Hydrodynamic Intensity Research Articles

New insights into local scour characteristics around vibrating monopiles under combined wave-current conditions

Cyclic lateral vibrations on monopile foundations of offshore wind turbines throughout their service life may affect the local scour around the foundations. While previous studies have explored local scour around vibrating monopile foundations under current-only conditions, the local scour characteristics around these foundations under combined wave-current conditions remains unclear. This experimental study presents new insights into local scour characteristics around vibrating monopile foundations under combined wave-current conditions. A novel dimensionless parameter, the friction velocity-based Froude number (Fr∗), is proposed to quantify the effect of hydrodynamic intensity on the scour process. Based on the Fr∗ values obtained in the experiment, three distinct regimes were identified to characterize the impact of vibrations on the scouring process: In Regime 1 (Fr∗ < 0.055), scour dimensions are more pronounced, while in Regime 3 (Fr∗ > 0.06), they are less significant compared to the equilibrium scour hole around static monopile foundations. In the transitional phase, Regime 2 (0.055 <Fr∗ < 0.06), scour dimensions fluctuate by up to 10.9% relative to static conditions. Additionally, an estimation equation for equilibrium scour depth based on Fr∗ is developed, demonstrating good prediction accuracy and broad applicability. These insights advance the understanding of scour features and provide a valuable reference for predicting scour depth around vibrating monopile foundations in diverse hydrodynamic environments.

Proximity to inlet channel drives spatial variation in sediment carbon across a lagoonal seagrass meadow

Seagrass meadows can be sinks for organic carbon, but estimates of global organic carbon stocks are complicated by substantial spatial variability in organic carbon burial observed within meadows. To improve estimates of organic carbon burial in seagrass meadows, it is necessary to understand the causes of the spatial heterogeneity. This study investigated relationships between spatial patterns in sediment organic carbon storage and accretion rates, hydrodynamics, and proximity to sources of organic carbon in a current-dominated Zostera marina Linnaeus meadow in Menemsha Pond, Massachusetts, USA. Sediment and velocity measurements were conducted at six stations along a 150-m transect across the meadow oriented perpendicular to the pond's unvegetated inlet channel. The meadow's edge near the channel had higher organic carbon than the channel as well as the highest organic carbon within the meadow. With increasing distance from the meadow's edge, all of the following decreased: sediment organic and total carbon, sediment accretion rates, peak tidal velocity, sediment trap mass deposition rate, and the relative contribution of non-seagrass sources to sediment organic carbon. Lower tidal velocities farther from the inlet channel reduced sediment resuspension, consistent with lower sediment trap mass deposition, which should enhance organic carbon content and organic carbon accretion rates. However, the opposite trend of decreasing organic carbon content (>50 % across the transect) and decreasing accretion rates with distance from channel was observed. This suggested that the local hydrodynamic intensity was not controlling organic carbon accretion, which was instead constrained by supply limitation and controlled by the lagoon-scale flow circulation.

Sedimentary records of giant landslide-dam breach events in western Sichuan, China

