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Review of Modeling Approaches at the Freshwater and Saltwater interface in Coastal Aquifers
No full textAround 40% of the world’s population depends on coastal aquifers for freshwater supply but natural and anthropogenic drivers threaten groundwater availability. Of these drivers, saltwater intrusion (SWI) is one of the most critical and is increasingly affecting coastal areas worldwide. Interest in coastal aquifers has significantly increased, as demonstrated by the growing number of publications in which researchers describe various approaches to illuminate the importance of coastal aquifers, specifically with regard to SWI. The state of research and knowledge of the coastal SWI issue has been reviewed herein. The review includes a discussion of select geophysical and field methods and tools which can inform the numerical modeling of coastal aquifers. MODFLOW was identified as the most often used numerical modeling platform. Further, while many research sites, particularly in the United States, were identified where field studies and geophysical methods, mostly geoelectric ones, added important value to the numerical modeling of the SWI process in the coastal zone, in some regions of the world, data scarcity was identified as the main challenge. Overall, numerical modeling, combined with geophysical methods, is a valuable tool for studying SWI and managing coastal water resources
Assessing the Reservoir Inflow Relationship for Effective Flood Mitigation: A Hydrologic Modeling Approach for Scituate Reservoir, Rhode Island
No full textMajor drinking water reservoirs can mitigate downstream flooding after extreme weather events if reservoir management decisions are guided by well parameterized and calibrated computational models of reservoir inflow. We applied a hydrologic modeling approach to the inflow of a major drinking water reservoir. Three highly parameterized models were developed for assessing the spatial and temporal relationship between high and low stream flows as a function of 1) surface/subsurface runoff process and channel routing parameters (FSP), 2) flow timing and snow accumulation (SSP) and, 3) combination of FSP and SSP (COMP). Multi-site calibration and multi-site parameterization were used to evaluate the model performance. We found a positive relationship between FSP or COMP with high flow in the watershed, but the SSP modeling parameters alone were found insufficient, capturing high flow conditions accurately even though the SSP model uncertainty was less than the FSP and COMP. The spatial and temporal prediction of low flow conditions resulted in an overestimation by 3% from observed low flow which is acceptable for assessing low flow impact. The approach to model parameterization and the results presented will have positive impacts on reservoir management during high or low flow times
Shock response of sandwich panels with additively manufactured polymer gyroid lattice cores
No full textThis work evaluates the shock response of sandwich structures with gyroid lattice cores made from Polylactic Acid (PLA), Acrylonitrile Butadiene Styrene (ABS), and Thermoplastic Polyurethane (TPU) using shock tube experiments coupled with high-speed photography and digital image correlation (DIC). The study found that gyroid lattice structures exhibit high energy absorption capacity and good structural integrity under shock loading, making them suitable for high strength-to-weight ratio and energy absorption applications in aerospace and defense industries. The sandwich panel with a TPU-core structure exhibited the highest deformation under shock loading, with a maximum deflection of approximately 6 mm, followed by ABS at 0.9 mm and PLA at 0.82 mm. Under shock loading, the sandwich panel with TPU gyroid core exhibited the highest specific deformation energy (0.146 J/g), which is consistent with its flexibility, though it remained in the same general order as ABS (0.104 J/g) and PLA (0.070 J/g). Interestingly, the specific total energy of the TPU gyroid core sandwich, while the lowest at 39.310 J/g, was still relatively close to ABS (54.098 J/g) and PLA (52.620 J/g), despite the substantial difference in inherent stiffness of TPU compared to ABS and PLA. This suggests that while TPU\u27s stiffness is much lower compared to PLA and ABS, its total energy absorption capability in gyroid form is not as drastically reduced, indicating the importance of geometry and mass distribution within the gyroid structure. Overall, the results of this study highlight the importance of careful design and optimization of these structures to utilize their unique properties fully
An investigation into the electromechanical performance of textile fabrics with conductive yarn elements for data transfer capabilities
No full textThis paper investigates the electromechanical performance of textile fabric with conductive yarn elements for data transmission capabilities. Electromechanical experiments were conducted to evaluate the electrical response of copper yarn elements stitched axially to the textile fabric, while assessing the mechanical response of the system during tensile tests under axial loading. The results indicated that the yarn element exhibited low electricomechanical coupling below 1.5% strain, making it suitable for consistent electrical performance during low mechanical strain conditions. Computational models were also developed and correlated with the experimental results of the conductive yarn. The computational model was then expanded to investigate the effect of the braiding angle in the braiding system, providing insights into how these parameters influence the system’s performance. Overall, this research contributes valuable insights into the electromechanical behavior of textile fabric with conductive yarn elements, and presents a framework for optimizing data transfer capabilities in e-textiles and smart textile applications. The findings open opportunities for further advancements in the design and engineering of functional textiles for a wide range of applications
Pivotal Roles of Triple Screening-Topological, Electrostatic, and Hydrodynamic-On Dynamics in Semidilute Polyelectrolyte Solutions
