The eco-corona on
microplastics refers to the initial layer of
biomolecular compounds adsorbed onto the surface after environmental
exposure. The formation and composition of the eco-corona in soils
have attracted relatively little attention; however, the eco-corona
has important implications for the fate and impacts of microplastics
and co-occurring chemical contaminants. Here, it was demonstrated
that the formation of the eco-corona on polyethylene microplastics
exposed to water-extractable soil metabolites (WESMs) occurs quite
rapidly via two pathways: direct adsorption of metabolites on microplastics
and bridging interactions mediated by macromolecules. The main eco-corona
components were common across all soils and microplastics tested and
were identified as lipids and lipid-like molecules, phenylpropanoids
and polyketides, nucleosides, nucleotides, and their analogues. WESMs
were found to reduce the adsorption of co-occurring organic contaminants
to microplastics by two pathways: reduced adsorption to the eco-corona
surface and co-solubilization in the surrounding water. These impacts
from the eco-corona and the soil metabolome should be considered within
fate and risk assessments of microplastics and co-occurring contaminants.