While microplastics (MPs) are closely associated with ocean contamination, they are also ubiquitous in the soil. One source of terrestrial MPs is plastic mulching, a technique that covers agricultural soil with black sheets of low-density polyethylene (LDPE) to reduce soil erosion, weed growth, evaporation, and enhance plant productivity. Despite the benefits of plastic mulching, recent research suggests these MPs are detrimental to plant and soil health by reducing root nutrient uptake and lowering water retention. This study focuses on transport, observing the effects of soil hematite (Fe₂O₃) concentrations on the vertical movement of LDPE in soils. 

The study will use multi-stage glass columns filled with simulated soil (S_sim), and LDPE initially mixed with the S_sim in the top stage. The main variable of this experiment is the concentration of hematite coating the quartz used as S_sim, which will vary between (0, 5, 10, 15, 22 mg/g quartz) columns. These columns are irrigated with simulated rainwater (R_sim) in wetting and drying cycles to simulate real-world watering conditions. After irrigation, the columns are deconstructed, LDPE is extracted, weighed, and imaged with an infrared microscope (LDIR) to determine the MPs concentration in each layer, revealing the depth of penetration.

This experiment is expected to show less LDPE vertical migration correlated with higher hematite concentrations in S_sim, due to surface charge interactions between LDPE and hematite. These results could be applied to different agricultural soils to determine the extent of MPs transport in soil associated with plastic mulching based on hematite content.