Unveiling the Vertical Migration of Microplastics with Suspended Particulate Matter in the Estuarine Environment: Roles of Salinity, Particle Properties, and Hydrodynamics.

The estuary is an energetic area connecting the inland, river, and ocean. The migration of microplastics (MPs) in this highly complex area is tied to the entire ecosystem. In this study, the effects of cohesive SPM (clay) and noncohesive SPM (sand) on the vertical migration of positively buoyant MPs, polyethylene (PE), and negatively buoyant MPs, polytetrafluoroethylene (PTFE), in the estuarine environment under hydrodynamic disturbances were investigated. The settling of positively buoyant MPs was more reliant on the cohesive SPM compared to the settling of negatively buoyant MPs. Moreover, MPs interacting with the SPM mixture at a clay-to-sand ratio of 1:9 settled more efficiently than those interacting with clay alone. A significant positive correlation was observed between MP settling percentage and the salinity level. MP settling percentage was significantly negatively correlated with fluid shear stress for both types of MPs, meanwhile, negatively buoyant MPs were able to resist greater hydraulic disturbances. In the low-energy mixing state, for both types of MPs, the settling percentage reached about 50% in only 10 min. The resuspension process of MPs under hydrodynamic disturbances was also uncovered. Additionally, the migration and potential sites of MPs were described in the context of prevalent environmental phenomena in estuaries.

Cleanup of oiled shorelines using a dual responsive nanoclay/sodium alginate surface washing agent.

Oil spills may affect ecosystems and endanger public health. In this study, we developed a novel and dual responsive nanoclay/sodium alginate (NS) washing fluid, and systematically evaluated its application potential in oiled shoreline cleanup. The characterization results demonstrated that sodium alginate combined with nanoclay via hydrogen bonds, and was inserted into the interlayer spacing of nanoclay. Adding sodium alginate reduced surface and interfacial tensions, while increasing the viscoelasticity of the washing fluid. Batch experiments were conducted to investigate oil removal performance under various conditions. Additionally, the factorial design analysis showed that three single factors (temperature, oil concentration, and salinity), and two interactive effects (temperature/salinity; and oil concentration/HA) displayed significant effects on the oil removal efficiency of the NS washing fluid. Compared to the commercial surfactants, the NS composite exhibited satisfactory removal efficiencies for treating oily sand. Green materials-stabilized Pickering emulsion can potentially be used for oil/water separation. The NS washing agent displayed excellent pH- and Ca2+- responsiveness, generating transparent supernatants with low oil concentration and turbidity. Our work opens an interesting avenue for designing economical, high performance, and green washing agents.

A framework for the evaluation and selection of shoreline surface washing agents in oil spill response.

The shorelines frequently suffer adverse impacts from oil spill accidents. As one important technique of shoreline cleanup, the application of surface washing agents (SWAs) can help achieve high oil removal from shoreline substrates with less damage to affected zone. In this study, a framework for evaluation and selection of SWAs in oil spill incidents was constructed to better understand and apply this technique. A decision tree was firstly developed to illustrate all possible scenarios which are appropriate to use SWAs in consideration of oil collectability, shoreline character, types and amount of stranded oil, and cleanup requirement. Based on literature review, theoretical modeling, and experts' suggestions, an integrated multi-criteria decision analysis (MCDA) method was then come up to select the most preferred SWA from five aspects of toxicity, effectiveness, minimal dispersion, demonstrated field test, and cost. Its suitability and rationality were proved by a hypothetical case. In addition, sensitivity analysis was performed by changing the weight of each criterion independently to check the priority rank of alternatives, and it also verified the robustness and stability of this model. The presented framework has significant implications for future research and application of SWAs in the shoreline cleanup.

Investigation into the oil removal from sand using a surface washing agent under different environmental conditions.

Spilled oil frequently reaches the shorelines and affects coastal biota and communities. The application of surface washing agents is an important shoreline cleanup technique that can help remove stranded oil from substrate surfaces with the advantages of high removal efficiency, low toxicity, and strong economic viability. In this study, the investigation into the oil removal from contaminated sand using a surface washing agent under variable environmental conditions was conducted. A preliminary test was conducted to obtain the optimal combination of operating factors of surface washing agent-to-oil ratio (SOR) 2:1, mixing speed 150 rpm, and mixing time 30 min. The results of single-factor experiments showed that high temperature and humic acid concentration of flush water contributed to the performance of a surface washing agent, while salinity and kaolinite concentration could inhibit its performance. The factorial analysis revealed the main effects of temperature and salinity, and the interactive effects of temperature and salinity as well as salinity and humic acid concentration that were significant to the washing efficiency of the surface washing agent. In addition, the comprehensive assessment of a surface washing agent from the aspects of toxicity, detergency, dispersion properties, and field trials was conducted. The results have significant implications for future application of surface washing agents in the shoreline cleanup.

