swansea ambient air monitoring station (sams) 1st quarter ... · 1st quarter py2018 air quality...

Swansea Ambient Air Monitoring Station (SAMS)

1st Quarter PY2018 Air Quality Data Report

Prepared for the Colorado Department of Transportation

and the City and County of Denver,

Department of Environmental Health

Airtech/Montrose Project No. 6203

Report ID: 6203-Q1 2018

January 11, 2018

City and County of Denver

Report ID: 6203-Q1 2018

Table of Contents

PROJECT OVERVIEW ............................................................................................................................... 1

Background ................................................................................................................................................. 1 Objectives .................................................................................................................................................... 1 Operational Staff and Contacts ................................................................................................................... 2 SAMS Site Description ................................................................................................................................ 3

Picture 1 – Location of SAMS in the Swansea Elementary School Parking Lot ..................................................... 3 Picture 2 – Interior of SAMS ................................................................................................................................... 3

SAMS Equipment ......................................................................................................................................... 4 Discussion of Results and Professional Judgment ...................................................................................... 4

POLLUTANT DATA COLLECTED .......................................................................................................... 7

Figure 1a – Monthly PM10 Data .................................................................................................................. 7 Figure 1b – Monthly PM10 Data .................................................................................................................. 8 Figure 1c – Monthly PM10 Data .................................................................................................................. 9 Figure 2a – Monthly PM2.5 Data ............................................................................................................... 10 Figure 2b – Monthly PM2.5 Data ............................................................................................................... 11 Figure 2c – Monthly PM2.5 Data ............................................................................................................... 12 Figure 3a – Monthly NO2 Data ................................................................................................................. 13 Figure 3b – Monthly NO2 Data ................................................................................................................. 14 Figure 3c – Monthly NO2 Data ................................................................................................................. 15 Figure 4a – Monthly CO Data .................................................................................................................. 16 Figure 4b – Monthly CO Data .................................................................................................................. 17 Figure 4c – Monthly CO Data ................................................................................................................... 18 Figure 5a – Monthly Black Carbon Data .................................................................................................. 19 Figure 5b – Monthly Black Carbon Data .................................................................................................. 20 Figure 5c – Monthly Black Carbon Data .................................................................................................. 21 Table 1a – Monthly Summary of VOC Data .............................................................................................. 22 Table 1b – Monthly Summary of VOC Data .............................................................................................. 23 Table 1c – Monthly Summary of VOC Data .............................................................................................. 24 Table 2 – Reporting and Quantification Limits for Selected VOC Compounds ........................................ 24

DATA QUALITY ASSURANCE/QUALITY CONTROL ....................................................................... 25

Quality Assurance/Quality Control ........................................................................................................... 25 NOX and CO Analyzers - Span Test ....................................................................................................................... 25 NOX and CO Analyzers - Precision Test ................................................................................................................ 26 PM2.5 / PM10 Analyzer ............................................................................................................................................ 27 Aethalometer .......................................................................................................................................................... 27 Wind Speed and Wind Direction ........................................................................................................................... 28 Gas Chromatograph ............................................................................................................................................... 28

SIGNATURE PAGE ................................................................................................................................... 34

APPENDIX

Quality Assurance Logs Calibration Certification Sheets Primary Flow Standard Certification Sheet


Report ID: 6203-Q1 2018 Page 1

Project Overview

Background

Colorado Department of Transportation (CDOT) and Denver Environmental Health

(DEH) entered into an agreement1 to monitor air quality at Swansea Elementary School in

three phases. Phase I will monitor air quality for one year prior to startup of a CDOT

construction project on Interstate 70 (I-70). Phase II will monitor air quality for three (3)

years during the I-70 expansion project; construction may last more than three years.

Phase III will monitor air quality for one year after I-70 construction and ground

disturbance activities are completed.

The monitoring aspect of Phase I began on April 1, 2017. The monitoring project scope

of work, which is an attachment to the agreement, defined the first quarter of a year as

beginning on September 1. Therefore, monitoring began in the third quarter of the 2017

project year (Q3 PY2017).

