The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen conce...The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.展开更多
South of Hangzhou Bay, Zhejiang Province, exhibits an embayed muddy coastline, with the muddy beaches of embayments extending continuously seaward.The source of sediments on this coast presents an interesting problem ...South of Hangzhou Bay, Zhejiang Province, exhibits an embayed muddy coastline, with the muddy beaches of embayments extending continuously seaward.The source of sediments on this coast presents an interesting problem to marine geologists and geomorphologists .The total annual load of sediments from the rivers of Zhejiang is only 12×106t.These materials affect only the area near the river mouths. The paper showed that the sediment along the coast of Zhejiang mainly comes from the Changjiang Estuary through analysing the time and space variations of suspended sediment, the features of sediment and the sedimentary transport.The Changjiang River is the largest river system in China, its sediment to the sea amounting to 468×106t. The sediment during summer transports mainly eastward, and is affected by the water body with high temperature, salinity and transparency; the winter season is the period with high sediment concentration. The sediment of the Changjiang Estuary transports together with the longshore current of the East China Sea southward, the southern boundary can reach the sea region approximately 500 km from the Shacheng Harbour. The accretion rate seaward has been about 10 - 30 m since the 16th century. The sediment movement combined the longitudinal with the lateral, so that the muddy flats progress continuously seaward under the construction of the seashore profile .展开更多
The offshore waters of the Changjiang Estuary are the transitional areas where river-supplied water and sediment are transported to the sea, and material exchanges occur with the neighbored Hangzhou Bay and the Jiangs...The offshore waters of the Changjiang Estuary are the transitional areas where river-supplied water and sediment are transported to the sea, and material exchanges occur with the neighbored Hangzhou Bay and the Jiangsu waters. Field observations of currents and sediment properties were conducted to study temporal and spatial distributions of suspended sediments under various dynamical conditions. The high sediment concentrations were found to occur in the western and southern waters of the offshore, and the low concentrations occurred in the eastern and northern waters. This pattern of the suspended sediment concentration （SSC） distribution is obviously influ- enced by the runoff and tidal current. The significant difference of along-estuary SSC distribution indicates that the SSC is reduced gradually from the west to the east, and that in the spring tide is obviously higher than in the neap tide. The methods of mechanism analysis and equal-area grids were used to calculate the suspended sediment fluxes at the typical cross sections. It was found that 44 percent of total suspended sediments from the Changjiang River were deposited in the submarine delta, and more than 27 percent of sediments were transported southernly into the Hangzhou Bay, and only 9 percent of sediments was supplied and exchanged with the northern Jiangsu waters, and about 20 percent of sediments was delivered offshore to the sea.展开更多
Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the n...Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with the submarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huanghe River changed its course and flowed northward into the Bohai Sea.展开更多
In order to study the relationship between nutrient pollutants and suspended sediments（SS） in the upper reaches of the Yangtze River and two tributaries, water samples were collected from September 1, 2010 to Septem...In order to study the relationship between nutrient pollutants and suspended sediments（SS） in the upper reaches of the Yangtze River and two tributaries, water samples were collected from September 1, 2010 to September 30, 2011 at the Zhutuo, Cuntang, Beibei, Wulong, Qingxichang,Wanxian, and Fengjie cross-sections. In the laboratory, the SS concentration and the concentration of SS whose particle size was smaller than0.02 mm were measured. The phosphorus（P）, nitrogen（N）, and permanganate index（CODMn） concentrations in the natural water sample, the settled water sample, and two types of filtered water samples obtained through filter membranes with pore sizes of 0.02 mm and 0.45 mm were monitored synchronously. The results show that there are strong relationships between the P and CODMnconcentrations and the SS concentration. P mainly exists in particulate form, while N mainly exists in dissolved form. SS whose particle size is smaller than 0.02 mm accounts for a high proportion of sediments in the Yangtze River and has a strong effect on water quality. At the seven cross-sections, the amounts of P, N, and CODMnin particulate form in the wet season are higher than in the dry season and the adsorption amounts of P, N, and CODMnper unit mass of sediment are higher in the dry season than in the wet season.展开更多
