Soil contamination, extent

Definitions of the extent, type, and concentration of soil contamination are the primary factors that control the cost of soil remediation. The economic effectiveness of a remediation strategy depends on the following ... 

Exposure Levels in Humans. It has been speculated that the 1974 OSHA regulations have reduced workplace air levels of 3,3 -dichlorobenzidine (CPMA 1998). However, it would be important to conduct exposure studies to monitor air levels in the workplace to confirm this premise. The need for more information on the extent of air, water, and soil contamination by industrial plant emissions or waste sites eontaining 3,3 -dichlorobenzidine continues. There is httle information on exposure of children to 3,3 -diehlorobenzidine (or products derived from the compoimd). The compound has a very limited distribution and is not present in consumer goods (other than in insoluble pigmented forms). This information is necessary for assessing the need to conduct health studies on these populations. 

Such redistribution of contaminated soil has been tried in a variety of contexts reviewed later in this chapter, but it is helpful to illustrate two potential results, as noted in the work of Wang et al. (1990) and Park et al. (1990). In the former Case, extensive removal of PAHs from soil contaminated with a diesel fuel was observed in lysimeter test systems following fertilizer addition, liming and tilling. Even HMW PAHs were substantially removed by this process, making this study noteworthy because of the high extent of degradation. These results represent the... 

In a similar study, Grosser etal. (1991) were able to show that the reintroduction of pyrene-degrading bacterial cultures into soil contaminated with coal gasification processing wastes enhanced pyrene mineralization more than 50-fold. This enhancement also occurred in uncontaminated soils, but to a lesser extent. Interestingly, the inoculants used in this study appeared to also be a Mycobacterium species, but in contrast to the studies of Heitkamp Cerniglia (1989), it could grow on pyrene in the absence of supplemental carbon sources. 

Existing site information very likely comes from the initial site assessment or phase I Environmental Site Assessment (ESA) done for that site. A phase I ESA normally includes a site inspection, a review of the relevant data, interviews, and a written report. When a phase II ESA is performed, more existing site information is obtained. A phase II contains (limited) soil sampling, done to determine the soil contaminants, or to determine the soil quality on- and off-site. Phase II ESAs have written reports including recommendations and have the extent of contamination delineated. 

The model was used to study the advection and dispersion of a trace contaminant load into a low-permeability soil column. An anisotropic case was simulated. The model estimated and showed the spatial distribution of the contaminant plume and visually depicted the concentration values in grayscale. The three-dimensional visualization provided by the model was shown to be very useful for identifying the extent and severity of the soil contamination due to the trace compound load under three different types of input load distribution (point source, line source, and two-point... 

The applications of separation science to environmental restoration are centered on the cleanup of contaminated groundwaters and soils. The extent and complexity of the groundwater contamination problem continues to present formidable technological obstacles to cleanup. The most important factors that contribute to this complexity are the large number of contaminated sites, the wide diversity of the contaminants present in those sites, the Inherent complexity of the subsurface chemistry of the contaminants, and the difficulty in interpreting existing regulations to establish compliance and properly prioritize site remediation efforts. 

Extent of Soil Contamination with Energetic Materials at... 

Terrestrial wildlife movements are such that site-specific tools are more efficiently used to refine exposure estimate. In this case, site-specific exposure estimates are used and compared with safe thresholds for toxicity, termed toxicity reference values (TRVs). Toxicity reference values for wildlife have been developed for energetic compounds. This chapter presents a brief overview of the processes used to establish these tools for ERA for explosives and related soil contaminants that are frequently of potential ecological concern at the affected military sites. This chapter also provides recommendations for use of these values in the ERA process. Investigations addressing the importance and extent of habitat disturbance as a component of the ERA process on explosives-contaminated ranges are reviewed in Chapter 11. General bioaccumulation principles and applications of the bioaccumulation factor and bioconcentration factor (BAF and BCF, respectively) concepts that are often employed in the ERA process to determine bioaccumulation potential of MC for terrestrial receptors are reviewed in Chapter 10. 

Soil contamination also can be very difficult to detect. New analytical methods have made it possible to detect and analyze dioxins, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). Analytical techniques have made it possible to detect the presence of these substances, determine whether remediation is needed, and evaluate the extent to which it has been carried out. Chemistry has provided or contributed to the remediation technologies that have been developed,... 

