The fingerprint of pesticides in agricultural used polyethylene

Abstract

The widespread use of polyethylene (PE) materials in agriculture through mulch films, tunnels, greenhouse covers, irrigation pipes and tying tapes has been instrumental in increasing crop productivity and reducing water demand. However, it raised concerns regarding the interaction between PE and pesticides sprayed on crops. This research strives to study the fingerprint of pesticides in agricultural PE by analyzing new items, end-of-life agricultural plastics and a range of samples corresponding to the recycling of aged PE, from sized and washed flakes to second-hand pellets and plant protection tubes elaborated from recycled plastic. Total concentrations determined for a selection of fungicides and insecticides in the abovementioned materials varied between 4.7 ng g⁻¹ and 4179 ng g⁻¹, with the fungicides cyprodinil and difenoconazole showing the highest concentrations. Furthermore, transformation products of pesticides phased out more than 40 years ago, e.g., p,p’-DDE, were found in some PE items. The survival of pesticides at temperatures above the melting point of this polymer was confirmed in laboratory-scale melting experiments, as well as through the analysis of second-hand pellets. Experiments carried out using pesticide-polluted dripline pipes confirmed the migration of these compounds from PE to flowing water.