Sediment Flux Research Articles

Emissions and Atmospheric Dry and Wet Deposition of Trace Metals from Natural and Anthropogenic Sources in Mainland China

Trace metals from natural and anthropogenic sources impact the atmospheric environment and enter the soil through dry and wet atmospheric deposition, ultimately affecting human health. In this study, we established an emission inventory of Pb, As, Cr, and Cd in East Asia (80° E–140° E, 15° N–50° N) for the year 2017, including dust and anthropogenic sources from both land and marine. We modified the Community Multiscale Air Quality (CMAQ) model to provide gridded data on concentrations, as well as dry and wet atmospheric deposition fluxes of metals, with a focus on mainland China. The emissions of Pb, As, Cr, and Cd in East Asia were 19,253, 3415, 3332, and 9379 tons, respectively, in 2017, with 55%, 69%, 25%, and 58% distributed in the fine mode. The spatial distribution of atmospheric concentrations and dry deposition of trace metals was similar to that of emissions, while the spatial distribution of precipitation-related wet deposition was further east and greater in the south than in the north. In mainland China, the average bulk-deposition fluxes of Pb, As, Cr, and Cd were 1036.5, 170.3, 465.9, and 185.0 μg·m−2·year−1, respectively. Our study provides gridded data on trace metals in mainland China, which can be used for assessing air quality, human exposure risks, and metal inputs to soils.

The pace of global river meandering influenced by fluvial sediment supply

Meandering rivers move gradually across the floodplains, and this river movement presents socioeconomic risks along river corridors and regulates terrestrial biogeochemical cycles. Experimental and field studies suggest that fluvial sediment supply can exert a primary control on lateral migration rates of rivers. However, we lack an understanding of the relative importance of environmental boundary conditions, such as floodplain vegetation and sediment supply, in setting the pace of river meandering across different environmental settings. Here, we combine the analysis of satellite imagery and global-in-scale sediment and water discharge models to evaluate the controls on lateral migration rates of 139 meandering rivers that span a wide range in size, climate, and bank vegetation. We show that migration rates normalized by the channel width monotonically increase with the volumetric sediment flux normalized by the characteristic size of the river. This relation is consistent across rivers in vegetated and unvegetated catchments, indicating that enhanced lateral migration rates in unvegetated basins is likely not only facilitated by lower bank mechanical strength, but also by higher normalized sediment supply in ephemeral rivers. Using three case examples, we also demonstrate that width-normalized meander migration rates respond to spatial gradients in sediment supply caused by river impoundments, highlighting the prominent role of sediment supply in setting the pace of meander migration. Our results suggest that sediment-supply variations caused by climate, land-cover and land-use changes can lead to predictable changes in meandering river evolution and ultimately drive architectural changes in sedimentary stratigraphy.

Long-term trends and response of wet ammonia deposition to changes in anthropogenic emissions in the Pearl River delta of China

The Pearl River Delta (PRD) region has been identified as a significant hotspot of wet ammonium deposition. However, the absence of long-term monitoring data in the area hinders the comprehension of the historical trends and changes in wet NH4+-N deposition in response to emissions, which interferes with the ability to make effective decisions. This study has analyzed the long-term trends of wet NH4+-N deposition flux and has quantified the effect of anthropogenic emissions and meteorological factors at a typical urban site and a typical forest site in the PRD region from 2009 to 2020. It revealed a significant decreasing trend in wet NH4+-N flux in both the typical urban and forest areas of the PRD region, at -6.2%/year (p < 0.001) and -3.3%/year (p < 0.001), respectively. Anthropogenic emissions are thought to have contributed 47–57% of the wet NH4+-N deposition trend over the past 12 years compared to meteorological factors. Meteorological conditions dominated the inter-annual fluctuations in wet NH4+-N deposition with an absolute contribution of 46%–52%, while anthropogenic emissions change alone explained 10%–31%. NH3 emissions have the greatest impact on the urban area among anthropogenic emission factors, while SO2 emissions have the greatest impact on the forest area. Additionally, precipitation was identified as the primary meteorological driver for both sites. Our findings also imply that the benefits of NH3 emissions reductions might not immediately emerge due to interference from weather-related factors.

