Yellow River Sediment Research Articles

Controls on Organic Carbon Burial in the Eastern China Marginal Seas: A Regional Synthesis

AbstractA regional synthesis of organic carbon (OC) burial was conducted using a comprehensive data set to reveal some of the key drivers and human multi‐stressors controlling OC burial and transport in the Eastern China Marginal Seas (ECMS). Both OC and Δ14C values of suspended particulate matter (SPM) in the Changjiang River, were significantly higher than estuarine mobile‐muds, suggesting selective decay of more labile younger OC from both marine and terrestrial sources and the accumulation of more recalcitrant older OC. Some of this decay is likely to be associated with iron‐redox cycling in mobile‐muds. In contrast, OC, δ13C, and Δ14C values increased along the Yellow River sediment dispersal pathway, indicating adding of young marine OC and less decay of terrestrial OC. OC burial efficiency in mud areas in the Bohai Sea (∼43%) was significantly higher than those in the Yellow (∼11%) and East China Seas (∼16%), owing to rapid deposition. Burial flux of biospheric OC in mud areas of the ECMS is 7.00 ± 0.79 Mt yr−1, corresponding to atmospheric CO2 drawdown by silicate weathering in major river drainage basins of mainland China. The burial flux of petrogenic OC was estimated to be 0.81 ± 0.25 Mt yr−1, accounting for >1.9% of total burial in the global ocean. While the ECMS is an important OC sink, river damming has greatly reduced OC burial. Thus, the overall impact on anthropogenically altered river‐dominated marginal seas remains an important and rapidly changing component of the coastal ocean carbon budget.

Sediment provenance and tidal current-driven recycling of Yellow River detritus in the Bohai Sea, China

A detailed sediment-provenance study is presented on the modern Bohai Sea, China, the innermost gulf of the Yellow Sea, using framework petrography, heavy-mineral and grain-size analyses. A series of subaqueous river deltas, characteristic of multisource, is distinguished along the coastal zone. First-cycle fluviodeltaic sediments are attributed principally to three large source areas: the Loess Plateau, the Yanshan highlands, and the Horqin sandland. Coastal sands along eastern Liaodong Bay are produced by weathering and physical erosion of near-source Mesozoic granitoid rocks during Quaternary lowstands. Apart from subaqueous deltas and coastal sands, sediment provenance is only attributed to two end-member mixing with various proportions between recycled Holocene Yellow River sediments and ancient fluvial sediments of the Liaohe river system, even though detrital sources are multiple along the coast. Relative contributions are quantified on a ternary diagram of heavy-mineral compositions, using the proportion of relative distances between a given mixed area and the two end-member deltas. The eastern Bohai flood-tidal delta, characterized by abundant garnet and ilmenite, is regarded as a large repository of ancient Liaohe sediments, which had been intermittently accumulated during Quaternary lowstands and reworked during multiple transgressions. As a secondary sediment source detached from the present-day Liaohe River delta, it is remobilized and involved in the modern sedimentation. A complete tidal current-dominated depositional pattern is proposed throughout the Bohai Sea to explain sediment accumulation and recycling. We suggest that dominant ebb tidal currents, prevailing in the southern Bohai Strait, are a primary driver carrying fine-grained Yellow River sediments eastward to the Yellow Sea. In contrast, the recycling of Yellow River sediments is driven by flood tidal currents, prevailing in the northern Bohai Strait. The internal recycling process in the Bohai Sea builds the sand sheet and its terminal lobe, i.e., the eastern Bohai mud belt, whereas the external recycling process that involves the depocenters of Yellow River sediments in the outside North Yellow Sea builds the sand ridges and its terminal lobe, i.e., the quartz-rich area. This study improves our understanding on the Yellow River dispersal system. It also provides a typical example that demonstrates how ancient alluvial sediments accumulated during eustatic lowstands are reactivated and join the modern sedimentation processes.

