Influence of Poly-3-hydroxybutyrate Micro-Bioplastics and Polyethylene Terephthalate Microplastics on the Soil Organic Matter Structure and Soil Water Properties

Abstract

Adverse effects of microplastics on soil abiotic properties have been attributed to changes in the soil structure. Notably, however, the effects on the supramolecular structure of soil organic matter (SOM) have been overlooked, despite their key role in most soil properties. This work accordingly investigated the influence of plastic residues at various concentrations on the SOM supramolecular structure and soil water properties. To model plastic residues of micro-bioplastics, spherical or spherical-like poly-3-hydroxybutyrate (PHB) was used, while polyethylene terephthalate (PET) was used as a model of conventional microplastics. The results suggest that both types of plastic residues affect SOM properties, including physical stability (represented by water molecule bridges), water binding (represented by decreased desorption enthalpy or faster desorption), and the stability of SOM aliphatic crystallites. The results further showed that the polyester-based microplastics and micro-bioplastics affected the SOM abiotic characteristics and that therefore the observed effects cannot be attributed solely to changes in the whole soil structure. Notably, similar adverse effects on SOM were observed for both tested plastic residues, although the effect of PHB was less pronounced compared to that of PET.

Microplastic Human Dietary Uptake from 1990 to 2018 Grew across 109 Major Developing and Industrialized Countries but Can Be Halved by Plastic Debris Removal

“…Within a few decades, plastics have become the backbone of Anthropocene activities with a 240-fold production growth. 1 Their versatility and low cost in practice have brought in many societal and technical benefits but also critical negative externalities during and after use, 2 particularly due to macro plastic litter and microplastics (MPs, <5 mm) as emerging environmental pollutants. 2 These tiny pollutants can spread to air, water, and soil systems, infiltrating the ecosystem and contaminating the food species incorporated in the food web 3 counteracting with the United Nations’ (UN’s) Sustainable Development Goals (SDGs), including SDG 14 (Life Below Water) and SDG 15 (Life on Land).…”

Cascading Polymer Macro-Debris Upcycling and Microparticle Removal as an Effective Life Cycle Plastic Pollution Mitigation Strategy

“…5 Once exposed to the natural environment, these solid wastes lose their mass denoted by plastic losses 6 from hydraulic weathering or photo-degradation and form macroparticles and microplastics (MPs) less than 5 mm in size. 7 These material losses are transported globally and yield wide dispersal into the air, water, and land-based natural systems. 8 Unlike soluble chemicals or sediments, polymer particles cannot run directly into the mineral cycle aided by biogenic degradation, and their degree of intermingling with the natural environment remains an unmet research need.…”

“…Since waste-recovery processes are not dominant in EoL waste management, most polymer wastes still end in landfills or casual discarding . Once exposed to the natural environment, these solid wastes lose their mass denoted by plastic losses from hydraulic weathering or photo-degradation and form macro-particles and microplastics (MPs) less than 5 mm in size . These material losses are transported globally and yield wide dispersal into the air, water, and land-based natural systems .…”

Distribution of microplastics in soil aggregates after film mulching

“…Agricultural production practices may indirectly impact polyethylene degradation by affecting soil microorganisms, accelerating the fragmentation of polyethylene particles (Zhang et al, 2020). The resulting microplastic residues affect the physical stability (represented by water molecule bridges) and water binding ability (represented by decreased desorption enthalpy or faster desorption) of soil, and the stability of soil organic matter (SOM) aliphatic crystallites (Fojt et al, 2022;Liu et al, 2022). Aggregates comprise soil particles and organic matter cement together and act as the basic building blocks of soil structure.…”

“…The spatial arrangement of primary particles in aggregates forms pore networks, determining the soil structure (Elliott and Coleman, 1988). This in turn controls biogeochemical cycles, soil carbon storage, and carbon processing (Horn et al, 1994), along with the distribution of soil organic carbon (SOC) and other nutrients in soil aggregates (Fojt et al, 2022;Shi et al, 2022a). Yu et al (2021) reported that microplastic contamination decreased the SOC content in soil aggregates greater than 0.25 mm in diameter, but showed the opposite effect on those < 0.053 mm.…”