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Ice nucleation and accretion on structural surfaces are sources of major safety and operational concerns in many industries including aviation and renewable energy. Common methods for tackling these are active ones such as heating, ultrasound, and chemicals or passive ones such as surface coatings. In this study, we explored the ice adhesion properties of slippery coated substrates by measuring the shear forces required to remove a glaze ice block on the coated substrates. Among the studied nanostructured and nanoscale surfaces [i.e., a superhydrophobic coating, a fluoropolymer coating, and a polydimethylsiloxane (PDMS) chain coating], the slippery omniphobic covalently attached liquid (SOCAL) surface with its flexible polymer brushes and liquid-like structure significantly reduced the ice adhesion on both glass and silicon surfaces. Further studies of the SOCAL coating on roughened substrates also demonstrated its low ice adhesion. The reduction in ice adhesion is attributed to the flexible nature of the brush-like structures of PDMS chains, allowing ice to detach easily. HIGHLIGHTS: • Introduces several simple and reproducible techniques to reduce ice adhesion significantly on surfaces with one surface coating and identifies the coating with the lowest adhesion. • Explores the lowest-adhesion coating on surfaces with microscale and macroscale structures and finds a continued reduction in ice adhesion. • Explores qualitatively and quantitatively through surface morphology and an analytical model the results of the ice adhesion values obtained, giving justification for all such results. [ABSTRACT FROM AUTHOR]

The process of creation of a new layer of ice on the basal plane and on the prism plane of a hexagonal ice crystal is analyzed. It is demonstrated that the ordering of water molecules in the already existing crystal affects the freezing. On the basal plane, when the orientations of water molecules in the ice block are random, the arrangement of the new layer in a cubic manner is observed more frequently--approximately 1.7 times more often than in a hexagonal manner. When the water molecules in the ice block are more ordered, it results in the predominance of the oxygen atoms or the hydrogen atoms on the most outer part of the surface of the ice block. In this case, the hexagonal structure is formed more frequently when the supercooling of water exceeds 10 K. This phenomenon is explained by the influence of the oriented electric field, present as a consequence of the ordering of the dipoles of water molecules in the ice block. This field modifies the structure of solvation water (i.e., the layer of water in the immediate vicinity of the ice surface). We showed that the structure of solvation water predetermines the kind of the newly created layer of ice. This effect is temperature-dependent: when the temperature draws nearer to the melting point, the cubic structure becomes the prevailing form. The temperature at which the cubic and the hexagonal structures are formed with the same probabilities is equal to about 260 K. In the case of the prism plane, the new layer that is formed is always the hexagonal one, which is independent of the arrangement of water molecules in the ice block and is in agreement with previous literature data. For the basal plane, as well as for the prism plane, no evident dependence on the ordering of water molecules that constitute the ice block on the rate of crystallization can be observed. [ABSTRACT FROM AUTHOR]

Globally, mineral sediment supply to deltaic wetlands has generally decreased so these wetlands increasingly rely on accretion of organic matter to keep pace with relative sea‐level rise (RSLR). Because organic‐rich sediments tend to be more compressible than mineral‐dominated sediments, deltaic wetland strata are vulnerable to compaction and drowning. Using an unprecedented data set of almost 3,000 discrete bulk density and organic‐matter measurements, we examine organic‐rich facies from coastal Louisiana to quantify the thickness lost to compaction and investigate whether sediments are able to maintain sufficient volume for the associated wetlands to keep pace with RSLR. We find that organic content as well as overburden thickness and density (which together determine effective stress) strongly control sediment compaction. Most compaction occurs in the top 1–3 m and within the first 100–500 years after deposition. In settings with thick peat beds, successions up to 14 m thick have been compacted by up to ∼50%. We apply geotechnical modeling to examine the balance between elevation gained from accretion and elevation lost to compaction due to renewed sediment deposition over a 100‐year timescale. Wetlands overlying mineral‐dominated lithologies may support the weight of deposition and allow net elevation gain. Model results show that reintroduction of sediment to a representative Mississippi Delta wetland site will likely cause another ∼0.35–1.14 m of compaction but leave a net elevation gain of ∼0.01–1.75 m, depending on the sediment delivery rate and stiffness of underlying strata. Plain Language Summary: River deltas constitute some of the most valuable but also most vulnerable environments on the planet. Their elevation right above sea level is controlled by a delicate balance between sediment deposition and compaction. If sediment delivery is reduced due to dam construction in the hinterland, for example, sedimentation rates decrease. Continued sediment compaction may prevent deltas from keeping up with sea‐level rise and increase the risk of drowning. In this study, we investigate the magnitude of compaction that occurs in deltaic wetlands. We find that highly organic sediments are particularly susceptible to compaction, especially when they are buried by sand or mud. As a result, deltaic wetlands cannot rely on organic matter alone to keep pace with sea‐level rise. These findings are relevant to delta restoration efforts where sediment is reintroduced to previously isolated wetlands to combat wetland loss. For restoration to be successful, elevation gained from new sediment deposition must outpace elevation lost to compaction. The portion of the Mississippi Delta where this restoration strategy has been planned indicates potentially favorable conditions for land building, provided that sediment loads are high, and the underlying material is strong and mineral rich. Key Points: Coastal sedimentary strata under effective stresses of >10 kPa, particularly organic‐rich sediments, are likely substantially compactedA large portion of the compaction in such organic‐rich strata occurs in the top 1–3 m and the first 100–500 years after depositionThough deposition in deltaic wetlands may drive compaction, river diversions in the Mississippi Delta will likely yield net elevation gain [ABSTRACT FROM AUTHOR]

A comprehensive study on the accretion and diagenesis of the Permian–Triassic boundary microbialites is conducive to a better understanding of the ecological community after the end-Permian mass extinction. Here we studied the special microbialite sequences at the Tianba section of Leye isolated carbonate platform, South China Block. The microbialites are shown as small columnar stromatolites, stromatolitic thrombolites, spotted thrombolites, and domical digitate thrombolites in an ascending order. Thin section analyses, coupled with cathodoluminescence photos and oxygen isotopic data, reveal that all types of microbially-mediated laminae/clots are partly recrystallized. Layers of the Polybessurus-like fossils commonly occur in the recrystallized fabrics of stromatolitic laminae. However, the Polybessurus-like fossils are rare in quantity and generally fragmentary and structureless in stromatolitic clots and spotted clots. Such taphonomic features are likely interpreted as the early decomposition by heterotrophic bacteria in an oxygen-depleted microenvironment caused by rapid accumulations of organic matter in the calm water. More enrichments of 13C in the laminae of stromatolite and in the clots of stromatolitic thrombolite and spotted thrombolite than in adjacent interstitial matrixes signify the photosynthesis-dominated isotopic fractionation during the growth of microbial communities. Rare calcimicrobial structures but many calcite crystal fans were found in the 13C-depleted digitate clots. These phenomena indicate that seawater on the carbonate platform was 12C-enriched and supersaturated, accelerating carbonate precipitations and decompositions of organic matter within the microbial community. Different preservations of the Polybessurus-like fossil revealed the complicated microbially-dominated sedimentation and post-depositional diagenesis in the abnormal seawater after the catastrophe. [ABSTRACT FROM AUTHOR]

Context. The process of mass accretion in the earliest phases of star formation is still not fully understood: does the accretion rate smoothly decline with the age of the protostar or are there short, intermittent accretion bursts? The latter option would also yield the possibility for very low-luminosity objects (VeLLOs) to be precursors of solar-type stars, even though they do not seem to have sufficiently high accretion rates to reach stellar masses during their protostellar lifetime. Nevertheless, probing such intermittent events in the deeply embedded phase is not easy. Chemical signatures in the protostellar envelope can trace a past accretion burst. Aims. We aim to explore whether or not the observed C18O and N2H+ emission pattern towards the VeLLO IRAM 04191+1522 can be understood in the framework of a scenario where the emission is chemically tracing a past accretion burst. Methods. We used high-angular-resolution Plateau de Bure Interferometer (PdBI) observations of C18O and N2H+ towards IRAM 04191+1522 that were obtained as part of the CALYPSO IRAM Large Program (Continuum And Lines in Young ProtoStellar Objects). We model these observations using a chemical code with a time-dependent physical structure coupled with a radiative transfer module, where we allow for variations in the source luminosity. Results. We find that the N2H+ line emission shows a central hole, with the N2H+ emission peaking at a radius of about 10′′ (1400 au) from the source, while the C18O emission is compact (1.3′′ FWHM, corresponding to 182 au). The morphology of these two lines cannot be reproduced with a constant luminosity model based on the present-day internal luminosity (0.08 L⊙). However, the N2H+ peaks are consistent with a constant-luminosity model of 12 L⊙. Using a model with time-dependent temperature and density profiles, we show that the observed N2H+ peak emission could indeed be caused by a past accretion burst with a luminosity 150 times higher than the present-day luminosity. Such a burst should have occurred a couple of hundred years ago. Conclusions. We suggest that an accretion burst occurred in IRAM 04191+1522 in the recent past. If such bursts are common and sufficiently long in VeLLOs, they could lead to higher accretion onto the central object than their luminosity suggests. For IRAM 04191 in particular, our results yield an estimated final mass of 0.2–0.25 M⊙ by the end of the Class 0 phase, which would make this object a low-mass star rather than a brown dwarf. More generally, our analysis demonstrates that the combination of observations of N2H+ and C18O is a more reliable diagnostic of past outburst activity than C18O or N2H+ emission alone. [ABSTRACT FROM AUTHOR]

