Methane, Volatile Organic Compounds, Ozone, and Nitrogen Oxides at the City of Boulder Reservoir (Colorado)
This site presents preliminary results of atmospheric near-real time monitoring at the Boulder Reservoir. This monitoring is sponsored by Boulder County Public Health. Monitoring is conducted by researchers at Boulder A.I.R. LLC, in partnership with the Colorado Department of Public Health and the Environment (CDPHE)
Methane (CH4)
Methane is a potent greenhouse gas. It has an atmospheric lifetime of about a decade and is distributed globally.
Methane emissions in our area mainly come from oil and gas. Livestock, landfills, and wastewater treatment plants are also sources of methane in northeastern Colorado.
Selected Volatile Organic Compounds (VOCs)
Ethane and propane have atmospheric lifetimes of about 2 months and about 2 weeks, respectively. They contribute to formation of ground-level ozone on a regional and continental scale. Oil and gas production and processing activities are the main source of ethane and propane. Propane can also be released to the atmosphere from storage and distribution of liquified petroleum gas.
Butanes and acetylene contribute to formation of ozone on local to regional scales.
Butanes are emitted from gasoline vapors, vehicle exhaust, and oil and gas production. Vehicle exhaust is the main source of acetylene.
Pentanes are also contributors to ozone formation on local to regional scales.
Pentanes are primarily emitted from gasoline vapors and oil and gas production.
Because i-pentane and n-pentane are released in different relative quantities by different sources, the i/n pentane ratio can be used to separate the influence of urban emissions from oil and gas emissions (Gilman, 2013; Thompson, 2014). An i/n pentane ratio of 0.8 - 0.9 is typical of raw oil and gas emissions, whereas a ratio from 2-4 is characteristic of vehicle and urban emissions. In recent years, Boulder's average pentane ratio has been around 1.1 (Gilman, 2013), suggesting a mix of influences from vehicle, urban, and oil and gas emissions.
Benzene and toluene contribute to ozone formation and may be hazardous to health if breathed at high levels.
Sources of toluene include paints, solvents, gasoline vapors and vehicle exhaust. Sources of benzene include gasoline vapors, vehicle exhaust, and oil and gas production activities.
Show Hide Additional VOCs
Ozone (O3) Prior 1-Hour Average (Preliminary data from CDPHE)
* The orange line in the ozone graph indicates the 70 ppb National Ambient Air Quality Standard (NAAQS). Exceedance of the standard occurs when the 8-hour running mean of the ozone readings is equal to or higher than this value.
Nitrogen Oxides (NOX)
Nitrogen oxides (NOX = NO2 + NO) react in the atmosphere to form ozone, nitric acid, and particulate nitrate.
Nitrogen oxides are formed during high temperature combustion in engines and fossil-fuel fired power plants.
Weather
All wind data are given in meters per second but can be converted to miles per hour by roughly doubling them (~2.2). Temperature and relative humidity data are provided by CDPHE, collected real-time, and have not been corrected nor validated.
Pollutant Source
Analysis Information
The bivariate polar plots you see above depict observed quantities of monitored chemicals as colors, plotted by wind direction and speed. Red colors indicate higher levels of the monitored chemical, whereas blue colors represent lower levels. The figure acts as a compass with the Boulder air quality station (BRZ) located at its center. Wind speeds are monitored in meters per second and increase as you move away from the center. This technique aggregates data into wind speed and direction bins and uses the chemical's median value in each bin to color the figure. As such, the scale values shown do not represent the absolute magnitude of the observed chemical. The minimum bin (min-bin) parameter specifies the minimum number of values in each bin needed to be shown in the figure. In some cases, min-bin values that are greater than one are selected to avoid outlier values biasing the results. Gray areas on the figure represent data that has been removed because there were too few data in the particular bin to meet the min-bin threshold. It is also important to note that data with wind speeds less than 1 meter per second are excluded from this analysis to ensure clear wind direction dependency results.
Click the buttons below each plot to view polar plots for all quarters by species
Quarter 3, 2024 Analysis
NOX Analysis Quarters
Methane Analysis Quarters
Benzene Analysis Quarters
Propane Analysis Quarters
Ethane Analysis Quarters
Acetylene Analysis Quarters
Past Quarters
Project Motivation
The Denver Metro North Front Range (DMNFR) has been in violation of the U.S. National Ambient Air Quality Standard (NAAQs) for ozone since 2004 and was designated as a nonattainment area for ozone. This designation sets requirements for the State of Colorado to develop plans for curbing emissions of ozone precursors, with the goal to reduce ozone and reach attainment of the ozone standard. Despite efforts to reduce emissions, air quality has not reached target levels, raising questions about which emission sources are contributing to the DMNFR’s air quality concerns.
In partnership with Boulder County and CDPHE, Boulder A.I.R. LLC is providing near real-time measurements of trace gases and wind data at the Boulder Reservoir. These measurements are used to inform the public about air pollution levels, and by regulators and researchers for studying emissions sources and transport in the DMNFR. A primary goal of this project is the monitoring and improvement of our understanding of emissions and impacts of oil and natural gas development on air quality in Boulder County.
Ozone is a secondary pollutant, formed in the atmosphere from reactions of NOX and VOCs. More background information on ozone, its formation chemistry and health effects, can be found through the EPA. Currently monitored compounds at the Boulder Reservoir include ozone (by CDPHE), nitrogen oxides (NOX), methane (CH4, a greenhouse gas), and a series of volatile organic compounds (VOC), including ethane, and propane, the latter two serving as tracer pollutants for oil and natural gas emissions.
Monitoring Methods
All data presented on this site are preliminary. Data quality protocols are applied at a later time for finalizing of the data.
Methane is monitored with a Picarro G-4302 cavity ring down spectrometer. Data are collected as 1-minute averages.
VOC are monitored by preconcentration of 500 ml-samples onto a micro-adsorbent trap, with subsequent thermal desorption, capillary column gas chromatography separation, and flame ionization detection. Samples are collected at 1-hour intervals. Currently quantified compounds include ethane, ethene, propane, propene, i-butane, acetylene, n-butane, i-pentane, n-pentane, hexane, isoprene, benzene, toluene, ethyl-benzene, m,p-xylene, and o-xylene.
Nitrogen Oxides (NOx) are measured at 1-minute time resolution with a Thermal Environmental Corporation 42iQTL chemiluminescence analyzer. Data are averaged to 5 minutes for display on this website.
Ozone is measured by CDPHE using a Teledyne UV absorption monitor at 1-minute time resolution following the federal regulatory protocol. Data are averaged to 5-min intervals for display on this website.
Wind speed and direction are measured by an R.M. Young propeller anemometer, 4 meters above ground level.
Data
Data requests should be directed to Boulder County Public Health, attention Bill Hayes (bhayes@bouldercounty.org).
Publically Posted Boulder AIR Datasets Available for Dissemination
Metadata
Contacts
Boulder County Public Health
Attn: Bill Hayes (bhayes@bouldercounty.org)
Boulder A.I.R., LLC
Attn: Detlev Helmig (dh.bouldair@gmail.com)
CDPHE
Attn: Erick Mattson (erick.mattson@state.co.us)