Prepared in cooperation with the U.S. Centers for Disease Control and Prevention and the Maine 

Center for Disease Control and Prevention

Methods of Collection and Quality Assessment of Arsenic 

Data in Well-Water Supplies in Maine, 2001–2 and 2006–7

U.S. Department of the Interior

U.S. Geological Survey

Data Series 1125

Methods of Collection and Quality 

Assessment of Arsenic Data in Well-Water 

Supplies in Maine, 2001–2 and 2006–7

By Charles W. Culbertson, James M. Caldwell, Luther F. Schalk,

Deana Manassaram, Lorraine C. Backer, and Andrew E. Smith

Prepared in cooperation with the U.S. Centers for Disease Control and 

Prevention and the Maine Center for Disease Control and Prevention

Data Series 1125

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, visit 

https://store.usgs.gov/.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Culbertson, C.W., Caldwell, J.M., Schalk, L.F., Manassaram, D., Backer, L.C., and Smith, A.E., 2020, Methods of 

collection and quality assessment of arsenic data in well-water supplies in Maine, 2001–2 and 2006–7:

U.S. Geological Survey Data Series 1125, 11 p., https://doi.org/10.3133/ds1125.

Associated data for this publication:

Culbertson, C.W., Caldwell, J.M., Schalk, L.F., and Medalie, L., 2020, Arsenic datasets and other physical and 

chemical measurements for selected domestic well-water supplies in Maine—2001–2 and 2006–7:

U.S. Geological Survey data release, https://doi.org/10.5066/P9X5HVDF.

ISSN 2327-638X (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Description of Study Area ...................................................................................................................2

Methods of Data Collection .........................................................................................................................2

Measurement of Field Water-Quality Constituents .........................................................................2

Sample Collection for Well-Water Chemical Analyses Performed in the Field .........................2

Point-of-Entry and Point-of-Use Sample Collection for Laboratory Chemical 

Analysis of Well Water ...........................................................................................................2

Point-of-Entry and Point-of-Use Sample Collection for Laboratory Arsenic and 

Arsenic Speciation (Valence) Analysis ...............................................................................8

Arsenic Sample Preparation and Preservation ...............................................................................8

Preparation of Field Anion-Exchange Chromatography Columns for Arsenic 

Speciation Analysis ................................................................................................................8

Quality Assessment of Laboratory Arsenic Analysis ...............................................................................9

References Cited..........................................................................................................................................10

Figures

1. Map showing domestic-well sample locations in Maine, 2001–2 and 2006–7 ...................3

2. Boxplots showing distribution of unfiltered arsenic concentrations in paired

samples analyzed by the Maine Department of Human Services Health and

Environmental Testing Laboratory (HETL) and Underwriters Laboratories Inc.

(UL), 2006–7....................................................................................................................................9

3. Graph showing arsenic concentrations in paired samples analyzed by the

Maine Department of Human Services Health and Environmental Testing

Laboratory and Underwriters Laboratories Inc., 2006–7 ........................................................9

Tables

1. Method information, minimum reporting limits, and U.S. Geological Survey

National Water Information System parameter codes for all constituents

measured in water samples collected from domestic wells in Maine for

laboratory analyses, 2001–2 and 2006–7 ...................................................................................4

2. Constituents, U.S. Geological Survey National Water Information System

parameter codes, minimum reporting limits, and method information for all

water samples collected from domestic wells in Maine for analyses performed

in the field, 2001–2 and 2006–7 ...................................................................................................5

3. Constituents, field parameters, arsenic speciation, and measuring entities for

water samples collected from domestic wells in Maine, 2001–2 and 2006–7 ....................7

4. Representative efficiency of anion-exchange chromatography resin for the

field separation of As(III) and As(V) for single arsenic species recovery ........................10

5. Representative efficiency of anion-exchange chromatography resin for the

field separation of As(III) and As(V) for As(III)+As(V) mix recovery ..................................10
iv

Conversion Factors

International System of Units to U.S. customary units

Multiply By To obtain

Length

micrometer (μm) 0.00003937 inch (in.)

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Volume

cubic meter (m3) 6.290 barrel (petroleum, 1 barrel = 42 gal)

milliliter (mL) 0.03381 ounce, fluid (fl. oz)

Flow rate

liter per second (L/s) 15.85 gallon per minute (gal/min)

Mass

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as

 °F = (1.8 × °C) + 32.

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm 

at 25 °C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).

Turbidity is reported in nephelometric turbidity units (NTU).

Concentrations of bacteria are reported in colony forming units per 100 milliliters (CFU/100 mL).
v

Abbreviations

EPA U.S. Environmental Protection Agency

HETL Health and Environmental Testing Laboratory, Maine Department of Human Services

NWQL National Water Quality Laboratory

POE point of entry

POU point of use

QA/QC quality assurance and quality control

UL Underwriters Laboratories Inc.

USGS U.S. Geological Survey

Methods of Collection and Quality Assessment of Arsenic 

Data in Well-Water Supplies in Maine, 2001–2 and 2006–7

By Charles W. Culbertson,1 James M. Caldwell,1 Luther F. Schalk,1 Deana Manassaram,2 Lorraine C. Backer,2

and Andrew E. Smith3

Abstract

The U.S. Geological Survey, in cooperation with the 

U.S. Centers for Disease Control and Prevention and the 

Maine Center for Disease Control and Prevention, assessed 

the chemical characteristics and the occurrence, distribution, 

and oxidation state of inorganic arsenic in drinking water from 

selected domestic well-water supplies in Maine in 2001–2 

and 2006–7.

The data collected provide support for evaluating arsenicremoval efficiencies of household water-purification systems 

and provide information to State and local officials that can 

be used in determining a water-treatment approach for the 

removal of arsenic from drinking water.

