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A comparative study of microplastics under the influence of soil-typical eco-coronas through laboratory and field incubation experiments
Summary
Researchers compared microplastic behavior under laboratory and field incubation conditions when eco-coronas — natural surface coatings of organic matter, proteins, and humic acids — were present on particles, assessing how these coatings modify microplastic hydrophobicity, transport, and toxicity to soil organisms.
Microplastics (MPs), ubiquitous in terrestrial environments, are usually covered by an eco-corona (EC) under natural conditions. When mistakenly ingested by soil organisms, MPs could harm their development, reproduction, and survival rates. The EC, a natural layer on MP surfaces, contains organic matter like carbohydrates, proteins, DNA, and compounds like humic and fulvic acids. It strongly influences the transport and behaviour of MPs, by altering their hydrophobicity, thereby affecting their adsorption efficiency. While limited research on EC formation on MP in aquatic environments exists, our understanding of typical ECs in soils is limited. Our study aims to address critical research questions regarding the identification, formation, and variation of EC on MPs in floodplain soils, and physico-chemical changes induced on MP's surface under different incubation conditions. We conducted experiments in both field and laboratory settings, collecting floodplain soils from Northern floodplains in Cologne, Germany. Polystyrene MPs (600-1000 microns) were incubated with soil samples in cylindrical chambers (mesh size 500 microns) for 4, 8, and 16 weeks. Laboratory-incubated samples were monitored for temperature and moisture, while the field incubations were left to be controlled by natural conditions. Additional soil parameters, including pH, CN content, grain size, and elemental composition, were also analyzed. After each incubation period, MPs were extracted manually and preserved at -28°C. The MPs were analyzed, employing 16S-V4 and ITS1 for metabarcoding and sequencing for attached ECs (bacteria and fungi), SEM imaging for visual inspection, ATR-FTIR spectroscopy for polymer-level analysis, and the Electroacoustic Sonic Amplitude system to identify the zeta potential of MPs to quantify the surface charge. We hypothesize that incubation duration influences EC formation and stability, altering MP's surface morphology, and surface charge. Our findings will contribute to understanding EC-mediated processes in soil ecosystems, providing insights into MPs' ecological impacts. Also see: https://micro2024.sciencesconf.org/559218/document