Objectives

Airtech Environmental Services Inc. (a Montrose Air Quality Services, LLC Company)

was contracted by the City and County of Denver to start up and operate the Swansea Air

Monitoring Station (SAMS). The SAMS is located at the Swansea Elementary School;

faculty parking lot; South East Corner; at 4650 Columbine Street, Denver, Colorado.

This report represents the first quarterly report for Phase I. The station monitored the

following parameters during Q1 PY2018:

• C6 (6-Carbon) through C12 (12-Carbon) Volatile Organic Compounds (VOC)

• Black Carbon

• Carbon Monoxide (CO)

• Particulate Matter less than 10 Microns (PM10)

• Particulate Matter less than 2.5 Microns (PM2.5)

• Meteorological Measurements

• Nitrogen Oxides (NOx)

The monitoring is being performed to meet the requirements of the agreement between

CDOT and DEH. Additionally, the regulations and specifications set forth by the

Colorado Department of Public Health and Environment (CDPHE) and the United States

Environmental Protection Agency (USEPA), are being followed as applicable.

1 The agreement between CDOT and DEH became effective on August 12, 2016 and can be obtained from

CDOT by referencing routing number 17-HTD-ZH-00167.



Operational Staff and Contacts

The contact information for each of the principal parties is summarized in the table

below:

Rebecca White Michael Ogletree

Colorado Department of Transportation City and County of Denver

5640 E. Atlantic Place 200 W 14th Ave

Denver, CO 80222 Denver, CO 80204

Phone: (303) 512-5901 Phone: (720) 865-2891

E-mail: [email protected] E-mail: [email protected]

Patrick Clark, PE, QSTI Dr. Larry Anderson

Montrose Air Quality Services, LLC University of Colorado Denver

990 W. 43rd Ave. 7120 Routt Street

Denver, CO 80211 Arvada, CO 80004

Phone: (303) 670-0530 Phone: (303) 664-0757

E-mail: [email protected] E-mail: [email protected]

Austin Heitmann

Montrose Air Quality Services, LLC

990 W. 43rd Ave.

Denver, CO 80211

Phone: (303) 670-0530

E-mail: [email protected]

tel:(303)%20512-5901

mailto:[email protected]

mailto:[email protected]



SAMS Site Description

Region: Denver

AQS ID: 080310023

Latitude: 39.781375

Longitude: -104.955423

Picture 1 – Location of SAMS in the Swansea Elementary School Parking Lot

Picture 2 – Interior of SAMS



SAMS Equipment

The list of primary equipment used in this project is shown in the table below.

Airtech/Montrose has supplied and installed the following:

• Glass lined sample probe

• Glass sampling manifold

• Sample blower, fittings, and tubing

• Instrument rack

• Cylinder mounts, calibration gases and regulators

• Security camera

Pollutant/Parameter

Sampling Period

Manufacturer

Model

Nitrogen Oxides

Minute Teledyne T200U

Carbon Monoxide

Minute Thermo Scientific 48i-TLE Trace Level CO

Dynamic Dilution Calibrator Periodic

Teledyne T700U

PM2.5 / PM10 Minute GRIMM

Technologies Inc.

180 EDM

Meteorological measurements

(temperature, pressure, relative

humidity)

Minute GRIMM

Technologies Inc.

180 EDM

Meteorological measurements

(wind speed and wind

direction)

Minute RM Young 05305V

C6 through C12 VOCs 30 Minutes Chromatotec Airmo C6-C12

(Model A27022)

Black Carbon

5 Minutes Magee Scientific Aethalometer

Data Logger

(with remote accessibility)

Multiple Agilaire 8872

Discussion of Results and Professional Judgment

The reported data is for the first quarter PY2018 which is considered, September, October

and November. The RM Young meteorological station was installed on 8/15/17, but due

to a wind direction calibration issue no valid data has been collected, the station is

currently being re-calibrated by the manufacturer. On 11/3/17 a grounding issue was

resolved on the RM Young but after an audit was conducted an 8 degree error in the wind

direction was found, invalidating the data collected during November.



