Characterizing anthropogenic methane sources in the Houston and Barnett Shale areas of Texas using the isotopic signature δ13C in CH4

Shuting Yang; Xin Lan; Robert Talbot; Lei Liu

doi:10.1016/j.scitotenv.2019.133856

Characterizing anthropogenic methane sources in the Houston and Barnett Shale areas of Texas using the isotopic signature δ¹³C in CH₄

Sci Total Environ. 2019 Dec 15:696:133856. doi: 10.1016/j.scitotenv.2019.133856. Epub 2019 Aug 8.

Authors

Shuting Yang¹, Xin Lan², Robert Talbot³, Lei Liu⁴

Affiliations

¹ Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States; Institute for Climate and Atmospheric Science, University of Houston, Houston, TX, United States. Electronic address: syang20@uh.edu.
² Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, United States; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, United States.
³ Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States; Institute for Climate and Atmospheric Science, University of Houston, Houston, TX, United States.
⁴ Physics Department, University of Toronto, Toronto, Ontario, Canada.

PMID: 31461696
DOI: 10.1016/j.scitotenv.2019.133856

Abstract

Methane (CH₄) is an important greenhouse gas with its mixing ratio increasing in the global atmosphere. Identifying fingerprints of CH₄ emissions is critical to understanding potential impacts of various anthropogenic sources in the Greater Houston area (GHA) and extensive natural gas operations in the Barnett Shale area (BSA) of Texas. Stable carbon isotope ratios of CH₄ (δ¹³C_CH₄) has been proposed to be a useful technique for differentiating individual CH₄ sources. Measurements of CH₄ mixing ratios and δ¹³C_CH₄ were sampled using a mobile laboratory equipped with cavity ring-down spectrometers (CRDS). Areal CH₄ distributions and the background δ¹³C_CH₄ signature were obtained from filtered ambient signals; -47.0‰ (GHA) and - 48.5‰ (BSA) were calculated. The fingerprint of thirty-three anthropogenic sources in the two study areas were sampled with forty-four δ¹³C analyses conducted. Repeated measurements indicated the natural variation of δ¹³C_CH₄ signatures of individual CH₄ sources. An unexpected massive CH₄ fugitive leak was detected near the San Jacinto River Fleet site in Houston exhibiting an δ¹³C_CH₄ value around -42‰. Our results and findings demonstrate the utility of δ¹³C_CH₄for facilitating emission inventories and atmospheric modeling.

Keywords: Anthropogenic sources; Barnett shale; Houston; Methane; Stable carbon isotope.