The bioavailability of DHA-bound phospholipids, especially the DHA-bound lysophospholipid (DHA-LPL) could be considered the most effective DHA chemical forms for DHA accretion in the brain. Such a DHA-LPL should also have very high emulsifying stability performance based on its analogy with conventional soy LPL. Therefore, in this study, we describe two fishery byproducts, rich in DHA-bound phospholipids, to derive DHA-LPL via sn-1 positional specific lipase partial hydrolysis of the phospholipids. Through this reaction, the DHA composition increased to 43.8% from 29.1% in the salmon head phospholipid-derived DHA-LPL, and to 84.0% from 47.4% in the squid meal phospholipid-derived DHALPL. In fact, these obtained DHA-LPLs exhibited far higher emulsifying stability than the conventional food emulsifiers in the market. For example, the prepared high-purity squid meal phospholipid-derived LPL sustained an emulsion form for a week even under 80. Thus, food emulsifiers produced from fishery byproducts are considered to exhibit very high values of both in a sense of outstandingly high health benefits and sustaining emulsions even under very high temperatures. [ABSTRACT FROM AUTHOR]

The majority of stars are part of gravitationally bound stellar systems, such as binaries. Observations of protobinary systems constrain the conditions that lead to stellar multiplicity and subsequent orbital evolution. We report high–angular resolution observations of the circumbinary disk around [BHB2007] 11, a young binary protostar system. The two protostars are embedded in circumstellar disks that have radii of 2 to 3 astronomical units and probably contain a few Jupiter masses. These systems are surrounded by a complex structure of filaments connecting to the larger circumbinary disk. We also observe accretion and radio jets associated with the protobinary system. The accretion is preferentially onto the lower-mass protostar, consistent with theoretical predictions [ABSTRACT FROM AUTHOR]

We present measurements utilizing the Filter Inlet for Gases and Aerosols (FIGAERO) applied to chamber measurements of isoprene-derived epoxydiol (IEPOX) reactive uptake to aqueous acidic particles and associated secondary organic aerosol (SOA) formation. Similar to recent field observations with the same instrument, we detect two molecular components desorbing from the IEPOX SOA in high abundance: C5H12O4 and C5H10O3. The thermal desorption signal of the former, presumably 2-methyltetrols, exhibits two distinct maxima, suggesting it arises from at least two different SOA components with significantly different effective volatilities. Isothermal evaporation experiments illustrate that the most abundant component giving rise to C5H12O4 is semi-volatile, undergoing nearly complete evaporation within 1 h while the second, less volatile component remains unperturbed and even increases in abundance. We thus confirm, using controlled laboratory studies, recent analyses of ambient SOA measurements showing that IEPOX SOA is of very low volatility and commonly measured IEPOX SOA tracers such as C5H12O4 and C5H10O3 , presumably 2-methyltetrols and C5 -alkene triols or 3-MeTHF-3,4-diols, result predominantly from thermal decomposition in the FIGAERO-CIMS. We infer that other measurement techniques using thermal desorption or prolonged heating for analysis of SOA components may also lead to reported 2-methyltetrols and C5 -alkene triols or 3-MeTHF-3,4-diol structures. We further show that IEPOX SOA volatility continues to evolve via acidity-enhanced accretion chemistry on the timescale of hours, potentially involving both 2-methyltetrols and organosulfates. [ABSTRACT FROM AUTHOR]

Accretion of the lower crust at mid‐ocean ridges is a debated topic, with modern seismic observations pointing to a complex magmatic system that includes an axial multisill system of middle‐ and lower‐crustal melt lenses and near‐ and off‐axis melt bodies. Here we revisit the hot spot‐influenced section of the western Galápagos Spreading Centre and reprocess multichannel seismic reflection data using a wide‐angle seismic tomography model. Our new images show that the magma reservoir in the lower crust at this ridge section is intruded with partially molten melt lenses. The images also show evidence for off‐axis melt lenses, magmatic‐hydrothermal interactions and Moho reflections in this region. We conclude that the similarities between the axial crustal structure of this hot spot‐influenced mid‐ocean ridge and the multisill magmatic structure imaged at the East Pacific Rise indicate that these features are common along the global mid‐ocean ridge system where seafloor spreading is dominated by magmatic accretion. Plain Language Summary: New oceanic crust forms along mid‐ocean ridges from melt extracted from the upwelling mantle. Accretion of the upper crust is well understood, but the process involved in the accretion of the lower crust is still debated. Here we present new seismic images of the crustal magmatic system of the western Galápagos Spreading Centre in the region where the influence of the Galápagos hot spot is largest and ridge magmatism is most robust. Our images show a complex magmatic system that includes lenses of partially molten rock beneath the spreading axis from the midcrust at 1.5 km and throughout the lower crust down to at least 5.4 km below the seafloor and off‐axis melt bodies. Segmentation of the axial magmatic system correlates with presence of hydrothermal features on the seafloor. This system has characteristics very similar to those recently imaged at the East Pacific Rise, indicating that these features are representative of crustal accretion at mid‐ocean ridges where seafloor spreading is dominated by magmatic processes. Key Points: Seismic images from the hot spot‐influenced section of the Galápagos spreading center reveal a multisill magmatic system in the lower crustSpatial correlation between a gap in the axial melt lens and the location of a mature, waning seafloor hydrothermal field suggests magmatic‐hydrothermal interactionsEvidence for off‐axis melt lenses emplaced at the edges of the axial low velocity zone, and weak Moho reflections on the across ridge axis seismic profile, which disappear in the axial zone [ABSTRACT FROM AUTHOR]

Highlights • A SHP surface with nanorods structure was fabricated by RF magnetron sputtering. • The as-prepared SHP aluminum surface exhibits excellent anti-icing property in glaze ice. • Frost formation was delayed for over 210 min at −5 °C and −10 °C. • Impacting cooled water droplets can be completely repelled. • The as-prepared SHP surface can reduce the critical diameter of water droplets. Abstract Ice accumulation on power transmission lines has been a vital problem for power systems in cold regions. In this paper, the anti-icing property of the as-prepared superhydrophobic (SHP) surface on the aluminum substrate in glaze ice was studied in an artificial climate chamber. Results show that the as-prepared SHP surface demonstrates excellent anti-icing property with only 24.65% of the entire surface froze after spraying for 60 min. The nano-scale structures and the HDTMS molecule both contributed to the superhydrophobicity. The reason for the excellent anti-icing property of the as-prepared SHP surface can be ascribed to two reasons: on the one hand, the nanoscale structures can effectively help maintain the superhydrophobicity of the as-prepared SHP surface at low temperatures, which inhibited the frosting process for over 210 min at −5°C and −10 °C. On the other hand, the as-prepared SHP surface can completely repel the impacting millimeter-level cooled water droplets or reducing the critical diameter of micro-scale droplets in glaze ice leading to a reduction of ice accumulation. The nanostructured ZnO textures significantly helped improve the ability to resist frost and ice accumulation on the aluminum surface, which has a good prospect on power transmission lines against ice formation. [ABSTRACT FROM AUTHOR]

Abstract There have been lots of debates regarding tectonic evolution of sedimentary basins in the North China block during the early Mesozoic. It has been widely held that the North China block was strongly affected by the collision of the North and South China blocks on the south and the terrane accretion on the north, and thus early Mesozoic basins of various scales in the interior and peripheries of the North China block resulted from crustal shortening. Based on extensive and detailed field investigations of stratigraphic sequences, sedimentary processes and basin tectonics, this study shows that the North China block manifested itself in general as a stable domain during the early Mesozoic, with rifting, transcurrent faulting and magmatism occurring mainly in peripheral regions. The North China block behaved as a big intracratonic basin in the Triassic albeit its depositional area shifted to the west in Mid–Late Triassic time. The westward migration of depocenter is assumed the consequence of uplifting of the eastern part of the North China block in response to the collision of the North and South China blocks along the Tongbai–Dabie–Sulu orogenic belt and coeval transpression of the Tanlu fault zone. Sedimentary basins had not developed until the Early Jurassic in the regions north of the Tongbai–Dabie orogen, and plausibly formed as the result of crustal stretching related to southeastward exhumation of the Dabie high-pressure metamorphic rocks. The collision of the North and South China blocks led to south-directed displacement of the East Qinling orogen, but few geological records exist indicative of Mid–Late Triassic thrusting in the southern margin of the western North China block. Instead, some evidence is suggestive of extensional or transtensional deformations, such as the existence of large normal faults controlling subsidence and sedimentation of Middle–Late Triassic basins and the presence of synsedimentary normal faults in basin sequences. Both the East and West Qinling experienced rapid uplifting in the Late Triassic, coeval with large-volume granitic magmatism. Late Triassic uplift and exhumation of the Qinling was considered as the result of asthenospheric upwelling and voluminous granitic injections. Vertical motion of the northern East Qinling might have triggered normal faulting along its northern edge and extensional subsidence of the southern margin of the western North China block. Broad denudation occurred simultaneously in the northern margin of the North China block from the Late Triassic to Early Jurassic in association with magmatism and development of a few small rift basins. Asthenospheric uprising is regarded as the cause for Late Triassic magmatism, regional surface uplift and supracrustal stretching. Triassic subsidence and sedimentation in the interior of the North China block was punctuated by crustal uplifting, possibly driven by mantle upwelling at the transition from the Triassic to Jurassic. The whole North China block then resumed low-rate subsidence from the late Early Jurassic and plausibly developed into a broad intracratonic basin in the Middle Jurassic, characterized by widespread distribution of shallow-water lacustrine and meandering river facies associations. The sagging of the whole North China block is thought of as the consequence of thermal contraction in the aftermath of mantle upwelling. Backarc extension related to the Paleo-Pacific plate subduction might have magnified subsidence of the eastern North China block, resulting in relatively thick accumulation of Middle Jurassic strata. This study restores tectonic and sedimentary history of the early Mesozoic basins in different portions of the North China block and advances models to illustrate how the basins of diverse origin were generated and filled in different stages. [ABSTRACT FROM AUTHOR]

