Characterization and distribution of plastic particles along Alexandria beaches, Mediterranean Coast of Egypt, using microscopy and thermal analysis techniques

Biodegradation of low-density polyethylene LDPE by marine bacterial strains Gordonia alkanivorans PBM1 and PSW1 isolated from Mediterranean Sea, Alexandria, Egypt

Plastic has become an essential part of daily human activity. Nonetheless, its over-utilization has resulted in environmental accumulation, leading to marine contamination. Biodegradation is the most effective approach for managing synthetic plastic waste. It encompasses various biological processes that depolymerize polymeric compounds into oligomers or monomers that can enter the biogeochemical cycle. Although research on microplastic biodegradation is abundant and increasing, studies on the biodegradation of low-density polyethylene (LDPE) by marine microorganisms remain scarce and underexplored. In the present study, a total of 17 bacterial isolates were isolated from plastic-contaminated sites in Abu Qir Bay, Alexandria, Egypt. Two bacterial strains demonstrated the highest LDPE biodegradation potential and were identified using 16 S rRNA sequencing, exhibiting 100% and 99.87% sequence identity to Gordonia alkanivorans. Biodegradation of LDPE was confirmed through dry weight loss, with G. alkanivorans strains PSW1 and PBM1 achieving reductions of 0.88 ± 0.658% and 0.66 ± 0.508%, respectively. Biodegradation was further confirmed through the formation of cracks and cavities observed through scanning electron microscopy (SEM). Infrared analysis indicated significant changes in LDPE functional groups and a decrease in the carbonyl index. Biodegradation of LDPE films was also demonstrated through gas chromatography-mass spectrometry (GC/MS) via the release of metabolites, correlating with LDPE utilization. The findings highlight the ability of marine bacteria G. alkanivorans strains PSW1 and PBM1 to biodegrade LDPE.

Enhanced Bioadhesive and Antimicrobial Properties of PVA/Ascorbic Acid Composite with Tannic Acid Synthesized by Gamma Irradiation for Biomedical Applications

Bioadhesive hydrogels play a crucial role in biomedical applications due to their capacity to adhere to biological surfaces. This study investigates a novel bioadhesive hydrogel system developed from poly(vinyl alcohol) (PVA) and ascorbic acid (AS), cross-linked through gamma irradiation at 7 kGy, and modified with 5 wt % tannic acid (TA). The primary objective was to enhance the hydrogel's bioadhesive, mechanical, and antimicrobial properties. Mechanical testing revealed that the (PVA/AS)/TA hydrogel exhibited significant improvements, with a lap shear strength of 92 kPa, a tensile strength of 0.57 MPa, and an elongation at break of 180%, compared to the unmodified variant. Antimicrobial efficacy was assessed against bacterial strains, including Staphylococcus aureus and Escherichia coli, showing potent inhibitory effects with minimum inhibitory concentration (MIC) values of 25 μg/mL and 30 μg/mL, respectively. The findings indicate that the (PVA/AS)/TA hydrogel is a promising candidate for wound healing, drug delivery, and tissue engineering applications. It showcases its novelty in improving bioadhesive properties while providing antimicrobial functionality, thus addressing critical challenges in biomedical material design.

Assessing microplastic pollution vulnerability in a protected coastal lagoon in the Mediterranean Coast of Egypt using GIS modeling

Lake Burullus is a coastal wetland and protected area on the Mediterranean coast of Egypt. Despite the importance of this lake to the livelihood of millions of Egyptians, intensive anthropogenic activities and drainage water input have impacted its water quality. The current work aimed to evaluate the distribution and composition of microplastics (MPs) in Lake Burullus and analyze the impact of non-point pollution sources on their distribution and fate. The results showed that the average concentration of MPs in the open water was significantly lower (165.0 MPs/m3) than that near the drains (835.6 MPs/m3). The thermal analysis indicated the presence of eight thermoplastic polymers, originating from diffuse sources mainly via land-based activities. Moreover, a model was generated using ArcGIS 10.5 to assess the vulnerability of surface water to pollution from non-point sources. This model incorporated factors such as proximity to roads, waterways, land use, and urban areas, in addition to salinity and total suspended solids (TSS). Comprehensive maps were generated to visually illustrate the areas expected to be affected by MPs pollution. The results showed that waterways played an important role in in the transport of MPs to Lake Burullus. In addition, urban areas were identified as pollution hotspots, indicating the impact of land-use changes in urban areas. Salinity and TSS were also identified as important factors affecting the fate of MPs. Implementing strong measures to control land pollution in urban areas and managing wastewater inputs is highly recommended to effectively mitigate the impact of MPs on the ecosystem of Lake Burullus.

