Salt Marsh Hydrogeology: A Review

Groundwater–surface water exchange in salt marsh ecosystems mediates nearshore salt, nutrient, and carbon budgets with implications for biological productivity and global climate. Despite their importance, a synthesis of salt marsh groundwater studies is lacking. In this review, we summarize drivers mediating salt marsh hydrogeology, review field and modeling techniques, and discuss patterns of exchange. New data from a Delaware seepage meter study are reported which highlight small-scale spatial variability in exchange rates. A synthesis of the salt marsh hydrogeology literature reveals a positive relationship between tidal range and submarine groundwater discharge but not porewater exchange, highlighting the multidimensional drivers of marsh hydrogeology. Field studies are heavily biased towards microtidal systems of the US East Coast, with little global information available. A preliminary estimate of marsh porewater exchange along the Mid-Atlantic and South Atlantic Bights is 8–30 × 1013 L y−1, equivalent to recirculating the entire volume of seawater overlying the shelf through tidal marsh sediments in ~30–90 years. This review concludes with a discussion of critical questions to address that will decrease uncertainty in global budget estimates and enhance our capacity to predict future responses to global climate change

Understanding cell-autonomous and non-autonomous signalling events in stomatal immunity

Stomata are entry sites for bacterial pathogens and can affect the outcome of infection to the disadvantage of the pathogen. This is referred to as stomatal immunity. Guard cells can mediate certain responses in a cell-autonomous manner, but this question remains to be addressed for pathogen-induced stomatal closure. This study reports transient and stable transgenic approaches to study guard cell responses. I employed virus-induced gene silencing and guard cell-specific promoters to investigate guard cell autonomy and non-autonomous signalling events during pathogen-induced stomatal closure. Plants that express FLAGELLIN SENSING 2 (FLS2) only in the guard cells retained stomatal closure to flg22 and wild-type-like susceptibility levels to bacterial infection. Interestingly, guard cell-specific knock-down of FLS2 did not impair stomatal closure or resistance to bacteria, suggesting that non-autonomous signalling events can mediate stomatal closure during pathogen invasion. Screening mutants of abscisic acid (ABA) signalling components revealed that pathogen-induced stomatal closure is independent from the prototypic drought stomatal closure pathway. I showed that OPEN STOMATA 1 is not involved in pathogen-induced stomatal closure and that it was inactive after flg22 treatment. Instead, the mutant of a related kinase SUCROSE NON-FERMENTING RECEPTOR KINASE 2.3 (SnRK2.3) was impaired in its flg22 stomatal closure response suggesting that SnRK2.3 plays an important role in this response. SnRK2.3 interacted with BOTRYRIS-INDUCED KINASE 1 in split-YFP and co-immunoprecipitation assays. Interestingly, the PBS1-like 1 (PBL1) mutant was impaired in flg22-induced stomatal closure and PBL1 activated SLOW ANION CHANNEL-ASSOCIATED 1 HOMOLOGUE 3 (SLAH3) in oocyte measurements. This suggests PBL1 as major player in MAMP-induced stomatal closure. My data reveal that aspects of stomatal immunity involve both guard cell-specific signalling events and non-symplastic cell-to-cell signalling. This work implicates independence of ABA- and pathogen-induced stomatal closure pathways and PBL1 as major regulator through direct activation of the anion channel SLAH3

Medium Ionization for Improved Aerodynamic Performance

Project DRIFT (Drag Reducing Ionized Flow Technology) aimed to improve aerodynamic performance and efficiency by ionizing the air that flows over an aircraft’s wing in subsonic, compressible regimes. To do so, viscous skin friction and resulting drag were reduced via the effects of corona discharge, an electrically induced phenomenon that alters the properties of the medium in which it resides. The corona discharge creates a flow with unique ionized properties that may lead to the ability to control aerodynamic characteristics. To achieve such a phenomenon, voltages of up to 15,000 volts were generated through a neon transformer and introduced to the models through electric diode pairs. Wind tunnel testing in conjunction with force balances allowed for drag measurements of various models with and without the corona activated. This allowed for the analysis and study of the ionization acting as a body force and adding momentum to the flow, delaying flow separation and improving aerodynamic performance. This quantitative data was analyzed and resulting in DRIFT’s conclusions surrounding the application of medium ionization within compressible flows

Currency option pricing with stochastic interest rates and transaction costs : a theoretical model

Digitised version produced by the EUI Library and made available online in 2020

When Moral Foundations Collide: An Examination of Liberals' and Conservatives' Reactions to Cross-foundational Moral Trade-offs

Two studies extended previous research on Moral Foundations Theory (MFT; Graham, Haidt, & Nosek, 2009) by examining the extent to which political ideology moderates the psychological reactions to various types of moral dilemmas. In Study 1, participants responded to moral dilemmas that asked them to trade-off between moral foundations related to individual rights (individualizing) and/or foundations related to social order and the restriction of behavior (binding). For trade-offs crossing individualizing with binding foundations, conservatives were more likely than liberals to experience negative affect, arousal, and difficulty making a decision while contemplating these trade-offs. Also, liberals were more likely than conservatives to clearly prefer the individualizing option. Study 2 tested whether affirming one's endorsement of individualizing or binding foundations could alleviate the threat induced by contemplating trade-offs between two moral values. Some participants were given the opportunity to credential themselves on either individualizing or binding foundations. and then responded to individualizing versus binding trade-offs. The manipulation had no consistent effect of any of the dependent variables. Although the hypotheses for Study 2 were not supported, both studies suggest that association between political ideology and moral foundations extend to complex and realistic dilemmas and might be driven by cultural conservatism or authoritarianism in particular

