Influence of UV exposure time and simulated marine environment on different microplastic degradation.

This study investigated the influence of environmental factors (UV radiation and salinity) in the degradative process of microplastics (MPs). MPs derived from polypropylene (PP), polystyrene (PS), and ethylene-vinyl acetate (EVA) were subjected to accelerated photodegradation while being submerged in distilled water or artificial seawater. Depending on the polymer, changes in surface properties, new functional chemical group formation and oxidative index, and thermal characteristics of samples were observed. After photodegradation experiments, EVA-MPs samples showed an increase in their thermal resistance, besides the changes in their surface. PP-MPs crystallinity index increased upon exposure to UV radiation. PS samples showed a higher carbonyl and hydroxyl index after 30 h of UV exposure. The methodology exploited applies to any location in the world and can be comparable once considering the total ultraviolet index (UVI). The saline medium increases the crystallinity index of PP and EVA-MPs samples and intensifies the formation of new carbonyl and hydroxyl bonds in EVA-MPs samples. The results showed that several environmental factors should be considered in interpreting MPs photodegradation.

Self-supported 3D reduced graphene oxide for solid-phase extraction: An efficient and low-cost sorbent for environmental contaminants in aqueous solution.

A 3D reduced graphene oxide (3D-rGO), a self-supported, efficient, and low-cost sorbent, was synthesised and employed in a solid-phase extraction (SPE) cartridge. As a proof of concept, it was applied to remove diclofenac from aqueous solution. After applying statistical methods to systematically investigate key parameters for optimizing the 3D-rGO cartridge performance, it reached removal and elution efficiencies of 100 % and 90 %, respectively. This SPE cartridge presented advantages compared to traditional ones as the smaller amount of material into the cartridge (mass twenty times smaller), in addition to the ability of eliminating sorbent preconditioning, reducing the use of solvents, and making the process environmentally friendly with a faster operation. Also, it presented improved reproducibility after several cycles of reuse, and finally a lower cost of production unveiled by a cost-benefit analysis. Analysis with scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, Raman, and Fourier transform infrared spectroscopy in attenuated total reflectance mode suggested that the 3D framework morphology with a high content of carbon at the surface and some residual oxygen-containing groups are the protagonists in this performance. Therefore, 3D-rGO has the potential to be a highly efficient sorbent in analytical procedures using SPE for environmental contaminants in water and effluent samples.

Sorption of endocrine disrupting compounds onto polyamide microplastics under different environmental conditions: Behaviour and mechanism.

Microplastics of polyamide are commonly found in aquatic environments and might act as vectors of different contaminants such as endocrine disrupting compounds (EDC). Therefore, sorption of 17α-ethynylestradiol (EE2), 17ß-estradiol (E2), and estriol (E3) on polyamide microplastics was studied under different simulated environments. The results suggest that the sorption process was affected by the presence of dissolved organic matter (DOM) and salinity, where both positive and negative effects were observed. Kinetics revealed that the process occurs through multiple steps wherever the sorption rate depicting the transportation of EDC molecules from the liquid phase to the solid boundary of the sorbent, is higher than the intraparticle and pore diffusion process. In addition, the sorption rate of E2 decreased with the increase of water matrix complexity from ultrapure water (UPW) > artificial seawater (ASW) > fulvic acid water (FAW) > artificial seawater with fulvic acid (AS/FAW), while the sorption rate of EE2 decreased from UPW > ASW > FAW and increased in the matrix combining salinity and organic matter (AS/FAW). On the contrary, the E3 sorption rate increased with matrix complexity, from UPW < ASW < FAW and decreased with the influence of salinity and organic matter combination (AS/FAW). The sorption capacity of the EDC reached maximum values of 82% for E2, 90% for EE2 and 56% for E3. Isotherms demonstrated the occurrence of multilayer sorption. A positive relationship has been found between the hydrophobicity of polyamide microplastics and the Log Kow of EDC, showing an important role of hydrophobic interactions in the sorption process under all the studied conditions. Moreover, hydrogen bonding and binding of contaminants and DOM to microplastics through bridges were also suggested. The results show that salinity and DOM can greatly influence the sorption and transportation of EDC in the aquatic environment and pose a risk to aquatic ecosystems.