Spatial and temporal distribution of physicochemical parameters of water in Gorgan Bay (the southeast of the Caspian Sea - Iran): Fundamentals for the monitoring of the Caspian Sea coastal areas

Gorgan Bay as a main part of the Miankaleh (a natural biosphere reserve registered by UNESCO) is one of the richest ecological area in the West Asia and very important internationally recognized refuge for the wildlife. To date, multi physicochemical parameters have not been examined on a large scale. To fill this knowledge gap, the present study aimed to explore the seasonal and spatial variability of water quality parameters of the bay. The results showed that except for depth and transparency, there are significant variations in most parameters across the four seasons. The patterns of these changes in the bay vary, as evidenced by a comparison of the distribution maps of the various factors throughout the year. Notably, alkalinity declined from east to west, reaching its highest levels at important entry points such as the Qarasu River, Bandar-Gaz, and the pier. TDS, on the other hand, increased westward, reaching its highest concentration in the shallow western regions. Maximum depth (310 cm) and transparency (250 cm) were observed in the central bay. While the pH was higher in deeper areas, the distribution of PO4 was more uniform. With lower levels in the east (salinity = 0.40 ‰) and higher levels in the west (salinity = 28.9 ‰), the salinity showed a coherent gradient. Agricultural land use in the basin of the bay and fluxes of nutrients and sediments of the rivers entering the bay has significant contribution to the bay pollution situation. These results will serve as a guide for improving our understanding of the Gorgan Bay ecosystem. They also have implications for informed conservation and management plans adapted to the specifics of this special region within the Caspian Sea.

Performance evaluation of four sampling techniques and source apportionment for the atmospheric deposition fluxes of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are primarily emitted into the atmosphere through anthropogenic activities and can be transported to receptor sites at varying distances. In this study, the atmospheric PAH deposition was investigated using a dry deposition plate (DDP) with Mylar, a dry deposition disk (DDD) with Velcro, a resin bulk deposition sampler (Resin-BDS), and a water bulk deposition sampler (Water-BDS) in Ulsan, South Korea, during May–October 2013. Additionally, ambient PAH concentrations were monitored using high-volume air samplers. The mean deposition fluxes of Σ13 PAHs were 8.62 ± 1.44, 36.9 ± 6.81, 56.9 ± 9.74, and 63.8 ± 8.04 μg/m2/d for the DDP, DDD, Resin-BDS, and Water-BDS, respectively. The DDD was more effective than the DDP because it could collect high molecular weight (HMW) PAHs from dry deposition, which are more toxic than low molecular weight PAHs. The Water-BDS had the highest fluxes of Σ13 PAHs; however, the Resin-BDS may be more suitable for collecting HMW PAHs from both dry and wet deposition due to relatively constant values for the deposition velocity of PAHs. Furthermore, the PAH fluxes in the Resin-BDS samples were significantly positively correlated with the gaseous and total (gaseous + particulate) concentrations of ambient PAHs. Hence, the fluxes obtained by the Resin-BDS were further used to apply principal component analysis, multiple linear regression, and backward air trajectory simultaneously to identify the emission sources of the deposited PAHs. The results indicate that the combustion of fossil fuels and biomass was the major source. In particular, the industrial complexes using petroleum and coal on the city's east coast and vehicular exhausts were the main local sources. Meanwhile, long-range sources may be forest fires, harbors, and industrial activities in nearby countries. Our study suggests that BDS, considering both dry and wet deposition, can be selectively used for research on PAH deposition.

Mesoscale structure of the atmospheric boundary layer across a natural roughness transition

The structure and intensity of turbulence in the atmospheric boundary layer (ABL) drive fluxes of sediment, contaminants, heat, moisture, and CO[Formula: see text] at the Earth's surface. Where ABL flows encounter changes in roughness-such as cities, wind farms, forest canopies, and landforms-a new mesoscopic flow scale is introduced: the internal boundary layer (IBL), which represents a near-bed region of transient flow adjustment that develops over kilometers. Measurement of this new mesoscopic scale lies outside present observational capabilities of ABL flows, and simplified models fail to capture the sensitive dependence of turbulence on roughness geometry. Here, we use large-eddy simulations, run over high-resolution topographic data and validated against field observations, to examine the structure of the ABL across a natural roughness transition: the emergent sand dunes at White Sands National Park. We observe that development of the IBL is triggered by the abrupt transition from smooth playa surface to dunes; however, continuous changes in the size and spacing of dunes over several kilometers influence the downwind patterns of boundary stress and near-bed turbulence. Coherent flow structures grow and merge over the entire [Formula: see text]10 km distance of the dune field and modulate the influence of large-scale atmospheric turbulence on the bed. Simulated boundary stresses in the developing IBL counter existing expectations and explain the observed downwind decrease in dune migration, demonstrating a mesoscale coupling between flow and form that governs landscape dynamics. More broadly, our findings demonstrate the importance of resolving both turbulence and realistic roughness for understanding fluid-boundary interactions in environmental flows.

