United States

Environmental Protection

Agency

EPA-600/R-04-001

January 2004

Research and

Development

Prepared for

Prepared by

National Risk Management

Research Laboratory

Research Triangle Park, NC 27711

Measurement of Fugitive Emissions at

a Region I Landfill

U.S. Environmental Protection Agency Region I
EPA-600/R-04-001

January 2004

Measurement of Fugitive Emissions

at a Region I Landfill

by

Mark Modrak, Ram Hashmonay, and Robert Keagan

ARCADIS Geraghty & Miller

P.O. Box 13109

Research Triangle Park, NC 27709

Contract No. 68-C99-201, Work Assignment No. 4-003

EPA Project Officer: Susan A. Thorneloe

Air Pollution Prevention and Control Division

National Risk Management Research Laboratory

Research Triangle Park, NC 27711

Prepared for:

U.S. Environmental Protection Agency

Office of Research and Development

Washington, DC 20460
ii

Abstract

This report discusses a new measurement technology for characterizing emissions from large

area sources. This work was funded by EPA’s Monitoring and Measurement for the 21st Century

Initiative, or 21M2. The site selected for demonstrating this technology is a superfund landfill

that is being evaluated for recreational use. Data on methane and air toxics were needed to help

determine any increased risk to those using the site. Open-path Fourier transform infrared (OPFTIR) spectrometers were used to provide data on both background and surface emissions. The

technology provides concentration maps indicating the spatial variability and areas where

additional control may be needed. Horizontal scans to identify any hot spots and vertical scans

to determine the mass flux using a multiple-beam configuration were conducted. Optical remote

sensing-radial plume mapping provided concentration mapping of the site. These data will be

used to make decisions about potential recreational use of this site.
iii

Foreword

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting

the Nation’s land, air, and water 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, EPA’s research program is providing data and technical support for solving

environmental problems today and building a science knowledge base necessary to manage

our ecological resources wisely, understand how pollutants affect our health, and prevent or

reduce environmental risks in the future.

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for

investigation of technological and management approaches for preventing and reducing risks

from pollution that threaten human health and the environment. The focus of the Laboratory’s

research program is on methods and their cost-effectiveness for prevention and control of

pollution to air, land, water, and subsurface resources; protection of water quality in public

water systems; remediation of contaminated sites, sediments and ground water; prevention and

control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both

public and private sector partners to foster technologies that reduce the cost of compliance and

to anticipate emerging problems. NRMRL’s research provides solutions to environmental

problems by developing and promoting technologies that protect and improve the environment;

advancing scientific and engineering information to support regulatory and policy decisions;

and providing the technical support and information transfer to ensure implementation of

environmental regulations and strategies at the national, state, and community levels.

This publication has been produced as part of the Laboratory’s strategic long-term research

plan. It is published and made available by EPA’s Office of Research and Development to

assist the user community and to link researchers with their clients.

Lee A. Mulkey, Acting Director

National Risk Management Research Laboratory
iv

EPA REVIEW NOTICE

This report has been peer and administratively reviewed by the U.S. Environmental Protection

Agency and approved for publication. Mention of trade names or commercial products does not

constitute endorsement or recommendation for use.

This document is available to the public through the National Technical Information Service,

Springfield, Virginia 22161.
v

Contents

Section Page

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

EPA Review Notice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1

E1. Background/Site Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1

E1.1 Horizontal Radial Plume Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2

E1.2 Vertical Radial Plume Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2

E2. Results and Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2

E2.1 Horizontal Radial Plume Mapping Results . . . . . . . . . . . . . . . . . . . . . . . . . E-2

E2.2 Vertical Radial Plume Mapping Results . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3

E2.3 Hazardous Air Pollutants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-4

E3. Concluding Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-4

1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

1.2 Project Purpose and Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.2.1 Horizontal Radial Plume Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

1.2.2 Vertical Radial Plume Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1.3 Data Quality Objectives and Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

1.4 Schedule of Work Performed for Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

2.0 The Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 Area A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 Area B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.3 Area C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.4 Area D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.5 Area E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.6 Vertical Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.7 Meteorological Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Contents (continued)

Section Page

vi

2.8 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

3.0 Analytical Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.1 The Horizontal RPM Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 The Vertical RPM Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9

3.3 The Search for HAPs and Other Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

4.0 Quality Assurance/Quality Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 Assessment of DQI Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 Ethylene Tracer Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.3 Assessment of Number of Cycles Used for Moving Average . . . . . . . . . . . . . . . . 4-5

5.0 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

6.0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
vii

List of Figures

Figure Page

1-1 Map of the Somersworth Superfund Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1-2 Overhead View of an Example Horizontal RPM Configuration . . . . . . . . . . . . . . . . 1-4

1-3 Example of a Vertical RPM Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

2-1 Schematic of OP-FTIR RPM Measurement Configuration in Area A . . . . . . . . . . . . 2-2

2-2 Schematic of OP-FTIR RPM Measurement Configuration in Area B . . . . . . . . . . . . 2-3

2-3 Schematic of OP-FTIR RPM Measurement Configuration in Area C . . . . . . . . . . . . 2-4

2-4 Schematic of OP-FTIR RPM Measurement Configuration in Area D . . . . . . . . . . . . 2-5

2-5 Schematic of OP-FTIR RPM Measurement Configuration in Area E . . . . . . . . . . . . 2-6

3-1 Reconstructed Methane Concentrations (in ppmv) for Area A . . . . . . . . . . . . . . . . . 3-3

3-2 Reconstructed Methane Concentrations (in ppmv) for Area B . . . . . . . . . . . . . . . . . 3-4

3-3 Reconstructed Methane Concentrations (in ppmv) for Area C . . . . . . . . . . . . . . . . . 3-5

3-4 Reconstructed Methane Concentrations (in ppmv) for Area D . . . . . . . . . . . . . . . . . 3-6

3-5 Reconstructed Methane Concentrations (in ppmv) for Area E . . . . . . . . . . . . . . . . . . 3-7

3-6 The OP-FTIR RPM Methane Concentration Contours Overlaid on the

Map of the Somersworth Superfund Landfill. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

3-7 Vertical Scan RPM Measurement of the Vertical Methane Plume Profile . . . . . . . 3-10

3-8 Vertical Scan RPM Measurement of the Plume Profile from the Hot Spot

in the Valley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11

3-9 Two Beam RPM Measurement of the Vertical Methane Plume Profile on

the Western (Upwind) Side of the Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

4-1 OP-FTIR RPM Measurement of the Vertical Ethylene Tracer Plume Profile

on the Western (Upwind) Side of the Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4-2 Time Series of the Calculated Ethylene Flux from Tracer Release Experiment . . . . 4-5

4-3 Calculated Average Methane Flux and Average CCF from the Vertical

Scanning Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
viii

List of Tables

Table Page

E1. Range of Mean Methane Concentrations (in ppmv above global background)

Found in Each Survey Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3

1-1 DQI Goals for Critical Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

1-2 Detection Limits for Target Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

1-3 Schedule of Work Performed for Somersworth, NH Field Study . . . . . . . . . . . . . . . 1-9

2-1 Coordinates of Mirrors Used for Horizontal Scanning in Area A . . . . . . . . . . . . . . . 2-2

2-2 Coordinates of Mirrors Used for Horizontal Scanning in Area B . . . . . . . . . . . . . . . 2-3

2-3 Coordinates of Mirrors Used for Horizontal Scanning in Area C . . . . . . . . . . . . . . . 2-4

2-4 Coordinates of Mirrors Used for Horizontal Scanning in Area D . . . . . . . . . . . . . . . 2-6

2-5 Coordinates of Mirrors Used for Horizontal Scanning in Area E . . . . . . . . . . . . . . . 2-7

2-6 Coordinates of Mirrors Used for Vertical Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

3-1 Moving Average of Calculated Methane Flux, CCF, Wind Speed, and

Wind Direction for the Vertical Scanning Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3-2 Mean Methane Concentration (ppm) Determinations for Each Area . . . . . . . . . . . . . 3-7
E-1

Executive Summary

E1. Background/Site Information

A field study was performed during September and October, 2002 by ARCADIS and the U.S.

