Fabrication of environmentally safe antifouling coatings using nano-MnO2/cellulose nanofiber composite with BED/GMA irradiated by electron beam

Marine biofouling, undesirable growth of organisms on submerged surfaces, poses significant challenges in various industries and marine applications. The development of environmentally safe antifouling coatings employing nano-MnO2/cellulose nanofiber (CNF) composite with bisphenol A epoxy diacrylate/glycidyl methacrylate (BED/GMA) irradiated by electron beam (T1) has been achieved in the current work. The physico-chemical characteristics of the fabricated coatings have been studied using Fourier transforms infrared spectroscopy, scanning electron microscope, water contact angle, and X-ray diffraction. The efficacy of T1 formulation and pure BED/GMA polymer (T2) in inhibiting biofouling formation was investigated in seawater of Alexandria Eastern Harbour by examining biofilm development morphologically and biochemically. In addition, regular analyses of seawater physicochemical parameters were conducted monthly throughout study. Results provide valuable information on coating performance as well as the complex interactions between coatings, biofilms, and environmental factors. The T1 formulation exhibited strong anti-fouling and anticorrosion properties over 2 months. However, after four months of immersion, all coated steel surfaces, including T1, T2, and T0, were heavily covered with macro-fouling, including tubeworms, barnacles, and algae. Biochemical analysis of extracellular polymeric substances (EPS) showed statistically significant variations in carbohydrates content between the coated surfaces. The T1 formulation showed decreased protein and carbohydrate content in EPS fractions after 14 days of immersion indicating less biofouling. Moreover, elemental analysis showed that carbon, oxygen, and iron were the predominant elements in the biofilm. Other elements such as sodium, silicon, chloride, and calcium were in lower concentrations. T2 and T0 surfaces revealed higher calcium levels and the appearance of sulphur peaks if compared with T1 surface. Diatoms and bacteria were detected on T1, T2, and T0 surfaces. The observed warming of seawater and nutrient-rich conditions were found to promote the growth of fouling organisms, emphasizing the importance of considering environmental factors in biofouling management strategies.

Spatial distribution, sources and risk assessment of polycyclic aromatic hydrocarbons in the surficial sediments of the Egyptian Mediterranean coast

The Egyptian Mediterranean coast (EMC) receives a considerable quantity of polycyclic aromatic hydrocarbons (PAHs). PAHs from EMC sediments were assessed to understand the effects of marine and riverine currents on their distribution. The concentrations of total PAHs ranged between 13,156-34,852 ng/g dw. PAH levels have increased even in areas far from the shoreline under the influence of riverine inputs from the Nile River; this is attributed to the tidally induced riverine freshwater re-suspension of surface sediments in the shallow near-shore section and re-precipitation in the fare stations. PAH levels generally increase as one moves from the western to the eastern part of the studied area, owing to the effect of the marine current. Diagnostic ratios pointed toward different pyrogenic sources. SQGs were used to assess the probability of observing adverse biological effects in benthic organisms in sediment samples. The toxic and mutagenic equivalent quotient for carcinogenic PAHs was extremely high.

Horizontal and vertical segregation of polycyclic aromatic hydrocarbons in the Egyptian Mediterranean coast

