Evaluating PFHxS toxicity to invertebrates and microbial processes in soil

Per- and poly-fluoroalkyl substances (PFAS) have raised global concerns regarding soil contamination and the subsequent adverse effects on soil organisms. PFOS, PFOA, and PFHxS are among the commonly detected PFAS in the environment with much attention directed to PFOS and PFOA and minimal information available on the toxicity of PFHxS for ecotoxicological assessments. Therefore, this study focuses on the toxic potential of PFHxS to soil biota. The effects of PFHxS to microbial processes and earthworms were assessed in a wide range of concentration (0–1000 mg/kg) in soil to define the safe concentration. The soil enzyme activities (dehydrogenase activity and soil respiration rate) were significantly reduced after exposure to PFHxS at concentrations exceeding 100 mg/kg. The bacterial community suffered more than the fungal community upon PFHxS exposure. Bacterial diversity and richness were inhibited due to PFHxS exposure. However, at taxonomic level, growth of some bacterial phyla was stimulated (e.g., Actinobacteria) while others were inhibited (e.g., Acidobacteria). Earthworm survival was also significantly affected at concentrations exceeding 100 mg/kg. Our findings showed that exposure to PFHxS negatively affects the soil microbial processes and earthworm survival, potentially jeopardising their functions.