Sediment sources and their impacts on a check dam-controlled watershed, Loess Plateau, China

Soil erosion is a major issue in Loess Plateau,China,and quantitative analyses of sediment sources are crucial for soil erosion control.In this study,a combination of flood couplet analysis and composite fingerprint identification was used for historical reconstructions of soil erosion in sediment source areas in Loess Plateau.Each flood couplet was constructed based on sediment 137Cs activity,and past soil erosion was calculated using soil bulk density and storage capacity curves.The contribution rates of the sediment sources were calculated using the fingerprinting method,and the amount of erosion in the sediment source areas was estimated.The best fingerprint combination(Cr,Ni,V,and TOC)enabled a 97.2%recognition of sediment sources from 29 flood events(1956–1990)in the Loess Plateau.The contribution rates of gullies,farmland,grassland,and shrubland were 44.89%,26.38%,10.49%,and 18.24%,respectively.These four land use types contributed 1,227,751,512,and 279 tons of sediments,respectively.Re-vegetation decreased soil erosion(1966–1983),whereas deforestation increased soil erosion(1956–1965 and 1984–1990).Rational soil and water conservation measures on slopes and check dam construction in gullies are therefore suggested to mitigate erosion.

Using Natural Radionuclides to Trace Sources of Suspended Particles in the Lower Reaches of the Yellow River

Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and desorption.We analyzed the activi-ties and distribution characteristics of multiple natural radionuclides(238U,226Ra,40K,228Ra,7Be and 210Pbex)on size-fractionated SPM at the Lijin Hydrographic Station(Huanghe or Yellow River)every month over a one-year period.Results showed that medium silt(16–32µm)was the main component.As expected,the activity of each radionuclide decreased with an increase of particle size.We examined the sources of SPM with different particle sizes using activity ratios of 226Ra/238U,228Ra/226Ra,40K/238U and 7Be/210Pbex,and concluded that SPM with different particle sizes originated from different sources.Our results indicate that fine SPM(<32µm)was mainly from the erosion of soil along the lower reaches of the Yellow River,while coarse SPM(>32µm)was mainly derived from resuspension of riverbed sediment.During high runoff periods,the concentration of SPM increased significantly,and the pro-portion of fine particles originating upstream increased.Naturally occurring radioactive isotopes,especially on size-fractionated par-ticles,are therefore seen as useful tracers to understand the sources and behaviors of riverine particles transported from land to sea.

Sources of sediment in tidal flats off Zhejiang coast,southeast China

The growth of tidal flats off Zhejiang coasts in southwestern China has provided substantial areas for local agriculture and construction activities.To evaluate modern and future development of tidal flats in the region,a good understanding of sediment sources is necessary.Previous research has concluded that the Changjiang(Yangtze)River is the dominant supplier of sediments to this part of the southeast Chinese coast,despite the fact that sediment delivery from this source has been decreased markedly in the past two decades.In this study,we investigated the sources of tidal flat sediments,and the magnetic and geochemical properties of recent tidal flat sediments along the Zhejiang coast were compared with those discharged from rivers.Magnetic and geochemical properties of the tidal flat samples reveal statistically distinct sediment provenance groups.The magnetic and geochemical scatter plots show that the suspended sediment samples are naturally divided into two different groups,one including the Changjiang River and Qiantang River material,and the other including the Jiaojiang,Oujiang,and Feiyun Rivers that located in the central and southern parts of the study areas.At last,a binary source of tidal flat sediments along the Zhejiang coast was determined,with the substantial majority originating from local rivers,while a much smaller proportion emanates from the Changjiang River to the north.We conclude that the sediment contribution of the Changjiang River to tidal flat development in the region has been markedly overestimated,with important implications for management.