Abstract The incremental accumulation of geochronological data from the Margate Terrane over the past two decades has progressively revealed a tectono-magmatic history of lengthening duration and greater complexity. The Margate Terrane is the southernmost of three Proterozoic island arc terranes that accreted against the southern margin of the Kaapvaal Craton which together form the Natal metamorphic belt. Early geochronological data suggested that the Margate Terrane was the youngest of the three terranes. Moreover, age bracketing of deformational fabrics indicated that the Margate Terrane was still tectonically active at ∼1040 Ma, some 90 Ma after the northernmost Tugela Terrane had been obducted onto the Kaapvaal Craton (∼1155 Ma) and had stabilised. More recent U-Pb zircon data show that the magmatic development of the Margate Terrane goes back as far as ∼1180 Ma, indicating that its protolith crust is not much younger than that of the Tugela or Mzumbe terranes. Nevertheless, age bracketing of tectonic fabrics indicates that there were two nearly coaxial tectonic events that affected the Margate and Mzumbe terranes, but not the Tugela Terrane which is thought to have escaped these events, having been shielded from them by the underlying rigid southern margin of the Kaapvaal Craton. Geochronology has revealed a marked southward younging of the earliest D 1 event across the belt, manifested as southerly-dipping fabrics and associated with initiation of terrane accretion across the belt: D 1 TUGELA = ∼1200 Ma; D 1 MZUMBE = ∼1150 Ma and D 1 MARGATE = ∼1090 Ma. The youngest plutons and tectonic fabrics in the Margate and Mzumbe Terranes (∼1030–1040 Ma) are interpreted in terms of oblique collisional tectonics associated with the assembly of Rodinia. The geochronological data support correlation with events and lithologies in the Bushmanland Subprovince of the Namaqua metamorphic belt and the Vardeklettane Terrane of the Maud belt in westernmost Dronning Maud Land, East Antarctica. Highlights • Margate Terrane geochronological data reveal four magmatic events. • Diachronous terrane docking and arc accretion occurred between 1170 Ma and 1040 Ma. • Events are penecontemporaneous with similar ones in the Namaqua and Maud belts. • Data suggest juxtapositioning of the Margate Terrane and Llano Belt at ∼1040 Ma. [ABSTRACT FROM AUTHOR]

Abstract Sand spits occur around the world with different shapes, dimensions and dynamics. While usually considered non-developable coastal features, development has taken place in several locations around the world, and because spits are often very dynamic, a better understanding of their behaviour and evolution is useful. Understanding their stability and morphological cycles can be used as a measure of the health of nearby beaches. The inter-annual and decadal morphological evolution of the beach spit at Tortugueros, on the Yucatan peninsula, Mexico, a re-entrant bay on the Isla del Carmen barrier system, is examined. Digitized information from satellite images and aerial photographs, covering a 31 year period, was used to compare the shoreline evolution with numerical results. The method used consists of the estimation of the wave breaking conditions and the evaluation of the cross and longshore energy flux. The time-averaged wave energy flux allows the estimation of the evolution of those morphological features. The shoreline changes are very dramatic, with rates of accretion up to 160 m yr-1 and erosion up to 196 m yr-1. The results of the comparative analysis show that Tortugueros beach is a resilient system in dynamic equilibrium, governed by the combination of the short period local marine climate of the area and large-scale weather cycles related to the El Niño and La Niña phenomena. The analysis presented in this paper is valid to describe the functioning and resilience of dynamic beach systems elsewhere, where the wave climate is known, based on the wave energy flux of the breaking waves. Highlights • Satellite images were used to analyse the shoreline evolution of a complex barrier spit. • Breaking wave energy flux data defined the drivers of the specific coastal dynamics. • The cycles of spit growth and breaching were observed on a seasonal basis. • A predominant oblique orientation of the total wave energy flux was observed. • The highly dynamic position and morphology of the barrier spit was analysed. [ABSTRACT FROM AUTHOR]

We improved the algorithm presented in Rubie et al. (2015) to model the chemical evolution of Earth driven by iron/silicate differentiation during the planet's accretion. The pressure at which the equilibration occurs during a giant impact is no longer a free parameter but is determined by the smooth particle hydrodynamic (SPH) simulations of Nakajima et al. (2021). Moreover, impacting planetesimals are now assumed to be too small to cause melting and differentiation and thus their materials are stored in the crystalline upper mantle of the growing planet until a hydrostatically relaxed global magma ocean forms in the aftermath of a giant impact, whose depth is also estimated from Nakajima et al. (2021). With these changes, not all dynamical simulations lead to a satisfactory reproduction of the chemical composition of the bulk silicate Earth (BSE). Thus, the latter becomes diagnostic of the success of dynamical models. In the successful cases also the BSE abundances of W and Mo can be reproduced, that were previously hard to fit (Jennings et al., 2021). • Use scaling laws to quantify the properties of magma oceans produced from impacts. • Equilibration depth during accretion affects the chemistry of the resulting mantle. • A chemically consistent Earth mantle is not the result of all N-body simulations. • Model mantle W and Mo concentrations more closely fit the Earth. • Iron-sulphide exsolution still required for fitting highly siderophile elements. [ABSTRACT FROM AUTHOR]

Abstract The geological evolution of the Early Paleozoic Wuyi-Yunkai orogen in South China is a scientific question of a long-standing debate. We document the presence of a NE-NEE-striking Early Paleozoic subduction-accretion shear zone, a possible mélange belt, in the northwestern Yunkai Domain. The northwestern Yunkai shear zone consists predominantly of tectonically juxtaposed fragments of Early Paleozoic flysch, arc volcanic rocks, and a forearc ophiolite. The Yunkai shear zone displays typical mélange structures in several locations; however, these structures are not continuous throughout the shear zone. The shear zone provides evidence for greenschist to amphibolite facies metamorphism and intense deformation resulting from Early Paleozoic to Early Mesozoic tectonic events. The flysch fragments are characterized by northwestward younging, northwestward thrusting, and northwestward migration of deformation and metamorphism. The arc volcanic rocks consist of basaltic-andesite, andesite, and dacite with a mainly sanukitic composition and also include Nb-enriched basalts. They are characterized by enrichment of LREEs, LILEs, Pb and depletion of HFSEs, suggesting a continental forearc or a continental arc tectonic setting. The ophiolitic fragments consist of MORB-like basalt and dolerite/gabbro. They have slightly depleted to flat LREE patterns and are characterized by enrichment of LILEs and Pb and depletion of HFSEs, indicating a continental forearc setting. Zircon U-Pb analyses yield 460–443 Ma and 455–437 Ma ages for the sanukitic volcanic rocks and ophiolitic fragments, respectively, suggesting that they formed in the Late Ordovician to Early Silurian. Both the sanukitic volcanic rocks and ophiolitic fragments possess negative to positive zircon ε Hf (t) values (−11.0 to +2.3), indicating that they may have been generated by partial melting of an old subarc mantle wedge source metasomatized by slab-derived fluids and/or melts. Recognition of the Early Paleozoic subduction-related magmatism and subduction-accretion structures in the northwestern Yunkai Domain has important implications for the tectonic history of the Wuyi-Yunkai orogen, South China. Collectively, combined with previous studies, we propose that the Huanan oceanic lithosphere began to subduct southeastward beneath the Yunkai terrane (arc) as early as 460 Ma, and the subduction continued between 460 and 440 Ma. Highlights • The northwestern Yunkai shear zone comprises fragments of flysch, arc volcanic rocks and a forearc ophiolite. • The arc volcanic rocks include sanukites (460–443 Ma) and Nb-enriched basalts (455 Ma). • Yunkai forearc ophiolite consist of MORB-like basalt, dolerite/gabbro (455–437 Ma). • An Early Paleozoic subduction-accretion model is proposed for the Yunkai Domain. [ABSTRACT FROM AUTHOR]

We study the differences in X-ray properties of luminous radio galaxies and their radio-quiet counterparts. In order to avoid biases associated with the dependence of X-ray properties on the black hole mass and Eddington ratio, the radio-loud and radio-quiet objects are selected to cover similar ranges of these parameters. Our studies are based on the X-ray data from the Swift /BAT catalog. We confirm previous results that radio galaxies are on average X-ray-louder than radio-quiet AGNs, but find that their spectral slopes are very similar. This suggests that in radio-loud and radio-quiet AGNs the hard X-rays are produced in the same region and by the same mechanism. We argue that this region can be associated with the hot, geometrically thick, central portion of the accretion flow, where production of hard X-rays is likely to be dominated by Comptonization of the optical/UV radiation of the truncated 'cold' accretion disc by hot electrons. The larger X-ray luminosities in radio-loud AGNs may result from larger radiative efficiencies of the innermost portions of the accretion flows around faster rotating black holes. [ABSTRACT FROM AUTHOR]

Highlights • This paper is focused on ice crystal icing (ICI) which is related to ice accretion for an aircraft in flight in the presence of ice particles. • Emphasis is put on the glaciated conditions where the required liquid water comes from the melting of the ice crystals themselves when they enter a warm environment. • A semi-empirical model is proposed. • The model is able to predict typical conical accretion shapes that are never found in classical supercooled water icing conditions. • The influence of the ice crystal melting ratio on the accretion shapes is properly accounted for. Abstract Icing has been identified as a major hazard for aviation safety since the beginning of aeronautical engineering. This paper is focused on ice crystal icing (ICI) which is related to ice accretion for an aircraft in flight in the presence of ice particles. Liquid water is necessary for the ice crystals to stick to the walls of the internal components of an aircraft engine. Emphasis is put on the glaciated conditions where the required liquid water comes from the melting of the ice crystals themselves when they enter a warm environment (the engine core). ICI represents an important concern for flight safety in addition to classical supercooled water icing where the accreted ice only derives from the instantaneous freezing of supercooled liquid droplets when they hit an obstacle. A semi-empirical model which accounts for the influence of the ice crystals on the mass and momentum balance equations is proposed. It accounts for the liquid transport in the porous ice layer and for the ice crystal sticking efficiency. The physics is extremely complicated and not completely understood. Therefore, several adjustable parameters are used in the model. However, the model predictions agree well with the existing experimental data. In particular, the model is able to predict typical conical accretion shapes that are never found in classical supercooled water icing conditions. Moreover, the influence of the ice crystal melting ratio on the accretion shapes is properly accounted for. [ABSTRACT FROM AUTHOR]

