Comparison of Temporal Trends in VOCs as Measured with PDB Samplers and Low‐Flow Sampling Methods

Harte, Philip T.

doi:10.1111/j.1745-6592.2002.tb00311.x

Cited by 9 publications

(6 citation statements)

References 2 publications

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“…This can be confirmed by comparing concentrations in samples collected with passive samplers and purging methods in the same well. Harte (2002) found close agreement of tetrachloroethene concentrations measured in wells in very permeable sand-and-gravel glacial deposits using PDB passive samplers and purging.…”

Section: Geologic Formationsupporting

confidence: 58%

“…Sampling approach: Sampler type: (1) Passive diffusion bag (PDB); (2) Deployment in the well: Multiple samplers, uniformly spaced in the fully penetrating well screen; (3) Deployment duration: 2-3 weeks. Performance assessment: Concurrent low-flow samples at coincident depths were collected from a subset of wells, as reported in Harte and others (2001) and Harte (2002) The adjusted concentration of U for passive sampling shows small variations at two of the wells profiled (wells ND and Q; table 2.1) and larger variations at four of the wells (wells MV, DD, DD2, T11; table 2.1), as identified by the relative magnitude of the standard deviation of U concentrations from the passive samplers. Well T11 had the highest mean U concentration and largest standard deviation from the profile of passive samplers and is at the large tailings pile ( fig.…”

Section: Appendix a Case Studiesmentioning

confidence: 99%

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Passive sampling of groundwater wells for determination of water chemistry

Imbrigiotta¹,

Harte²

2020

Techniques and Methods

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A series of nylon screen samplers retrieved from a profile of the water column of a well showing capped bottles and the removed tops. The variation of iron-staining on the removed tops indicates stratified flow with different redox conditions occurs under ambient flow conditions in the well. Photograph by Philip T. Harte, U.S. Geological Survey. (F) Figure 5A from report, a polyethylene diffusion bag sampler. Photograph by Bradley P. Varhol, EON Products, Inc. (G) Figure 9 from report, a rigid porous polyethylene sampler, without protective mesh and with protective mesh, in a water-filled tube for shipment. Photographs by Leslie Venegas, ALS Global. (H) Figure 13A from report, QED Environmental Systems, Inc. Snap Sampler® with volatile organic compound bottle (40-milliliter vial). Photograph by Sanford Britt, QED Environmental Systems, Inc.

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Section: Geologic Formationsupporting

confidence: 58%

Section: Appendix a Case Studiesmentioning

confidence: 99%

Passive sampling of groundwater wells for determination of water chemistry

Imbrigiotta¹,

Harte²

2020

Techniques and Methods

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“…However, as pointed out in a previous Ground Water Monitoring and Remediation editorial and subsequent discussions (Barcelona 2000a;Hare et al 2000;Barcelona 2000b;Harte 2002), several important considerations and limitations for PD sampler use have not been thoroughly investigated in the peer-reviewed literature, and relatively few field data sets have been presented. Where field data are available, PD sampler performance has primarily been evaluated at sites with fairly simple geologic and hydrostratigraphic conditions.…”

Section: Introductionmentioning

confidence: 99%

Passive diffusion ground water samplers at a site with heterogeneous hydrostratigraphy: Pilot study results