Sediment source-to-sink process variations of sandy-muddy transitional beaches and their morphological indications

The clay mineralogy of 28 sandy-muddy transitional beach(SMT-Beach)sediments and surrounding mountain river sediments along the coasts of southeastern China was systematically investigated to reveal the sediment source-to-sink process variations of such beaches and their morphological indications.The results show that the clay mineral assemblages of these SMT-Beaches mainly comprise of almost equal illite(~30%),kaolinite(~28%),chlorite(~22%),and smectite(~20%)contents.From the surrounding mountain rivers to the SMT-Beaches,clay mineral assemblages show distinct spatial changes characterized by a large decrease(~40%)in kaolinite,whereas the other three clay minerals present relative increases,especially clear for smectite.The muddy sediment sources of SMT-Beaches inferred from the clay mineralogy are mainly derived from nearby mountain rivers coupled with long-distance transport and penetration of the Changjiang River.The sandy sediments of these beaches are predominantly sourced from nearby mountain rivers,the weathering products of surrounding rocks in both mainland and island environments,and erosion of the“Old Red Sand”and“Red Soil Platform”.However,the sandy sediment sources of the SMT-Beaches are largely reduced because of the remarkable decrease in the river fluvial supply associated with intensive human activities such as dam construction and coastal reclamation.Subsequently,the sandy sections of SMT-Beaches present clear erosion and have revealed by both time series remote sensing images and a compilation of published literature.In contrast,the muddy sediment supply of SMT-Beaches is temporarily stable and relatively constant,resulting in the landward migration of the mudflats with relative transgression or accumulation.These findings highlight that the natural evolution processes of SMT-Beaches have been greatly reshaped by intensive human activities.

Distribution and dispersal pattern of clay minerals in surface sediments,eastern Beibu Gulf,South China Sea

Clay minerology of sediments are useful in determining distribution, sources and dispersal routes of fine-grained sediments. In the present paper, clay minerals of surface sediments throughout the eastern part of Beibu Gulf has been investigated to reveal sources and transport of detrital fine- grained sediments. Four distinct clay mineral suites were observed from cluster analysis of clay mineral compositions of the samples. From the distribution pattern of clay minerals, we conclude that kaolinte in the eastern gulf is mainly derived from South China Landmass; Smectite could not be transported mainly by surface current from north-western Hainan Island, and maybe minor portion of it from Red River; Illite is mainly transported by the currents fl＇om South China Sea. Chlorite has two sources, namely South China Sea and South China Landmass. The Zhujiang River derived sediments could not be one of the sources for the clay mineral here, because of very different composition and ratios. The distribution pattern of clay minerals in the eastern Beibu Gulf is mainly controlled by fine-grained sediment source and local currents. The Silt/Clay, Smectite/Kaolinte, and Smetite/（Chlorite＋Illite） ratios could be used as indicators of fine-grained sediment dispersal in the gulf.

The sedimentation rates in the Okinawa Trough during the Late Quaternary

On the basis of accelerator mass spectrometer radiocarbon （AMS ^14C） dating, sedimentation rates of 11 cores collected from the northern to southern Okinawa Trough are discussed. The sedimentation rates in the Okinawa Trough roughly range from 11 to 39cm/ka, and the average is 23.0cm/ka. China＇s continental matter is the main sediment source of the middle Okinawa Trough and has important contribution to the northern and southern Okinawa Trough. The sedimentation rates during the marine oxygen isotope （MIS） 2 are uniformly higher than those during MIS 1 in the northern and middle Okinawa Trough while they are on the contrary in the southern Okinawa Trough. Sedimentation rates in the Okinawa Trough can be one of the proxies of sediment source and an indicator of cooling events.