EPA to measure emissions from a superfund site in Somersworth, New Hampshire using an

open-path Fourier transform infrared (OP-FTIR) spectrometer. The study involved a technique,

developed through research funded by the EPA’s National Risk Management Research

Laboratory (NRMRL), which uses optical remote sensing-radial plume mapping (ORS-RPM)

to evaluate fugitive emissions.

The focus of the study was to characterize the emissions of methane and hazardous air pollutants

to assess landfill gas emissions from the site. The results will help determine whether active

controls will be required at the site. Concentrations of each compound were measured, and fluxes

(determined as the rate of flow per unit time, through a unit area) were calculated for each

compound detected. The site was divided into five survey areas for the field campaign. Detailed

maps of each survey area, and the survey configurations used in each area are included in the

report (see Figures 1-1, 2-1 through 2-5, and Tables 2-1 through 2-5).

The ORS-RPM techniques used in the present study were designed to characterize the emissions

of fugitive gases from area sources. Detailed spatial information is obtained from path-integrated

ORS measurements by the use of optimization algorithms. The method involved the use of an

innovative configuration of non-overlapping radial beam geometry to map the concentration

distributions in a plane. This method, radial plume mapping (RPM) (Hashmonay et al., 1999; Wu

et al., 1999; Hashmonay et al., 2002), can also be applied to a vertical plane downwind from an

area emission source to map the crosswind and vertical profiles of a plume. By incorporating

wind information, the flux through the plane is calculated, which leads to an emission rate of the

upwind area source.
E-2

E1.1 Horizontal Radial Plume Mapping

Horizontal scanning was performed in each of the five survey areas (see Figure 1-1) to search

for emission hot spots. Area A is located in the northwestern section of the landfill site; Area B

is located in the southeastern section of the site and includes a baseball field and basketball

courts; Area C is located in the northern section of the site and includes a baseball field; Area

D is located inside the chain-link fence of four tennis courts in the northeastern corner of the site;

Area E is located in the southwestern section of the site.

E1.2 Vertical Radial Plume Mapping

The vertical scan configuration was set up along the eastern boundary of the landfill site. This

location was chosen because it was optimum for determining a flux that would be representative

of the entire site under the given wind conditions. Figure 1-1 shows the location of the vertical

scanning configuration (the red line shows the location of the vertical plane, the red dot shows

the location of the OP-FTIR instrument, and the red square shows the location of the scissors

jack).

E2. Results and Discussions

An emissions contour map of the entire site and identification of three emission hot spots was

obtained from radial plume mapping. Vertical scanning enabled an estimate of the methane flux

from the entire site to be made.

E2.1 Horizontal Radial Plume Mapping Results

Horizontal scans were performed at each of the five survey areas. Figures 3-1 through 3-5 show

the average reconstructed methane concentrations in parts per million by volume for Areas A,

B, C, D, and E, respectively. The global methane background value of 1.75 ppm was subtracted

from each of the measurements taken. Table E1 shows a range of the area-averaged methane

concentrations measured in the five areas.
E-3

Table E1. Range of Mean Methane Concentrations (in ppmv above global background) Found

in Each Survey Area.

Area Range of Methane Concentrations

A 0.00 to 2.69

B 0.56 to 1.83

C 0.00 to 3.06

D 0.00 to 1.91

E 0.00 to 1.44

The measured surface methane concentrations ranged from the global background to 3.06 ppm.

The average methane concentration found was 1.03 ppm above global background.

Figure 3-6 shows the horizontal RPM-determined methane concentration contours overlaid on

a map of the Somersworth site. The determination of this concentration map is based solely on

the mean path-integrated measurements made in each survey area, and six auxiliary pathintegrated measurements made by an additional OP-FTIR instrument. Figure 3-6 shows three

methane hot spots, one in Area A (2.5 ppm above ambient), the second in the northwest corner

of Area C (3.0 ppm above ambient), and the third hot spot, the most intense at 6.5 ppm above

ambient, occurred in a small valley that lies north of the baseball field in Area B. This hot spot

was identified in sub-area B, so the additional OP-FTIR instrument was set up in the valley and

made six auxiliary measurements. These six measurements provided the detail showing the sharp

concentration gradients shown in Figure 3-6. Strong methane emissions were located near an

uncapped vent that was on the south slope of the valley adjacent to Area B.

E2.2 Vertical Radial Plume Mapping Results

Vertical scanning was done on the eastern boundary of the landfill to determine a methane flux

from the entire site, which was estimated to be 5.8 g/s. Additionally, the methane flux from the

hot spots (found during the surface scanning survey) was estimated by modifying the vertical

scanning configuration slightly. The estimated methane flux from the hot spots was 3.3 g/s,

which represents 57 percent of the emission from the entire landfill.
E-4

E2.3 Hazardous Air Pollutants

All data collected at the site, including data from horizontal and vertical scanning surveys, were

analyzed for any chemicals that are normally not found in the atmosphere, and this analysis did

not detect the presence of any of these chemicals at the site. This result is not surprising when

one notes that the maximum methane concentration measured at the landfill was 6.5 ppm, and

the minor constituents (neglecting aliphatic hydrocarbons) occur in landfills at levels that are

typically much less than 10-4 times the methane levels. Thus, minor constituents of the landfill

gases would be expected to be present at levels much lower than the detection limits of the OPFTIR instrument.

E3. Concluding Statements

The present study employed OP-FTIR sensors to determine chemical concentrations over the

entire area of the Superfund landfill in Somersworth, New Hampshire. The spatial information

was extracted from path-integrated OP-FTIR measurements using the RPM method. This

measurement-based technique provided a complete methane concentration-contour map of the

entire landfill and located methane emission hot spots (up to 6.5 ppm average above the global

background). In addition, the vertical scanning technique provided an estimate for the methane

emission from the entire landfill of 5.8 g/s. The methane emission rate from the hot spots in the

valley was determined to be 3.3 g/s, which is estimated to be 57 percent of the emission from the

entire landfill.
1-1

1.0

Introduction

1.1 Background

A superfund site in Somersworth, New Hampshire is being considered for re-use as a soccer

field/recreational area, and the state has requested a study to assess landfill gas emissions from

this site. The results will help determine whether active controls will be required. The focus of

the study was to characterize the emissions of methane and hazardous air pollutants. The study

employed optical remote sensing (ORS) techniques to determine chemical concentrations over

the entire area of the landfill. These techniques result in the generation of maps showing the

locations of high methane concentrations. In addition, concentration contour lines (isopleths)

were generated in the downwind vertical plane from which emission rates were determined.

