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Table 5 1 Microcosm test series for each soil sample test solid liquid phase vapor phase notes and comments phase in water headspace 1 soil MTBE,TBA oxygen abiotic control test,no biological degradation sodium azide 2 sod MTBE TBA oxygen test of aerobic MTBE TBA degradation in native sods 3 sod MTBE TBA oxygen positive control test of aerobic MTBE and TBA degradation with MC-100 added culture MC-100 known to degrade these chemicals 4 soil MTBE TBA oxygen test of co-metabolism conditions ro ane 5 sod MTBE,TBA nitrogen test of anaerobic or low-oxygen conditions 6 soil MTBE TBA nitrogen anaerobic test with methanol added to deplete available electron Methanol acceptors The nominal setup for an individual macrocosm consisted of a 160mL glass vial with a septum-seal, 50g of soil and 75 mL of water The remaining vapor headspace was purged with either GC-grade oxygen or nitrogen (as applicable), respectively, for either 5 minutes or 30 minutes Each macrocosm in the set was then spiked with MTBE and TBA to bring the initial aqueous phase concentration to a level of approximately 10 mg/L For the abtotac control (Table 5 1, test 1), sodium azide was added to bring aqueous concentrations to a level of 2% For the positive control (Table 5 1, test 3), a bacterial culture known to degrade both TBA and MTBE was added at a level of approximately 400 ug-culture/g-soil The samples were incubated at room temperature (20-22°C) for the test duration In analysis, water samples were taken through the vial septa with a syringe and analyzed for MTBE, TBA, and methanol by purge and trap with GUMS The initial analysts schedule was planned for either a 70 day duration or when detection limits were reached for the aerobic tests, and up to 150 days for the anaerobic tests The implemented sampling schedule as included to the data tables of Appendix 2, along with measured test results over time Whale macrocosms were set up an duplicate, analysts was an most cases performed from one microcosm an each test series Duplicate analyses were performed to only selected sampling events At the test conclusion, the vapor headspace of selected macrocosms was sampled with a synnge and analyzed for oxygen and methane concentrations The liquid phase was analyzed for nitrate and sulfate 5.3. Data Analysis Data results from the microcosm tests are included in Appendix 2, including plots of concentration versus time In each case, both TBA and MTBE are monitored within the same macrocosm A summary table of results as also included an the appendix and identifies • whether the microcosm showed evidence of degradation for either MTBE or TBA (yes or no), • whether an intermediate increase in TBA concentration as noted over the test duration (yes), and 14