Table 4.
Summary and Comparison of Fertility Parameters in Surface Soils (0–30 cm).
| Parameters | Control Soil | Remediated Soil | Importance |
|---|---|---|---|
| Parameters very likely related to soil degradation from contamination or remediation technique | |||
| Proportion fine to coarse particles (clay + silt):sand | 62:38 | 77:23 | May cause compaction, reduced infiltration, reduced root penetration, reduced gas exchange |
| OM (%) | 0.81 | 0.26 | Reduces CEC, CIC, may reduce moisture content and availability of soil nutrients |
| FC (%) | 35.0 | 30.0 | Reduces moisture retention, may cause water stress, wilting |
| Po (%) | 54.1 | 49.8 | May cause compaction, reduced infiltration, reduced root penetration, reduced gas exchange |
| BD (g cm−3) | 11.1 | 12.3 | May cause compaction, reduced infiltration, reduced root penetration, reduced gas exchange |
| Compaction (MPa) | 0.84–1.10 | 1.32–3.04 | Reduces water infiltration, root penetration, free gas exchange (respiration of soil organisms); about two to three times greater in remediated soil |
| H (%) | 22.9 | 12.5 | May cause water stress and wilting; about half as much moisture in remediated soil |
| Depth of roots (soil profile, cm) | 118 | 3–10 | Sign of unfertile conditions for plant growth, possible due to compaction |
| Presence of insects and spiders (soil profile, cm) | 0–118 | 0–63 | Sign of poor conditions, possibly due to poor plant growth (root penetration, primary productivity) and less food available |
| Parameters very likely not related to soil degradation from contamination or remediation technique | |||
| TPH (mg kg−1) | 182 | 969 | Low levels, no significant correlation found between TPH and other factors (R2 < 0.7) in remediated soil |
| pH | 7.1–8.0 | 7.4–8.5 | Mildly alkaline but in same range as subsurface of control soil (7.9–8.4); probably not detrimental to soil fertility |
| WDPT (s) | 0.48–0.59 | 1.26 | Levels classified as “null” |
| Toxicity | NA | NA | No relationship was found between the soil concentration in the bioassay and response of the test organisms (all samples considered non-toxic) |
Soil Organic Matter (OM), Field Capacity (FC), Porosity (Po), Bulk Density (BD), Moisture Content (H), Total Petroleum Hydrocarbons (TPH), Water Drop Penetration Time (WDPT), not applicable (NA). Note: depth of roots and presence of ants and spiders is presented for the entire soil profile, not just 0–30 cm.