The results of NO2, CO, PM2.5, PM10, black carbon and VOC monitoring data can be

found in Figures 1 through 5 and Table 1 on Pages 7 through 24. The Clean Air Act

requires EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants

considered harmful to public health and the environment. The graphs shown indicate the

readings for each month relative the NAAQS Standard (if applicable). Electronic records

of all data and calibrations have been uploaded to the Dropbox data room maintained by

DEH.

At 10:35 am on 9/24/17 the power went out at the SAMS and was not restored until

08:29 am on 9/25/17. During this approximately 22 hour outage no data was collected.

This report only used the hours of data collected on those days to calculate 24 hour

averages for those days.

The PM2.5 24 hour standard of 35 ug/m3 was exceeded on 9/4/17 and 11/10/17. The

9/4/17 PM2.5 24 hour standard exceedance of 51.2 ug/ m3 was attributed to very dense

smoke plumes from wild fires in western Montana, Northern Idaho, Washington, and

Northern California. The elevated levels in PM2.5 in the days before and after 9/4/17 are

also due to the wild fires in the Northeast. The 11/10/17 PM2.5 24 hour standard

exceedance of 38.3 ug/ m3 was due to a very strong surface temperature inversion. This

causes stagnant air, trapped by the temperature inversion, to sit over Denver all day.

Winds around the SAMS were remained below 6 mph all day, also pointing to local

stagnation. Without other contradictory data, this spike in PM2.5 was local Denver

emissions trapped by stagnate meteorology. PM2.5 was elevated at most (but not at

Chatfield and National Jewish) of the Denver area PM2.5 stations for most of the middle

of the day.

No other pollutant standards were exceeded during Q1 PY2018.

An exceptional event is any unusual or naturally occurring event that can affect air quality

but cannot not be reasonably controlled using techniques that agencies may implement in

order to attain and maintain the NAAQS. All exceptional events are documented by

CDPHE. As of 1/11/18 CDPHE has not declared the above events on 9/4/17 and

11/10/17 as exceptional events.

The aethalometer, GRIMM, and all meteorological equipment was calibrated weekly with

no unusual results or maintenance issues this quarter.

The Chromatotec Gas Chromatograph (GC) for C6 through C12 was calibrated daily by

running a permeation benzene tube and zero air checks with no unusual results this

quarter while the GC was in operation.

The CO and NOX analyzers were calibrated daily by diluting an EPA Protocol 1

calibration. No maintenance issues were observed during the sampling period. Unusual

calibration results were observed as follows: The CO monitor was regularly exceeding

https://www.epa.gov/clean-air-act-overview



the 10% precision requirement when analyzing the one (1) ppm calibration mixture.

These exceedances fell between an 11 to 15% error. Considering the ambient levels of

CO were found to be well below the 1-hour and 8-hour standards we consider the

ramifications for the exceedances to be negligible. The CO analyzer precision level

calibration mixture was increased to 1.5 ppm on 1/3/18 to increase the acceptable range

of error, which should increase the passing rate of the precision level calibration. The

NO2 monitor was regularly exceeding the 10% precision requirement when analyzing the

seventy (70) ppb calibration mixture. These exceedances fell between an 11 to 18% error.

The Gas Phase Titration (GPT) used to produce the NO2 gas by mixing O3 and NO gas is

created with the Dynamic Gas Dilution Calibrator. The Gas Phase Titration Pre-Set

(GPTPS) is run to calibrate the ozone generator to improve the accuracy of the O3

concentration. A GPTPS will be run weekly beginning 1/5/18. This should increase the

passing rate of the precision level calibration.



Pollutant Data Collected

Figure 1a – Monthly PM10 Data

The graph below is shown for September and is the plot of the 24 hour averages. The

orange line represents the 150 micrograms per cubic meter (ug/m3) 24 hour ambient PM10

standard.



Figure 1b – Monthly PM10 Data

The graph below is shown for October and is the plot of the 24 hour averages. The orange

line represents the 150 ug/m3 24 hour ambient PM10 standard.