Introduction: Landslide-dammed lake outburst floods (LLOFs) are common natural disasters in high-mountain regions, posing serious safety threats to residents’ livelihoods and properties and causing major damage to engineering facilities. Giant landslides and river damming events commonly occur in the Eastern Tibetan Plateau in southwestern China. Dam failure generate LLOFs that form outburst deposits (ODs). This phenomenon is particularly common in some giant ancient landslide-dammed lakes.Methods: This study conducted a detailed investigation of the sedimentary characteristics of large-scale landslide-dammed lake outburst deposits in the Diexi Reach of the Upper Minjiang River and Tangjiashan Reach of the Tongkou River Basin, West Sichuan Plateau, China. Meanwhile, typical evidence of high-energy ODs was recorded.Results and Discussion: The longitudinal distribution of these ODs is similar to an elongated fan-shaped terrace along the river channel, presenting a distinctive sedimentary disordered–sub-ordered–ordered sequence from upstream to downstream. Several typical units of “sedimentary facies” are developed in the OD profiles, such as boulder units deposited by high-energy outburst flood (OF) events and the gravel and sand units representing pulsating-flow sedimentary environments during the recession stage. The grain size frequency curves are bimodal, and the granularity accumulated curves are upward convex, which reflect that the detrital characteristics of the sediment source area are mainly composed of coarse gravel and boulders. This indicates that the coarse gravel sediment gradually become decreased from upstream to downstream. Moreover, the OD hydrodynamic intensity displays a gradual weakening, and sediment sorting is improved. From upstream to the downstream, the mean particle-size and sorting of the ODs gradually decrease. The skewness become larger, and the kurtosis of the ODs is distributed in all the types. In addition, the different combinations of quartz sand surface microtextures indicate the transformation from high-to low-energy impacts over a short distance, which is controlled by flood hydrodynamics and regime.Significance: These sedimentary characteristics of ODs explain the hydrodynamic changes during the propagation of OFs, and are also important records for distinguishing between ODs, and “normal” floods.

Landcover-based detection of rapid impacts of extreme storm on coastal landscape

On September 24, 2022, Post-Tropical Hurricane Fiona made landfall in Atlantic Canada and caused unprecedented damages to the coastal communities and ecosystems therein. The aftermath triggered local government and communities in Prince Edward Island (PEI), Canada to rethink current policies and practices for coastal protection in the context of climate change. This historic hazard represents the escalating frequency and intensity of extreme weather events that globally threaten coastal regions, accelerating coastal erosion and endangering communities. This study employs landcover-based detection to assess rapid storm impact of Fiona on coastline of PEI using Sentinel-2 satellite images, to gauge the efficacy of landcover-based detection and quantify storm-induced coastal environmental changes. Our results indicate that, following Fiona, over 51 km2 coastal land loss due to the erosion at beach foreshore and inundation at tidal flat, and over 11 km2 sand dune loss mainly on the PEI north shore. This constitutes a 3.5 % loss of coastal land resources within the 1798 km2 PEI coastal zone. Fiona also caused over 194 km2 area in coastal buffer zone showed temporal fluid-mud from the eroded sediments of sand dunes, cliffs, and tidal flats, suggesting the significant sediment loss from vertical structures in addition to the direct retreat. The landcover-based method can be regarded as a valuable tool for the storm impacts on coastal environments. Based on the coastal change pattern, more sustainable coastal protection and adaptation measures should be developed, focusing on reducing hydrodynamic intensity and improving erosion capacity, with consideration of the increasing likelihood of more intense and frequent storm events in a warming climate.

Tracking the source of antibiotic resistome in the stormwater network drainage in the presence of sewage illicit connections

Stormwater pipes are illicitly connected with sewage in many countries, which means that sewage enters stormwater pipes and the drainage is discharged to surface water without any treatment. Sewage contains more pathogens and highly risky antibiotic resistance genes (ARGs) than surface runoff. Therefore, sewage may alter the microbial and ARG compositions in stormwater pipe drainage, which in turn leads to an increased risk of resistance in surface water. However, the effects of sewage on ARGs in the drainage of stormwater networks have not been systematically studied. This study characterized the microbial and ARG composition of several environmental compartments of a typical stormwater network and quantified their contributions to those in the drainage. This network transported ARGs and microorganisms from sewage, sediments in stormwater pipes, and surface runoff into the drainage and thus into the river. According to metagenomic analysis, multidrug resistance genes were most abundant in all samples and the numbers and relative abundance of ARGs in the drainage collected during wet weather were comparable to that of sewage. The results of SourceTracker showed that the relative contribution of sewage was double that of rainwater and surface runoff in the drainage during wet weather for both microorganisms and ARGs. Desulfovibrio, Azoarcus, and Sulfuritalea were connected with the greatest number of ARGs and were most abundant in the sediments of stormwater pipes. Furthermore, stochastic processes were found to dominate ARG and microbial assembly, as the effects of high hydrodynamic intensity outweighed the effects of environmental filtration and species interactions. The findings of this study can increase our understanding of ARGs in stormwater pipe drainage, a crucial medium linking ARGs in sewage to environmental ARGs.

