Stratigraphic Trapping of Spilled Jet Fuel Beneath the Water Table

Environmental conditions and the initial attempt to recover JP-4 jet fuel from a shallow aquifer at a tank farm in Hanahan, South Carolina, in 1975. allowed the jet fuel to become stratigraphically trapped below the water table. The trapped jet fuel remained an undetected source of dissolved hydrocarbon contamination in shallow ground water in the area for 17 years. The trapped jet fuel was located when a variety of chemical, hydrologic. geologic, and historical evidence led investigators to install and sample deeper wells. These findings emphasize the need to use an integrated approach lo evaluating the data when determining the extent of contamination and planning fuel recovery operations in a lithologically heterogeneous aquifer.     

Tracing coalbed natural gas-coproduced water using stable isotopes of carbon

Recovery of hydrocarbons commonly is associated with coproduction of water. This water may be put to beneficial use or may be reinjected into subsurface aquifers. In either case, it would be helpful to establish a fingerprint for that coproduced water so that it may be tracked following discharge on the surface or reintroduction to geologic reservoirs. This study explores the potential of using δ¹³C of dissolved inorganic carbon (DIC) of coalbed natural gas (CBNG)–coproduced water as a fingerprint of its origin and to trace its fate once it is disposed on the surface. Our initial results for water samples coproduced with CBNG from the Powder River Basin show that this water has strongly positive δ¹³C_DIC (12‰ to 22‰) that is readily distinguished from the negative δ¹³C of most surface and ground water (−8‰ to −11‰). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high δ¹³C and DIC concentrations allow us to identify surface and ground water that have incorporated CBNG-coproduced water. Accordingly, we suggest that the δ¹³C_DIC and DIC concentrations of water can be used for long-term monitoring of infiltration of CBNG-coproduced water into ground water and streams. Our results also show that the δ¹³C_DIC of CBNG-coproduced water from two different coal zones are distinct leading to the possibility of using δ¹³C_DIC to distinguish water produced from different coal zones.     

An assessment of aquifer storage recovery using ground water flow models

Owing to increased demands on ground water accompanied by increased drawdowns, technologies that use recharge options, such as aquifer storage recovery (ASR), are being used to optimize available water resources and reduce adverse effects of pumping. In this paper, three representative ground water flow models were created to assess the impact of hydrogeologic and operational parameters/factors on recovery efficiency of ASR systems. Flow/particle tracking and solute transport models were used to track the movement of water during injection, storage, and recovery. Results from particle tracking models consistently produced higher recovery efficiency than the solute transport models for the parameters/properties examined because the particle tracking models neglected mixing of the injected and ambient water. Mixing between injected and ambient water affected recovery efficiency. Results from this study demonstrate the interactions between hydrogeologic and operational parameters on predictions of recovery efficiency. These interactions are best simulated using coupled numerical ground water flow and transport models that include the effects of mixing of injected water and ambient ground water.     

Remediation of Contaminated Ground Water Using Biological Techniques

On-site biological cleanup following spills of biodegradable hazardous organic compounds in lagoon, soil, and ground water environments is a cost-effective technique when proper engineering controls are applied. Biodegradation of hazardous organic contaminants by microorganisms minimizes liability by converting toxic reactants into harmless end products.
Three case histories presented in this paper detail:
• Bench-scale evaluation of the potential for biological remediation in the spill site matrix
• Field implementation of biological treatment techniques.
Cost-effectiveness, minimal disturbance to existing operations, and on-site destruction of spilled contaminants are several of the advantages identified for implementing biodegradation as a technique for spill cleanup and environmental restoration.     

Evidence for Enhanced Mineral Dissolution in Organic Acid-Rich Shallow Ground Water