Introduction

Arsenic is toxic to humans and widespread in surface 

water and groundwater throughout the United States and world 

(National Research Council, 1999; Welch and others, 1999; 

Welch and others, 2000; Focazio and others, 2000; Ryker, 

2001; Smedley and Kinniburgh, 2002; DeSimone and others, 

2009). Arsenic in surface waters and groundwater aquifers 

has both anthropogenic and natural sources. Anthropogenic 

sources include current and historical industrial uses, as well 

as broad-spectrum uses in the lumber, agriculture, and livestock industries (National Research Council, 2001). Arsenic 

occurs naturally in the Earth’s crust, ranking as the 20th most 

abundant element, with an average crustal abundance of 

approximately 2 milligrams per kilogram (0.0002 percent). 

It is common in weathered volcanic and marine sedimentary rocks containing iron and manganese oxides, in fossil 

fuels, and in a number of minerals, including arsenopyrite 

(FeAsS), orpiment (As2S3), scorodite (FeAsO4), and realgar 

(AsS) (Cullen and Reimer, 1989; Korte and Fernando, 1991; 

Smedley and Kinniburgh, 2002).

1U.S. Geological Survey.

2U.S. Centers for Disease Control and Prevention.

3Maine Department of Health and Human Services.

Arsenic in groundwater is primarily inorganic, either in 

the oxidized state as arsenate [As(V)], the form typical in oxic 

waters, or the reduced state as arsenite [As(III)], the form typical in anoxic waters (Cullen and Reimer, 1989; Smedley and 

Kinniburgh, 2002).

Roughly half of the population of Maine derives its 

drinking water from domestic wells, of which about 75 percent are drilled bedrock wells. Arsenic concentrations above 

the current U.S. Environmental Protection Agency (EPA) 

drinking-water standard of 10 micrograms per liter (μg/L or 

parts per billion) (U.S. Environmental Protection Agency, 

2001) have been detected in water from drilled bedrock wells 

throughout Maine (Marvinney and others, 1994, 1995; Peters 

and others, 1999; Ayotte and others, 1999, 2003, 2006; Lipfert 

and others, 2006; Yang and others, 2009; Nielsen and others, 

2010; Zheng and Ayotte, 2015; Flanagan and others, 2012). 

Effective removal of arsenic by household water-purification 

systems is constrained by the chemical form (for example, 

oxidation state) in which it occurs, as well as the prevailing chemical characteristics of the well water, including 

pH, and the presence of competing ions, such as phosphate 

(U.S. Environmental Protection Agency, 2001).

The U.S. Geological Survey (USGS), in cooperation with 

the U.S. Centers for Disease Control and Prevention and the 

Maine Center for Disease Control and Prevention, assessed 

the chemical characteristics and the occurrence, distribution, 

and oxidation state of inorganic arsenic in drinking water from 

selected domestic well-water supplies in Maine in 2001–2 

and 2006–7.

The data collected provide support for evaluating arsenicremoval efficiencies of household water-purification systems 

and provide information to State and local officials that can 

be used in determining a water-treatment approach for the 

removal of arsenic from drinking water.

Purpose and Scope

This report describes methods used to collect arsenic 

and other water-chemistry data from domestic well water 

in support of studies evaluating arsenic removal efficiencies of household water purification systems. Data consist 

of water-chemistry results from samples collected over two 

time periods: 2001–2 and 2006–7 (also two samples collected 
2 Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine

in 2008), well characteristics (depth and type), and chemical 

characteristics of well water from approximately 120 selected 

domestic wells in known high-arsenic clusters throughout the 

State of Maine. All data are available in the USGS National 

Water Information System (NWIS) database, are searchable 

by USGS site number (U.S. Geological Survey, 2019), and are 

published in Culbertson and others (2020).

Description of Study Area

The study area includes most of the populated areas in 

the State of Maine apart from Aroostook County in northeastern Maine. The samples collected were from singlefamily dwellings relying on private well water as the primary 

drinking-water supply; additionally, these households had 

water-purification systems designed for the removal of arsenic 

installed either at the well-water point of entry (POE) or point 

of use (POU). The initial pilot study included 31 households 

sampled for arsenic and arsenic species in 2001–2, whereas 

the full-scale study included 120 households sampled in 

2006–7. Households were recruited based on their locations in 

areas of Maine known to have high concentrations of arsenic 

(>10 μg/L) in groundwater (fig. 1).

Methods of Data Collection

Households with domestic wells included in this study 

were identified and prescreened prior to both sampling periods 

by project personnel associated with concurrent studies by 

the U.S. Centers for Disease Control and Prevention and the 

Maine Center for Disease Control and Prevention. To be considered for the study, households needed to have well water 

containing elevated (>10 μg/L) concentrations of arsenic and 

a previously installed water-purification system designed 

to remove arsenic; systems used reverse-osmosis, anionexchange, or adsorption technologies. Most homes tested had 

point-of-use reverse-osmosis systems installed. Well-water 

samples (pre-water-treatment system) were collected at the 

house POE, prior to the pressure tank and household watertreatment system(s), by using the existing domestic well-water 

pump. Samples collected after water treatment were collected 

at the kitchen (POU) faucet. A list of constituent names, 

USGS NWIS parameter codes, and minimum reporting limits 

for all samples collected for laboratory and field analyses are 

shown in tables 1 and 2. A summary of field measurements 

and analytical determinations, along with the entity or entities 

that analyzed or measured each, is presented in table 3.

Measurement of Field Water-Quality 

Constituents

Prior to collection of POE well water for arsenic and 

other chemical analyses, field measurements of temperature, specific conductance, pH, and dissolved oxygen were 

measured onsite using a multiparameter water-quality monitor 

immersed in a flow-through chamber under a steady water 

flow of approximately 1–1.5 liters per minute. Field measurements and water-chemistry results are published in Culbertson 

and others (2020). During the 2006–7 sample collection 

period, low dissolved oxygen readings (<1 mg/L) were 

confirmed by an alternate, colorimetric method (CHEMets 

colorimetric dissolved oxygen test kit, 0–1 part per million; CHEMetrics, Inc., Calverton, Va.). Samples for water 

chemistry determinations and arsenic analyses were collected 

after water-quality-monitor readings had stabilized (generally 0.25–0.75 hour). Except for specific conductance, field 

measurements of the other water-quality constituents in 

POU water samples were not made because of physical and 

chemical alterations imparted by the water-treatment systems. 

