Transport Patterns Research Articles

Uptake, removal and trophic transfer of fluorescent polyethylene microplastics by freshwater model organisms: the impact of particle size and food availability.

As an emerging contaminant, microplastics (MPs) are widely distributed in freshwater ecosystems and pose potential threats to aquatic organisms, attracting significant attention from both the scientific community and the general public. However, there is still uncertainty regarding the mechanisms of MPs transfer within aquatic biota and how particle size and food availability influence their transport patterns. In this study, zebrafish (Danio rerio) were selected as a model organism to investigate the uptake and elimination of fluorescent polyethylene (PE) MPs under different exposure scenarios (waterborne or trophic transfer, with or without food) and varying particle sizes (ranging from 10-300 μm at concentrations of 0.1, 2, and 300 mg/L). Additionally, water fleas (Daphnia magna) were provided as prey for the fish. The dynamic accumulation of PE-MPs sized between 10-20 μm at a concentration of 25 mg/L by daphnia was also determined along with its impact on animal feeding behavior. The results demonstrated that both organisms were capable of ingesting PE-MPs during exposures lasting up to 24 hours for daphnia and up to 72 hours for zebrafish. Furthermore, rapid elimination rates were observed within just 30 minutes for daphnia and between 6-12 hours for zebrafish. The presence of food reduced MPs uptake and removal by daphnia but significantly increased MP elimination by fish. Zebrafish showed a preference for ingesting larger-sized MPs that they could easily recognize; however, trophic transfer from daphnia to fish was found to be the primary route of ingestion specifically for PE-MPs sized between 10-20 μm. The findings suggest that while fish directly ingest fewer invisible MPs from the water column, they still accumulate these particles through predation on contaminated prey organisms. Therefore, it is imperative to prioritize the ecological risks associated with the transfer of MPs from zooplankton to fish.

Research on heavy metal enrichment and transportation in tea plant-soil systems of different varieties.

This study aimed to investigate heavy metal enrichment in different tea plant varieties and their distribution within different plant parts and to clarify the behavioral characteristics of heavy metals in the tea tree-soil system and their influencing factors. In this study, soil samples were collected from the root zones of 13 tea tree varieties in Guizhou, which had been planted for 10years. The aim was to compare the physicochemical properties of tea plantation soils under soil-forming matrixes and consistent management. Additionally, the study investigated the enrichment and transportation patterns of Cd, Cr, Cu, Pb, Zn, and Ni in the tea tree-soil systems of different tea tree varieties. The results showed that the planting of tea trees decreased the soil pH by 0.5; soil nutrients decreased; soil Pb, Cr, Ni, Cu, and Zn contents in the root zone increased; and Cd content decreased. Heavy metals were mainly enriched in the roots, and Zn, Cu, Ni, and other elements related to the protein and enzyme synthesis of tea trees could be mostly transported to the stems and leaves. There were significant differences in the enrichment and transportation of heavy metals among the different tea tree varieties. Under consistent soil-forming parent material, soil pH, organic matter, nutrients, and other indices only had a significant effect on heavy metal enrichment in the tea tree roots. Therefore, in areas with high background soil heavy metal contents, the construction of tea plantations should be based on regional soil environmental conditions to choose tea tree varieties with low heavy metal enrichment capacities to avoid the risk of high background soil heavy metals on the safe production of tea for consumers.

