Assessment of heavily weathered petroleum hydrocarbon-impacted soils to native soil invertebrates from a Canadian subarctic site

Purpose Risks to native soil-dwelling organisms in terrestrial ecosystems contaminated by petroleum hydrocarbons (PHCs) are difficult to assess due to the range of compounds and their varying toxicity. Weathering of PHCs in soil has been shown to alter their chemical composition and decrease their associated toxicity. Hence, generic regulatory guidelines may inadequately predict risks and exposure scenarios at some sites. Methods In this study, the toxicity of both coarse- and fine-grained subarctic soils contaminated with weathered PHCs was assessed using two soil invertebrates, Folsomia candida and Proisotoma minuta . In addition to survival and reproduction tests, avoidance behavior was investigated using F. candida , P. minuta , Oppia nitens , and Folsomia bisetosa . Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results and verified the sensitivity of F. candida and P. minuta to contaminants. Results Despite exceeding the Canada-wide generic guidelines for PHC fraction 3 (F3), weathered contaminated soils at concentrations between 1140 and 5880 mg/kg had no significant negative impacts on the reproduction or mortality rates of F. candida or P. minuta . Furthermore, all four soil invertebrates preferred to inhabit the contaminated soils during the 48 h avoidances tests. Conclusion Natural weathering processes to PHC-impacted soils at a Canadian Subarctic site have led to a decrease in toxicity on four native soil invertebrates.