Microplastics in the Marine Environment: A Review of Their Sources, Formation, Fate, and Ecotoxicological Impact

Global plastic production is on the rise, and improper plastic management leads to the disposal of plastic in the environment, wherein it enters the environment, after degradation, as microplastics (size < 5 mm) and nanoplastics (size < 1 μm). The most common sink for the microplastics is the marine environment, including the sediment, deep sea, shorelines, and oceans. The objective of this study is to collate the environmental impact assessment of the microplastics in the marine habitat, focusing on the following main elements: (a) source and type of microplastics, specifically leading to the marine sink; (b) degradation pathways; (c) ecotoxicological impact on marine biota, since the smaller-sized microplastics can be digested by the marine biota and cause threats to them; (d) fate of microplastic in the marine environment, including the modes of transport and deposition. This chapter aims to provide a deeper insight into the fate of microplastics once it enters the marine environment, and the information could be a useful reference for the development of microplastic risk management strategies

Emerging Themes and Future Directions of Multi-Sector Nexus Research and Implementation

Water, energy, and food are all essential components of human societies. Collectively, their respective resource systems are interconnected in what is called the “nexus”. There is growing consensus that a holistic understanding of the interdependencies and trade-offs between these sectors and other related systems is critical to solving many of the global challenges they present. While nexus research has grown exponentially since 2011, there is no unified, overarching approach, and the implementation of concepts remains hampered by the lack of clear case studies. Here, we present the results of a collaborative thought exercise involving 75 scientists and summarize them into 10 key recommendations covering: the most critical nexus issues of today, emerging themes, and where future efforts should be directed. We conclude that a nexus community of practice to promote open communication among researchers, to maintain and share standardized datasets, and to develop applied case studies will facilitate transparent comparisons of models and encourage the adoption of nexus approaches in practice

Emerging Themes and Future Directions of Multi-Sector Nexus Research and Implementation

Water, energy, and food are all essential components of human societies. Collectively, their respective resource systems are interconnected in what is called the “nexus”. There is growing consensus that a holistic understanding of the interdependencies and trade-offs between these sectors and other related systems is critical to solving many of the global challenges they present. While nexus research has grown exponentially since 2011, there is no unified, overarching approach, and the implementation of concepts remains hampered by the lack of clear case studies. Here, we present the results of a collaborative thought exercise involving 75 scientists and summarize them into 10 key recommendations covering: the most critical nexus issues of today, emerging themes, and where future efforts should be directed. We conclude that a nexus community of practice to promote open communication among researchers, to maintain and share standardized datasets, and to develop applied case studies will facilitate transparent comparisons of models and encourage the adoption of nexus approaches in practice

Solubilities of PAHs in alcohol-water mixtures

Solubilities of phenanthrene, pyrene, and perylene were determined in aqueous solutions containing either methanol, ethanol, or propanol at alcohol volume fractions ranging from zero to nearly one, at 25\sp\circC under atmospheric pressure. These data, and data from the literature on naphthalene, were compared to 2, 3, and 4 interaction-parameter Margules equations and UNIFAC predictions. For each solute-solvent-cosolvent (i.e., PAH-water-alcohol) system examined, the solubility of each PAH increased with increasing alcohol volume fraction. The UNIFAC model poorly estimated solubilities at cosolvent volume fractions near 0.5. Analysis of the data with various forms of the Margules equations suggests that, in addition to solute-solvent and solute-cosolvent interactions, solvent-cosolvent (i.e., water-alcohol) and solute-solvent-cosolvent interactions are important at cosolvent volume fractions near 0.5. A simplified three-suffix Margules model is proposed, which includes terms for all these interactions and accurately estimates the experimental data with a consistent set of interaction parameters. All interaction parameters involving solute molecules may be estimated from the octanol-water partition coefficient, K\sb{ow}, of the respective solute. This empirical result suggests that the solubility of other PAHs in similar alcohol-water mixtures may be estimated from K\sb{ow}, and enthalpy of fusion. Additionally, extension of Margules equations to quaternery systems were conducted and evaluated. Generally, the two-suffix model is able to calculate the PAHs solubilities in ternary solvent systems studied. The deviation of calculated PAH\u27s solubilities from experimental measurements for systems containing phenol as cosolvent results from the complex molecular interactions of phenol. Similar solubility data for phenanthrene and pyrene were determined at 4\sp\circ and 43\sp\circC. Combined the data at 25\sp\circC, these data were analyzed with van\u27t Hoff\u27s equation. At each temperature, solubility increases as alcohol volume fraction concentration increases. The data suggests that excess enthalpies of the solute are close to zero. Assuming excess enthalpies as zero, excess entropy was calculated to be nearly independent of temperature