Plastic debris at vines: carriers of pollutants in the environment?

Modern agriculture employs large amounts of plastics, such as mulching and greenhouse films, thermal covers, plant protection tubes and tying tape. The latter two types are very common in viticulture. Guard tubes are employed to protect young vines from mechanic and atmospheric damage, whilst polymeric tying tape has replaced natural-origin materials to hold the canopy of vines. Both materials are made on synthetic polymers, which include a range of additives to improve their environmental stability remaining in the environment of vineyards for years. During this time, they are exposed to the range of pesticides (fungicides, insecticides and in a lesser extend herbicides) applied to vines. Tying tape fits within the category of meso-plastics, difficult to recover due to their abundance and limited size. After pruning, most of the tying tapes end in the soil of vineyards. Both types of materials are potential sources of microplastics during aging.

Depending on the affinity between pesticides and plastics, the latter can act as reservoirs of this kind of pollutants, contributing to their delayed release in the environment of vineyards, and/or serving as carriers of pesticides into the trophic web, and/or into surface waters due to wind and run-off transport. This presentation deals with the characterization of plastic debris collected from vineyards. Thus, the presence of pesticides residues in this matrix were determined, including a comparison with their levels in soil, and the study of the sorption/desorption processes of pesticides in new and aged samples of different types of vineyard plastics.

Residues of pesticides in plastic litter, collected from conventionally managed vineyards, varied from 100 ng g^-1 to more than 10000 ng g^-1. The range of compounds remaining in this matrix included not only moderately lipophilic pesticides, but also medium polarity species, i.e. metalaxyl, carbendazim and dimethomorph. The strength of interaction between pesticides and the two main types of plastic residues identified in vineyards (PE and PP) was mostly controlled by the degree of polymer weathering, which was characterized by FTIR in the total attenuated reflectance mode (ATR).

Acknowledgements: M.C. acknowledges a FPI contract to the Spanish Ministry of Science and Innovation. Funds received from Xunta de Galicia (project ED431C2021/06) are acknowledged.