A research note on the assessment of optimum conditions for preparing soils for bioremediation feasibility testing

Abstract In this applied study, the effects of short‐term storage at 22°C, 6°C, and −25°C on the numbers of microorganisms enumerated were examined with soils collected from a petrochemical contaminated soil containing multiple contaminants including phenol, polycyclic aromatic hydrocarbons, and petroleum hydrocarbons. Short term storage of soils at refrigerator temperature did not significantly change the number of microorganisms compared to those in the fresh soil (0 days of storage); however, at −25°C there was a slight decrease in the phenol utilizers and total viable count (TVC). Long‐term storage caused a significant decrease in the number of phenol utilizers in the petrochemical‐contaminated soil samples. Chemical dispersing agents were used in an attempt to increase the extraction of microorganisms from naphthalene contaminated soil which were predominantly clay soils. These did not significantly change the enumeration of naphthalene utilizers or TVC. While these results are not unexpected from current research and knowledge of microbial community succession in laboratory environments, the results from the applied nature of this study confirm that it is best practice to keep soil samples designated for bacterial enumeration for the shortest possible time, and not longer than 1–2 weeks, and at refrigerated temperature (6°C) in preference to room (22°C) or deep freezer (−18°C) temperatures.