Abstract
Lake basins can behave as accumulators of microplastics released in wastewaters as such or resulting from degradation of larger items before and/or during their journey toward the marine environment as a final sink. A novel multianalytical approach was adopted for the detection and quantification of microplastics with size < 2 mm in the sediments of the volcanic lake of Bracciano, Italy. Simple analytical techniques such as solvent extraction/fractionation (for polyolefins and polystyrene) or depolymerization (for polyethylene terephthalate, PET), along with chromatographic detection (SEC and HPLC), allowed quantitative and qualitative determination of the main synthetic polymer contaminants. In particular, PET microplastic concentrations of 0.8–36 ppm were found, with variability related to the sampling site (exposure to incoming winds and wave action). Proton Nuclear Magnetic Resonance (1H-NMR) and Attenuated Total Reflectance Fourier Transformed InfraRed (ATR-FTIR spectroscopic investigations supported the identification and chemical characterization of plastic fragments and polymer extracts. The average molecular weight of solvent extractable polymers was evaluated from 2D 1H-NMR diffusion ordered spectroscopy (DOSY) experiments. The proposed, easily accessible multianalytical approach can be considered as a useful tool for improving our knowledge on the nature and the concentration of microplastics in sediments, giving insights on the impact of human activities on the health status of aquatic ecosystems.
Highlights
Environmental pollution by microplastics (MPs) and nanoplastics (NPs) has raised growing concerns in the last two decades, as a result of the increasing evidences regarding the direct and indirect negative effects of such contaminants on both marine [1] and soil biota [2,3], and the potential of bioaccumulation and transfer to humans through the food chain
The individual sediment samples pre-sieved at 5 mm and mechanically homogenized were divided into 120–140 g aliquots and further sieved at 2 mm to obtain two fractions each: sieve fraction 1, containing plastic fragments with size between 5 and 2 mm, and fraction 2, containing all microplastics smaller than 2 mm
The fraction 2 obtained from another equivalent aliquot of each sample was subjected to sequential extractions in refluxing organic solvents followed by alkaline hydrolysis as previously described [23], for separate quantitative determination of the extractable hydrocarbon polymers, and of the terephthalic acid (TPA) monomer deriving from the hydrolytic depolymerization of polyethylene terephthalate (PET)
Summary
Environmental pollution by microplastics (MPs) and nanoplastics (NPs) has raised growing concerns in the last two decades, as a result of the increasing evidences regarding the direct and indirect negative effects of such contaminants on both marine [1] and soil biota [2,3], and the potential of bioaccumulation and transfer to humans through the food chain. The growing number of studies about microplastic pollution in aquatic environments, initially focused on the detection and mapping of floating plastic debris, has expanded more recently to the investigation of those present in sediments [7]. Specific studies on the source of pollution by plastic materials in marine environments have estimated that about 80% of the total mass of plastic waste is originated in urban areas and conveyed to the seas mainly by rivers [16,17,18]. The results would allow drawing a more accurate picture of the source, extent, and transport of the different kind of microplastics, providing the basis for a correlation with the available data on the distribution of the different polymer types in marine environments on a global scale
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