Figure 1c – Monthly PM10 Data

The graph below is shown for November and is the plot of the 24 hour averages. The

orange line represents the 150 ug/m3 24 hour ambient PM10 standard.



Figure 2a – Monthly PM2.5 Data

The graph below is shown for September and is a plot of the 24 hour averages. The

orange line represents the 35 ug/m3 24 hour ambient PM2.5 standard and the yellow line

represents the 12 ug/m3 one (1) year mean ambient PM2.5 standard. Please note that the

24 hour average values cannot be directly compared to the annual mean standard.



Figure 2b – Monthly PM2.5 Data

The graph below is shown for October and is a plot of the 24 hour averages. The orange

line represents the 35 ug/m3 24 hour ambient PM2.5 standard and the yellow line





Figure 2c – Monthly PM2.5 Data

The graph below is shown for November and is a plot of the 24 hour averages. The

orange line represents the 35 ug/m3 24 hour ambient PM2.5 standard and the yellow line





Figure 3a – Monthly NO2 Data

The graph below is shown for September is a plot of the one (1) hour averages. The

orange line represents the 100 parts per billion (ppb) one (1) hour ambient NO2 standard

and the yellow line represents the 53 ppb one (1) year mean ambient NO2 standard.

Please note that the one (1) hour average values cannot be directly compared to the

annual mean standard.



Figure 3b – Monthly NO2 Data

The graph below is shown for October is a plot of the one (1) hour averages. The orange

line represents the 100 ppb one (1) hour ambient NO2 standard and the yellow line

represents the 53 ppb one (1) year mean ambient NO2 standard. Please note that the one

(1) hour average values cannot be directly compared to the annual mean standard.



Figure 3c – Monthly NO2 Data

The graph below is shown for November is a plot of the one (1) hour averages. The

orange line represents the 100 ppb one (1) hour ambient NO2 standard and the yellow line

represents the 53 ppb one (1) year mean ambient NO2 standard. Please note that the one

(1) hour average values cannot be directly compared to the annual mean standard.



Figure 4a – Monthly CO Data

The graph below is shown for September and is a plot of the one (1) hour averages. The

orange line represents the nine (9) ppm eight (8) hour ambient CO standard and the

yellow line represents the 35 ppm one (1) hour ambient CO standard.



Figure 4b – Monthly CO Data

The graph below is shown for October and is a plot of the one (1) hour averages. The





Figure 4c – Monthly CO Data

The graph below is shown for November and is a plot of the one (1) hour averages. The





Figure 5a – Monthly Black Carbon Data

The graph below is shown for September and plots the 24 hour averages. Black Carbon

does not have a NAAQS Standard.



Figure 5b – Monthly Black Carbon Data

The graph below is shown for October and plots the 24 hour averages. Black Carbon




Figure 5c – Monthly Black Carbon Data

The graph below is shown for November and plots the 24 hour averages. Black Carbon




The results of the selected VOC compounds are shown in the table below. Electronic

records of all VOC compounds have been uploaded to the Dropbox data room maintained

by DEH. When calculating the average, the following rules were applied:

• If an individual result was above the reporting limit (RL), the result was used in

calculating the average

• If an individual result was below the RL or not detected, one half the RL was used

in calculating the average.

Table 1a – Monthly Summary of VOC Data

The table below is shown for September and averages 30 minute runs. None of the

compounds reported have a NAAQS Standard.