Total concentrations of formate, acetate, and isobutyrate varied from less than 5 to greater than 9,000 μmol/l over distances of < 3 m in ground water from a shallow hydrocarbon contaminated aquifer. Laboratory incubations of aquifer material indicate that organic acid concentrations were dependent on the amount of hydrocarbon loading in the sediment and the relative rates of microbial organic acid production and consumption. In heavily contaminated sediments, production greatly exceeded consumption and organic acid concentrations increased. In lightly contaminated sediments rates were essentially equal and organic acid concentrations remained low. Concentrations of dissolved calcium, magnesium, and iron generally were one to two orders of magnitude higher in organic acid-rich ground water than in ground water having low organic acid concentrations. Carbonate and Fe(III)-oxyhydroxide minerals were the likely sources of these elements. Similarly, concentrations of dissolved silica, derived from quartz and k-feldspar, were higher in organic acid-rich ground water than in other waters. The positive relation (r = 0.60, p < .05, n = 16) between concentrations of silica and organic acids suggests that the microbially mediated buildup of organic acids in ground water enhanced quartz/k-feldspar dissolution in the aquifer, although it was not the only factor influencing their dissolution. A model that included organic acid microequivalents normalized by cation microequivalents significantly strengthened the correlation (r = 0.79, p < .001, n = 16) between dissolved silica and organic acid concentrations, indicating that competition between silica and cations for complexation sites on organic acids also influenced quartz/k-feldspar dissolution. Physical evidence for enhanced mineral dissolution in organic acid-rich waters included scanning electron microscopy images of highly corroded quartz and k-feldspar grains from portions of the aquifer containing organic acid-rich ground water. Microporosity generated in hydrocarbon contaminated sediments may adversely affect remediation efforts that depend on the efficient injection of electron acceptors into an aquifer or on the recovery of solutes from an aquifer.     

The Potential Use of Bali Wastewater for Crop Production Based on Moscow Region Experience

The article offers a new approach to the selection of a treatment plant, based on the optimization of biogeochemical matter flows. The existing treatment facilities of Bali are analyzed. The authors propose several process schemes for domestic wastewater treatment, depending on the technology of utilization of biogenic elements from the wastewater for agricultural production. These are based on water treatment technologies that have been in use in Moscow for more than 100 years.     

Multiport Sock Samplers: A Low-Cost Technology for Effective Multilevel Ground Water Sampling

The importance of obtaining depth-specific ground water samples is now well recognized among practitioners and scientists alike. Many methods and technologies are available for level discrete or depth-specific ground water sampling in consolidated aquifers. All methods have their associated advantages and drawbacks, however. One common disadvantage is that they are expensive. A large number of point discrete ground water samples were required for a UK research project aimed at quantifying natural attenuation processes in ground water contaminated by a former coal carbonization plant. Based on experience from a previous project to develop novel level accurate sampling methodologies for use in existing boreholes, the Ground Water Protection and Restoration Research Unit (GWPRRU) produced and tested a low-cost design multiport sock sampler for ground water monitoring. The sock sampler design allowed the recovery of multiple depth-specific ground water samples from depths of 150 feel (45 m) from individual boreholes in the sandstone aquifer at the field site. Because of their use of inexpensive materials, simple design, installation and use that does not require gravel packs, packers, or grouting, sock samplers were found to be the most cost effective, convenient, and reliable method of obtaining multiple depth-specific ground water samples at the project field site.     

Effects of a Dual‐Pump Crude‐Oil Recovery System,Bemidji, Minnesota,USA

A crude‐oil spill occurred in 1979 when a pipeline burst near Bemidji, MN. In 1998, the pipeline company installed a dual‐pump recovery system designed to remove crude oil remaining in the subsurface at the site. The remediation from 1999 to 2003 resulted in removal of about 115,000 L of crude oil, representing between 36% and 41% of the volume of oil (280,000 to 316,000 L) estimated to be present in 1998. Effects of the 1999 to 2003 remediation on the dissolved plume were evaluated using measurements of oil thicknesses in wells plus measurements of dissolved oxygen in groundwater. Although the recovery system decreased oil thicknesses in the immediate vicinity of the remediation wells, average oil thicknesses measured in wells were largely unaffected. Dissolved‐oxygen measurements indicate that a secondary plume was caused by disposal of the pumped water in an upgradient infiltration gallery; this plume expanded rapidly immediately following the start of the remediation in 1999. The result was expansion of the anoxic zone of groundwater upgradient and beneath the existing natural attenuation plume. Oil‐phase recovery at this site was shown to be challenging, and considerable volumes of mobile and entrapped oil remain in the subsurface despite remediation efforts.     