Multivariate analysis of inlet morphodynamics: The mixed sand-gravel ebb-tidal delta of Deben Estuary, Suffolk

The morphodynamics of inlets and ebb-tidal deltas often exhibit cyclic behaviour, controlled by wave-tide interactions and the influence of these on sediment-bypassing processes. Variation in the form and timing of inlet dynamics can occur in response to changes in the key sediment transport processes and sediment supply, and particularly the relative dominance of differential wave direction driving alongshore sediment transport. This paper investigates the morphodynamics of the Deben ebb-tidal delta through multivariate analysis of multi-annual bathymetry and metocean parameters covering the period 1991 to 2023. Results show that sediment bypassing and associated morphological change in this ebb-tidal delta follows variable behaviour mid-cycle, leading to change in the morphology and configuration of the ebb-delta from cycle to cycle. In the most recent cycle (since 2003), delta volume followed a stepwise growth driven by sediment influx periods, evident primarily in the updrift shoal, followed by cross-shore redistribution. Interannual variability in wave climate was clustered into four groups that capture the relative balance between the dominant NE and SW forcing. Sediment influx periods are mostly associated with subdued SW and increased NE forcing, but the summer and winter NE wave climate play different roles on the up- and downdrift, and upper and lower components of the ebb-delta system. Tide level has increased in the last 33 years, which is strongly correlated with ebb-delta volume increase. Wave and tide conditions have discrete and independent effects on the ebb-tidal delta, whereas wave-tide interactions do not significantly change these underlying influences.

A complex case of thermal maturity assessment in a terrigenous sedimentary system: The Northwestern Black Sea basin

An integrated approach combining fluorescence spectrometry, pyrolysis geochemistry, and dispersed organic matter (DOM) maceral analysis has been used to determine the thermal maturity of Oligocene source rocks in two neighboring offshore wells within the complex deep-sea system of the Northwestern Black Sea. The samples contain predominantly immature Type II kerogen, including a mixture of marine liptinite (alginite, liptodetrinite), degraded liptinite, primary vitrinite, and reworked vitrinitic macerals. The occurrence of several vitrinite reflectance (VRo) populations in the samples is attributed to a high influx of reworked vitrinite transported to the marine basin from multiple terrestrial sources with diverse degrees of degradation. The presence of multiple VRo populations complicates the application of VRo for determining the thermal maturity of the organic matter. Further, the VRo measurements on the primary vitrinite population show only a subtle increasing trend with depth. A significantly improved thermal maturity resolution was obtained using the red to green quotient (R/G). R/G was measured on the autochthonous unicellular Tasmanites-type alginite under UV-excitation. In contrast to VRo the results show a significant correlation between increasing R/G values with increasing depth. This indicates that the R/G quotient is a better maturity proxy for the studied low maturity marine system with a large influx of sediments. The beginning of the downward declining trend in the temporal variation of liptinite is regarded as the onset of catagenesis. This occurs at a burial depth of 2.5 km and a R/G value of 0.50, corresponding to a VRo equivalent (VRo Eq) of 0.44%. At a burial depth of 3.2 km and a R/G value of 0.57 (VRo Eq = 0.57%), the onset of the oil window is marked by an increase in the amount of solid bitumen (initial oil solid bitumen). The observed alterations in maceral composition with burial depth align with the thermal maturity of the wells. However, the data suggest that the thermal evolution of the organic matter is out of sync with the surrounding formation temperature, possibly due to rapid burial induced by a high sedimentation rate.

