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When micro-porous and meso-porous silica particles were exposed to aqueous phenanthrene solutions for various durations it was observed that sorbed-phase phenanthrene concentrations increased with aging time only for meso-porous but not micro-porous silicas. Desorption equilibrium was reached almost instantaneously for the micro-porous particles while both the rate and extent of desorption decreased with increasing aging time for the meso-porous silicas. These findings indicate that phenanthrene can be sequestered within the internal pore-space of meso-porous silicas while the internal surfaces of micro-porous silicas are not accessible to phenanthrene sorption, possibly due to the presence of physi - or chemi-sorbed water that may sterically hinder the diffusion of phenanthrene inside water-filled micro-pores. By contrast, the internal surfaces of these micro-porous silicas are accessible to phenanthrene when incorporation methods are employed which assure that pores are devoid of physi-sorbed water. Cons equently, when phenanthrene was incorporated into these particles using either supercritical CO or via solvent soaking, the aqueous desorption kinetics were extremely slow indicating effective sequestration of phenanthrene inside micro-porous particles. Finally, a two - compartment conceptual model is used to interpret the experimental findings and the implications for contaminant fate and transport are discussed.

The groundwater arsenic poisoning in Bangladesh is the largest disaster in the history of human civilization: more than 100 million people have been drinking arsenic-poisoned water on a daily basis. A large number of scientists believe that the groundwater arsenic poisoning in Bangladesh is a natural disaster, that the poisoning has been present for thousands of years, and that reduction of ancient soil with ferric hydroxide-bearing arsenic is the main mechanism for the mobilization of arsenic into groundwater. However, historical groundwater use data from the dug wells and the tube wells, historical medical data, arsenic toxicological data, hydrological, hydro geological and geochemical parameters reject the reduction hypothesis and suggest that the groundwater arsenic poisoning in Bangladesh is a recent, man-made disaster and that exposure and oxidation of arsenic minerals previously below the water table is probably the principal mechanism for releasing arsenic into groundwater.

The oxidation of arsenic-bearing minerals present in the Bengal delta sediments is responsible for the release of arsenic oxides in solution to the groundwater. The subsequent migration of this arsenic-contaminated groundwater through the upper layers of deltaic sediments is the principal cause of arsenic poisoning in Bangladesh.

Arsenic-bearing minerals of several kinds are associated with the organic-rich sediments present in deltaic environments. Available sources for arsenic are the ocean, coal beds in India, and mountains to the north. Minerals formed in these reducing environments below the groundwater table would be stable unless they were exposed to oxidizing-environments. The groundwater table is lowered by increased irrigation during the dry season and in the cone of depression formed by pumping-tube wells and irrigation wells drilled below the zone of fluctuation. The arsenic minerals in the newly exposed sediments oxidize and release the arsenic when the water table recovers and exposes the oxidized minerals to a reducing-environment.

Increased irrigation did become necessary during India’s 30 years of unilateral diversion of river water from the Ganges, Tista and 28+ common rivers of Bangladesh and India which cut the normal flow of the 30+ rivers during the dry season. The solution to the arsenic problem is to restore the natural river flow of the Ganges, Tista and other common rivers of Bangladesh and India. This would restore the groundwater level to a level that existed in Bangladesh prior to the construction and commission of Farakka Barrage in 1975.

Other man-made environmental disasters created by the Farakka, Tista and other barrages/dams constructed in the common rivers of Bangladesh and India would also be solved if these barrages were removed and a normal flow restored. The riverbeds could then be dredged and groundwater produced at a safe yield rate. A comprehensive plan not only for water supplies but associated waste disposal should be worked out for all of Bangladesh. Individual units within the plan could then be developed on the bases of need and tied into the overall plan as it develops.

This experiment is a comparative study of the efficiency of 12 different extractants in determining the movable and easily assimilated by plants forms of lead and cadmium in a region polluted by the ore mining industry. The main part of both elements is blocked in slightly soluble compounds, and thus they can barely be reached by plants. Both the total quantity and the movable forms of lead and cadmium depend mainly on the possibility of oxidizing processes occurring in the soil and on the transformation of the major pollutants - PbS and CdS in compounds with higher solubility. This leads to their mechanical removal due to their getting into the soil solution or their adsorption and remaining in an exchangeable form in some of the soil components. The concentration of lead and cadmium in the plant species, typical for the investigated region, show that the risk assessment in using soils, contaminated by heavy metals, for agricultural activities cannot be based solely on the data regarding the total amount of these elements. Particularly important is their form, as well as the percentage of exchangeable forms, assimilable by the plants

Road-dust samples were taken from areas of high traffic flows in Irbid City; Jordan. A series of <90, 90-<106, 106-<125, 125-<250, 250-<1000 and 1000-< 2000 µm of road-dust particle size fractions were investigated throughout to evaluate the ratio between metal content in each particle size fraction and total metal content. Atomic absorption spectrometry technique was used throughout. Sequential procedure was used for chemical speciation in road dust samples of <90 µm. This procedure permits a reproducible evaluation of the partitioning of Cu and Zn among the various chemical forms in which they are present in street dust. Two reference standard materials BCR-CRM 142R and NIST-SRM 2709 were tested to validate the propo sed method. Results show that there was no significant difference between the measured values for Cu and Zn and their certified values with RSD of less than 5%.