Evaluation of Hydrogeo-chemical Conditions for Development of Nuclear Criticality in Low-Level Waste Disposal Facilities

The under ground disposal of fissile isotope-bearing wastes poses some unique issues. Specifically, radionuclides such as ²³⁵U disposed in low-level waste facilities, if present in the correct concentration and geometry, can create a nuclear criticality event that releases radioactivity to ground water. This paper reports the results of a study of the potential for ²³⁵U to be transported by ground water within low-level waste facilities and to concentrate to form a critical mass. Coupled hydrologic and geochemical modeling was used to investigate two possible mechanisms for concentrating mobile uranium: sorption on high capacity sites and precipitation in a reducing zone. The hydrogeochemical modeling showed that (1) it is difficult to mobilize uranium from sorption sites then re-deposit it; (2) if uranium is already in solution it can accumulate in zones of high sorption, and (3) reducing zones can accumulate sufficient uranium in the presence of oxygenated ground water. Site-specific disposal practices, such as the commingling of large quantities of depleted (nonfissile) uranium and the difficulty of bringing sufficient mass together in the correct geometry, limit the potential for criticality safety concerns. In order to determine appropriate disposal practices, hydrogeochemical modeling can be used to study the future mobility and accumulation of the waste.     

Aquifer Classification for the UIC Program: Prototype Studies in New Mexico

Three case studies from New Mexico illustrate methods by which aquifers can be classified for purposes of the Federal Underground Injection Control program. The principal technique involves preparation of hydrogeologic maps or cross sections which display information on the permeability of rock units and the dissolved solids content of formation fluids. Because deep water wells are lacking in most areas, the analysis normally requires considerable interpretation of geological and geophysical logs collected by energy and mineral companies, plus use of a general model or concept about regional hydrogeology. Injection of waste fluids into aquifers containing water with less than 10,000 mg/1 dissolved solids is not allowed unless an exemption is justified by economic, engineering and other factors. Based on the case studies, regulatory exemptions will be possible for aquifers which are hydrocarbon or mineral-producing, or which are important for brine disposal purposes.     

Field Methods for Measurement of Ground Water Redox Chemical Parameters

An inexpensive, versatile, and portable system is presented, which facilitates rapid field determinations of redox potentials, pH, conductivity, ferrous and total iron, nitrite, specific conductance, dissolved oxygen, and temperature. Accuracy is facilitated by on-site measurements of most parameters using specially constructed flow-through cells and, for several analyses, sealed reagent ampoules, which can be broken and developed inside a flowing stream of ground water. Coupled with laboratory analyses of more stable ground water parameters, this system can provide accurate and relatively inexpensive determinations of redox conditions in ground water.     

Vadose zone-attenuated artificial recharge for input to a ground water model

Accurate representation of artificial recharge is requisite to calibration of a ground water model of an unconfined aquifer for a semiarid or arid site with a vadose zone that imparts significant attenuation of liquid transmission and substantial anthropogenic liquid discharges. Under such circumstances, artificial recharge occurs in response to liquid disposal to the vadose zone in areas that are small relative to the ground water model domain. Natural recharge, in contrast, is spatially variable and occurs over the entire upper boundary of a typical unconfined ground water model. An improved technique for partitioning artificial recharge from simulated total recharge for inclusion in a ground water model is presented. The improved technique is applied using data from the semiarid Hanford Site. From 1944 until the late 1980s, when Hanford's mission was the production of nuclear materials, the quantities of liquid discharged from production facilities to the ground vastly exceeded natural recharge. Nearly all hydraulic head data available for use in calibrating a ground water model at this site were collected during this period or later, when the aquifer was under the diminishing influence of the massive water disposals. The vadose zone is typically 80 to 90 m thick at the Central Plateau where most production facilities were located at this semiarid site, and its attenuation of liquid transmission to the aquifer can be significant. The new technique is shown to improve the representation of artificial recharge and thereby contribute to improvement in the calibration of a site-wide ground water model.     

Sources of ground water salinity on islands using 18O, 2H, and 34S

Stable isotopes of 18O and 2H in water, and 34S and 18O in dissolved SO4, are used to verify the interpretation of the chemical evolution and proposed sources of salinity for two islands that have undergone postglacial rebound. Results for delta18O and delta34S in dissolved SO4 on the Gulf Islands, southwest British Columbia, Canada, suggest a three-component mixing between (1) atmospheric SO4 derived largely from recharge of meteoric origin, (2) modern marine SO4 associated with either modern-day salt water intrusion or Pleistocene age sea water, and (3) terrestrial SO4. The age of the marine SO4 is uncertain based on the geochemistry and SO4 isotopes alone. Two options for mixing of saline ground waters are proposed--either between current-day marine SO4 and atmospheric SO4, or between older (Pleistocene age) marine SO4 and atmospheric SO4, delta18O and delta2H compositions are relatively consistent between both islands, with a few samples showing evidence of mixing with water that is a hybrid mixture of Fraser River water and ocean water. The isotopic composition of this hybrid water is approximately delta18O = 10 per thousand. delta18O and delta2H values for many saline ground waters plot close to the global meteoric water line, which is distinctly different from the local meteoric water line. This suggests a meteoric origin for ground waters that is different from the current isotopic composition of meteoric waters. It is proposed these waters may be late Pleistocene in age and were recharged when the island was submerged below sea level and prior to rebound at the end of the last glaciation.     