There is much concern over the potential hazards of landfill gas emissions. Hazardous air

pollutants (HAPs) at sufficient levels can result in negative health effects due to both short-term

and long-term exposures. The predominant component of landfill emissions is methane, which

can result in fire and possible explosions at high levels. Methane is also a major greenhouse gas

that is implicated in global warming. Adding to these concerns is the annoyance of the odors due

to some of the minor components of landfill gases. EPA has promulgated regulations under the

Clean Air Act to address the public health and welfare concerns of landfill gas emissions. The

final rule and guidelines are contained in 40 CFR Parts 51, 52, and 60, Standards of Performance

for New Stationary Sources and Guidelines for Control of Existing Sources: Municipal Solid

Waste Landfills.

The Somersworth site was divided into five rectangular survey areas (A-E). Figure 1-1 presents

the overall layout of the Somersworth Superfund Site, detailing the geographic location of each

survey region. Additionally, the figure shows the location of the vertical scanning configuration,

which was used to gather data in order to calculate emission fluxes for the entire site.
1-2

Figure 1-1. Map of the Somersworth Superfund Landfill

1.2 Project Purpose and Description

The optical remote sensing (ORS) techniques used in the present study were designed to

characterize the emissions of fugitive gases from area sources. These techniques were developed

in research and development programs funded by the U.S. EPA’s National Risk Management

Research Laboratory (NRMRL). Detailed spatial information is obtained from path-integrated

ORS measurements by the use of optimization algorithms. The method involved the use of an

innovative configuration of non-overlapping radial beam geometry to map the concentration

distributions in a plane. This method, radial plume mapping (RPM) (Hashmonay et al., 1999; Wu

et al., 1999; Hashmonay et al., 2002), can also be applied to a vertical plane downwind from an

area emission source to map the crosswind and vertical profiles of a plume. By incorporating

wind information, the flux through the plane is calculated, which leads to an emission rate of the

upwind area source. An open-path Fourier transform infrared (OP-FTIR) sensor manufactured
1-3

by Unisearch Associates was chosen for the present study because of its capability of accurately

measuring a large number of chemical species that might occur in a plume.

The OP-FTIR spectrometer combined with the RPM method can be used for both fence-line

monitoring applications, and real-time, on-site, remediation monitoring and source characterization. An infrared light beam modulated by a Michelson interferometer is transmitted from a

single OP-FTIR instrument to a corner cube mirror target, which is usually set up at a range of

100 to 500 meters. The returned light signal is received by the single telescope and directed to

a detector. The light is absorbed by the molecules in the beam path as the light is transmitted to

the mirror and again as the light is reflected back to the analyzer. Thus, the round-trip path of the

light doubles the chemical absorption signal. The OP-FTIR measures the path-integrated concentration (PIC) along the beam path. One advantage of OP-FTIR monitoring is that the concentrations of a multitude of infrared absorbing gaseous chemicals can be detected and measured

simultaneously with high temporal resolution.

The chemical vapor emitted from an emission source forms a plume, which is carried by the

wind across the multiple infrared beams. The OP-FTIR PIC measurements can be used with

wind data to calculate the emission rate applying the RPM method for vertical planes. The beam

measurements avoid the uncertainties that are inherent in the traditional point measurements.

Meteorological and survey measurements were also made. A theodolite was used to make the

survey measurement of the azimuth and elevation angles and the radial distances to the mirrors

relative to the OP-FTIR sensor. ARCADIS had the following tasks:

• Collect OP-FTIR data in order to identify major emissions hot spots by generating

surface concentration maps in the horizontal plane

• Measure emission fluxes of detectable compounds downwind from major hot spots

• Collect any ancillary data

• Demonstrate the operation and function of the ORS technology

Additionally, U.S. EPA personnel operated a bistatic, non-scanning OP-FTIR (manufactured by

Midac) to determine ambient background concentrations, and these measurements were used to

correct the results of the ORS-RPM measurements for background contributions of the analytes.

The following sections provide general descriptions of the experiments performed at the site.
1-4

Figure 1-2. Overhead View of an Example Horizontal

RPM Configuration.

1.2.1 Horizontal Radial Plume Mapping

The RPM approach provides spatial information to path-integrated measurements by optical

remote sensing. This technique yields information on the two-dimensional distribution of the

concentrations in the form of chemical-concentration contour maps (Hashmonay et al., 1999; Wu

et al., 1999; Hashmonay et al., 2002). This form of output readily identifies chemical “hot spots,”

the location of high emissions. This method can be of great benefit for performing site surveys

prior to site remediation activities.

Horizontal radial scanning is usually performed with the ORS beams located as close to the

ground as practical. This enhances the ability to detect minor constituents emitted from the

ground, since the emitted plumes dilute significantly at higher levels above the ground. The

survey area is divided into a Cartesian grid of n times m rectangular cells. A mirror is located in

each of these cells and the OP-FTIR sensor scans to each of these mirrors, dwelling on each for

a set measurement time (30 seconds in the present study). The system scans to the mirrors in the

order of either increasing or decreasing

azimuth angle. The path-integrated

concentrations measured at each mirror

are averaged over a several scanning

cycles to produce time-averaged

concentration maps. Meteoro-logical

measurements are made concurrent with

the scanning measurements.

Figure 1-2 represents a typical horizontal

RPM configuration in which n = m = 3.

The lines represent the nine optical paths,

each terminating at a mirror (Hashmonay

et al., 2002). The solid square represents a

point source. The enclosed areas represent

the calculated plume, transported downwind by the wind. The numbers associated

with the isopleths are the determined

values for the concentrations. Horizontal

scanning was performed at the five survey

areas depicted in Figure 1-1.
1-5

Figure 1-3. Example of a Vertical RPM Configuration

1.2.2 Vertical Radial Plume Mapping

The vertical RPM method maps the concentrations in the vertical plane of the measurement. By

scanning in a vertical plane downwind from an area source, one can obtain plume concentration

profiles and calculate the plane-integrated concentrations. The flux is calculated by multiplying

the plane-integrated concentration by the wind speed component perpendicular to the vertical

plane. The flux leads directly to a determination of the emission rate (Hashmonay et al., 1998;

Hashmonay and Yost, 1999, Hashmonay et al., 2001). Thus, vertical scanning leads to a direct

measurement-based determination of the upwind source emission rate. At the Somersworth

Superfund Site, a vertical scanning measurement was performed at the eastern boundary (See

Figure 1-1).