Spotlight on the vertical migration of aged microplastics in coastal waters.

Coastal waters are complex and dynamic areas with unique environmental attributes that complicate the vertical migration of microplastics (MPs). The MPs that enter coastal waters from diverse sources, including terrestrial, riverine, oceanic, and shoreline inputs undergo various aging pathways. In this study, the variations in the physiochemical characteristics of MPs undergoing various aging pathways and their vertical migration under dynamic conditions subjected to the effects of different MP characteristics and coastal environmental features were comprehensively explored. Opposite effects of aging on the vertical migration of hydrophobic and hydrophilic MPs were observed, with aging appearing to promote the dispersion of hydrophobic MPs but enhance the vertical migration of hydrophilic ones. The positive role of salinity and the negative role of humic acid (HA) concentrations on MP vertical migration were identified, and the mechanisms driving these effects were analyzed. Notably, intense turbulence not only promoted the floating of positively buoyant MPs but also reversed the migration direction of negatively buoyant MPs from downward to upward. Aging-induced changes in MP characteristics had a limited effect on MP vertical migration. The inherent characteristics of MPs and the surrounding environmental features, however, played major roles in their vertical migration dynamics. ENVIRONMENTAL IMPLICATION: Microplastics (MPs) have emerged as a significant global environmental concern and the coastal zones are the hotspots for MP pollution due to their high population density. This study comprehensively investigated the variations in the physiochemical characteristics of MPs undergoing various aging pathways. Their vertical migration patterns under dynamic conditions subjected to the effects of different MP characteristics and coastal environmental features were revealed. The roles of turbulence and MP density in their migration were identified. The findings of this study have important implications for understanding the transport and determining the ecological risks of MPs in coastal waters.

Assessment of the infiltration of water-in-oil emulsion into soil after spill incidents.

The issue of inland oil spills exerts an adverse impact on environmental and ecological health. Many cases are concerned with water-in-oil emulsions, especially in the oil production and transport system. To understand the contamination and take an efficient response work after spill, this study investigated the infiltration behavior of water-in-oil emulsions and the influencing factors by measuring the characteristics of different emulsions. The results showed that an increase of water and fine particle content and decrease in temperature would improve the viscosity of emulsions and reduce the infiltration rate, whereas salinity levels had a negligible impact on infiltration if the pour point of emulsion systems was far higher than the freezing point of water droplets. It is worth mentioning that excessive water content at a high temperature may cause demulsification during the infiltration process. The oil concentration in different soil layers was related to the viscosity of emulsion and infiltration depth, and the adopted Green-Ampt model simulated well under low temperature. This study reveals the new features of emulsion infiltration behavior and distribution patterns under different conditions and is helpful for the response work after spill accidents.

An insight into the benefits of substituting polypropylene with biodegradable polylactic acid face masks for combating environmental emissions.

Mask waste can affect the natural environment and human health. In this study, the life cycle assessment (LCA) of two types of face masks (Polylactic acid (PLA) and Polypropylene (PP)) was first performed to evaluate the environmental impacts from production to end-of-life, and then, greenhouse gas (GHG) emissions were estimated for each life stage. The GHG emissions for one functional unit of PP and PLA face masks were estimated to be 6.27E+07 and 5.06E+07 kg CO2 eq, respectively. Explicitly, PLA mask production emissions are 37 % lower as compared to those for PP masks. Packaging has been recognized as a major GHG source throughout the product's life cycle. This study may provide a new insight into the environmental benefits of reducing GHG emissions within PLA face mask life cycles. Biodegradable and environmentally friendly materials can be used in the manufacturing and packaging of face masks.

Preparation, characteristics, and performance of the microemulsion system in the removal of oil from beach sand.

