Showing papers by "John A. Cherry published in 1997"
TL;DR: The time for disappearance of stationary, single component immiscible-phase liquid (NAPL) from planar fractures due to dissolution and subsequent diffusion is directly dependent on the ratio of mass storage capacity of dissolved and sorbed contaminant in the matrix to the initial storage capacity in the fracture as discussed by the authors.
Abstract: The time for disappearance of stationary, single-component immiscible-phase liquid (NAPL) from planar fractures due to dissolution and subsequent diffusion is directly dependent on the ratio of mass storage capacity of dissolved and sorbed contaminant in the matrix to the initial storage capacity for immiscible-phase liquid in the fracture. This was determined from an analytical evolution for three-dimensional mass transfer into water-saturated matrix blocks of clay or sedimentary rock represented as rectangular parallelepipeds. A ratio greater than one indicates the number of times the fracture void volume can be completely replenished with the immiscible phase before disappearance ceases. However, each successive fracture replenishment requires longer time for disappearance due to consumption of part of the matrix storage capacity caused by previous fracture loadings. Ultimately, with continued NAPL replenishment in the fractures, this mass redistribution causes the dissolved concentration in the matrix to equal the aqueous solubility, at which point continued disappearance cannot occur. Mass storage capacity ratios for matrix and fracture conditions typical of clays and sedimentary rocks are greater than one for a variety of the common chlorinated solvents. The initial disappearance times for a trichloroethylene (TCE) DNAPL in a fractured clay of 10{sup {minus}4} fracture porosity and 35% matrixmore » porosity with parallel, planar fractures, range from 0.01 to 113 days for fracture spacings of 1 cm and 1 m, respectively. Disappearance times for TCE DNAPL are much larger for a generic sandstone with the same fracture porosity and geometry and 10% matrix porosity, and range from 0.44 to 4,400 days, due to reduced storage capacity in the matrix.« less
92 citations
TL;DR: This paper addresses the use of wells for amendment delivery, recognizing the potential utility of amendments such as electron acceptors, electron donors, and microbial nutrients for stimulating bioremediation, and the possible utility of oxidizers, reducers, etc., for controlled abiotic degradation.
Abstract: Arrays of unpumped wells can be used as discontinuous permeable walls in which each well serves both as a means to focus ground water flow into the well for treatment and as a container either for permeable reactive media which directly destroy dissolved ground water contaminants or for devices or materials which release amendments that support in situ degradation of contaminants within the aquifer downgradient of the wells. This paper addresses the use of wells for amendment delivery, recognizing the potential utility of amendments such as electron acceptors (e.g., oxygen, nitrate), electron donors (primary substrates), and microbial nutrients for stimulating bioremediation, and the potential utility of oxidizers, reducers, etc., for controlled abiotic degradation. Depending on its rate and constraints, the remedial reaction may occur within the well and/or downgradient. For complete remediation of ground water passing through the well array; the total flux of amendment released must meet or exceed the total flux demand imposed by the plume.
40 citations
TL;DR: In this article, a series of six ancient connected lakes occupied the broad plain of the closed Basin of Mexico and the pore water of the broad aquitard formed from sediment in these lakes indicate that the origin of this paleo-lake water was local meteoric water, which entered the ancient lakes as runoff, and groundwater from springs.
40 citations
31 Dec 1997
TL;DR: In this paper, the authors evaluated the performance of permeable wall and funnel-and-gate barrier for plume capture in a three-dimensional groundwater flow model and found that the barrier can capture plume in both generic and site-specific hydrogeologic systems.
Abstract: The passive interception and in situ treatment of dissolved contaminants in groundwater by permeable reactive barriers has recently gained favor at an increasing number of sites as an alternative to conventional approaches to groundwater remediation such as the pump-and-treat method. Permeable reactive barriers have two essential functions. The first is that the barriers must be installed in a position such that all of the plume passes through the reactive system. The second function is to achieve acceptable treatment of the contamination by physical, chemical or biological means within or downgradient of the barrier. In this paper, issues associated with the hydraulic performance of permeable reaction barriers are evaluated using a three-dimensional groundwater flow model. The efficiency of plume capture by permeable wall and funnel-and-gate systems is examined for some generic and for site-specific hydrogeologic systems. The results have important implications to decisions pertaining to the selection, design and installation of permeable reactive barrier systems.
10 citations
31 Dec 1997
TL;DR: In this article, a series of laboratory tests and small scale field trials were initiated to test the performance of an innovative permeable reactive barrier for treatment of nitrate from septic systems, which promotes denitrification by providing an energy source in the form of solid organic carbon mixed into the porous media material.
Abstract: Beginning in 1991 a series of laboratory tests and small scale field trials were initiated to test the performance of an innovative permeable reactive barrier for treatment of nitrate from septic systems. The barrier promotes denitrification by providing an energy source in the form of solid organic carbon mixed into the porous media material. Advantages of the system for nitrate treatment are that the reaction is passive and in situ and it is possible to incorporate sufficient carbon mass in conveniently sized barriers to potentially provide treatment for long periods (decades) without the necessity for maintenance. However, longevity can only be demonstrated by careful long term monitoring of field installations. This paper documents four years of operating history at three small scale field trials; two where the denitrification barrier is installed as a horizontal layer positioned in the unsaturated zone below conventional septic system infiltration beds and one where the barrier is installed as a vertical wall intercepting a septic system plume at a downgradient location. The barriers have successfully attenuated 50-100% of NO{sup -}{sub 3}-N levels of up to 170 mg/L and treatment has remained consistent over the four year period in each case, thus considerable longevity is indicated.more » Other field trials have demonstrated this technology to be equally effective in treating nitrogen contamination from other sources such as landfill leachate and farm field runoff.« less
7 citations
31 Dec 1997
TL;DR: In this paper, the authors give preliminary results of research into methods to emplace granular iron at depths in the range of 15 to 60 m. The study included review of available and emerging methods of installing barrier or reactive material and the selection, preliminary design and costing of several methods.
Abstract: Some groundwater plumes containing chlorinated solvent contaminants are found to be so deep that current in situ remediation technologies cannot be economically applied. Also, source zones are often found to be too deep for removal or inaccessible due to surface features. Plumes emanating from these sources require containment or treatment. Containment technologies are available for shallow sites (< 15 m) and are being developed for greater depths. However, it is important to advance the science of reactive treatment - both for cut off of plumes and to contain and treat source zones. Zero-valent metal technology has been used for remediation of solvent plumes at sites in Canada, the UK and at several industrial and military sites in the USA. To date, all of the plumes treated with zero-valent metal (granular iron) have been at depths less than 15 m. This paper gives preliminary results of research into methods to emplace granular iron at depths in the range of 15 to 60 m. The study included review of available and emerging methods of installing barrier or reactive material and the selection, preliminary design and costing of several methods. The design of a treatment system for a 122 m wide PCE plumemore » that, immediately down gradient from its source, extends from a depth of 24 to 37 m below the ground surface is used as a demonstration site. Both Permeable Reactive Wall and Funnel-and-Gate{trademark} systems were considered. The emplacement methods selected for preliminary design and costing were slurry wall, driven/vibrated beam, deep soil mixing and hydrofracturing injection. For each of these methods, the iron must be slurried for ease of pumping and placement using biodegradable polymer viscosifiers that leave the iron reactive.« less
6 citations