Seed settling and trapping during submerged secondary dispersal: Implications for saltmarsh recruitment and restoration

Given the decline of global salt marshes, there is a pressing need to pinpoint the key processes that limit and facilitate seed-based pioneer recruitment. Secondary seed dispersal, in the form of short-distance submerged movement, is a prerequisite for initiating pioneer establishment in adjacent tidal flats but has not been fully appreciated and understood. In this study, using a settling tube and race-track flume, seeds of four global occurring saltmarsh species were studied in terms of their settlement speed and trapping opportunity to understand how seed traits and physical settings affect submerged dispersal behavior and thus seed-based saltmarsh recruitment. Present study led to the following novel insights: 1) Seeds have density-dependent settling speeds, which are comparable to that of fine sand, but much faster than that of very fine sand and silt. Since the latter is the type of sediment commonly found in many estuaries worldwide (such as the Scheldt), seeds will typically settle faster than local sediments. A sufficiently long hydrodynamic-calm period allows slowly settling sediment to bury settled seeds, otherwise, seeds will remain uncovered if the period is short. 2) Seed trapping ratio increased linearly with surface roughness (a proxy for local topographic complexity), but this effect becomes smaller with increasing hydrodynamic intensity. Seed drag coefficient was identified as the key biotic factor contributing to interspecies variability in trapping ratio. Overall, present results suggest that submerged seed dispersal may form a primary bottleneck for salt marsh recruitment by limiting seed availability via two mechanisms: i) reduced chance of seed burial through asynchronous settling of seeds and sediment particles; ii) reduced probability of seed trapping due to encountering smooth tidal flat surfaces. This study provide mechanistic and data basis for the targeted application of biophysical models in predicting outcomes of saltmarsh recruitment and long-term maintenance, thereby informing seed-based conservation and restoration.

Evolutions of sedimentary facies and palaeoenvironment and their controls on the development of source rocks in continental margin basins: A case study from the Qiongdongnan Basin, South China Sea

Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China. However, the development of high-quality source rocks in this basin, especially in its deep-water areas, are still not fully understood. In this study, evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated. The results show that during the Oligocene and to Miocene periods, the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment, which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin. In shallow-water areas, the palaeoproductivity and reducibility successively decrease, and the hydrodynamic intensity gradually increases for the water columns of the Yacheng, Lingshui, and Sanya-Meishan strata. In deep-water areas, the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata, while the reducibility gradually increases for the water columns of the Yacheng, Lingshui, and Sanya-Meishan strata. In general, the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks. Meanwhile, the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential. The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.

Effect of Hydrodynamic Condition on Adsorption of Sulfadiazine on Marine Sediments

In the present study, the adsorption behavior of sulfadiazine (SDZ) on various sediments under different hydrodynamic conditions generated by a rocking shaker was investigated. Based on the dye mixing experiments, three regimes with different hydrodynamic characteristics, i.e., laminar, transition, and turbulent regimes, were identified. The hydrodynamic intensity was found to have a positive effect on the adsorption of SDZ, In general, the adsorption capacity followed the order of turbulent &gt; transition &gt; laminar &gt; static. Compared to quartz sands, montmorillonite exhibited a narrower range of adsorption capacity under different hydrodynamic conditions, which implies it is less sensitive to the hydrodynamic conditions. For adsorption kinetics, sands fit the pseudo-first-order model, while montmorillonite fits the pseudo-second-order model. For adsorption thermodynamics, the Freundlich model showed a better correlation coefficient for all sediments. In addition, it was found that particle size could affect the antibiotic adsorption capacity, and the presence of salts inhibited the adsorption performance.

