and as a result agree poorly with the reference sample result. The data for other metals from th at same day were

also reviewed , and were found not to be outliers and consequently we re not excluded from

the corresponding regression s. Note that on January 6, 2012 the Xact 625 recorded only 14 hourly readings (see Section 6.4), but no reference sample was collected on that day so there is no impact on the comparison of Xact 625 and ref erence results.

6.2 Comp arability and Correlation

Table 6 -2 summarizes the outcome of linear regression of the daily average Xact 625 results against the corresponding reference results for each target metal for which this comparison

could be made. For each metal Table 6 -2 shows the number of data points in the regression, the slope and intercept of the regression line, and the r 2 value. The slope and intercept result s are shown with t heir associated 95% CI values. Slope results that do not include a value of 1.0 within the 95% CI, and intercept values that do not include a value of 0.0 within the 95% CI, are highlighted by bold font in Table 6-2.

Table 6 -2 shows that the regression slopes for Mn, Pb, Se, and Zn are relatively close to 1.0, although a slope of 1.0 falls slightly outside the 95% CI range of the slope for Mn. The slope y = 0.9713x - 3.0144
r2 = 0.9883

0 20 40 60 80 100 120 140 160 180 200

0 50 100 150 200Xact 625 Result, ng/m3

ICP/MS Result, ng/m 324 Table 6 -2. Results of Linear Regression of Xact 625 and Reference Data

Metal Number of

Data

Points Slope a
(±95% CI) Intercept b
(ng/m 3 )
(±95% CI) Coefficient of

Determination (r 2 )

Ca 47 0.8 22 (± 0.03 5 ) - 30. 6 (± 11.9 ) 0.979

Cu 26 0. 304 (± 0.1 69 ) 2. 07 (± 0.6 47 ) 0.341

Mn 48 1. 038 (± 0.0 12 ) - 0. 094 (± 2.13 ) 0.999

Pb 52 1.0 59 (± 0.0 7 2) 1.5 6 (± 0. 301 ) 0.943

Se 25 0.9 86 (± 0.11 4 ) 0.0 12 (± 0.2 19 ) 0.926

Zn 53 0.9 71 (± 0.029) - 3. 0 1 (± 0.97 7 ) 0.988

a: Values in bold indicate 95% CI does not include slope of 1.0.

b: Values in bold indicate 95% CI does not include intercept of zero.

for Ca, and es pecially the slope for Cu, are substantially less than 1.0. Table 6-2 also shows that the regression intercepts for Ca, Cu, Pb, and Zn differ significantly from zero. As shown in Figures 6 -3 to 6-8, the concentration ranges of the target metals and the numbers of data points available for regression analysis differ greatly among the six metals. In that regard the strikingly different regression results for Cu and Se are noteworthy, given the similarly low concentration ranges and the relatively small numbers of data points available for these metals (Figures 6 -4 and 6-7, respectively). A likely cause of the weak regression for Cu is

that the Cu concentrations were near bo th the detection limit of the ICP/MS analysis and the QL of the Xact 625. In addition, after the field period in Marietta was completed the vendor of the Xact 625 investigated Xact 625 XRF spectra, including a spectrum of a blank section of the Xact 625’s filter tape obtained prior to the start of monitoring in Marietta. The vendor indicated a Cu reading on the blank tape equivalent to approximately 6 ng/m 3 . A single blank analysis result must be viewed with caution, but this observation suggests that Xa ct 625 tape background may have contributed to the regression results for Cu, and that analysis of a blank spot on the filter tape should be part of the routine daily QC checks of the Xact 625. Such a blank analysis is generally recommended by the vendor but was not included among the automated QC procedures implemented by the vendor for this verification.

With the e xception of Cu Table 6-2 shows strong correlation of the Xact 625 and reference method results, with r 2 value s ranging from 0.926 for Se to 0.999 for Mn.

The regre ssion plots for Ca, Mn, Pb, and Zn (Figures 6-3, 6-5, 6-6, and 6-8) each show one data point that is at a much higher concentration than all other data points. To assess whether these single data points unduly influenced the regression results shown for tho se metals in

Table 6 -2, the regressions were also calculated without these single data points. The impact of these single points on the respective regression results was found to be minimal. For example, for Ca, Mn, and Zn the regression slope changed by 0.018 or less upon exclusion of the highest data point, r 2 values also changed only slightly, and no changes occurred in the25 significance of the difference of slope values from 1.0 or intercept values from 0.0. A small

effect was seen for Pb, for which exclusion of the highest data point increased the regression slope from 1.059 to 1.149 (the latter significantly different from 1.0), decreased the intercept from 1.556 to 1.305 (both significantly different from 0.0), and reduc ed r 2 from 0.943 to 0.914. Nevertheless, these small differences do not alter the overall picture of the Xact 625’s performance relative to the reference method in determining Pb. It was concluded that the single high data points in the regressions for Ca, Mn, Pb, and Zn do not exert undue effect on the regression results for these metals , and these data points were included in the regressions.