The variation and attribution analysis of the runoff and sediment in the lower reach of the Yellow River during the past 60 years

Abstract The water and sediment regimes of the Yellow River are the basis of decision-making of major projects of the Yellow River. Based on water and sediment data at the Huayuankou station, Gaocun station, Aishan station, and Lijin station in the lower reach of the Yellow River, the Mann–Kendall test, the T-test for differences, wavelet analysis, slope change ratio method and the double cumulative curve method were applied to analyze the runoff and sediment regime alteration. The results show that the water and sediment of the lower Yellow River have a significant downward trend, and the annual sediment decreases significantly compared with the annual runoff. The annual runoff and sediment of the four hydrological stations changed around the 1980s and 1990s, respectively. The water and sediment of hydrological stations have periodic variations on multiple time-scales, but the variation scales are different. Precipitation, human activities and other factors lead to the decreasing trend of water and sediment in the lower Yellow River, and their contribution rates to the change of water and sediment are also different. Precipitation contributed 0.15%–8.71% and 0.06%–22.32% to the reduction of runoff and sediment load at the hydrological stations, while human activities contributed 91.29%–99.85% and 77.68%–102.21% to the reduction of runoff and sediment load, respectively. Human activity is the main factor in runoff and sediment reduction.

Experimental Research on the Modification of the Yellow River Sediment

Experimental Research on the Modification of the Yellow River Sediment

Metals in sediments and their accumulation in Zostera japonica in different sediment habitats of the Yellow River estuary

This research aims to study the ecological risk of metals to Zostera japonica and focuses on two typical sediment environments in the Yellow River estuary, namely, sediment erosion and deposition areas. Two different sediment habitats of Z. japonica were selected in this research from southern and northern sites in the Yellow River estuary. The plant growth and nutrient and metal concentrations in the sediments and Z. japonica tissue were investigated in the growth period of Z. japonica from April to October 2019. The shoot height of Z. japonica was measured with a centimetre-scale measuring stick, and the dry shoot weight was obtained after drying at 70 °C for 24 h. The total carbon (TC) and total nitrogen (TN) concentrations in the Z. japonica tissue and sediment were determined with an elemental analyser (Vario Macro Cube, Elementar Company, Germany). The total phosphorus (TP), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), lead (Pb), chromium (Cr) and cadmium (Cd) contents in the digested solutions were measured by high-resolution inductively coupled plasma atomic emission spectrometry (HR-ICP-AES, Spectro Company, Germany). The growth of Z. japonica was different at the two study sites, with a higher biomass at the southern site than that at the northern site due to higher sediment nutrient concentrations at the southern site. The Cu, Zn, Pb, Cr and Cd concentrations in the sediments at the southern site were 25.1 μg g−1, 74.2 μg g−1, 21.4 μg g−1, 65.4 μg g−1 and 0.32 μg g−1, respectively, which were higher than the levels at the northern site of 13 μg g−1, 47.6 μg g−1, 12.4 μg g−1, 46.4 μg g−1 and 0.17 μg g−1, respectively. However, among the metals, only Cd was bioconcentrated in the Z. japonica tissue, with bioconcentration factor (BCF) values of 5.59 and 10.85 at the southern and northern sites, respectively. The sediments at the southern site in the estuary are composed of clays enriched in nutrients, thus supporting more sustainable growth and higher biomass than the coarse-particle sediments at the northern site in the estuary. Moreover, the sediments at the southern site were also enriched in metals, resulting in high levels of metals in the Z. japonica tissue. Overall, the ecological risk was low except for Cd, which should be considered because of its potential impacts on this seagrass and its related food webs in the estuary ecosystem.

Response of interrill erosion to flow parameters of sand loess in regions with high and coarse sediment yields