Compound

Average

Result for

September

(ppb)

Total

Number

of Data

Points

Number

Above

QL2

Number

Between

RL and

QL

Number

Below RL

N-Hexane 0.257 1286 627 330 329

N-Heptane 0.0978 1286 153 256 877

N-Octane 0.0891 1286 148 205 933

Benzene 0.102 1286 152 293 841

Toluene 0.364 1286 689 327 270

Ethylbenzene 0.0680 1286 31 145 1110

m,p-Xylene 0.190 1286 171 414 701

o-Xylene 0.109 1286 13 51 1222

2 Quantification Limit (QL)



Table 1b – Monthly Summary of VOC Data

The table below is shown for October and averages 30 minute runs. None of the


Compound

Average

Result for

October

(ppb)

Total

Number

of Data

Points

Number

Above

QL3

Number

Between

RL and

QL

Number

Below RL

N-Hexane 0.256 1348 557 391 400

N-Heptane 0.0901 1348 131 186 1031

N-Octane 0.0786 1348 94 149 1105

Benzene 0.112 1348 183 276 889

Toluene 0.431 1348 712 262 374

Ethylbenzene 0.0778 1348 55 170 1123

m,p-Xylene 0.213 1348 227 369 752

o-Xylene 0.115 1348 19 82 1247




Table 1c – Monthly Summary of VOC Data

The table below is shown for November and averages 30 minute runs. None of the


Compound

Average

Result for

November

(ppb)

Total

Number

of Data

Points

Number

Above

QL4

Number

Between

RL and

QL

Number

Below RL

N-Hexane 0.399 1345 787 273 285

N-Heptane 0.143 1345 325 229 791

N-Octane 0.0898 1345 143 226 976

Benzene 0.172 1345 377 298 670

Toluene 0.538 1345 906 246 193

Ethylbenzene 0.0984 1345 120 257 968

m,p-Xylene 0.269 1345 349 397 599

o-Xylene 0.123 1345 30 137 1178

Table 2 – Reporting and Quantification Limits for Selected VOC Compounds

The RLs and QLs for the selected compounds is shown in the table below:

Compound

Reporting

Limit

(ppb)

Quantification

Limit (ppb)

N-Hexane 0.1 0.2

N-Heptane 0.1 0.2

N-Octane 0.1 0.2

Benzene 0.1 0.2

Toluene 0.1 0.2

Ethylbenzene 0.1 0.25

m,p-Xylene 0.15 0.35

o-Xylene 0.2 0.35




Data Quality Assurance/Quality Control

Quality Assurance/Quality Control

Quality assurance is a general term for the procedures used to ensure that a particular

measurement meets the quality requirements for its intended use. Quality control of

continuous analyzers consists of precision and span checks or flow verifications. Quality

objectives were assessed via laboratory and site system audits.

All work being done on this project follows the operating procedures described in the

“Swansea Air Monitoring Station Quality Assurance Project Plan” (QAPP) dated 7/1/17.

The QAPP can be provided by Michael Ogletree upon request. Mr. Ogletree’s contact

information can be found in the “Operational Staff and Contacts” section of this report.

To ensure the collection of high quality data, the following Quality Assurance/Quality

Control procedures were implemented:

NOX and CO Analyzers - Span Test

A span test was conducted every other day. The NOX span test started at 21:46 and lasted

for approximately 50 minutes. The CO span test started at 22:46 and lasted for

approximately 20 minutes.

A CO span test was conducted by first analyzing a span gas of CO which was introduced

to the sampling manifold at the back of the analyzer. After a stable reading was reached

and recorded, a zero gas was introduced to the sampling manifold at the back of the

analyzer. The CO gas was generated by diluting an EPA Protocol 1 calibration gas using

the Teledyne Dynamic Dilution Calibrator.

An NO/NO2 span test was conducted by first analyzing a zero gas that was introduced to

the sampling manifold at the back of the analyzer. After a stable reading was reached and

recorded, a span gas of NO was introduced to the sampling manifold at the back of the

analyzer. The NO gas was also generated by diluting an EPA Protocol 1 calibration gas

using the Teledyne Dynamic Dilution Calibrator. After a stable reading was reached and

recorded, a span gas of NO2 was generated by diluting an EPA Protocol 1 calibration gas

and combing the diluted gas with a known quantity of ozone (O3) using the Teledyne

Dynamic Dilution Calibrator. After a stable reading was reached and recorded, a zero gas

was introduced to the sampling manifold at the back of the analyzer.