Accurate daily suspended sediment load(SSL)prediction is essential for sustainable water resource management,sediment control,and environmental planning.However,SSL prediction is highly complex due to its nonlinear an...Accurate daily suspended sediment load(SSL)prediction is essential for sustainable water resource management,sediment control,and environmental planning.However,SSL prediction is highly complex due to its nonlinear and dynamic nature,making traditional empirical models inadequate.This study proposes a novel hybrid approach,integrating the Adaptive Neuro-Fuzzy Inference System(ANFIS)with the Gradient-Based Optimizer(GBO),to enhance SSL forecasting accuracy.The research compares the performance of ANFIS-GBO with three alternative models:standard ANFIS,ANFIS with Particle Swarm Optimization(ANFIS-PSO),and ANFIS with Grey Wolf Optimization(ANFIS-GWO).Historical SSL and streamflow data from the Bailong River Basin,China,are used to train and validate the models.The input selection process is optimized using the Multivariate Adaptive Regression Splines(MARS)method.Model performance is evaluated using statistical metrics such as Root Mean Square Error(RMSE),Mean Absolute Error(MAE),Mean Absolute Percentage Error(MAPE),Nash Sutcliffe Efficiency(NSE),and Determination Coefficient(R^(2)).Additionally,visual assessments,including scatter plots,Taylor diagrams,and violin plots,provide further insights into model reliability.The results indicate that including historical SSL data improves predictive accuracy,with ANFIS-GBO outperforming the other models.ANFIS-GBO achieves the lowest RMSE and MAE and the highest NSE and R^(2),demonstrating its superior learning ability and adaptability.The findings highlight the effectiveness of nature-inspired optimization algorithms in enhancing sediment load forecasting and contribute to the advancement of AI-based hydrological modeling.Future research should explore the integration of additional environmental and climatic variables to enhance predictive capabilities further.展开更多
According to some main assumptions in the Rouse Formula,it analyzes the applicability of Rouse distribution in the coastal region.Based on the classical Rouse Formula,the linear form of Rouse Formula and the transport...According to some main assumptions in the Rouse Formula,it analyzes the applicability of Rouse distribution in the coastal region.Based on the classical Rouse Formula,the linear form of Rouse Formula and the transport characteristics of offshore sediment were used to take lnz/h,lnc_(a),c_(a),u,lnu and z/h as the independent variables.The multiple liner regression method was used to analyze the influence of the independent variables on the vertical distribution of sediment concentration.By using the method of significance test,the factors(lnu)that have less influence on sediment concentration among 6 variables were eliminated.The correlation coefficient between the calculated sediment concentration and the measured sediment concentration indicates that the adopted variables can reflect the characteristics of vertical distribution of concentration of fine sediment near shore under complex dynamic conditions.展开更多
This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current ...This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current systems by analyzing the thermal infrared imagery with the sediment imagery, which is acquired by correlating the atmosphere corrected AVHRR imagery with in-situ suspended sediment data. The coastal current systems affecting the sediment dispersal mainly include： the Taiwan Warm Current （TWC）, the Huanghai Sea Mixed Water （HSMW）, North Jiangsu near-shore current, and Zhejiang near-shore current etc. In winter, the current systems are stable. Their distribution affects the sediment from north Jiangsu expanding toward the Changjiang estuary in some degree .The front between Zhejiang coastal current and TWC blocks the expanding of sediment toward the sea. In the flood season, apart from the limitation by coastal current systems, the spatial and temporal distribution of suspended sediment is also affected by the runoff, which shows as the jet stream and fresh water. Spring and autumn are the transitional periods of the forming of expanding patterns of flood season and winter respectively. In addition, the re-suspended sediment caused by the wind wave may make the expanding range of near-shore sediment larger.展开更多
