Swansea Ambient Air Monitoring Station (SAMS)
4th Quarter PY2017 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-Q4 2017
December 14, 2017
City and County of Denver
Report ID: 6203-Q4 2017
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 ........................................................................................................... 6
Figure 1a – Monthly PM10 Data .................................................................................................................. 6 Figure 1b – Monthly PM10 Data .................................................................................................................. 7 Figure 1c – Monthly PM10 Data ................................................................................................................... 8 Figure 2a – Monthly PM2.5 Data .................................................................................................................. 9 Figure 2b – Monthly PM2.5 Data ................................................................................................................ 10 Figure 2c – Monthly PM2.5 Data ................................................................................................................ 11 Figure 3a – Monthly NO2 Data .................................................................................................................. 12 Figure 3b – Monthly NO2 Data .................................................................................................................. 13 Figure 3c – Monthly NO2 Data .................................................................................................................. 14 Figure 4a – Monthly CO Data ................................................................................................................... 15 Figure 4b – Monthly CO Data ................................................................................................................... 16 Figure 4c – Monthly CO Data ................................................................................................................... 17 Figure 5a – Monthly Black Carbon Data ................................................................................................... 18 Figure 5b – Monthly Black Carbon Data ................................................................................................... 19 Figure 5c – Monthly Black Carbon Data ................................................................................................... 20 Table 1 – Summary of VOC Data ............................................................................................................... 21
DATA QUALITY ASSURANCE/QUALITY CONTROL ........................................................................ 23
Quality Assurance/Quality Control ............................................................................................................ 23 NOX and CO Analyzers - Span Test ........................................................................................................................ 23 NOX and CO Analyzers - Precision Test .................................................................................................................. 24 PM2.5 / PM10 Analyzer ............................................................................................................................................. 25 Aethalometer ........................................................................................................................................................... 25 Wind Speed and Wind Direction ............................................................................................................................. 25 Gas Chromatograph ................................................................................................................................................. 26
SIGNATURE PAGE .................................................................................................................................... 32
APPENDIX
Quality Assurance Logs Calibration Certification Sheets Primary Flow Standard Certification Sheet
City and County of Denver
Report ID: 6203-Q4 2017 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 Q4 PY2017:
• 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 2
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]
City and County of Denver
Report ID: 6203-Q4 2017 Page 3
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
City and County of Denver
Report ID: 6203-Q4 2017 Page 4
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 fourth quarter PY2017 which is considered, June, July and
August. The RM Young meteorological station was installed on 8/15/17, but due to a
grounding issue on the signal cable no valid data was collected until 11/3/17, therefore no
valid wind speed or wind direction data was collected during Q4 PY2017.
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 6 through 21. The Clean Air Act
requires EPA to set National Ambient Air Quality Standards (NAAQS) for pollutants
City and County of Denver
Report ID: 6203-Q4 2017 Page 5
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.
No pollutant standard was exceeded during Q4 PY2017. Additionally, there were no
exceptional events, weather or otherwise, during the sampling period. 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.
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. A board malfunction occurred on 4/22/17 and the
GC was sent in for repair. The GC was re-installed and re-started operation on 7/17/17.
Due to an erroneous factory setting adjustment made during the repair, valid data
collection did not occur until 8/17/17.
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
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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 6
Pollutant Data Collected
Figure 1a – Monthly PM10 Data
The graph below is shown for June and is the plot of the 24 hour averages. The orange
line represents the 150 ug/m3 24 hour ambient PM10 standard.
City and County of Denver
Report ID: 6203-Q4 2017 Page 7
Figure 1b – Monthly PM10 Data
The graph below is shown for July and is the plot of the 24 hour averages. The orange
line represents the 150 ug/m3 24 hour ambient PM10 standard.
City and County of Denver
Report ID: 6203-Q4 2017 Page 8
Figure 1c – Monthly PM10 Data
The graph below is shown for August and is the plot of the 24 hour averages. The orange
line represents the 150 ug/m3 24 hour ambient PM10 standard.
