Transport of Organic Compounds Dissolved in Ground Water

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  • JNJoan M. Newsom
    Joan M. Newsom
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Abstract
Organic compounds, such as trichlomethylene (TCE) and chlorobenzene, that have been found in drinking water supplies are of public concern because they are possibly carcinogenic. These substances can now be routinely detected in trace amounts with gas chromatograph mass spectrometers. There are some polar organic compounds, which are not detectable individually by common methods and therefore little is known about them. The transport of organic compounds is more difficult to predict than the flow of ground water because: Trace amounts of pollutants are difficult to measure Transport is complicated if the compound is partitioned into several phases The concentration of organics in ground water may vary due to aquifer heterogeneity and other hydrologic factors Reactions with other organic compounds and reactions with the aquifer material (such as adsorption) may affect the mobility of the organics Biodegradation may also affect net transport. Adsorption is a factor in the attenuation of non‐polar organics in aquifers with significant organic content (>0.1 percent organic carbon). The organic material adsorbs the non‐polar organic chemicals. The mobility of a pollutant in such an aquifer depends on at least two parameters: the levels of dissolved organic matter and the content of organic carbon in the aquifer material. The partition coefficient of the chemical pollutant between the aquifer and water is commonly calculated as a function of the organic content of the aquifer and the partition coefficient between octanol and water. Field and laboratory results reported in the literature indicate that the following organic compounds may be biodegradable under aerobic conditions: alkyl benzenes and chlorobenzenes. Under anaerobic conditions halogenated aliphatics, alkyl benzenes, several pesticides and phenolic compounds may be biodegradable. Halogenated aliphatics appear not to degrade under aerobic conditions and non‐chlorinated aro‐matics and chlorobenzenes appear not to degrade under anaerobic conditions. Alkyl benzenes biode‐grade more rapidly than their halogenated counterparts.
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