Erosion and accretion patterns on intertidal mudflats of the Yangtze River Estuary in response to storm conditions

Understanding of erosion and accretion patterns over intertidal mudflats during storm periods is vital for the management and sustainable development of coastal areas. This study aimed to investigate the effect of the 2014 storm Fung-wong on the erosion and accretion patterns of the Nanhui intertidal mudflats in the Yangtze estuary, China, based on field measurements and Delft3D numerical modeling. Results show that prolonged easterly winds during the storm enhance the flood velocity, weaken the ebb velocity, and even change the current direction. The current velocity, wave heights, and bed-level changes increased by 1–1.43 times, 2.40–3.88 times, and 2.28–2.70 times than those of normal weather, respectively. The mudflats show a spatial pattern of overall erosion but increasing erosion magnitude from the high (landward) mudflat to the low (seaward) mudflat during the storm. The magnitude of bed-level change increases with increasing wind speed, but the spatial pattern of erosion and accretion remains the same. The main reason for this pattern is the longer submersion duration of the low mudflat compared with the high mudflat, so the hydrodynamic process is longer and stronger, leading to an enhancement in bed shear stress and sediment transport rate. Wind speed increases the hydrodynamic intensity but does not affect on the submersion duration over each part of the intertidal mudflat. This study is helpful to improve the understanding of physical processes during storms on intertidal mudflats and provides a reference for their protection, utilization, and management, as well as for research in related disciplines.

Microbiome of High-Rank Coal Reservoirs in the High-Production Areas of the Southern Qinshui Basin.

To study the distribution features of microorganisms in distinct hydrological areas of the southern Qinshui Basin, C-N-S microorganisms were studied using 16S RNA sequencing, metagenome sequencing and geochemical technologies, showing the high sensitivity of microorganisms to the hydrodynamic dynamics of coal. The hydrodynamic intensity of the #3 coal gradually decreased from the runoff areas to the stagnant areas. The stagnant zones have higher reservoir pressure, methane content, δ13CDIC and TDS and lower SO42-, Fe3+ and NO3- concentrations than the runoff areas. C-N-S-cycling microorganisms, including those engaged in methanogenesis, nitrate respiration, fermentation, nitrate reduction, dark oxidation of sulfur compounds, sulfate respiration, iron respiration, chlorate reduction, aromatic compound degradation, denitrification, ammonification and nitrogen fixation, were more abundant in the stagnant areas. The relative abundance of C-N-S functional genes, including genes related to C metabolism (e.g., mcr, mer, mtr, fwd and mtd), N metabolism (e.g., nifDKH, nirK, narGHI, nosZ, amoB, norC and napAB) and sulfur metabolism (e.g., dsrAB and PAPSS), increased in the stagnant zones, indicating that there was active microbiological C-N-S cycling in the stagnant areas. The degradation and fermentation of terrestrial plant organic carbon and coal seam organic matter could provide substrates for methanogens, while nitrogen fixation and nitrification can provide nitrogen for methanogens, which are all favorable factors for stronger methanogenesis in stagnant areas. The coal in the study area is currently in the secondary biogenic gas generation stage because of the rising of the strata, which recharges atmospheric precipitation. The random forest model shows that the abundance of C-N-S microorganisms and genes could be used to distinguish different hydrological zones in coal reservoirs. Since stagnant zones are usually high-gas-bearing zones and high-production areas of CBM exploration, these microbiological indicators can be used as effective parameters to identify high-production-potential zones. In addition, nitrate respiration and sulfate respiration microorganisms consumed NO3- and SO42-, causing a decrease in the content of these two ions in the stagnant areas.