Specific conductance, a proxy for total dissolved solids, was 

measured in both prefiltration and postfiltration water, specifically to assess the performance efficiencies of reverse-osmosis 

water-treatment systems in removing arsenic (Fravel and 

Lindsey, 2014).

Sample Collection for Well-Water Chemical 

Analyses Performed in the Field

Upon obtaining stabilized readings of temperature, specific conductance, and pH, well-water samples for field chemical analyses were collected. Field measurements (or analyses) 

of POE well water included total iron, ferrous iron (FeII), total 

manganese, reactive phosphorus, sulfate, sulfide, and nitrate. 

These measurements were made immediately upon sample 

collection using standard colorimetric methods (American 

Public Health Association, 1998; Hach Company, 2000). 

Equipment blanks and sample replicates for quality-control 

(QC) purposes were collected and analyzed with the field 

samples. Additionally, during the 2006–7 sample collection 

period, replicate samples for some constituents were collected 

for chemical analysis by an alternate laboratory and method 

(Underwriters Laboratories Inc. [UL], South Bend, Indiana). 

Results of field chemical and quality-control analyses are 

published in Culbertson and others (2020).

Point-of-Entry and Point-of-Use Sample 

Collection for Laboratory Chemical Analysis of 

Well Water

According to study protocols for the 2006–7 study, two 

laboratories (Underwriters Laboratories Inc. [UL], South 

Bend, Indiana, and the Health and Environmental Testing 

Laboratory [HETL] of the Maine Department of Human 

Services4 in Augusta, Maine) were used to measure arsenic 

concentrations. The laboratory results from these two facilities 

are published here as a means of comparison of the analytical 

4Since July 2004, the Maine Department of Health and Human Services.
Methods of Data Collection 3

SOMERSET

PISCATAQUIS

PENOBSCOT

OXFORD

WASHINGTON

YORK

FRANKLIN

HANCOCK

WALDO

KENNEBEC

CUMBERLAND

LINCOLN

ANDROSCOGGIN

CANADA

CANADA

GULF OF MAINE

MAINE

KNOX

SAGADAHOC

NH

MA

71 ̊ 70 ̊ 69 ̊ 68 ̊ 67 ̊

46 ̊

45 ̊

44 ̊

43 ̊

EXPLANATION

County boundary

Study site

Pilot and study site

Pilot site

ATLANTIC OCEAN

Gulf of Maine

NEW

HAMPSHIRE

VERMONT

MAINE

NEW YORK MASSACHUSETTS

CANADA

Map area

0 50 KILOMETERS

0 25 50 MILES

25

Figure 1. Domestic-well sample locations in Maine, 2001–2 and 2006–7.
4 Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine Table 1. Method information, minimum reporting limits, and U.S. Geological Survey National Water Information System parameter codes for all constituents measured in water samples collected from domestic wells in Maine for laboratory analyses, 2001–2 and 2006–7. [Samples were collected for laboratory measurements before (point-of-entry, POE) and after (point-of-use, POU) household water-treatment systems. CASRN, Chemical Abstracts Service Registry Number; method reference, indicates the method code number associated with U.S. Environmental Protection Agency analytical methods, Standard Methods for the Examination of Water and Wastewater analytical methods, or U.S. Geological Survey (USGS) National Water Quality Laboratory analytical methods; MCL, maximum contaminant level; SMCL, secondary maximum contaminant level; MRL, minimum report- ing limit; N/A, not applicable; mg/L, milligram per liter; CaCO3, calcium carbonate; UL, Underwriters Laboratories Inc.; μg/L, microgram per liter; HETL, Maine Department of Human Services Health and Environmental Testing Laboratory; NWQL, National Water Quality Laboratory; As, arsenic; CFU/100 mL, colony forming units (colonies) per 100 milliliters; N, nitrogen; NTU, nephelometric turbidity units] Constituent CASRN1 Method reference MCL/ SMCL Unit MRL USGS param- eter code USGS method code Analyzing entity Analyte description Alkalinity, total N/A 2320 B2 N/A mg/L as CaCO3 10 29803 TT060 UL Alkalinity, water, filtered, Gran titration, laboratory, milligrams per liter as calcium carbonate. Arsenic 7440-38-2 200.83 10 μg/L 5 01002 PM100 UL Arsenic, water, unfiltered, micrograms per liter. Arsenic 7440-38-2 200.83 10 μg/L 0.5 01002 PLM99 HETL Arsenic, water, unfiltered, micrograms per liter. Arsenic 7440-38-2 GF0964 10 μg/L 1.9 01002 GF096 USGS- NWQL Arsenic, water, unfiltered, micrograms per liter. Arsenic 7440-38-2 200.83 10 μg/L 0.5 01000 PLM98 HETL Arsenic, water, filtered, micrograms per liter. Arsenite 15502-74-6 200.83 10 μg/L as As 0.5 62452 PLM98 HETL Arsenite, water, filtered, micrograms per liter as arsenic. Arsenate 15584-04-0 200.83 10 μg/L as As 0.5 62453 PLM98 HETL Arsenate, water, filtered, micrograms per liter as arsenic. Fecal coliform N/A 9222 D2 1 CFU/100 mL 1 31616 BAC93 UL Fecal coliform, M-FC MF (0.45 micrometer) method, water, colony forming units per 100 milliliters. Fluoride 16984-48-8 300.03 4 mg/L 0.1 00951 IC075 UL Fluoride, water, unfiltered, milligrams per liter. Hardness, total N/A 2340 B2 N/A mg/L as CaCO3 10 00909 TT099 UL Hardness, water, unfiltered, measured, milligrams per liter as cal- cium carbonate. Iron, total 7439-89-6 200.73 0.3 mg/L 0.02 74010 PLA44 UL Iron, water, unfiltered, milligrams per liter. Lead 7439-92-1 200.83 15 μg/L 5 52298 PM100 UL Lead, water, unfiltered, micrograms per liter. Manganese 7439-96-5 200.83 50 μg/L 5 71883 PM100 UL Manganese, water, unfiltered, micrograms per liter. Nitrate 14797-55-8 353.23 10 mg/L as N 1 00630 CDR25 UL Nitrate plus nitrite, water, unfiltered, milligrams per liter as nitrogen. Nitrite 14797-65-0 353.23 1 mg/L as N 0.1 00615 CDR25 UL Nitrite, water, unfiltered, milligrams per liter as nitrogen. pH N/A 150.13 6.5–8.5 pH units N/A 00403 EL022 UL pH, water, unfiltered, laboratory, standard units. Sodium 7440-23-5 200.73 N/A mg/L 0.1 52290 PLA44 UL Sodium, water, unfiltered, milligrams per liter.