6.3 Bias

Table 6- 3 summarizes the bias results for the six metals for which Xact 625 results can be compared to the ICP/MS results . The bias values were calculated according to Equation 3 in

Section 5.4. Shown in Table 6- 3 for each metal are the mean (± SD) , median, and range of the individual bias values found by this comparison.

Table 6 -3. Bias of Xact 625 Results Relative to Reference Results

Metal Number of

Data Points Bias (%)
Mean (± SD) Median Range

Ca 47 - 31. 3 (± 9.5 ) -31.0 -57.0 to -9.8

Cu 26 - 5.6 (± 2 2.1 ) 1.2 -56.0 to 26.2

Mn 48 1.1 (± 21.8 ) -0.6 -33.3 to 103

Pb 52 74. 8 (± 5 4.3 ) 61.9 8.7 to 33 9

Se 25 - 0. 7 0 (± 8. 1 ) -1.3 -15.9 to 17.7

Zn 53 - 20.5 (± 1 5.4 ) -17.9 -59.3 to 27.6

The per cent bias results in Table 6 -3 appear to present a different picture than the regression results in Section 6.2, in that (e.g.) a low average bias is indicated for Cu and a relatively large average bias for Pb. The bias results are sensitive to the magnitude of the concentrations being compared, i.e., a small quantitative difference in measurement results can equate to a large percent bias if the reference result is a small concentration. Consequently, a regression equation and r 2 value indicating similarity of results may not

correspo nd to low percent bias values. A good example is Pb, for which the regression line is shown in Figure 6-5. Although the regression slope for Pb is only slightly above 1.0 (i.e., 1.059), the positive intercept of approximately 1.5 ng/m 3 is relatively large compared to the reference Pb concentrations, more than half of which are less than about 3 ng/m 3

.

Afte r the field period in Marietta was completed the vendor of the Xact 625 analyzed the XRF spectrum of a blank section of the Xact 625’s filter tape obtained prior to the start of monitoring in Marietta, and observed a blank Pb level equivalent to approximately 1 ng/m 3

.26 This observation indicates that the Xact 625 filter tape background may have contributed significantly to the positi ve intercept for Pb

, reinforc ing the suggestion made in Section 6.2 that analysis of the blank filter tape should be part of the routine daily QC checks of the Xact

625.

In the c ase of Ca, the combination of a relatively low slope and relatively large negative intercept (Figure 6 -3 ) contribute to the negative bias values shown in Table 6-3. On the other hand, i n the case of Cu the relatively random magnitude and direction of the differences between Xact 625 and ICP/MS results shown in Figure 6-3 result in an overall average percent bias close to zero despite a wide range of individual bias values.

The infl uence of the absolute magnitude of the measured concentrations on the percent bias results is illustrated in Figure 6 -9, which plots the individual percent bias values for Pb as a function of the reference method concentrations for that metal. The percent bias values for Pb are all positive, but clearly decline sharply as the reference Pb concentration increases.

Figure 6 -9. Percent bias results for Pb as a function of the reference concentration.

6.4 Data Completeness

The DC fo r the Xact 625 in operation at the Marietta site was calculated in two ways as

described in Section 5.5

. DC for each metal was calculated both as the percentage of hourly

data collected during the verification testing period

, and as the percentage of the 23.5-hour daily averaging periods in which the Xact 625 provided at least 12 readings. Hourly DC w as calculated over both the entire period of operation of the Xact 625 in Marietta (December 10, 2011 to February 27, 2012; 1,905 total possible hours ) and over the 65-day period during which the reference samples were collected (December 23 to February 25 ; 1,560 total 0 50 100 150 200 250 300 350 400

0 5 10 15 20Bias of Xact 625 Result, %

ICP/MS Pb Result, ng/m 327 possible hours ). Completeness relative to daily 23.5-hour periods was calculated only for the latter period. Table 6 -4 summarizes the DC results.