Figure 1-3 shows a schematic of

the experimental setup used for

vertical scanning. Several mirrors

are placed in various locations on

a vertical plane in-line with the

scanning OP FTIR. Two of the

mirrors used in the configuration

are mounted on a scissors jack

(which is a piece of equipment

used to create a vertical platform

for mounting mirrors in the

configuration). The location of

the vertical plane is selected so

that it intersects the mean wind

direction as close to perpendicular as practical. Vertical scanning was performed on the downwind side of the Somersworth

Superfund site (the eastern border

in Figure 1-1), in order to estimate a methane flux for the entire

site.
1-6

1.3 Data Quality Objectives and Criteria

Data quality objectives (DQOs) are qualitative and quantitative statements developed using

EPA’s DQO Process (described in EPA QA/G-4, Guidance for the Data Quality Objectives

Process) that clarify study objectives, define the appropriate type of data, and specify tolerable

levels of potential decision errors that will be used as the basis for establishing the quality and

quantity of data needed to support decisions. DQOs define the performance criteria that limit the

probabilities of making decision errors by considering the purpose of collecting the data, defining

the appropriate type of data needed, and specifying tolerable probabilities of making decision

errors. For this project, the qualitative data quality objective is to provide data to support the state

in a risk assessment decision regarding this site.

Quantitative objectives are established for critical measurements using the data quality indicators

of accuracy, precision, and completeness. The acceptance criteria for these data quality indicators

are summarized in Table 1-1. Accuracy of measurement parameters is determined by comparing

a measured value to a known standard. Values must be within the listed tolerance to be

considered acceptable. Accuracy can also be measured by calculating the percent bias of a

measured value to that of a true value.

Precision is evaluated by making replicate measurements of the same parameter and then

assessing the variations of the results. Replicate measurements are expected to fall within the

tolerances shown in Table 1-1. Completeness is expressed as a percentage of the number of valid

measurements compared to the total number of measurements taken.

Table 1-1. DQI Goals for Critical Measurements

Measurement

Parameter

Sampling

Method(s) Analysis Method Accuracy Precision % Complete

Wind direction N/A Magnetic compass with

vane

±5° tolerance ±5° 90%

Wind speed N/A Heavy duty wind cup set ±0.8 m/s ±0.8 m/s 90%

Optical path length N/A Theodolite ±1 m ±1 m 100%

Mid-IR absorbance N/A FTIR ±10% ±10% abs 90%
1-7

ORS-RPM was used at each test site to evaluate fugitive emissions of the target compounds, if

detectable. Estimated minimum detection limits, by compound, are given in Table 1-2. It is

important to note that the values listed in Table 1-2 should be considered first step approximations, as the minimum detection limit is highly variable, and depends on many factors

including atmospheric conditions. Actual minimum detection levels are calculated in the

quantification software for all measurements taken. Minimum detection levels for each

absorbance spectrum are determined by calculating the root mean square (RMS) absorbance

noise in the spectral region of the target absorption feature. The minimum detection level is the

absorbance signal (of the target compound) that is five times the RMS noise level using a

reference spectrum acquired for a known concentration of the target compound.

Table 1-2. Detection Limits for Target Compounds

Compound Sampling/ Analytical

Method

Estimated Detection Limits

for 100 m One-Way Path,

1 min Average (ppmv)

Acetaldehyde FTIR 0.010

Acetone FTIR 0.024

Acrylonitrile FTIR 0.010

Benzene FTIR 0.040

Bromodichloromethane FTIR N/A

1,3-Butadiene FTIR 0.012

Butane FTIR 0.006

Carbon disulfide FTIR 0.028

Carbon tetrachloride FTIR 0.008

Carbonyl sulfide FTIR 0.006

Chlorobenzene FTIR 0.040

Chloroform FTIR 0.012

Chloromethane FTIR 0.012

1,4-Dichlorobenzene FTIR 0.012

Dichlorodifluoromethane FTIR 0.004

t-1,2-Dichloroethene FTIR N/A

Dichlorofluoromethane FTIR N/A

Dimethyl sulfide FTIR 0.018

Ethane FTIR 0.010

Ethanol FTIR 0.006

(Continued)
1-8

Table 1-2. Detection Limits for Target Compounds (continued)

Compound Sampling/ Analytical

Method

Estimated Detection Limits

for 100 m One-Way Path,

1 min Average (ppmv

Ethyl benzene FTIR 0.060

Ethyl chloride FTIR 0.004

Ethyl mercaptan FTIR N/A

Ethylene dibromide FTIR 0.006

Ethylene dichloride FTIR 0.030

Fluorotrichloromethane FTIR 0.004

Formaldehyde FTIR 0.006

Hexane FTIR 0.006

Hydrogen sulfide FTIR 6.0

Methane FTIR 0.024

Methyl chloroform FTIR 0.006

Methyl ethyl ketone FTIR 0.030

Methyl isobutyl ketone FTIR 0.040

Methyl mercaptan FTIR 0.060

Methylene chloride FTIR 0.014

Pentane FTIR 0.008

Propane FTIR 0.008

2-Propanol FTIR 0.006

Propylene dichloride FTIR 0.014

Tetrachloroethene FTIR 0.004

Toluene FTIR 0.040

Trichlorethylene FTIR 0.004

Vinyl chloride FTIR 0.010

Vinylidene chloride FTIR 0.014

Xylenes FTIR 0.030

1.4 Schedule of Work Performed for Project

One field measurement campaign was completed for this project. The field tests were performed

at the site during the end of September and beginning of October 2002 and were completed in

six days (three days at the site and three days traveling to and from the site). Table 1-3 provides

the schedule of work that was performed for each day of the project.
1-9

Table 1-3. Schedule of Work Performed for Somersworth, NH Field Study

Date Day of Week Detail of Work Performed

29 September 2002 Sunday Transport equipment to site

30 September 2002 Monday AM: Arrive at site

PM: Horizontal scanning of Area A (1.5 hours)

1 October 2002 Tuesday Horizontal scanning of Area B (2 hours), Area D (2

hours), and Area E (1 hour)

2 October 2002 Wednesday Horizontal scanning of Area B (2 hours) and vertical

scanning

3 October 2002 Thursday Transport equipment from site

4 October 2002 Friday Continue travel with equipment
2-1

2.0

The Measurements

The following subsections describe testing procedures done at each of the five survey areas,

which are designated as Area A through Area E. Each site was scanned horizontally to produce

concentration maps and to locate any hot spots. In addition, a vertical scanning survey was done

on the eastern side of the site. In each of these sections, a figure is included that details the

respective survey area. The location of the vertical scanning configuration is depicted in Figure

1-1. The square shows the location of the scissors jack, the dot shows the location of the

scanner/OP-FTIR instrument, and the dashed line indicates the position of the vertical plane.

2.1 Area A

Area A is located in the northwestern section of the landfill site. A line of large trees bounds the

survey area on the northern side (see Figure 1-1). Figure 2-1 shows a schematic of the horizontal

scanning configuration in Area A, which was divided into nine cells located as in Figure 2-1. The

scanning OP-FTIR sensor was setup in the southeast corner of Cell 1 in Area A. In the RPM

calculations, the boundaries of Cells 8 and 9 were altered to accommodate the tree-lined fence.

Table 2-1 lists the radial coordinates (relative to the OP-FTIR sensor) for each of the nine

mirrors.
2-2

Figure 2-1. Schematic of OP-FTIR RPM Measurement

Configuration in Area A (distances in meters).

Table 2-1. Coordinates of Mirrors Used for Horizontal Scanning in Area A.

