In TRAMPAS we brought together a wide range of approaches through multidisciplinary studies to explore two challenges of societal importance including microplastic soil pollution and pathogen fate in the environment.
First Study. Microplastics, specifically polypropylene (PP) and polyethylene (PE), impact soil aggregate stability, with effects varying based on factors like chemistry, concentration, size, and degradation. Through experiments involving different concentrations, sizes, and incubations of microplastics in soil, we utilized high-energy moisture characteristic curves to assess soil wetting rates and stability. Results showed that higher microplastics concentrations increased drainable pores, especially with larger particles. Both PE and PP microplastics tended to increase modal matric suction, more pronounced in fast wetting. The incorporation of microplastics led to increased soil structural index and stability ratio, indicating significant impacts on soil structure and aggregate stability.
Second Study. Silica-DNA microparticles served as surrogates, along with bromide. Microplastics (PP and PE) were mixed with sand particles (0.5% w/w) and tested in packed columns. PE-treated columns exhibited faster breakthrough during the first pulse compared to PP and controls. Similar trends were observed for bromide concentrations. Microplastics type influenced the arrival of bromide during the second pulse. Microplastics-treated columns showed higher bromide mass recovery, with retention of silica-DNA microparticles being lower in contaminated soil. MiP size and chemistry affected retention, demonstrating accelerated bacteria tracer transport in microplastics-affected soils.
Third study. This study investigates the mobility of polyethylene (PE)-derived additives in soil under different heating and leaching conditions. Soil columns were exposed to varying temperatures (no heating, 60°C, 80°C) and leaching methods (continuous and interrupted). Breakthrough curves (BTCs) revealed that previous temperature exposure and leaching conditions affected the retention of additives and Br− transport in soil. Values for PE-derived additives were influenced by temperature and leaching conditions. Additives also altered surface tension and viscosity in water. Overall, the study’s findings have implications for understanding the impact of microplastics-derived additives on water infiltration, plant uptake, and the potential transport of contaminants like heavy metals.
Fourth study. This study investigated microplastics degradation in soil, examining changes in soil and plastisphere interfacial properties. Polypropylene and polyethylene microplastics were mixed with sandy loam at different proportions and incubated for six months. Assessments included contact angle (CA), surface tension, and surface elemental compositions using advanced techniques. Fluorescence microscopy and scanning electron microscopy visualized degradation. Results showed a significant increase in CA values for PE-treated soils over time, indicating enhanced degradation. Plastispheres in both PP and PE-treated soils had higher CA values than the control, suggesting the release of degraded microplastics. In-depth analyses revealed substantial transformations in soil and plastisphere chemistry and surface tension after 180 days. The findings highlight the potential of CA and surface elemental compositions as indicators for monitoring microplastics degradation in soils and plastisphere development.
