Search Results (10)

Microplastics are omnipresent in aquatic environments and can act as vectors to carry other pollutants, modifying their pathway through the systems. In this study, the differences in the adsorption capacity and mechanism for Cr(VI) sorption with polyethylene (PE, a conventional microplastic) and polylactic acid (PLA, a biodegradable microplastic) were investigated via characterization of the MPs, the determination of kinetic behavior (pseudo-first- and second-order model, the Elovich model), and the degree of fit to Langmuir and Freundlich isothermal models; the adsorption behavior was also studied under different solution conditions. The results indicated that when the dose of MPs was 1 g/L, the adsorption capacity of Cr(VI) on MPs reached the highest value, the adsorption capacities were PLA(0.415 mg/g) > PE(0.345 mg/g). The adsorption of Cr(VI) on PE followed the Langmuir isotherm model, while PLA had a stronger fit with the Freundlich model. Sorption in both cases followed a pseudo-first-order kinetics model. The maximum adsorption capacity of Cr(VI) on PLA (0.54 mg/g) is higher than that on PE (0.38 mg/g). In addition, PLA could reach adsorption equilibrium in about 8 h and can adsorb 72.3% of the total Cr(VI) within 4 h, while PE required 16 h to reach equilibrium, suggesting that PLA adsorbs at a significantly faster rate than PE. Thus, biodegradable MPs like PLA may serve as a superior carrier for Cr(VI) in aquatic environments. When the pH increased from 2 to 6, the adsorption of Cr(VI) by PE and PLA decreased from 0.49 mg/g and 0.52 mg/g to 0.27 mg/g and 0.26 mg/g, respectively. When the concentration of sodium dodecyl sulfate in the Cr(VI) solution was increased from nil to 300 mg/L, the adsorption of Cr(VI) by PE and PLA increased by 3.66 and 3.05 times, respectively. In addition, a higher temperature and the presence of Cu²⁺ and photoaging promoted the adsorption of Cr(VI) by MPs, while higher salinity inhibited the adsorption. The desorption efficiencies of Cr(VI) on MPs were PLA(57.8%) > PE(46.4%). The characterization results further confirmed that the adsorption mechanism could be attributed to electrostatic attraction, hydrogen bonding, and surface complexation. In sum, PLA could potentially serve as better vectors for Cr(VI) than PE, but the risk associated with PLA might be higher than that with PE. Full article

Microplastics (MPs) and antibiotics are emerging pollutants widely found in aquatic environments, potentially causing environmental harm. MPs may act as carriers for antibiotics, affecting their environmental distribution. This study investigates the adsorption of four macrolide antibiotics and a metabolite onto two types of MPs: polyethylene terephthalate (PET) and polyethylene (PE). Results revealed a linear isotherm adsorption model, with higher adsorption to PET than to PE (R² > 0.936 for PE and R² > 0.910 for PET). Hydrophobic interactions and hydrogen bonding could be the main adsorption mechanisms, with pore filling potentially involved. Reduced particle size enhances adsorption due to the increase of active adsorption sites. This increasement is more pronounced in PE than in PET, leading to an 11.6% increase in the average adsorption of all macrolides to PE, compared to only 5.1% to PET. Dissolved organic matter inhibits adsorption (azithromycin adsorption to PE was reduced from 12% to 5.1%), while salinity enhances it just until 1% salinity. pH slightly influences adsorption, with maximal adsorption at neutral pH. Results in real samples showed that complexity of the matrix decreased adsorption. Overall, these findings indicate that PE and PET MPs can be a vector of macrolides in aquatic environments. Full article

Plastic pollution is a global diffuse threat, especially considering its fragmentation into microplastics (MPs) and nanoplastics (NPs). Since the contamination of the aquatic environment is already well studied, most studies have now focused on the soil. Moreover, the number of studies on the exposure routes and toxic effects of MNPs in humans is continuously increasing. Although MNPs can cause inflammation, cytotoxicity, genotoxicity and immune toxicity in livestock animals, which can accumulate ingested/inhaled plastic particles and transfer them to humans through the food chain, research on this topic is still lacking. In considering farm animals as the missing link between soil/plant contamination and human health effects, this paper aims to describe their importance as carriers and vectors of MNP contamination. As research on this topic is in its early stages, there is no standard method to quantify the amount and the characteristics of MNPs in different matrices. Therefore, the creation of a common database where researchers can report data on MNP characteristics and quantification methods could be helpful for both method standardization and the future training of an AI tool for predicting the most abundant/dangerous polymer(s), thus supporting policy decisions to reduce plastic pollution and perfectly fitting with One Health principles. Full article