No full textFor semidilute polyelectrolyte solutions, it is generally assumed that topological, electrostatic, and hydrodynamic interactions are screened (called triple screening). Despite a large body of research focused on polyelectrolyte solutions, the concept of triple screening has never been rigorously verified. In this work, we test the concept by probing concentration fluctuations in aqueous solutions containing a well-studied polyelectrolyte, sodium poly(styrenesulfonate) (NaPSS) with neutron scattering, theory, and molecular dynamics simulations. Neutron spin-echo (NSE) and small-angle neutron scattering (SANS) data from semidilute solutions of NaPSS are presented at different polymer and salt (NaCl) concentrations. A combined theory for structure (J. Chem. Phys. 105, 5183 (1996)) and dynamics (J. Chem. Phys. 107, 2619 (1997)), which captures effects of hydrodynamic, topological, and electrostatic screening, is used to interpret the experimental results. The theory quantitatively predicts the decay rate obtained from the NSE measurements while capturing the shape and concentration dependencies of the polyelectrolyte peak observed in the SANS spectra. Detailed comparisons of the theory and the experiments reveal that the wavevector-dependent decay rate of concentration fluctuations in semidilute solutions of polyelectrolytes is dictated by the screening of hydrodynamic, topological, and electrostatic interactions. This conclusion is corroborated by coarse-grained molecular dynamics simulations, executed without any hydrodynamic interactions, which fail to capture the correct wavevector dependence of the decay rate. These results highlight that the theories based on the concept of triple screening provide a quantitative framework for predicting a relation between the structure and dynamics of polyelectrolyte solutions
Bioconcentration of per- and polyfluoroalkyl substances and precursors in fathead minnow tissues environmentally exposed to aqueous film-forming foam–contaminated waters
Get PDFExposure to per- and polyfluoroalkyl substances (PFAS) has been associated with toxicity in wildlife and negative health effects in humans. Decades of fire training activity at Joint Base Cape Cod (MA, USA) incorporated the use of aqueous film-forming foam (AFFF), which resulted in long-term PFAS contamination of sediments, groundwater, and hydrologically connected surface waters. To explore the bioconcentration potential of PFAS in complex environmental mixtures, a mobile laboratory was established to evaluate the bioconcentration of PFAS from AFFF-impacted groundwater by flow-through design. Fathead minnows (n = 24) were exposed to PFAS in groundwater over a 21-day period and tissue-specific PFAS burdens in liver, kidney, and gonad were derived at three different time points. The ∑PFAS concentrations in groundwater increased from approximately 10,000 ng/L at day 1 to 36,000 ng/L at day 21. The relative abundance of PFAS in liver, kidney, and gonad shifted temporally from majority perfluoroalkyl sulfonamides (FASAs) to perfluoroalkyl sulfonates (PFSAs). By day 21, mean ∑PFAS concentrations in tissues displayed a predominance in the order of liver \u3e kidney \u3e gonad. Generally, bioconcentration factors (BCFs) for FASAs, perfluoroalkyl carboxylates (PFCAs), and fluorotelomer sulfonates (FTS) increased with degree of fluorinated carbon chain length, but this was not evident for PFSAs. Perfluorooctane sulfonamide (FOSA) displayed the highest mean BCF (8700 L/kg) in day 21 kidney. Suspect screening results revealed the presence of several perfluoroalkyl sulfinate and FASA compounds present in groundwater and in liver for which pseudo-bioconcentration factors are also reported. The bioconcentration observed for precursor compounds and PFSA derivatives detected suggests alternative pathways for terminal PFAS exposure in aquatic wildlife and humans. Environ Toxicol Chem 2024;00:1–12. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC
Considerations and challenges in support of science and communication of fish consumption advisories for per- and polyfluoroalkyl substances
Get PDFFederal, state, tribal, or local entities in the United States issue fish consumption advisories (FCAs) as guidance for safer consumption of locally caught fish containing contaminants. Fish consumption advisories have been developed for commonly detected compounds such as mercury and polychlorinated biphenyls. The existing national guidance does not specifically address the unique challenges associated with bioaccumulation and consumption risk related to per- and polyfluoroalkyl substances (PFAS). As a result, several states have derived their own PFAS-related consumption guidelines, many of which focus on one frequently detected PFAS, known as perfluorooctane sulfonic acid (PFOS). However, there can be significant variation between tissue concentrations or trigger concentrations (TCs) of PFOS that support the individual state-issued FCAs. This variation in TCs can create challenges for risk assessors and risk communicators in their efforts to protect public health. The objective of this article is to review existing challenges, knowledge gaps, and needs related to issuing PFAS-related FCAs and to provide key considerations for the development of protective fish consumption guidance. The current state of the science and variability in FCA derivation, considerations for sampling and analytical methodologies, risk management, risk communication, and policy challenges are discussed. How to best address PFAS mixtures in the development of FCAs, in risk assessment, and establishment of effect thresholds remains a major challenge, as well as a source of uncertainty and scrutiny. This includes developments better elucidating toxicity factors, exposures to PFAS mixtures, community fish consumption behaviors, and evolving technology and analytical instrumentation, methods, and the associated detection limits. Given the evolving science and public interests informing PFAS-related FCAs, continued review and revision of FCA approaches and best practices are vital. Nonetheless, consistent, widely applicable, PFAS-specific approaches informing methods, critical concentration thresholds, and priority compounds may assist practitioners in PFAS-related FCA development and possibly reduce variability between states and jurisdictions