In the Loess Plateau, regions with high and coarse sediment yields are the main sources of the Yellow River sediments. The responses of the interrill erosion rate of the soil in this area (Shenmu soil) to flow intensity parameters were systematically investigated through indoor artificially simulated rainfall experiments considering five slope gradients (0.1564, 0.2079, 0.2588, 0.309, and 0.3584) and five rainfall intensities (60, 80, 100, 120 and 140 mm·h−1). Thereafter, an interrill erosion model was established based on two types of soil: Shenmu soil and Ansai soil. The experimental data of Ansai soil were obtained from a study by Wu et al. (2017). The results showed that for Shenmu soil, the interrill erosion mechanism can be classified into two types. The first type was detachment-limited interrill erosion in the initial rainfall phase and transport-limited interrill erosion in the subsequent rainfall. The other type was transport-limited interrill erosion during the entire rainfall duration. Among the flow intensity parameters (i.e., mean flow velocity (R2 = 0.92), shear stress (R2 = 0.84), stream power (R2 = 0.96), and unit stream power (R2 = 0.82)), stream power was found to be satisfactory for predicting the interrill erosion rate of Shenmu soil in terms of the coefficient of determination (R2). However, the interrill erosion rate model based on the stream power for the two types of soil exhibited low prediction accuracy. Furthermore, a general flow intensity parameter was derived to predict the interrill erosion rate of overland flow. Based on this parameter, an interrill erosion rate model for the two types of soil was formulated by multiple regression analysis with an R2 value of 0.96, a relative root mean square error of 18.9%, and a model efficiency of 0.94. Overall, this general flow intensity parameter was shown to be the preferred predictor for estimating the interrill erosion rate for steep slopes in the regions with high and coarse sediment yields.

Simulating cross-sectional geometry of the main channel in response to changes in water and sediment in Lower Yellow River

To understand the non-equilibrium morphological adjustment of a river in response to environmental changes, it is essential to (i) accurately identify how past conditions of water and sediment have impacted current morphological adjustment of the river, and (ii) establish a corresponding simulation for non-equilibrium conditions. Based on discharge and suspended sediment concentration (SSC) as well as 82 cross-sectional data items for the Huayuan-kou-Lijin reach of the Lower Yellow River in the period 1965–2015, the process of adjustment of the geometry of the main channel (area, width, depth, and geomorphic coefficient), and its responses to changes in discharge and SSC for different reaches are statistically analyzed. Following this, a delayed response model (DRM) of the geometry of the main channel subjected to variations in discharge and SSC is established using a multi-step analytical model, with the discharge and SSC as the main controlling factors. The results show that the area, width, and depth of the main channel decreased initially, then increased, decreased again, and finally increased again. These features of the geometry of the channel were positively correlated with the 4-year moving average discharge and negatively with the 4-year moving average SSC. The geomorphic coefficient for the Huayuankou-Sunkou reach exhibited a trend of decrease, whereas that of the Sunkou-Lijin reach decreased initially, then increased, decreased again, and finally increased again. Except for the Huayuankou-Gaocun reach in 1965–1999, the coefficient was negatively correlated with the 4-year moving average discharge and positively with SSC. The simulated values of the morphological parameters of the main channel for all sub-reaches obtained using the DRM agreed well with the measured values. This indicates that the DRM can be used to simulate the process of response of the cross-sectional geometry of the main channel to variations in the water and sediment. The results of the model show that the adjustment of the geometry of the main channel was affected by the discharge and the SSC at present (30%) as well as for the previous 7 years (70%). The proposed model offers insights into the mechanism whereby past water and sediment influence the current morphological adjustment of the river, and provides an effective method for predicting the magnitude and trend of the geometry of the main channel under different flow conditions.

11000-Year Record of Trace Metals in Sediments off the Southern Shandong Peninsula in the South Yellow Sea

Geochemical background values are the normal concentration of trace metals in the natural environment and sediment cores have been proved to be excellent samples to get these values. The trace metal (Cu, Pb, Zn, Cr, Cd, As, Hg, Ni, Li, and Co) concentration profiles along a sediment core are investigated to get the background values and to assess the depositional processes and contamination levels off the southern Shandong Peninsula, China. All the metals, except As and Hg, had similar concentration profiles with the highest average values during the period of 6 − 3 kyr. The high concentrations of As and Hg occurred before 6ka and during the period of 3 − 0 kyr. The difference in metal concentrations before and after 6 kyr was mainly attributed to the source of core sediments, which are derived from proximal sediment on the Shandong Peninsula before 6 kyr and the mixture of proximal sediment and Yellow River sediment after 6 kyr. The effects of particle size and human activity were mainly contributed to the metal concentrations since 6 kyr. The average concentrations of trace elements in sediments between 6 and 3 kyr were selected as background values. The principal component factor analysis indicate that the metals were from the natural sources throughout the observed depositional period, with the exception of As and Hg, which may had anthropogenic sources for the sediments from the bottom 2 m of the core. Their geoaccumulation indices indicate that the sediments were not contaminated for Cu, Zn, Cr, Cd, Pb, Ni, Li and Co, whereas they were contaminated recently for As and Hg due to the regional civilization and human activities.