Abstract The vast majority of additive manufacturing methods rely on an ultra-serialized approach for building parts. Often described as "layer-by-layer," in reality, these are hierarchically serial, point-by-point, path-by-path and layer-by-layer approaches. The multi-scale stratification of mass and accompanying complex thermal histories introduced by thermally-based hierarchical processes such as selective laser melting (SLM), fused deposition modeling (FDM), and direct metal laser deposition (DMLS), give rise to a number of limitations in terms of build times with respect to part size and scale, as well as structural performance due to process-induced inhomogeneities. This work proposes a new methodology that has the potential for addressing these drawbacks by implementing a truly volumetric approach to additive manufacturing of fiber-reinforced-like composite objects. That is, instead of building parts a single point at a time in a hierarchical manner, by spatially controlling the energy distribution within a three-dimensional build domain, one can build parts from large constituent volumes, in parallel, by addressable, resistive heating. The work presented herein consists of a theoretical treatment of the underlying physics, process planning via the solution of an inverse problem for implementing the proper control, and, finally, a preliminary demonstration of the process. Highlights • Accretive, volumetric additive manufacturing (AM) enables significant reduction in build time and build time scaling (L3 → L). • Enabled by three-dimensional control of temperature distribution of build volume via addressable resistive wire array. • Process results in mechanically-stabilized composite material response. • Process requires no moving parts to operate (completely "solid-state"). • Process allows for in-situ postprocessing. [ABSTRACT FROM AUTHOR]

Abstract This contribution is a synthesis of studies carried out since 2004 in the Makran accretionary wedge exposed in SE Iran. These studies were intended to improve our understanding of the behaviour of accretionary wedges and of the significance of the Makran wedge in the frame of Tethys tectonics. Reassessing the stratigraphy and structure of the Iranian Makran has allowed distinguishing four main litho-tectonic units. The lithological content of these four units is briefly described to discuss the sedimentary environments, which record the general filling of an oceanic basin with clastic sediments derived from the north. The petrology of ophiolites, exposed in the backstop region to the north of the accretionary wedge itself, demonstrates the existence of an oceanic basin formed in the Jurassic-Late Cretaceous to the north of continental slivers, which had separated from Central Iran. There is petrological evidence for a subduction-related magmatic arc during the Late Cretaceous, which sourced much of the clastic material in the Cretaceous-Lower Miocene turbidites present throughout the wedge. The literature survey shows that the Late Cretaceous to Present evolution of the Pakistan part of the Makran fold-and-trust belt is in its major attributes similar to that of the Iranian Makran. These observations and results are discussed in a tectonic model that integrates knowledge on the Oman Mountains, on the other side of the current Oman subduction. [ABSTRACT FROM AUTHOR]

Highlights • Zircons from the Baifen lamproites in the southern Yangtze Block are used as probes of the deep crust. • The youngest zircon age of 253 Ma is interpreted as eruption time of the Baifen lamproites. • Crustal components as old as ca 3.45 Ga may exist beneath the southern Yangtze Block. • Zircon xenocrysts also record crustal growth at 2.2–2.1 Ga and 2.0–1.8 Ga in the southern Yangtze Block. Abstract Integrated U–Pb dating and Hf-isotope analysis of zircon xenocrysts from the Baifen lamproites of the Zhenyuan area in the southeastern Guizhou Province offer a unique glimpse into the evolution of the deep continental crust beneath the southern part of the Yangtze Block, South China. A total of 148 zircons with 90–110% concordance yield U–Pb ages varying from 3458 ± 9 Ma to 252 ± 2 Ma. They generally have high Th/U ratios (>0.3), indicating a magmatic origin. The two youngest magmatic zircons give a weighted mean 206Pb/238U age of 253.0 ± 2.8 Ma, which is interpreted as the emplacement age of the host Baifen lamproites. Most zircons with pre-eruption ages are xenocrysts derived from the deeper crust of the southern Yangtze Block. They define two major Paleoproterozoic age populations at 2.17 Ga and 1.8 Ga, with similar Hf model ages (T crust) of 2.4–2.8 Ga (peak at 2.64 Ga). The oldest zircon has a 207Pb/206Pb age of 3458 ± 9 Ma with ε Hf (t) = +1.47 and T crust = 3.7 Ga. This demonstrates the presence of Archean crustal components (or remnants) as old as 3.7 Ga beneath the southern Yangtze Block. Magmatic events involving significant addition of juvenile mantle-derived materials mainly occurred at 2.2–2.1 Ga and 2.0–1.8 Ga, but the latter event also involved reworking of the Neoarchean crust and might represent the cratonization of the Yangtze continent during the middle Paleoproterozoic, which could be correlated to the assembly of the Columbia supercontinent. This segment of the Yangtze Block became tectonically quiescent until 1.2 Ga, implying that the crustal stabilization lasted for ca 600 million years. A few late Mesoproterozoic zircon xenocrysts within the age range 1.3–1.0 Ga suggest the occurrence of Grenville-aged events. These Neoproterozoic zircon xenocrysts (992–547 Ma) have a wide range of ε Hf (t) values (+8.47 to −22.07), consistent with the zircon Hf isotopic compositions of widespread coeval igneous rocks in the Yangtze Block. The data show that the Yangtze Block has undergone important crustal growth and reworking during the Neoproterozoic in response to the breakup of the Rodinia supercontinent. The early–middle Paleozoic zircon xenocrysts (513–357 Ma) have negative ε Hf (t) values (−2.97 to −12.69) and T crust Hf model ages of 1.59–2.27 Ga, indicating reworking of the Precambrian crustal basement without juvenile contributions during the Caledonian orogeny. The positive ε Hf (t) values (+13.79 to +0.22) of twelve late Paleozoic zircons (284–264 Ma), with a major age peak at ca 275 Ma, suggest that the Precambrian basement beneath the southern Yangtze Block experienced an episode of strong rejuvenation during the Permian. We propose a possible linkage between the Baifen lamproite magmatism (284–252 Ma) and the Emeishan flood-basalt volcanism. [ABSTRACT FROM AUTHOR]

Reef islands of the Xisha Islands, South China Sea, were formed during the mid–late Holocene. However, the vertical accretion of ornithogenic sediments of the islands is not well understood owing to a lack of precise dating. Here we present an analysis of seven of the Xisha Islands, and reconstruct their accumulation history based on radiocarbon analysis of seabird subfossils. From Clam‐based age–depth models, a universal development mode of the Xisha Islands is hypothesized. The mean accumulation rate of guano sediments on the Xisha Islands in the late Holocene was 1.02 ± 0.42 mm a−1. The sum of the deposition rate of coral sands and the rate of ornithogenic accumulation is lower than or close to the current rate of sea level rise in the Xisha Islands, implying a potential threat to the islands' safety. This study also provides robust evidence for a sequence of island development associated with seabirds. [ABSTRACT FROM AUTHOR]

The amount of atmospheric gas absorbed into a planetary interior during formation depends on the temperature, pressure, composition, and dynamics of its atmosphere, along with the planet mass, its composition, rate of accretion, and the average age of its surface. We develop a boundary layer model for terrestrial planet ingassing during accretion that quantifies the amounts of hydrogen and helium dissolved into a global magma ocean from a hot, gravitationally captured nebular atmosphere in the first few million years of solar system history. Assuming that most of Earth's accretion occurred within the lifetime of its nebular atmosphere, one or more ocean masses of ingassed hydrogen are predicted if the surface pressure is high and the magma surface is young. In addition, Earth would have acquired hundreds of petagrams of helium-3 from the same nebular atmosphere. Our model predicts negligible hydrogen ingassing from a gravitationally captured nebular atmosphere on Mars, but shows that vast amounts of hydrogen ingassing – tens of ocean masses – are possible during the accretion of Super-Earth-sized terrestrial planets. [ABSTRACT FROM AUTHOR]

Understanding the relationships between and among chondritic components of various chondrite groups is of prime importance for deciphering the dynamics of material transport and planetary accretion in the early Solar System. Here we obtain insights into these processes and the reservoirs present by investigating the nucleosynthetic Ti isotopic signatures of individual Ca,Al-rich inclusions (CAIs) and Na–Al-rich chondrules from ordinary and CO chondrites. This specific type of chondrule is of interest as it is thought to have incorporated refractory, CAI-like material as precursors. Our data show that CAIs from ordinary and CO chondrites exhibit 50 Ti excesses that are indistinguishable from CV CAIs, and thus indicate a common source reservoir for refractory inclusions in ordinary, CO, and CV chondrites. Na–Al-rich chondrules from CO chondrites also show 50 Ti excesses, indicating the presence of CAIs from this reservoir in the precursor materials of CO chondrules. In contrast, Na–Al-rich chondrules from ordinary chondrites show no 50 Ti excesses and are indistinguishable from the bulk values for ordinary chondrites. Thus, known CAIs cannot have been the refractory precursor of the Na–Al-rich chondrules in ordinary chondrites. Consequently, within the accretion region of the ordinary chondrites, two different types of refractory components must have existed: (1) a 50 Ti-enriched refractory component that is present as CAIs and either arrived at the accretion region of the ordinary chondrites after chondrule formation, or was only present in insignificant amounts, and (2) another type of refractory material without a 50 Ti excess, which was involved as precursor in the chondrule formation process. Our data thus imply that refractory components with condensation signatures must have formed in at least two isotopically distinct nebular regions. These may be related to non-carbonaceous and carbonaceous source regions, that is, the inner and outer Solar System, divided by the early formation of Jupiter. [ABSTRACT FROM AUTHOR]