Assessment of persistent and emerging pollutants levels in marine bivalves in the Gulf of Suez, Egypt

Bivalves possess important ecological and economic values. They have been extensively used as bioindicators for both emerging and classical pollutants in the aquatic environment. This study investigates the levels of trace metals, polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs), alongside microplastic (MPs), in Tridacna maxima, Paphia textile, and Paratapes undulatus, collected from the Gulf of Suez. This work represents the first investigation of MPs in marine bivalves from the Gulf of Suez. MPs were detected in 72% of the specimens examined and four types of MPs were identified. The metal pollution index indicated that bivalves may have long-term toxic effects on human consumers. The results showed minimal hydrocarbon pollution. Diagnostic ratios indicated a combination of pyrolytic and petrogenic sources, with a notable influence from pyrolytic origins. The risk assessment reflected that the levels of certain trace metals, PAHs, and OCP contaminants could present a low risk to human health.

Sustainable polymeric adsorbents for adsorption-based water remediation and pathogen deactivation: a review

Water is a fundamental resource, yet various contaminants increasingly threaten its quality, necessitating effective remediation strategies. Sustainable polymeric adsorbents have emerged as promising materials in adsorption-based water remediation technologies, particularly for the removal of contaminants and deactivation of water-borne pathogens. Pathogenetic water contamination, which involves the presence of harmful bacteria, viruses, and other microorganisms, poses a significant threat to public health. This review aims to analyze the unique properties of various polymeric materials, including porous aromatic frameworks, biopolymers, and molecularly imprinted polymers, and their effectiveness in water remediation applications. Key findings reveal that these adsorbents demonstrate high surface areas, tunable surface chemistries, and mechanical stability, which enhance their performance in removing contaminants such as heavy metals, organic pollutants, and emerging contaminants from water sources. Furthermore, the review identifies gaps in current research and suggests future directions, including developing multifunctional polymeric materials and integrating adsorption techniques with advanced remediation technologies. This comprehensive analysis aims to contribute to advancing next-generation water purification technologies, ensuring access to clean and safe water for future generations.

Radiation synthesis of sodium alginate/gelatin based ultra-absorbent hydrogel for efficient water and nitrogen management in wheat under drought stress

The main focus of this study was on using radiation to make an ultra-absorbent hydrogel (UAH) from sodium alginate (SA) and gelatin (GL) biopolymers. This UAH can effectively handle water and nitrogen in wheat farming during drought stress. The hydrogel was synthesized by gamma irradiation-induced SA/GL/polyacrylamide crosslinking at 10-40 kGy. Varying SA/GL ratios affected swelling and the gel fraction of SA/GL/PAm hydrogels. The (SA/GL 17/83) hydrogel exhibited a 40.03 g/g swelling degree, while increasing SA content resulted in higher swelling, peaking at 75.5 g/g for (SA/GL 83/17). This indicated a synergistic interaction between SA and GL. The gel fraction also increased from 76.8 to 90.3%, with a higher GL content reflecting increased crosslinking. After multiple hydrolysis cycles, the hydrogel achieved 1293 (g/g) swelling and 36 days of water retention. When applied to wheat (Triticuma estivum) under drought stress, it significantly improved shoot length (18%), root length (43%), shoot fresh weight (49%), and shoot dry weight (51%) under extreme drought. The significant increases in protein and carbohydrate content in both shoots (up to 32% and 19%, respectively) and grains (up to 21% and 24%, respectively), along with the reduction in proline content (up to 38%), demonstrate that ultra-absorbent hydrogel (UAH) effectively enhances nitrogen content, photosynthesis, and overall plant health in wheat under varying drought stress levels. This novel SA/GL-based UAH holds promise for addressing water scarcity and agricultural challenges, offering a sustainable solution for water and nitrogen management under drought stress.

Microplastics in marine invertebrates from the Red Sea Coast of Egypt: Abundance, composition, and risks

This study marked the first exploration of microplastics in marine invertebrates in the Red Sea Coast of Egypt. 110 individuals from 11 different species, including Bivalvia, Gastropoda, Echinoidea, and Holothuroidrea, were collected near a popular tourist destination. The average concentrations of microplastics varied among species, ranging from 8.2 to 136.5 items per individual or 0.2 to 18.1 items per gram of tissue wet weight, with 100 % occurrence. Bivalves had higher concentrations per gram of tissue compared to sediment dwellers and grazers, with Brachidontes pharaonis showing the highest levels. Actinopyga crassa, a sea cucumber, displayed the highest abundance per individual due to its large size and behavior. The identified plastic polymers suggested sources associated with tourism and maritime activities. The estimated human exposure to microplastics through bivalve consumption was minimal. Further research is needed to examine microplastics contamination in the Red Sea and its potential impacts on ecosystems and human well-being.