Refining the roles of productivity, redox, and remineralization on the cadmium isotope composition of marine sediments

Cadmium (Cd) has a nutrient-like distribution in the ocean, similar to the macronutrient phosphate. Significant isotope fractionation induced by the biological cycling of Cd makes it a potential tracer for nutrients and productivity. However, the Cd flux and Cd isotope composition of marine sediments may also be influenced by local redox conditions and partial remineralization of organically hosted Cd. These confounding factors are under-constrained and render it challenging to use Cd as a reliable paleoproxy. To understand the relative importance of each of these processes, we examined the Cd isotope systematics of 69 modern sediments deposited across a wide range of environments. We complement these data with four profiles of particulate Cd isotope compositions from the Southern Ocean. We report three main results. First, we show that the sedimentary flux of Cd is tightly coupled to that of organic matter. Second, most Cd burial occurs in regions with some bottom-water oxygen, and the flux of CdS to anoxic regions is, globally, minor. Finally, we find that remineralization can substantially modify sedimentary Cd isotope compositions, though it is challenging to relate pelagic and sedimentary processes. For example, we find that the relationship between sedimentary Cd isotope compositions and surface seawater [Cd] is the reverse of that predicted by isotope reactor models. Likewise, sedimentary Cd isotope compositions are anti-correlated with bottom-water oxygen. While this pattern is consistent with preferential remineralization of isotopically heavy Cd, profiles of marine particulate matter reveal the reverse, whereby the Cd isotope composition of large particles, which are most likely to reach the seafloor, becomes increasingly ‘heavy’ with depth. These results highlight how productivity, redox, and remineralization all influence the flux and isotope composition of Cd to marine sediments. While our study suggests that there is no simple way to relate sedimentary Cd isotopes to surface nutrient utilization, our data point toward several potential controls that could form the basis of novel proxies for local redox conditions and remineralization.

System-scale dynamics of long-term sediment and phosphorus accumulation in contrasting valley-bottom wetlands in dryland landscapes of South Africa

Anthropogenic-induced acceleration of sediment and associated nutrients presents a serious challenge to water resource management across the globe. While wetlands are potential natural solutions, little is known of how well key wetland types attenuate downstream sediment fluxes and how these relate to local- and catchment-scale factors. This research aimed to develop an understanding of patterns and rates of sediment and phosphorus retention in valley-bottom wetlands in South Africa. The geomorphology, sedimentology and historical accretion rates of three wetlands which offered diversity in size, catchment position and degree of organic accumulation were compared to ascertain the impact of local- and catchment-scale factors. Estimates of sediment and associated phosphorus accumulation suggest higher rates in clastic sediment-dominated wetlands (1089–7655 g sediment m−2 yr−1, 0.4–1.6 g-P m−2 yr−1) compared to an organic sediment-dominated system (601–1308 g-sediment m−2 yr−1, 0.2–0.3 g-P m−2 yr−1). Sediment accretion rates generally increased longitudinally, indicating that distal wetland reaches act as sediment and phosphorus retention hotspots. Phosphorus distribution patterns were primarily attributed to variations in organic matter content and associated aluminium and iron complexing agents in fine-grained sediment deposits, while particle size distributions were less important. However, the relevance of individual complexing agents in phosphorus dynamics varied among wetlands with differing landscape conditions. Contrasts between these systems reflect variations in catchment lithology and hydroclimatic regime, which influence the relative magnitude of sediment supply and vegetation productivity. We postulate that intermediate-sized wetlands characterised by catchments around 900 ha in size, gentle longitudinal slopes (∼2 %), a high proportion of fine sediment deposition, limited organic matter breakdown, and a long vegetation growing season provide optimal conditions for sediment and phosphorus accumulation. This system-scale information is essential to guide management decisions to identify and prioritize within-catchment ‘hotspots’ of sediment and phosphorus retention.

Carbon wet deposition flux and river carbon output in a forest watershed in permafrost region of the Da Xing'an Mountains.

Carbon wet deposition and river carbon output in river basins are important components of global carbon cycle. The assessment of both properties is of great significance for regional carbon budget. However, research on these topics in high-latitude permafrost regions in China is still lacking. We conducted dynamic monitoring of carbon wet deposition and carbon output in the river from May 28th to October 30th, 2022, in Laoyeling watershed, a typical forested watershed in the Da Xing'an Mountains permafrost region. We analyzed the variations of carbon component concentrations and fluxes in precipitation and river water, and estimated the contribution of carbon wet deposition to carbon output in the watershed. The results showed that wet deposition fluxes of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total dissolved carbon (TDC) in the Laoyeling watershed were 1354.86, 684.59, and 2039.45 kg·km-2, respectively. The fluxes of DOC, DIC, TDC, particulate organic carbon (POC), particulate inorganic carbon (PIC), and total carbon (TC) in the river were 601.75, 1977.30, 2579.05, 125.13, 21.99, and 2726.17 kg·km-2, respectively. The contribution of TDC wet deposition to the river TDC output was 9941.89 kg, accounting for 17.6% of total output. The DIC concentration in the river showed significant seasonal differences, with increased runoff resulting from precipitation leading to a decrease in DIC concentration in the river and showing a clear dilution effect, while the concentrations of DOC, POC, and PIC increased, mainly due to erosion effect. In conclusion, carbon wet deposition flux in the Laoyeling watershed was mainly determined by precipitation, and its contribution to river carbon output was relatively small compared to other factor. Runoff was the dominant factor affecting river carbon output. The results would provide important insights into carbon cycling and carbon budget balance in permafrost regions under climate change.

