Natural gradient tracer test to evaluate natural attenuation of MTBE under anaerobic conditions

Illa Amerson, Richard Johnson

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

A natural gradient tracer test using perdeuterated MTBE was conducted in an anaerobic aquifer to determine the relative importance of dispersion and degradation in reducing MTBE concentrations in ground water. Preliminary ground water chemistry and hydraulic conductivity data were used to place the tracer within an existing dissolved MTBE plume at Port Hueneme, California. Following one year of transport, the tracer plume was characterized in detail. Longitudinal dispersion was identified as the dominant mechanism for lowering the perdeuterated MTBE concentrations. The method of moments was used to determine the longitudinal and lateral dispersion coefficients (0.85 m2/day and 0.08 m2/day, respectively). A mass-balance analysis, carried out after one year of transport, accounted for 110% of the injected mass and indicated that no significant mass loss occurred. The plume structure created by zones of higher and lower hydraulic conductivity at the site was complex, consisting of several localized areas of high tracer concentration in a lower concentration plume. This is important because the aquifer has generally been characterized as exhibiting fairly minor heterogeneity. In addition, the tracer plume followed a curved flowpath that deviated from the more macroscopic direction of ground water flow inferred from local ground water elevation measurements and the behavior of the existing plume. Understanding the mass balance, plume structure, curvature of the tracer plume, and consequently natural attenuation behavior required the detailed sampling approach employed in this study. These data imply that a detailed understanding of site hydrogeology and an extensive sampling network may be critical for the correct interpretation of monitored natural attenuation of MTBE.

Original languageEnglish (US)
Pages (from-to)54-61
Number of pages8
JournalGround Water Monitoring and Remediation
Volume23
Issue number1
StatePublished - Dec 2002

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Natural attenuation
MTBE
natural attenuation
anoxic conditions
Groundwater
plume
tracer
Hydraulic conductivity
Aquifers
Sampling
Hydrogeology
Groundwater flow
Method of moments
groundwater
hydraulic conductivity
Degradation
mass balance
aquifer
test
sampling

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

Natural gradient tracer test to evaluate natural attenuation of MTBE under anaerobic conditions. / Amerson, Illa; Johnson, Richard.

In: Ground Water Monitoring and Remediation, Vol. 23, No. 1, 12.2002, p. 54-61.

Research output: Contribution to journalArticle

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