Quantifying microplastics pollution in the Red Sea and Gulfs of Suez and Aqaba: Insights from chemical analysis and pollution load assessment

Microplastics (MPs) constitute the majority of marine plastic litter. The pollution caused by MPs has been categorized as a gradual and persistent crisis, but little is known about its extent along the shores of the Red Sea, particularly on the Egyptian side. The Red Sea is a rapidly developing region and home to critical ecosystems with high levels of endemism. This study represents the first comprehensive survey investigating the extent of MP pollution along the Egyptian shores of the Red Sea, including the Gulf of Suez and Aqaba. Mean concentrations ranged from 23.3 ± 15.28 to 930.0 ± 181.9 MPs/kg DW. Out of 17 beaches surveyed, 12 had mean concentrations of <200 items/kg, indicating a low occurrence of MPs compared to the shores of the Mediterranean Coast of Egypt. The pollution load index varied from low to medium levels in most locations. Ras Mohamed, a marine protected area, showed high vulnerability to MP pollution. All the investigated particles were fragments of secondary MPs. The sources of pollution mainly come from maritime activities, including cargo shipping and intense recreational activities. Fourier Transform Infrared Spectroscopy identified four plastic polymers, with polyethylene and polypropylene being the most common. The surface morphology of plastic particles was examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. All the particles exhibited signs of degradation, which could generate countless plastic pieces with possible deleterious impacts. This work has highlighted the importance of conducting region-specific assessments of mismanaged plastic waste, focusing on the role of tourism and recreational navigation as contributors to plastic litter, to estimate plastic waste inputs into the waters of the Red Sea Coast of Egypt. Efforts are needed to develop strategic plans to reduce the disposal of plastic waste in the region.

Distribution, bioavailability, and ecological risk assessment of potentially toxic heavy metals in El-Burullus Lake sediments, Egypt

El-Burullus Lake is the second largest coastal lagoon in Egypt in addition to its connection to the Mediterranean Sea. In this study, geochemical fractionations of heavy metals (Fe, Pb, Cd, Cu, Cr and Zn) were investigated after the great efforts made to rehabilitate and restore the lake by the Egyptian Government. The results indicated that F4 (residual fraction) was the dominant fraction for all studied metals followed by F3 (oxidizable fraction). That means the majority of studied metals source in the lake is lithogenic. Contamination by each individual heavy metal or multi elements was low according to individual contamination factor (ICF) and global contamination factor (GCF). Risk assessment code (RAC) classification showed that Cd and Cu exhibited low risk, Zn was of moderate risk, whereas, other metals are safe. The toxicity calculated by toxic risk index (TRI) indicating that no toxic risk was expected in the Lake.

Microplastics contamination in commercial fish from Alexandria City, the Mediterranean Coast of Egypt

Plastic waste is a major threat to various marine ecosystems. Due to being semi-enclosed basin with dense population, the Mediterranean Sea has been considered as a hot spot for plastic pollution. Alexandria was listed as one of the major cities contributing to plastic waste in the eastern Mediterranean basin. Accordingly, microplastics (MPs) abundance and composition were investigated in the digestive tracts of commercial fish species from two major fishing areas in Alexandria; Abu-Qir Bay and Eastern Harbor, which are affected by plastic pollution. The incidence and average densities of MPs were 91.8 ± 8.4% and 11.7 ± 9.5 items fish^-1, similar to highly polluted regions in the southeastern Mediterranean Sea. The average MPs concentration was significantly higher in Sparus aurata (38.3 ± 28.4 items fish^-1) than all species, except for Siganus rivulatus and Boops boops. Polyethylene and poly ethylene-vinyl acetate were the dominant polymers in the fish digestive tracts. Four types of plastic polymers were recorded in Siganus rivulatus and five in Parupeneus macronemus. The dominance of glossy fragments (sizes <500 μm) in Abu-Qir Bay indicated land-based source of pollution from domestic, agricultural, and industrial wastes. The dominance of larger plastic filaments and colored fragments in the Eastern Harbor suggested secondary MPs, originating from the fragmentation of larger plastic items of sea-based sources, such as fishing and recreational activities.