The volatile siderophile elements are important tracers of the delivery of volatile elements to the Earth. Their concentrations in the bulk silicate Earth are a function of the relative timing of their accretion and their sequestration into the core: a comprehensive understanding of their metal-silicate partitioning behaviour is therefore required in order to infer the volatile element accretion history. We present new partitioning data between liquid metal and liquid silicate at 11 GPa for a suite of volatile siderophile elements: Ag, As, Au, Cu, Ge, P, Pb, Sb, Sn. We focus particularly on determining their valence states and the effects of Si on partitioning, which are required in order to extrapolate from experimental conditions to core-formation conditions. It was found that all elements have weak to strong positive interaction parameters with Si. At low f O 2 , redox equilibria dictate that the siderophile elements should become more siderophile. However, at low f O 2 , Si also partitions more strongly into the metal. Given the repulsive nature of the interaction between Si and the elements of interest, the increased Si concentration at low f O 2 will counteract the expected increase in the partition coefficient, making these elements less siderophile than expected at very reducing conditions. This causes the linear relationship between f O 2 and log( D ) to become non-linear at low f O 2 , which we account for by fitting an interaction parameter between Si and the elements of interest. This has implications for the interpretation of experimental results, because the valence cannot be determined from the slope of log( D ) vs. log f O 2 if low f O 2 , high Si metal compositions are employed without applying an activity correction. This also has implications for the extrapolation of experimental partitioning data to core-formation conditions: reducing conditions in the early stages of core formation do not necessarily result in complete or even strong depletion of siderophile elements when Si is present as a light element in the core-forming metal phase. [ABSTRACT FROM AUTHOR]

Abstract: Herein, it is reported an on‐the‐fly accretion/reaction protocol to evaluate the structure‐performance relationship in the chemoselective flow citral hydrogenation over Ni‐based catalysts. Based on the methodology one was able to determine Ni nanoparticles ideal average size (ca. 9 nm), in a rapid and facile manner. The methodology offers a simple workflow, cost‐effective and adaptable strategy for process intensification and optimization. [ABSTRACT FROM AUTHOR]

Highlights • Yellow River sediment delivery has decreased over 99% under the human interference. • Significant reduction of Yellow River sediment input occurred in 1985. • The new regime of riverine delivery shapes deltaic morphology at multiple timescales. • Approximately 68% of sediment input deposited near the active Yellow River mouth. • Active Yellow River mouth is transforming from the accretion to erosion state. Abstract The Yellow River subaqueous delta (YRSD), once the most rapid depo-center among river deltas worldwide, has been under the risks of subsidence and degradation due to the new regime of riverine delivery affected by human interventions. Utilizing hydrologic and bathymetric surveying datasets, we examined the latest regime of river input from the perspective of water-sediment relationship, and the responding morphological evolutionary processes of active YRSD over a period of 20 years between 1996 and 2016. Results show that the new discharge regime is strongly interfered by the Water-Sediment Regulation Scheme (WSRS), characterized by a more drastic decline of sediment load than that of water discharge; more harmonious relationship between water and sediment discharges in the lower reach of the river to the sea; coarser sediment delivery and low suspended sediment concentration (SSC). We identified inverse erosion-accretion trends in the subaqueous region: net accretion of 0.15 m/yr in the active Yellow River mouth (AYRM) and severe erosion of −0.1 m/yr in the Gudong littoral zone (GDLZ). As the primary sink for sediment delivery, AYRM received approximately 68% of sediment delivery during the study period and sedimentation was mainly occurred in the shallower area where water depth was less than 10 m. In addition, recent morphological evolution of AYRM is found to have undergone through four stages, namely: moderate accretion (1996–2002), rapid accretion (2002–2007), reduced accretion (2007–2015) and rapid erosion (2015–2016). The new regime of riverine delivery presents multiple spatiotemporal scales in shaping deltaic morphology. Compared with the previous research, we present the morphological evolution of deltaic system over decadal timescale is strongly influenced by reduction of sediment supply derived from basin-scale human impacts, and the variability of subaqueous portion during the study period is closely related to inter-annual variability of river input. Besides, the building of AYRM is shaped by event-scale WSRS induced-floodwater, and decade-scale change of sediment pathway governed by frequent mouth channel migration. The results show, for the first time, that AYRM has experienced a significant erosion since the implementation of WSRS, with a decline of 99% sediment delivery in 2016 compared to the natural mode during 1950s. The results also indicate that to maintain the erosion-accretion balance of AYRM, an estimation of 41.4–62.3 Mt/yr sediment delivery should be kept. Due to the fluvial regime change from the natural to the highly human-regulated modes, the AYRM, as well as the whole YRSD, is expected to be transforming from the accretion to erosion states. [ABSTRACT FROM AUTHOR]

Suspended sediment concentration (SSC) has a significant impact on the estuarine environment and its morphological evolution. At any given location, the temporal variability of depth-averaged SSC is due to a combination of two processes: horizontal advection and local resuspension. In this study, we investigated the sediment dynamics at three anchored monitoring stations close to the maximum turbidity zone of the Changjiang Estuary, and developed a box model to differentiate the effects of advection and resuspension. Further, settling velocities were estimated using the ADV Reynolds flux method, excluding the advection SSC component. We found that predicted changes in advection- and resuspension-induced SSCs were consistent with the bottom shear stress and accretion/erosion observations. The combination of observed bed accretion/erosion changes and the predicted advection-induced SSCs indicates that the advective transport of suspended sediment is an important process in accelerating persistent erosion at the monitoring stations. Although SSC variations due to advection and resuspension are of similar magnitudes, our model results indicate that if resuspension dominates, the resuspension-induced component can reach up to twice the magnitude of the advection-induced component. We conclude that the box model is a valuable tool for evaluating subaqueous delta accretion/erosion in response to sediment reduction caused by upstream dam construction and climate change. [ABSTRACT FROM AUTHOR]

Diego de Almagro Island was formed by the subduction and accretion of several seafloor-derived tectonic slices with very heterogeneous ages and pressure-temperature-time (P-T-t) paths. The highest element of the pile (the Lazaro unit) evidences subduction in the high-P granulite field (~1.3 GPa, 750 °C) at ca. 163 Ma. Below it, a thin tectonic sliver (the Garnet Amphibolite unit) preserves eclogitefacies remnants (~570 °C and ~1.7 GPa) formed at ca. 131 Ma (in situ U-Pb zircon rim ages). Peak assemblages were nearly fully amphibolitized during decompression down to ~1.2 GPa and ~600 °C at 125-120 Ma (Rb-Sr multimineral dating). The underlying Blueschist unit has ~50 m.y. younger metamorphic ages and exhibits slightly cooler peak burial conditions (~520 °C, 1.7 GPa; ca. 80 Ma, in situ white mica Ar-Ar ages and multimineral Rb-Sr dating) and is devoid of amphibolitization. The mylonites from the sinistral strike-slip Seno Arcabuz shear zone bounding Diego de Almagro Island to the east also exhibit amphibolite-facies (~620 °C and ~0.9 GPa) deformation at ca. 117 Ma (multimineral Rb-Sr ages). In situ white mica Ar-Ar dating and multimineral Rb-Sr dating of low-T mylonites (~450 °C) along the base of the Lazaro unit reveal partial resetting of high-T assemblages during tectonic displacement between 115 and 72 Ma and exhumation of the slice stack. Detrital zircon U-Th-Pb ages indicate that the material accreted on Diego de Almagro Island has been mostly recycled from a Permian-Triassic accretionary wedge (Madre de Dios accretionary complex) exposed along the subduction buttress. Geological and geochronological constraints suggest that the rocks of the Seno Arcabuz shear zone and the Lazaro unit were tectonically eroded from the buttress, while the underlying Garnet Amphibolite and Blueschist units instead derive from the subducted oceanic basin, with increasingly younger maximum depositional ages. The very long residence time of the rocks (~90 m.y. for the Lazaro unit) along the hanging wall of the subduction interface recorded long-term cooling along the Patagonian subduction zone during the Mesozoic. Diego de Almagro Island therefore represents a unique window onto long-term tectonic processes such as subduction interface down-stepping, tectonic erosion, and episodic underplating near the base of an accretionary wedge (40-50 km). [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to compare the plasma exposure and tissue accretion of docosahexaenoic acid (DHA) in response to oral dosing of free carboxylic acid (OM3CA) and ethyl ester (OM3EE) forms. Materials and methods: Sixteen adult male Wistar rats, fed a low-fat, carbohydrate-rich, standard chow diet, were chronically catheterized and gavaged for 5 consecutive days with either OM3CA (n = 9) or OM3EE (n = 7), the last day fasted overnight and spiked respectively with either 14C-DHA or 14C-DHA-ethyl ester (14C-DHA-EE) tracers. Appearance of 14C-labelled plasma polar and neutral lipids over 4 h and retention of 14C-activity (R) in the tissues at 4 h were measured. Results: Compared to OM3EE, OM3CA resulted in 2- and 3-fold higher areas under the plasma 14C-labelled polar and neutral lipid curves (exposures), respectively, as well as, higher R in all tissues examined. For both OM3CA and OM3EE, R varied in a tissue specific manner; highest in liver, followed by red skeletal muscle, adipose tissue, brain and white skeletal muscle. Multiple linear regression analysis revealed that R in each tissue (except liver) was dependent on polar lipid exposure alone (r2>0.87 and P<0.001), but not neutral lipid exposure, and furthermore this dependence was indistinguishable for OM3CA and OM3EE. In the liver, R was found to be dependent on both polar and neutral lipid exposures (r2 = 0.97, P<0.001), with relative contributions of 85±2% and 15±2%, respectively. As for the other tissues, these dependencies were indistinguishable for OM3CA and OM3EE. Conclusion: The present results, in fasted low-fat diet fed rats, are consistent with higher oral bioavailability of OM3CA versus OM3EE forms of DHA. Once DHA has entered the circulation, the tissue distribution is independent of the dosed form and uptake in the skeletal muscle, fat and brain is driven by the polar pools of DHA in plasma, while DHA accretion in liver is supplied by both polar and neutral plasma lipids. [ABSTRACT FROM AUTHOR]

