Presence of VOCs show oil & gas heavily influence nearby air quality
Monitoring systems have been set up at the Boulder Reservoir to measure levels of ethane and propane gases, which are emitted in the process of oil and gas manufacturing and distribution. These two volatile organic compounds (or VOCs) are clear tracers of oil and gas emissions. When we see decreases in these two VOCs, it also represents decreases in other harmful pollutants.
Ethane and propane are emitted in association with industrial oil and gas production and processing, and can provide clear tracers of oil and gas activities. Ethane and propane have atmospheric lifetimes of approximately two months to two weeks, respectively. These gases contribute to the formation of ground-level ozone on a regional and continental scale. Propane can also be released into the atmosphere from the storage and distribution of liquefied petroleum gas.
To better understand how oil and gas industries generate emissions that contribute to rising ozone levels, Boulder County started a monitoring study to record real-time concentrations of different atmospheric gases that are known byproducts of oil and gas industries (with a focus on ethane and propane concentrations). Atmospheric monitoring systems at the Boulder Reservoir are used to monitor air quality and have provided data to Boulder County regarding local increases in atmospheric ethane and propane, signalling emissions from oil and gas activity.
The seasonal cycles of ethane and propane shown in the figures below are driven by two factors:
1. During the winter, the mixing of the lower atmosphere is weaker, which causes emissions from nearby sources to accumulate longer and to build up in higher concentrations.
2. The breakdown/oxidation of these compounds is slower during the winter, which gives them longer lifetimes and results in a build up to higher levels.
Oil and gas production has definitive impacts on the levels of propane and ethane. For example, there is a significant distinction between VOC concentrations closer to oil and gas facilities versus farther away. As you can see in Figure 1, concentrations are much higher in Longmont, which is closer to oil and gas facilities, compared to at Boulder Reservoir. Both figures show that each year during the winter months, ethane and propane concentrations spike. This suggests that oil and gas activity in and around Boulder County has been influencing local air quality.
explore the data
Taking a closer look at ethane and propane levels in Boulder’s air.
Figure 1: Ethane concentrations measured at Boulder Reservoir from 4/04/17 to 9/03/2020. The blue lines represent the raw data and the gray line represents the smoothed conditional mean of the data. Notice that peak concentrations occur in winter months. Source: Monitoring is conducted by researchers at Boulder A.I.R. LLC, in partnership with the Colorado Department of Public Health and the Environment (CDPHE) and sponsored by Boulder County Public Health.
Figure 2: Propane concentrations measured at Boulder Reservoir from 4/04/17 to 9/03/2020. The blue lines represent the raw data and the gray line represents the smoothed conditional mean of the data. Notice that peak concentrations occur in winter months. Source: Monitoring is conducted by researchers at Boulder A.I.R. LLC, in partnership with the Colorado Department of Public Health and the Environment (CDPHE) and sponsored by Boulder County Public Health.
Now let’s compare Boulder’s propane concentrations to Longmont, which is closer to areas of oil and gas development.
Figure 3. Propane concentrations measured at Boulder Reservoir for 3 years (04/04/17 to 09/03/20) compared to propane concentrations measured at Longmont Union Reservoir for 8 months (01/29/20 to 09/03/20). Note that the scale of the vertical axes in the two figures is the same (ranges from 0-600 ppb). The blue lines represent the raw data and the gray lines represent the smoothed conditional mean of the data. Notice that peak concentrations occur in winter months. This VOC was 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 were collected at 1.5-hour intervals. Source: Monitoring is conducted by researchers at Boulder A.I.R. LLC, in partnership with the Colorado Department of Public Health and the Environment (CDPHE) and sponsored by Boulder County Public Health.
recommendations
Monitoring VOC concentrations can contribute to proper air quality regulation.
Monitoring VOCs in Boulder County provides an important step in measuring the impacts of oil and gas activity in the region. These monitoring systems can provide scientific data to help inform regulations to reduce VOCs that contribute to air pollution statewide and throughout Boulder County.