Cross-habitat patterns of sediment transport and release by surgeonfishes

Cross-habitat patterns of sediment transport and release by surgeonfishes

THE COOLING EFFECT OF COMBUSTOR EXIT LOUVER SCHEME ON A TRANSONIC NOZZLE GUIDE VANE ENDWALL

Abstract The ever-increasing combustor exit temperature in modern turbine engine designs raises challenges for the nozzle guide vane cooling. Due to the complexity of NGV cooling design, the cooling effect from the upstream combustor cooling features can prove valuable. This study investigates, experimentally and numerically, the cooling effect of a louver cooling scheme near the combustor exit on the NGV endwall. The wind tunnel testing and CFD simulation are carried out with engine-representative conditions of an exit Mach number of 0.85, an exit Reynolds number of 1.5 × 106, an inlet turbulence intensity of 16%, and a density ratio of 2.1. Various coolant mass flow ratios from 1% to 4% are tested to demonstrate the effect of the coolant rate. For the geometry studied, the results found a critical mass flow ratio between 1%~2%. The coolant forms a uniform film only by exceeding this value to provide good coverage upstream of the NGV passage inlet. As for the cooling of the NGV passage, the mass flow ratio of the range investigated is insufficient for desirable cooling performance. The pressure side endwall proves most difficult for the coolant to reach. In addition, the fishmouth cavity at the combustor-NGV passage causes a three-dimensional cavity vortex that transports the coolant in the pitch-wise direction. The transport pattern is dependent on the coolant mass flow ratio. Therefore, the authors propose combining this louver scheme with the upstream jump cooling scheme for a desirable NGV cooling system.

Significant shift of footprint patterns and pollutant source contributions: insights from observations at Shanghuang observatory, East China

Abstract As two of the most important products of the combustion process, carbon dioxide (CO2) and carbon monoxide (CO) are commonly used as tracers for combustion source assignment. Their relationship will help to better understand the regional carbon cycle and assess climate forcing effects. In this study, mixing ratios of CO2 and CO were continuously measured using a Picarro gas concentration analyzer at the Atmospheric Boundary Layer Eco-Environmental Shanghuang Observatory, Chinese Academy of Sciences (ABLECAS) throughout 2022–2023. The variability of the mixing ratio of CO to CO2 (ΔCO/ΔCO2) in a 1 h time interval was calculated based on linear slope analysis after background values were determined and subtracted. The results showed that the mixing ratio of CO had a clear seasonal variability with a moderate increase in the spring (249.1 ± 59.6 part per billion (ppb)) and winter (257.8 ± 90.3 ppb), mostly due to more frequent transport from north of the Yangtze River. ΔCO/ΔCO2 at the ABLECAS varied with air mass origin, with a linear slope 0%–1% on a 1 h basis. Relatively high ΔCO/ΔCO2 values for an air mass from the north in the winter indicate that the emission sources had lower combustion efficiency. In summer, the ΔCO/ΔCO2 ratio mostly reflected the background conditions for air masses from marine areas. The potential source regions and contribution assignments were evaluatedat the ABLECAS according to source–receptor relationship analysis using the FLEXPART model with CO as a pollutant tracer from 2015 to 2023. We found that the footprint of an air mass had a clear transition period between 2018 and 2019, and a synoptic anomaly, related to Arctic Oscillation strength and west Pacific subtropical high position, plays a key role in influencing the pollutant transport patterns. This study provides a scientific basis for the formulation of air quality regulation policy, and helps to implement the national carbon neutralization strategy.

Numerical simulation and experimental study of microplastic transport under open channel shear flow: Roles of particle physical properties and flow velocities

Microplastic (MP) transport patterns under open channel shear flow remain unclear. This study investigates the transport laws of MPs at various flow velocities, MP densities, sizes and concentrations in the U-shaped experimental flume and the numerical flume based on Lattice Boltzmann Method (LBM). The results indicate that the average horizontal particle velocity and the transport distances of Polyvinyl chloride (PVC) and Polystyrene (PS) particles increase with the average cross-sectional flow velocity, while the average vertical particle velocity decreases with it. The total average particle velocity closely matches the average vertical particle velocity, regardless of the variation in MP size, density and concentration. Formula-based analysis reveals that the acceleration of spherical MP transport mainly depends on the particle size and its consequent relative drag force term (RDFT) under the conditions with a single type of MP particles, but on the particle density and its consequent RDFT and relative gravity term (RGT) in the case concerning different types of MP particles with identical particle sizes. The average horizontal particle velocity maximum of PVC and PS are both strongly correlated with the average flow velocity maximum in the cross-section. This correlation lowers with the MP particle size and concentration, and is independent of MP density. Our findings can provide reference for the prevention and control of MP pollution in rivers.

