Assessing the Potential Chronic, Lethal, and Multigenerational Ecotoxicity of Land-Applying Biosolids using Zea mays, Glycine max, Phaseolus vulgaris and Brassica rapa

Abstract

Abstract The uncertainty of potential toxicity when land-applying municipal biosolids to agricultural fields needs to be clarified considering the concomitant benefit for nutrient amendment and sustainability of resource recovery. This research is part of a larger program that assessed the toxicity of biosolids to terrestrial and aquatic organisms and this study specifically examined the toxicity of two biosolids when applied to four environmentally-relevant field crops. New bioassays were necessary to test the ecotoxicity of biosolids throughout the entire life cycle of each crop: Zea mays (corn), Glycine max (soybeans), Phaseolus vulgaris (common bean), and Brassica rapa (field mustard). It was hypothesized that biosolids would exhibit impact at both an environmentally-relevant application rate (8 tonnes ha-1) and a worst-case scenario (22 tonnes ha-1). The ecotoxicity of biosolids was tested using chronic, lethal, and multigenerational endpoints (i.e., F1 generation viability). Overall, study findings indicated a positive response to nutrient amendment using biosolids at either application rate. Negative responses to biosolids were seen in early growth stages of some cultivars (Zea mays) but disappeared or became positive as plants matured: these observations would have been made if existing protocols had been followed. Brassica rapa exhibited a negative germination rate when exposed to biosolids; however, further work is necessary to elucidate whether the effect is a result of nutrient additions or physical compaction on the small seed. The complete life-cycle bioassays of crops suggest that plants grown in the biosolids-amended soil were significantly larger and produced more seeds compared to reference assays. These results lend scientific support for their sustainable use in land-application strategies in Canada.