Types, occurrence, and distribution of microplastics and metals contamination in sediments from south west of Kerkennah archipelago, Tunisia

Differentiating Microplastics from Natural Particles in Aqueous Suspensions Using Flow Cytometry with Machine Learning

Microplastics (MPs) in natural waters are heterogeneously mixed with other natural particles including algal cells and suspended sediments. An easy-to-use and rapid method for directly measuring and distinguishing MPs from other naturally present colloids in the environment would expedite analytical workflows. Here, we established a database of MP scattering and fluorescence properties, either alone or in mixtures with natural particles, by stain-free flow cytometry. The resulting high-dimensional data were analyzed using machine learning approaches, either unsupervised (e.g., viSNE) or supervised (e.g., random forest algorithms). We assessed our approach in identifying and quantifying model MPs of diverse sizes, morphologies, and polymer compositions in various suspensions including phototrophic microorganisms, suspended biofilms, mineral particles, and sediment. We could precisely quantify MPs in microbial phototrophs and natural sediments with high organic carbon by both machine learning models (identification accuracies over 93%), although it was not possible to distinguish between different MP sizes or polymer compositions. By testing the resulting method in environmental samples through spiking MPs into freshwater samples, we further highlight the applicability of the method to be used as a rapid screening tool for MPs. Collectively, this workflow can be easily applied to a diverse set of samples to assess the presence of MPs in a time-efficient manner.

Occurrence and risks of microplastics in the ecosystems of the Middle East and North Africa (MENA)

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m³ and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Erⁱ > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries.

Joint effects of microplastics and ZnO nanoparticles on the life history parameters of rotifers and the ability of rotifers to eliminate harmful phaeocystis

The rising concentration of microplastics and nanoparticles coexisting simultaneously in marine may bring joint harm to zooplankton. Rotifer is an important functional group of marine zooplankton, which plays an important role in the energy flow of marine ecosystem. To evaluate the comprehensive effects of nano-sized microplastics and metal oxide nanoparticles on life history parameters of rotifers and population dynamics of rotifers during eliminating harmful algae Phaeocystis, we exposed rotifers Brachionus plicatilis to the multiple combinations of different concentrations of nanoplastics and ZnO nanoparticles. Results showed that rotifer maturation time was prolonged and the total offspring was decreased significantly with rising ZnO nanoparticles and microplastics concentrations, and microplastics and ZnO nanoparticles had significant interaction, which brought more serious joint deleterious effects on survival, development, and reproduction. At the population level, ZnO nanoparticles exacerbated the delayed effect of microplastics on the elimination of Phaeocystis by rotifers, although eventually rotifers also completely eliminated Phaeocystis in the closed system. This study provided new insights into revealing the comprehensive impact of microplastics and ZnO nanoparticles on zooplankton not only from the perspective of life history parameters of rotifers but also from the perspective of population dynamics of rotifers controlling harmful algae, which is of great significance to understand the impact of mixed pollutants on marine ecosystem.

The response of life history defense of cladocerans under predation risk varies with the size and concentration of microplastics

Microplastics are an emerging and increasingly serious pollutant in freshwater environment, which have become a threat to freshwater organisms. However, whether microplastics interfere with the responses of organisms to their predators is still unclear. In this study, we investigated the effects of microplastics with tiny different particle size (diameter: 0.7 and 1 µm) on the anti-predation (Rhodeus ocellatus as the predator) defense responses of different body-sized cladocerans, Daphnia pulex and Moina macrocopa. Results showed that microplastics had a size-based inhibitory effect on the induced defense of both D. pulex and M. macrocopa. Specifically, 0.7 µm microplastics had stronger effects on reduced survival time, delayed maturation time, and decreased offspring numbers. In addition, the effects of microplastics also varied with different body-sized cladocerans, i.e. medium-sized cladoceran (D. pulex) were more sensitive than the small-sized one (M. macrocopa) regarding the maturation time. This study illustrated for the first time that the effect of microplastics on induced defense was related to cladoceran species and microplastics size, and further revealed the extensive negative effects of microplastics from the perspective of interspecific relationship.