Recent anthropogenic curtailing of Yellow River runoff and sediment load is unprecedented over the past 500 years

Recent anthropogenic curtailing of Yellow River runoff and sediment load is unprecedented over the past 500 years

Sediment budget of the Yellow River delta during 1959–2012, estimated from morphological changes and accumulation rates

The Yellow River (Huanghe) is a major sediment source of sediment to the Bohai Sea and Yellow Sea, resulting in the formation of a large and dynamic delta complex. However, the river sediment discharge reaching the delta has decreased dramatically since the middle 1960s. This study examines the sediment accumulation and morphological changes of the delta complex during 1959–2012 using a repeated bathymetry dataset, high-resolution seismic profiles, and sediment cores obtained in 2012 and 2013. Sediment accumulation rates were determined using the downcore concentrations of 137Cs and 210Pb. The average accumulation rates calculated for the delta complex range from 6.9–24 cm y−1 on the delta front slope, 1–2 cm y−1 at the toe of the slope, and < 1 cm y−1 in the northeastern shelf area. Morphological changes and sediment accumulation rates show that 1) the Yellow River delta has entered a destruction phase after 1996, 2) the amount of erosion of the whole delta reaches 210 MT y−1 of sediment, which is at least required to maintain the whole delta morphology, 3) three-quarters (487 MT y−1) of the Yellow River-derived sediment was deposited in the subaerial and subaqueous delta during 1959–2012, and 4) Whereas, one-quarter (144 MT y−1) was transported to the Bohai Sea, and as much as one fifth (117 MT y−1) was transported further offshore to the Yellow Sea, passing through the Bohai Sea during this period. The source of these sediments is a combination of the Yellow River sediment discharge and the erosion of the previous Yellow River delta lobes. Despite the sharp decline in the Yellow River sediment discharge over the past five decades, the offshore dispersal of the river discharge and eroded sediment to the Yellow Sea was more than 100 MT y−1 on average. Results of this study show that the erosion of the abandoned delta lobes can sustain the supply of sediment to remote offshore depocenters even after decades of declining river sediment discharge.

Brevibacillus migulae sp. nov., isolated from a Yellow River sediment sample.

Strain CFH S0501T, a novel Gram-stain-positive, aerobic, rod-shaped, endospore-forming and motile micro-organism with peritrichous flagella, was isolated from a sediment sample collected from the Yellow River in Henan Province, PR China. Optimum growth was observed at 28 °C, pH 7.0 and without NaCl. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that the strain belonged to the genus Brevibacillus and was closely related to Brevibacillus centrosporus DSM 8445T and Brevibacillus ginsengisoli Gsoil 3088T (with 96.8 and 96.7 % sequence similarity, respectively). The predominant menaquinone was MK-7. Major cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. Polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, two unidentified phospholipids and an unidentified polar lipid. The cell-wall peptidoglycan was found to contain meso-diaminopimelic acid. The genome size was 5.26 Mbp with a G+C content of 49.7 mol%. The average nucleotide identity (ANI) and in silico DNA-DNAhybridization (DDH) values between CFH S0501T and the other species of the genus Brevibacillus were found to be low (ANIm <86.11 %, ANIb <70.30 % and DDH <25.00 %). Based on physiological properties, chemotaxonomic characteristics and low ANI and DDH results, strain CFH S0501T is considered to represent a novel species, for which the name Brevibacillus migulae sp. nov. is proposed. The type strain is CFH S0501T (=DSM 29940T=BCRC 80809T).