Distribution of gamma-ray radionuclides in surface sediments of the KongsQorden, Arctic: Implications for sediment provenance

The Kongsfjorden is highly sensitive region to climate variability,however,the study of gamma-ray radionuclides in related areas is relatively scarce.In this study,the grain size,total organic carbon(TOC),13 Corg isotopes,and specific activities of seven gamma nuclides were analysed in surface sediments of the Kongsfjorden in the Arctic during the summer of 2017.The specific activities of 210 Pb_(ex),137 Cs,238 U,226 Ra,228 Ra,228 Th,and 40 K were 12–256 Bq/kg,0–3.8 Bq/kg,25–42 Bq/kg,24–38 Bq/kg,22–40 Bq/kg,22–40 Bq/kg,and 354–738 Bq/kg,respectively,with average values of(121±94)Bq/kg,(2.0±1.2)Bq/kg,(34±6)Bq/kg,(32±4)Bq/kg,(32±6)Bq/kg,(33±6)Bq/kg,and(611±119)Bq/kg.This study observed a significant positive correlation(r=0.845,p<0.05)between TOC and 210 Pb_(ex),highlighting the strong influence of organic matter on the distribution of 210 Pb_(ex).The boundary scavenging of210 Pb from the open sea contributed 27.5%–46.2%to the total 210 Pb_(ex) in the sediments of the outer Kongsfjorden.The grain size was an important factor affecting the activity distribution of several radionuclides(238 U,228 Ra,228 Th,226 Ra,and 40 K).The specific activity of 137 Cs indicated the transport of terrestrial materials from the exposed area of the Kongsfjorden.The sediments in the Kongsfjorden were derived from various material contributions of glacial meltwater debris,glacial rivers,bare soil,atmospheric deposition,and marine sources.This study explains the source of the Kongsfjorden sediment and the distribution characteristics of radionuclides,and illustrateas the main factors affecting the distribution of radionuclides,which provides a reference for the behavior of polar radionuclides in future research.

Radiolaria fossils in the surface sediments and sedimentary environment in the Bering Sea

Totally 2472 grains of Radiolaria belonging to 36 Genera and 45 species are distinguished from 12 surface sediments in the Bering Sea. The distribution characteristics of Radiolaria fossils in the surface sediments are as follows: (1) From the shelf of shallow water to the upper of continental slope, there are a few Radiolaria fossils and monotonous genus and species; (2) In the lower of continental slope, Radiolaria fossils are poor in the volcanic cinders and turbidite; (3) The abundance and diversity of Radiolaria fossils are high in clay of the basin. The dominant species of Radiolaria is Spongotrochus glacialis on the continental shelf. Current, topography, water depth, and temperature etc. are key factors influencing Radiolaria distribution. The sources of sediments mainly are terrigenous, biogenic and volcanic sediments in the survey area and they are mostly from the Kamchatka peninsula in the east of Russia and the Aleutian Islands.

Source identification of aluminum in surface sediments of the Yellow Sea off the Shandong Peninsula

Surface sediment samples in the near shore area of the north Shandong Peninsula are collected for grain size and element analyses. The results indicate that the surface sediments in the study area are primarily composed of the silt-sized components similar to the Huanghe River. The total concentration of aluminum varies from 5.57% to7.37%（average（6.33 ± 0.40）%）, and its spatial distribution is mainly controlled by the grain size. Correlations between the ratio of aluminum to titanium concentration and aluminum concentration, titanium concentration and the mean grain size indicate that aluminum in the near shore surface sediments is affected majorly by the terrigenous source, and partially by the anthropogenic source. The ratios of aluminum to titanium concentrations are larger than the background value of loess matter at some stations due to the existence of excess aluminum associated with human activities. Thus, the sources of aluminum should be identified firstly when aluminum is used as an index of terrigenous matter even in the near shore area dominated by terrigenous deposits.

The source of heavy metals and its indication to the sediment transfer in the Hangzhou Bay

-Suspended matters are important carriers of heavy metals in the hydrocycle.In this paper, the field investigation , lab. experiment and 'corresponding analysis' were made to study sources of the heavy metals and the transfer of suspended matters from the Hangzhou Bay.This conclusion shows that the contents of heavy metals in this area are the natural background values ; the distributions of heavy metals are controlled by the plume front.

