Gas flux and isotopic sampling of diffuse gas at a site of serpentinization for the purposes of sourcing methane

Morrissey, Liam (2016) Gas flux and isotopic sampling of diffuse gas at a site of serpentinization for the purposes of sourcing methane. Masters thesis, Memorial University of Newfoundland.

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Abstract

The flux of natural CH₄ released and CO₂ sequestered at a site of serpentinization were determined and methods for sourcing dissolved and diffuse CH₄ at the site were tested. Greenhouse gas fluxes (CO₂, CH₄, N₂O) at an ultra-basic pool associated with a site of serpentinization in the Tablelands, Gros Morne, NL were measured to determine the impact on atmospheric heating. It was calculated that the site had a small net reduction on atmospheric heating over a time horizon of 100 years and a net increase on atmospheric heating over a time horizon of 30 years. Methods for sourcing methane were also examined in this thesis. Several common collection and concentration methods were tested in the laboratory and at the Tablelands and were shown to be non-isotopically fractionating for CH₄. Additionally, a metadata analysis showed that a carbon fractionation factor of above 1.04 better described microbial CH₄ and below better described abiogenic CH₄. Results from this thesis are the first to calculate the flux of both CH₄ released and CO₂ sequestered at a site of serpentinization and highlight the need for an understanding of the natural baseline of these sites.

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