Late Miocene Yellow River formation in Qingtongxia area, North China: Detrital zircon and heavy mineral analysis at Niushou Mountain, Ningxia

The development and formation times of the Yellow River, the second largest drainage system in China, remain controversial. The Ganhegou Formation, a set of Upper Miocene–Pliocene fluvial facies sediments, developed around Niushou Mountain in the outermost edge of the arcuate structural belt in the northeastern margin of the Tibetan Plateau and has a sediment composition very similar to that of the Yellow River. In this article, the relationship between the deposition of the Ganhegou Formation and the Yellow River is confirmed through the analysis and comparison of sediment composition, detrital zircons, and heavy mineral characteristics of the Ganhegou Formation, a Yellow River terrace, and the modern Yellow River. The sediments of the Ganhegou Formation contain abundant well‐ground and sorted fluvial pebbles that are largely consistent with Yellow River sediments. The analysis of the composition of zircons and heavy minerals shows that the age peaks of all detrital zircons are primarily among 200–300 Ma, 400–500 Ma, and 1,700–2,000 Ma and that all the heavy minerals are generally characterized by the combination of ‘haematite + garnet + zircon + epidote + quartz and altered minerals’. Therefore, the Ganhegou Formation in the Niushou Mountain area of Ningxia is a likely sediment of the ancient Yellow River, which has existed at Qingtongxia since at least the Late Miocene.

Human impact on suspended particulate matter in the Yellow River Estuary, China: Evidence from remote sensing data fusion using an improved spatiotemporal fusion method

Transport of suspended particulate matter (SPM) in estuarine waters plays an important role in regulating erosion-accretion and biogeochemical processes. In the Yellow River Estuary (YRE), artificial water and sediment regulation scheme (WSRS) and coastal engineering structures are the 2 typical anthropogenic activities affecting the spatiotemporal dynamics of estuarine SPM. The monitoring of SPM transport affected by such human activities requires SPM mapping at both high spatial and high temporal resolutions. In this study, we presented an improved Flexible Spatiotemporal Data Fusion (FSDAF) strategy with consideration of highly dynamic SPM variations in estuarine waters, and generated 30-m hourly SPM concentrations based on Landsat 8 OLI and GOCI datasets. The new strategy produced higher SPM estimation accuracy than the original FSDAF, with the relative percentage difference (RPD) decreasing from 29.75% to 5.31% using GOCI-derived hourly SPM as reference. With in situ SPM measurements as reference, the fused SPM concentrations had an RMSE of 12.09 mg/L and an RPD of 27.17%. Investigation of interday SPM variations before, during, and after the WSRS in 2018 revealed that the first WSRS significantly increased the SPM concentration and plume extent; new wetland with an area of 12.56 km2 was formed due to sediment accretion near the river mouth. The two groins offshore from the coastlines on the north and south sides of YRE exhibited obvious sediment trapping effects in that higher SPM concentrations on one side of each groin were found regardless of the turbidity modes and diurnal SPM variations; the trapping effects were associated with the number of groins and groin length. Intraday variations of SPM were influenced by tidal currents, with plume direction following the ebb and flooding tidal current direction. The inter- and intraday characteristics of the 30-m hourly SPM dynamics facilitate the detailed analysis of the sediment transport associated with human activities.

Recent anthropogenic curtailing of Yellow River runoff and sediment load is unprecedented over the past 500 y.

The Yellow River (YR) is the fifth-longest and the most sediment-laden river in the world. Frequent historical YR flooding events, however, have resulted in tremendous loss of life and property, whereas in recent decades YR runoff and sediment load have fallen sharply. To put these recent changes in a longer-term context, we reconstructed natural runoff for the middle reach of the YR back to 1492 CE using a network of 31 moisture-sensitive tree-ring width chronologies. Prior to anthropogenic interference that started in the 1960s, the lowest natural runoff over the past 500 y occurred during 1926 to 1932 CE, a drought period that can serve as a benchmark for future planning of YR water allocation. Since the late 1980s, the low observed YR runoff has exceeded the natural range of runoff variability, a consequence of the combination of decreasing precipitation and increasing water consumption by direct and indirect human activities, particularly agricultural irrigation. This reduced runoff has resulted in an estimated 58% reduction of the sediment load in the upper reach of the YR and 29% reduction in the middle reach.

