Effect of emerging contaminants on soil microbial community composition, soil enzyme activity, and strawberry plant growth in polyethylene microplastic-containing soils

Abstract

Microplastic pollution is commonly found in terrestrial ecosystems, yet few studies have investigated its impact on agricultural soils. Herein, we examine the effects of emerging contaminants and high-density polyethylene (HDPE) microplastics (<1 mm) on soil microbial community composition, soil enzyme activity, and strawberry plant growth. The study was conducted outdoors over the span of two years near Montreal, Canada. We found that soils containing emerging contaminants had a significant weighted UniFrac distance from control soils (q = 0.0076). However, when the emerging contaminants were in the presence of 100 mg kg⁻¹ HDPE microplastics, the distance from the control was no longer significant (q = 0.1862). This suggests that HDPE microplastics may mitigate the impact of the emerging contaminants on the soil microbial community. Conversely, no significant differences among treatments were observed in the Shannon's diversity index of the soil microbial community throughout the study. Significant differences in the soil enzyme activity among treatments were rare. At the end of each year's growing season, there were no significant differences in the dry plant biomass, strawberry yield, and the number of leaves and flower stalks between treatments. Many of the endpoints measured showed no significant differences between treatments. Nonetheless, sharing the results of this two-year study, performed outdoors using environmentally relevant concentrations, is important to prevent biased literature and the repetition of resource intensive experiments.