The transport mechanism and settlement characteristics of suspended sediments are analyzed in this article on the basis of measured data. Results indicate that the concentration and flux of suspended sediments decreas...The transport mechanism and settlement characteristics of suspended sediments are analyzed in this article on the basis of measured data. Results indicate that the concentration and flux of suspended sediments decrease sharply from Hangzhou Bay to the offshore area. Suspended sediment transport is mainly controlled by advection transport and gravitational circulation transport. The settling velocity of suspended sediments gradually decreases from Hangzhou Bay to the offshore area. The settlement of suspended sediments mainly takes place during the turning phase of the tidal currents.展开更多
The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the Nor...The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the North Channel of Changjiang Estuary. They were assimilated with the measured data in 2003, 2004, 2006 and 2007, using the tidal range＇s proportion conversion. Variations in TCD and TCV, preferential flow and SSC have been calculated. Influences of typical engineering projects such as Qingcaosha fresh water reservoir, Yangtze River Bridge, and land reclamation on the ebb and flood TCD, TCV and SSC in the North Channel for the last 10 years are discussed. The results show that： （1） currently, in the upper part of North Channel, the ebb tide dominates; after the construction of the typical projects, ebb TCD and TCV tends to be larger and the vertical average ebb and flood SSC decrease during the flood season while SSC increases during the dry season; （2） changes in the vertical average TCV are mainly contributed by seasonal runoff variation during the flood season, which is larger in the flood season than that in the dry season; the controlling parameters of increasing ebb TCD and TCV are those large-scale engineering projects in the North Channel; variation in SSC may result mainly from the reduction of basin annual sediment loads, large-scale nearshore projects and so on.展开更多
Rahughat Hydroelectric Project is an ROR （run of river） project with the installed capacity of 40 MW. The suspended sediment study was carried out in 2008 and 2015 AD. The present study is concentrated on the study ...Rahughat Hydroelectric Project is an ROR （run of river） project with the installed capacity of 40 MW. The suspended sediment study was carried out in 2008 and 2015 AD. The present study is concentrated on the study carried out in 2015 AD. The suspended sediment samples were collected in the headworks site and its analysis was done in Hydro Lab Pvt. Ltd. Concentration analysis, PSD （particle size distribution） analysis and mineral content analysis were carried out. The minimum and maximum sediment concentration is 54 PPM and 3,759 PPM respectively. The PSD analysis shows that 52% of the suspended sediment contained sand fraction and 48% is fine sediments. The mineral content analysis shows presence of quartz, feldspar, mica, kyanite, garnet, carbonates, chlorite, clay and some fragments of shale, phyllite and slate with few unidentified sediments. The proposed desander in RGHEP is designed to settle particles of size 0.2 mm and above. The sediments lesser than 0.2 mm size that reach the turbine may affect the loss of turbine material due to erosion.展开更多
Based on the analysis of suspended sediment elements at estuaries, influence of human activities and estuarine regulation projects on the turbidity maximum zone was studied according to the measurement data between 19...Based on the analysis of suspended sediment elements at estuaries, influence of human activities and estuarine regulation projects on the turbidity maximum zone was studied according to the measurement data between 1959 and 2011. It was found that human activi- ties had little effect on the seaward water while the sharp decrease of sediment volume and concentration in runoff led to the sharp decrease of turbidity maximum zone in the estuary. The concentration at outside sea and Hangzhou Bay did not change, and that along the Subei coast also decreased a little, which had no influence on the turbidity maximum zone. Com- pared with the concentration between 1959 and 1999, the peak of concentration moved up- stream in the estuary, and the concentration in 2000-2009 decreased by about 24.73% with a narrower variation range along the river to the sea. The suspended sediment concentration in North Passage was low in upstream and downstream because of the decrease of seaward sediment and coarsening of bed material, while it was relatively high in the middle due to the influence of sediment cross the north jetty.展开更多
