Table 2. Summary Statistics of Emission Rates (g D–1) of Light Hydrocarbons and VOCs from Abandoned Wells in Western Pennsylvaniaa.
| compound | frequency of left-censored data | minimum | maximum | KM mean | KM standard deviation | median |
|---|---|---|---|---|---|---|
| Natural Gas Constituents as Measured using ASTM-D-1945 (g d–1) | ||||||
| methane | 15/48 | <1.8 × 10+0 | 8.3 × 10+4 | 2.2 × 10+3 | 1.2 × 10+4 | 6.9 × 10+1 |
| ethane | 15/48 | <4.2 × 10–3 | 3.8 × 10+2 | 1.8 × 10+1 | 5.7 × 10+1 | 1.5 × 10+0 |
| propane | 18/48 | <5.3 × 10–3 | 6.8 × 10+1 | 3.9 × 10+0 | 1.3 × 10+1 | 4.2 × 10–1 |
| isobutane | 18/48 | <1.8 × 10–3 | 1.3 × 10+1 | 7.5 × 10–1 | 2.4 × 10+1 | 1.1 × 10–1 |
| butane | 18/48 | <8.5 × 10–4 | 2.3 × 10+1 | 1.2 × 10+0 | 3.9 × 10+1 | 1.5 × 10–1 |
| neopentane | 24/38 | <3.5 × 10–4 | 7.3 × 10–1 | 3.0 × 10–2 | 1.1 × 10–1 | <5.4 × 10–3 |
| isopentane | 18/48 | <8.5 × 10–4 | 8.8 × 10+0 | 5.0 × 10–1 | 1.5 × 10+1 | 7.2 × 10–2 |
| pentane | 26/48 | <7.3 × 10–4 | 7.1 × 10+0 | 3.5 × 10–1 | 1.2 × 10+1 | 5.7 × 10–2 |
| VOCs as Measured using EPA Method TO-15 (g d–1) | ||||||
| hexane | 17/48 | <5.7 × 10–6 | 1.4 × 10+1 | 7.2 × 10–1 | 2.3 × 10+1 | 1.1 × 10–1 |
| cyclohexane | 17/48 | <1.2 × 10–5 | 3.0 × 10+0 | 1.6 × 10–1 | 4.9 × 10–1 | 2.7 × 10–2 |
| heptane | 21/48 | <5.9 × 10–6 | 5.7 × 10+0 | 3.8 × 10–1 | 1.1 × 10+1 | 5.2 × 10–2 |
| benzene | 24/48 | <3.0 × 10–6 | 7.4 × 10–1 | 2.2 × 10–2 | 1.1 × 10–1 | 2.2 × 10–3 |
| toluene | 35/48 | <3.5 × 10–6 | 8.7 × 10–1 | 2.7 × 10–2 | 1.3 × 10–1 | <1.0 × 10–3 |
| ethylbenzene | 43/48 | <4.0 × 10–6 | 4.4 × 10–2 | 1.8 × 10–3 | 8.1 × 10–3 | <7.2 × 10–4 |
| m,p-xylene | 31/48 | <4.0 × 10–6 | 4.3 × 10–1 | 2.1 × 10–2 | 8.3 × 10–2 | <1.9 × 10–3 |
| o-xylene | 40/48 | <4.0 × 10–6 | 8.4 × 10–2 | 3.9 × 10–3 | 1.6 × 10–2 | <9.9 × 10–4 |
| 1,3,5-trimethylbenzene | 40/48 | <4.6 × 10–6 | 4.4 × 10–2 | 1.6 × 10–3 | 6.5 × 10–3 | <1.1 × 10–3 |
| 1,2,4-trimethylbenzene | 41/48 | <4.6 × 10–6 | 5.8 × 10–2 | 1.7 × 10–3 | 8.4 × 10–3 | <1.0 × 10–3 |
| 4-ethyltoluene | 41/48 | <4.6 × 10–6 | 4.2 × 10–2 | 1.4 × 10–3 | 6.3 × 10–3 | <1.0 × 10–3 |
| propylbenzene | 46/48 | <4.6 × 10–6 | 8.1 × 10–3 | <7.7 × 10–4 | ||
| cumene | 45/48 | <4.6 × 10–6 | 6.2 × 10–3 | 1.7 × 10–4 | 9.4 × 10–4 | <7.7 × 10–4 |
a
The product of the lower limits of flow detection and reporting limits was used for the calculation of minimum emission rates. Midpoints of adjusted light hydrocarbon and VOC concentration data were used for all calculations. KM mean and standard deviations were not calculated for data sets having less than three reportable values. All data and calculations are reported in two significant figures.