Active composting of soil is the term used to describe processes whereby soil is mixed with large amounts of biodegradable organic material resulting in greatly increased microbial activity due to degradation of the organic matter. Active compositing of contaminated soil has proven to be an effective means of bioremediation for a wide range of contaminants [1-3] and is especially effective when dealing with weathered hydrocarbon-contaminated soils [4]. Polycyclic aromatic hydrocarbons (PAHs) containing four or more condensed rings are usually relatively recalcitrant [5]. Composting has been specifically suggested for treatment of such PAHs in contaminated soil since they may be cometabolized in the presence of more easily degraded compounds [6]. However, little is known about the fate of PAHs during composting. Although chemical analysis frequently shows their disappearance, they may become unextractable, converted to other chemical forms or be mineralized. If mineralization does occur, rates must be determined so that the process can be better compared to others. In addition, mineralization rates can be used in mathematical modeling of the process in order to better explain the mechanisms governing it. Significant mineralization rates have been reported for PAHs having more than 4 fused rings during composting of municipal waste [7]. The addition of mature compost to soil spiked with an anthracene (3-rings) and hexadecane-contaminated soil has resulted in the mineralization of these contaminants [8]. However, no data are available for mineralization rates during active composting of soil.
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