Isotopes and sustainability of ground water resources, North China Plain

Ground water in deep confined aquifers is one of the major water resources for agricultural, industrial, and domestic uses in the North China Plain. Detailed information on ground water age and recharge is vital for the proper management of these water resources, and to this end, we used carbon 14 of dissolved inorganic carbon and tritium in water to measure the age and determine the recharge areas of ground water in the North China Plain. These isotopic data suggest that most ground water in the piedmont part of the North China Plain is <40 years old and is recharged locally. In contrast, ground water in the central and littoral portions of the North China Plain is 10,000 to 25,000 years old. The delta18O (deltaD) values of this ground water are 1.7 per thousand (11 per thousand) less than that in the piedmont plain ground water and possibly reflect water recharged during a cooler climate during the last glaciation. The temperature of this recharge, based on delta18O values, ranges from 3.7 degrees C to 8.4 degrees C, compared to 12 degrees C to 13 degrees C of modern recharge water. The isotopic data set combined indicates that ground water in the central and littoral part of the North China Plain is being mined under non-steady state conditions.     

Aquifer Storage and Recovery Using Saline Aquifers: Hydrogeological Controls and Opportunities

Aquifer storage and recovery (ASR) is a valuable tool for managing variations in the supply and demand of freshwater, but system performance is highly dependent upon system-specific hydrogeological conditions including the salinity of the storage-zone native groundwater. ASR systems using storage zones containing saline (>10,000 mg/L of total dissolved solids) groundwater tend to have relatively low recovery efficiencies (REs). However, the drawbacks of low REs may be offset by lesser treatment requirements and may be of secondary importance where the stored water (e.g., excess reclaimed, surface, and storm waters) would otherwise go to waste and pose disposal costs. Density-dependent, solute-transport modeling results demonstrate that the RE of ASR systems using a saline storage zone is most strongly controlled by parameters controlling free convection (e.g., horizontal hydraulic conductivity) and mixing of recharged and native groundwater (e.g., dispersivity and aquifer heterogeneity). Preferred storage zone conditions are moderate hydraulic conductivities (5 to 20 m/d), low degrees of aquifer heterogeneity, and primary porosity-dominated siliclastic and limestones lithologies with effective porosities greater than 5%. Where hydrogeological conditions are less favorable, operational options are available to improve RE, such as preferential recovery from the top of the storage zone. Injection of large volumes of excess water currently not needed into saline aquifers could create valuable water resources that could be tapped in the future during times of greater need.     

Vadose Zone Monitoring: An Early Warning System

Currently, vadose zone monitoring is required under the Resource Conservation and Recovery Act (RCRA) only at land treatment facilities. Contaminant leak detection through ground water monitoring is very important, but it is considered to be after the fact. Remedial action costs can be reduced considerably by monitoring the vadose zone for compounds that exhibit high rates of movement. Volatile organic compounds (VOCs) exhibit this property and are present at many municipal landfills, recycling facilities, and treatment storage and disposal facilities (TSDFs). Through the authors'personal experience, it has been noted that gaseous phase transport of VOCs through the vadose zone is at least an order of magnitude greater than advective transport of VOCs in ground water. Therefore, VOCs in soil gas are an effective early warning leak detection parameter. Downward movement of leachate can be intercepted by porous cup lysimeters. Attenuation in the vadose zone slows the apparent movement of contaminants; however, it is only a matter of time before leachate reaches the water table. The authors believe that soil-gas and pore-water monitoring should and eventually will be required at all RCRA sites. If vadose zone monitoring becomes an additional requirement under RCRA, both the facility owner and the taxpayer will benefit. During the interim, facility owners can benefit by employing vadose zone monitoring techniques coupled with either qualitative or quantitative chemical analyses.     

