Functional Response of a Near-Surface Soil Microbial Community to a Simulated Underground CO2 Storage Leak

Sergio E Morales,William E Holben

doi:10.1371/journal.pone.0081742

Abstract

Understanding the impacts of leaks from geologic carbon sequestration, also known as carbon capture and storage, is key to developing effective strategies for carbon dioxide (CO2) emissions management and mitigation of potential negative effects. Here, we provide the first report on the potential effects of leaks from carbon capture and storage sites on microbial functional groups in surface and near-surface soils. Using a simulated subsurface CO2 storage leak scenario, we demonstrate how CO2 flow upward through the soil column altered both the abundance (DNA) and activity (mRNA) of microbial functional groups mediating carbon and nitrogen transformations. These microbial responses were found to be seasonally dependent and correlated to shifts in atmospheric conditions. While both DNA and mRNA levels were affected by elevated CO2, they did not react equally, suggesting two separate mechanisms for soil microbial community response to high CO2 levels. The results did not always agree with previous studies on elevated atmospheric (rather than subsurface) CO2 using FACE (Free-Air CO2 Enrichment) systems, suggesting that microbial community response to CO2 seepage from the subsurface might differ from its response to atmospheric CO2 increases.

Highlights

Carbon capture and storage (CCS) technology is being explored as an option for reducing carbon dioxide (CO2) emissions to the atmosphere [1,2,3]
CO2 has led the trend of increasing greenhouse gases in the atmosphere with a 28% increase in CO2 emissions between 1990-2004 [19]
In 2004, CO2 emissions were estimated at 30 Gt CO2 equivalents/year, with emissions projected to increase 40% to 110% by 2030 [19]

Summary

Introduction

Carbon capture and storage (CCS) technology is being explored as an option for reducing carbon dioxide (CO2) emissions to the atmosphere [1,2,3]. Supercritical CO2 expands and tends to be buoyant, continuously moving upwards until a “cap rock” (e.g. a barrier of non-porous rock) is encountered This fact, and the ability of a CO2 plume to spread out over a large area suggest that, over time, pathways for CO2 to move upward and escape could lead to stored gas reaching surface soils or the atmosphere [3]. This has led to research aimed at developing monitoring techniques for the detection of CO2 leaks from geologic formations, and to studies on the effects such leaks could have on surface ecosystems [4,5,6]

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