A new three-dimensional mathematical model is proposed to predict the shape of accreted ice on helicopter rotors. The model assumes that ice accretion on a rotor’s surface occurs by flow and solidification of a thin water film on its surface. The model is developed by analyzing conservation of mass, momentum, and energy in the thin water film on a rotating curved surface. The model is expressed in rotating body-fitted nonorthogonal curvilinear coordinates, and the Coriolis-force term in the momentum equations is neglected because its effect is relatively small compared with that of the centrifugal force. The computational method is presented to solve the model, and the model is validated by comparing its results with published experimental data. The results show that the proposed model accurately predicts both the water-film thickness and the ice-layer thickness on a rotating surface. Additionally, the model has been used to study how the rotor angular speed and MVD (Median Volumetric Diameter) of the droplets affect ice accretion. The results show that an increase in both angular speed and MVD can lead to a thicker layer of ice, while the effect of MVD on ice accretion near the stagnation point becomes unobvious when MVD is larger enough. [ABSTRACT FROM AUTHOR]

Earth’s core contains ∼10% of a light element that may be a combination of Si, S, C, O or H, with Si potentially being the major light element. Metal-silicate partitioning of siderophile elements can place important constraints on the P-T-fO 2 and composition of the early Earth, but the effect of Si alloyed in Fe liquids is unknown for many of these elements. In particular, the effect of Si on the partitioning of highly siderophile elements (Au, Re and PGE) is virtually unknown. To address this gap in understanding, we have undertaken a systematic study of the highly siderophile elements Au, Pd, and Pt, and the volatile siderophile elements P, Ga, Cu, Zn, and Pb at variable Si content of metal, and 1600 °C and 1 GPa. From our experiments we derive epsilon interaction parameters between these elements and Si in Fe metallic liquids. The new parameters are used to update an activity model for trace siderophile elements in Fe alloys; Si causes large variation in the magnitude of activity coefficients of these elements in FeSi liquids. Because the interaction parameters are all positive, Si causes a decrease in their metal/silicate partition coefficients. We combine these new activity results with experimental studies of Au, Pd, Pt, P, Ga, Cu, Zn and Pb, to derive predictive expressions for metal/silicate partition coefficients which can then be applied to Earth. The expressions are applied to two scenarios for continuous accretion of Earth; specifically for constant and increasing fO 2 during accretion. The results indicate that mantle concentrations of P, Ga, Cu, Zn, and Pb can be explained by metal-silicate equilibrium during accretion of the Earth where Earth’s early magma ocean deepens to pressures of 40–60 GPa. Au, Pd, and Pt, on the other hand become too high in the mantle in such a scenario, and require a later removal mechanism, rather than an addition as traditionally argued. A late reduction event that removes 0.5% metal from a shallow magma ocean can lower the Au, Pd, and Pt contents to values near the current day BSE. On the other hand, removal of 0.2–1.0% of a late sulfide-rich matte to the core would lower the Au, Pd, and Pt concentrations in the mantle, but not to chondritic relative concentrations observed in the BSE. If sulfide matte is called upon to remove HSEs, they must be later added via a late veneer to re-establish the high and chondritic relative PUM concentrations. These results suggest that although accretion and core formation (involving a Si, S, and C-bearing metallic liquid) were the primary processes establishing many of Earth’s mantle volatile elements and HSE, a secondary removal process is required to establish HSEs at their current and near-chondritic relative BSE levels. Mn and P - two siderophile elements that are central to biochemical processes (photosynthesis and triphosphates, respectively) - have significant and opposite interactions with FeSi liquids, and their mantle concentrations would be notably different if Earth had a Si-free core. [ABSTRACT FROM AUTHOR]

Abstract: Submarine groundwater discharge (SGD) is an important source of nutrients to many coastal reefs, yet there is little information on how SGD impacts key coral reef processes. Here, we investigated the effect of SGD on coral growth and bioerosion rates from Porites lobata nubbins and blocks of calcium carbonate (CaCO3) on two reef flats in Maunalua Bay, O'ahu. Over a 6‐month (coral nubbins) and yearlong (CaCO3 blocks) deployment period, we combined multiple metrics of coral growth (buoyant weight, surface area, and linear extension) and bioerosion with a suite of co‐measured physicochemical parameters that are indicators for SGD (carbonate chemistry, dissolved inorganic nutrients, temperature, salinity, and water motion). All coral growth metrics showed a modal response to SGD, and the percent change in buoyant weights and nubbin surface area were negatively related to pH variation. SGD negatively affected coral survival, indicating that at high levels of SGD, salinity stress could be killing corals, but at mid‐levels SGD‐associated nutrients could be increasing growth rates. SGD had a positive effect on bioerosion, most likely due to the positive effect of increased nutrients on bioeroding organisms. Further, coral accretion rates were two orders of magnitude higher than bioerosion rates; however, given the low coral cover on these reef flats, the total carbonate accreted by corals is much lower than suggested by rates alone. These results indicate that corals can thrive on SGD‐impacted reefs if isolated from secondary stressors, so active management to reduce macroalgae and sedimentation could allow coral recovery in Maunalua Bay. [ABSTRACT FROM AUTHOR]

Abstract: Runaway expansion of shallow ponds can catalyze the conversion of vegetated marshes into open water environments. Predicting how this transition affects ecosystem functioning is difficult because little is known about pond biogeochemistry. We characterized sediment organic matter sources and transformations in three ponds with different plant communities, over alternating periods of tidal isolation and flushing, during summer and fall, using a combination of stable isotopes, lipid biomarkers, and benthic fluxes. Sediment respiration rates (1.66 ± 0.09 mmol C m−2 d−1 to 28.53 ± 7.76 mmol C m−2 d−1) were comparable to shallow estuaries and driven by sulfate reduction. Rates varied across ponds, reflecting differences in summertime Ruppia maritima and macroalgae abundances, but were similar between seasons. Interactions between aboveground plant and sediment bacterial communities translated into distinct biogeochemical processes across the three ponds. Tidal isolation and summer weather intensified plant and bacterial community effects on pond carbon dynamics, resulting in algal biomass and lipid δ13C values that were 3–12‰ enriched, compared to nearby habitats. Surface sediment organic matter mainly derived from pond microalgae and was compositionally distinct from tidal creeks and marshes. Surprisingly, sediment bacteria were not tightly coupled to benthic microalgae but decomposed multiple carbon sources in surface sediments and became increasingly reliant on buried peat at deeper horizons. Pond development over time could largely be explained by sediment respiration and the simultaneous accretion of the surrounding marsh platform. The role of decomposition in pond expansion is consistent with previous assessments based on whole‐pond metabolism rates. Consequently, future pond expansion could alter ecosystem biogeochemistry and reduce carbon storage. [ABSTRACT FROM AUTHOR]

In microelectrodischarge milling (μED-milling) process, material removal occurs in the form of debris and these particles are predominantly spherical in shape with size varying from few nanometers to micrometers. The behavior of the debris particles in μED-milling is not well discussed in the literature, and this study will provide useful insight into the debris movement and its accretion on machining surfaces. Debris in its molten or cooled state will cause major issues in the μED-milling process such as secondary discharge and redeposition. Its presence at one location in large number gives rise to secondary discharge causing a disturbance in sparking, and its movement may affect the geometry of channel due to redeposition. The necessary drive for debris movement along the gap is provided by tool rotation. The experimental investigation of debris movement with dielectric at a gap of few micrometers is practically difficult due to complex phenomenon of the process. Thus, the present objective is focused to investigate the movement of debris and dielectric in the gap through simulation with consideration for fluid debris interaction and subsequent deposition. The effect of debris size, the position of injection, and the tool speed on the accretion of particles on the surface are analyzed by ANSYS Fluent. The trajectory of the particles, distance traveled, and accretion rate are calculated using discrete phase modeling. The 2D simulation results of accretion are compared with experimental surface micrographs. [ABSTRACT FROM AUTHOR]

Underneath rock slopes of rubble mound structures often one or more granular filter layers are present. These filter layers prevent base material washout. In contrast to traditional filters, geometrically open filters allow for some movement of base material. In order to design such open filters the amount of erosion and accretion of base material needs to be predicted. Based on 2D physical model tests Van Gent and Wolters (2015) presented a method to estimate the erosion and accretion of sand underneath rock slopes. Since the developed method was only valid for perpendicular wave attack, a new study has been performed to assess effects of oblique wave attack on the amount of erosion and accretion of sand underneath a rock slope. For that purpose 3D physical model tests were performed in a wave basin with 5 different wave angle between 0° (perpendicular wave attack) and 75°. Based on the test results it was shown how the effects of wave obliquity can be taken into account in the design of open filters. In addition, the effect of the storm duration on open filters has been studied. This led to an extended design method to predict the amount of erosion and accretion of sand underneath rock slopes under wave loading. [ABSTRACT FROM AUTHOR]

