Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier

McCobb, T. D.; LeBlanc, D. R.; Massey, A. J.

Abstract:

Installation of a permeable reactive barrier to intercept a phosphate (PO₄) 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-m² 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 PO₄ concentrations in ground water flowing upward through the barrier. Samples from vertically aligned pairs of horizontal multiport suction samplers also indicated substantial decreases in PO₄ 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 PO₄ 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 PO₄ flux by as much as 95%. ?? 2009 National Ground Water Association.

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Article

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70034714

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McCobb, T. D.; LeBlanc, D. R.; Massey, A. J.

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English

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Ground Water Monitoring and Remediation

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Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier; 2009; Article; Journal; Ground Water Monitoring and Remediation; McCobb, T. D.; LeBlanc, D. R.; Massey, A. J.