Effect of soil composition and contamination on naphthalene mineralization

The extent of biodegradation in soil may be determined by factors such as sorption of the compound to soil and different soil fractions. It is anticipated that knowledge gained in laboratory studies can eventually be applied to field conditions (i.e. bioremediation).

In this study, naphthalene (a nonpolar hydrocarbon) biodegradation was examined in batch cultures under aqueous conditions and in soil slurries. Four soils with different characteristics (varying amounts of organic matter, clay, silt, and sand) were used to make the soil slurries. Biodegradation assays were performed with and without Strain 5R, a known naphthalene degrader. The soils used to make the soil slurries were contaminated with naphthalene using either a dry or wet contamination procedure.

This study resulted in a number of findings: 1) Colony hybridizations determined that the frequency of the NahA (a naphthalene degrading) genotype increased with exposure to naphthalene. 2) Changes in the soil pH can affect the total amount of mineralization. 3) The method of contamination (wet or dry) may have an effect on the amount of mineralization. 4) Dry contaminated soil slurries with Strain 5R had faster mineralization rates than Strain 5R by itself in water. 5) Mercuric chloride is not the best method to sterilize soil.