While the isotopically heterogeneous nature of the terrestrial mantle has long been established, the origin, scale, and longevity of the heterogeneities for different elements and isotopic systems are still debated. Here, we report Nd, Hf, W, and Os isotopic and highly siderophile element (HSE) abundance data for the Boston Creek komatiitic basalt lava flow (BCF) in the 2.7 Ga Abitibi greenstone belt, Canada. This lava flow is characterized by strong depletions in Al and heavy rare earth elements (REE), enrichments in light REE, and initial ε 143 Nd = +2.5 ± 0.2 and intial ε 176 Hf = +4.2 ± 0.9 indicative of derivation from a deep mantle source with time-integrated suprachondritic Sm/Nd and Lu/Hf ratios. The data plot on the terrestrial Nd-Hf array suggesting minimal involvement of early magma ocean processes in the fractionation of lithophile trace elements in the mantle source. This conclusion is supported by a mean μ 142 Nd = −3.8 ± 2.8 that is unresolvable from terrestrial standards. By contrast, the BCF exhibits a positive 182 W anomaly (μ 182 W = +11.7 ± 4.5), yet is characterized by chondritic initial γ 187 Os = +0.1 ± 0.3 and low inferred source HSE abundances (35 ± 5% of those estimated for the present-day Bulk Silicate Earth, BSE). Collectively, these characteristics are unique among Archean komatiite systems studied so far. The deficit in the HSE, coupled with the chondritic Os isotopic composition, but a positive 182 W anomaly, are best explained by derivation of the parental BCF magma from a mantle domain characterized by a predominance of HSE-deficient, differentiated late accreted material. According to the model presented here, the mantle domain that gave rise to the BCF received only ∼35% of the present-day HSE complement in the BSE before becoming isolated from the rest of the convecting mantle until the time of komatiite emplacement at 2.72 Ga. These new data provide strong evidence for a highly heterogeneous Archean mantle in terms of absolute HSE abundances and W isotopic composition, and also indicate slow mixing, on a timescale of at least 1.8 billion years. Additionally, the data are consistent with a stagnant-lid plate tectonic regime in the Hadean and Archean, prior to the onset of modern-style plate tectonics. [ABSTRACT FROM AUTHOR]

Abstract: Sowohl durch natürliche als auch durch vom Menschen beeinflusste Vorgänge werden Kohlenwasserstoffe in sehr großer Menge in die Erdatmosphäre emittiert. Ihre atmosphärischen Oxidationsvorgänge bilden fast ausschließlich reaktive RO2‐Radikale als Zwischenprodukte, deren atmosphärisches Schicksal noch nicht vollständig erforscht ist. Hier wird gezeigt, dass Gasphasenreaktionen von zwei RO2‐Radikalen Aufbauprodukte bilden, die aus dem Kohlenstoffgerüst beider Reaktionspartner bestehen. RO2‐Radikale, die funktionelle Gruppen tragen, zeigen hohe Bildungsgeschwindigkeiten der Aufbauprodukte, die mit denen der entsprechenden Reaktionen mit NO und HO2 konkurrieren. Dieses Reaktionsverhalten, das bei der Modellierung von atmosphärischen Prozessen noch nicht berücksichtigt wurde, kann für das Schicksal von RO2‐Radikalen in allen Bereichen der Atmosphäre wichtig oder sogar vorherrschend sein. Darüber hinaus können die gebildeten Aufbauprodukte einen besonders niedrigen Dampfdruck aufweisen, der sie als wirksame Quelle für das sekundäre organische Aerosol kennzeichnet. [ABSTRACT FROM AUTHOR]

Abstract: There is concern that accelerating sea‐level rise will exceed the vertical growth capacity of coastal‐wetland substrates in many regions by the end of this century. Vertical vulnerability estimates rely on measurements of accretion and/or surface‐elevation‐change derived from soil cores and/or surface elevation tables (SETs). To date there has not been a broad examination of whether the multiple timescales represented by the processes of accretion and elevation change are equally well‐suited for quantifying the trajectories of wetland vertical change in coming decades and centuries. To examine the potential for timescale bias in assessments of vertical change, we compared rates of accretion and surface elevation change using data derived from a review of the literature. In the first approach, average rates of elevation change were compared with timescale‐averaged accretion rates from six regions around the world where sub‐decadal, decadal, centennial, and millennial timescales were represented. Second, to isolate spatial variability, temporal comparisons were made for regionally unique environmental categories within each region. Last, comparisons were made of records from sites where SET‐MH stations and radiometric measurements were co‐located in close proximity. We find that rates vary significantly as a function of measurement timescale and that the pattern and magnitude of variation between timescales are location‐specific. Failure to identify and account for temporal variability in rates will produce biased assessments of the vertical change capacity of coastal wetlands. Robust vulnerability assessments should combine accretion rates from multiple timescales with the longest available SET record to provide long‐term context for ongoing monitoring observations and projections. [ABSTRACT FROM AUTHOR]

The Kandelia candel (L.) Druce mangrove forest in the Kuantu Nature Reserve, North Taiwan, has experienced rapid expansion since 1978. This study assesses the current extent and historical expansion of the mangroves by means of aerial photograph interpretation. An analysis of a time series of aerial photographs, covering the period from 1978 to 2012, has revealed major changes in the distribution of mangroves in relation to the geomorphic changes in the Kuantu Nature Reserve. The results indicate that the area-increasing rate was highest (2.27 ha/y) during the 1986-94 period, meaning the most rapid encroachment of mangroves into the habitats of Cyperus and Phragmites saltmarshes. Based on the Shannon diversity index t test, with the encroachment of Kandelia, the landscape composition in the Kuantu Nature Reserve has been dominated by the mangrove swamp of Kandelia. The geomorphic changes in the area of accretion and erosion were derived from the 0-m contour in the 1:5000 topographic maps in 1978, 1986, 1994, and 2005. Based on a review of related literature, the possible driving forces of geomorphic changes are explained by human impacts (e.g., land subsidence because of the overpumping of groundwater and collapse triggered by sand pumping) and natural forces (e.g., increased accretion induced by mangroves and headward expansion of tidal creek and typhoon-induced erosion). The complicated interplay between vegetation and landform in the Kuantu Nature Reserve is discussed from the viewpoint of biogeomorphic succession. Similar mangrove expansion cases are also examined. [ABSTRACT FROM AUTHOR]

The Marbat basement (Sultanate of Oman) belongs to the Neoproterozoic accretion domain of the Arabian-Nubian shield. We present new geochronological, petrological and geochemical data as an extension of our previous study (Denèle et al., 2017) re-interpreting this basement as a metamorphic core complex (MCC). We showed that this MCC consists of a metamorphic unit (Juffa complex) separated by an extensional detachment from a plutonic unit (Sadh complex and Tonalite plutons). Geochemical data show that the Juffa metasediments correspond to volcanogenic graywackes, suggesting deposition in front of a juvenile magmatic arc. New in situ U–Pb zircon data show that the protolith of the Juffa paragneisses is Tonian in age (960–830 Ma). The Juffa complex recrystallized under amphibolite facies conditions (950 MPa, 630 °C) corresponding to thermal gradient of 17–18 °C/km, i.e. close to that observed in fore-arc environment subjected to tectonic underplating. It was then retrogressed (<400 MPa, <400 °C) during exhumation of the MCC. Phase assemblages of the Sadh complex and Tonalite plutons record magmatic temperatures estimated at 700–840 °C and 610–840 °C from hornblende and zircon-saturation thermometry, respectively; pressures are grossly estimated at ca. 250 MPa. These data and structural evidence led us to consider that the Sadh complex is a plutonic unit emplaced during exhumation of the MCC. Hence, we re-interpret the previously published zircon core U–Pb ages of the Banded gneisses (ca. 860–830 Ma) as inherited, and zircon rim ages (ca. 815 Ma) as the age of their intrusion. This suggests that the parent magma of all these granitoids could have interacted with volcanic material equivalent to the Juffa complex. Overall, the Marbat area developed during the Tonian and involved (i) deposition of volcanosediments (Juffa complex) in an island-arc environment (960–830 Ma); (ii) metamorphism under middle pressure conditions during tectonic underplating at ca. 820–815 Ma, followed by emplacement of plutonic rocks in the upper crust during initiation of the MCC at ca. 815–810 Ma; and (iii) late-tectonic intrusions associated with MCC amplification at ca. 800–790 Ma (Mahall intrusives and Tonalite plutons). [ABSTRACT FROM AUTHOR]

In many regions of the world, subsidence of organic rich soils threatens levee stability and freshwater supply, and continued oxidative loss of organic matter contributes to greenhouse gas production. To counter subsidence in the Sacramento-San Joaquin Delta of northern California, we examined the feasibility of using constructed wetlands receiving drainage water treated with metal-based coagulants to accrete mineral material along with wetland biomass, while also sequestering carbon in wetland sediment. Nine field-scale wetlands were constructed which received local drainage water that was either untreated (control), or treated with polyaluminum chloride (PAC) or iron sulfate (FeSO 4 ) coagulants. After twenty three months of flooding and coagulant treatment, sediment samples were collected near the inlet, middle, and outlet of each wetland to determine vertical accretion rates, bulk density, sediment composition, and carbon sequestration rates. Wetlands treated with PAC had the highest and most spatially consistent vertical accretion rates (∼6 cm yr −1 ), while the FeSO 4 wetlands had similarly high accretion rates near the inlet but rates similar to the untreated wetland (∼1.5 cm yr −1 ) at the middle and outlet sites. The composition of the newly accreted sediment in the PAC and FeSO 4 treatments was high in the added metal (aluminum and iron, respectively), but the percent metal by weight was similar to native soils of California. As has been observed in other constructed wetlands, the newly accreted sediment material had lower bulk densities than the native soil material (0.04–0.10 g cm −3 versus 0.2–0.3 g cm −3 ), suggesting these materials will consolidate over time. Finally, this technology accelerated carbon burial, with rates in PAC treated wetland (0.63 kg C m −2 yr −1 ) over 2-fold greater than the untreated control (0.28 kg C m −2 yr −1 ). This study demonstrates the feasibility of using constructed wetlands treated with coagulants to reverse subsidence by accreting the resulting organo-metal flocculent and storing carbon at rates exceeding untreated wetlands. Management and design questions remain for how to best integrate this technology into heavily subsided land to lower the risks and consequences associated with levee failure, improve water quality, and ultimately restore these lands to tidal wetlands. [ABSTRACT FROM AUTHOR]