Ballast water is recognized as a major vector for the transfer of Harmful Aquatic Organisms and Pathogens (HAOP) and a source of sea pollution that negatively affects the environment and human health. Therefore, the International Maritime Organization (IMO) adopted the International Convention for the Control and Management of Ship’s Ballast Water and Sediments (BWM Convention) in 2004. The BWM Convention introduced two standards, Ballast Water Exchange Standard (Regulation D-1) and Ballast Water Performance Standard (Regulation D-2). Ships are required to install Ballast Water Treatment (BWT) equipment in order to comply with Regulation D-2. However, the deadline for the installation of BWT is prolonged until September 2024, and many ships are still complying only with Regulation D-1. In addition, there are specific sea areas where Regulation D-1 cannot be complied with, and hence, HAOP could be easily transferred between ports. Consequently, it is essential to develop a system to protect the marine environment, human health and economy in coastal areas from the introduction of HAOP. This paper analyses ballast water discharged in the Port of Ploče (Croatia) according to ship type, age and flag they are flying. It was found that general cargo ships and bulk carriers discharged most of the ballast (87% of the total quantity) in the Port of Ploče. Moreover, discharged ballast water was analysed according to the origin, and it was found that 70% of discharged ballast originates from the Adriatic Sea. Based on the analysis of the research results and literature review, the ballast water risk assessment (BWRA) method was adopted, however, with certain modifications. The adopted method is modified by an additional risk factor (the deballasting ship’s age), different risk scoring of the deballasting ship type and adding Paris MoU Grey and Black lists flag ships as high-risk ships. As a result, the BWRA method presented in the paper could be used as an early warning system and to facilitate the implementation of adequate measures to prevent pollution by discharged ballast water. Full article

As landfilling is a common method for utilizing plastic waste at its end-of-life, it is important to present knowledge about the environmental and technical complications encountered during plastic disposal, and the formation and spread of microplastics (MPs) from landfills, to better understand the direct and indirect effects of MPs on pollution. Plastic waste around active and former landfills remains a source of MPs. The landfill output consists of leachate and gases created by combined biological, chemical, and physical processes. Thus, small particles and/or fibers, including MPs, are transported to the surroundings by air and by leachate. In this study, a special focus was given to the potential for the migration and release of toxic substances as the aging of plastic debris leads to the release of harmful volatile organic compounds via oxidative photodegradation. MPs are generally seen as the key vehicles and accumulators of non-biodegradable pollutants. Because of their small size, MPs are quickly transported over long distances throughout their surroundings. With large specific surface areas, they have the ability to absorb pollutants, and plastic monomers and additives can be leached out of MPs; thus, they can act as both vectors and carriers of pollutants in the environment. Full article

Plastics have been one of the most useful materials in the world, due to their distinguishing characteristics: light weight, strength, flexibility, and good durability. In recent years, the growing consumption of plastics in industries and domestic applications has revealed a serious problem in plastic waste treatments. Pollution by microplastics has been recognized as a serious threat since it may contaminate all ecosystems, including oceans, terrestrial compartments, and the atmosphere. This micropollutant is spread in all types of environments and is serving as a “minor but efficient” vector for carrier contaminants such as pesticides, pharmaceuticals, metals, polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The need to deeply study and update the evolution of microplastic sources, toxicology, extraction and analysis, and behavior is imperative. This review presents an actual state of microplastics, addressing their presence in the environment, the toxicological effects and the need to understand their extent, their interactions with toxic pollutants, the problems that arise in the definition of analytical methods, and the possible alternatives of treatments. Full article

Filter feeders are target species for microplastic (MP) pollution, as particles can accumulate in the digestive system, disturbing feeding processes and becoming internalized in tissues. MPs may also carry pathogens or pollutants present in the environment. This work assessed the influence of polystyrene (PS) MP size and concentration on accumulation and depuration time and the role of MPs as vectors for metallic (Cd) and organic (benzo(a)pyrene, BaP) pollutants. One-day exposure to pristine MPs induced a concentration-dependent accumulation in the digestive gland (in the stomach and duct lumen), and after 3-day depuration, 45 µm MPs appeared between gill filaments, while 4.5 µm MPs also occurred within gill filaments. After 3-day exposure to contaminated 4.5 µm MPs, mussels showed increased BaP levels whilst Cd accumulation did not occur. Here, PS showed higher affinity to BaP than to Cd. Three-day exposure to pristine or contaminated MPs did not provoke significant alterations in antioxidant and peroxisomal enzyme activities in the gills and digestive gland nor in lysosomal membrane stability. Exposure to dissolved contaminants and to MP-BaP caused histological alterations in the digestive gland. In conclusion, these short-term studies suggest that MPs are ingested and internalized in a size-dependent manner and act as carriers of the persistent organic pollutant BaP. Full article

