UC Irvine

Emissions of hydrocarbons associated with oil and natural gas infrastructure are of current significant interest to atmospheric scientists. Studies aim to address the local and regional air quality impacts of oil and gas operations throughout North America. In Fort McMurray, multiple facilities mine and upgrade crude bitumen. The “Industrial Heartland” in Fort Saskatchewan, Alberta is Canada’s largest hydrocarbon processing center, home to over 40 chemical and petrochemical facilities. Ambient samples collected in both regions during the summer of 2010 revealed significant enhancements in over 40 VOCs. Many of these measured values were similar to or greater than some of the world’s largest urban and industrial centers. The primary sources of these VOCs included propene fractionation, diluent separation, and bitumen processing facilities. Hydroxyl radical reactivity (ROH) was calculated in each region as a measure of ozone formation potential. On average, background samples had a ROH of 4.4 s-1, while industrial plumes averaged 9.2 s-1, with reactivity reaching up to 60 s-1 in the most concentrated plumes. Acetaldehyde, propene, and 1,3-butadiene had the largest contributions to the ROH values.

The Barnett Shale of northern Texas is one of the most developed and active natural gas shale plays in the United States. Emissions from the many oil and gas system components in the region have not been fully characterized. Whole air samples were collected throughout the region in October 2013, targeting known methane sources. Hydrocarbon mixing ratios, correlation plots, and stable isotopes were used to discern emission signatures for thermogenic (oil and gas) versus biogenic sources of methane. Ratios of ethane and propane to methane were distinct for each source type, although highly variable, and used to characterize natural gas as either wet or dry. Integration of these ratios into a bottom-up methane emissions inventory for the region predicted a median ethane flux of 5500 kg C2H6 hr-1, which was consistent with top-down estimates. Lastly, the impact of emissions on local photochemistry and a statistical source apportionment suggested that thermogenic sources are responsible for nearly 70% of hydroxyl reactivity, matching the 64-72% predicted by the CH4 inventory. Overall, oil and natural gas activities were the dominant source of CH4 in the Barnett Shale region.

In addition to their influence on air quality and climate, VOCs emitted from oil and natural gas operations are of concern because of their potential health risks. Compounds such as 1,3-butadiene and benzene are hazardous air pollutants and known cancer-causing agents. In the communities closest to the Industrial Heartland, a 13-year record revealed a higher rate of male hematopoietic cancers than other communities in Alberta. The industrial emissions cannot directly be linked to cancer rates, but the elevated VOC concentrations in the region warrant further monitoring and research. In the Barnett Shale, oil and wet natural gas emit increased amounts of potentially harmful gases, including benzene. Using two methods, benzene emission estimates were calculated for the region, and ranged from 48 ± 16 to 84 ± 26 kg C6H6 hr-1.