Leaf-Level Bidirectional Exchange of Formaldehyde on Deciduous and Evergreen Tree Saplings.

Gas-phase formaldehyde (HCHO) is formed in high yield from the oxidation of many volatile organic compounds (VOCs) and is commonly used as a constraint when testing the performance of VOC oxidation mechanisms in models. However, prior to using HCHO as a model constraint for VOC oxidation in forested regions, it is essential to have a thorough understanding of its foliar exchange. Therefore, a controlled laboratory setup was designed to measure the emission and dry deposition of HCHO at the leaf-level to red oak (Quercus rubra) and Leyland cypress (Cupressus × leylandii) tree saplings. The results show that HCHO has a compensation point (CP) that rises exponentially with temperature (22-35 °C) with a mean range of 0.3-0.9 ppbv. The HCHO CP results are also found to be independent of the studied tree species and 40-70% relative humidity. Given that HCHO mixing ratios in forests during the daytime are usually greater than 1 ppbv, the magnitude of the CP suggests that trees generally act as a net sink of HCHO. Additionally, the results show that HCHO foliar exchange is stomatally controlled and better matches a reactivity factor (f0) of 0 as opposed to 1 in conventional dry deposition parametrizations. At 30 °C, daytime HCHO dry deposition fluxes are reduced by upward of 50% when using f0 = 0 and a nonzero HCHO CP, although deposition remains the dominant canopy sink of HCHO. A reduced deposition sink also implies the increased importance of the gas-phase photolysis of HCHO as a source of HO2.

Spatio-temporal variations of methane fluxes in sediments of a deep stratified temperate lake

Spatio-temporal variability of sediment-mediated methane (CH4) production in freshwater lakes causes large uncertainties in predicting global lake CH4 emissions under different climate change and eutrophication scenarios. We conducted extensive sediment incubation experiments to investigate CH4 fluxes in Lake Stechlin, a deep, stratified temperate lake. Our results show contrasting spatial patterns in CH4 fluxes between littoral and profundal sites. The littoral sediments, ∼33% of the total sediment surface area, contributed ∼86.9% of the annual CH4 flux at the sediment-water interface. Together with sediment organic carbon quality, seasonal stratification is responsible for the striking spatial difference in sediment CH4 production between littoral and profundal zones owing to more sensitive CH4 production than oxidation to warming. While profundal sediments produce a relatively small amount of CH4, its production increases markedly as anoxia spreads in late summer. Our measurements indicate that future lake CH4 emissions will increase due to climate warming and concomitant hypoxia/anoxia.

Semi-quantifying vertical sedimentary succession and microfacies characterization from a delta system in a lacustrine basin, Huangqihai Lake, North China

The formation of vertical sedimentary succession of a delta in the arid and semi-arid basin-margin progradation dramatically depends on the variation of sediment flux and accommodation, but the discontiguous record of signals tends to exist enormously variable, which renders the bulk record of microfacies difficult to quantify from the vertical sedimentary succession. We analyzed the 18 vertical sedimentary successions collected from 18 field trenches of a lake delta by the cusp-catastrophe model, allowing detailed mapping of microfacies. The present detailed study indicates the suitability of cusp-catastrophe theory for explaining vertical sedimentary succession in the BWH (Bawanghe) delta. Three equilibrium states of processes responsible for the deposition of the BWH delta's evolution were established: sandy-dominated upper leaves primarily exhibit the delta plain; sandy/muddy-dominated lower leaves present the delta plain and pro-delta; and sandy-dominated middle leaves which commonly developed the delta front. The result of analysis shows that the reliability of the cusp-catastrophe model to identity mutation of vertical sedimentary succession exceeds 50 %, and to identity microfacies transitions with a precipitation periodicity exceeds 70 %. These cognitions support the previous view that changing precipitation results in an abrupt change in margin progradation. Simultaneously, the study gives new insights into the microfacies quantification of lake deltas and reveals the influence of crest value changes of precipitation on vertical sedimentary succession can be understood from the dependence of microfacies distribution on the change of sediment flux and accommodation.