Dominant spring precipitation anomaly modes and circulation characteristics in the Tarim Basin, Central Asia

Recently, extreme precipitation has occurred frequently in the Tarim Basin, which has a fragile ecological environment, arousing widespread concern. Using daily precipitation observations from 42 stations in the Tarim Basin during the spring of 1980–2021 and monthly circulation reanalysis data from the European Center for Medium-Range Weather Forecasts Reanalysis v5, as well as statistical analyses and physical diagnostic methods, this study investigated the abnormal modes and the evolution characteristics and differences in atmospheric circulation. The results show that the spring precipitation anomalies in the Tarim Basin can be divided into two independent precipitation modes: the first (EOF1) is a precipitation pattern that is uniform throughout the region and the second (EOF2) is an east–west inverse pattern. Thus, there are distinct differences in the atmospheric circulation characteristics responsible for abnormal spring precipitation modes in the basin. When the precipitation across the entire basin is consistently excessive, the 500 hPa geopotential height is affected by the negative phase of the North Atlantic Oscillation related circulation, and the 700 hPa wind field is controlled by abnormal southwesterly winds. Water vapor transport is mainly driven by anomalous water vapor uplift along the terrain in the middle latitudes west of the Atlantic Ocean and south of the Arabian Sea. This leaves the Tarim Basin with a net water vapor budget and abnormally high atmospheric precipitable water. The opposite situation occurs when the precipitation across the entire basin is consistently lower than normal. When there is a west-to-east precipitation gradient, The western region of the Tarim Basin is dominated by upward airflow, whereas the eastern region is dominated by downward airflow, providing dynamic conditions for the west-to-east precipitation gradient. Under the influence of anomalous water vapor transport from the southwest and water vapor convergence, water vapor conditions favorable for precipitation can occur. The net water vapor in the basin also exhibited an abnormal west-to-east transport pattern. Moreover, the atmospheric precipitable water demonstrated an inverse phase distribution under the EOF2 atmospheric precipitation mode in the Tarim Basin.

Geophysical characterization of the bedrock and regolith in the Pranmati basin critical zone, Uttarakhand Himalaya

The young active Himalayan mountain is characterized by steep slope and dissected topography in overall compressive tectonic setting. The mountain belt has primarily coarse textured soil with poor water holding capacity and is highly prone to erosion. The erosion not only affects many ecosystems located at downstream but also has detrimental effects on the critical zone (CZ). In the present study, we have carried out DC electrical resistivity study in the Pranmati catchment of the Alaknanda basin, a Himalayan critical zone in the Lesser Himalaya, to understand the pattern of soil erosion, transportation and deposition by characterizing the bedrock architecture and hence regolith thickness. A total of 6 electrical resistivity tomogram (ERT) profiles were laid at two locations in the catchment, one in a plain grassland and another at a crop field located on a hill slope of >25o. The study area in the Baijnath klippe, consists of quartz-biotite gneisses with layers of quartz mica-schist enclosed by thrust faults. Electrical resistivity sections of the downslope grassland site show a sharp resistivity contrast between the southwest and northeast transects suggesting south-eastern increase in dip of the bedrock, oblique to the north-east facing surface topography and a thick regolith (> 10 m). The resistivity sections of the site located on the hillslope yield a very thin layer of regolith (< 2 m) indicating significant soil erosion and high weathering of the bedrock. We propose that the water–rock interaction within the porous regolith facilitated by subsurface water circulation might be a potential source for the thick regolith. The observations substantiate existing hypotheses for the evolution and development of deep critical zones. From the results, it has been hypothesized that the bedrock architecture and water channel paths within the CZ together control the regolith thickness.