The monthly mean suspended sediment concentration in the upper layer of the East China Seas was derived from the retrieval of the monthly binned SeaWiFS Level 3 data during 1998 to 2006. The seasonal variation and spa...The monthly mean suspended sediment concentration in the upper layer of the East China Seas was derived from the retrieval of the monthly binned SeaWiFS Level 3 data during 1998 to 2006. The seasonal variation and spatial distribution of the suspended sediment concentration in the study area were investigated. It was found that the suspended sediment distribution presents apparent spatial characteristics and seasonal variations, which are mainly affected by the resuspension and transportation of the suspended sediment in the study area. The concentration of suspended sediment is high inshore and low offshore, and river mouths are generally high concentration areas. The suspended sediment covers a much wider area in winter than in summer, and for the same site the concentration is generally higher in winter. In the Yellow and East China Seas the suspended sediment spreads farther to the open sea in winter than in summer, and May and October are the transitional periods of the extension. Winds, waves, currents, thermocline, halocline, pycnocline as well as bottom sediment feature and distribution in the study area are important influencing factors for the distribution pattern. If the 10rag L^-1 contour line is taken as an indicator, it appears that the transportation of suspended sediment can hardly reach 124^o00＇E in summer or 126^o00＇E in winter, which is due to the obstruction of the Taiwan Warm Current and the Kuroshio Current in the southern Yellow Sea and the East China Sea.展开更多
Profles of tidal current and suspended sediment concentration （SSC） were measured in the North Branch of the Changjiang Estuary from neap tide to spring tide in April 2010. The measurement data were analyzed to dete...Profles of tidal current and suspended sediment concentration （SSC） were measured in the North Branch of the Changjiang Estuary from neap tide to spring tide in April 2010. The measurement data were analyzed to determine the characteristics of intratidal and neap-spring variations of SSC and suspended sediment transport. Modulated by tidal range and current speed, the tidal mean SSC increased from 0.5 kg/m3 in neap tide to 3.5 kg/ma in spring tide. The intratidal variation of the depth-mean SSC can be summarized into three types： V-shape variation in neap tide, M-shape and mixed M-V shape variation in medium and spring tides. The occurrence of these variation types is controlled by the relative intensity and interaction of resuspension, settling and impact of water exchange from the rise and fall of tide. In neap tide the V-shape variation is mainly due to the dominant effect of the water exchange from the rise and fall of tide. During medium and spring tides, resuspension and settling processes become dominant. The interactions of these processes, together with the sustained high ebb current and shorter duration of low-tide slack, are respon- sible for the M-shape and M-V shape SSC variation. Weakly consolidated mud and high current speed cause significant resuspension and remarkable flood and ebb SSC peaks. Setting occurs at the slack water periods to cause SSC troughs and formation of a thin flufflayer on the bed. Fluxes of water and suspended sediment averaged over the neap-spring cycle are all seawards, but the magnitude and direction of tidal net sediment flux is highly variable.展开更多
Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in...Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in the current velocity was observed in the South Branch as a result of high river runoff and tide deformation, in which the magnitude and duration of ebb currents were significantly greater than those of flood currents. The suspended sediment concentration（SSC） and suspended median grain size also exhibited remarkable flood-ebb variation; these variables were considerably larger during the ebb than during the flood and increased from neap to spring tide. Affected by the strong asymmetry in the current velocity and SSC between the flood and ebb,suspended sediment flux during the ebb was notably larger than during the flood, and a seaward tidal net flux was observed in each tidal cycle. The balance of sediment flux illustrates that the seaward sediment transport was dominated by river flow and tidal trapping and the landward sediment transport was dominated by the Stokes drift and the shear effect. Notable resuspension occurred during the spring and moderate tides. The critical velocity for the resuspension of bed sediments was estimated based on the correlation between current velocity with SSC and suspended median grain size. The results show that the critical velocity was approximately 40 cm/s during the flood phases and approximately 80 cm/s during the ebb phases because the surficial flood bed sediments located in the lower reach are much finer than the surficial ebb bed sediments located in the upper reach. The flood-ebb variation in the critical erosion velocity has significant effect on the intratidal variation of SSC and sediment transport process, and it is a common phenomenon in many estuaries of the world due to the complicated spatial distribution of bed sediments.展开更多