Modeling of contaminant fate and transport in soils, groundwater, air and other environmental media can be a critical component of permitting, remedial action planning and design, site characterization, and source identification. Modeling of emissions and contamination can result in significant cost-savings as compared with additional sampling and analysis, and is frequently utilized by potentially responsible parties as well as governmental agencies for air permitting, remedial investigations, corrective measures studies, and engineering design. The science of modeling has been challenged in federal and state courtrooms across the country. Questions have been raised as to the reliability, predictability and specificity of contaminant fate and transport modeling by various adversaries, including former operators, neighboring owners, and liability insurers. This paper will discuss the scientific rigors of environmental modeling, its many uses and acceptability within the scientific community, as well as its limitations. The paper will also review and discuss recent court rulings and evidentiary issues regarding contaminant fate and transport modeling in litigation and related expert witness testimony.

The Air Force Center for Environmental Excellence operates several groundwater remediation systems at the Massachusetts Military Reservation (MMR). These systems involve multiple extraction and injection wells designed to provide complete or partial hydraulic containment of contaminant plumes. It is important in the design and optimization of these systems to be able to accurately delineate their hydraulic capture zones, which are three-dimensional and irregularly shaped. Traditional delineation techniques are based on visual identification of the envelope of pathlines leading to the extraction wells, the pathlines being generated by either backward or forward particle tracking in the simulated flow field. A new technique being used at the MMR involves forward tracking of particles from a dense three -dimensional array of starting locations without actually plotting the pathlines. Instead, the particle-tracking outcome is used to define a grid-based three-dimensional continuum of capture parameter, which can then be contoured in two-dimensional projections or otherwise rendered visible by three-dimensional visualization software. The resulting capture parameter is a three-dimensional scalar field that can be considered a quantitative spatial property of the flow regime. It can be combined with other scalar fields defined in the same grid, such as the concentration field, for visualization or for volumetric calculations. Arithmetic comparisons of capture parameter arrays generated at different pumping rates are also useful in sensitivity analysis.

An investigation of groundwater-to-indoor air vapor intrusion of trichloroethylene (TCE) was conducted at a commercial building to 1) identify vapor pathways; 2) measure TCE attenuation; 3) evaluate whether building pressurization can reduce vapor intrusion; and, 4) evaluate seasonal effects on vapor intrusion. The investigation included a site assessment, both indoor and outdoor air sampling, and the modification of the existing heating, ventilation and air-conditioning system. The investigation found that preferential pathways, such as a floor crack, acted as conduits for vapor intrusion when the building was not properly ventilated. The investigation also found that air TCE concentrations were significantly attenuated between ground surface and the breathing zone and proper building pressurization can effectively minimize vapor intrusion. Weather conditions at the site did not significantly affect the indoor air TCE concentrations.

The coastal bend region of South Texas has undergone significant changes in recent times. Increased agricultural activities, industrialization and population growth have enhanced the releases of organic chemicals in South Texas environments. Several classes of organic contaminants have been detected in air, water and sediment samples collected in this region. There is a growing concern that this increased usage may lead to unacceptable exposures and pollute surface-water bodies used for water supply purposes.

Among all the groundwater remediation treatments designed to remove MtBE and other gasoline components, has been widely used since it is one of the best established, econom ical and reliable technologies for the remediation of volatile compounds dissolved in groundwater. However although has been successfully applied at several contaminated sites, the airflow distribution in saturated media and the interactions of various physical, chemical and microbial processes during operations are still not well understood. This experimental study was designed to investigate the effectiveness of in removing dissolved MtBE from a saturated media, performing a removal test under confined and controlled conditions in an intermediate scale tank (m 1 × 1 × 1,2). The experimental conditions focused on the study of the stripping process driven by air injection. Stripping is considered to be the most effective removal process driven by in the initial period of its application. The study confirmed that has significant potential for remediating groundwater contaminated by MtBE, by showing that the stripping action, driven by air injection contributes significantly to the overall removal action of the technology.

The gasoline additive MtBE has become one of the most commonly detected contaminants in groundwater nationwide and has caused much concern in the state of Maine. In 1998 the Maine Department of Human Services conducted a statewide survey of groundwater wells and MtBE was detected in 16% of private and public wells tested. These findings resulted in the state regulatory agencies deciding to opt out of the reformulated gasoline (RFG) program in 1999. Subsequently, the average concentration of MtBE in gasoline dropped from ∼15% to 2% by volume to protect water resources. This major policy change provided a microcosm to study the economic and environmental effects of this gasoline additive. In order to test the effect of this policy on water quality, groundwater samples were analyzed over a period of six years (1998–2003) from 19 wells distributed across a sand and gravel aquifer in Windham, Maine. MtBE continues to occur in detectable concentrations in 30 to 40% of the study wells despite Maine’s decision to opt out of the RFG program in 1999. Although recent detected concentrations are lower than in previous years, this study confirms MtBE’s temporal and spatial persistence in the environment. Reducing MtBE concentrations in gasoline may not be sufficient to eliminate its occurrence in groundwater. The economic perspective is that MtBE increases the cost of groundwater remediation, as compared to MtBE-free gasoline. Economic data for spills are being analyzed to assess if reducing MtBE concentration in gasoline has affected remediation cost. Preliminary results suggest that MtBE increases costs, even when present in low concentrations in gasoline.