Browsing by Subject "Agricultural soil"

Microplastic (MP, <5 mm) contamination of soils has become a critical environmental concern. Plastic mulching films applied in agricultural soils can degrade into MPs, potentially negatively affecting terrestrial ecosystems. Conventional plastics are mainly used in agricultural practices, but the use of biodegradable materials has increased. However, the effects of these polymers on the environment still need to be better understood. The objective of this study was to assess and compare the ecotoxicological effects of mulching film-based microplastics, conventional low-density polyethylene microplastics (PE-MPs) and biodegradable polybutylene adipate terephthalate microplastics (PBAT-BD-MPs), on the earthworm Eisenia andrei. The measured parameters were survival, reproduction, growth, and oxidative stress. In this study, an eight-week reproduction test was conducted using adult earthworms of synchronised age. They were exposed to seven microplastic concentrations: 0%, 0.005%, 0.05%, 0.1%, 0.5%, 1%, 5% (w/w). Oxidative stress was evaluated by analysing six different biomarkers, catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), and lipid peroxidation (LPO). The Integrated Biomarker Response Index (IBR) was provided from biomarker assays, and the soil water-holding capacity and pH were also measured. The results indicated adverse effects on earthworms from both conventional and biodegradable MPs, although impacting different parameters. Responses were observed even at low concentrations; however, no clear dose-response relationship was observed. While exposure to PE-MPs resulted in a decline in earthworm biomass with increasing concentrations, PBAT-BD-MP exposure led to enhanced earthworm growth at lower concentrations. MP exposures did not alter the production of juveniles significantly. However, a minor descending trend in juvenile production was noted with increasing PE-MP concentration, and the juveniles exposed to a 5% concentration of PBAT-BD-MP exhibited lower biomass than the control group. Both MPs caused oxidative stress already at environmentally relevant concentrations. Biomarkers CAT and GR showed significant activation at PE-MP exposure, whereas SOD and LPO levels were impacted at PBAT-MP exposure. This indicates the oxidative damage caused by PBAT-BD-MP exposure. Moreover, both MP types increased soil pH and water-holding capacity at the highest concentration (5%), potentially influencing the observed responses in earthworms subjected to these concentrations. This study provides novel insights into the effects of conventional and biodegradable microplastics on earthworms over various concentrations. Furthermore, it highlights the complexity of microplastics and soil systems, influenced by plastic type, concentration, and environmental conditions.