Erosion-reducing potential of Salix psammophila roots in the water–wind crisscrossed erosion region of the Chinese Loess Plateau: A simulated investigation

Laboratory-simulated experiments under a one-way wind erosion–rain erosion sequence were conducted to investigate the effect of S. psammophila roots on wind and water erosion processes and quantify its erosion-reducing potential. With the collected soil of sandy loam and planted shrub of S. psammophila, 16 soil boxes including bare and root-permeated soils were arranged in March 2017 and conducted in August 2017. With the wind speeds of 11 and 14 m s−1 and rainfall intensities of 60 and 100 mm h−1, two levels of interaction (11 m s−1 × 60 mm h−1 and 14 m s−1 × 100 mm h−1) were designed. The particle-size composition and sediment transport flux were examined in the former wind tunnel experiments, and the runoff hydrodynamic parameters and runoff and water erosion rates were determined in the following rainfall tests. The sediment reduction effect by roots (%) was used to quantify the erosion-reducing potential of roots. The results demonstrated that in the former wind tunnel experiments, compared with the bare soils, the root-permeated soils showed a slight coarsening of surface soil and had 18.03% and 35.71% less sediment transport flux at wind speeds of 11 and 14 m s−1, respectively. In the following rainfall tests, S. psammophila roots weakened the hydrodynamic intensity of overland flow and decreased runoff and water erosion rates by 13.34%, 30.70% and 4.44%, 43.72% at rainfall intensities of 60 and 100 mm h−1, respectively. Different from the water erosion process of bare soils, which showed an increased fluctuated trend, the root-permeated soils presented a steady increase in the early stage of rainfall and then a decrease-stable trend at the mid and end of rainfall. In the wind tunnel–rainfall experiments, the sediment reduction effect by Salix psammophila roots showed 24.37% and 39.72% at levels of 11 m s−1 × 60 mm h−1 and 14 m s−1 × 100 mm h−1, respectively. This kind of study may provide more insights into understanding ecological impacts of sandy vegetation construction on the water–wind crisscrossed erosion region of the Chinese Loess Plateau and also sandy land.

Pinpointing stage‐specific causes of recruitment bottlenecks to optimize seed‐based wetland restoration

Abstract Attaining the goals of ‘The UN‐Decade on Ecosystem Restoration’ requires efficient methods for large‐scale restoration of degraded ecosystems. Seed‐based approaches may offer opportunities for massive recovery of native vegetation but are prone to failure when applied to highly valued coastal wetlands such as salt marshes. Pinpointing the impact of early life stage transitions on recruitment variation across species and contexts is a critical first step toward amplifying seed‐based restoration efficiency. Large‐scale field experiments were conducted in 100 microhabitats across eight salt marshes to investigate root causes of variation in seed retention and seedling emergence, using four globally occurring salt marsh species as models. The resulting insights and dataset were then translated into predictors using machine learning, for targeted application in disentangling recruitment bottlenecks. Seed retention, regardless of species, was identified as the principal bottleneck in recruitment with hydrodynamic intensity, bed‐level dynamics, and burial depth as critical governing factors. Seedling emergence was discerned as the critical bottleneck driving cross‐species recruitment variability and was pivotally influenced by soil salinity and burial depth. Predictions using machine learning under different restoration scenarios indicated that simple management, such as seed burial or species selection, can create opportunities to bypass potential recruitment bottlenecks. Synthesis and applications. Our results suggest that the failure of seed‐based coastal wetland restoration should be attributed to multiple recruitment bottlenecks that arise from different life stage transitions and are context/species dependent. In planning future seed‐based restoration practices, managers should assess the variability of life stage‐specific dominant factors at target sites to identify site‐specific recruitment bottleneck(s). Our work underscores the need for strategic management that buffers against recruitment bottlenecks to improve restoration efficiency and advances the application of data‐driven techniques to make seed‐based restoration predictive.