Each calibration gas was certified according to EPA Protocol 1 procedures. The

generated gases were approximately, five (5) ppm of CO, 400 ppb of NO and 300 ppb of

NO2. In all cases the measured responses were then compared to the generated gas value

to determine the analyzer drift. The EPA requirement for span is 10 percent. The span

check results are summarized in the table below:



Parameter Span Count5 Span Passed Span Percentage

Nitrogen Oxide 44 44 100

Nitrogen Dioxide 44 44 100

Carbon Monoxide 44 42 95

NOX and CO Analyzers - Precision Test

A precision test was conducted every other day. The NOX precision test started at 21:46

and lasted for approximately 50 minutes. The CO precision test started at 22:46 and

lasted for approximately 20 minutes.

A CO precision test was conducted by first analyzing a precision gas of CO which was

introduced to the sampling manifold at the back of the analyzer. After a stable reading

was reached and recorded, a zero gas was introduced to the sampling manifold at the back

of the analyzer. The CO gas was generated by diluting an EPA Protocol 1 calibration gas

using the Teledyne Dynamic Dilution Calibrator.

An NO/NO2 precision test was conducted by first analyzing a zero gas that was

introduced to the sampling manifold at the back of the analyzer. After a stable reading

was reached and recorded, a precision gas of NO was introduced to the sampling

manifold at the back of the analyzer. The NO gas was also generated by diluting an EPA

Protocol 1 calibration gas using the Teledyne Dynamic Dilution Calibrator. After a stable

reading was reached and recorded, a precision gas of NO2 was generated by diluting an

EPA Protocol 1 calibration gas and combining the diluted gas with a known quantity of

ozone (O3) using the Teledyne Dynamic Dilution Calibrator. After a stable reading was

reached and recorded, a zero gas was introduced to the sampling manifold at the back of

the analyzer.

Each calibration gas was certified according to EPA Protocol 1 procedures. The

generated gases were approximately, one (1) ppm of CO, 100 ppb of NO and 70 ppb of

NO2. In all cases the measured responses were then compared to the generated gas value

to determine the analyzer drift. The EPA requirement for span is 10 percent. The span

check results are summarized in the table below:

Parameter Precision

Count

Precision

Passed Span Percentage

Nitrogen Oxide 46 46 100

Nitrogen Dioxide 46 28 61

Carbon Monoxide 46 34 74

5 Due to a power outage from the morning of 9/24/17 to the morning of 9/25/17 a Span Test was

inadvertently skipped



PM2.5 / PM10 Analyzer

A zero check was conducted on the GRIMM analyzer every two (2) weeks. The zero

check was conducted by placing a particulate filter inline and observing the response of

the analyzer. If anything other than a zero reading was observed, corrective action was

taken. Additionally, a flow check was conducted on the analyzer by using a NIST

traceable standard to measure the flow rate through the GRIMM. The NIST standard was

a MesaLabs DCL-MH DryCal flowmeter. The calibration certification can be found in

the Appendix of this report. The flow test was considered acceptable if the flow rate was

between 1.15 and 1.25 liters per minute (lpm). On a weekly basis the met station ambient

temperature, relative humidity, and pressure was checked by comparing the measured

values to that of a reference standard. The results were considered acceptable if the

temperature, relative humidity, and pressure was within 2oC, 5%, and 10 mmHg,

respectively. A summary of the weekly and biweekly checks is summarized below.

Test Count6 Passed Percentage

Zero Check 7 7 100%

Flow Check 7 7 100%

Temperature Check 12 12 100%

Pressure Check 12 12 100%

Aethalometer

On a monthly basis the aethalometer cyclone was cleaned and inspected. A flow check

was conducted using a NIST traceable standard to measure the flow rate through the

aethalometer. The NIST standard was a MesaLabs DCL-MH DryCal flowmeter. The

calibration certification can be found in the Appendix of this report. The flow test was

considered acceptable if the flow rate was within seven (7) percent of the measured value.