Shoreline Behavior in Response to Coastal Structures: A Case Study in Haikou Bay, China

The rapid development of coastal structures on sandy coastlines raises concerns about their impacts on the shoreline’s evolution and the sediment transport dynamics. This study utilized a numerical modeling approach to simulate the multi-year response of Haikou Bay’s coastline to various nearshore structures, including piers and a large artificial island. The LITLINE module of the MIKE21 (v2020) software was employed to analyze the sediment transport patterns across three distinct coastal segments. The simulation results indicated that the sediment transport directions varied significantly: from west to east in the western segment, from east to west in the middle segment, and convergence toward the center in the eastern segment, divided by a construction trestle. The net sediment transport rates were quantified as 2000 m3/year for the western segment, 8000 m3/year for the middle segment, and 13,000 m3/year (west) and 10,000 m3/year (east) for the eastern segment. Due to the conflicting sediment transport directions on each side of the breakwater, noticeable deposition occurred on both sides. The presence of the artificial island created notable deposition in its wave shadow area, while the overall impact on the shoreline changes diminished over time. These findings underscore the significant influence of human activities, particularly coastal structures, on the natural evolution of shorelines.

Contrasting Domestic and Global Impacts of Emission Reductions in China on Tropospheric Ozone

AbstractSustained near‐surface ozone pollution despite stringent emission controls in China has drawn wide attention. However, how such rapid regional emission reductions affect global tropospheric ozone remains unexplored. Here, using an ensemble of measurements and global model simulations, we find Chinese emission reductions during 2013–2020 have increased domestic surface ozone; particularly in North China, they have decreased the global tropospheric ozone burden by 2.7 Tg (54% of China's anthropogenic contribution and 7% of global anthropogenic contribution in 2019) and ozone radiative forcing by 8.8 mW m−2 (64% of China's anthropogenic contribution and 9% of global anthropogenic contribution in 2019). Nitrogen oxides (NOx) associated nonlinear chemistry and height‐dependent atmospheric transport patterns primarily cause the contrasting impacts. Future Chinese NOx emission controls would continue to decrease global tropospheric ozone, while regional surface ozone may still increase unless NOx reductions exceed ∼53% of the 2019 level. Our results reveal the substantial benefit of regional emission reductions in China on global tropospheric ozone mitigation.

On the Scaling of Transport Phenomena at a Monotonously Changing Hydraulic Conductivity Field

Monotonously stratified porous medium, where the layered medium changes its hydraulic conductivity with depth, is present in various systems like tilled soil and peat formation. In this study, the flow pattern within a monotonously stratified porous medium is explored by deriving a non-dimensional number, Fhp, from the macroscopic Darcian-based flow equation. The derived Fhp theoretically classifies the flow equation to be hyperbolic or parabolic, according to the hydraulic head gradient length scale, and the hydraulic conductivity slope and mean. This flow classification is explored numerically, while its effect on the transport is explored by Lagrangian particle tracking (LPT). The numerical simulations show the transition from hyperbolic to parabolic flow, which manifests in the LPT transition from advective to dispersive transport. This classification is also applied to an interpolation of tilled soil from the literature, showing that, indeed, there is a transition in the transport. These results indicate that in a monotonously stratified porous medium, very low conducting (impervious) formations may still allow unexpected contamination leakage, specifically for the parabolic case. This classification of the Fhp to the flow and transport pattern provides additional insight without solving the flow or transport equation only by knowing the hydraulic conductivity distribution.

Three-dimensional distribution of aerosols of multiple types at daily scale using TROPOMI spaceborne observations

