Assessment of soil quality using bioaccessibility-based models and a biomarker index.

Bioavailability in heterogeneous media such as soils is a multi-factorial concept which ranges from soil chemistry to toxicity. The complexity of this factor has been tackled by various studies pinpointing its relevancy for laboratory to field extrapolation of toxicity data. As contaminant bioavailability on these sites is virtually unknown, a global assessment of this issue has been conducted on soils impacted by antitank firing from a Canadian Range and Training Area (RTA) and contaminated by energetic materials (EM) and metals. Yet, the descriptive results acquired from this survey require further in-depth analysis so as to enhance understanding of soil health status. Statistical models as well as an index integrating biomarker responses were derived from this database and are proposed as diagnostic, explanatory and possibly predictive tools for soil bioavailability and quality assessment. Relationships associating bioaccessible contaminant levels to soil properties allowed to clarify contaminant behaviour in energetic material (EM)-contaminated soils. Likewise, models expressing biomarker responses as a function of bioaccessible contaminant concentrations contributed to identify the contaminants causing toxicity in earthworms and to the comprehension of those toxic effects. The index of biomarker response was adapted from similar concepts applied in the aquatic environment and is an original contribution to terrestrial sites. The biomarker index data were in agreement with soil contamination profiles and represent therefore an interesting tool for soil quality appraisal. Such tools also offer a promising potential for the management of contaminated soils.