The sediment discharge from the Yangtze River Basin has a stepwise decreasing trend in recent years. The impounding of the Three Gorges Reservoir exacerbated this de- creasing trend and affected the change of the susp...The sediment discharge from the Yangtze River Basin has a stepwise decreasing trend in recent years. The impounding of the Three Gorges Reservoir exacerbated this de- creasing trend and affected the change of the suspended sediment concentration （SSC） in the Yangtze River Estuary through the transmission effect. The SSC data of the Yangtze River Estuary during 1959-2012 showed that： （1） The SSC in the South Branch of the Yang- tze River in the estuary and in the off-shore sea area displayed decreasing trends and de- creased less towards the sea. At the same time, the difference in decreasing magnitude be- tween SSC and sediment discharge became bigger towards the sea. （2） For the North Branch the preferential flow did not change much but the SSC tended to decrease, which was mainly caused by the decrease of SSC in the South Branch and China East Sea. （3） Due to the de- creased runoff and the relatively strengthened tide, the peak area of the SSC in the bar shoal section in 2003-2012 moved inward for about 1/6 longitude unit compared with that in 1984-2002, and the inward-moving distance was in the order of flood season 〉 annual average 〉 dry season. （4） In the inlet of the South Passage, the SSC decreased mainly because the increase caused by resuspension and shore-groove exchange was less than the decrease caused by the sharp SSC decrease in the basin and the sea areas. The reverse was true in the middle section, where the SSC showed an increasing trend. （5） In the inlet of the North Passage, under the combined influence of decreased flow split and sediment split ratios, the decreased SSC in the basin and the sea area and decreased amount of resuspension, the SSC displayed a decreasing trend. In the middle section, because the increased amount caused by sediment going over the dyke was markedly more than the decreased amount caused by external environments, the SSC tended to increase. Holistically, the sharp decrease in sediment discharge caused synchronized SSC decreases in the Yangtze River Estuary. But there were still areas, where the SSC displayed increasing trends, indicatingsynchronicity and difference in the response of SSC to the sharp decrease in sediment discharge from the basin.展开更多
We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time o...We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.展开更多
A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion ...A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls spatial distribution of SSC.展开更多
Information on the concentration of suspended sediments in coastal waters is necessary for the understanding and management of the coastal environment. Traditionally, suspended sediment concentration （SSC） has been ...Information on the concentration of suspended sediments in coastal waters is necessary for the understanding and management of the coastal environment. Traditionally, suspended sediment concentration （SSC） has been measured by time-consuming and costly boat surveys which allow the accurate measurement of SSC for single points in space and time. In order to obtain the instantaneous measurement of SSC, a variety of remote sensing method has been adopted. Remote sensing from airborne and spaceborne sensors has been proven to be a useful adjunct to such surveys as it provides an instantaneous and synoptic view of sediments that would otherwise be unavailable. Dominique Durand and Jerome Bijaoui in 2000 presented a feasible study on optical remote sensing of shallow-water environmental parameters. Yogesh C. Agrawal and H. C. Pottsmith in 2001 tried to use Laser Diffraction Sensors to measure Concentration and Size Distribution of Suspended Sediment. Francisco Pedocchi and Marcelo H. Garcia in 2006 made an evaluation of the LISST-ST instrument for suspended particle size distribution and settling velocity measurements. H.K.Ha and W-Y.Hsu in 2009 tried to measure suspended cohesive sediment concentration using ADV backscatter strength. Shuisen Chen, Ligang Fang in 2009 managed to use remote sensing of turbidity in seawater intrusion reaches of Pearl River Estuary. In this article, the brief review of most of the technologies or methods used to observe the suspended sediment concentration is executed. As the most powerful technology in the remote sensing, acoustic backscatter device is discussed in detail. A comparison between those traditional and modern technologies is made to clarify its future application and development.展开更多