Sulfate 14808-79-8 300.03 250 mg/L 10 00946 IC075 UL Sulfate, water, unfiltered, milligrams per liter.Turbidity N/A 180.1 LL3 N/A NTU 0.1 82079 TBD05 UL Turbidity, water, unfiltered, laboratory, nephelometric turbidity units.Uranium 7440-61-1 200.83 30 μg/L 5 63032 PM100 UL Uranium, water, unfiltered, micrograms per liter.

1This report contains CAS Registry Numbers, which is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client Services.2Analytical method code from “Standard Methods for the Examination of Water and Wastewater” (American Public Health Association, 1998).3Analytical method code from the U.S. Environmental Protection Agency.4Analytical method code from the USGS National Water Quality Laboratory.
Methods of Data Collection 

5

Table 2. Constituents, U.S. Geological Survey National Water Information System parameter codes, minimum reporting limits, and method information for all water samples collected from domestic wells in Maine for analyses performed in the field, 2001–2 and 2006–7.[USGS, U.S. Geological Survey; MRL, minimum reporting limit; mg/L, milligram per liter; CASRN, Chemical Abstracts Service Registry Number; N, nitrogen; wu, water, unfiltered; NEWSC, New England Water Science Center; PO4, phosphate; °C, degree Celsius; NA, not applicable; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ppm, part per million; % saturation, percent saturation; std units, standard units; gal/min, gallon per minute]

Constituent

USGS

parameter 

code

Units MRL (mg/L) CASRN1

Analytical 

method 

number 

reference2

USGS 

method 

code

USGS method name Method description

Field chemistry parameters

Nitrate, water, unfiltered, 

field, milligrams per liter as nitrogen

99124 mg/L as N 0.1 14797-55-8 8039 CDR23 Nitrate, wu, field, colorimetry, 

Hach test kit (NEWSC)

Field determination of nitrate in unfiltered water 

by cadmium reduction colorimetry method with Hach Test Kit.

Sulfate, water, unfiltered, 

field, milligrams per liter

99127 mg/L 1 14808-79-8 8051 CL203 Sulfate, wu, field, colorimetry, 

Hach test kit (NEWSC)

Field determination of sulfate in unfiltered water 

with Hach Test Kit, SulfaVer 4 method.

Orthophosphate, water, 

unfiltered, milligrams per liter as PO4

99126 mg/L 0.01 7723-14-0 8048 ASC20 Phosphate (orthophosphate), 

wu, field, colorimetry, Hach test kit (NEWSC)

Field determination of phosphate in unfiltered 

water with Hach Test Kit, PhosVer 3 (ascorbic acid) method.

Iron(II), water, unfiltered, 

field, milligrams per liter

99128 mg/L 0.01 15438-31-0 8146 PHEN5 Iron(II), wu, field, Hach 

colorimetry

Iron(II) in unfiltered water determined in the 

field by the 1,10-phenanthroline method with portable colorimeter using Hach AccuVac ampules. Range up to 3.00 mg/L.

Iron, water, unfiltered, field, 

milligrams per liter

99138 mg/L 0.01 7439-89-6 8008 CL204 Iron, total, wu, field, colorimetry, Hach test kit 

(NEWSC)

Field determination of total iron in unfiltered 

water with Hach Test Kit, FerroVer method. Range up to 3.00 mg/L.

Manganese, water, unfiltered, field, milligrams 

per liter

53570 mg/L 0.1 7439-96-5 8034 CL205 Manganese, wu, field, 

colorimetry, Hach test kit (NEWSC)

Field determination of manganese in unfiltered 

water with Hach Test Kit, Periodate Oxidation method. Range up to 20.00 mg/L.

Sulfide, water, unfiltered, 

field, milligrams per liter

99119 mg/L 0.001 18496-25-8 8131 MB002 Sulfide, field, by Hach methylene blue colorimetric 