Dynamics and stable isotope composition of gaseous and dissolved oxygen

The vadose zone and ground water environments are a sink for atmospheric O(2). The pathways and rates of O(2) consumption are primarily related to the availability and rate of oxidation of key reductants (e.g., organics, sulfides), through a combination of biological or abiotic reactions. The range in delta(18)O of O(2) in the subsurface is large, from +20 per thousand to +39 per thousand (Vienna Standard Mean Ocean Water) in the vadose zone and from +12 per thousand to +46 per thousand in ground water. The aggregated O(2) isotope fractionation by consumption (alpha(k)) was found to range from 0.970 to 1.300 and 0.980 to 1.030 in vadose zones and aquifers, respectively. These data suggest the delta(18)O patterns in both unsaturated zones and aquifers can be attributed to microbially mediated reactions (alpha(k)= range from 0.975 to 1.000), but there are apparently other inverse isotope fractionating processes (alpha(k) > 1.000). Circumstantial evidence suggested O(2) processed during the sulfide oxidation and precipitation of Fe-oxyhydroxides process (or other unidentified processes) could be the cause of the significant (18)O depletions. Overall, delta(18)O data from vadose zones and ground water revealed that isotope fractionation by consumption of gaseous and dissolved O(2) in the subsurface and ground water environments is more complicated than what has classically been attributed solely to geomicrobial respiration. Given the questions and inexplicable data arising from this study, further detailed research on O(2) consuming processes in the Earth's subsurface and ground water is warranted.     

Investigation of Possible Contamination of Shallow Ground Water by Deeply Injected Liquid Industrial Wastes

The objective of this study was to assess the possible impact of deep well disposal operations, conducted between 1958 and 1974, on the ground water quality in a shallow fresh water aquifer beneath Sarnia, Ontario, Canada. Because of the breakout of formation fluids in Sarnia and Port Huron, Michigan, in the early 1970s, it had been hypothesized that liquid waste from the disposal zone in bedrock had leaked through numerous abandoned oil, gas, and salt wells in the area up to the shallow fresh water aquifer and from there to the surface.
A monitoring well network of 29 5cm (2 inch) diameter piezometers was established in the thin sand and shale aquifer system, which exists between 30 and 70m (100 and 230 feet) below ground surface. In addition, a 300m (1000 foot) deep borehole was drilled and instrumented with a Westbay multilevel casing, which permitted sampling of the disposal zone.
Ground water samples from the shallow monitoring wells and the Westbay multilevel casing were analyzed for volatiles by GC/MS. Those volatile aromatics that were conspicuously present in the deep disposal zone, e.g., ethyl toluenes and trimethyl benzene, were not detected in the shallow monitoring wells. Thus, if contaminants from the disposal zone did indeed migrate to the shallow aquifer, contamination was not widespread and probably consisted mostly of displaced chloride-rich formation waters.     

Partitioning of semi-soluble organic compounds between the water phase and oil droplets in produced water

When selecting produced water treatment technologies, one should focus on reducing the major contributors to the total environmental impact. These are dispersed oil and semi-soluble hydrocarbons, alkylated phenols, and added chemicals. Experiments with produced water have been performed offshore on the Statoil operated platforms Gullfaks C and Statfjord B. These experiments were designed to find how much of the environmentally relevant compounds were dissolved in the water phase and not associated to the dispersed oil in the produced water. Results show that the distribution between the dispersed oil and the water phase varies highly for the different components groups. For example the concentration of PAHs and the C6-C9 alkylated phenols is strongly correlated to the content of dispersed oil. Therefore, the technologies enhancing the removal of dispersed oil have a higher potential for reducing the environmental impact of the produced water than previously considered.     

Monitoring Dissolved Oxygen in Ground Water: Some Basic Considerations

Dissolved oxygen (D.O.) concentration has a significant effect upon ground water quality by regulating the valence state of trace metals and by constraining the bacterial metabolism of dissolved organic species. For these reasons, the measurement of dissolved oxygen concentration should be considered essential in most water quality investigations. D.O. measurements have been frequently neglected in ground water monitoring. This is because O₂ has often been assumed absent below the water table; measurement of O₂, concentrations is not mandated by drinking water standards; and the redox potential has previously been considered an adequate and encompassing electrochemical measurement. Redox potentials, however, cannot adequately predict dissolved oxygen concentrations nor can D.O. concentrations be used to calculate redox potentials.
D.O. concentrations can be measured precisely in the field by titration or electrode methods. The best methods of sample recovery are those that use positive pressure displacement devices. A fully adequate sampling procedure will isolate ground water from the atmosphere and will collect samples at restricted depth intervals at ambient temperature and pressure.