Three-phase four-leg voltage-source converters have been considered for some recent projects in smart grids and in the automotive industry, projects such as on-board electric vehicles (EVs) chargers, thanks to their built-in ability to handle unbalanced AC currents through the 4th wire (neutral). Although conventional carrier-based modulations (CBMs) and space vector modulations (SVMs) have been commonly applied and extensively studied for three-phase four-leg voltage-source converters, very little has been reported concerning their pollution impact on AC grid in terms of switching ripple currents. This paper introduces a thorough analytical derivation of peak-to-peak and RMS values of the AC current ripple under balanced and unbalanced working conditions, in the case of three-phase four-leg converters with uncoupled AC-link inductors. The proposed mathematical approach covers both phase and neutral currents. All analytical findings have been applied to two industry recognized CBM methods, namely sinusoidal pulse-width modulation (PWM) and centered PWM (equivalent to SVM). The derived equations are effective, simple, and ready-to-use for accurate AC current ripple calculations. At the same time, the proposed equations and diagrams can be successfully adopted to design the conversion system basing on the grid codes in terms of current ripple (or total harmonic distortion (THD)/total demand distortion (TDD)) restrictions, enabling the sizing of AC-link inductors and the determination of the proper switching frequency for the given operating conditions. The analytical developments have been thoroughly verified by numerical simulations in MATLAB/Simulink and by extensive experimental tests. Full article

The fate, properties and determination of microplastics (MPs) and nanoplastics (NPs) in soil are poorly known. In fact, most of the 300 million tons of plastics produced each year ends up in the environment and the soil acts as a log-term sink for these plastic debris. Therefore, the aim of this review is to discuss MP and NP pollution in soil as well as highlighting the knowledge gaps that are mainly related to the complexity of the soil ecosystem. The fate of MPs and NPs in soil is strongly determined by physical properties of plastics, whereas negligible effect is exerted by their chemical structures. The degradative processes of plastic, termed ageing, besides generating micro-and nano-size debris, can induce marked changes in their chemical and physical properties with relevant effects on their reactivity. Further, these processes could cause the release of toxic oligomeric and monomeric constituents from plastics, as well as toxic additives, which may enter in the food chain, representing a possible hazard to human health and potentially affecting the fauna and flora in the environment. In relation to their persistence in soil, the list of soil-inhabiting, plastic-eating bacteria, fungi and insect is increasing daily. One of the main ecological functions attributable to MPs is related to their function as vectors for microorganisms through the soil. However, the main ecological effect of NPs (limited to the fraction size < than 50 nm) is their capacity to pass through the membrane of both prokaryotic and eukaryotic cells. Soil biota, particularly earthworms and collembola, can be both MPs and NPs carriers through soil profile. The use of molecular techniques, especially omics approaches, can gain insights into the effects of MPs and NPs on composition and activity of microbial communities inhabiting the soil and into those living on MPs surface and in the gut of the soil plastic-ingesting fauna. Full article

The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative, hydrogen is widely regarded as a key element for a potential energy solution. However, different from fossil fuels such as oil, gas, and coal, the production of hydrogen requires energy. Alternative and intermittent renewable sources such as solar power, wind power, etc., present multiple advantages for the production of hydrogen. On one hand, the renewable sources contribute to a remarkable reduction of pollutants released to the air. On the other hand, they significantly enhance the sustainability of energy supply. In addition, the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of the renewable energy sources. In this regard, hydrogen storage technology presents a key roadblock towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen, solid-state storage is the most attractive alternative both from the safety and the volumetric energy density points of view. Because of their appealing hydrogen content, complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review, the progresses made over the last century on the development in the synthesis and research on the decomposition reactions of homoleptic tetrahydroborates is summarized. Furthermore, theoretical and experimental investigations on the thermodynamic and kinetic tuning of tetrahydroborates for hydrogen storage purposes are herein reviewed. Full article