We present new satellite-based daily observations of the 3D distribution of aerosols from most common types and origins, both over land and ocean, derived from TROpospheric Ozone Monitoring Instrument (TROPOMI) measurements. This is done using the so-called AEROS5P (AEROsol Sentinel 5 Precursor) approach which retrieves vertical profiles of aerosol extinction from passive measurements of high-resolution spectral reflectance in the visible and near infrared for cloud-free conditions. Previous work demonstrated the potential of this approach, but it was initially applicable only to biomass burning aerosols with limited spatial coverage over ocean. The new methodology presented here generalizes the method for the most common aerosol types and improves spatial coverage. We take advantage of an operational aerosol type product derived from Visible Infrared Imaging Radiometer Suite (VIIRS) observations, combined with those from TROPOMI, to choose a priori aerosol set of intensive properties (particle size and refractive index). AEROS5P shows good agreement in aerosol optical depth, when compared to observations from AErosol RObotic NETwork and other widely used satellite measurements. Additionally, the vertical distribution of aerosol plumes of different types derived from AEROS5P agrees well with lidar coincident observations from the Advanced Topographic Laser Altimeter System spaceborne sensor and ground-based measurements. We utilize AEROS5P to analyze the three-dimensional distribution of aerosols for four different scenarios. It traces the three-dimensional pathways of smoke from Canadian wildfires reaching the Eastern USA in July 2023, desert dust from the Namibian deserts over the southeast Atlantic Ocean confined near the surface during the same month, fine aerosol pollution over Western Europe during June 2019, and an extreme dust event mixed with fine aerosol pollution over Northern China in March 2021. These observations provide valuable insights into aerosol transport patterns, surface-level air quality impacts, and can potentially be used to assess the radiative effects at various atmospheric layers.

Response time of fast flowing hydrologic pathways controls sediment hysteresis in a low-gradient watershed, as evidenced from tracer results and machine learning models

Hydrologic controls on the timing of sediment transport and sediment hysteresis patterns remain an open area of investigation in hydrology, especially for low-gradient watersheds with substantial instream sediment deposition. Sediment hysteresis, which describes the mismatch between hydrograph peak and sedigraph peak, aids with elucidation of the mechanisms of sediment transport in watersheds. Most frequently, the controls of hysteresis are attributed to the proximity of sediment sources to monitoring locations in a watershed. However, this assumption, while widely applied, is infrequently verified. We investigated the controls of sediment hysteresis in a low gradient system located in the Bluegrass Region of central Kentucky, USA. Turbidity and conductivity sensors installed at the basin outlet provided data to quantify sediment hysteresis and separate hydrologic flow pathways (i.e., by describing the source of water delivered to the watershed’s outlet) using a tracer-based approach. Predictive hydrologic parameters, including hydrologic pathways, event magnitude, and antecedent conditions, were estimated and grouped based on hydrologic similitude. Thereafter, we identified parameters required to predict sediment hysteresis using a tailored ensemble feature selection approach coupled with three machine learning algorithms—Random Forest, K-Nearest Neighbors, and Gradient Boosted Trees. Results from the analysis of 68 storm events occurring over a two-year period showed that clockwise events accounted for 85 % of the total sediment yield despite comprising only 53 % of the events. The hysteresis index (HI) can be predicted (r = 0.8, RMSE = 0.12) using three, out of the thirty-nine hydrologic parameters considered. The most important predictors of HI reflect the volume of event rainfall and the relative proportions of new water (i.e., water derived from precipitation during the storm event) and old water (i.e., water previously stored in the watershed) comprising the hydrograph. Further analyses reveal that new water timing—which changes with the rainfall volume—and sediment timing are closely linked, suggesting that variations in the hysteresis patterns are controlled by changes in the response time of fast flowing water pathways. This implies that hydrologic pathways, as opposed to sediment proximity to the watershed outlet, control sediment hysteresis in this watershed. These results have important implications for better understanding the mechanisms controlling sediment transport at the watershed scale.

NTLFlowLyzer: Towards generating an intrusion detection dataset and intruders behavior profiling through network and transport layers traffic analysis and pattern extraction

Network security remains a critical concern in modern computing systems due to the constant emergence of threats and attacks. This paper introduces a comprehensive behavioral profiling solution to address the limitations of current intrusion detection methods in identifying zero-day attacks and novel malicious behaviors. Beginning with raw network data, the proposed framework progresses through multiple stages, ultimately culminating in the creation of activity-specific profiles. Central to this approach is NTLFlowLyzer, a novel network traffic analyzer, which generates an updated dataset, BCCC-CIC-IDS2017, for enhanced profile generation. The core of the profiling system leverages the distinct behaviors exhibited by individual features and the diverse correlations observed across various activities. The profiling procedure attains accuracy and robustness by integrating a novel feature selection algorithm and a pattern extraction process. Furthermore, behavior similarity is introduced to quantify the resemblance between activities based on their features and behaviors. We rigorously evaluate the effectiveness of our model by subjecting it to comprehensive testing, followed by meticulous comparison with previous works. Our proposed framework proficiently characterizes eight malicious activities with an accuracy rate surpassing 99.8%, while displaying promising performance in profiling various other activities. These findings, derived from our comprehensive experiments, provide valuable guidance for accurately implementing behavioral profiling.