Combining airborne thermal infrared images and radium isotopes to study submarine groundwater discharge along the French Mediterranean coastline

The French Mediterranean coastline, which includes karstic springs discharging into coastal seas and coastal lagoons. Study focus We investigated submarine groundwater discharge (SGD), an important vector for many chemical elements that may impact the quality of the coastal environment. First, we acquired airborne thermal infrared (TIR) images to detect terrestrial groundwater inputs. Then we report in situ data (salinity; temperature; radium isotopes). We use these data i) to confirm the presence of groundwater discharge and to characterize the different systems, and ii) to quantify SGD fluxes and estimate the residence time of the water bodies. New hydrological insights for the region Few studies have been conducted on SGD along the French Mediterranean coastline. The terrestrial groundwater spring inputs in La Palme and Salses-Leucate coastal lagoons are in the range (0.04–0.11) m 3 s −1 , ≤ 2% of the local river inputs. In comparison, total SGD estimates to La Palme lagoon (0.56–1.7 m 3 s −1 ) suggest that the recirculation of lagoon water through the sediment is two orders of magnitude greater than the terrestrial groundwater inputs. At the Calanque of Port-Miou, the terrestrial groundwater flux to the coastal seas was between 0.6 and 1.2 m 3 s −1 in July 2009. This study demonstrates the application of airborne TIR remote sensing for detecting surficial groundwater springs, and the inability of the method to detect deeper, submerged springs

Revisiting \u3csup\u3e228\u3c/sup\u3eTh as a Tool for Determining Sedimentation and Mass Accumulation Rates

The use of 228Th has seen limited application for determining sedimentation and mass accumulation rates in coastal and marine environments. Recent analytical advances have enabled rapid, precise measurements of particle-bound 228Th using a radium delayed coincidence counting system (RaDeCC). Herein we review the 228Th cycle in the marine environment and revisit the historical use of 228Th as a tracer for determining sediment vertical accretion and mass accumulation rates in light of new measurement techniques. Case studies comparing accumulation rates from 228Th and 210Pb are presented for a micro-tidal salt marsh and a marginal sea environment. 228Th and 210Pb have been previously measured in mangrove, deltaic, continental shelf and ocean basin environments, and a literature synthesis reveals that 228Th (measured via alpha or gamma spectrometry) derived accumulation rates are generally equal to or greater than estimates derived from 210Pb, reflecting different integration periods. Use of 228Th is well-suited for shallow (\u3c15 cm) cores over decadal timescales. Application is limited to relatively homogenous sediment profiles with minor variations in grain size and minimal bioturbation. When appropriate conditions are met, complimentary use of 228Th and 210Pb can demonstrate that the upper layers of a core are undisturbed and can improve spatial coverage in mapping accumulation rates due to the higher sample throughput for sediment 228Th

A quasi 3D approach for the modelling of an automotive turbocharger's compressor

In this work the 3DCell method has been extended to the thermo-fluid dynamic simulation of an automotive turbocharger's compressor. The 3DCell, an approach continuously developed by the authors at Politecnico di Milano, is based on a pseudo-staggered leapfrog method that allows to decompose a generic 3D problem in a set of 1D scalar equation arbitrarily oriented in space. The system of equations has been solved referring to a relative rotating framework for the moving components, whereas to an absolute reference elsewhere. The domain has been discretized on a basis of a polar coordinate system, identifying five macro sub-domains, namely the inlet pipe, impeller, vaneless diffuser, volute, outlet pipe, each treated numerically in a specific way. The diffuser's momentum in the tangential direction has been modelled resorting to the conservation of the angular momentum, while the rotor channels are modelled as rotating pipes that exchange work and momentum with the blades as they experience a relative source term due to the centrifugal force field and its potential. The model has been validated against measurements carried out on a steady state flow test bench at University of Genoa

Revisiting 228Th as a tool for determining sedimentation and mass accumulation rates

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tamborski, J., Cai, P., Eagle, M., Henderson, P., & Charette, M. Revisiting 228Th as a tool for determining sedimentation and mass accumulation rates. Chemical Geology, 607, (2022): 121006, https://doi.org/10.1016/j.chemgeo.2022.121006.The use of 228Th has seen limited application for determining sedimentation and mass accumulation rates in coastal and marine environments. Recent analytical advances have enabled rapid, precise measurements of particle-bound 228Th using a radium delayed coincidence counting system (RaDeCC). Herein we review the 228Th cycle in the marine environment and revisit the historical use of 228Th as a tracer for determining sediment vertical accretion and mass accumulation rates in light of new measurement techniques. Case studies comparing accumulation rates from 228Th and 210Pb are presented for a micro-tidal salt marsh and a marginal sea environment. 228Th and 210Pb have been previously measured in mangrove, deltaic, continental shelf and ocean basin environments, and a literature synthesis reveals that 228Th (measured via alpha or gamma spectrometry) derived accumulation rates are generally equal to or greater than estimates derived from 210Pb, reflecting different integration periods. Use of 228Th is well-suited for shallow (<15 cm) cores over decadal timescales. Application is limited to relatively homogenous sediment profiles with minor variations in grain size and minimal bioturbation. When appropriate conditions are met, complimentary use of 228Th and 210Pb can demonstrate that the upper layers of a core are undisturbed and can improve spatial coverage in mapping accumulation rates due to the higher sample throughput for sediment 228Th.This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, through the Ocean Frontier Institute. This project was supported by U.S. Geological Survey Coastal and Marine Hazards and Resources Program. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. PC acknowledges the support of the Natural Science Foundation of China (NSFC) through Grants No. 92058205