Radish growth and soil aggregate stability affected by microplastic contamination

The major objective of this study is to investigate changes in radish growth parameters (fresh and dry biomass and photosynthetic efficiency) and the stability of water-stable soil aggregates under contamination by different microplastic materials (high-density polyethylene (HDPE), polyvinyl chloride (PVC), and polystyrene (PS)) in contrasting soil types (Chernozem, Luvisol and Umbrisol). The study was conducted as a pot experiment under laboratory conditions, including three soil types and three microplastic types, with five replicates per variant. The results indicate that the effects of microplastics on plant biomass were significantly dependent on the interaction between soil type and microplastic type. In Chernozem, PS contamination significantly increased both dry and fresh biomass production (by approximately 46% and 50%, respectively) compared with the control. This response was directly associated with increased photosynthetic efficiency and greater stability of water-stable microaggregates in this variant. These findings confirm the stimulatory effect of PS on plant growth in Chernozem. The presence of PS in Chernozem appears to promote the formation of stable microaggregates and decrease macroaggregates, thereby altering the pore system (distribution of micro- and macropores) and supporting plant growth and nutrient absorption. An improvement in the stability of water-stable microaggregates was also observed in Luvisol and Umbrisol under PS contamination (statistically significant in Umbrisol); however, these changes were not reflected in the analysed plant growth parameters. In contrast, HDPE and PVC microplastic pollution had no statistically significant effect on biomass production or photosynthetic efficiency in Chernozem, Luvisol, or Umbrisol. Overall, the findings demonstrate that the effects of microplastic contamination on soil properties and plant growth are strongly influenced by both the type of microplastic polymer and soil characteristics.