An Impact Assessment of Cordon Pricing Relaxation on Modal Shift During the COVID-19 Pandemic

ABSTRACT The COVID-19 pandemic brought significant disruptions to transportation patterns worldwide, with a notable increase in Private Vehicle (PV) usage. Many studies have focused on travel restrictions, while neglecting to consider potential changes in transportation-related policies implemented during COVID-19 that may have improved public health. The present study explores the motivations for modal shifts to PVs and tries to analyze which of the risks of exposure and modifications in transportation policies has caused these modifications. Focusing on the case study of Tehran, Iran, where cordon pricing was relaxed during the pandemic, the study collected data through online and paper-based surveys from 1475 respondents. Binary logit models were employed to analyze the data and understand the impact of destination location, residency area, trip purpose, trip frequency, and vehicle characteristics on modal shift behavior. In addition to COVID-19 exposure as a primary reason for the modal shift, respondents also identified the relaxation of cordon pricing restrictions as a factor that increased the utility of PVs. The study's findings contribute to better understanding the dynamics of travel behavior during pandemics, guiding policymakers in devising effective strategies to address both public health concerns and traffic conditions.

Long-term (2010–2021) lidar observations of stratospheric aerosols in Wuhan, China

Abstract. This study analyzes the vertical distribution, optical properties, radiative forcing, and several perturbation events of stratospheric aerosols using observations from a ground-based polarization lidar in Wuhan (30.5° N, 114.4° E) from 2010 to 2021. The background stratospheric aerosol optical depth (sAOD) was 0.0044 ± 0.0019 at 532 nm, as calculated during a stratosphere-quiescent period from January 2013 to August 2017. In addition, several cases of volcanic aerosol and wildfire-induced smoke were observed. Volcanic aerosols from the Nabro (2011) and Raikoke (2019) eruptions (both in boreal summer) increased the sAOD to 2.9 times the background level. Tracers of smoke from the Canadian wildfire in the summer of 2017 were observed twice, at 19–21 km on 14–17 September and at 20–23 km on 28–31 October, with a plume-isolated aerosol optical depth (AOD) of 0.002–0.010 and a particle linear depolarization ratio δp of 0.14–0.18, indicating the dominance of non-aged smoke particles. During these summertime events, the injected stratospheric aerosols were captured by the large-scale Asian monsoon anticyclone (AMA), confining the transport pathway to mid-latitude Asia. On 8–9 November 2020, smoke plumes originating from the California wildfire in October 2020 appeared at 16–17 km, with a mean δp of 0.13. Regarding seasonal variation, the sAOD in the cold half-year (0.0054) is 69 % larger than in the warm half-year (0.0032) due to stronger meridional transport of stratospheric aerosols from the tropics to middle latitudes. The stratospheric radiative forcing was −0.11 W m−2 during the stratosphere-quiescent period and increased to −0.31 W m−2 when volcanic aerosols were largely injected. These findings contribute to our understanding of the sources and transport patterns of stratospheric aerosols over mid-latitude Asia and serve as an important database for the validation of model outputs.