The study area is situated near Rouyn-Noranda, about 600 km to the north-west of Montreal, Canada (48°14 N, 79°01 W). Three sites were sampled at a downwind distance of 0.5, 2 and 8 km from the Horne copper smelter. At each site, soil samples were collected under three trembling aspen Populus tremuloides Michx) of similar age (< 30 years old). The soils developed in postglacial lake sediments of silt texture to form Luvisols, according to the Canadian System of Soil Classification (Soil Classification Working Group, 1998). The extent of soil contamination received through the atmospheric deposition of metals represents the main difference between the three sites as other characteristics were kept constant (e.g. climate, parent material, slope, aspect, etc.). For a more detailed description of the sites, see Seguin et al. (2004). 

The extent of arsenic sorption in natural waters will be influenced by many factors, relating to both the sorbent and the water composition. As(V) and As(III) have different affinities for various sorbent phases that may be present in sediment, soils, and aquifers. Thus the redox speciation of arsenic and the characteristics of available sorbents will strongly affect the extent of arsenic sorption as will the pH and concenPations of co-occurring inorganic and organic solutes in the aqueous phase. Since sorption is a surface phenomenon and is limited by the availability of surface sites on the sorbing phase(s), the extent of competition between arsenic and other sorbates will depend not only on the affinity of each sorbate for the surface but also on their concentrations relative to each other and to the surface site concentration. Elevated concenPations of phosphate have been used to desorb arsenic from clays (51) and from soils contaminated with arsenical pesticides (113). 

Most of the unplanned release locations throughout the 100-N Area have not been sampled to determine the extent of contamination. Although screening sampling or radiation surveys were usually performed and exposed surface contamination was excavated, quantitative radionuclide- and chemical-specific analyses were not performed. Based on the areas of known releases (e.g., 116-N-3 crib and trench) and areas of inferred releases, inferred areas of soil contamination have been identified. These areas are shown in Figure 5-25 and the sources are listed in Table 5-1. 

Other elements, such as boron, cadmium, nickel and zinc are readily taken up by plants and we would therefore expect that they would be involved in most of the short-term problems which result from soil contamination. There are, therefore, two categories of trace-element pollution that involving elements such as copper, lead and mercury, which presents what is principally a longterm environmental problem, and that involving elements like boron, cadmium, nickel and zinc which presents more immediate problems. To some extent, these categories may be considered separately. 

The process of direct anaerobic-aerobic treatment resulting in humification of TNT and its congeners offers a convincing and simple concept (Fig. 18 process II) for the remediation of soil contaminated with TNT and congeneric compounds. This is evident by comparison with the alternative process I (Fig. 18), which requires the desorption of the contaminants by innocuous solvents such as methanol or ethanol. Desorption plus the separation of particles must precede the actual anaerobic process of polynitrotoluene reduction. Furthermore, the anaerobic stage requires a microbial system which degrades TAT and diaminotoluenes productively or at least to such an extent that subsequent aerobic treatment results in complete mineralization. 

Phytoremediation is a viable choice for hydrocarbons remediation if sufficient time is allowed for plant establishment and contaminant degradation. In the process, plants could be used to extract, detoxify, and/or sequester toxic pollutants from soil (Xu et al., 2005). Initial HM for C. ligularis was 1 000 mg kg perlite. PAH and aliphatics were completely removed for inoculated and non-inoculated plants during first 60 days of culture (results not shown). This pattern probably can be due to low hydrocarbon concentrations resulting in a high hydrocarbon rate (4.75 mg HM kg perlite d ) and extent (100%). Similar results were obtained by Alvarez-Bemal et al. (2007) using Mimosa monancistra to remove PAH in soil contaminated with 200 mg phenanthrene kg soil, 100 mg anthracene kg soil, and 50 mg benzo(a)pyrene kg soil. Concentration of PHE dropped sharply in the first 14 days, after 56... 

Nonaqueous phase Hquids (NAPLs) present special problems for soil and ground water cleanup. Contaminant transport through ground water depends in part on the water solubiHty of the compound. Because NAPLs cling to subsurface particles and are slow to dissolve in ground water, they hinder cleanups and prolong cleanup times. Dense nonaqueous phase Hquids (DNAPLs) migrate downward in the aquifer and can coUect in pools or pockets of the substmcture. Examples of DNAPLs are the common solvents tetrachloroethylene (PCE) and trichloroethylene (TCE) which were used extensively at many faciHties before the extent of subsurface contamination problems was realized. 

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