Rapid monitoring of reclaimed farmland effects in coal mining subsidence area using a multi-spectral UAV platform.

In eastern China, coal mining has damaged a large amount of farmland, posing a great threat to food security. Backfilling with coal waste, fly ash, and sediments from rivers is an effective method to restore farmland. This study was conducted at the reclaimed area (RA) and the undisturbed area (UA) in Shandong Province, China. Soil and plant analyzer development (SPAD) of corn was selected as an indicator of crop growth. Multi-spectral data was obtained by the unmanned aerial vehicle equipped with a camera. By analyzing the correlation between SPAD and spectral bands, the common vegetation index is improved. Different regression methods were used to construct the SPAD inversion model. The distribution of corn SPAD was monitored to objectively evaluate reclamation technology. The results are as follows: (1) the vegetation index improved using the red-edge band has a higher correlation with SPAD, and the largest coefficient of determination (R2) value is 0.779; (2) the optimum inversion model for both jointing stage (R2 = 0.676) and milky stage (R2 = 0.661) is the linear regression model; the optimum model for both tasseling stage (R2 = 0.809) and filling stage (R2 = 0.830) is the partial least squares regression model; (3) the SPAD inversion map of RA and UA obtained by the optimum model shows that the corn grown in RA is slightly better than in UA. This study realized the rapid and efficient monitoring of the reclamation effects based on multi-spectral imagery and verified the feasibility of backfilling reclamation with Yellow River sediment in coal mining subsidence areas.

Magnetic evidence for Yellow River sediment in the late Holocene deposit of the Yangtze River Delta, China

Sediment source identification is critical for understanding delta evolution processes and for managing delta sustainability, particularly for deltas experiencing significant recent fluvial sediment discharge. Sediment sources for the Yangtze River Delta (YRD) are commonly assumed to be derived from the Yangtze River, despite the fact that the YRD is a tide-dominated delta that can receive marine-sourced sediments in addition to fluvial inputs. In particular, potential contributions from the neighbouring sediment-laden Yellow River, when it discharged into the Yellow Sea during 1128–1855 CE, remains unclear. Here we present provenance analysis of three cores from the northern YRD using size-specific magnetic characterizations. We find that magnetic properties of sediments younger than ~400 years have large differences among the studied cores. Comparison of magnetic properties to potential sources, including the major Yangtze River tributaries (i.e., Jinsha River, Jialing River, and Han River) and Old Yellow River (OYR), indicates that the northern core received enhanced Yellow River sediment loads over the last 400 years, while the southern core had a dominant Yangtze influence, which is most pronounced in size fractions less than 16 μm. This interpretation is supported by geochemical results. The documented spatial sediment source heterogeneity is caused by differences in tidal-fluvial interaction among delta distributary channels. Our results imply that the neighbouring OYR delta to the north exerts a remote influence on the YRD through longshore transport. This coastal connectivity between deltas should be assessed when forecasting future tide-dominated delta changes in the context of global change.

Quartz grain characteristics of the late Pleistocene hard clay in the Yangtze River delta and implications for sedimentary environment and provenance

AbstractThe sedimentologic fingerprinting in detrital deposit is vital to reconstruct sedimentary environments and discriminate sources. In this study, grain size and microtextural characteristics of quartz from the late Pleistocene hard clay in the Yangtze River delta (YRD) were analyzed by using a laser particle size analyzer and a scanning electron microscope. Subaqueous quartz from the Yangtze River and Yellow River sediments and eolian quartz from the Chinese Loess Plateau loess were also analyzed by scanning electron microscopy to obtain the microtextural characteristics. Quartz grains of the hard clay were characterized by poor sorting, fine skew, bimodal grain-size distributions, and numerous eolian microtextures. The comparison of the quartz grain characteristics of the hard clay with these in eolian loess indicated that the hard clay belonged to an eolian deposition. Moreover, the fine quartz grains of the hard clay were dominated by eolian microtextural characteristics, representing long-distance transportation. The coarse quartz grains of the hard clay exhibited more subaqueous microtextural characteristics, which indicated that the coarse fraction of the hard clay was derived from the proximal source regions in the YRD. The determination of buried eolian deposition with multiple sources in the YRD implies a southward westerly jet stream, strengthened eolian dust transportation, and extensive aridification in the YRD due to the increased Northern Hemisphere ice sheets in Marine Oxygen Isotope Stage 2.