Novel sediment source fingerprinting quantifying erosion-induced total nitrogen and total phosphorus outputs from an intensive agricultural catchment,North China

Intensive farming is a primary cause of increased sediment and associated nitrogen(N)and phosphorus(P)loads in surface water systems.Determining their contributing sources,pathways and loads present major challenges in the high-intensity agricultural catchments.Herein,we quantify the sediment sources and magnitude of sediment total N and total P from different sources using a novel application of compound-specific stable isotope(CSSI)and fallout radionuclides(FRNs)of^(137)cs and^(210)pbex in an intensive agricultural catchment in North China.Sediment sources from surface and sub-surface soils were estimated from FRNs fingerprint and accounted for 62±7%and 38±7%respectively,while surface soil from land uses that originated from hillslope were identified by CssI fingerprint.Using a novel application of FRNs and CSSI sediment fingerprinting techniques,the dominant sediment source was derived from maize farmland(44±0.1%),followed by channel bank(38±7%).The sedimentation rate(13.55±0.30 t ha^(-1)yr^(-1))was quantifed by the^(137)cs cores(0-60 cm)at the outlet of this catchment.The total N and total P in sediment were both mostly derived from maize farmland and least from channel banks.The channel banks are significant sediment sources but contribute little to the input of sediment N and P for eutrophication.It implies that chemically-applied farmlands are the main hotspots for catchment erosion control and pollution prevention.The novel application of FRNs and CSSI techniques cost-effectively quantified sediment N and P loads from different sources with a single visit to the catchment,enabling rapid assessment for optimizing soil conservation strategies and land management practices.

Slope-gully erosion relationship in small catchments of the middle reaches of the Yellow River

The slope-gully erosion relationship in small catchments of the middle reaches of the Yellow River has long been a topic concerned by relevant departments in China Slope-gully relationship in typical small catchment is determined determined on the concept of net increase of sediment yield by using analytical method of sediment formation at different positions in the catchment The result shows that sediments in a small catchment in the middle reaches of the Yellow River mainly come from slopes. ms paper indicated that the sediment sources from slopes are roughly 55, 60, 78 and 85 % of the total sediment yield of a small catchment in Yangdaogou. Wangjiagou. Jiuyuangou and Nanxiaohegou, respectively, due to impacts of varying degress from slope runoff.

Characteristics of Clay Minerals in the Northern South China Sea and Its Implications for Evolution of East Asian Monsoon since Miocene

Clay mineral assemblages, crystallinity, chemistry, and micromorphology of clay particles in sediments from ODP Site 1146 in the northern South China Sea （SCS） were analyzed, and used to trace sediment sources and obtain proxy records of the past changes in the East Asian monsoon climate since the Miocene, based on a multi-approach, including X-ray diffraction （XRD） and scanning electron microscopy combined with energy dispersive X-ray spectrometry （SEM-EDS）. Clay minerals consist mainly of illite and smectite, with associated chlorite and kaolinite. The illite at ODP Site 1146 has very well-to-well crystallinity, and smectite has moderate-to-poor crystallinity. In SEM the smectite particles at ODP Site 1146 often appear cauliflower-like, a typical micromorphology of volcanic smecites. The smectite at ODP Site 1146 is relatively rich in Si element, but poor in Fe, very similar to the smectite from the West Philippine Sea. In contrast, the chemical composition of illite at ODP Site 1146 has no obvious differences from those of the Loess plateau, Yellow River, Yangtze River, and Pearl River. A further study on sediment source indicates that smectite originates mainly from Luzon, kaolinite from the Pearl River, and illite and chlorite from the Pearl River, Taiwan and/or the Yangtze River. The clay mineral assemblages at ODP Site 1146 were not only controlled by continental eathering regimes surrounding the SCS, but also by the changing strength of the transport processes. The ratios of （illite＋chlorite）/smectite at ODP Site 1146 were adopted as proxies for the East Asian monsoon evolution. Relatively higher ratios reflect strongly intensified winter monsoon relative to summer monsoon, in contrast, lower ratios indicate a strengthened summer monsoon relative to winter monsoon. The consistent variation of this clay proxy from those of Loess plateau, eolian deposition in the North Pacific, planktonic, benthic foraminifera, and black carbon in the SCS since 20 Ma shows that three profound shifts of the East Asian winter monsoon intensity, and aridity in the Asian inland and the intensity of winter monsoon relative to summer monsoon, occurred at about 15 Ma, 8 Ma, and the younger at about 3 Ma. The phased uplift of the Himalaya-Tibetan plateau may have played a significant role in strengthening the Asian monsoon at 15 Ma, 8 Ma, and 3 Ma.

