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

Most microplastic (MP) uptake studies are lab-based, lacking field validation. This study analyzes MP accumulation in wheat grains under conventional farming, linking it to soil MP properties. Two wheat varieties showed consistent accumulation trends. Py-GC/MS identified polyethylene terephthalate (PET) as the most abundant grain MP (5.70 ± 0.41 mg/kg), while polystyrene (PS) was least accumulated (0.82 ± 0.12 mg/kg) despite higher soil PS levels, indicating selective uptake. Grain MP content did not correlate with soil MP abundance but negatively correlated with particle size (p < 0.001): PET and PE (20-40 μm) accumulated more than polyvinyl chloride (PVC) (70-80 μm). MP shape also influenced uptake (p < 0.05); fibrous PS likely hindered absorption. This study is the first to identify MP shape as a key factor in plant uptake, offering new mechanistic insights.