Remediation programmes are considered complete when human risk-based criteria are met. These targets are unrelated to the ecological parameters that may be important with regard to future soil uses. As a consequence, there has been a move towards the consideration of biological indicators for hazard assessment in conjunction with the remediation of contaminated soils. This study uses a range of biological assays to assess the ecological health of soils from a former gas works site undergoing various remediation treatments. The indicators that optimally differentiated the extent of soil remediation were biomass-C, respiration, dehydrogenase activity, earthworm toxicity and mustard seed germination. Although they had different end-points, once robust and sensitive biological indicators were incorporated into a quantitative soil quality index, they gave a clearer representation of ecological health than chemical data alone by their integration of contamination effects at a number of trophic levels.
Dawson, J. J. C., Godsiffe, E. J., Thompson, I. P., Ralebitso-Senior, T. K., Killham, K. S., & Paton, G. I. (2007). Application of biological indicators to assess recovery of hydrocarbon impacted soils. Soil Biology and Biochemistry, 39(1), 164-177. https://doi.org/10.1016/j.soilbio.2006.06.020