| Date | Value |
|---|---|
| Jun 30, 2013 12:01 | 0.32 ppm |
| Jun 23, 2013 11:41 | 0.26 ppm |
| Jun 14, 2013 16:24 | 0.36 ppm |
| Jun 7, 2013 12:39 | 0.16 ppm |
| May 21, 2013 16:54 | 0.36 ppm |
| May 14, 2013 18:43 | 0.32 ppm |
| May 12, 2013 16:22 | 0.32 ppm |
| May 9, 2013 17:31 | 0.34 ppm |
| May 8, 2013 21:16 | 0.64 ppm |
| May 6, 2013 16:19 | 0.64 ppm |