Morphological Rather Than Abundance Factors Control Microplastic Accumulation in Wheat Grains: A Field-Based Study

Area of Science:

• Environmental Science
• Agricultural Science
• Materials Science

Background:

• Most microplastic (MP) uptake research is lab-based, lacking real-world field validation.
• Understanding MP accumulation in food crops like wheat is crucial for food safety and environmental health.

Purpose of the Study:

• To investigate microplastic accumulation in wheat grains under conventional farming conditions.
• To correlate grain MP accumulation with soil MP characteristics and properties.

Main Methods:

• Analysis of MP accumulation in two wheat varieties grown in conventional fields.
• Identification and quantification of MPs in wheat grains using Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC/MS).
• Correlation analysis between grain MP content, soil MP abundance, particle size, and shape.

Main Results:

• Consistent MP accumulation trends were observed across two wheat varieties.
• Polyethylene terephthalate (PET) was the most abundant MP in grains, while polystyrene (PS) was least accumulated.
• Grain MP content negatively correlated with particle size (smaller MPs accumulated more) and was influenced by MP shape (fibrous MPs showed reduced uptake).
• No correlation was found between grain MP content and overall soil MP abundance.

Conclusions:

• Microplastic uptake in wheat grains is selective, influenced by particle size and shape, not solely by soil concentration.
• This study identifies MP shape as a significant factor in plant uptake, providing novel mechanistic insights.
• Findings highlight the importance of considering MP characteristics in assessing risks to agricultural systems and food chains.