| Period | Year 2013 | Year 2016 | ||
| Minimum | Maximum | Minimum | Maximum | |
| Cold season | 4.03 µg/l | 16.24 µg/l | 13.03 µg/l | 17.05 µg/l |
| Summer season | 12.10 µg/l | 19.73 µg/l | 13.20 µg/l | 19.81 µg/l |
| Rainy season | 7.008 µg/l | 18.02 µg/l | 13.05 µg/l | 17.63 µg/l |