Mirror Number Radial Distancea

(m)

Azimuth Angle from Northa

(deg)

1 58.9 315

2 64.1 334

3 103 2

4 121 304

5 130 320

6 125 332

7 191 296

8 179 307

9 170 313

a The radial distance and azimuth are relative to the position of the scanning

OP-FTIR.
2-3

Figure 2-2. Schematic of OP-FTIR RPM Measurement Configuration in Area B

(distances in meters).

2.2 Area B

Area B is located in the southeastern section of

the site, includes a baseball field and basketball

courts (see Figure 1-1), and is divided into 11

cells. Figure 2-2 is a schematic of the horizontal

scanning configuration in Area B and shows the

scanning OP-FTIR sensor was setup in the

northwest corner of the area. A second

monostatic (Unisearch) OP-FTIR system was

setup four meters from the scanning OP-FTIR

and made simultaneous measurements over two

paths to the mirror positions shown in Figure 2-2

for Cells 10 and 11. These measurements were

combined with those made to the nine cells by

the scanning system, resulting in an eleven-cell

RPM computation. Table 2-2 lists the radial

coordinates (relative to the OP-FTIR sensor) for

each of the nine mirrors.

Table 2-2. Coordinates of Mirrors Used for Horizontal Scanning in Area B.

Mirror Number Radial Distancea

(m)

Azimuth Angle from Northa

(deg)

1 51.4 119

2 63.4 147

3 89.8 156

4 90.4 100

5 105 117

6 114 132

7 128 93

8 139 104

9 149 116

10 219 97

11 219 119

a The radial distance and azimuth are relative to the position of the scanning

OP-FTIR.
2-4

Figure 2-3. Schematic of OP-FTIR RPM Measurement Configuration

in Area C (distances in meters).

2.3 Area C

Area C is located in the northern section of the site and includes a baseball field (see Figure 1-1).

Figure 2-3 is a schematic of the horizontal scanning configuration in Area C and shows the

scanning OP-FTIR sensor set up in the southeastern corner of the area. A fence cut across the

northwest corner of the area, resulting in locating some of the mirrors in less than optimum positions for the RPM algorithm. The radial coordinates are given for all nine mirrors in Table 2-3.

Table 2-3. Coordinates of Mirrors Used for Horizontal Scanning in Area C.

Mirror Number Radial Distancea

(m)

Azimuth Angle from Northa

(deg)

1 38.1 301

2 50.1 347

3 99.6 358

4 80.5 270

5 76.4 297

6 90.5 321

7 123 265

8 122 281

9 131 295

a The radial distance and azimuth are relative to the position of the scanning

OP-FTIR.
2-5

Figure 2-4. Schematic of OP-FTIR RPM Measurement Configuration in

Area D (distances in meters).

2.4 Area D

Area D is inside the chain-link fence of four tennis courts in the northeastern corner of the

landfill site (see Figure 1-1). Figure 2-4 is a schematic of the horizontal scanning configuration

in Area D and shows the setup in this area was different from the other areas in that the scanning

OP-FTIR sensor was located on the center of one side, instead of a corner, of the rectangular

area. The scanning sensor was located on the western side of Area D. Since Area D was confined

by a chain-link fence, it was much smaller than the other survey areas in the study. The

coordinates of the nine mirrors are listed in Table 2-4.

2.5 Area E

Area E is located in the southwestern section of the site (see Figure 1-1). Figure 2-5 shows a

schematic of the horizontal scanning configuration in Area E. The scanning OP-FTIR sensor was

setup in the northeastern corner of the designated area, and only four mirrors were used. The

coordinates of the four mirrors are listed in Table 2-5.
2-6

Figure 2-5. Schematic of OP-FTIR RPM Measurement Configuration in Area E

(distances in meters).

Table 2-4. Coordinates of Mirrors Used for Horizontal Scanning in Area D.

Mirror Number Radial Distancea

(m)

Azimuth Angle from Northa

(deg)

1 41.6 35

2 27.6 73

3 32.8 121

4 50.8 55

5 43.7 80

6 46.1 104

7 70.9 54

8 60.2 83

9 64.3 107

a The radial distance and azimuth are relative to the position of the scanning

OP-FTIR.
2-7

Table 2-5. Coordinates of Mirrors Used for Horizontal Scanning in Area E.

Mirror Number Radial Distancea

(m)

Azimuth Angle from Northa

(deg)

1 55.3 253

2 123 275

3 85.5 215

4 126 259

a The radial distance and azimuth are relative to the position of the scanning

OP-FTIR.

2.6 Vertical Scanning

The vertical scan configuration was set up along the eastern boundary of the landfill site. This

location was chosen because it was optimum under the given wind condition for determining a

methane flux that would be representative of the entire site. Figure 1-1 shows the location of the

vertical scanning configuration (the line shows the location of the vertical plane, the dot shows

the location of the scanner/OP-FTIR, and the square shows the location of the scissors jack). The

angular coordinates of the five mirrors are listed in Table 2-6.

Table 2-6. Coordinates of Mirrors Used for Vertical Scanning.

Mirror Number Radial Distancea

(m)

Elevation Angleb

(deg)

Azimuth Angle from Northa

(deg)

1 47.1 0 6

2 109 0 1

3 110 2 2

4 111 6 1

5 186 0 2

a The radial distance and azimuth are relative to the position of the scanning OP-FTIR. b Elevation angle shown is the angle from the horizontal axis to the mirror.

2.7 Meteorological Data

Meteorological data, including wind direction, wind speed, temperature, relative humidity, and

barometric pressure, were continuously collected during the sampling campaign with a
2-8

Climatronics weather station, model 101990-G1. The weather station collects real-time data from

its sensors and records time-stamped data to a data logger.

Wind direction and speed-sensing heads were used to measure the wind speed and direction at

height of 2 and 10 meters. The sensing heads for wind direction incorporate an automatic sensing

function that adjusts to true north, eliminating the errors associated with using a compass

heading. The sensing heads incorporate standard cup-type wind speed sensors.

2.8 Data Analysis

The OP-FTIR data were collected as interferograms and archived to CD-ROMs. The archived

interferograms were delivered to U.S. EPA personnel, who performed the conversions to absorbance spectra, which they analyzed to determine concentrations using Non-Lin (Spectrosoft)

software. This analysis was done after completion of the field campaign. The concentration

determinations were combined with the appropriate mirror locations, wind speed, and wind

direction, and algorithms developed in MatLab (Math-works) were then used to process the data

into horizontal plane concentration maps or vertical plane plume profiles. The fluxes were then

determined as the product of the determined area-integrated concentrations times the component

of the wind speed normal to the vertical measurement plane.

Copies of the interferogram data were also analyzed by ARCADIS. These spectra files were

searched for volatile organic compounds (VOCs) and ammonia concentrations, and EPA’s

methane-concentration determinations were verified.
3-1

3.0

Analytical Results and Discussion

The RPM algorithm is the tool that extracts the spatial information from the open-path

measurements to produce plume concentration maps and emission rates. The concordance

correlation factor (CCF) is used to represent the level of fit for the reconstruction in the pathintegrated domain (predicted vs. observed PIC) (Hashmonay et. al, 1999). The CCF is similar

to the Pearson correlation coefficient but is adjusted to account for shifts in location and scale.

