The effects of three different microplastics on enzyme activities and microbial communities in soil

Abstract

Soils always receive microplastics (MPs) from plastic mulching, compost, and sewage irrigation, but the effects of MPs on soil environment remain largely unexplored. The objectives of this study were to investigate the effects of three MPs (membranous polyethylene (PE), fibrous polypropylene (PP), and microsphere PP) on enzyme activities and microbial community structure in one loamy and sandy soil. The concentration of microsphere PP (2 mg/g) was one-tenth of those of the other two MPs (20 mg/g). The results showed that the effects of three MPs on urease, dehydrogenase, and alkaline phosphatase activities followed the order: fibrous PP > membranous PE > microsphere PP, membranous PE > microsphere PP > fibrous PP and fibrous PP > microsphere PP > membranous PE, respectively. Results from high-throughput sequencing of 16S rRNA revealed that the membranous PE and fibrous PP raised the alpha diversities of the soil microbiota, whereas the diversity indexes of microbiota on MPs surfaces were significantly lower than those in the amended soils. MPs significantly altered the microbial community structure, especially for the enrichment of Acidobacteria and Bacteroidetes, the depletion of Deinococcus-Thermus and Chloroflexi. Aeromicrobium, Streptomyces, Mycobacterium, Janibacter, Nocardia, Arthrobacter were prone to inhabit on the MPs surfaces.

Soil Science Challenges in a New Era: A Transdisciplinary Overview of Relevant Topics

“…However, the study of the interaction of MP with the soil microbial community has received little attention to this time. [80][81][82] It has also been pointed out that plastics could act as carriers of inorganic and organic contaminants in the water-soil interface, releasing these contaminants into the environment and affecting soil (micro-)organisms, with adverse consequences for the food web. 83,84 As a result of increased environmental awareness, biodegradable, oxo-biodegradable, and compostable plastics have been proposed as environmentally friendly alternatives to conventional plastics.…”

Microplastics Increase Soil pH and Decrease Microbial Activities as a Function of Microplastic Shape, Polymer Type, and Exposure Time

“…As a result of their manufacturing origin and environmental degradation, microplastics may occur in many shapes and a variety of physical and chemical properties (Helmberger et al, 2020;Rillig and Lehmann, 2020). The accumulation of microplastics in soil may impact soil characteristics (Liu et al, 2017;Yi et al, 2020), depending on microplastic properties (Lozano et al, 2021a). Indeed, microplastic shape may determine how microplastics interact with soil particles (de Souza Machado et al, 2018;Rillig et al, 2019a;Lehmann et al, 2020;Rillig and Lehmann 2020).…”

“…Microplastics could alter soil microbial communities (Fei et al, 2020;Wiedner et al, 2020;Yi et al, 2020), affecting enzymatic activities (Hargreaves and Hofmockel, 2014). Indeed, recent research has showed that microplastics could affect nutrient and/or substrate availability (Yu et al, 2020;Zhou et al, 2020;Lozano et al, 2021b), likely due to microplastic absorption or its competition for physicochemical niches with microorganisms (Yu et al, 2020).…”

Microplastics in Soils and Sediment: Sources, Methodologies, and Interactions with Microorganisms

“…A study by Markowicz et al determined that microplastics are added to soils from the application of composted biodegradable and oxo-biodegradable plastics (Markowicz and Szymanska-Pulikowska 2019). The presence of microplastic pollutants in soils has been shown to affect natural growth and function of organisms (Boots et al 2019;Yi et al 2020;Lahive et al 2019), and the physical and chemical properties of the soil (Lehmann et al 2019;Machado et al 2018;Zhang et al 2019a). The implications for microbiota are discussed in more detail in the section "Microplastics in Soil and Sediment Microbia."…”