Accurate assessment of surface suspended sediment concentration （SSSC） in estuary is essential to address several important issues： erosion, water pollution, human health risks, etc. In this study, an empirical cub...Accurate assessment of surface suspended sediment concentration （SSSC） in estuary is essential to address several important issues： erosion, water pollution, human health risks, etc. In this study, an empirical cubic retrieval model was developed for the retrieval of SSSC from Yellow River Estuary. Based on sediments and seawater collected from the Yellow River and southeastern Laizhou Bay, SSSC conditions were reproduced in the laboratory at increasing concentrations within a range common to field observations. Continu- ous spectrum measurements of the various SSSCs ranging from 1 to 5700 mg/1 were carried out using an AvaField-3 spectrometer. The results indicated the good correlation between water SSSC and spectral reflectance （Rrs） was obtained in the spectral range of 726-900 nm. At SSSC greater than 2700 mg/L, the 740-900 nm spectral range was less susceptible to the effects of spectral reflectance saturation and more suitable for retrieval of high sediment concentrations. The best correlations were obtained for the reflectance ratio of 820 nm to 490 nm. Informed by the correlation between Rrs and SSSC, a retrieval model was developed （R2 = 0.992）. The novel cubic model, which used the ratio of a near-infrared （NIR） band （740-900 nm） to a visible band （400-600 nm） as factors, provided robust quantifica- tion of high SSSC water samples. Two high SSSC centers, with an order of 103 mg/1, were found in the inversion results around the abandoned Diaokou River mouth, the present Yellow River mouth to the abandoned Qingshuigou River mouth. There was little sedi- ment exchange between the two high SSSC centers due to the directions of the residual currents and vertical mixing.展开更多
基金Supported by the Tianjin Key R&D Program(No.21YFSNSN00220)。
文摘The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries.
文摘South of Hangzhou Bay, Zhejiang Province, exhibits an embayed muddy coastline, with the muddy beaches of embayments extending continuously seaward.The source of sediments on this coast presents an interesting problem to marine geologists and geomorphologists .The total annual load of sediments from the rivers of Zhejiang is only 12×106t.These materials affect only the area near the river mouths. The paper showed that the sediment along the coast of Zhejiang mainly comes from the Changjiang Estuary through analysing the time and space variations of suspended sediment, the features of sediment and the sedimentary transport.The Changjiang River is the largest river system in China, its sediment to the sea amounting to 468×106t. The sediment during summer transports mainly eastward, and is affected by the water body with high temperature, salinity and transparency; the winter season is the period with high sediment concentration. The sediment of the Changjiang Estuary transports together with the longshore current of the East China Sea southward, the southern boundary can reach the sea region approximately 500 km from the Shacheng Harbour. The accretion rate seaward has been about 10 - 30 m since the 16th century. The sediment movement combined the longitudinal with the lateral, so that the muddy flats progress continuously seaward under the construction of the seashore profile .
基金The Science and Technology Commission of Shanghai Municipality Point Project under contract No 07DJ14003
文摘The offshore waters of the Changjiang Estuary are the transitional areas where river-supplied water and sediment are transported to the sea, and material exchanges occur with the neighbored Hangzhou Bay and the Jiangsu waters. Field observations of currents and sediment properties were conducted to study temporal and spatial distributions of suspended sediments under various dynamical conditions. The high sediment concentrations were found to occur in the western and southern waters of the offshore, and the low concentrations occurred in the eastern and northern waters. This pattern of the suspended sediment concentration （SSC） distribution is obviously influ- enced by the runoff and tidal current. The significant difference of along-estuary SSC distribution indicates that the SSC is reduced gradually from the west to the east, and that in the spring tide is obviously higher than in the neap tide. The methods of mechanism analysis and equal-area grids were used to calculate the suspended sediment fluxes at the typical cross sections. It was found that 44 percent of total suspended sediments from the Changjiang River were deposited in the submarine delta, and more than 27 percent of sediments were transported southernly into the Hangzhou Bay, and only 9 percent of sediments was supplied and exchanged with the northern Jiangsu waters, and about 20 percent of sediments was delivered offshore to the sea.