ZnO nanoparticles alter redox metabolism of Limnoperna fortunei.

Nanoparticles such as zinc oxide nanoparticles (ZnO-NP) that are incorporated in consumer and industrial products have caused concern about their potential ecotoxicological impact when released into the environment. Bivalve mollusks are susceptible targets for nanoparticle toxicity since nanomaterials can enter the cells by endocytosis mechanisms. The aim of this study was to evaluate the influence of ZnO-NP on the redox metabolism in Limnoperna fortunei and the DNA damage after exposure to ZnO-NP. Adult bivalves were incubated with 1-, 10-, and 50-µg mL-1 ZnO-NP for 2, 4, and 24 h. Ionic Zn release, enzymatic and non-enzymatic antioxidant activity, oxidative damage, and DNA damage were evaluated. Oxidative damage to proteins and lipids were observed after 4-h exposure and returned to baseline levels after 24 h. Superoxide dismutase levels decreased after 4-h exposure and increased after 24 h. No significant alteration was observed in the catalase activity or even DNA double-strand cleavage. The dissociation of ZnO may occur after 24 h, releasing ionic zinc (Zn2+) by hydrolysis, which was confirmed by the increase in the ionic Zn concentration following 24-h exposure. In conclusion, ZnO-NP were able to induce oxidative stress in exposed golden mussels. The golden mussel can modulate its own antioxidant defenses in response to oxidative stress and seems to be able to hydrolyze the nanoparticles and consequently, release Zn2+ into the cellular compartment.

Antioxidant defences and haemocyte internalization in Limnoperna fortunei exposed to TiO2 nanoparticles.

TiO2 nanoparticles (TiO2-NP) have been incorporated into a large range of materials for different applications in the last decades and are very likely to appear in wastewater and effluents, eventually reaching the aquatic environment. Therefore, the assessment of the biological impact of TiO2-NP on aquatic ecosystem is of a major concern. The mussels represent a target group for TiO2-NP toxicity, as they are filter feeders and are capable of bioaccumulating toxic compounds. Furthermore, the exotic organism Limnoperna fortunei, golden mussel, is a freshwater bivalve that has been used in biomonitoring environmental conditions. In this work, the TiO2-NP's ability to interact with haemocytes of golden mussel was assessed by transmission electron microscopy. The enzymatic and non-enzymatic antioxidant defenses were evaluated by superoxide dismutase (Sod) and catalase (Cat) activities and protein sulfhydryl content, which were measured after the golden mussel was exposed to TiO2-NP (1, 5, 10 and 50µgmL(-1)). Results demonstrate that TiO2-NP was internalized by cells, causing alterations in haemocytes membrane. Antioxidant activity of Sod and Cat decreased after 2h TiO2-NP exposure. After 4h exposure, the enzymatic antioxidant activity was restored. Notably, the protein sulfhydryl content decreased after 2h to all the TiO2-NP concentrations and no alterations were observed after 4h of TiO2-NP exposure. These results demonstrate the potential of golden mussel as sentinel organism to TiO2-NP exposure.

Determination of monoaromatic hydrocarbons (BTEX) in surface waters from a Brazilian subtropical hydrographic basin.

This study examined surface water samples for the presence of the monoaromatic hydrocarbons benzene, toluene, ethylbenzene and xylene. Water samples were collected from the sub-basin of the Tegas River and the Marrecas Stream microbasin located in the metropolitan region of the municipality of Caxias do Sul (Rio Grande do Sul State, Brazil). For all sampling points evaluated, only toluene was detected, with concentrations values in the range of 1.70-18.44 µg L(-1). In general, the relatively high toluene concentration for the samples collected were above the limit of 2 µg L(-1) established by the Brazilian government for Class I rivers for the protection of aquatic life. However, they were well below the established limit of 170 µg L(-1) in water used for human consumption.