An approach for evaluating the level of plastic residues in agricultural soils

There is a continuous increase of the use of plastic materials globally, which makes difficult to manage their waste, constituting an important source of pollution for the different environmental areas. Specifically, the long-term quality and productivity of agricultural soils is affected by the contamination of these plastic residues, being these pollutants mainly present as microplastics coming from the degradation of the larger initial plastic contaminants. In addition, plastics contain different additives to improve their properties which are normally toxic organic compounds which may have a negative impact to the agricultural environment.

The purpose of this research is to develop and validate an analytical method based in a solid-liquid extraction stage followed by gas chromatography coupled to mass spectrometry (GC-MC) to determine volatile organic compounds related to plastics (monomers, additives, and degradation products) in soil samples of agricultural areas. For this purpose, a number of samples were collected in a wide zone located in the Rambla del Beal (Cartagena, Spain).

The optimized method has allowed the quantification of 14 volatile compounds, such as styrene, phthalates or bisphenol A that may be released from plastic residues, because they are monomeric species or additives. Other species associated to the degradation (environmental conditions over time) of the plastic residues such as 2,4-diterbutylphenol have been also found in the samples.

In addition, a non-targeted approach has been developed for the identification of other pollutants present in the soil samples without the use of standards. This goal was achieved by the use of the mass spectrometer detector working in the full scan mode and the application of MS database libraries (NIST and Wiley).

This analytical methodology represents a basis for a reliable evaluation of the presence of plastic pollutants in soils through the determination of their additives, monomers and degradation compounds.

 

The authors are grateful to the Spanish MICINN (Project PGC2018-098363-B-100) for financial support