method test kit

Sulfide, field, by Hach methylene blue colorimetric method test kit.
6 Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine Table 2. Constituents, U.S. Geological Survey National Water Information System parameter codes, minimum reporting limits, and method information for all water samples collected from domestic wells in Maine for analyses performed in the field, 2001–2 and 2006–7.—Continued [USGS, U.S. Geological Survey; MRL, minimum reporting limit; mg/L, milligram per liter; CASRN, Chemical Abstracts Service Registry Number; N, nitrogen; wu, water, unfiltered; NEWSC, New England Water Science Center; PO4, phosphate; °C, degree Celsius; NA, not applicable; μS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; ppm, part per million; % saturation, percent saturation; std units, standard units; gal/min, gallon per minute] Constituent USGS parameter code Units MRL (mg/L) CASRN1 Analytical method number reference2 USGS method code USGS method name Method description Field water-quality parameters Temperature, water, de- grees Celsius 00010 ° C NA NA NA THM01 Temperature, water, wu, field, thermistor, multiparameter sonde (NEWSC) Field determination of water temperature (° C) in unfiltered water with multiparameter sonde. Specific conductance, water, unfiltered, micro- siemens per centimeter at 25 degrees Celsius 00095 μS/cm at 25 °C NA NA NA SC001 Specific conductance, wu, field, electrometry, multipa- rameter sonde (NEWSC) Field determination of specific conductance in unfiltered water by electrometry with multi- parameter sonde. Dissolved oxygen, water, unfiltered, milligrams per liter 00300 mg/L 0.01 7782-44-7 NA LUMIN Dissolved oxygen, wu, field, luminescence sensor, multi- parameter sonde (NEWSC) Field determination of dissolved oxygen in un- filtered water by luminescence-based sensor with multiparameter sonde. Dissolved oxygen, water, unfiltered, milligrams per liter 00300 ppm 0.01 7782-44-7 NA RHODA Dissolved oxygen, wu, field, CHEMetrics 0–1 ppm kit (NEWSC) Field determination of dissolved oxygen in unfiltered water with CHEMetrics indigo carmine test kit, 0–1 ppm (mg/L). Dissolved oxygen, water, unfiltered, percent of saturation 00301 % satura- tion 0.1 7782-44-7 NA CAL35 Dissolved oxygen solubil- ity, barometric pressure, temperature, calculation, multiparameter sonde (NEWSC) Dissolved oxygen solubility in natural waters, calculation, multiparameter sonde. pH, water, unfiltered, field, standard units 00400 std units NA NA NA PROBE pH, wu, field, electrometry, multiparameter sonde (NEWSC) Field determination of pH in unfiltered water by electrometry with multiparameter sonde. Flow rate, instantaneous, 

gallons per minute

00059 gal/min NA NA NA G0009 Instantaneous flow rate, gallons per minute Field measured flow rate; timed measurement of volume.

1This report contains CAS Registry Numbers, which is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client Services.2Hach DR/2010 Spectrophotometer Procedures Manual, Hach Company (2000).
Methods of Data Collection 7

Table 3. Constituents, field parameters, arsenic speciation, and measuring entities for water samples collected from domestic wells in 

Maine, 2001–2 and 2006–7.

[USGS, U.S. Geological Survey; Maine HETL, Maine Department of Human Services Health and Environmental Testing Laboratory, Augusta, Maine; 

Underwriters Laboratories, Underwriters Laboratories Inc., South Bend, Indiana; NWQL, National Water Quality Laboratory, Denver, Colorado; DO, dissolved 

oxygen]

Constituent

USGS

parameter 

code

Laboratory or measuring entity

Maine HETL 

2001–2; 

2006–7

Underwriters 

Laboratories 

2006–7

USGSNWQL 

2001–2

USGS field 

measurements 

2001–2; 2006–7

Analytical determinations

Alkalinity 29803 X

Arsenic, total (unfiltered) 01002 X X X

Arsenic, dissolved (filtered) 01000 X

Fecal coliform 31616 X

Fluoride 00951 X

Iron, total 74010/99138 X X

Iron, ferrous (Fe II) 99128 X

Iron, ferric (Fe III) 51279 X

Lead 52298 X

Manganese 71883/53570 X X

Nitrate 00630/99124 X X

Nitrite 00615 X

pH (lab) 00403 X

Phosphate 99126 X

Sodium 52290 X

Sulfate 00946/99127 X X

Sulfide 99119 X

Total hardness 00909 X

Turbidity 82079 X

Uranium 63032 X

Field parameters

Dissolved oxygen 00300 X

Percent DO saturation 00301 X

pH (field) 00400 X

Specific conductance 00095 X

Temperature 00010 X

Arsenic speciation—field preparation

Total arsenic, raw well water X

Filtered arsenic, raw well water X

Arsenite [As(III)], raw well water; field ion exchange X

Arsenate [As(V)], raw well water; field ion exchange X

Filtered arsenic, well water, post-household filtration system X

Arsenite [As(III)], well water, post-household filtration system X
8 Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine

results for many of the same constituents, and to help inform 

the evaluation of the water treatment system performance in 

both studies.

POE and POU samples were collected for laboratory 

chemical analysis by following standard USGS protocols 

(U.S. Geological Survey, variously dated) and that of the 

Underwriters Laboratories Inc. (UL) DrinkWell well-water 

testing system. Once stable readings for temperature, specific conductance, and pH were achieved (0.25–0.75 hour), 

POE samples were collected. Source water for POU samples 

(kitchen faucet) was run continuously for approximately 

20 minutes prior to sample collection. The faucet aerator on 

the POU faucet was removed to minimize sample aeration. 

Faucets were disinfected with alcohol (isopropanol) wipes 

prior to sample collection. Bottle types and preservatives 

varied depending on the analysis to be performed. A complete 

list of constituents and minimum reporting limits is shown in 

table 1. All samples collected for analysis at UL were chilled 

to 4 degrees Celsius and shipped overnight on the day of collection. Samples were analyzed within appropriate, analytespecific holding times, according to the laboratories’ standard 

operating procedures. Published arsenic results are labeled as 

either “pre-household filtration” (POE) or “post-household 

filtration” (POU) samples (Culbertson and others, 2020).

Point-of-Entry and Point-of-Use Sample 

Collection for Laboratory Arsenic and Arsenic 

Speciation (Valence) Analysis

Household well-water samples for unfiltered arsenic, 

filtered arsenic (0.45-μm filter), and filtered As(III), and 

As(V) were collected at the POE and processed onsite prior to 

laboratory analysis. Laboratory analyses of arsenic, for both 

the 2001–2 and 2006–7 sampling periods, were performed by 

the Health and Environmental Testing Laboratory (HETL) of 

the Maine Department of Human Services5 in Augusta, Maine, 

and are published in Culbertson and others (2020). A subset 

of sample replicates (paired samples) were collected during 

the 2001–2 sampling period and analyzed by both the HETL 

and the USGS National Water Quality Laboratory (NWQL). 

