City and County of Broomfield, CO
Program Overview
details about the Broomfield Air Quality Monitoring Program origins, data collected, and the equipment used
The City and County of Broomfield, Colorado implemented a robust, oil & gas-focused air quality monitoring program in late 2018 in response to a new 5 pad, 80+ well oil and gas operation.
The objectives for the monitoring program include:
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Qualify and quantify air contaminants
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Provide insight regarding emissions sources
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Correlate measurements with standardized health guidelines
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Share information with citizens
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Provide air quality information that can inform Broomfield policy
Broomfield's air monitoring network includes:
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Real-time monitoring stations, each capable of auto-triggering canister samples during air quality events.
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Sites with continuous 7-day duration whole-air canister samples
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Sites with periodic (one week per month) 7-day duration whole-air canister samples
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Whole air canisters provided to Broomfield staff for manual sampling during concern events
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An instrumented vehicle called the mobile plume-tracker which is deployed when emission buildup is expected or to investigate an event
Real-time Monitoring Stations
Real-time monitoring stations monitor for the following metrics:
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TVOC Indicator: a PID 10.6 eV sensor responds to over 900 volatile organic compounds output as a voltage signal at 1-minute resolution. This metric is used to identify pollutant change over time and to trigger automated canister samples when VOC events are detected.
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Particulate Matter 2.5 and 10: A Purple Air II sensor provides 1-minute resolution of PM with incredible accuracy. Measurements are typically accurate to within 10% of a reference-grade PM system, though concentrations are less-trustworthy at high concentration values.
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NO Indicator and NO2 Indicator (NOx Indicator): an electrochemical sensor provides indication of NOx change over time. This sensor's limited accuracy makes it useful for general spatial trends over time, and is less useful for minute-by-minute assessment of NOx pollutants.
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Meteorology: a cup and vane anemometer provides wind speed and wind direction while a sensor provides temperature, pressure, and humidity data at 1-minute resolution.
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Auto-trigger Sampling: each sensor system is equipped with a triggering box, which opens a valve to take a 1-minute canister sample when TVOC Indicator reaches a defined event threshold.
Canister Samples
Whole-air canisters are deployed in four ways:
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auto-triggered as 1-minute samples by the monitoring stations
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sampled over a 7-day window on a continuous, week-to-week basis or on a 1 week per month schedule
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manually by staff or citizens
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manually during mobile plume tracker drives
Canister samples are analyzed by the lab at the Colorado State University Department of Atmospheric Science using GC and FID technologies. The canister analysis measures 49 VOC compounds (dubbed TVOC_CSU49) plus methane and ethane.
The canister analytes include:
ethane
ethene
propane
propene
i-butane
n-butane
ethyne
t-2-butene
1-butene
c-2-butene
cyclopentane
i-pentane
n-pentane
t-2-pentene
1-pentene
cis-2-pentene
n-hexane
isoprene
2,4 dimethylpentane
n-heptane
benzene
cyclohexane
2,3-dimethylpentane
2-methylhexane
3-methylhexane
2,2,4-trimethylpentane
methylcyclohexane
2,3,4-trimethylpentane
toluene
2-methylheptane
3-methylheptane
n-octane
ethylbenzene
m+p-xylene
styrene
o-xylene
n-nonane
isopropylbenzene
n-propylbenzene
n-propylbenzene
3-ethyltoluene
4-ethyltoluene
1,3,5-trimethylbenzene
2-ethyltoluene
1,2,4-trimethylbenzene
n-decane
1,2,3-trimethylbenzene
1,3-diethylbenzene
1,4-diethylbenzene
C2HCl3
C2Cl4
methane
Mobile Plume Tracker
The mobile plume tracker is an instrumented vehicle deployed at times when meteorological conditions favor pollutant build-up in the area, or when operational activities are expected to increase emissions.
The mobile plume tracker is equipped with a cavity-ring-down analyzer that measures methane and acetylene at sub-second resolution.
Occasionally, the plume tracker is also outfitted with a fast-GC BTEX analyzer.
As the operator identifies a plume, the plume tracker will attempt to find plume center and plume origin and the operator will manually deploy whole-air canister samples to further characterize the plume composition.