Abstract

Different moisture management methods were compared for biodegradation efficiency in sandy and organic soils. The conventional method consisted in maintaining the soil moisture at approximately 50 to 75% field capacity accompanied by daily aeration and mixing. In the test method, the soil was allowed to dry out completely for three to four days after which the soil was moistened to 50 to 75% of field capacity and mixed daily for five days. In the test method the drying and moisturizing cycles were maintained throughout the experiment. There was no difference in treatments in the sandy soil, both treatments resulting in the detoxification to background levels within five weeks. During the processing of the organic soil, an increase in toxicity was observed, apparently due to increased availability of hydrocarbons, and possibly due to the production of toxic intermediates of biodegradation. The transformation rate in the test method was 22% less than in the conventional method, although this transformation started at least four weeks earlier than in the conventional method. Based on these observations, a combination of drying (to increase bioavailability) and conventional moisture management (to stimulate hydrocarbon degrading microorganisms) is recommended.

Key words:  Remediation, toxicity, petroleum.

Abbreviation

Abbreviations:TPH, Total petroleum hydrocarbon; CEC, cation exchange capacity; ESP, exchangeable sodium percentage.