Replicate results are identified as such in Culbertson and others (2020) by the “SampleType” field. In both sampling periods, the effectiveness of household water-treatment systems 

in removing arsenic was assessed by comparing POU samples 

(post-arsenic treatment system, collected at the kitchen faucet) 

to raw, untreated POE samples. Throughout the 2006–7 sampling period, replicate (paired) samples were collected for preand post-arsenic treatment system assessment and analyzed by 

both UL and HETL. During preliminary stages of the 2006–7 

sampling period, post-household treatment system (POU) 

samples were analyzed for filtered arsenic as well as As(III); 

however, there was concern that any As(III) present could be 

oxidized by interaction with the treatment system and thus be 

5Since July 2004, the Maine Department of Health and Human Services.

reported as As(V). Consequently, the sample collection protocol was modified mid-study, whereby, an additional replicate 

sample for As(III) determination on the raw (POE) well water 

was collected. Thereafter, instead of two sample replicates, 

As(III) determinations on raw POE well water were performed 

in triplicate. All samples for As(III) determinations on raw 

water were collected in triplicate during the 2001–2 sample 

period. Except where noted, the only arsenic determination on 

post-household filtration (POU) water was for filtered arsenic.

Arsenic Sample Preparation and Preservation

Sample preparation for arsenic analysis included acidification to pH <2 (Ultrex, ultra-high-purity nitric acid [HNO3], 

J.T. Baker Chemical Company, Phillipsburg, N.J.) for filtered 

arsenic sample analysis, and filtration through 0.45 μm nylon 

syringe filters, followed by acidification (5 percent [volume 

per volume] sulfuric acid [0.05 percent final H2SO4], Baker 

Instra-Analyzed, J.T. Baker Chemical Company) for filtered 

arsenic sample analysis and arsenic speciation (valence) analysis. Samples for As(III) and As(V) analysis were prepared 

onsite by eluting aliquots of the filtered/acidified samples 

through anion-exchange chromatography columns according to the method described by Ficklin (1983). Once aliquots 

for arsenic valence analysis were collected, the samples for 

filtered arsenic analysis were further acidified to pH <2 with 

HNO3 (Ultrex). This step was necessary to prevent HNO3

damage to the anion-exchange resin. The H2SO4 step was 

necessary to adjust the pH of the source water to approximately pH 4. At this pH, the anion-exchange columns retain 

the negatively charged As(V) species while allowing the 

neutral As(III) species to pass through in the filtrate (Ficklin, 

1983; Edwards and others, 1998; Wilkie and Hering, 1998). 

The filtrates were collected and further acidified to pH <2 with 

HNO3. Any arsenic measured in these samples is interpreted 

to be As(III) (table 3). As(V) was determined as the difference 

between filtered arsenic and As(III). Total particulate arsenic was determined as the difference between unfiltered and 

filtered arsenic samples.

Arsenic analyses were performed by three laboratories: 

(1) the Maine Department of Human Services HETL, Augusta, 

Maine, (2) UL, South Bend, Ind., and (3) the USGS NWQL, 

Denver, Colorado (table 3). Interlaboratory comparisons are 

displayed in figures 2 and 3 and are available in the published 

data (Culbertson and others, 2020).

Preparation of Field Anion-Exchange 

Chromatography Columns for Arsenic 

Speciation Analysis

Anion-exchange chromatography columns for the 

separation of As(III) and As(V) in the field were prepared in 

the laboratory prior to well-water sample collection. AG 1 

anion-exchange resin (50–100 mesh; Bio-Rad Laboratories, 
Quality Assessment of Laboratory Arsenic Analysis 9

1,000

100

10

1

Maine Health and Environmental

Testing Laboratory

Underwriters

Laboratory

Total arsenic concentrations, in micrograms per liter

EXPLANATION

Maximum value

3rd quartile

1st quartile

Median

Minimum value

Figure 2. Distribution of unfiltered arsenic concentrations in 

paired samples analyzed by the Maine Department of Human 

Services Health and Environmental Testing Laboratory (HETL) 

and Underwriters Laboratories Inc. (UL), 2006–7. Modified from 

Nielsen and others (2010).

0 100 200 300 400 500

Total arsenic concentration, in micrograms per liter, analyzed by the

Maine Health and Environmental Testing Laboratory 

0

100

200

300

400

500

Total arsenic concentration, in micrograms per liter,

analyzed by Underwriters Laboratory

R2 = 0.9838

Figure 3. Arsenic 

concentrations in paired 

samples analyzed by the Maine 

Department of Human Services 

Health and Environmental 

Testing Laboratory and 

Underwriters Laboratories Inc., 

2006–7. Modified from Nielsen 

and others (2010).

Hercules, Calif.) was obtained in the chloride form and converted to the acetate form prior to column packing (Wilkie and 

Hering, 1998). Poly-Prep 0.8 x 4-centimeter polypropylene 

chromatography columns (Bio-Rad Laboratories, Hercules, 

Calif.) were slurry-vibra-packed with approximately 2 milliliters of the converted anion-exchange resin and excess 

deionized water to keep the resin moist (vibra-packing of the 

resin slurry was used to eliminate channeling in the resin bed). 

Columns were capped and refrigerated until use in the field. 

The anion-exchange columns were prepared in batches of 

100; column efficiency tests were performed on each batch. 

Representative anion-exchange column efficiencies are shown 

in tables 4 and 5.

