Organic contaminants, in soil

Organic contaminants are compounds with a carbon skeleton, usually associated with atoms of hydrogen, oxygen, nitrogen, phosphorus and sulphur (see Section 

Radon gas is invisible, odourless and tasteless. It is therefore difficult to detect and 

Once in the soil environment organic contaminants may move in, or interact with, the soil atmosphere, soil water, mineral fractions and organic matter. Ultimately, however, the organic contaminants will either dissipate or persist (Fig. 4.27). Compounds persist if they are of low volatility, low solubility (Box 4.14) or have a molecular structure that resists degradation. Conversely, if compounds are highly volatile, highly soluble or are easily degraded, they will be 

14 Physical and chemical properties that dictate the fate of organic contaminants 

The solubility of a compound depends on its polarity. If water is the solvent, the compound will need to be of similar polarity to be dissolved in it, for example ethanol (CH3CH2OH). In ethanol the OH-group is polar and therefore the molecule has polar character (Fig. 1b). If the compound is nonpolar, for example ethane, it will not dissolve in polar water (Fig. 1c) because opposites do not mix. Ethanol will, however, dissolve in a non-polar solvent, for example hexane. Thus, the term solubility should always be used with clarification of the solvent, for example aqueous solubility. Solubility is expressed as the mass of a substance that will dissolve in a given volume of solvent, for example mg I-1. 

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Introduction to Organic Contaminants in Soil Concepts and Risks... 

Soil slurry-sequencing batch reactor (SS-SBR) is a technology for the biological treatment of organic contaminants in soil. The technology has been evaluated in full-scale field tests but is not commercially available. The SS-SBR system consists of a set of tanks operated on a fill-and-draw basis. Each tank is filled during a discrete period of time and operated as a batch reactor. According to the vendor, reaction times are on the order of days. 

CF Systems extraction process removes a broad range of contaminants and typically extracts more than 99% of the organic contaminants from the waste feed. However, the CF Systems process cannot remove heavy metals or other inorganics. Also, the CF Systems process does not destroy the organic contaminants in soil or waste but rather extracts them from the medium in which they are contained. 

Microbial cleaners (MCs) are a mixture of specially selected microorganisms and biocatalysts designed for the bioremediation of organic contaminants in soil or water. According to the vendor, MCs have been used in multiple full-scale applications and are commercially available from EnviroLogic Engineering. 

The MelDAS technology is a modified incineration process in which high temperatures destroy organic contaminants in soil and concentrate metals into fly ash. Details of the metals immobilization process can vary based on the specific application, but the essential steps are to combine the toxic-metal containing material with the appropriate amount of sorbent, to form this mixture into pellets or briquets placing the metal compounds into intimate contact with the sorbent, and to heat treat the pellets causing a reaction to form nonleachable metal compounds. The MelDAS process requires a sorbent. 

X-ray treatment is being investigated for the decontamination of organic contaminants in soils or aqueous solutions. Bench-scale ex situ experiments have been conducted, and in situ treatment has been suggested as possible. The technology is not currently commercially available. 

Berg, J. D. Eggen, T. (1991)- Enhanced composting for cold-climate biodegradation of organic contamination in soil. In Proceedings, Third EPA Forum on Innovative Hazardous Waste Technologies, Dallas, Texas, June 11-13, pp- 17-36. 

Boyd, S. A. Sun, S. (1990). Residual petroleum and polychlorinated oils as sorptive phases for organic contaminants in soils. Environmental Science Technology, 24, 142-4. 

A Standard Reference Material is certified to contain 94.6 ppm of an organic contaminant in soil. Your analysis gives values of 98.6, 98.4, 97.2, 94.6, and 96.2 ppm. Do your results differ from the expected result at the 95% confidence level If you made one more measurement and found 94.5, would your conclusion change ... 

Khandelwal, A., Rabideau, A. J., and Shen, P. (1998). Analysis of diffusion and sorption of volatile organic contaminants in soil/bentonite barrier materials, Environmental Science Technology, 32(9), 1333-1339. 

PAHs in soil may partition into soil organic matter (SOM) or adsorb on soil minerals. The sorptive properties of SOM fractions for organic contaminants in soil play an important role on the transportation of PAHs in soil. Xiao et al. (2004) has reported that soil/sediment organic matter can be fractionated into four fractions with a combined wet chemical procedure and that kerogen and black carbon (BC) are major SOM components in soil/sediment samples collected from the industrialized suburban areas of Guangzhou, China. Phenanthrene and naphthalene were used as the sorbates to study PAH s sorption isotherms on four original and four Soxhlet-extracted soil/sediment samples, 15 isolated SOM fractions, and a char as the sorbents. The sorption isotherms of phenanthrene and naphthalene on all the sorbents were variously nonlinear. The particulate kerogen and black carbon (KB) fractions... 

ISO/DIS 11464 Soil Quality - Pretreatment of Samples for Physico-Chemical Analyses, 1995 ISO/DIS 14507 Soil Quality - Sample Pretreatment for Determination of Organic Contaminants in Soil, 1995... 

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