Introduction

One of the environmental pollutants that has become a global concern is microplastics. This study investigates the impact of two types of microplastics, polyethylene terephthalate (PET) and polyester, on soil characteristics. The objective of this research is to examine the effects of polymeric microplastic particles of polyethylene terephthalate and polyester on certain soil properties, including soil acidity, soil respiration, microbial biomass carbon, and soil microorganism biodiversity. One of the environmental pollutants that has become a global concern is microplastics. This study investigates the impact of two types of microplastics, polyethylene terephthalate (PET) and polyester, on soil characteristics. The objective of this research is to examine the effects of polymeric microplastic particles of polyethylene terephthalate and polyester on certain soil properties, including soil acidity, soil respiration, microbial biomass carbon, and soil microorganism biodiversity.

Materials and methods
For this purpose, microplastic particles smaller than 5 mm were added to the soil at weight percentages of 1%, 3%, 5%, and 10%. The incubation period for assessing the soil characteristics was 60 days. To prepare the soil, the samples were passed through a 2 mm sieve and placed into standardized one-liter plastic jars, which were labeled according to the respective percentages of microplastics added. The prepared samples were then allowed to rest for a duration of two months, during which temperature and humidity were maintained consistently, and parameters such as pH and electrical conductivity were measured. At the end of the resting period, the effects of different types of microplastics at specified weight percentages on the physical, chemical, and biological properties of the soil were assessed. Additionally, the impact on microorganism diversity and distribution was compared with control samples.Additionally, the impact on microorganism diversity and distribution was compared with control samples.
Results and discussion
The results indicated that the addition of microplastic particles to the soil led to a decrease in soil respiration over time. Specifically, for the treatments containing microplastic at the 1% level, soil respiration increased from 24.45 mg CO₂ per kg of soil per day to 38.12 mg CO₂ per kg of soil per day, while at higher levels, at 10% polyethylene terephthalate, it decreased to 30.45 mg CO₂ per kg of soil per day, and in the polyester treatment, it reduced to 27.47 mg CO₂ per kg of soil per day.
Furthermore, at the beginning of the research, the microbial biomass carbon level in the soil at the 1% level increased from 7.43 mg carbon per kg of soil to 21.36 mg carbon per kg of soil (for the polyethylene terephthalate treatment) and 21.97 mg carbon per kg of soil (for the polyester treatment). However, over time, at higher levels (10%), the microbial biomass carbon decreased to 12.82 mg carbon per kg of soil for polyethylene terephthalate and to 11.96 mg carbon per kg of soil for polyester. This indicates an inverse relationship between microplastic concentration and biomass carbon. Additionally, over time, negative effects of microplastics on soil biodiversity became evident, with a decrease in biodiversity observed at the 1% level compared to the control treatment, while other levels (3%, 5%, and 10%) exhibited increases.For this purpose, microplastic particles smaller than 5 mm were added to the soil at weight percentages of 1%, 3%, 5%, and 10%. The incubation period for assessing the soil characteristics was 60 days. To prepare the soil, the samples were passed through a 2 mm sieve and placed into standardized one-liter plastic jars, which were labeled according to the respective percentages of microplastics added. The prepared samples were then allowed to rest for a duration of two months, during which temperature and humidity were maintained consistently, and parameters such as pH and electrical conductivity were measured. At the end of the resting period, the effects of different types of microplastics at specified weight percentages on the physical, chemical, and biological properties of the soil were assessed. Additionally, the impact on microorganism diversity and distribution was compared with control samples.
Results and discussion
The results indicated that the addition of microplastic particles to the soil led to a decrease in soil respiration over time. Specifically, for the treatments containing microplastic at the 1% level, soil respiration increased from 24.45 mg CO₂ per kg of soil per day to 38.12 mg CO₂ per kg of soil per day, while at higher levels, at 10% polyethylene terephthalate, it decreased to 30.45 mg CO₂ per kg of soil per day, and in the polyester treatment, it reduced to 27.47 mg CO₂ per kg of soil per day.
Furthermore, at the beginning of the research, the microbial biomass carbon level in the soil at the 1% level increased from 7.43 mg carbon per kg of soil to 21.36 mg carbon per kg of soil (for the polyethylene terephthalate treatment) and 21.97 mg carbon per kg of soil (for the polyester treatment). However, over time, at higher levels (10%), the microbial biomass carbon decreased to 12.82 mg carbon per kg of soil for polyethylene terephthalate and to 11.96 mg carbon per kg of soil for polyester. This indicates an inverse relationship between microplastic concentration and biomass carbon. Additionally, over time, negative effects of microplastics on soil biodiversity became evident, with a decrease in biodiversity observed at the 1% level compared to the control treatment, while other levels (3%, 5%, and 10%) exhibited increases.


Conclusion
Overall, the findings of this study demonstrate that microplastics have complex effects on the environment and soil ecosystems, and their impact on microbial activity is intricate and dependent on concentration and type. While microplastics may present opportunities for improving soil quality, they pose serious risks at higher levels. Hence, there is a need for further studies to fully understand their consequences.
Overall, the findings of this study demonstrate that microplastics have complex effects on the environment and soil ecosystems, and their impact on microbial activity is intricate and dependent on concentration and type. While microplastics may present opportunities for improving soil quality, they pose serious risks at higher levels. Hence, there is a need for further studies to fully understand their consequences.