TABLE 2.
Comparison of MTBE carbon and hydrogen isotopic enrichment factors with 95% confidence intervals and 2D-CSIA slopes caused by abiotic processes and aerobic biodegradation by pure and mixed culturesc
| Process or culture | Carbon |
Hydrogen |
Λ ± 95% CI | Reference(s) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ɛC (‰) | ±95% CI (‰) | R2 | R (%) | No. of data points | ɛH (‰) | ±95% CI (‰) | R2 | R (%) | No. of data points | |||
| Abiotic processes | ||||||||||||
| Oxidation by permanganate | NA | −109 | 9 | 0.98 | 90 | 16 | NA | 10 | ||||
| Acidic hydrolysis (SN1) | −4.9 | 0.6 | 0.995 | 88 | 6 | −55 | 7 | 0.99 | 88 | 6 | 11 ± 1 | 10 |
| Volatilization | ||||||||||||
| Headspace equilibrium (aqueous, close) | +0.2 | 0.2 | NA | NA | 19 | |||||||
| Diffusive (sand/aqueous) | −1.0 | 0.1 | 0.8 to 0.9 | −5 | 1 | ∼5 | 25 | |||||
| Advective/air sparging (sand/aqueous) | ∼0 | 0.1 | 0.8 to 0.9 | −4 to −12 | NA | 0.88 to 0.99 | NA | 25 | ||||
| Bubbling (aqueous, open, n = 2) | +0.11 | 0.03 | 0.82 | 99.99 | 26 | −5 | 1 | 0.93 | 99.997 | 26 | −27 ± 4 | This study |
| Pure cultures | ||||||||||||
| M. petroleiphilum PM1a | −2.0 to −2.4 | 0.1 to 0.3 | 0.88 to 0.98 | 93 | 39 | −33 to −37 | 4 to 5 | 0.90 to 0.99 | 80 to 90 | 26 | 18 ± 3 | 11, 14 |
| Methylibium sp. strain R8 | −2.3 | 0.1 | 0.98 | 98 | 40 | −40 | 4 | 0.95 | 91 | 36 | 17 ± 1 | 3, 41 |
| A. tertiaricarbonis L108 | −0.48 | 0.05 | 0.94 | 96 | 34 | NS (−0.2) | 8 | 0.00 | 82 | 29 | NA | 41 |
| R. ruber IFP 2001 | −0.28 | 0.06 | 0.81 | 97 | 27 | NS (+5) | 20 | 0.14 | 88 | 24 | NA | 41 |
| P. tetrahydrofuranoxydans K1 | −2.3 | 0.2 | 0.99 | 12 | −100 | 10 | 0.99 | 11 | 48 ± 5 | 33 | ||
| Mixed cultures | ||||||||||||
| Borden enrichment culture | −1.52 to −1.97 | 0.06 | 0.99 | 95 to 97 | 38 | NA | NA | 19 | ||||
| VAFB mixed consortiuma | −1.5 to −1.8 | 0.1 | 0.95 to 0.99 | 99.7 | 55 | −29 to −66 | 3 to 4 | 0.91 to 0.99 | 80 to 90 | 24 | 12 ± 2 to 45 ± 2 | 14, 33 |
| Port Hueneme microcosm | −1.4 | NA | NA | 27 | ||||||||
| Artificial mixture (L108-PM1) | −0.2 to −1.0 | 0.1 to 0.2 | 0.96 to 0.995 | 98.5 | 36 | NS (−4 to +2) | 13 to 15 | 0.04 to 0.09 | 83 | 18 | NA | 42 |
| Biofilms on geotextiles from Leuna, Germanyb | ||||||||||||
| Replicate CO1 | −0.4 | 0.2 | 0.98 | 87 | 7 | NS (−4) | 9 | 0.36 | 87 | 4 | NA | This study |
| Replicate CO2 | −0.4 | 0.4 | 0.94 | 76 | 6 | NS (−9) | 11 | 0.59 | 76 | 5 | NA | This study |
| CO total | −0.4 | 0.1 | 0.97 | 87 | 13 | NS (−5) | 4 | 0.37 | 87 | 9 | NA | This study |
| Replicate PO1 | −0.37 | 0.09 | 0.96 | 94 | 10 | NS (−7) | 18 | 0.81 | 86 | 4 | NA | This study |
| Replicate PO2 | −0.4 | 0.1 | 0.91 | 80 | 9 | NS (−7) | 17 | 0.89 | 80 | 4 | NA | This study |
| PO total | −0.36 | 0.06 | 0.94 | 94 | 19 | NS (−7) | 7 | 0.85 | 86 | 8 | NA | This study |
a
Original data reevaluated by Elsner et al. (11).
b
Each replicate bottle reported individually but also as a total.
c
NA, not analyzed or not applicable; NS, not significant; CI, confidence interval; R%, maximum percentage of MTBE removal analyzed. Abiotic processes include oxidation, acidic hydrolysis, and different types of volatilization.