The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2–100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D5) or ozonolysis of β - pinene, oligomerization rate constants on the order of 10-3 to 10-1M-1 s-1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase. [ABSTRACT FROM AUTHOR]

Seismic discontinuities between the Moho and the inferred lithosphere–asthenosphere boundary (LAB) are known as mid-lithospheric discontinuities (MLDs) and have been ascribed to a variety of phenomena that are critical to understanding lithospheric growth and evolution. In this study, we used S-to-P converted waves recorded by the USArray Transportable Array and the OIINK (Ozarks–Illinois–Indiana–Kentucky) Flexible Array to investigate lithospheric structure beneath the central U.S. This region, a portion of North America's cratonic platform, provides an opportunity to explore how terrane accretion, cratonization, and subsequent rifting may have influenced lithospheric structure. The 3D common conversion point (CCP) volume produced by stacking back-projected Sp receiver functions reveals a general absence of negative converted phases at the depths of the LAB across much of the central U.S. This observation suggests a gradual velocity decrease between the lithosphere and asthenosphere. Within the lithosphere, the CCP stacks display negative arrivals at depths between 65 km and 125 km. We interpret these as MLDs resulting from the top of a layer of crystallized melts (sill-like igneous intrusions) or otherwise chemically modified lithosphere that is enriched in water and/or hydrous minerals. Chemical modification in this manner would cause a weak layer in the lithosphere that marks the MLDs. The depth and amplitude of negative MLD phases vary significantly both within and between the physiographic provinces of the midcontinent. Double, or overlapping, MLDs can be seen along Precambrian terrane boundaries and appear to result from stacked or imbricated lithospheric blocks. A prominent negative Sp phase can be clearly identified at 80 km depth within the Reelfoot Rift. This arrival aligns with the top of a zone of low shear-wave velocities, which suggests that it marks an unusually shallow seismic LAB for the midcontinent. This boundary would correspond to the top of a region of mechanically and chemically rejuvenated mantle that was likely emplaced during late Precambrian/early Cambrian rifting. These observations suggest that the lithospheric structure beneath the Reelfoot Rift may be an example of a global phenomenon in which MLDs act as weak zones that facilitate the removal of cratonic lithosphere that lies beneath. [ABSTRACT FROM AUTHOR]

It remains an elusive goal to simultaneously model the astrophysics of Solar System accretion while reproducing the mantle chemistry of more than one inner terrestrial planet. Here, we used a multistage core-mantle differentiation model based on Rubie et al. (2011, 2015) to track the formation and composition of Earth and Mars in various Grand Tack formation simulations. Prior studies showed that in order to recreate Earth's mantle composition, it must grow first from reduced (Fe-metal rich and O-poor) building blocks and then from increasingly oxidized (FeO rich) material. This accretion chemistry occurs when an oxidation gradient exists across the disk so that the innermost solids are reduced and increasingly oxidized material is found at greater heliocentric distances. For a suite of Grand Tack simulations, we investigated whether Earth and Mars can be simultaneously produced by the same oxidation gradient. Our model did not find an oxidation gradient that simultaneously reproduces the mantle compositions of Earth and Mars. Due to its small mass and rapid formation, the formation history of Mars-like planets is very stochastic which decreases the likelihood of compatibility with an Earth-producing oxidation gradient in any given realization. To reconcile the accretion history and ideal chemistry of the Mars-like planet with the oxidation gradient of an Earth-producing disk, we determined where in the Earth-producing disk Mars must have formed. We find that the FeO-rich composition of the Martian mantle requires that Mars' building blocks must originate exterior to 1.0 astronomical units (AU). • Earth's building blocks reflect an average of the entire inner disk, unlike Mars. • Mars' growth history varies greatly between simulations due to dynamical mixing. • Mars' building blocks must originate exterior to 1 AU to reproduce FeO rich mantle. [ABSTRACT FROM AUTHOR]

Icing on transmission lines is a serious threat to safe operation of power grids. Ice accretion on power lines includes two processes, which are the collision between water droplets and a conductor, and the freezing of water on the conductor. In the previous studies on the collision efficiency, a circular shape of a conductor has been assumed. In this work, the change of conductor shape is specified through changing the number of the conductor strands, and the influence of this on the collision efficiency is analyzed by Fluent. The results show that the relationship between conductor strand number and the collision efficiency is quite small, but different under different conditions, such as wind speed and median volume diameter of water droplets. From the point of view of the icing rate in the beginning of an icing event, the optimal conductor size and shape which lead to minimizing the collision efficiency can be calculated based on the local historical weather data using these results provided that accurate micro-meteorological data are available. [ABSTRACT FROM AUTHOR]

Because of the significant role soils play in the health and function of the Everglades ecosystem, soil conservation is a central tenet of Everglades restoration. As such, it is critical to anticipate ecosystem responses to hydrologic restoration activities from the perspective of the soil component. The broad goal of this work was to investigate the resulting effects of various hydrologic restoration scenarios on soil processes of phosphorus and carbon accretion by modeling soil edaphic processes using the Everglades Landscape Model. The results of modeling effort suggest that full implementation of the Comprehensive Everglades Restoration Plan provides the greatest spatial reduction of phosphorus (P) enrichment throughout the system. The existing condition baseline ( ECB) scenario, which represents the current hydrologic and nutrient impaired condition, produced the highest observed rates of soil carbon accretion; however, this scenario is successful in accretion of soil carbon due to elevated P conditions, not restored hydrology. Management implications of restoration with respect to soil elucidated from this work include: (1) prioritization of habitat quality and ecosystem function (via P reduction) over carbon sequestration potential and (2) need to reduce P inputs before restoring hydrologic connectivity and historic flows. [ABSTRACT FROM AUTHOR]

Rising sea levels threaten the sustainability of coastal wetlands around the globe. The ability of coastal marshes to maintain their position in the intertidal zone depends on the accumulation of both organic and inorganic materials, and vegetation is important in these processes. To study the effects of vegetation type on surface elevation change, we measured surface accretion and elevation change from 2011 to 2016 using rod surface elevation table and feldspar marker horizon method (RSET-MH) in two Phragmites and two Suaeda marshes in the Liaohe River Delta. The Phragmites marshes exhibited higher rates of surface accretion and elevation change than the Suaeda marshes. The two Phragmites marsh sites had average surface elevation change rates at 8.78 mm/yr and 9.26 mm/yr and surface accretion rates at 17.56 mm/yr and 17.88 mm/yr, respectively. At the same time, the two Suaeda marsh sites had average surface elevation change rates at 5.77 mm/yr and 5.91 mm/yr and surface accretion rates at 13.42 mm/yr and 14.38 mm/yr, respectively. The elevation change rates in both the Phragmites marshes and the Suaeda marshes in the Liaohe River Delta could keep pace and even continue to gain elevation relative to averaged sea level rise in the Bohai Sea reported by the 2016 State Oceanic Administration, People's Republic of China projection (2.4-5.5 mm/yr) in current situations. Our data suggest that vegetation is important in the accretionary processes and vegetation type could regulate the wetland surface elevation. However, the vulnerability of coastal wetlands in the Liaohe River Delta need further assessment considering the accelerated sea level rise, the high rate of subsidence, and the declining sediment delivery, especially for the Suaeda marshes. [ABSTRACT FROM AUTHOR]

Interaction of windblown sand with maritime vegetation, either as dune migration or episodic grain transport is a common phenomenon along many sandy coasts. Vegetation introduces antecedent surface roughness, especially when scaled to the landform height, but its role may be concealed if overwhelmed by aeolian incursion and burial. Where field observations and cores lack detail for characterizing this complex process, ground-penetrating radar (GPR) offers continuous visualization of aeolian sequences. Along the Curonian Spit, Lithuania, dune reactivation phases resulted in massive invasion of siliciclastic sand triggered by natural perturbations and land clearance. Massive (>30 m high) dunes entombed mature pine, oak, and alder stands and this process is ongoing. Mid-frequency (200 MHz) georadar surveys reveal landward-dipping lateral accretion surfaces interrupted by high-amplitude point-source anomalies produced by recently buried trees. In tropical regions, dense vegetation and potential for rapid lithification of carbonate sand results in more complex internal structures. Along the windward coast of San Salvador Island, the Bahamas, a massive dune has buried several generations of maritime scrubland, resulting in highly chaotic reflection pattern and high target density. On a nearby Little Exuma Island, numerous reentrants in aeolianites promoted formation of blowouts and incursion of windblown sand 10–25 m into a silver thatch palm forest. High-frequency (800 MHz) GPR images resolve diffractions from trunks and roots buried by > 2 m of oolitic sand. Basal refection morphology helps differentiate the irregular dune/beachrock surface from a smooth palm-frond mat. Aside from detecting and mapping buried vegetation, geophysical images capture its effect on sediment accumulation. This has the potential for differentiating its effect from other discordant structures within dunes (clasts, dissolution voids, trunk molds, burrows, and cultural remains). [ABSTRACT FROM AUTHOR]