Quantifying free tropospheric moisture sources over the western tropical Atlantic with numerical water tracers and isotopes

AbstractTropical free‐tropospheric humidity plays a crucial role for the Earth's radiative balance and climate sensitivity. In addition to atmospheric humidity, stable water isotopes can provide important information about the hydrological cycle. We use the isotope‐ and water tagging‐enabled version of the COSMOiso model to determine isotopic fingerprints of diagnosed moisture pathways over the western tropical Atlantic (WTA). A convection‐permitting, high‐resolution (5 km) nudged simulation is performed for January–February 2020. During this period, the target region is characterized by alternating large‐scale circulation regimes with different humidity and isotope signatures. Moist conditions in the middle troposphere (300–650 hPa) are associated with moisture transport from the south, east, southeast, as well as evaporation from the North Atlantic, while dry conditions correspond to extratropical transport from the north and west. To predict the contribution of different moisture sources, we used a statistical model based on the local specific humidity and temperature as predictors and obtained an R‐squared (R2) of 0.52. Adding water isotopes improved the prediction (R2 = 0.73), showing that isotopes provide unique information on moisture sources and transport patterns beyond conventional local observations.

Morphological and geological responses of barrier estuaries to dam-opening systems

River discharge depending on the dam gate operation method is an important factor underlying changes in estuarine sedimentation dynamics, but comprehensive studies are limited by data collection constraints. The hydrological operation of Nakdong Dam, designed to prevent seawater intrusion by opening during ebb tides and heavy rains and closing during flood tides, presents an ideal setting for such investigations. This study focused on the Nakdong River Estuary (NRE), utilizing aerial photography, bathymetry data, and sedimentation rate data to determine alterations in sediment transport and deposition patterns within the two tributary estuaries. Spatial discrepancies in sedimentation patterns across the eastern and western regions of the NRE were particularly evident in the spatial variations of textural characteristics and sedimentation rates. An enhanced ebb tidal prism resulting from dam gate opening in the eastern region caused the development of erosional topography and a rough depositional environment, forming a landward migrating (transgressive) barrier island system. Conversely, the predominantly closed dam gates in the western region maintained a consistent deposition pattern due to a regular tidal prism, facilitating the formation of sedimentary topography and fine sediment deposition. Consequently, barrier islands followed a seaward building (prograding) system. Therefore, the results suggested a role of modern dam gate operation as a major sedimentation mechanism, providing valuable insights for the sustainable management of estuarine sediment environments.

Organic carbon burial dynamics at the Chukchi Shelf margin: Implications for the Arctic Ocean carbon sink

Organic carbon (OC) burial plays a crucial role in regulating the Arctic Ocean's capacity to uptake atmospheric CO₂. In this study, we demonstrate the transport, deposition, and degradation patterns of different sources of OC to reveal burial dynamics at the Chukchi Shelf margin, a region with the highest primary production in the Arctic Ocean currently affected by dramatic sea ice retreat. Observations of suspended particulate material show a pronounced separation of terrestrial and marine OC in the water column, which subsequently influences OC lateral transport and differential deposition. Easily suspendable terrestrial OC is concentrated in the upper 10 m of water or sea ice and transported to the Canada Basin, where it undergoes severe degradation of fresh carbon in the water column and uppermost sediments. In contrast, faster-settling marine OC is more likely to be buried in the canyons and at the Chukchi Shelf margin, with ice algae contributing about 14 % and 55 % of OC burial in areas south and north of 73°N, respectively, leading to higher initial burial efficiency. Increasing Arctic marine primary production could thus enhance the region's role as a carbon sink over millennial timescales, although the burial efficiency of terrestrial OC will eventually exceed that of marine OC with prolonged burial time. Our findings highlight the importance of lateral transport, differential deposition, and selective degradation in Arctic carbon burial, providing a basis for objectively assessing the future capacity of the Arctic carbon sink and its feedback to climate change.

Модели цепей поставок и их классификация

The article discusses various models of supply chains of goods. The classification and models of supply chains are considered. The basic concepts and elements of supply chain management are revealed. The theoretical basis of the article is research conducted in such fields of knowledge as logistics and supply chain management. Logistics supply chains are an important element in the activities of any company. They include the planning, production and management of goods, services and information from the point of origin to the point of consumption. Supply chains coordinate complex patterns of movement and transportation, shipment and receipt, import and export operations, warehousing, inventory management, procurement, production planning and customer service.