Estimating Emissions of Toxic Hydrocarbons from Natural Gas Production Sites in the Barnett Shale Region of Northern Texas

Oil and natural gas
operations have continued to expand and move
closer to densely populated areas, contributing to growing public
concerns regarding exposure to hazardous air pollutants. During the
Barnett Shale Coordinated Campaign in October, 2013, ground-based
whole air samples collected downwind of oil and gas sites revealed
enhancements in several potentially toxic volatile organic compounds
(VOCs) when compared to background values. Molar emissions ratios
relative to methane were determined for hexane, benzene, toluene,
ethylbenzene, and xylene (BTEX compounds). Using methane leak rates
measured from the Picarro mobile flux plane (MFP) system and a Barnett
Shale regional methane emissions inventory, the rates of emission
of these toxic gases were calculated. Benzene emissions ranged between
51 ± 4 and 60 ± 4 kg h–1. Hexane, the
most abundantly emitted pollutant, ranged from 642 ± 45 to 1070
± 340 kg h–1. While observed hydrocarbon enhancements
fall below federal workplace standards, results may indicate a link
between emissions from oil and natural gas operations and concerns
about exposure to hazardous air pollutants. The larger public health
risks associated with the production and distribution of natural gas
are of particular importance and warrant further investigation, particularly
as the use of natural gas increases in the United States and internationally.