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

The use of plastic mulching is a well-established technique for the culture of many crops. In this practice the cultivated soil is covered by a polymer film, aiming at keeping constant soil temperature, reducing water evaporation and lowering the employ of agrochemicals The most common mulch films are olefinic plastic films (Low-Density Polyethylene, LDPE) that need to be removed after their life cycle and disposed of. Over the last years, biodegradable mulching films have been developed to avoid removal, transport, and landfill disposal. In particular, an important role is played by biobased polymers produced from a biomass source, in contrast to the other types of polymers originating from an oleochemical source, represent an important effort in reducing the dependence on fossil sources and create a positive environmental impact by reducing greenhouse gas emissions. In this vein, the European Commission has determined that biobased polymers are of great interest due to, among other things, their lower carbon footprint. Recent studies have shown that, due to the hydrophobicity properties of biopolymers, agrochemicals are sorbed by biodegradable mulch films in greater quantities than olefin films so that, when these films degrade, the micro-fragments become carriers for agrochemicals in terrestrial and aquatic environments. This work aims to study this process starting from the adsorption of agrochemicals on biodegradable mulching films up to the degradation processes of the films, and the transport of the residual agrochemicals in aquatic environments. The study of this complex process requires the understanding of different phenomena that constitute the subjects of study of this work. In particular, the phenomenon of the absorption of agrochemicals 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. 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 agrochemicals on plastic debris in freshwater environments. In this work we focused on a specific geographical area, namely the southern Mediterranean area. To this end, the field tests were carried out in the Apulian region, Italy, and in Catalonia, Spain.