City and County of Denver
Report ID: 6203-Q4 2017 Page 9
Figure 2a – Monthly PM2.5 Data
The graph below is shown for June 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 10
Figure 2b – Monthly PM2.5 Data
The graph below is shown for July 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 11
Figure 2c – Monthly PM2.5 Data
The graph below is shown for August 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 12
Figure 3a – Monthly NO2 Data
The graph below is shown for June 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 13
Figure 3b – Monthly NO2 Data
The graph below is shown for July 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 14
Figure 3c – Monthly NO2 Data
The graph below is shown for August 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 15
Figure 4a – Monthly CO Data
The graph below is shown for June 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 16
Figure 4b – Monthly CO Data
The graph below is shown for July 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 17
Figure 4c – Monthly CO Data
The graph below is shown for August 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 18
Figure 5a – Monthly Black Carbon Data
The graph below is shown for June and plots the 24 hour averages. Black Carbon does
not have a NAAQS Standard.
City and County of Denver
Report ID: 6203-Q4 2017 Page 19
Figure 5b – Monthly Black Carbon Data
The graph below is shown for July and plots the 24 hour averages. Black Carbon does
not have a NAAQS Standard.
City and County of Denver
Report ID: 6203-Q4 2017 Page 20
Figure 5c – Monthly Black Carbon Data
The graph below is shown for August and plots the 24 hour averages. Black Carbon
does not have a NAAQS Standard.
City and County of Denver Report ID: 6203-Q4 2017 Page 21
Table 1 – Summary of VOC Data 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.
Compound
Average Result for August2
(ppb)
Total Number of Data Points
Number Above QL3
Number Between RL and
QL Number
Below RL N-Hexane 0.259 614 316 181 117 N-Heptane 0.0935 614 65 113 436 N-Octane 0.123 614 42 82 490 Benzene 0.0952 614 55 159 400 Toluene 0.410 614 409 125 80 Ethylbenzene 0.0722 614 11 76 527 m,p-Xylene 0.190 614 79 231 304 o-Xylene 0.108 614 2 22 590
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
2 Data is for 8/17/17 to 8/31/17, on 4/23/17 the Chromatotec GC failed and did not begin collecting valid data again until 8/17/17. Therefore, VOCs were not monitored in June and July 2017. 3 Quantification Limit (QL)
City and County of Denver
Report ID: 6203-Q4 2017 Page 23
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:
City and County of Denver
Report ID: 6203-Q4 2017 Page 24
Parameter Span Count Span Passed Span Percentage
Nitrogen Oxide 46 46 100
Nitrogen Dioxide 46 28 61
Carbon Monoxide 46 46 100
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 Span Count Span Passed Span Percentage
Nitrogen Oxide 46 45 98
Nitrogen Dioxide 46 39 85
Carbon Monoxide 454 265 58
4 The CO precision test did not run on June 13, 2017. 5 See note in discussion of results.
City and County of Denver
Report ID: 6203-Q4 2017 Page 25
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 Count Passed Percentage
Zero Check 6 6 100%
Flow Check 6 6 100%
Temperature Check 13 13 100%
Pressure Check 13 13 100%
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%
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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 26
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 installed during Q4 PY2017 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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 27
An issue with the calibration of the mass flow controller in the gas dilution system used
to generated these PAMS gas mixtures has resulted in the values of the actual
concentrations being too high.
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
City and County of Denver
Report ID: 6203-Q4 2017 Page 28
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.
City and County of Denver
Report ID: 6203-Q4 2017 Page 28
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-
dimethylpentane6
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%
34 n-Dodecane 45%
6 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
City and County of Denver
Report ID: 6203-Q4 2017 Page 29
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
35 ppb. Once the GC returned from being serviced the dilution flow rate was decreased
thus decreasing the gas concentration from 55 ppb in Q3 PY2017 to 35 ppb in Q4
PY2017. 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 August 2017 is shown below.
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 August 2017 is shown as follows.
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Report ID: 6203-Q4 2017 Page 31
The zero and span checks are summarized below:
Test Count Passed Percentage
Span Check 16 16 100%
Zero Check 30 30 100%
City and County of Denver
Report ID: 6203-Q4 2017 Page 32
Signature Page
Prepared and reviewed by:
Patrick Clark, PE
Montrose Air Quality Services, LLC
Austin Heitmann
Montrose Air Quality Services, LLC
Additionally reviewed by:
Michael Ogletree
City and County of Denver
Appendix
Quality Assurance Logs
Calibration Certification Sheets
Primary Flow Standard Certification Sheet