Table 1. Mercury concentrations of soil samples from the two power plants.
| Sampling site | Average mercury level* (μg/kg) | Maximum Mercury level (μg/kg) | Years of operation | Reference |
|---|---|---|---|---|
| Power Plant A, this study | 305 ± 47.97 | 362 | 4 | |
| Power Plant B, this study | 383 ± 32.59 | 407 | 3 | |
| Power Plant BaoJi, China | 606 | 2,105 | 16 | 33 |
| Power Plant “A Horizon”, US | 19,900 | — | 30 | 34 |
| Power Plant ChengDu, China | 24,546 | 40,032 | >30 | 35 |
Dashed line: background soil mercury concentration in China (37 μg/kg)32. Sampling sites are marked in Fig. 1. Uncontaminated soil samples were collected from a farmland site > 55 km away from any power plants. A1, A2, B1, B2, B3 and B4 are locations where biological samples were collected. The level of significance was defined at P < 0.05 using T-test.