Table 6 -4. Data Completeness for the Xact 625

Measure of Completeness Time Period Value (%) Completeness of Hourly

Data 12/10/11 to 2/27/12 96.0

Completeness of Hourly

Data 12/23/11 to 2/25/12 95.4

Percentage of Days with
≥12 Hours of Data 12/23/11 to 2/25/12 96.9

Table 6

- 4 shows that the completeness of the Xact 625’s hourly data was greater than 95% over both its entire operational period at the Marietta site and over the 65-day period of reference sampling. By far the largest episode of missing Xact 625 data was from 3:00 pm

on Frid ay , January 6 to 11:00 am on Monday, January 9, 2012. This loss of data resulted when the Xact 625 software opened a second XRF control screen, causing routine sampling to be interrupted. No reason could be found for this event, but because the data loss began on a Friday afternoon, the problem was not discovered and corrected until site operators visited

the site on the following Monday. This event caused the Xact 625 to produce only 14 hourly readings on January 6, none on January 7 and 8, and 13 hourly readings on January 9. On all other sampling days between December 23 and February 25

, the Xact 625 returned at least 22 hourly readings. Thus, the Xact 625 provided hourly readings for less than 12 hours on only two days out of the 65 days on which reference sampling occurred.

6.5 Oper ational Factors

The Xact 625 was installed in the field trailer shown in Figure 3-1 prior to its arrival at the field site. Consequently, installation of the Xact 625 was not evaluated in this test. Startup of the Xact 625 was straightforward upon setup of the field trailer at the test site, and the analyzer was ready for routine operat ion within about one day after electrical power was

connected to the trailer. The Xact 625 operated reliably throughout the field test, as indicated by the DC results in Section 6.4, and required minimal operator attention. The filter tape in the analyzer was replaced approximately every 2 weeks, but no other routine maintenance was needed. During the period in which the Xact 625 was installed at the East Liverpool site, the temperature and barometric pressure sensors of the analyzer malfunctioned, invalidating the Xact 625 data from that site. However, that malfunction was caused by the design and installation of connectors for those sensors in an exposed location on the roof of

the field trailer, and not by an issue with the Xact 625 itself.

The X act 625 was programmed to carry out several internal automated QC checks on a daily basis, and did so without interruption during the field period. The results of these QC checks are summarized in Section 4.3, and demonstrated stab le performance , minimal flow variation, and close agreement with calibration standards throughout the entire field period at both the East Liverpool and Marietta sampling sites. Analysis of the Xact 625’s blank filter28 tape to determine background metals levels was not part of the mo nitor’s automated daily QC

checks. However the results reported above, and investigations conducted by the vendor after the Marietta field period, indicate that inclusion of blank filter analysis in such QC checks may be valuable.

The dat a files produced by the Xact 625 clearly distinguished the QC analysis periods from the normal hourly ambient sampling periods, and included a variety of analyzer operating data in addition to the measured ambient metals concentrations in ng/m 3 . Those operating

d ata included ambient and internal analyzer temperatures, ambient barometric pressure and tape pressure drop, sample flow rates in actual and standard units, sample volumes, and alarm and QC indications. The data files were well organized and allowed quick review to assess Xact 625 operations and QC results, such as those summarized in Section 4.3. Xact 625 data files were reviewed at least weekly by a Pall Corporation representative to assess the analyzer’s operating stability, but the data files were cle ar enough that a similar review could be performed by any user familiar with the file format.

The purch ase price of the Xact 625 at the time of preparation of this report was approximately $180,000

. This price is subject to change.29 

### Chapter 7 Performance Summary

Of the 23 ambient PM 10 metals determined by the Xact 625 in this verification, 1 9 were also determined by the ICP/MS analysis of referen ce samples. Of those 19 metals , Xact 625

results for 1 2 metals were almost always below the respective QLs of the Xact 625, and for

one other metal (Mo) the Xact 625 reported a nearly constant and unrealistic ambient concentration due to an incorrect energy window for that metal in the XRF analys is. The vendor of the Xact 625 indicates that this problem can be avoided in the future by narrowing the energy window. Table 7 -1 presents a summary of the quantitative performance results of

the Xact 625 for the remaining six metals, showing the perform ance parameters and resulting performance metrics.

