Assessing the aerobic biodegradability of 14 hydrocarbons in two soils using a simple microcosm/respiration method

The aerobic biodegradability of 14 hydrocarbons in two soils was determined using a simple microcosm/respirometric method based on oxygen consumption. Biodegradability was assessed indirectly by measuring the depletion of oxy gen over time in the headspace of microcosms containing soil and test chemi cals. The microcosms consisted of small glass vials fitted with valves that allowed headspace gas samples to be collected, essentially resulting in a sealed system. Respiration data from control microcosms were obtained from identically treated microcosms with no test chemical. Control data were nec essarily included in all calculations of percent of theoretical oxygen dema nd (%ThOD) for any given test chemical. Two experiments were performed to v erify this simple biodegradation test method. First, an experiment was perf ormed in which disappearance of n-tetradecane from the microcosms was measu red directly by standard soil extraction and analytical techniques while si multaneously performing this simple respirometric method based on %ThOD wit h the same test chemical. Second, the method was compared to a well-establi shed radiochemical technique using C-14-phenanthrene. Results of both compa risons showed that the method is both accurate and reliable. The consistent manner with which the data were produced in two different soils show that the method is also very reproducible. The method described here provides a simple and inexpensive method for determining the aerobic biodegradability of organic compounds in soils. (C) 2001 Elsevier Science Ltd. All rights re served.