Study on the Critical Dynamics of Compound Erosion in the Pisha Sandstone Area

The Pisha sandstone area which was distributed in Ordos of Inner Mongolia was the main source area of Yellow River sediment. The area has a characteristic of serious composite erosion and fragile ecological environment. So it is an important prerequisite to identify the critical force occurrence conditions of compound erosion for prevent and control the multiple composite erosion. Using the method such as field observation, simulation experiments and literature review, this study preliminarily summarizes the dynamic critical conditions and key influencing factors of water erosion, wind erosion and freeze-thaw erosion.

Historical change of carbon burial in Late Quaternary sediments of the ancient Yellow River delta on the west coast of Bohai Bay, China

The ancient Yellow River Delta (YRD) on the west coast of the Bohai Bay is possibly a huge carbon sink due to the high runoff and sediment load of the Yellow River, which transfers huge amounts of particulate carbon from terrestrial sources to the Bohai Sea. In this study, a 30.76 m long core (BXZK11), drilled in 2016, has been analyzed for AMS 14C dating, grain size, foraminifera, organic carbon (OC), total nitrogen (TN), and stable carbon isotope ratios (δ13C) to provide insights into the historical changes of carbon burial in Late Quaternary sediments of the ancient YRD. The results show that the sedimentary environments are divided into six depositional units in core BXZK11. The biggest contributor to organic carbon apparent mass accumulation rate (OCAMAR) is the negative covariance between apparent sedimentation rate (ASR) and OC. The average of OCAMAR is 20.76 g/(m2 yr) during the Holocene. The rates are highest in delta front deposits and lowest in shallow sea environments. Compared with the modern YRD, BXZK11 exhibits rather low ASR and OCAMAR, indicative of the enormous variations of Yellow River sediment load into the sea and the significant difference of carbon sequestration capacity of YRD at different periods. C3 plants of the delta wetland gradually develop without C4 plant input as the delta transgresses after sea level stabilization. The sediments have been characterized by decreasing terrestrial organic matter (TOM) since 6500 cal. a BP, reflecting the decline of Yellow River freshwater discharge. Both the 8.2 ka event and the weak Asian monsoon summer event at 6265 cal. a BP correspond well with the low TOM in BXZK11. The implication is that climate may affect the dynamics of carbon burial by regulating terrestrial inputs.

The Effect of Sedimentin Yellow River on Hydraulic Characteristics of Spray Sprinkler

The water shortage has become a great challenge for Yellow River irrigation regions; for the high level of suspended sediment in Yellow River, sprinkler irrigation, which has achieved superior anti-clogging performance, can be an effective solution for water conservation in agriculture management. For the direct utilization of the Yellow River water resource in irrigation land as irrigated by movable sprinkler irrigation systems, a series of experiments about the effect of sediment-water on the hydraulic performance of fixed spray plate sprinkler was conducted. The results showed that peak water precipitation rate appeared as both clean and sediment-water jetting from the groove, and the differences were that sediment-water minimized peak value of water application rate and increased wetted radius efficiently. The water distribution of an individual sprinkler resembled lotus shape with different working conditions, and the application rate nearby sprinkler increased with the increase insediment concentration, resulting in higher water distribution uniformity. In addition, sediment-water increased the spray distance remarkably with a maximum increasing ratio of 7.79%; meanwhile, it led to the transfer of peak application region to the edge of the wetted circle and, consequently, the wetted area increased. The calculation result of the water diffusion coefficient indicated that sediment-water contributed to splintering water jet effectively, but the analysis of variance showed that no significant change was obtained with increasing sediment concentration. All these results suggested that the sediment-water in Yellow River could be directly utilized in agriculture irrigation with superior hydraulic performance, and it would be helpful to protect and maximize the utilization of the Yellow River resource.