Effect of plastic pollution in soil properties and growth of grass species in semi-arid regions: a laboratory experiment

Since the year 2020, the use of plastic as a strategy to mitigate the spread of COVID-19 disease has been given substantial attention. Global environmental contamination of plastic creates waste and is a known threat to soil ecosystems as a main sink of microplastics. However, there is still considerable uncertainty about microplastics controlling soil properties alteration. Therefore, we carried out an incubation experiment with soil and Carex stenophylla Wahlenb., which are the dominant soil and grass species in semi-arid regions. We investigated the effect of polymer polyethylene terephthalate (PET) concentrations (0%, 1%, 3%, and 5%) on C. stenophylla growth and soil ammonium-N and nitrate–N, organic matter content, pH, soil aggregates, and soil respiration. When soils were exposed to PET microplastics, fewer seeds germinated (62.8 ± 32%) but not significantly (p value > 0.05) when soils were treated to 0, 1, 3, and 0.5% PET. Shoot height was also not effectively reduced with PET. The soil pH was considerably lower when exposed to higher PET compared to all other treatments with the soil exposed to 5% w/w PET for both unplanted and planted, being 0.84 and 0.54 units, respectively, lower than the controls. The soil microbial respiration under exposure to PET was considerably increased in comparison to control samples. Moreover, the presence of PET resulted in potential alterations of soil stability, and with PET present soil stability increased. In conclusion, PET microplastics cannot significantly affect the development of C. stenophylla but could affect crucial soil properties. In addition, changes occurred with increased variability in soil ammonium-N and nitrate–N, particularly at a high PET ratio.