Application of the tidally averaged equilibrium cohesive sediment concentration for determination of physical parameters in the erosion-deposition fluxes

A puzzling fact for the Partheniades-Krone formula is the adoption of very contrasting values for the empirical parameters (e.g., the erosion coefficient and the critical shear stresses) but satisfactory reproduction of the suspended sediment concentration (SSC). Here, a theoretical equation for the tidally-averaged equilibrium (TAE) condition is derived by setting the integrated erosion flux throughout a tidal period equivalent to the integrated deposition flux throughout the same tidal period, leading to a new constraint condition on these parameters if values of the TAE-SSC are available. A preliminary check using the measured data of the Yangtze Estuary shows that a larger critical shear stress for erosion would require a smaller critical shear stress for deposition, both of which must be enhanced if the erosion coefficient further increases. Contrasting sets of parameter values derived by this constraint are fed into a coupled hydro-sediment-morphodynamic model to simulate cohesive sediment transport in the Yangtze Estuary. The results confirm that very contrasting parameter values can indeed lead to satisfactory reproduction of the temporal variations of the SSC (e.g., those in July 2016, including both spring tide and neap tide). This is further demonstrated by the numerical modelling of cohesive sediment transport in an idealized symmetrical estuary. These results indicate that the TAE condition can be used as a constraint for determining the erosion coefficient and the critical shear stresses for erosion and deposition. In addition, two simplified equations of the bed sediment mass conservation (no erosion version and the no deposition version) are derived as complements for obtaining a unique set of the three parameter values, provided that the simultaneous measured time series of SSC, bed shear stress and bed level can be collected at the same gauging station.

Impact of large wood on sediment (dis)connectivity in a meandering river

Large wood (LW) can exert strong influence on sediment storage patterns in fluvial systems. However its specific impact on sediment routing is largely dependent on the stability of individual LW pieces or LW jams. We used sediment (dis)connectivity principles to quantify the impact of LW on sediment erosion and storage along a meandering river reach. Decadal spatiotemporal changes of LW and fluvial landforms are appraised along a 3.65 km long reach of the Odra River (Czechia). Detailed orthophotos at two-year intervals from 2012 to 2022 are analysed alongside field inventories. During this study period, there was a single flood event with a 5–10-year recurrence interval, and three smaller flow events with a recurrence interval of up to 2 years. We assessed the sediment deposition, bank protection, and erosion effects of LW, finding that the impact of LW on decelerating sediment fluxes was more pronounced. Specifically, LW-related deposition varied between 13.6 m2 and 36.7 m2 per 100 m of channel length during the individual two-year periods. In contrast, we detected only 0.5 m2 to 7.8 m2 per 100 m of channel length of newly eroded material during the same periods. Additionally, 6.3 % to 7.8 % of the lengths of the outer meander bends were protected by persistent LW elements against erosion during these two-year periods. Finally, we developed a three-stage conceptual model depicting the impact of LW on sediment (dis)connectivity in a meandering river at different relative timescales. Our model accounts for the dependence of interactions between LW and fluvial sediments based on the LW stability and frequency-magnitude of the hydrogeomorphic processes. In general, our observations suggest that the presence of stable LW in meandering rivers primarily leads to the deceleration of the lateral and longitudinal dimensions of sediment (dis)connectivity.