Oil deposited on shoreline substrates has serious adverse effects on the coastal environment and can persist for a long time. In this study, a green and effective microemulsion (ME) derived from vegetable oil was developed as a washing fluid to remove stranded oil from beach sand. The pseudo-ternary phase diagrams of the castor oil/water (without or without NaCl)/Triton X-100/ethanol were constructed to determine ME regions, and they also demonstrated that the phase behaviors of ME systems were almost independent of salinity. ME-A and ME-B exhibited high oil removal performance, low surfactant residues, and economic benefits, which were determined to be the W/O microstructure. Under optimal operation conditions, the oil removal efficiencies for both ME systems were 84.3 % and 86.8 %, respectively. Moreover, the reusability evaluation showed that the ME system still had over 70 % oil removal rates, even though it was used six times, implying its sustainability and reliability.

Development of a calcium alginate-cellulose nanocrystal-based coating to reduce the impact of oil spills on shorelines.

It is well known that oil stranded on shoreline substrates can be difficult to remove and cause serious environmental effects. To address this issue, a calcium alginate-cellulose nanocrystal (CA-CNC)-based coating with a unique surface structure and superhydrophobic properties was developed to reduce the extent of shoreline oiling. The results of batch washing test showed that not only did the introduction of CNC not reduce the oil removal efficiency; it also improved the environmental stability of the coating to resist the effects associated with seawater immersion and erosion (especially in the case of 0.4 wt% of CNC). The oil-repellent performance of the coated gravels implied that both oscillation time and oil concentration had almost no effects on the amount of adhered oil. Assessment of oiling prevention based on the laboratory shoreline tank simulator proved the coated gravel performed very well as more oil floated and less oil remained on substrates and penetrated into the subsurface. Biotoxicity analysis showed that the coating powders reduced impacts on the toxicity of the oil to algae at low doses. There is a good potential for the use of this CA-CNC based coating technique to improve shoreline oil spill response.

Exploring the use of alginate hydrogel coating as a new initiative for emergent shoreline oiling prevention.

Marine oil spills are often reported as a result of activities associated with oil exploration, production and transportation. The spilled oil may reach the shoreline, and then the stranded oil can persist for a long time, exerting many negative effects on coastal ecosystems. Conventional shoreline cleanup methods cannot effectively remove the oil residues from affected areas and are very expensive. Therefore, the use of alginate hydrogel coatings was proposed as a new initiative for emergent shoreline oiling prevention. The alginate hydrogel-coated gravels showed high surface roughness, as well as remarkable water wetting and low-oil-adhesion properties. There was a low oil adhesion on the coated gravels in the continuous test with oil/water emulsion flow, indicating the excellent oil-repellent properties of the coated substrate. The results of batch oil-repellent tests showed that independent of the kind or weathering degree of the oil used, oil can be easily washed out from the coated gravels. The coated gravels had good environmental stability and the slightly partial de-crosslinking of alginate structure would not reduce the oil repellence performance. Moreover, the performance of the alginate hydrogel-coated gravel was further proved with a laboratory shoreline tank simulator, in which more stranded oil floated to the water surface and less oil remained on gravels and entered into subsurface. This proposed oiling prevention method can be used not only for shorelines but also for coastal piers, seaports, and solid manmade shorelines. The coating material is derived from the biomass in the ocean and can be degraded under natural conditions. This study may provide a unique direction for the future development of green oil spill control strategy.

[Study of the relative factors of cure depths of light curing composite resin].

PURPOSE: To investigate the effect of different composite resin, different light curing units, different irradiation time, different irradiation distance on cure depths of light curing composite resin. METHODS: Designed by factorial experiment, 192 Cylindrical samples were made with 4mm internal diameter and 6mm high mold. The whole samples were scanned by Planmeca ProMax panoramic X-ray unit, cure depths were measured using a scoping method described in the ISO standard for resin-based composites. The data was statistically analyzed by SPSS11.5 software package for ANOVA. RESULTS: The differences of four factors-composite resin, light curing units, irradiation time, irradiation distance were significant (P<0.01), and the effects between-subjects were involved among four factors (P<0.01). CONCLUSIONS: From this study, we conclude that cure depths may be affected by two kinds of light curing units, two kinds of composite resin, four kinds of irradiation time and four kinds of irradiation distances, once each factor is strengthened, cure depths could reach a more ideal effect. Supported by Key Research Project of Science and Technology Committee of Liaoning Province (Grant No.00225001).