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V,, (L-water) water volume within the microcosm <br /> Va (L-air) air volume within the microcosm <br /> H, (L-water/L-air) chemical-specific Henry's law coefficient <br /> ms (kg) total mass of soil in the microcosm <br /> fo,(g-oc/g-soil)organic carbon fraction of the soil <br /> K,,,, (L-water/kg-oc) chemical-specific organic carbon to water partition coefficient <br /> Calculated values for the zero-order rate estimate and first-order rate estimate are taken <br /> as averages over the applicable time increments in a given test The results are tabulated <br /> in Appendix 2 for each test <br /> Half-life is also included in the tables of Appendix 2, and is defined as <br /> t112 = ln(2)/kw r-observed <br /> A concise summary of test results is included in Table 5 2 <br /> Table 5 2 Sum ary of microcosm test results <br /> MTBE TBA <br /> maximum degrad Intests with degradation Identdled degrad- In tests wtrh degradation identified <br /> test anon ation <br /> duration in <br /> range of mass lag time half life range indicated range of mass lag time half life range <br /> Microcosm Test/Sire Locavon da s no tests change ran a da hours no tests chane ran a da hours <br /> Aerobic native soil <br /> 30011 Crown Valley Parkway 56 3 of 3 100% 0 to 14 95 to 157 3 of3 -100% 7 to 28 82 to 357 <br /> 16969 Brookhurst 56 5 of 5 100% 0 to 49 174 to 1263 5 of 5 -100°k 0 to 14 15 to 184 <br /> 27101 Arte a Ht wa 154 3 of 3 -39%to-1001A 7 to 140 684 to 2965 3 of 3 -100% 14 to 35 169 to 840 <br /> Anaerobic transformation <br /> 30011 Gown Valley Parkway 196 3 of 3 -29%to 100% 21 to 145 167 to 3976 2 of 3 -100% 0 to 14 345 to 1129 <br /> 16969 Brookhurst 161 3 of 3 100% 7 to 70 116 to 1362 3 of 3 -50%to 79% 21 to 145 239 to 2689 <br /> 27101 Orte a HI hwa 154 1 of 3 100% 14 to 56 657 2 of 3 -100% 14 to 70 1227 to 1974 <br /> naerobic with methanol <br /> 30011 Crown Valley Parkway 196 3 of 3 99%to 100% 56 to 145 87 to 777Fla <br /> oT 3 211% 142 3720 - <br /> 16969 Brookhurst 161 3 of 3 100% 21 to 111 90 to 264 oT 3 -- >161 — <br /> 27101 Ortega Hiqhway 154 2 of 3 100% 56 to 114 179 to 448 0 of 3 >154 — <br /> o-metabolism propane <br /> 30011 Crown Valley Parkway 196 1 of 3 100% 125 to 145 160 0 of 3 — >196 — <br /> 16969 Brookhurst 161 3 c 3 -100% 14 to 70 127 to 281 1 of 3 27% 70 to 91 4556 <br /> 27101 Or[e a w hwa 154 1 o 56 to 70 2414 1 of 3 -84% 0 to 7 113 <br /> Control Tests for all tests far all tests <br /> All control <br /> 30011 Crown Valley Parkway 196 0 of 3 8%to 15% (negative contrcl) 0 Of 3 -8%to 16% (negative control) <br /> 16969 Brookhurst 161 0 of 5 9%to 1014 0 Of 5 5%to 10% <br /> 27101 Ortega Highway 154 0 of 3 0% 0 of 3 11%to 0 <br /> erobic soil with MC 100 <br /> 30011 Gown Valley Parkway 28 3 of 3 -100% (Positive control) 3 of 3 -100% (positive control) <br /> 16969 Brookhurst 14 5 of 5 -100% 5 of 5 -100% <br /> 27101 Orte a Ht hwa 7 3o(3 3 -100% 3 of 3 -100% <br /> 5.4. Discussion of Microcosm Data Results <br /> 5 4 1 Aerobic microcosms <br /> Both MTBE and TBA showed significant degradation in all aerobic soil microcosms, at <br /> all three investigated sites For MTBE in 8 of 11 microcosms, with all three sites <br /> represented, the observed acclimation time was lel days or Iess For TBA, all samples <br /> showed acclimation times less than 35 days, but with an observed trend of increased <br /> acclimation time, respectively, for 16969 Brookhurst, 30011 Crown Valley Parkway, and <br /> 27101 Ortega Highway Calculated degradation rates for TBA and MTBE were in similar <br /> 16 <br />