Additionally, a leak check was conducted by capping the sample probe and observing the

measured flow through the instrument. The leak check was considered valid if the

measured flow rate was less than 2.5 liters per minute (lpm). A summary of the monthly

checks and is summarized below:

Test Count Passed Percentage

Flow Check 3 3 100%

Leak Check 3 3 100%

6 Temperature and Pressure check on 11/20/17 was not completed due to the unavailability of a technician



Wind Speed and Wind Direction

The wind speed is calibrated via an anemometer drive that provides a convenient and

accurate way to rotate the anemometer shaft at a known rate. The known rate that the

drive rotates can then be compared to the wind speed reading on the data logger.

The wind direction is calibrated with a vane angle bench stand. The monitor is placed on

the stand which has a base with markings of 0 to 360 degrees. The tail of the monitor is

stabilized so that as the monitor is rotated the wind direction readings are stable on the

data logger.

Because the RM Young sensor was not collecting valid data during Q1 PY2018 no

QA/QC was performed.

Gas Chromatograph

The GC was calibrated prior to installation using a gas standard containing a known

concentration of the Photochemical Assessment Monitoring Station (PAMS) list of

compounds. A copy of the calibration certification can be found in the Appendix of this

report. Two (2) additional concentrations were prepared and analyzed by diluting the

cylinder gases using zero air and a Thermo Model 146i Multi-Gas Calibrator.

A multipoint calibration of the GC was conducted before monitoring commenced. The

calibration also identifies 35 compounds (or pairs of compounds that coelute). An

example of the calibration for one of these compounds, benzene, is shown in the

following figure. This calibration spans the concentration range from about 1 to 17 ppb.

Similar calibrations were done for the other PAMS compounds identified by the GC.



The PAMS calibration data collected on 9/28/2017 was prior to recalibration of the mass

flow controller used for dilution of the PAMS gas mixture. This lead to an inaccurate

calibration. Additional PAMS calibration data was collected on 10/31/2017, after

recalibration of the flow controller. Four repeated samples were collected at a single

concentration with a measured response of about 93% of actual. No BTEX gas runs were

sampled during Q1 PY2018.

The detection limit for the GC technique was determined from data collected during

repeated measurements of a low concentration PAMS standard mixture. The detection

limit is three (3) times the standard deviation of low concentration measurements for the

individual compounds. Because some peaks are close together, there is a greater

uncertainty for partially overlapping peaks and small retention time shifts. We have

chosen to use a reporting limit, as the smallest concentration where we have confidence

that the compound is present. The smallest reporting limit has been set at 0.1 ppb and is

greater than or equal to three times the standard deviation for each of the compounds.

Compounds present at concentrations equal to the detection limit (or reporting limit, in

this case) are believed to be present, but concentrations near this limit are highly



uncertain. Data to be used quantitatively should exceed the quantitation limit. This

limit is used to identify when the concentration that was measured for the compound is

known with a reasonable degree of confidence. The quantitation limit is normally

defined as 10 times the standard deviation of low concentration measurements for

individual compounds. Concentrations below the quantitation limit and above the

reporting limit really indicates that the compound was present, but the concentration is

too uncertain to be of value.

The GC technique used in this work uses a sorbent tube to collect C6 through C12

hydrocarbons, then thermally desorbs these compounds onto the GC column for

separation. The larger compounds are not completely desorbed under the conditions used

in this analysis, so that can place additional limitations on the quantitative determination

of the concentrations of some of these compounds, since some of the compound collected

during one time period will not be desorbed until the following sample is analyzed. This

carryover of sample to a subsequent period was estimated by looking at data for a zero

sample following a PAMS calibration sample. This data allows one to estimate the

percent carryover of compounds to a subsequent period. The data for both undecane and

dodecane suggests that the carryover is more than 50% so concentrations will not be

reported for these compounds. The following table shows the reporting limits,

quantitation limits and estimated percent carryover for each of the compounds identified

in this work.