Quality Assessment of Laboratory 

Arsenic Analysis

Arsenic in all samples was determined by inductively 

coupled plasma-mass spectrometry (EPA Method 200.8; 

U.S. Environmental Protection Agency, 1994) by the HETL 

(table 1). As a QA check of samples analyzed by the HETL, 

replicate samples, collected during 2001–2, were analyzed 

for unfiltered arsenic by an alternate method: USGS Method 

GF096: “Arsenic Determination by Hydride Generation/

Atomic Absorption Spectrometry” by the USGS NWQL 

(table 1).
10 Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine

Table 4. Representative efficiency of anion-exchange 

chromatography resin for the field separation of As(III) and As(V) 

for single arsenic species recovery.

[As, arsenic; μg/L, microgram per liter As(III), arsenic-3 or arsenite; As(V), 

arsenic-5 or arsenate]

Replicate number As added 

(μg/L)

As recoverable 

(μg/L)

As(III)

Replicate 1 62 61

Replicate 2 62 61

Replicate 3 62 57

As(V)

Replicate 1 67 <0.5

Replicate 2 67 <0.5

Replicate 3 67 <0.5

Table 5. Representative efficiency of anion-exchange 

chromatography resin for the field separation of As(III) and As(V) 

for As(III)+As(V) mix recovery.

[As, arsenic; As(III), arsenic-3 or arsenite; μg/L, microgram per liter; As(V), 

arsenic-5 or arsenate]

Replicate number As(III) added 

(μg/L)

As(V) added 

(μg/L)

As recoverable 

(μg/L)

Replicate 1 33 34 31

Replicate 2 33 34 32

An assessment of the HETL and UL arsenic analyses 

was derived from a 2006–7 comparison of arsenic determinations reported by each laboratory for replicate (paired) 

samples. Sixty-four samples from wells with concentrations 

of arsenic ranging from 5 to 420 micrograms per liter (μg/L) 

were replicated (sampled at the same time and from the same 

source, preserved in the same way, and analyzed by using EPA 

Method 200.8). The results of the analyses for unfiltered arsenic from the two laboratories were compared to assure quality 

in the analytical process (figs. 2 and 3; Nielsen and others, 

2010; Culbertson and others, 2020).

In general, the average difference in concentration for the 

64 sample pairs analyzed by HETL and UL, expressed as the 

absolute value of the relative percent difference between the 

samples, was about 7.6 percent (|[HETL−UL]/([HETL+UL]/2) 

|*100). A comparison of concentrations for the paired samples 

(fig. 3) shows that, for the most part, this difference is primarily at the upper end of the range in concentrations of arsenic 

(with one exception at the lower end of the range). The range 

in relative percent difference is 0 to 105 percent, although only 

two samples have a relative percent difference greater than 

16.7 percent. According to a one-way analysis of variance of 

the datasets, the concentration means are not significantly different at the p=0.05 level (Nielsen and others, 2010).

References Cited

American Public Health Association, 1998, Standard 

methods for the examination of water and wastewater 

(20th ed.): Washington, D.C., American Public Health 

Association, American Water Works Association, and Water 

Environment Federation, 1,325 p.

Ayotte, J.D., Montgomery, D.L., Flanagan, S.M., and 

Robinson, K.W., 2003, Arsenic in groundwater in eastern 

New England—Occurrence, controls, and human health 

implications: Environmental Science & Technology, v. 37, 

no. 10, p. 2075–2083.

Ayotte, J.D., Nielsen, M.G., Robinson, G.R., and Moore, R.B., 

1999, Relation of arsenic, iron, and manganese in ground 

water to aquifer type, bedrock lithogeochemistry, and land 

use in the New England Coastal Basins Study Unit: U.S. 

Geological Survey Water-Resources Investigations Report 

99–4162, 61 p.

Ayotte, J.D., Nolan, B.T., Nuckols, J.R., Cantor, K.P., 

Robinson, G.R., Jr., Baris, D., Hayes, L., Karagas, M.R., 

Bress, W., Silverman, D.T., and Lubin, J.H., 2006, 

Modeling the probability of arsenic in groundwater in New 

England as a tool for exposure assessment: Environmental 

Science & Technology, v. 40, no. 11, p. 3578–3585.

Culbertson, C.W., Caldwell, J.M., Schalk, L.F., and Medalie, 

L., 2020, Arsenic datasets and other physical and chemical 

measurements for selected domestic well-water supplies in 

Maine—2001–2 and 2006–7: U.S. Geological Survey data 

release, https://doi.org/10.5066/P9X5HVDF.

Cullen, W.R., and Reimer, K.J., 1989, Arsenic speciation in the 

environment: Chemical Reviews, v. 89, no. 4, p. 713–764.

DeSimone, L.A., Hamilton, P.A., and Gilliom, R.J., 2009, 

Quality of water from domestic wells in principal aquifers 

of the United States, 1991–2004—Overview of major findings: U.S. Geological Survey Circular 1332, 48 p.

Edwards, M., Patel, S., McNeill, L., Chen, H., Frey, M., 

Eaton, A.D., Antweiler, R.C., and Taylor, H.E., 1998, 

Considerations in As analysis and speciation: Journal 

American Water Works Association, v. 90, no. 3, 

p. 103–113.

Ficklin, W.H., 1983, Separation of arsenic(III) and arsenic(V) 

in ground waters by ion-exchange: Talanta, v. 30, no. 5, 

p. 371–373.

Flanagan, S.M., Ayotte, J.D., and Robinson, G.R., Jr., 

2012, Quality of water from crystalline rock aquifers in 

New England, New Jersey, and New York, 1995–2007 

(ver. 1.1, April 2018): U.S. Geological Survey Scientific 

Investigations Report 2011–5220, 104 p., accessed 

October 29, 2019, at https://doi.org/10.3133/sir20115220.
References Cited 11

Focazio, M.J., Welch, A.H., Watkins, S.A., Helsel, D.R., and 

Horn, M.A., 2000, A retrospective analysis on the occurrence of arsenic in ground-water resources of the United 

States and limitations in drinking-water-supply characterizations: U.S. Geological Survey Water-Resources 

Investigations Report 99–4279, 21 p.

