Assessment of the occurrence and interaction between pesticides and plastic litter from vineyard plots

The fingerprint of pesticides in agricultural used polyethylene

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.

Polyethylene fragments in Argentinean horticultural soils: Environmental transformation to a composite material

Polyethylene macro, meso, and microplastics collected from horticultural soils in Moreno, Buenos Aires, Argentina, were studied to understand their physicochemical transformations after environmental exposure. These plastics contained mechanically stable compounds of Si (1.2-4.0 %), Al (0.91-1.5 %), and Fe (0.64-2.2 %), likely due to soil clay particles adhering to the plastic. The plastics' surfaces were oxidized, with high carbonyl (0.05-0.23) and hydroxyl (1.6-2.7) indices. Weathering led to thinner, rougher surfaces with increased contact angles due to the presence of clay and polar organic groups. Scanning electron microscopy (SEM) showed cracks and particles on the surfaces, while atomic force microscopy (AFM) revealed roughness increased from 0.44 nm in pristine polyethylene (p-PE) to 1.60 nm in weathered samples. Heavy metal sorption experiments showed that the weathered plastics absorbed significantly more Ni2+ and Pb2+ than unweathered PE (4.5 times for Ni2+ and 11 times for Pb2+). After removing clay with hydrofluoric acid, the plastics still retained the same amount of these metals, suggesting that the sorption occurred mainly on the modified plastic surface rather than the clay. Arsenate tests indicated that the plastics selectively absorbed cationic metals. This study also developed a simple ATR-FTIR method for quantifying silicate on polyethylene surfaces, contributing to an understanding of soil-derived particle interactions with plastic in agricultural settings.

Identification of hazardous organic compounds in e-waste plastic using non-target and suspect screening approaches

End-of-life electric and electronic devices stand as one of the fastest growing wastes in the world and, therefore, a rapidly escalating global concern. A relevant fraction of these wastes corresponds to polymeric materials containing a plethora of chemical additives. Some of those additives fall within the category of hazardous organic compounds (HOCs). Despite the significant advances in the capabilities of analytical methods, the comprehensive characterization of WEEE plastic remains as a challenge. This research strives to identify the primary additives within WEEE polymers by implementing a non-target and suspect screening approach. Gas chromatography coupled to time-of-flight mass spectrometry (GC-QTOF-MS), using electron ionization (EI), was applied for the detection and identification of more than 300 substances in this matrix. A preliminary comparison was carried out with nominal resolution EI-MS spectra contained in the NIST17 library. BPA, flame retardants, UV-filters, PAHs, and preservatives were among the compounds detected. Fifty-one out of 300 compounds were confirmed by comparison with authentic standards. The study establishes a comprehensive database containing m/z ratios and accurate mass spectra of characteristic compounds, encompassing HOCs. Semi-quantification of the predominant additives was conducted across 48 WEEE samples collected from handling and dismantling facilities in Galicia. ABS plastic demonstrated the highest median concentrations, ranging from 0.154 to 4456 μg g-1, being brominated flame retardants and UV filters, the families presenting the highest concentrations. Internet router devices revealed the highest concentrations, containing a myriad of HOCs, such as tetrabromobisphenol A (TBBPA), tribromophenol (TBrP), triphenylphosphate (TPhP), tinuvin P and bisphenol A (BPA), most of which are restricted in Europe.