Like the Pearson correlation, CCF values are bounded between -1 and 1, yet the CCF can never

exceed the absolute value of the Pearson correlation factor. For example, the CCF will be equal

to the Pearson correlation when the linear regression line intercepts the ordinate at 0, its slope

equals 1, and its absolute value will be lower than the Pearson correlation when these conditions

are not met. For the purposes of this report, the closer the CCF value is to 1, the better the fit for

the reconstruction in the path-integrated domain.

In reporting the average calculated fluxes, a moving average is used in Table 3-1 to show

temporal variability in the flux values. A moving average involves averaging flux values

calculated from several different consecutive cycles (a cycle is defined as data collected when

scanning one time through all the mirrors in the configuration). For example, a data set taken

from five cycles may be reported using a moving average of four, where values from cycle one

to four and two to five are averaged together to show any variability in the flux values.

3.1 The Horizontal RPM Results

Figures 3-1 through 3-5 present the average reconstructed methane concentrations for Areas A

through E, respectively. The contours give methane concentrations in ppmv, and the Xs show

the positions of the mirrors. The corresponding schematic diagrams of each area provide

directional indicators. Additionally, the calculated CCF for each reconstruction is provided.

Table 3-2 shows a list of the area-averaged concentrations of methane in all of the 42 cells

measured in the 5 areas. The table also includes five auxiliary measurements taken with the

Unisearch OP-FTIR within Cell 10 of Area B. These additional measurements were taken to
3-2

provide more detailed spatial information on the hot spot detected in this area. The listed

methane values are area averages for each of the cells as computed by the RPM algorithms. The

global methane background value of 1.75 ppm was subtracted from each of the area-averaged

values. The highest methane area-averaged concentrations were measured in Cell 8 (3.06 ppm)

in Area C and Cells 1 and 2 in Area A (2.64 ppm and 2.69 ppm, respectively, see Figures 2-1 and

2-3). The methane levels in these three cells were more than 2.5 ppm higher than the global

background level of 1.75 ppm. The area-averaged determinations for methane in the other 39

cells ranged from the ambient background level to 2.27 ppm above background. The mean value

of all 42 determinates was 1.03 ppm.

Table 3-1. Moving Average of Calculated Methane Flux, CCF, Wind Speed, and Wind

Direction for the Vertical Scanning Survey.

Cycles CCF Flux

(g/s)

Wind Speed

(m/s)

Wind Directiona

(deg)

1 to 4 0.999 4.4 2.23 7

2 to 5 0.998 5.2 2.32 3

3 to 6 0.998 5.5 2.27 0

4 to 7 0.993 5.1 2.42 0

5 to 8 0.992 6.0 2.78 1

6 to 9 0.985 6.5 2.73 3

7 to 10 0.985 7.1 2.78 1

8 to 11 0.994 8.7 2.72 356

9 to 12 0.994 7.7 2.41 345

10 to 13 0.997 6.4 2.29 340

11 to 14 0.999 5.1 2.11 333

Average 0.994 6.1 S S

St. Dev. of Mean 0.0051 1.28 S S

a Wind direction shown is the angle from a vector normal to the plane of the configuration.
3-3

Figure 3-1. Reconstructed Methane Concentrations (in ppmv) for Area A (distances in

meters).
3-4

Figure 3-2. Reconstructed Methane Concentrations (in ppmv) for Area B (distances in meters).
3-5

Figure 3-3. Reconstructed Methane Concentrations (in ppmv) for Area C

(distances in meters).
3-6

Figure 3-4. Reconstructed Methane Concentrations (in ppmv) for Area D (distances

in meters).
3-7

Figure 3-5. Reconstructed Methane Concentrations (in ppmv) for Area E (distances

in meters).

Table 3-2. Mean Methane Concentration (ppm) Determinations for Each Area.

Cell

Number Area A Area B Area B Auxiliary

Measurements Area C Area D Area E

1 2.6 1.3 1.5 1.6 1.1 1.1

2 2.7 0.65 0.00 0.95 1.3 0.15

3 1.2 1.3 1.7 0.77 1.3 1.4

4 0.00 1.6 6.4 2.3 0.72 0.00

5 0.00 0.56 5.8 1.4 0.85

6 0.00 0.75 0.79 1.8

7 0.62 1.8 0.00 1.9

8 0.33 0.68 3.1 1.5

9 0.00 0.92 0.00 1.3

10 1.1

11 0.31
3-8

Figure 3-6. The OP-FTIR RPM Methane Concentration Contours Overlaid on the Map of the

Somersworth Superfund Landfill.

Figure 3-6 shows RPM-determined methane concentration contours overlaid on a site map of

the Somersworth landfill. The dots indicate the OP-FTIR locations used to collect the data. The

determination of this concentration map is based solely on the mean path-integrated measurements in the five areas comprising a total of 42 cells and 5 auxiliary path-integrated measurements made by the Unisearch OP-FTIR in Area B. The methane concentration map shows three

hot spots, one in Area A (2.5 ppm above ambient), the second in the north west corner of Area

C (3.0 ppm above ambient), and the third hot spot, the most intense at 6.5 ppm above ambient,

occurred in the small valley north of the baseball field in Area B. Since this hot spot was

identified in Area B, the Unisearch OP-FTIR was setup in the valley and made path-integrated

measure-ments to five mirror positions in, and on, the north and south slopes of the valley.

Including the five path-integrated measurements from the Unisearch instrument in the RPM

calculation of provided the detail showing the sharp concentration gradients shown in Figure 3-6.

The Unisearch measurements located strong methane emissions from an uncapped vent

(probably from a hole dug for a utility pole that was never installed) located on the south slope

of the valley adjacent to the Area B ball field.
3-9

3.2 The Vertical RPM Results

Table 3-1 presents methane emission flux determinations from the vertical scanning survey. See

Figure 1-1 for the location of the vertical scanning survey at the site. The first column of this

table refers to a running average calculation from the several cycles. The second column shows

the calculated CCF. The third, fourth, and fifth columns show the calculated methane flux, the

average wind speed, and the wind direction, respectively, during the time the measurements were

taken.

Figure 1-3 shows the schematic of the vertical scanning configuration. The measurement was set

up on the eastern boundary that was on the downwind side of the landfill and located so that the

centerline of the methane plume emitted from the hot spots in the valley and from Areas C and

A would intersect the beam paths. The centerline of the plume was closer to the mirror tower

than to the OP-FTIR sensor, and some of the plume extended beyond the tower. This portion of

the plume was captured by the beam to mirror number 5, which was situated 186 meters from

the sensor.

The emission flux was determined for the vertical-plane area shown in Figure 3-7 (186 meters

horizontal and 23 meters vertical) by multiplying the area-integrated concentration by the

component of the wind speed normal to the vertical plane. This resulted in a flux value of 5.8

g/sec. This vertical plane captured most of the methane plume emitted from the landfill; thus,

the flux through this plane is approximately equal to the emission rate for the entire landfill.

