Rapid desorption of radium isotopes from black shale during hydraulic fracturing. 1. Source phases that control the release of Ra from Marcellus Shale

Hydraulic fracturing of the Marcellus Shale produces wastewaters that are hypersaline and highly enriched in isotopes of radium. Radium is understood to derive from the Marcellus Shale itself, but its source phases and their contributions to wastewater production have not been described. Using seque...

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Bibliographic Details
Published in:Chemical geology 2018-09, Vol.496, p.1-13
Main Authors: Landis, Joshua D., Sharma, Mukul, Renock, Devon, Niu, Danielle
Format: Article
Language:English
Subjects:
226Ra
228Ra
Exchange
Isotope
Marcellus
Produced water
Radium
Rock
Shale
Sorption
Wastewater
Water
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Summary:Hydraulic fracturing of the Marcellus Shale produces wastewaters that are hypersaline and highly enriched in isotopes of radium. Radium is understood to derive from the Marcellus Shale itself, but its source phases and their contributions to wastewater production have not been described. Using sequential extractions and experimental leachates, we characterize two distinct end-members that could contribute Ra to wastewaters, (1) a mineral phase, which hosts labile228Ra and has 226Ra/228Ra atom ratios ~250, and (2) an organic phase, which hosts exchangeable226Ra and has 226Ra/228Ra ~10,000. In leaching experiments we observed rapid extraction of Ra from these phases, with high ionic strength solutions leaching up to 14% of Ra from the shale in just hours. Radium concentrations and 226Ra/228Ra ratios increase with [Ca2+] of the leaching solution, and solutions approaching 1 M Ca2+ produce 226Ra/228Ra ratios compatible with Marcellus wastewaters. In contrast, pure water removes
ISSN:0009-2541
1872-6836
DOI:10.1016/j.chemgeo.2018.06.013