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.

Measuring emissions from oil and natural gas well pads using the mobile flux plane technique.

We present a study of methane emissions from oil and gas producing well pad facilities in the Barnett Shale region of Texas, measured using an innovative ground-based mobile flux plane (MFP) measurement system, as part of the Barnett Coordinated Campaign.1 Using only public roads, we measured the emissions from nearly 200 well pads over 2 weeks in October 2013. The population of measured well pads is split into well pads with detectable emissions (N = 115) and those with emissions below the detection limit of the MFP instrument (N = 67). For those well pads with nonzero emissions, the distribution was highly skewed, with a geometric mean of 0.63 kg/h, a geometric standard deviation of 4.2, and an arithmetic mean of 1.72 kg/h. Including the population of nonemitting well pads, we find that the arithmetic mean of the well pads sampled in this study is 1.1 kg/h. This distribution implies that 50% of the emissions is due to the 6.6% highest emitting well pads, and 80% of the emissions is from the 22% highest emitting well pads.

Atmospheric vertical profiles of O3, N2O, CH4, CCl2F2, and H2O retrieved from external-cavity quantum-cascade laser heterodyne radiometer measurements.

Atmospheric vertical profiles of ozone, nitrous oxide, methane, dichlorodifluoromethane, and water are retrieved from data collected with a widely tunable external-cavity quantum-cascade laser heterodyne radiometer (EC-QC-LHR) covering a spectral range between 1120 and 1238 cm(-1). The instrument was operated in solar occultation mode during a two-month measurement campaign at Rutherford Appleton Laboratory in Oxfordshire, UK, in winter 2010/2011, and ultrahigh-resolution (60 MHz or 0.002 cm(-1)) transmission spectra were recorded for multiple narrow spectral windows (~1 cm(-1) width) specific to each molecule. The ultrahigh spectral resolution of the EC-QC-LHR allows retrieving altitudinal profiles from transmission spectra that contain only few (1-3) significant absorption lines of a target molecule. Profiles are validated by comparing with European Centre for Medium-Range Weather Forecasts operational atmospheric profiles (ozone and water), with other data in the literature (nitrous oxide, methane, dichlorodifluoromethane), and with retrievals from a lower resolution (600 MHz or 0.02 cm(-1)) Fourier transform spectroscopy data that were also recorded during the measurement campaign.

Active Wavelength Control of an External Cavity Quantum Cascade Laser.

We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3σ precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm-1. Since this control method can be applied to any external cavity laser with little to no modification, such a precision provides an excellent opportunity for spectroscopic applications that target molecular absorption lines at standard atmospheric conditions.

Atmospheric observations of multiple molecular species using ultra-high-resolution external cavity quantum cascade laser heterodyne radiometry.

We demonstrate a widely tunable laser heterodyne radiometer operating in the thermal IR during an atmospheric observation campaign in the solar occultation viewing mode. An external cavity quantum cascade laser tunable within a range of 1120 to 1238 cm(-1) is used as the local oscillator (LO) of the instrument. Ultra-high-resolution (60 MHz or 0.002 cm(-1) transmission spectroscopy of several atmospheric species (water vapor, ozone, nitrous oxide, methane, and dichlorodifluoromethane) has been demonstrated within four precisely selected molecule-specific narrow spectral windows (∼1 cm(-1). Atmospheric transmission lines within each selected window were fully resolved through mode-hop-free continuous tuning of the LO frequency. Comparison measurements were made simultaneously with a high-resolution Fourier transform spectrometer to demonstrate the advantages of the laser heterodyne system for atmospheric sounding at high spectral and spatial resolutions.