Sources and pathways of carbon and nitrogen of macrophytes and sediments using stable isotopes in Al-Kharrar Lagoon, eastern Red Sea coast, Saudi Arabia.

Elemental ratios (δ13C, δ15N and C/N) and carbon and nitrogen concentrations in macrophytes, sediments and sponges of the hypersaline Al-Kharrar Lagoon (KL), central eastern Red Sea coast, were measured to distinguish their sources, pathways and see how they have been influenced by biogeochemical processes and terrestrial inputs. The mangroves and halophytes showed the most depleted δ13C values of -27.07±0.2 ‰ and -28.34±0.4 ‰, respectively, indicating their preferential 12C uptake, similar to C3-photosynthetic plants, except for the halophytes Atriplex sp. and Suaeda vermiculata which showed δ13C of -14.31±0.6 ‰, similar to C4-plants. Macroalgae were divided into A and B groups based on their δ13C values. The δ13C of macroalgae A averaged -15.41±0.4 ‰, whereas macroalgae B and seagrasses showed values of -7.41±0.8 ‰ and -7.98 ‰, suggesting uptake of HCO3- as a source for CO2 during photosynthesis. The δ13C of sponges was -10.7±0.3 ‰, suggesting that macroalgae and seagrasses are their main favoured diets. Substrates of all these taxa showed δ13C of -15.52±0.8 ‰, suggesting the KL is at present a macroalgae-dominated lagoon. The δ15N in taxa/sediments averaged 1.68 ‰, suggesting that atmospheric N2-fixation is the main source of nitrogen in/around the lagoon. The heaviest δ15N (10.58 ‰) in halophytes growing in algal mats and sabkha is possibly due to denitrification and ammonia evaporation. The macrophytes in the KL showed high C %, N %, and C/N ratios, but this is not indicated in their substrates due possibly to a rapid turnover of dense, hypersaline waters carrying most of the detached organic materials out into the Red Sea. The δ13C allowed separation of subaerial from aquatic macrophytes, a proxy that could be used when interpreting paleo-sea level or paleoclimatic changes from the coastal marine sediments.

Sol-Gel Functionalized Polyurethane Foam-Packed Mini-Column as an Efficient Solid Extractor for the Rapid and Ultra-Trace Detection of Textile Dyes in Water.

Textile dyes widely used in industrial products are known as a major threat to human health and water ecological security. On the other hand, sol gel represents a principal driver of the adoption of dispersive solid-phase microextractors (d-µ SPME) for pollutants residues in water. Thus, the current study reports a new and highly rapid and highly efficient hybrid sol-gel-based sponge polyurethane foam as a dispersive solid-phase microextractor (d-µ-SPME) platform packed mini-column for complete preconcentration and subsequent spectrophotometric detection of eosin Y textile dye in wastewater. The unique porous structure of the prepared sol-gel immobilized polyurethane foams (sol-gel/PUF) has suggested its use for the complete removal of eosin Y dye (EY) from water. In the mini-column, the number (N) of plates, the height equivalent to the theoretical plates (HETP), the critical capacity (CC), and the breakthrough capacities (BC) of the hybrid sol-gel-treated polyurethane foams towards EY dye were determined via the breakthrough capacity curve at various flow rates. Under the optimum condition using the matrix match strategy, the linear range of 0.01-5 µg L-1, LODs and LOQs in the range of 0.006 µg L-1, and 0.01 µg L-1 for wastewater were achieved. The intra-day and inter-day precisions were evaluated at two different concentration levels (0.05 and 5 µg L-1 of dye) on the same day and five distinct days, respectively. The analytical utility of the absorbents packed in pulses and mini-columns to extract and recover EY dye was attained by 98.94%. The column could efficiently remove different dyes from real industrial effluents, and hence the sol-gel/PUF is a good competitor for commercial applications. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements. Therefore, this study has provided a convenient pathway for the preparation of compressible and reusable sponge materials from renewable biomass for efficient removal of EY from the water environment.

Molecular interactions of polyvinyl chloride microplastics and beta-blockers (Diltiazem and Bisoprolol) and their effects on marine meiofauna: Combined in vivo and modeling study.

The ecotoxicological effects of beta-blockers (i.e. Diltiazem and Bisoprolol) and their interactions with the microplastic polyvinyl chloride on marine meiofauna were tested in laboratory microcosms. An experimental factorial design was applied, using meiobenthic fauna collected from the Old Harbor of Bizerte (NE Tunisia), but with a main focus on the nematode communities. The meiobenthic invertebrates were exposed to two concentrations of Diltiazem and Bisoprolol, of 1.8 µg.L-1 and 1.8 mg.L-1, respectively, and one concentration of polyvinyl chloride (i.e. 20 mg.kg-1), separately and mixed. The overall meiofauna abundance was significantly reduced in all treatments, mainly that of polychaetes and amphipods. Moreover, the juveniles-gravid female ratios of the nematode communities were the lowest in the 1.8 µg.L-1 Bisoprolol treatment and for the 1.8 mg.L-1 mixture of Diltiazem and microplastics, suggesting that different dosages influence the maturity status of the examined species. The demographic results were also supported by in silico approach. The simulation of molecular interactions revealed acceptable binding affinities (up to -8.1 kcal/mol) and interactions with key residues in the germ line development protein 3 and sex-determining protein from Coenorhabditis elegans. Overall, the experimental outcome strongly indicates synergistic interactions among the beta-blockers Diltiazem and Bisoprolol and the microplastic polyvinyl chloride on marine nematode communities.