Egyptian Mediterranean coast receives significant amounts of polycyclic aromatic hydrocarbons (PAHs) from industrial exhausts, riverine inputs, maritime shipping and fishers, and oil and natural gas production and exploration. The present study considers the first exhaustive assessment for the dissolved PAHs along the Egyptian Mediterranean coast (Alexandria to Manzallah) to monitor their spatial distribution and investigate the effect of the marine currents and the role of microorganisms in their distribution. Surface water levels ranged between 124.97 and 301.02 ng L^-1 with an average 223.68 ± 41.11 ng L^-1. The distribution increases from west to east based on the water circulation in the Mediterranean Sea. The levels in near shore stations were lower than those of middle and onshore stations. The intensive existence of micro-organisms near shore stations consumes great part of PAHs, while this bio-remediation process decreases gradually away from the shoreline leaving relative high concentrations of dissolved PAHs in the middle and onshore stations. Middle and deep-water levels ranged between 312.75 and 1042.95 ng L^-1 with an average 633.47 ± 225.53 ng L^-1. Deeper waters showed higher PAHs concentrations where the average concentrations of 50 m stations (868.12 ± 138.35 ng L^-1) ˃ 30 m stations (629.49 ± 143.85 ng L^-1) ˃ 10 m stations (402.79 ± 59.46 ng L^-1). The wind-induced waves re-suspend rich PAHs sediment particles to increase its concentration in the water column. Carcinogenic toxic equivalent quotient (TEQ) for total detected PAHs in the middle and deep water represented more than double (75.46 ng TEQ L^-1) the value in the surface water (34.76 ng TEQ L^-1). The diagnostic ratios and principal component analysis indicated mainly pyrogenic origin in surface, middle, and deep waters.

Silver Nanoparticle Interactions with Surfactant-Based Household Surface Cleaners

Silver nanoparticles (AgNPs) are the most widely used engineered nanomaterials in consumer products, primarily due to their antimicrobial properties. This widespread usage has resulted in concerns regarding potential adverse environmental impacts and increased probability of human exposure. As the number of AgNP consumer products grows, the likelihood of interactions with other household materials increases. AgNP products have the potential to interact with household cleaning products in laundry, dishwashers, or during general use of all-purpose surface cleaners. This study has investigated the interaction between surfactant-based surface cleaning products and AgNPs of different sizes and with different capping agents. One AgNP consumer product, two laboratory-synthesized AgNPs, and ionic silver were selected for interaction with one cationic, one anionic, and one nonionic surfactant product to simulate AgNP transformations during consumer product usage before disposal and subsequent environmental release. Changes in size, morphology, and chemical composition were detected during a 60 min exposure to surfactant-based surface cleaning products using ultraviolet-visible (UV/Vis) spectroscopy, transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX), and dynamic light scattering (DLS). Generally, once AgNP suspensions were exposed to surfactant-based surface cleaning products, all the particles showed an initial aggregation, likely due to disruption of their capping agents. Over the 60 min exposure, cleaning agent-1 (cationic) showed more significant particle aggregates than cleaning agent-2 (anionic) and cleaning agent-3 (nonionic). In addition, UV/Vis, TEM-EDX, and DLS confirmed formation of incidental AgNPs from interaction of ionic silver with all surfactant types.

Dissolution of Silver Nanoparticles in Colloidal Consumer Products: Effects of Particle Size and Capping Agent

The utilization of silver nanoparticles (AgNPs) in consumer products has significantly increased in recent years, primarily due to their antimicrobial properties. Increased use of AgNPs has raised ecological concerns. Once released into an aquatic environment, AgNPs may undergo oxidative dissolution leading to the generation of toxic Ag+. Therefore, it is critical to investigate the ecotoxicological potential of AgNPs and determine the physicochemical parameters that control their dissolution in aquatic environments. We have investigated the dissolution trends of aqueous colloidal AgNPs in five products, marketed as dietary supplements and surface sanitizers. The dissolution trends of AgNPs in studied products were compared to the dissolution trends of AgNPs in well-characterized laboratory-synthesized nanomaterials: citrate-coated AgNPs, polyvinylpyrrolidone-coated AgNPs, and branched polyethyleneimine-coated AgNPs. The characterization of the studied AgNPs included: particle size, anion content, metal content, silver speciation, and capping agent identification. There were small differences in the dissolved masses of Ag+ between products, but we did not observe any significant differences in the dissolution trends obtained for deionized water and tap water. The decrease of the dissolved mass of Ag+ in tap water could be due to the reaction between Ag+ and Cl-, forming AgCl and affecting their dissolution. We observed a rapid initial Ag+ release and particle size decrease for all AgNP suspensions due to the desorption of Ag+ from the nanoparticles surfaces. The observed differences in dissolution trends between AgNPs in products and laboratory-synthesized AgNPs could be caused by variances in capping agent, particle size, and total AgNP surface area in suspensions.