Tabl e 7 -1. Quantitative P erformance Results for the Xact 625

Performance

Parameter Metal Metric

Comparability Slope Intercept (ng/m 3 )

Ca 0.8 22

- 30. 6

Cu 0. 304 2. 07

Mn 1. 038

- 0. 094

Pb 1.0 59 1.5 6

Se 0.9 86 0.0 12

Zn 0.9 71

- 3. 0 1

Correlation Coefficient of Determination (r 2 )

Ca 0.97 9

Cu 0. 341

Mn 0.9 99

Pb 0.9 43

Se 0.92 6

Zn 0.98 8

Bias Mean (%) Median (%)

Ca

- 3 1. 3

- 3 1.0

Cu

- 5.6 1. 2

Mn 1.1

- 0.6

Pb 74. 8 61.9

Se

- 0. 7

- 1.3

Zn

- 20.5

- 1 7.9

Data Completeness Hourly Data (%) Daily Averages
with ≥ 12 Hours (%)

All 95.4 to 96.0 96.930 Table 7

- 1 indicates that the daily average Xact 625 results were highly correlated and in close quantitative agreement with ICP/MS analysis results for most of the six metals, and that the Xact 625 achieved data completeness of over 95%. The regression re sults for Cu reflect the fact that Cu concentrations were often near the detection limit of the ICP/MS analysis and the QL of the Xact 625. In addition, investigations conducted after the verification test suggest that the regression results for Cu and th e bias results for Pb may have been affected by the levels of these metals in the Xact 625’s blank filter tape.

The Xa ct 625 required minimal operator attention during testing, with routine maintenance

consis ting of changing the sampling tape approximatel y every 2 weeks. The monitor

conducted several automated internal QC checks on a daily basis, and provided readily understandable data files that distinguished QC from ambient monitoring results and included analyzer flow and internal readings. T he RSD o f the Pd internal standard readings determined in every Xact 625 XRF analysis was 2.04%. The monitor ’s average flow error

was -0.69% (± 0.004%), where the value in parentheses is the SD of the daily flow check results. The average accuracy relative to upscale rod check standards analyzed daily was 100.21% (±0.004%) for Cr, 100.55% (±0.013%) for Cd, and 99.79% (±0.007%) for Pb, where accuracy of 100% represents perfect agreement with the upscale rod check standard.
However, t he test results noted above for Cu and Pb strongly indicate that analysis of blank portions of the filter tape should be a component of the Xact 625’s automated internal QC

checks.31 

### Chapter 8

References

1. Scho ol Air Toxics Monitoring Initiative, information available at http://www.epa.gov/ttn/amtic/airtoxschool.html

.

2. Quali ty Assurance Project Plan for the Verification of the Xact 625 Ambient Particulate Metals Monitor, Battelle, Columbus, Ohio, August 2011

3. U.S. EPA, Environmental Technology Verification Program Quality Management Plan, EPA Report No: 600/R

- 08/009 EPA/600/R

- 03/021, U.S. Environmental Protection Agency, Cincinnati, Ohio, January 2008.

4. Battelle, Quality Management Plan for the ETV Advanced Monitoring Systems Center, Version 7.0, U.S. EPA Environmental Technology Verification Program, prepared by Battelle, Columbus, Ohio, November 2008.

5. Compendi um method IO-3.1, Selection, Preparation, and Extraction of Filter Material, in Compendium of Methods for the Determination of Inorganic Compounds in Ambient Air

, EPA/625/R-96/010a, U.S. Environmental Protection Agency Office of Research and Development, June 1999.

6. Met hod IO -3.5, Determination of Metals in Ambient Particulate Matter Using Inductively Coupled Plasma/Mass Spectrometry (ICP/MS), in Compendium of Methods for the Determination of Inorganic Compounds in Ambient Air , EPA/625/R-96/010a, U.S. Environmental Protection Agency Office of Research and Development, June 1999.

7. Quali ty Assurance Project Plan for Support for the EPA National Monitoring Programs (NMO C, UATMP, PAMS, HAPs, and NATTS) , EPA Contract EP-D-09-048, ERG, Morrisville, North Carolina, 2011.

8. C urri e, Lloyd A. , Detection and Quantitation in X- Ray Fluorescence Spectrometry. In X

ray Fluorescence Analysis of Environmental Samples, Dzubay, Thomas B. , ed. ; Ann Arbor Science, Ann Arbor, MI, 1978; pgs. 289-305.

9. Met hod IO -3.3, Determination of Metals in Ambient Particulate Matter Using X- Ray Fluorescence (XRF) Spectroscopy, in Compendium of Methods for the Determination of Inorganic Compounds in Ambient Air , EPA/625/R-96/010a, U.S. Environmental Protection Agency Office of Research and Development, June 1999.