USGS Science⌕ Search
Home/Archive/USGS

USGS · 70034714

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

T.D. McCobb·D.R. LeBlanc·A.J. Massey
View original source ↗Export metadata ↓

Abstract

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%.

Explore related subjects

Ground Water Monitoring and RemediationArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

T.D. McCobb, D.R. LeBlanc, A.J. Massey. 2009-05-18. Monitoring the removal of phosphate from ground water discharging through a pond-bottom permeable reactive barrier. https://doi.org/10.1111/j.1745-6592.2009.01235.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2022

Understanding the evolution of groundwater-contaminant plume chemistry emanating from legacy contaminant sources: An example from a long-term crude oil spill

Understanding the evolution of plumes emanating from residual hydrocarbon contaminant sources requires evaluating how changes in source compositions over time cause changes in dissolved plume chemistry as residual sources age. This study investigates such changes at the site of a 1979 crude-oil pipeline spill and is the first comprehensive look at groundwater chemistry associated with a residual hydrocarbon source zones in different stages of aging. The data show a direct relationship between concentrations of benzene and naphthalene in the residual oil and those measured in water samples collected below the oil. Groundwater associated with oil near the spill site had different chemical composition compared with water associated with oil that had spread downgradient from the spill zone, indicating a shift in biodegradation reactions. These results emphasize that source zone processes are spatially and temporally heterogeneous and should be accounted for in natural attenuation studies where residual source zones persist.

Minnesota↗
USGS2019

Examining the extraction efficiency of petroleum-derived dissolved organic matter in contaminated groundwater plumes

The extraction efficiency of petroleum-derived dissolved organic matter (DOM) was examined for groundwater samples from an aquifer contaminated with crude oil. Four different types of extraction were used to determine which method is best suited for the analysis of potentially toxic petroleum-derived DOM. The four types were a liquid-liquid extraction (LLE) with dichloromethane (EPA method 3510C), and three solid-phase extraction (SPE) stationary phases that are routinely used for extraction of polar analytes from water. For the LLE, that is selective for non-polar compounds, the extraction efficiency of petroleum-derived DOM decreased downgradient as the petroleum-derived DOM becomes increasingly polar due to biodegradation. In contrast, the average extraction efficiency by the SPE methods was greater than 65 % across the gradient. The results showed that SPE is more efficient for extracting petroleum-derived DOM at hydrocarbon-contaminated sites. The use of a method with greater extraction efficiency for partially-oxidized hydrocarbons may prove useful in determining relationships between their composition and structure and potential for risks to human health or the environment.

Ground Water Monitoring and Remediation↗
USGS2012

Potentially bioavailable natural organic carbon and hydrolyzable amino acids in aquifer sediments

This study evaluated the relationship between concentrations of operationally defined potentially bioavailable organic -carbon (PBOC) and hydrolyzable amino acids (HAAs) in sediments collected from a diverse range of chloroethene--contaminated sites. Concentrations of PBOC and HAA were measured using aquifer sediment samples collected at six selected study sites. Average concentrations of total HAA and PBOC ranged from 1.96 ± 1.53 to 20.1 ± 25.6 mg/kg and 4.72 ± 0.72 to 443 ± 65.4 mg/kg, respectively. Results demonstrated a statistically significant positive relationship between concentrations of PBOC and total HAA present in the aquifer sediment (p < 0.05). Higher levels of HAA were consistently observed at sites with greater levels of PBOC and first-order decay rates. Because amino acids are known to be readily biodegradable carbon compounds, this relationship suggests that the sequential chemical extraction procedure used to measure PBOC is a useful indicator of bioavailable carbon in aquifer sediments. This, in turn, is consistent with the interpretation that PBOC measurements can be used for estimating the amount of natural organic carbon available for driving the reductive dechlorination of chloroethenes in groundwater systems.

Ground Water Monitoring and Remediation↗