Crop‐ and weather‐dependent yield and wind erosion benefits from a conservation practices system

AbstractWind erosion and variable weather challenge crop production in the northern Great Plains. Management that increases residue cover might mitigate wind erosion during the cash crop growing season. We evaluated horizontal sediment flux (modified Wilson and Cooke samplers) and cash crop yield across a single rotation of corn (Zea mays L.)–soybean (Glycine max (L.) Merr.)–spring wheat (Triticum aestivum L.) in paired fields with contrasting management. One field included cover crops and retained spring wheat straw (aspirational), while the other excluded both conservation practices over the 3‐year rotation (business‐as‐usual). Horizontal sediment flux rapidly decreased with days after cash crop planting (increasing crop canopy), regardless of management treatment. In 2 years (2020 corn and 2022 spring wheat), there was greater horizontal sediment flux, lower cash crop grain yield, and lower cash crop aboveground biomass in the aspirational versus business‐as‐usual field. In 2021 soybean, there was lower horizontal sediment flux, greater cash crop yield, and greater cash crop aboveground biomass in the aspirational versus business‐as‐usual field. Higher yield and lower horizontal sediment flux responses corresponded with the management treatment that produced the higher cash crop aboveground biomass. Additionally, our short‐term study indicated that in drought years, cover crops worsened the adverse effects of abnormally low precipitation on yield and biomass of 2020 corn but not 2021 soybean.

β''-Al2O3 protecting layer for stable zinc metal anodes

Aqueous zinc-ion batteries (AZIB) has attracted considerable attention on account of its low cost, high security and environmental friendliness. Nevertheless, the growing dendrites and corrosion reactions on the surface of zinc anode limit the development of AZIB. Herein, β''-Al2O3 with high ion conductivity was firstly employed as an efficient artificial layer for stabilizing the zinc anode. The optimized β''-Al2O3 layer enables homogeneous ion flux and uniform zinc deposition, significantly suppressing dendrite growth and parasitic reactions. Symmetric cells based on this unique protective layer can stably operate for 1600 h under 1 mA cm−2/1 mAh cm−2. Benefiting from the high-performance zinc metal anode, the full cell paired with the NH4V4O10 cathode delivers a high discharge initial capacity of 400 mAh g−1 at 1 A g−1 and good cycling stability. This simple protecting layer provides a new strategy for the modification of zinc metal anode and accelerates the practical application of AZIB.

Morphodynamics and depositional architecture of mid‐channel bars in large Amazonian rivers

AbstractLarge rivers are characterized by large water discharges, high suspended sediment fluxes and low slope, and typically display multiple channels that are separated by large complex bars. The most common channel style found in these rivers is characterized by the alternating presence of single and multiple channel threads. Mid‐channel compound bars separate a main deeper channel from shallower secondary channels, leading to low‐order braiding and low to moderate sinuosity. Despite the importance of this type of river for global terrestrial sediment transport and the interpretation of ancient fluvial successions, integrated depositional models for large multi‐channel rivers are still not fully developed. This paper interprets the channel morphodynamics and depositional architecture of such large rivers by investigating the distinctive features of their laterally‐accreting mid‐channel bars in the Solimões–Amazonas River. This is achieved by examination of temporal series of satellite images, quantification of bedforms using multibeam echosounding surveys, analysis of shallow seismic and ground penetrating radar surveys of selected areas, and on‐site field observations and sample collections. Such mid‐channel bars produce directional variability in planform scroll bar accretion of up to 180°. As these bars – and their associated channels – evolve, they become progressively shallower, due to the bifurcation of the two channels and the resultant partitioning of discharge that leads to a gradual reduction in transport capacity within the outer channel. The preserved successions of this process in the alluvial plain are characterized by fining‐upward trends, with larger cross‐strata sets at mid‐depths and internal erosional surfaces marking distinct cycles of bar development with potentially differing palaeocurrent trends. The new depositional models proposed for these mid‐channel bars and channels constitute a basis for the recognition of large multi‐channel river deposits in the ancient rock record.

Atmospheric microplastic deposition associated with GDP and population growth: Insights from megacities in northern China

Microplastic (MP) pollution is evolving into one of the most pressing environmental concerns worldwide. This study assessed the impact of economic activities on atmospheric MP pollution across 17 megacities in northern China, analyzing the correlation between the deposition flux of atmospheric MPs and variables such as city population, gross domestic product (GDP), and industrial structure. The results have shown that the MP pollution is obviously impacted by human activities related to increased GDP, population, as well as tertiary service sector, in which the MP pollution shows most close relationship with the GDP growth. Polypropylene, polyamide, polyurethane, and polyethylene were identified as the primary components of atmospheric MPs. The average particle size of MPs in atmospheric dustfall is 78.3 µm, and the frequency of MP particles increases as the particle size decreases. The findings highlight the complex relationship between socio-economic development and atmospheric MP accumulation, providing essential insights for the formulation of targeted emission reduction strategies.