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Tracer Method to Determine Residence Time in a Permeable Reactive Barrier
Author(s) -
Bartlett T.R.,
Morrison S.J.
Publication year - 2009
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/j.1745-6584.2009.00544.x
Subject(s) - tracer , residence time (fluid dynamics) , radioactive tracer , radon , zerovalent iron , residence time distribution , chemistry , residence , permeable reactive barrier , groundwater , radioactive decay , environmental science , hydrology (agriculture) , mineralogy , contamination , geology , nuclear physics , adsorption , geotechnical engineering , physics , ecology , demography , sociology , environmental remediation , biology , inclusion (mineral) , organic chemistry
A method is presented to evaluate ground water residence time in a zero‐valent iron (ZVI) permeable reactive barrier (PRB) using radon‐222 ( 222 Rn) as a radioactive tracer. Residence time is a useful indicator of PRB hydraulic performance, with application to estimating the volumetric rate of ground water flow through a PRB, identifying flow heterogeneity, and characterizing flow conditions over time as a PRB matures. The tracer method relies on monitoring the decay of naturally occurring aqueous 222 Rn as ground water flows through a PRB. Application of the method at a PRB site near Monticello, Utah, shows that after 8 years of operation, residence times in the ZVI range from 80 to 486 h and correlate well with chemical parameters (pH, Ca, SO 4 , and Fe) that indicate the relative residence time. Residence times in this case study are determined directly from the first‐order decay equation because we show no significant emanation of 222 Rn within the PRB and no measurable loss of 222 Rn other than by radioactive decay.