Fravel, H.G., Jr., and Lindsey, K., 2014, Understanding 

salt passage vs. salt rejection in reverse osmosis systems: American Membrane Technology Association 

blog, August 29, 2014, accessed August 2017 at 

https://www.amtaorg.com/understanding-salt-passage-vssalt-rejection-in-reverse-osmosis-systems.

Hach Company, 2000, Procedures manual, DR2010/DR2400 

Spectrophotometer (7th ed., October 2000): Loveland, 

Colo., Hach Company, 872 p.

Korte, N.E., and Fernando, Q., 1991, A review of arsenic (III) 

in groundwater: Critical Reviews in Environmental Science 

and Technology, v. 21, no. 1, p. 1–39.

Lipfert, G., Reeve, A.S., Sidle, W.C., and Marvinney, R.G., 

2006, Geochemical patterns of arsenic-enriched ground 

water in fractured crystalline bedrock, Northport, Maine, 

USA: Applied Geochemistry, v. 21, no. 3, p. 528–545.

Marvinney, R.G., Loiselle, M.C., Hopeck, J.T., Braley, D., and 

Krueger, J.A., 1994, Arsenic in Maine ground water—An 

example from Buxton, Maine, in Proceedings of the 1994 

Focus Conference on Eastern Regional Ground Water 

Issues, Burlington, Vt., October 3–5: National Ground 

Water Association, p. 701–715.

Marvinney, R.G., Loiselle, M.C., Hopeck, J.T., Braley, D., and 

Krueger, J.A., 1995, Arsenic in Maine groundwater—An 

example from Buxton, Maine [abs.]: Geological Society of 

America Abstracts with Programs, v. 27, p. 67.

National Research Council, 1999, Arsenic in drinking water: 

Washington, D.C., National Academy Press, 330 p.

National Research Council, 2001, Arsenic in drinking 

water—2001 update: Washington, D.C., National Academy 

Press, 244 p.

Nielsen, M.G., Lombard, P.J., and Schalk, L.F., 2010, 

Assessment of arsenic concentrations in domestic well 

water, by town, in Maine, 2005–09: U.S. Geological Survey 

Scientific Investigations Report 2010–5199, 68 p. [Also 

available at https://doi.org/10.3133/sir20105199.]

Peters, S.C., Blum, J.D., Klaue, B., and Karagas, M.R., 

1999, Arsenic occurrence in New Hampshire drinking 

water: Environmental Science & Technology, v. 33, no. 9, 

p. 1328–1333.

Ryker, S.J., 2001, Mapping arsenic in ground water: Geotimes, 

v. 46, no. 11, p. 34–36.

Shapiro, S.S., and Francia, R.S., 1972, An approximate analysis of variance test for normality: Journal of the American 

Statistical Association, v. 67, no. 337, p. 215–216.

Smedley, P.L., and Kinniburgh, D.G., 2002, A review of 

the source, behavior and distribution of arsenic in natural 

waters: Applied Geochemistry, v. 17, no. 5, p. 517–568.

U.S. Environmental Protection Agency, 1994, Method 200.8—

Determination of trace elements in waters and wastes by 

inductively coupled plasma-mass spectrometry (rev. 5.4): 

U.S. Environmental Protection Agency method, 57 p.

U.S. Environmental Protection Agency, 2001, National primary drinking water regulations—Arsenic and clarifications 

to compliance and new source contaminants monitoring 

[final rule]: Federal Register, v. 66, no. 14, p. 6975–7066.

U.S. Geological Survey, 2019, USGS water data for the 

Nation: U.S. Geological Survey National Water Information 

System database, accessed May 14, 2019, at https://doi.org/

10.5066/F7P55KJN.

U.S. Geological Survey, [variously dated], National field manual for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A10, accessed April 4, 2017, at 

https://pubs.water.usgs.gov/twri9A.

Welch, A.H., Helsel, D.R., Focazio, M.J., and Watkins, S.A., 

1999, Arsenic in ground water supplies of the United States, 

in Chappell, W.R., Abernathy, C.O., and Calderon, R.L., 

eds., Arsenic exposure and health effects: Burlington, Mass., 

Elsevier, p. 9–17.

Welch, A.H., Westjohn, D.B., Helsel, D.R., and Wanty, R.B., 

2000, Arsenic in ground water of the United States—

Occurrence and geochemistry: Ground Water, v. 38, no. 4, 

p. 589–604.

Wilkie, J.A., and Hering, J.G., 1998, Rapid oxidation of geothermal arsenic(III) in streamwaters of the Eastern Sierra 

Nevada: Environmental Science & Technology, v. 32, no. 5, 

p. 657–662.

Yang, Q., Jung, H.B., Culbertson, C.W., Marvinney, R.G., 

Loiselle, M.C., Locke, D.B., Cheek, H., Thibodeau, H., 

and Zheng, Y., 2009, Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in 

greater Augusta, Maine, USA: Environmental Science & 

Technology, v. 43, no. 8, p. 2714–2719.

Zheng, Y., and Ayotte, J.D., 2015, At the crossroads—Hazard 

assessment and reduction of health risks from arsenic in 

private well waters of the northeastern United States and 

Atlantic Canada: Science of the Total Environment, v. 505, 

p. 1237–1247.

For more information about this report, contact:

Director, New England Water Science Center

U.S. Geological Survey 

10 Bearfoot Road 

Northborough, MA 01532

dc_nweng@usgs.gov

or visit our website at

https://www.usgs.gov/centers/new-england-water

Publishing support provided by the

Pembroke and Rolla Publishing Service Centers
Culbertson and others—Methods of Collection and Quality Assessment of Arsenic Data in Well-Water Supplies in Maine—Data Series 1125

ISSN 2327-638X (online)

https://doi.org/10.3133/ds1125