Reportable Compounds

Reporting Quantitation Approximate

# Name Limit Limit % carryover

ppbv ppbv

1 2,2-Dimethylbutane 0.1 0.2 <5%

2 n-Hexane 0.1 0.2 <5%

3 Methylcyclopentane & 2,4-

dimethylpentane7

0.1 0.25 <5%

4 Benzene 0.1 0.2 <5%

5 Cyclohexane 0.25 0.75 <5%

6 2-Methylhexane & 2,3-dimethylpentane 0.2 0.5 <5%

7 3-Methylhexane 0.1 0.2 <5%

8 2,2,4-Trimethylpentane 0.1 0.2 <5%

9 n-Heptane 0.1 0.2 <5%

10 Methylcyclohexane 0.1 0.2 <5%

11 2,3,4-Trimethylpentane 0.1 0.2 <5%

12 Toluene 0.1 0.2 <5%

13 2-Methylheptane 0.1 0.2 <5%

14 3-Methylheptane 0.1 0.2 <5%

15 n-Octane 0.1 0.2 5%

16 Ethylbenzene 0.1 0.25 10%

17 m & p-Xylene 0.15 0.35 10%

18 Styrene 0.2 0.5 15%

19 o-Xylene 0.2 0.35 10%

20 n-Nonane 0.1 0.2 10%

21 Isopropylbenzene 0.1 0.2 10%

22 a-Pinene 0.2 0.4 nd

23 n-Propylbenzene 0.15 0.35 15%

24 m-Ethyltoluene 0.3 1 15%

25 p-Ethyltoluene 0.2 0.65 15%

26 1,3,5-Trimethylbenzene 0.2 0.5 15%

27 o-Ethyltoluene 0.2 0.5 15%

28 1,2,4-trimethybenzene 0.25 0.75 20%

29 n-Decane 0.3 0.85 20%

30 1,2,3-Trimethylbenzene 0.3 0.85 20%

31 m-Diethylbenzene 0.3 0.9 20%

32 p-Diethylbenzene 0.4 1.3 25%

33 n-Undecane 45%

7 Due to Methylcyclopentane & 2,4-dimethylpentane co-eluting the concentrations of the

individual compounds became unavailable, therefore the compound concentrations must

be reported as a sum of both compounds



34 n-Dodecane 45%

To verify the stability of the GC, a span check was normally done at a 25-hour interval.

The span check used a benzene permeation tube that emits benzene at a rate of 101

nanograms per minute, and was diluted to generate a gas concentration of approximately

55 ppb. The span check was followed by a zero check to minimize carryover of the high

benzene concentration of benzene from the span check to the next ambient sample and to

verify the desorption efficiency and check for contamination of the GC.

If the results of the span check varied by more than ±15% from the average response that

has been observed previously for more than two (2) consecutive days, a system retention

time and response test was scheduled as soon as possible. Appropriate remedial action

was taken if a problem was observed. A control chart showing the results of the span

check for September, October, and November 2017 is shown below.

The calculated concentration of benzene from the permeation tube was initially about 39

ppbv (through 10/25/17). The flow of dilution gas was reduced, increasing the benzene

concentration to about 62 ppbv (from 10/26/17 - 11/10/17). A new permeation tube was

installed, emitting benzene at a lower rate, having a benzene concentration about 24 ppbv

(beginning on 11/10/17).

For the zero checks, the benzene carryover from a preceding calibration or span check

should be less than 1% of the concentration of the benzene in the span gas. If this zero

check limit was exceeded on more than two (2) consecutive days, a system retention time

and response test was scheduled as soon as possible. Appropriate remedial action was

taken if a problem was observed. A control chart showing the results of the zero check

for September, October, and November 2017 is shown as follows.



The zero and span checks are summarized below:

Test Count Passed Percentage

Span Check 100 98 98%

Zero Check 89 89 100%



Signature Page

Prepared and reviewed by:

Patrick Clark, PE


Austin Heitmann


Additionally reviewed by:

Michael Ogletree


Appendix

Quality Assurance Logs

Calibration Certification Sheets

Primary Flow Standard Certification Sheet

swansea ambient air monitoring station (sams) 1st quarter ... · 1st quarter py2018 air quality...

Documents