Effects of Farming Conditions on Infestation of Oysters by Shell-Boring Annelids

Oysters are farmed worldwide and one of the main problems is infestation by polydorin polychaetes. The native Crassostrea gasar and the exotic Pacific Crassostrea gigas oysters support aquaculture production along the subtropical southern Brazilian coast. Worm infestation rates in the two oyster species were evaluated, hypothesizing that infestation is related to stocking densities and hydrodynamic intensity. The main oyster production areas in Brazil were sampled: Parana state, Medeiros (25° 22′ S, 48° 27′ W), Ponta Oeste da Ilha do Mel (25° 29′ S, 48° 22′ W), and Cabaraquara (25° 49′ S, 48° 34′ W) and the Santa Catarina state, Riberão da Ilha (27° 43′ S, 48° 33′ W). Generalized linear models were performed to analyze the effects of sites characterized by different stocking density, hydrodynamic intensity and mean sea surface temperature (SST), the condition index, and the oyster species (native or exotic). Polydorin infestation was higher (mean of 6.02 polydorins/oyster) under higher oyster stocking densities and intermediate hydrodynamic intensity sites (Riberão da Ilha, in the Santa Catarina state). In Parana State, the two sites with similar stocking densities, Ponto Oeste (7,638 oysters/m2) and Cabaraquara (7,550 oyster/m2) presented a higher polydorin infestation in the site with low hydrodynamic intensity and higher mean SST (5.34 vs. 2.64 polydorins/oyster, respectively). The condition index was not impacted by the polydorin infestation. Native C. gasar showed a higher polydorin infestation than the exotic C. gigas (6.02 vs. 1.36, respectively), indicating a higher vulnerability to worm infestation. These results may lead to a better understanding of the infestation patterns of locally grown oysters and to the implementation of better farming management.

Spatial heterogeneity in sediment and carbon accretion rates within a seagrass meadow correlated with the hydrodynamic intensity

The majority of the carbon stored in seagrass sediments originates outside the meadow, such that the carbon storage capacity within a meadow is strongly dependent on hydrodynamic conditions that favor deposition and retention of fine organic matter within the meadow. By extension, if hydrodynamic conditions vary across a meadow, they may give rise to spatial gradients in carbon. This study considered whether the spatial gradients in sediment and carbon accretion rates correlated with the spatial variation in hydrodynamic intensity within a single meadow. Field measurements were conducted in three depth zones across a Zostera marina L. (eelgrass) meadow in Nahant Harbor, Massachusetts. Four sediment cores were collected in each zone, including one outside the meadow (control) and three within the meadow at increasing distances from the nearest meadow edge. Sedimentation and carbon accretion rates were estimated by combining the measurements of dry bulk density, organic carbon fraction (%OC), 210Pb, and 226Ra. Tilt current meters measured wave velocities within each zone, which were used to estimate turbulent kinetic energy (TKE). Both sediment and carbon accretion rates exhibited spatial heterogeneity across the meadow, which were correlated with the spatial variation in near-bed TKE. Specifically, both accretion rates increased with decreasing TKE, which was consistent with diminished resuspension associated with lower TKE. A method is proposed for using spatial gradients in hydrodynamic intensity to improve the estimation of total meadow accretion rates.

Environmental mechanism of capturing nutrient-rich particles by the lake bottom trap in a large, shallow lake

Bottom traps capture and preserve nutrient-rich mobile bottom sediments by forming a weak hydrodynamic environment. In this study, Lake Chaohu, a large shallow lake in China, was considered the research object, and the influence of trap at the bottom of the lake on the physical, chemical, and biological characteristics of sediments and water were analysed by combining on-site monitoring and laboratory analysis. The results showed that the hydrodynamic intensity was attenuated by more than 65% at the bottom of the trap compared with that of the upper surface of the water body under different weather conditions, forming an obviously weak hydrodynamic environment. The weak dynamic environment and large sedimentation rate at the bottom of the trap were beneficial to the sedimentation and storage of fine particles that adsorb nutrients, such as nitrogen and phosphorus, in the water. Owing to the increase in local water depth, a low-temperature and low-dissolved oxygen environment was formed inside the trap. The abundance and diversity of microorganisms in the sediments inside the trap were reduced, and the abundance of nitrifying and denitrifying bacteria in the sediment was reduced by approximately 50%, indicating an environment favourable for nitrogen accumulation in the sediment in the trap. Therefore, the environment inside the bottom trap is favourable for capturing the high nutrient-rich particulate matter in the water, which provides theoretical support for use of the lake bottom traps for controlling the endogenous pollution of shallow lakes.