Divine¹,

Madsen²,

Andrews³

et al. 2005

Groundwater Monitoring Rem

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Use of passive diffusion (PD) ground water samplers has significantly increased in recent years because significant cost savings may be realized, primarily because sampling time is reduced and minimal investigation‐derived waste (IDW) is generated. However, PD samplers measure water quality over a relatively discrete interval, while traditional purge‐and‐sample methods are most influenced by the water quality in more permeable zones across the well screen. Consequently, these two sampling methods may potentially yield distinctly differing concentration measurements for a specific well if significant contaminant stratification and geologic heterogeneity exist. A large body of purge‐and‐sample historical monitoring data exist for the study site, and results from potential future full‐scale PD sampler application must be interpretable and comparable in the context of these historical data to be useful for evaluating achievement of long‐term site remediation objectives. Therefore, a pilot study was conducted to assess potential for PD samplers for monitoring chlorinated volatile organic compounds (VOCs) in ground water. PD samplers were installed in a select group of indicator wells, and their performance was compared to results from both purge‐and‐sample and low‐flow (LF; another discrete interval–type technique) methods. At several wells, multiple PD samplers were installed across the well screen interval to evaluate potential contaminant stratification. At one well, contaminant stratification was particularly significant: concentrations of total VOCs measured by two PD samplers installed ∼0.6 m (2 feet) apart differed by an order of magnitude. PD sampler and LF data interpreted in tandem with purge‐and‐sample data provide additional information, suggesting that contamination is located primarily in the more permeable zones at the study well locations. Additionally, low concentrations of some VOCs were measured in some PD and LF samples but not in the corresponding purge‐and‐bail samples. The results of this study underscore the importance of pilot studies and careful program design and regulatory agreement before implementing PD samplers (or any alternative sampling method) in a long‐term monitoring program, especially at sites with heterogeneous hydrostratigraphy.

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“…Vertical chemical profiling of CVOCs and other volatile organics of groundwater in wells BBC3 and BBC4 was performed for this study using passive diffusion bag (PDB) samplers (Harte, 2002;Harte, Brayton, & Ives, 2000). Multiple PDB samplers were deployed at different depths in the open borehole based on the interpretation of likely flow zones from the previously collected borehole geophysical log results (Bothner et al, 2010) Reston, Virginia, using gas chromatography procedures (Busenberg, Plummer, Bartholomay, & Wayland, 1998).…”

Section: Methodsmentioning

confidence: 99%

Borehole‐scale testing of matrix diffusion for contaminated‐rock aquifers

Harte

Brandon

2020

Remediation Journal

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A new method was developed to assess the effect of matrix diffusion on contaminant transport and remediation of groundwater in fractured rock. This method utilizes monitoring wells constructed of open boreholes in the fractured rock to conduct backward diffusion experiments on chlorinated volatile organic compounds (CVOCs) in groundwater. The experiments are performed on relatively unfractured zones (called test zones) of the open boreholes over short intervals (approximately 1 meter) by physical isolation using straddle packers. The test zones were identified with a combination of borehole geophysical logging and chemical profiling of CVOCs with passive samplers in the open boreholes. To confirm the test zones are within inactive flow zones, they are subjected to a series of hydraulic tests. Afterward, the test zones are air sparged with argon to volatilize the CVOCs from aqueous to air phase. Backward diffusion is then measured by periodic passive‐sampling of water in the test zone to identify rebound. The passive (nonhydraulically stressed) sampling negates the need to extract water and potentially dewater the test zone. The authors also monitor active flowing zones of the borehole to assess trends in concentrations in other parts of the fractured rock by purge and passive sampling methods. The testing was performed at the former Pease Air Force Base (PAFB) in Portsmouth, New Hampshire. Bedrock at the former PAFB consists of fractured metasedimentary rocks where the authors investigated back diffusion of cis‐1,2‐dichloroethylene (cis‐1,2‐DCE), a CVOC. Postsparging concentrations of cis‐1,2‐DCE showed initial rebounding followed by declines, excluding an episodic spike in concentrations from a groundwater recharge event. The authors theorize that there are three processes that controlled concentration responses in the test zones postsparging. First, the limited back diffusion of CVOCs from a halo or thin zone of rock around the borehole contributes to the initial rebounding. Second, aerobic degradation of cis‐1,2‐DCE occurred causing declines in concentrations in the test zone. Third, microflow from microfractures contributed to the episodic spike in concentrations following the groundwater recharge event. In active flow zones, the latter two processes are not measurable due to equilibration from groundwater transport between the borehole and active flowing fractures.

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Comparison of Temporal Trends in VOCs as Measured with PDB Samplers and Low‐Flow Sampling Methods

Cited by 9 publications

References 2 publications

Passive sampling of groundwater wells for determination of water chemistry

Passive sampling of groundwater wells for determination of water chemistry

Passive diffusion ground water samplers at a site with heterogeneous hydrostratigraphy: Pilot study results

Borehole‐scale testing of matrix diffusion for contaminated‐rock aquifers

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