Environmental Microplastic Particles vs. Engineered Plastic Microparticles-A Comparative Review

Microplastic particles (MPs) pose a novel threat to nature. Despite being first noticed in the 1970s, research on this topic has only surged in recent years. Researchers have mainly focused on environmental plastic particles; however, studies with defined microplastic particles as the sample input are scarce. Furthermore, comparison of those studies indicates a discrepancy between the particles found (e.g., in the environment) and those used for further research (e.g., exposure studies). Obviously, it is important to use particles that resemble those found in the environment to conduct appropriate research. In this review, different categories of microplastic particles are addressed, before covering an overview of the most common separation and analysis methods for environmental MPs is covered. After showing that the particles found in the environment are mostly irregular and polydisperse, while those used in studies with plastic microparticles as samples are often not, different particle production techniques are investigated and suggestions for preparing realistic plastic particles are given.

Removal of Pharmaceuticals from Water by Adsorption and Advanced Oxidation Processes: State of the Art and Trends

Pharmaceutical products have become a necessary part of life. Several studies have demonstrated that indirect exposure of humans to pharmaceuticals through the water could cause negative effects. Raw sewage and wastewater effluents are the major sources of pharmaceuticals found in surface waters and drinking water. Therefore, it is important to consider and characterize the efficiency of pharmaceutical removal during wastewater and drinking-water treatment processes. Various treatment options have been investigated for the removal/reduction of drugs (e.g., antibiotics, NSAIDs, analgesics) using conventional or biological treatments, such as activated sludge processes or bio-filtration, respectively. The efficiency of these processes ranges from 20–90%. Comparatively, advanced wastewater treatment processes, such as reverse osmosis, ozonation and advanced oxidation technologies, can achieve higher removal rates for drugs. Pharmaceuticals and their metabolites undergo natural attenuation by adsorption and solar oxidation. Therefore, pharmaceuticals in water sources even at trace concentrations would have undergone removal through biological processes and, if applicable, combined adsorption and photocatalytic degradation wastewater treatment processes. This review provides an overview of the conventional and advanced technologies for the removal of pharmaceutical compounds from water sources. It also sheds light on the key points behind adsorption and photocatalysis.

Plastic pollution threat in Africa: current status and implications for aquatic ecosystem health

Rapid population growth and poor waste management practice are among the main drivers of plastic pollution in modern times, thus making Africa a hotspot for plastic pollution both now and in the future. This study is a review of plastic pollution reports from the African aquatic environment with regard to causes, current status, toxicological implications and implications for ecosystem services. A total of 59 plastic pollution studies from 1987 to September 2020 were reviewed. They comprised 15 from North Africa (NA) (Algeria, Egypt, Morocco and Tunisia), six from East Africa (EA) (Ethiopia, Kenya, Tanzania and Uganda), 13 from West Africa (WA) (Ghana, Guinea-Bissau, Mauritania and Nigeria), and 25 studies from Southern Africa (SA) (South Africa). This shows that plastic pollution studies in Africa, according to the sub-regions, are in the order: SA > NA > WA > EA. High human population in the basins of African large aquatic systems is identified as the greatest driver enhancing plastic surge in the aquatic environment. The occurrence of plastics was mostly reported in the estuarine/marine environment (42 studies) compared to the freshwater environment (only 17 studies). Plastics have also been reported in the three compartments of the aquatic environment: water column, benthic sediment and animals. Zooplankton, annelids, molluscs, insects, fishes and birds were reported as bioindicators of plastic ingestion in the inland and coastal waters of Africa. Polyethylene, polyethylene terephthalate (polyester) and polypropylene were the common plastic polymers observed in the African aquatic environment. In situ toxicological implications of the ingested plastic polymers were not reported in any of the studies. However, reports from laboratory-controlled experiments showed that these polymers are deleterious to aquatic animal health. More research efforts need to delineate the plastic pollution status of the East, West and North of Africa. Furthermore, such studies are required to identify the plastic polymers and in situ ecotoxicological impacts of plastics on both animal and human health.

A Review of Zein as a Potential Biopolymer for Tissue Engineering and Nanotechnological Applications

Tissue engineering (TE) is one of the most challenging fields of research since it provides current alternative protocols and materials for the regeneration of damaged tissue. The success of TE has been mainly related to the right selection of nano-sized biocompatible materials for the development of matrixes, which can display excellent anatomical structure, functionality, mechanical properties, and histocompatibility. Today, the research community has paid particular attention to zein as a potential biomaterial for TE applications and nanotechnological approaches. Considering the properties of zein and the advances in the field, there is a need to reviewing the current state of the art of using this natural origin material for TE and nanotechnological applications. Therefore, the goal of this review paper is to elucidate the latest (over the last five years) applications and development works in the field, including TE, encapsulations of drugs, food, pesticides and bandaging for external wounds. In particular, attention has been focused on studies proving new breakthroughs and findings. Also, a complete background of zein’s properties and features are addressed.