Contaminant Leaching

Meima, J. A., Comans, R. N. J. 1998. Application of surface complexadon/precipitation modeling to contaminant leaching from weathered municipal solid waste incinerator bottom ash. Environmental Science and Technology, 32, 688-693. 

A concern raised during full scale operations of the CHEMFIX process was the possibility of contaminant leaching from freshly treated, moist material. During normal processing procedures, treated material would be transferred directly onto the solidification cell. It would be this material that exhibited the potential for contaminant leaching in those 48 hours it took to physically solidify. To determine when the metals were actually bound in the product matrix, a TCLP analysis was done on a series of treated samples over a period of curing times. The results are illustrated in Table 4. 

The data shows an immediate decrease (the difference between untreated and 0 hours after treatment) in the TCLP leachable metals concentration for all seven metals. This indicated that the metals were bound immediately upon being treated. There would be no threat for contaminant leaching during the period it took for the CHEMFIX product to physically solidify. In addition, the TCLP leachable metal concentrations of those samples that were not allowed to cure (0 hours after treatment) all passed the TCLP regulatory limits. Therefore immediately after treatment the material can be classified as non-hazardous. 

Solidification/stabilization is a promising treatment technology for containing and immobilizing dredged material contaminants within a disposal site. While solidification/stabilization is not a solution to every disposal problem, the technology offers improved physical characteristics that reduce the accessibility of water to contaminated solids and reduced leachability for many contaminants. Leaching tests must be able to determine the (a) compounds that can be released from the waste (b) maximum concentration of these compounds in the leachate (c) quantities released per unit mass of waste (d) release rate of these compounds and (e) effects of a co-disposal of the waste. 

Most of the cancers were the same in both genders, but notably only women had elevated incidences of breast cancer and only men had elevated incidences of cancers of the esophagus and bladder. No explanations were offered for these observed differences. The study did not identify specific pollutants, but other studies have shown that typical contaminants leaching out of hazardous waste sites contain large numbers of lipophiles and hydrophiles including organic solvents, pesticides, heavy metals, and other inorganics. 64 ... 

The time required for contaminants leached from the wastes to arrive at some point away from the source may be important under certain circumstances. The rate of water movement provides an estimate of the rate of travel of nonattenuated contaminants. The rate calculation must take into account the pore volume and structure of the geologic materials in which flow occurs. The attenuation characteristics of the geologic materials will retard this rate for a specific contaminant by an amount related to its attenuation factor. This factor is of great importance for wastes that undergo decay or decomposition during flow through a porous medium. 

Leaching of pollutants to ground or surface waters is a major pathway of environmental contamination. Leaching of TCDD from soil containing 8-26,300 ng/g yielded aqueous leachates of... 

The purpose of this chapter is to provide a comprehensive review of water movement in roadways so that this knowledge may be incorporated into fate/ transport models for use in risk assessment. The focus of the chapter is on the environmental impact of leaching of contaminants and aspects of subsurface hydrology as they relate to contaminant leaching. More specifically, the goal of this chapter is to provide answers to the following questions ... 

The volumetric water content in the pavement varies considerably (3-45%) not only because of material or design differences but also because of spatial differences such as lateral variability including edge effects along the shoulders or wheel path location [38,39] or vertical variability [40]. Temporal variabihty of water content in the field in the short term based on precipitation events [41 ] or in the long term based on seasons [42] or time passed after construction [43] has also been reported. The high variabihty in water content indicates that both satirrated and unsaturated conditions occur in the field. Thus, contaminant leaching studies should consider the presence of variably saturated conditions in the field. 

The power of analytical instrumentation currently available makes it possible to detect organic contaminants leached from solid wastes used as road construction and repair (C R) materials at extremely low concentrations. Such low detection limits are essential if contaminants are to be measured with the accuracy and precision required to model their environmental chemodynamic behavior. Most of the work on organic analysis and characterization has resulted from the use of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) [1]. 

