Table 4.
The effect of additive concentrations on ambient VOC levels. The degrees of freedom (df) and H statistics of three-way Kruskal-Wallis tests of the effects of H2O2 (doses of 0.5, 1, 2 and 5 M), Fe(III)sulfate (0, 0.6, 2 and 20 mM) and citrate (0 and 50 mM) on general VOC levels at different time points as measured with PID (*P < 0.05, **P < 0.01, ***P < 0.001)
| Time (min) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 15 | 30 | 45 | 60 | 90 | 120 | 180 | 1–3 d | ||
| Treatment | df | H | H | H | H | H | H | H | H | H |
| H2O2 | 4 | 5.4 | 3.4 | 2.9 | 1.7 | 1.7 | 9.2 | 24.2*** | 43.6*** | 59.7*** |
| Fe(III) | 4 | 9.3 | 46.7*** | 48.6*** | 41.3*** | 45.7*** | 53.2*** | 43.7*** | 41.1*** | 34.5*** |
| Citrate | 1 | 4.8* | 12.3*** | 17.3*** | 19.7*** | 16.2*** | 14.9*** | 7.6** | 5.9* | 0.1 |
| H2O2 × Fe(III) | 12 | 20.8 | 9.8 | 7.2 | 9.2 | 11.1 | 7.0 | 6.9 | 6.6 | 7.3 |
| H2O2 × citrate | 3 | 0.8 | 5.9 | 3.6 | 4.0 | 7.2 | 7.1 | 4.6 | 6.0 | 1.0 |
| Fe(III) × citrate | 4 | 14.2** | 2.7 | 3.6 | 5.8 | 5.9 | 3.0 | 6.2 | 3.3 | 4.1 |
| H2O2 × Fe(III) × citrate | 12 | 22.6* | 13.4 | 9.7 | 14.3 | 12.2 | 7.9 | 7.3 | 4.3 | 2.5 |