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Measurement of Natural Losses of LNAPL Using CO 2 Traps
Author(s) -
McCoy Kevin,
Zimbron Julio,
Sale Tom,
Lyverse Mark
Publication year - 2014
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/gwat.12240
Subject(s) - sorbent , isobaric process , flux (metallurgy) , chemistry , analytical chemistry (journal) , environmental science , environmental chemistry , thermodynamics , physics , organic chemistry , adsorption
Abstract Efflux of CO 2 above releases of petroleum light nonaqueous phase liquids ( LNAPLs ) has emerged as a critical parameter for resolving natural losses of LNAPLs and managing LNAPL sites. Current approaches for resolving CO 2 efflux include gradient, flux chamber, and mass balance methods. Herein a new method for measuring CO 2 efflux above LNAPL bodies, referred to as CO 2 traps, is introduced. CO 2 traps involve an upper and a lower solid phase sorbent elements that convert CO 2 gas into solid phase carbonates. The sorbent is placed in an open vertical section of 10 cm ID polyvinyl chloride ( PVC ) pipe located at grade. The lower sorbent element captures CO 2 released from the subsurface via diffusion and advection. The upper sorbent element prevents atmospheric CO 2 from reaching the lower sorbent element. CO 2 traps provide integral measurement of CO 2 efflux based over the period of deployment, typically 2 to 4 weeks. Favorable attributes of CO 2 traps include simplicity, generation of integral (time averaged) measurement, and a simple means of capturing CO 2 for carbon isotope analysis. Results from open and closed laboratory experiments indicate that CO 2 traps quantitatively capture CO 2 . Results from the deployment of 23 CO 2 traps at a former refinery indicate natural loss rates of LNAPL (measured in the fall, likely concurrent with high soil temperatures and consequently high degradation rates) ranging from 13,400 to 130,000 liters per hectare per year (L/Ha/year). A set of field triplicates indicates a coefficient of variation of 18% (resulting from local spatial variations and issues with measurement accuracy).