Biodegradable Microplastic-Driven Change in Soil pH Affects Soybean Rhizosphere Microbial N Transformation Processes.

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• The ecological effects of microplastics (MPs), both biodegradable and nonbiodegradable, on soil microbial processes are not well understood.
• Nitrogen (N) transformation is a critical soil function influenced by microbial communities.
• Understanding these impacts is crucial for assessing the environmental risks associated with plastic pollution.

Purpose of the Study:

• To systematically investigate the effects of biodegradable (polybutylene succinate, PBS) and nonbiodegradable (polyethylene, PE) MPs on microbial nitrogen transformation in the rhizosphere of soybean (Glycine max).
• To determine how MPs influence soil properties, plant growth, and microbial community function in different soil types (red and brown soils).

Main Methods:

• Controlled experiments were conducted using soybean plants grown in red and brown soils amended with PBS and PE microplastics.
• Soil parameters including pH and dissolved organic carbon were measured.
• Microbial community composition, diversity, and nitrogen transformation processes (denitrification, ammonification) were analyzed.

Main Results:

• Microplastics altered soil pH and dissolved organic carbon in a manner dependent on MP type and soil type.
• Soybean growth was more sensitive to 1% PBS MP exposure in red soil, which experienced acidification and impeded nutrient uptake.
• PBS MPs negatively impacted microbial community structure, diversity, nitrogen cycling processes, and overall rhizosphere metabolism.

Conclusions:

• Biodegradable MPs, specifically PBS, exert a more significant negative influence on the ecological functions of the plant-soil system compared to nonbiodegradable MPs.
• The findings highlight the potential risks of biodegradable MPs to soil health and agricultural productivity.
• Further research is needed to understand the long-term consequences of biodegradable MPs in terrestrial ecosystems.