The study of a consistent pattern of heat and mass transfer at drying fiber-forming polymers

In this article, the consistent pattern of mass transfer in the process of drying granular polyethylene terephthalate (PET), polycaproamide (PCA), and polyamide 66 (PA 66) were studied. A modified quasi-stationary method was used to analyze the data. The characteristic time and the hydrodynamic intensity index were obtained based on experimental data. Some features of water sorption and desorption by fiber-forming polymers were studied.

Processes and mechanisms of phosphorus mobility among sediment, water, and cyanobacteria under hydrodynamic conditions.

Phosphorus (P) has an important role in eutrophication and it is essential to explore the processes and mechanisms of P mobility in natural waters. In this study, laboratory experiments were conducted to simulate the SW system (sediment and water) and SAW system (sediment, algae, and water) under four hydrodynamic intensity conditions (static control, 50 rpm, 125 rpm, and 200 rpm treatments), to investigate P mobility. Results in SW system showed that sediment was an important source of P for overlying water, and the released total P (TP) increased with stronger hydrodynamic intensity, when P associated with metal pools (redox-sensitive P [BD-P] and meta-oxides bound P [NaOH-P]) were the most unstable and easier to migrate into the overlying water. Stronger hydrodynamic disturbances could enhance the processes including sediment resuspension, dissolution of particles, and release of P, when P mobility had a close relationship with redox conditions near sediment-water interface (SWI). Therefore, the release of TP, BD-P, and NaOH-P from sediment increased and decreased in the control and 50-200 rpm treatments over time. In SAW system, the release of TP significantly increased from sediment comparing to SW system, and the growth of Microcystis aeruginosa could selectively enhance the release of BD-P, NaOH-P, and organic P (OP). Meanwhile, the released P from sediment was quickly accumulated by algal cells. The maximum accumulation ability of P by cells, the highest photosynthetic efficiency, and the best growth of M. aeruginosa were observed in 125 rpm treatment. But with excessively strong hydrodynamic intensity (200 rpm treatment), the accumulation ability of P and alkaline phosphatase activity (APA) of M. aeruginosa was suppressed, which might hinder algal utilization of P and inhibit algal growth. Overall, our findings demonstrated the patterns of P mobility in natural ecosystems and could contribute to the understanding of P cycling.

Changes in the hydrodynamic intensity of Bosten Lake and its impact on early human settlement in the northeastern Tarim Basin, Arid Central Asia

The climate of arid central Asia (ACA) is extremely dry and early human settlement in the region were dependent upon an unstable water supply. Thus, knowledge of the hydrological fluctuation history is essential for understanding the relationship between humans and the environment in the region. Here we present a record of Holocene lake hydrodynamic intensity based on the grain size of suspended lacustrine silt isolated from the sediments of Bosten Lake, which feeds a river flowing to the northeastern Tarim Basin. The results show that lake hydrodynamic intensity was very weak during the early Holocene (12.0–8.2 ka); and then increased with two distinct centennial-millennial-scale intervals of weak intensity during 4.7–3.7 ka and 1.2–0.5 ka. Notably, increases in lake hydrodynamic intensity occurred 2.2 kyr prior to an increase in local precipitation. We speculate that this was a consequence of relatively high early summer temperatures during 8.2–6.0 ka that resulted in an increased water supply from melting snow and ice in mountainous areas of the catchment. Thus, we conclude that the changes of the Holocene hydrodynamic intensity of Bosten Lake were mainly controlled by temperature or precipitation at different times. The variations in the hydrodynamic intensity of Bosten Lake also influenced water availability for the human population that occupied the downstream area of the northeastern Tarim Basin. A drastic decrease in hydrodynamic intensity of Bosten Lake occurred around 400 and 700 CE likely has caused the emigration of the inhabitants and cultural collapse of Loulan Kingdom.