The vertical scanning configuration shown in Figure 3-7 was situated just downwind of the

location of high methane emissions in the valley, which is referred to as the hot spot. However,

the vertical plane with the 186-meter horizontal distance extended sixty meters beyond the hotspot plume. The vertical scan measurements can also be used to determine the emission flux

from the hot spot by narrowing the RPM computation to the portion of the vertical plane through

which the hot spot plume passes, as shown in Figure 3-8. The RPM determined flux for this

modified plane, which extends to 140 meters from the OP-FTIR sensor, was 4.6 g/sec. This flux

also includes contributions from the areas of the landfill that are upwind of the hot spot. To

determine the net flux from the hot spot, a vertical plane configuration was set up immediately

upwind, just west of the hot spot and collected data simultaneously. This configuration, which

used two separate non-scanning OP-FTIR sensors, is shown in Figure 3-9. The flux through this

plane was determined as 1.3 g/sec. The net flux through the 140-meter by 25-meter plane is the

difference between the flux through the downwind plane and that of the upwind plane, 3.3 g/sec.
3-10

Figure 3-7. Vertical Scan RPM Measurement of the Vertical Methane Plume Profile (numbers

on the isopleths are methane concentrations above the global background).

Since the downwind plane contained the hot-spot plume, the mean emission rate from the hot

spot is estimated to be 3.3 g/sec, which represents 57 percent of the emission (5.8 g/sec) from

the entire landfill.
3-11

Figure 3-8. Vertical Scan RPM Measurement of the Plume Profile from the Hot Spot in the

Valley (numbers on the isopleths are methane concentrations above the global

background).
3-12

Figure 3-9. Two Beam RPM Measurement of the Vertical Methane Plume Profile on the

Western (Upwind) Side of the Landfill (numbers on the isopleths are the

methane concentrations above the global background).

3.3 The Search for HAPs and Other Chemicals

All regions of the spectra collected by both MIDAC and Unisearch Open-Path FTIRs were

carefully searched for absorption features due to any chemicals that are normally not in the

atmosphere. This search included all measurements on the 42 beams and from the vertical

measurements as well as the Unisearch measurements near the methane hot spot in the valley.

No absorption features were found. This result is not surprising, when one notes that the

maximum concentration of methane measured at the landfill was 6.5 ppm. The minor

constituents (neglecting the aliphatic hydrocarbons) occur at landfills at levels that are typically

much less than 10-4 times the methane levels. Thus we would expect the minor constituents of

the landfill gases to be lower than 650 pptv in the ground-level atmosphere, which are levels

considerably lower than the detection limits of the OP-FTIR systems.
4-1

4.0

Quality Assurance/Quality Control

In preparation for this project, a Category III Quality Assurance Project Plan (QAPP) was

prepared and approved prior to the field campaign. In addition, standard operating procedures

were in place during the survey.

4.1 Assessment of DQI Goals

The data quality objectives established for critical measurements using the data quality indicators

(DQIs) of accuracy, precision, and completeness are listed in Table 1-1 of this document.

However, the goal is to develop improved DQIs for the applied techniques used in this type of

research project.

Although calibration of the Climatronics heads did not occur prior to the field study, both

Climatronics heads were calibrated in March 2003 by the U.S. EPA/APPCD Metrology Lab (the

previous calibration of both heads was in November 1999). All functions were checked during

the March 2003 calibration, and the only adjustment made was an approximately 4° change to

wind direction for one of the Climatronics heads. As shown in Table 1-1, accuracy within 5%

is an acceptable range, and this variance will have very little bearing on the final flux estimate.

It should also be noted that the wind direction measurement is not as critical to the flux estimates

as the wind speed measurement. Additionally, checks for agreement of the wind speed and wind

direction measured from the two heads (2m and 10m) were done. While it is true that some

variability in the parameters measured at both levels should be expected, this is a good first-step

check for assessing the performance of the instruments.

It has been determined that the accuracy of the measured optical path-lengths (which are

collected using the theodolite), as stated in the QAPP and by the manufacturer’s specifications,

are not crucial to our method. However, calibration of the theodolite was done in the field during

May 2003. The optical path-length was checked by measuring a standard distance of 50 feet
4-2

(15.24 meters). The same distance was measured twice using the theodolite and yielded distances

of 15.43 and 15.39 meters. These results fall well within the acceptable accuracy range stated in

Table 1-1. The horizontal angle was checked by setting up two targets approximately 180° apart,

measuring the two horizontal angles between the targets, and calculating the sum, which should

be 360°. These angles were measured twice using the theodolite. The first test yielded a sum of

359°21’18”, and the second test yielded a sum of 359°59’55”. Both of these values fall well

within the acceptable accuracy range stated in Table 1-1.

As a QC check of the accuracy of the OP_FTIR, we have verified the measurement of the known

atmospheric background nitrous oxide concentration of around 320 ppbv from data taken with

the monostatic OP-FTIR. It should be noted that 320 ppbv is an average value, as the

atmospheric background value exhibits a slight seasonal variation. The data were taken from a

sample of the actual data collected during the current field campaign. The average nitrous oxide

concentration found was 337 ± 9.121 ppbv. This value falls within the accuracy goals stated in

Table 1-1.

Additionally, DQI procedures for proper operation, as described in EPA Compendium method

TO-16, and the OP-FTIR EPA Guidance Document were followed for this study. The development of DQI standards for this method is a future goal, and improved DQI standards will be

included in future QAPP documents written using this method.

4.2 Ethylene Tracer Release

To verify the accuracy of the method used to calculate emission flux, a tracer gas was released

during the vertical scanning survey. Ethylene was released through a soaker hose configuration

located directly west of the vertical scanning survey. The wind direction during the time of the

release was almost due west, which allowed the vertical configuration to capture the plume from

the tracer release. The soaker hoses were set up in an “H” configuration to simulate an area

source, and the approximate dimensions of the “H” configuration were 10 meters wide and 40

meters long on each side. Using a digital scale, the weight of the ethylene cylinder was recorded

prior to release of the gas and immediately after the release was completed. In addition, the

precise starting and ending time of the release was recorded in order to calculate the average

actual flux of ethylene. This flux value was then compared to the ethylene flux calculated from

the vertical scanning survey.
4-3

Figure 4-1. OP-FTIR RPM Measurement of the Vertical Ethylene Tracer Plume Profile on the

Western (Upwind) Side of the Landfill. These Determinations Were Made from the

Same OP-FTIR Measurements as the Methane Vertical Plume Profile (numbers on

the isopleths are the ethylene concentrations in ppm).

Figure 4-1 shows a schematic of the vertical scanning configuration used to simultaneously

measure the methane emissions and the ethylene tracer plume. The configuration is overlaid by

the ethylene plume profile in the form of concentration contours as determined by the RPM

algorithm. The emission flux through the vertical measurement plane, calculated from the area

integration of the concentration profile multiplied by the component of the wind speed normal

to the vertical plane, was determined as 0.98 g/sec. Since the measurement plane captured the

entire plume, the entire flux through the plane is the emission rate of ethylene.
4-4

Ethylene tracer gas was released for 75 minutes. During this period, the measured mass of the

ethylene cylinder was reduced by 4.59 kg. A loss of 4.59 kg over a 75-minute period indicates

an average flow rate of 1.02 g/sec. The measured emission rate indicates an ethylene mass

recovery of 96%.

The flux of the ethylene release determined by mass-loss agrees well with the average ethylene

flux calculated from the vertical scanning survey. Observed wind directions during the vertical

scanning survey were not highly variable, which is indicative of a stable atmosphere. Hashmonay

et al. [2001] found that fluxes calculated during stable environments underestimated the actual

flux by around 12%. The average ethylene flux calculated during the current experiment

underestimated the actual average ethylene flux by 3.9%.