Reconciliation of the Early Slip History of the Altyn Tagh Fault, Northern Tibetan

Whether the Altyn Tagh fault (ATF) had been extended beyond its current northeastern tip and linked with strike-slip faults in East Asia is a key to understanding the timing and mechanisms of crustal deformation in the northern Tibetan Plateau. We present Late Cretaceous dextral movement affected by Okhotomorsk Block-East Asia collision and a larger sinistral offset since Late Eocene along the ATF based on the provenance analysis of western Jiuxi Basin. Moreover, currently available estimates of offset based on displaced Paleozoic and Jurassic rocks could not represent the maximum offset due to late Cretaceous dextral offset.

Performance evaluation of a water erosion tracer using plot-scale experiments and process-based modeling

Socioeconomic and environmental losses caused by water erosion have highlighted the importance of quantifying and understanding the dynamics of soil redistribution in the landscape to develop effective soil management practices.Several methods are applied to estimate erosion/deposition rates and identify sources of sediments,among them,the one that uses rare earth elements(REE)as a tracer stands out.However,an alternative not yet explored that can benefit the accuracy of the estimates provided by the method is using a tracer containing a chemical signature composed of more than one REE.The present study aimed to evaluate the performance of a new water erosion tracer based on montmoril-lonite labeled with rare earth elements(La40-MMT).The innovative aspects of this La40-MMT tracer include its highly stable multi-chemical signature(Nd^(3+),La^(3+),and Pr^(3+)),which enhances tracer detection in the environment,and its low production cost due to the use of an industrial residue in the synthesis process.The tracer was evaluated for a typical soil of the Cerrado biome,using a natural rainfall field-scale plot-NRFP(5 m × 20 m)and a physical predictive erosion model(WEPP).The results showed that the La40-MMT tracer could be used to estimate erosion/deposition rates,with agreement between the values observed with the tracer and the WEPP model.Thus,this study confirmed the great potential of La40-MMT as a tool to identify patterns of soil redistribution at the field scale and aid in the validation of erosion models.

Geochemistry of rare earth elements and yttrium in Late Permian coals from the Zhongliangshan coalfield, southwestern China

Rare earth elements and yttrium(REY)in coal deposits are considered promising alternative sources for these resources owing to their increasing global demand.This paper reports the geochemical characteristics of REY in the Late Permian coals from an underground K1a seam section of the Zhongliangshan coalfield in Chongqing,southwestern China.The mineralogy,degree of enrichment,distribution patterns,modes of occurrence,and sediment origin of REY were investigated.Compared with the average of world coals,the concentration of REY in the K1a coals were normal,dominated by light REY(LREY),with less medium and heavy REY(MREY,HREY).The fractionation degree of the MREY and HREY are higher than that of LREY in most K1a coal samples,deduced from the mixed enrichment type of REY,mainly including M-H-type,and a few L-M type and H-type.In addition,the combination of anomalies of Ce,Eu,Gd,and Al_(2)O_(3)/TiO_(2) parameters,the terrigenous materials in the K1a coal were derived from the felsic-intermediate rocks at the top of the Emeishan basalt sequence,and the samples were affected by seawater intrusion during early peat accumulation.Although the minerals primarily consist of kaolinite,illite,pyrite,and small amounts of quartz,calcite and anatase,REY are correlated with ash yield,SiO2,and Al_(2)O_(3),revealing that the REY mainly occur in aluminosilicate minerals,especially kaolinite and illite.Meanwhile,REY positively relate to P_(2)O_(5) and Zr,which may exist in phosphate-containing minerals or zircon.Furthermore,most samples in the K1a coal or ash do not reach the cut-off grade for the beneficial recovery of REY.With the exception of central Guizhou,southwestern Chongqing,and the junction of western Guizhou and northeastern Yunnan,the REY content in coals from southwestern China are high,and its by-products are suitable as potential REY sources.

