Assessing the potential chronic, sublethal and lethal ecotoxicity of land-applying biosolids on Folsomia candida and Lumbricus terrestris

The ecotoxicity of biosolids has been studied extensively using single-compound toxicity testing and ‘spiking’ studies; however, little knowledge exists on the ecotoxicity of biosolids as they are land-applied in the Canadian context. The purpose of this study is to elucidate the chronic, sub-lethal (i.e., behavioural), and lethal impacts of land- applying biosolids on the environmentally relevant Folsomia candida (springtails) and Lumbricus terrestris (earthworms) and concomitantly ascertain whether the use of biosolids for nutrient amendment is a sustainable practice. This study is part of a larger multi-compartment programme which includes terrestrial plants and aquatic arthropods. After a review of existing government protocols and research, the current study suggests new environmentally relevant bioassays as to elucidate the true nature of the potential ecotoxicity of land-applying biosolids, within a laboratory context. Specifically, protocols were developed (e.g., shoebox bioassays for L. terrestris sub-lethal testing) or modified (e.g., using Evans’ boxes (Evans 1947) for chronic and sub-lethal testing on L. terrestris ). Subsequently, two biosolids were tested on springtails and earthworms using avoidance and reproductive bioassay endpoints, at application rates that represent standard (8 tonnes ha −1 ) and worst-case scenarios (22 tonnes ha −1 ). Results indicated no effect of biosolids at the environmentally relevant concentration; the worst-case scenario exhibited a positive significantly significant relationship (indicating preference for treatment conditions). We suggest that further assessment of the potential ecotoxicological impact of biosolids employ (i) environmentally relevant organisms, (ii) appropriate bioassays including the use of whole-organism endpoints, and (iii) multi-kingdom testing (e.g., Kingdom Plantae, Animalia) to comprehensively elucidate answers. Lastly, in situ (field assays) are strongly encouraged for future studies.