A first assessment of organic carbon burial in the West Gironde Mud Patch (Bay of Biscay)

On the Bay of Biscay continental shelf, there are several mid-shelf mud patches including La Grande Vasière to the north, the West Gironde Mud Patch (WGMP) off the Gironde estuary and the Basque Mud Patch close to the Spanish border. In general, these deposits are several meters thick and cover coarser substrate. Questions remain about their storage capability for fine particles and carbon. This work investigates the sedimentation of the WGMP in order to develop a first estimate of organic carbon (OC) burial. Interface sediment cores were collected at nine stations along two cross-shelf transects in October–November 2016. X-radiograph imaging and grain-size analyses were used to characterize sedimentary structures. 210Pbxs depth profiles were established to calculate sediment (SAR) and mass (MAR) accumulation rates. Sedimentary structures indicate episodic sandy inputs overlying older deposits at proximal sites, and relatively continuous sedimentation at seaward locations. On the outer-central portion of the northern transect, a maximum SAR (0.47 cm yr−1) was observed, suggesting a depocenter. On the southern transect, excluding two stations where sedimentary inputs appear massive but sporadic, the SARs are lower (<0.3 cm yr−1). Quantitative estimates of OC burial rates increase seaward with a maximum of 45 gC m−2 yr−1. To evaluate carbon loading independent of grain-size variability, OC values were normalized to surface area of sediments (SA). Interestingly, a qualitative comparison of OC burial efficiencies using the OC/SA ratio highlights three groups of sites (low, medium and relatively high OC burial efficiency) which are likely related both to different sedimentary environments and variable deposition conditions linked to local environmental conditions and depth. This work highlights the likely control of hydrodynamic intensity and sedimentary inputs on the amount of OC stored in the WGMP sediments.

Multi-jet hydrodynamic surface finishing and X-ray computed tomography (X-CT) inspection of laser powder bed fused Inconel 625 fuel injection/spray nozzles

• Multiphase hydrodynamic finishing reduces the surface roughness of L-PBF fuel nozzles. • Direct metal laser sintered IN625 fuel injection/spray nozzles are surface finished. • Profile and areal surface roughness reduced uniformly across all nozzle branches. • The peak height above the core surface Spk in the inlet section reduced by 75 %. • X-CT inspection showed dimensional deviations ≤ 100 μm in the nozzles. Laser powder bed fused (L-PBF) components have poor surface finish quality that hinders their use in practical applications. Surface finishing the complex passages in the L-PBF components is particularly challenging. We aimed to produce a consistent surface finish on the internal passages of direct metal laser sintered (DMLS) Inconel 625 fuel nozzles—regardless of the as-built non-uniform surface—using a multi-jet hydrodynamic finishing technique. We effectively harnessed the hydrodynamic intensity and surface finished the fuel injection/spray tips comprising multiple branches. We found profile and areal surface roughness reduced up to 90 % across all branches. Also, the peak height above the core surface Spk at the nozzle inlet reduced by 40–75 %. X-ray computed tomography (X-CT) inspection post-finishing showed that roundness and circularity of the injection/spray tips improved, while most critical nozzle dimensions were within the tolerance. The results lend further credence that the proposed technique: Multi-jet hydrodynamic cavitation abrasive finishing (MJ-HCAF) can be used to surface-finish and deploy the L-PBF fuel nozzles in practical applications—ensuring safe implementation.