Distribution characteristics and source identification of polychlorinated dibenzo-p-dioxin and dibenzofurans,and dioxin-like polychlorinated biphenyls in the waters from River Kanzaki,running through Osaka urban area,Japan

This is the first to elucidate the distribution and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans （PCDD/PCDFs）,and dioxin-like polychlorinated biphenyls in the waters from Kanzaki River,which is one of the most heavily polluted rivers in Japan.The World Health Organization （WHO）-toxic equivalent quantities （TEQs） in waters from the mainstream exceeded the Japanese environmental standard （1.0 pg-TEQ/L）.The PCDD/PCDFs were dominated by highly chlorinated DFs,which predominantly contributed to the WHO-TEQs,suggesting that the main causes would be the incineration-related wastes.To find the sources,the dioxin congener concentrations in water and sediment samples from its tributary small waterways were determined.Abnormally high WHO-TEQs were detected in a water （50 pg-TEQ/L） and a sediment sample （41,000 ng-TEQ/kg dry weight） near the industrial solid waste incinerators （ISWIs）.The PCDD/PCDF characteristics agreed well with those of the incinerator-related wastes as seen in the mainstream.These facts indicate that the dioxin pollution in the mainstream could be largely related to the industrial wastes from the ISWIs.Here,a TEQ apportionment method was used to understand the contribution of the pyrogenic sources to the WHO-TEQs.The average contribution ratios of the pyrogenic sources to WHO-TEQs were more than 80% for river waters from the mainstream,indicating that the elevated WHO-TEQs in the mainstream had been largely caused by the ISWIs.

Quartz-Hosted Fluid Inclusions Characteristics and Their Implications for Fluvial Deposits along the Changjiang River

The characteristics of quartz-hosted fluid inclusions in fluvial sediments from five locations in the upstream,midstream,and estuary of the Changjiang River,China,are analyzed.The sources of sediments are discussed concerning their differences in the shape,size,number,gas percentage and genetic type of quartz-hosted fluid inclusions.From upstream to downstream,the characteristics of quartz-hosted fluid inclusions in sediments are different.The fluid inclusion types in the samples from upstream to estuary are gradually enriched.The sediment influx from the tributaries of the Changjiang River makes new types of quartz-hosted fluid inclusions in the downstream and estuary.In terms of the number and size,most quartz-hosted fluid inclusions are concentrated in the range of 2-4μm in diameters and 10-150 in number per 10^-3 mm^3.The number and size ranges of the fluid inclusions from different positions are also different.The fluid inclusions in the sample collected from the Shigu,upstream of the Changjiang River,are 2-18μm in size,with the number of 2-166 per 10^-3 mm^3.Among the samples collected from Yibin,Yichang and Wuhan,the sizes of fluid inclusions are 2-15,2-10,2-12μm,with the number of 1-270,2-220,and 1^-308 per 10^-3 mm^3,respectively.The proportion of primary fluid inclusions in the sample of the upstream(14%)is higher than that of the midstream(6%-8%)and the estuary(5%),suggesting that different types of source rocks have been input into the river by the tributaries.The characteristics of quartz-hosted fluid inclusions in the fluvial sediments could offer a new perspective for exploration of the source of sediments.