Enhanced Transport of TiO₂ in Unsaturated Sand and Soil after Release from Biodegradable Plastic during Composting

Abstract

Biodegradable plastics can reach full degradation when disposed of appropriately and thus alleviate plastic pollution caused by conventional plastics. However, additives can be released into the environment during degradation and the fate of these additives can be affected by the degradation process. Here, we characterized TiO2 particles released from a biodegradable plastic mulch during composting and studied the transport of the mulch-released TiO2 particles in inert sand and agricultural soil columns under unsaturated flow conditions. TiO2 particles (238 nm major axis and 154 nm minor axis) were released from the biodegradable plastic mulch in both single-particle and cluster forms. The mulch-released TiO2 particles were fully retained in unsaturated soil columns due to attachment onto the solid–water interface and straining. However, in unsaturated sand columns, the mulch-released TiO2 particles were highly mobile. A comparison with the pristine TiO2 revealed that the mobility of the mulch-released TiO2 particles was enhanced by humic acid present in the compost residues, which blocked attachment sites and imposed steric repulsion. This study demonstrates that TiO2 particles can be released during composting of biodegradable plastics and the transport potential of the plastic-released TiO2 particles in the terrestrial environment can be enhanced by compost residues.

Mobility of soil-biodegradable nanoplastics in unsaturated porous media affected by protein-corona

“…[43][44][45] In addition, the near 100% recovery suggests that nanoplastics did not attach onto the sand-water interface nor the air-water interface. 22 Indeed, the classical DLVO calculation revealed a repulsive interaction energy for the three types of nanoplastics interacting with the sand-water interface and the air-water interface (Fig. S8A and B †).…”

“…The transport experiments were carried out with the same unsaturated flow system used in our previous studies. 21,22 Briefly, the system consisted of a Plexiglass column (5 cm inner diameter and 15 cm length), a perforated bottom metal plate covered with a 20 μm nylon membrane (NM-E #635, Gilson Company, Inc., Lewis Center, OH), and a hanging water tube connected at the bottom of the metal plate to provide suction and establish unsaturated flow in the column. Inflow was injected with a peristaltic pump and a 12-needle sprinkler at the top of the column, and outflow was sampled with a fraction collector.…”

Unlocking the Potentials of Biodegradable Plastics with Proper Management and Evaluation at Environmentally Relevant Concentrations

“…Concerns have also arisen about the release of additives, such as fillers, plasticizers, colorants, and UV-stabilizers, from biodegradable plastics during degradation 41,56,57 . While this release of additives is an expected process of the biodegradation in the environment, the released additives could pose environmental threats.…”