TABLE 1.
Mean values of soil chemical, physical and biological properties (± SE) for the three Hg contamination levels low, moderate, and high Hg (n = 4) (compare also with Frossard et al., 2018).
| Low Hg | Moderate Hg | High Hg | P + | |
| Soil chemical properties: | ||||
| Hgtot (μg kg–1 soil) | 251 (± 46.3) | 3,019 (± 945) | 36,097 (± 2,398) | < 0.001 |
| Hgwater extractable (μg kg–1 soil) | 1.54 (± 0.35) | 4.95 (± 1.61) | 67.7 (± 17.5) | 0.002 |
| Corg (%) | 1.63 (± 0.24) | 2.76 (± 0.52) | 2.18 (± 0.38) | 0.19 |
| Ctot (%) | 2.71 (± 0.16) | 3.78 (± 0.43) | 3.88 (± 0.47) | 0.10 |
| Ntot (%) | 0.17 (± 0.02) | 0.29 (± 0.04) | 0.31 (± 0.04) | 0.041 |
| C:N ratio | 16.5 (± 1.16) | 13.1 (± 0.33) | 12.7 (± 0.57) | 0.013 |
| pH (H2O) | 8.30 (± 0.10) | 8.13 (± 0.11) | 7.98 (± 0.04) | 0.08 |
| Soil physical properties: | ||||
| Sand (%) | 44.4 (± 6.22) | 22.8 (± 1.29) | 29.4 (± 1.60) | 0.008 |
| Silt (%) | 48.7 (± 6.03) | 66.4 (± 2.16) | 61.2 (± 1.00) | 0.023 |
| Clay (%) | 7.0 (± 0.58) | 10.8 (± 1.01) | 9.5 (± 0.73) | 0.023 |
| Soil biological properties: | ||||
| Microbial biomass (μg DNA g–1 soil) | 19.1 (± 2.57) | 57.4 (± 7.98) | 57.7 (± 8.65) | 0.005 |
| Basal respiration (μg CO2 d–1g–1 soil) | 9.9 (± 1.81) | 15.0 (± 2.79) | 19.1 (± 2.92) | 0.09 |
| Nitrification rate (ng NO3 h–1 g–1 soil) | 68.0 (± 2.91) | 69.6 (± 3.06) | 68.8 (± 1.61) | 0.91 |
| Abundance of gene copies (assessed by qPCR)*: | ||||
| 16S (x1010) (g–1 soil) | 2.85 (± 0.44) | 5.61 (± 0.91) | 4.92 (± 0.47) | 0.035 |
| ITS (x108) (g–1 soil) | 0.75 (± 0.14) | 2.23 (± 0.85) | 2.89 (± 1.10) | 0.21 |
| nifH (x108) (g–1 soil) | 2.52 (± 0.67) | 8.50 (± 1.55) | 8.53 (± 2.53) | 0.06 |
| amoA Bacteria (x107) (g–1 soil) | 0.37 (± 0.27) | 1.42 (± 0.67) | 1.48 (± 0.45) | 0.25 |
| amoA Archaea (x107) (g–1 soil) | 2.50 (± 0.46) | 4.04 (± 0.81) | 2.75 (± 0.41) | 0.20 |
| merA (x107) (g–1 soil) | 0.71 (± 0.17) | 1.52 (± 0.34) | 2.45 (± 0.24) | 0.004 |
+Effect of Hg contamination assessed by analysis of variance (ANOVA); significant values (P < 0.05) are in bold. *16S: bacterial 16S gene, ITS: fungal ITS gene, nifH: nitrogenase iron protein gene, amoA: ammonia monooxygenase subunit A gene, merA: mercuric reductase gene.