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Monitoring the Removal of Phosphate from Ground Water Discharging through a Pond‐Bottom Permeable Reactive Barrier
Author(s) -
McCobb Timothy D.,
LeBlanc Denis R.,
Massey Andrew J.
Publication year - 2009
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/j.1745-6592.2009.01235.x
Subject(s) - plume , groundwater , transect , suction , flux (metallurgy) , piezometer , hydrology (agriculture) , environmental science , diffusion , pore water pressure , geology , geotechnical engineering , chemistry , aquifer , oceanography , meteorology , physics , organic chemistry , thermodynamics
Installation of a permeable reactive barrier to intercept a phosphate (PO 4 ) plume where it discharges to a pond provided an opportunity to develop and test methods for monitoring the barrier’s performance in the shallow pond‐bottom sediments. The barrier is composed of zero‐valent‐iron mixed with the native sediments to a 0.6‐m depth over a 1100‐m 2 area. Permanent suction, diffusion, and seepage samplers were installed to monitor PO 4 and other chemical species along vertical transects through the barrier and horizontal transects below and near the top of the barrier. Analysis of pore water sampled at about 3‐cm vertical intervals by using multilevel diffusion and suction samplers indicated steep decreases in PO 4 concentrations in ground water flowing upward through the barrier. Samples from vertically aligned pairs of horizontal multiport suction samplers also indicated substantial decreases in PO 4 concentrations and lateral shifts in the plume’s discharge area as a result of varying pond stage. Measurements from Lee‐style seepage meters indicated substantially decreased PO 4 concentrations in discharging ground water in the treated area; temporal trends in water flux were related to pond stage. The advantages and limitations of each sampling device are described. Preliminary analysis of the first 2 years of data indicates that the barrier reduced PO 4 flux by as much as 95%.