The favorable results found were due to the orientation of the prevailing winds, with respect to

the vertical configuration. Table 3-2 shows that the observed wind direction was generally

perpendicular to the vertical configuration during the entire survey. This allowed the configuration to capture a large amount of the ethylene plume from the site. Another factor that

contributed to the favorable results found was the small variability in wind direction and speed

during the period of the survey, which indicates very stable atmospheric conditions. Flux calculations in unstable atmospheric conditions tend to underestimate down to 60% of the actual

fluxes (Hashmonay et al., 2001).

Figure 4-2 shows a time series of the calculated ethylene fluxes measured during the tracer

release study. It is apparent that the calculated flux decreases sharply with time. This was

expected, as the ethylene flow rate was decreased rapidly after the experiment began in order to

prevent the regulator on the cylinder from freezing. It is important to note that, despite the

fluctuation in the actual flow rate of the ethylene release, the experiment still yielded very

favorable results.
4-5

Figure 4-2. Time Series of the Calculated Ethylene Flux from Tracer Release Experiment

4.3 Assessment of Number of Cycles Used for Moving Average

A statistical analysis of the methane fluxes (measured from the vertical scanning configuration)

was done to investigate trends in methane concentrations, standard deviations, and the average

CCF when a different number of cycles is used for the moving average. The statistical analysis

suggests that a moving average of four cycles is sufficient to provide a valid emission flux.

Figure 4-3 shows the average methane flux and average CCF calculated using many different

numbers of cycles for the moving average. The figure shows that the average calculated methane

flux increases slightly as the number of cycles used for the moving average increases but begins

to level off after two cycles. Additionally, the figure shows that the standard deviations of

methane fluxes decreases after two cycles. The CCF plot shows a similar trend, with values

leveling off after four cycles, and standard deviations decreasing as well.
4-6

Figure 4-3. Calculated Average Methane Flux and Average CCF from the Vertical

Scanning Survey
5-1

5.0

Conclusion

The present study employed Open-path FTIR sensors to determine chemical concentrations over

the entire area of the Superfund landfill in Somersworth, New Hampshire. The spatial

information was extracted from the path-integrated open-path FTIR measurements using the

RPM method. This measurement-based technique provided a complete methane concentrationcontour map of the entire landfill and located areas of high methane emissions (up to 6.5 ppm

average methane concentration above the global background). In addition, the vertical scanning

technique provided an estimate for the methane emission of 5.8 g/sec from the entire landfill.

The methane emission rate from the hot spots in the valley was determined to be 3.3 g/sec, which

is 57 percent of the emission from the entire landfill. The vertical scanning technique was tested

for accuracy by using ethylene tracer release. The RPM determination of the ethylene emission

rate agreed with the actual release rate to within four percent.
6-1

6.0

References

Hashmonay, R.A., K. Wagoner, D.F. Natschke, D.B. Harris, and E.L. Thompson, Radial

Computed Tomography of Air Contaminants Using Optical Remote Sensing, presented at the

AWMA 95th Annual Conference and Exhibition, Baltimore, MD, June 23-27, 2002.

Hashmonay, R.A., D.F. Natschke, K. Wagoner, D.B. Harris, E.L. Thompson, and M.G. Yost,

Field Evaluation of a Method for Estimating Gaseous Fluxes from Area Sources Using OpenPath Fourier Transform Infrared, Environ. Sci. Technol., 35, 2309-2313, 2001.

Hashmonay, R.A., and M.G. Yost, Innovative Approach for Estimating Fugitive Gaseous Fluxes

Using Computed Tomography and Remote Optical Sensing Techniques, J. Air Waste Manage.

Assoc., 49, 966-972, 1999.

Hashmonay, R.A., M.G. Yost, D.B. Harris, and E.L. Thompson, Simulation Study for Gaseous

Fluxes from an Area Source Using Computed Tomography and Optical Remote Sensing,

presented at SPIE Conference on Environmental Monitoring and Remediation Technologies,

Boston, MA, Nov., 1998, in SPIE Vol. 3534, 405-410.

Hashmonay, R.A., M.G. Yost, and Chang-Fu Wu, Computed Tomography of Air Pollutants

Using Radial Scanning Path-Integrated Optical Remote Sensing, Atmospheric Environment, 33

(2), 267-274, 1999.

Wu, C-F., M.G. Yost, R.A., Hashmonay, D.Y. Park, Experimental Evaluation of a Radial Beam

Geometry for Mapping Air Pollutants Using Optical Remote Sensing and Computed

Tomography, Atmospheric Environment, 33 (28), 4709-4716, 1999.

Tsai, M.Y., M.G. Yost, C.F. Wu, R.A. Hashmonay, and T.V. Larson, Line Profile

Reconstruction: Validation and Comparison of Reconstruction Methods, Atmospheric

Environment, 35 (28), 4791-4799, 2001.
6-2

ARCADIS Geraghty & Miller

P.O. Box 13109

Research Triangle Park, NC 27709 68-C99-201, WA 4-003

TECHNICAL REPORT DATA

(Please read Instructions on the reverse before completing)

1. REPORT NO. 2. 3. RECIPIENT'S ACCESSION NO.

4. TITLE AND SUBTITLE 5. REPORT DATE

Measurement of Fugitive Emissions at a Region I Landfill January 2004

6. PERFORMING ORGANIZATION CODE

7. AUTHORS 8. PERFORMING ORGANIZATION REPORT NO.

M. Modrak, R. Hashmonay, and R. Keagan

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO.

11. CONTRACT/GRANT NO.

12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED

U. S. EPA, Office of Research and Development

Air Pollution Prevention and Control Division

Research Triangle Park, North Carolina 27711

Final: 01/01/02 to 08/19/03

14. SPONSORING AGENCY CODE

EPA/600/13

15. SUPPLEMENTARY NOTES

The EPA Project Officer is Susan A. Thorneloe, mail drop E305-02, phone (919) 541-2709

16. ABSTRACT

The report discusses a new measurement technology for characterizing emissions from large area

sources. The work was funded by EPA’s Monitoring and Measurement for the 21st Century Initiative, or

21M2. The site selected for demonstrating this technology is a superfund landfill that is being evaluated for

recreational use. Data on methane and air toxics were needed to help determine any increased risk to

those using the site. Open-path Fourier transform infrared (OP-FTIR) spectrometers were used to provide

data on both background and surface emissions. The technology provides concentration maps indicating

the spatial variability and areas where additional control may be needed. Horizontal scans to identify any

hot spots and vertical scans using a multiple-beam configuration to determine the mass flux were

conducted. Optical remote sensing-radial plume mapping provided concentration mapping of the site.

These data will be used to make decisions about potential recreational use of this site.

17. KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group

Aerosol Particles

Earth Fills (Landfill)

Organic Compounds

Methane

Pollution Control

Stationary Sources

14G

13C

17C

7C

18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (This Report) 21. NO. OF PAGES

Release to Public

 Unclassified 52

20. SECURITY CLASS (This Page) 22. PRICE

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