The role of polymers as carriers of agrochemicals and contaminants in water environment and agricultural soil

Abstract

The employ of plastic materials in agriculture represents an important cause of environmental pollution. It has been estimated that about over 2 million tons of olefinic plastic films (Low-Density Polyethylene, LDPE) are employed per year worldwide for mulching applications. Over the last years, biodegradable mulching films have been developed to avoid removal, transport, and landfill disposal. However, recent studies have shown that, due to the hydrophobicity properties of biopolymers, agrochemicals and heavy metals are sorbed by biodegradable mulch films in greater quantities than olefin films so that, when these films degrade, the micro-fragments become carriers for contaminants in terrestrial and aquatic environments. This work aims to study this process starting from the adsorption of contaminants on biodegradable mulching films up to the degradation processes of the films, and the transport of the residual contaminants in aquatic environments. These different phenomena constitute the subjects of study of this work. In particular, the phenomenon of the absorption of chemicals on biodegradable plastic films was studied both through laboratory tests, in order to quantitatively describe the adsorption phenomenon, and then field tests on a real crop cycle carried out in the Apulian region, Italy. The research activity then focused on the description of the degradation process of biopolymer films through in situ tests and finally moved on the evaluation of residual contaminants on plastic debris in freshwater environments. In particular, the role of biofilm in the sorption of heavy metals by plastic debris with reference to a Mediterranean aquatic environment, namely the Llobregat river located in Catalonia, Spain, was studied. This study was conducted through an experimental campaign ranging from the collection of plastic debris at various points of the Llobregat bank to tests performed at the laboratories of ICTA-UAB.

Date of Award	30 May 2025
Original language	English
Supervisor	Michael Grelaud . (Director), Giacomo Scarascia Mugnozza (Director) & Patrizia Ziveri . (Director)