PET plastics as a Trojan horse for radionuclides

Elemental analysis by neutron activation analysis and synchrotron x-ray fluorescence microscopy of ocean plastics ingested by pelagic seabirds

We report the combined use of Neutron Activation Analysis (NAA) for bulk measurement of marine plastics ingested by wildlife, with a more detailed analysis of individual plastics at different stages of degradation using synchrotron X-ray fluorescence microscopy (S-XFM). On average, Sable Shearwaters (n = 9) ingested 4.16 ± 4.62 g of plastics (50 ± 35 items), most of which were high-density polyethylene (47.4 %) and polypropylene (42.6 %) as determined by attenuated total reflectance Fourier transform infrared spectroscopy. Using NAA, the most abundant elements (Ti, Zn, Cd, Cu, Cr, Sr) were those commonly associated with plastic additives that confer UVC resistance, mechanical properties, or colouration. S-XFM revealed that visually and structurally near identical plastics may not only contain different chemical elements, but that the internal spatial distribution of these elements can vary substantially. S-XFM also detected the presence of lead (Pb) which may indicate prior recycling history of the plastic feed stock. A consistent finding was the accumulation of iron (Fe) and bromine (Br) at the surface of the degrading plastics, attributable to biofilm formation. Our observations highlight that bird populations ingesting marine plastics are exposed to an unpredictable profile of chemical elements, the degradation-dependent release rate of which is unknown in the acidic and enzymatically-active stomach environment. Based on the variability of their elemental content, we propose to regard marine plastics as 'mixed waste'. We speculate that plastics more generally could be doped with complex elemental 'fingerprints' for the purpose of traceability and establishment of an unbroken chain of custody.

Floating microplastics along the western Mediterranean Sea: Are we reaching a "Good Environmental Status" or drifting away?

This study investigates the spatial and temporal distribution of sea surface microplastic in the Spanish Mediterranean Sea, assessing compliance with the Good Environmental Status (GES) criteria of the European Marine Strategy Framework Directive 2008/56/EC and Barcelona Convention. Data from 668 sea surface water samples collected from 2017 to 2023 were analysed to classify their status according to indicators of microplastic pollution. A mean abundance of 0.24 ± 1.80 items/m2 of sea surface microplastics was quantified, with significant differences between locations, zones, areas, and macro-areas (KW, p <0.05). The highest abundance was observed in the protected area of the Columbretes Islands (14.26 ± 8.66 items/m2) and the lowest in Fuengirola (0.0008 ± ND items/m2). The peninsular coast showed a higher abundance of microplastic (0.41 ± 0.27 items/m2) than the Balearic Islands (0.21 ± 0.06 items/m2). Fragments and sheets accounted for 72 % and 15 % of the microplastics, respectively. The highest microplastic abundance was observed in 2017 (0.85 ± 0.5 items/m2) and the lowest in 2022 (0.07 ± 0.01 items/m2), but no temporal trend was detected (MK, p >0.05). According to GES, 98 % of the stations were classified as having "Moderate" to "Very poor" conditions, while only 2 % were in good or high environmental status. This study confirms the lack of GES achievement along the Spanish western Mediterranean coastal waters and highlights the need for action to reduce plastic waste and prevent marine pollution.

The microplastic-crisis: Role of bacteria in fighting microplastic-effects in the digestive system

Plastic particles smaller than 5 mm, referred to as Microplastics, pose health risks, like metabolic, immunological, neurological, reproductive, and carcinogenic effects, after being ingested. Smaller plastic particles are more likely to be absorbed by human cells, with nanoplastics showing higher potential for cellular damage, including DNA fragmentation and altered protein functions. Micro- and nanoplastics (MNPs) affect the gastrointestinal tract by altering the microbial composition, they could influence digestive enzymes, and possibly disrupt mucus layers. In the stomach, they potentially interfere with digestion and barrier functions, while in the intestines, they could increase permeability via inflammation and tissue disruption. MNPs can lead to microbial dysbiosis, leading to gastrointestinal symptoms. By activating inflammatory pathways, altering T cell functions and affecting dendritic cells and macrophages, immune system homeostasis could possibly be disrupted. Probiotics offer potential strategies to alleviate plastic effects, by either degrading plastic particles or directly countering health effects. We compared genetic sequences of probiotics to the genome of known plastic degraders and concluded that no probiotic bacteria could serve the role of plastic degradation. However, probiotics could directly mitigate MNP-health effects. They can restore microbial diversity, enhance the gut barrier, regulate bile acid metabolism, reduce inflammation, regulate insulin balance, and counteract metabolic disruptions. Antioxidative properties protect against lipid peroxidation and MNP-related reproductive system damage. Probiotics can also bind and degrade toxins, like heavy metals and bisphenol A. Additionally, bacteria could be used to aggregate MNPs and reduce their impact. Therefore, probiotics offer a variety of strategies to counter MNP-induced health effects.

Polyethylene terephthalate (PET) microplastics as radionuclide (U-232) carriers: Surface alteration matters the most

Polyethylene terephthalate (PET) plastics find widespread use in various aspects of our daily lives but often end up in the environment as (micro)plastic waste. In this study, the adsorption efficiency of PET microplastics for U-232 has been investigated prior and after surface alteration (e.g. oxidation (PET-ox), MnO2-coating (PET/MnO2) and biofilm-formation (PET/Biofilm)) in the laboratory (at pH 4, 7 and 9) and seawater samples under ambient conditions and as a function of temperature. The results revealed a significant increase in the adsorption efficiency upon surface alteration, particularly after biofilm development on the MP's surface. Specifically, the Kd values evaluated for the adsorption of U-232 by PET, PET-ox, PET/MnO2 and PET/Biofilm are 12, 27, 73 and 363, respectively, at pH 7 and under ambient conditions. The significantly higher adsorption efficiency of the altered and particularly biofilm-coated PET, emphasizes the significance of surface alteration, which may occur under environmental conditions. In addition, according to the thermodynamic investigations the adsorption of U-232 by PET-MPs (both non-treated and modified), the adsorption is an endothermic and entropy-driven reaction. A similar behavior has been also observed using seawater solutions and assumes that surface alteration is expected to enhance the radionuclide, stability, mobility and bioavailability in environmental water systems.

Economic losses related to the reduction of Posidonia ecosystem services in the Gulf of Gabes (Southern Mediterranean Sea)

In the early XXth century, the Gulf of Gabes in SE Tunisia used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean basin and was a highly productive hotspot of benthic species. Since the 70's, >500 million t of wet toxic phosphogypsum discharges from a fertilizer industrial complex have led to the gradual loss of ∼90 % of its initial surface. This drastic shrinkage is accompanied by significant value losses originated from the direct and indirect-use services of which the most important ones are small scale fisheries and carbon storage function. Using market valuations of a number of services we estimate economic losses at 105 million € in 2014 (∼915€/ha), i.e., around 115 % of the added value of the gabesian fertilizer factories for the same year. Value losses should increase in the near future in relation with the COP26 agreements which boosted the open carbon credit market. Without actions to reduce negative production externalities caused by the fertilizer industry in the Gulf of Gabes it would not be possible to recover Posidonia ecosystems in this region leading to further economic, ecologic, and cultural losses.