Organic contaminants leached from various soHd waste materials (SWMs) used in road construction and repair, discussed in the present chapter, included petroleum hydrocarbons, pesticides, phthalates, phenols, PCBs, organotin compounds, and surfactants. In order to conduct a forensic investigation of these contaminants, it is important that (a) suitable pre-extraction and preservation treatments are implemented for the samples, and (b) specific extraction and/or cleanup techniques for each organic contaminant are carried out prior to the identification and characterization steps. 

Pure copper(II) sulphide membranes were obtained on the way described above evidently show the superiority of this method compared to wet precipitation one as the latter leads to nonsoichiometric, contaminated, leaching, porous or occasionally inactive copper(II) membranes. ... 

The sorption to soil components is a determinant factor for the mobility of contaminants, accounting for their distribution among soil, sediment and water phases. The extent to which chemicals partition between the solid and solution phases in soil, or between water and sediment in aquatic ecosystems, determines the likelihood of the contaminants leaching through the soil or being immobile. The soil sorption hence influences the elution of compounds into groundwater bodies as well as their availability for transformation by soil microbes, their volatilization from soil surfaces and their bioavailability for exposed organisms. 

Vinyl chloride fire emissions. Could occur in drinking water from atmospheric deposition, industrial contamination, leaching from protective coatings in storage tanks From chemical spills. Used in making PVC pipes. RW 24-170pgl 5 pgr 2 pgr GC-PID/ELCD, CG-MS... 

Modeling of contaminant leaching is a complex and diverse discipline. From simplified to more comphcated models there are several options available. The selection of the appropriate model is based on the needs and most importantly on the resources available such as data, sorbent and sorbate characteristics, and reaction constants, among others. The literature review presented in this chapter includes a wide range of applications for contaminant leaching from natural systems that have been contaminated to engineered systems where a byproduct needs to be evaluated for potential reuse as opposed to disposal. 

Modeling of Contaminant Leaching by Maria Diaz and Defhe Apul. Email defne.apul utoledo.edu... 

CHAPTER 3 Modeling of contaminant leaching (M. Diaz, D. Apul). 

This legislation began with a multimedia dimension to the extent that RCRA addresses solid waste and solid waste volumes that increased with growth and use of pollution control technologies for contaminants in air and water. On the other hand, solid wastes dispersed to landfills and other disposal sites can result in contaminants leaching into drinking water supplies. 

The influence of the ionic contamination leached from the plastic can be illustrated by 85°C/85% RH lifetest results for unpassivated transistors which were encapsulated in several types of moulding... 

The SCM approach was used to describe the siuface properties and prediction of heavy-metal adsorption on natural aquatic sediment [79]. All of the model parameters were determined from experimental data of potentiometric titration and metal Cu and Cd adsorption isotherm Results showed that all three typical versions (CCM, DLM and TLM) of SCMs can simulate the experimental data very well and provide an acceptable prediction for heavy-metal adsorption to natural sediments. The heavy-metal (Mo, Pb, Cu, Zn, Cd) contaminant leaching from weathered municipal solid waste was successfully modeled by DLM [80]. The leaching of Mo, Pb, and Cu from the weathered ash was well deseribed by surface complexation, whereas the precipitation of formed Zn-hydroxy species had to take into consideration to describe the leaehing data of Zn. 

A barrier layer, typically of silica, the purpose of which is to prevent contaminants leaching from the glass and changing the properties of either the alignment layer or the liquid crystal. 

Contaminant ingress within the cathode compartment of proton exchange membrane fuel cells fueled by hydrogen, the preferred system for automotive applications and the most technically challenging, represented the focus of this analysis. Therefore, proton exchange manhrane fuel cells based on other fuels, such as methanol and reformate, were excluded from the present analysis to focus the discussion. For these other fuels, additional contamination routes (contaminant leaching in the liquid methanol solution fuel followed by dissolution in the ionomer and transport to the cathode, etc.) and contaminants (CO, CO, CH, etc.) exist. 

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