Effect of Agricultural Organic Inputs on Nanoplastics Transport in Saturated Goethite-Coated Porous Media: Particle Size Selectivity and Role of Dissolved Organic Matter

The transport of nanoplastics (NPs) through porous media is influenced by dissolved organic matter (DOM) released from agricultural organic inputs. Here, cotransport of NPs with three types of DOM (biochar(DOM) (BCDOM), wheat straw(DOM) (WSDOM), and swine manure(DOM) (SMDOM)) was investigated in saturated goethite (GT)-coated sand columns. The results showed that codeposition of 50 nm NPs (50NPs) with DOM occurred due to the formation of a GT-DOM-50NPs complex, while DOM loaded on GT-coated sand and 400 nm NPs (400NPs) aided 400NPs transport due to electrostatic repulsion. According to the quantum chemical calculation, humic acid and cellulose played a significant role in 50NPs retardation. Owing to its high concentration, moderate humification index (HLX), and cellulose content, SMDOM exhibited the highest retardation of 50NPs transport and promoting effect on 400NPs transport. Owing to a high HIX, the effect of BCDOM on the mobility of 400NPs was higher than that of WSDOM. However, high cellulose content in WSDOM caused it to exhibit a 50NPs retardation ability that was similar to that of BCDOM. Our results highlight the particle size selectivity and significant influence of DOM type on the transport of NPs and elucidate their quantum and colloidal chemical-interface mechanisms in a typical agricultural environment.

Automated summary

This study investigates the co-transport of nanoplastics (NPs) and dissolved organic matter (DOM) released from agricultural organic inputs in porous media. The results show that the co-deposition of NPs with DOM occurs due to the formation of a complex, while DOM loaded on the porous media aids NP transport due to electrostatic repulsion. Quantum chemical calculations suggest that humic acid and cellulose play a significant role in NP retardation. The type of DOM also affects the transport and retardation of NPs.