文摘Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyze the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with the submarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huanghe River changed its course and flowed northward into the Bohai Sea.
基金supported by the Chongqing Education Foundation(Grant No.KJ1400324)the Advanced Research Project of Chongqing Science and Technology Commission(Grant No.cstc2013jcyj A20013)
文摘In order to study the relationship between nutrient pollutants and suspended sediments（SS） in the upper reaches of the Yangtze River and two tributaries, water samples were collected from September 1, 2010 to September 30, 2011 at the Zhutuo, Cuntang, Beibei, Wulong, Qingxichang,Wanxian, and Fengjie cross-sections. In the laboratory, the SS concentration and the concentration of SS whose particle size was smaller than0.02 mm were measured. The phosphorus（P）, nitrogen（N）, and permanganate index（CODMn） concentrations in the natural water sample, the settled water sample, and two types of filtered water samples obtained through filter membranes with pore sizes of 0.02 mm and 0.45 mm were monitored synchronously. The results show that there are strong relationships between the P and CODMnconcentrations and the SS concentration. P mainly exists in particulate form, while N mainly exists in dissolved form. SS whose particle size is smaller than 0.02 mm accounts for a high proportion of sediments in the Yangtze River and has a strong effect on water quality. At the seven cross-sections, the amounts of P, N, and CODMnin particulate form in the wet season are higher than in the dry season and the adsorption amounts of P, N, and CODMnper unit mass of sediment are higher in the dry season than in the wet season.
基金supported by the National Natural Science Foundation of China(52350410465)the General Projects of Guangdong Natural Science Research Projects(2023A1515011520).
文摘Accurate daily suspended sediment load(SSL)prediction is essential for sustainable water resource management,sediment control,and environmental planning.However,SSL prediction is highly complex due to its nonlinear and dynamic nature,making traditional empirical models inadequate.This study proposes a novel hybrid approach,integrating the Adaptive Neuro-Fuzzy Inference System(ANFIS)with the Gradient-Based Optimizer(GBO),to enhance SSL forecasting accuracy.The research compares the performance of ANFIS-GBO with three alternative models:standard ANFIS,ANFIS with Particle Swarm Optimization(ANFIS-PSO),and ANFIS with Grey Wolf Optimization(ANFIS-GWO).Historical SSL and streamflow data from the Bailong River Basin,China,are used to train and validate the models.The input selection process is optimized using the Multivariate Adaptive Regression Splines(MARS)method.Model performance is evaluated using statistical metrics such as Root Mean Square Error(RMSE),Mean Absolute Error(MAE),Mean Absolute Percentage Error(MAPE),Nash Sutcliffe Efficiency(NSE),and Determination Coefficient(R^(2)).Additionally,visual assessments,including scatter plots,Taylor diagrams,and violin plots,provide further insights into model reliability.The results indicate that including historical SSL data improves predictive accuracy,with ANFIS-GBO outperforming the other models.ANFIS-GBO achieves the lowest RMSE and MAE and the highest NSE and R^(2),demonstrating its superior learning ability and adaptability.The findings highlight the effectiveness of nature-inspired optimization algorithms in enhancing sediment load forecasting and contribute to the advancement of AI-based hydrological modeling.Future research should explore the integration of additional environmental and climatic variables to enhance predictive capabilities further.
文摘According to some main assumptions in the Rouse Formula,it analyzes the applicability of Rouse distribution in the coastal region.Based on the classical Rouse Formula,the linear form of Rouse Formula and the transport characteristics of offshore sediment were used to take lnz/h,lnc_(a),c_(a),u,lnu and z/h as the independent variables.The multiple liner regression method was used to analyze the influence of the independent variables on the vertical distribution of sediment concentration.By using the method of significance test,the factors(lnu)that have less influence on sediment concentration among 6 variables were eliminated.The correlation coefficient between the calculated sediment concentration and the measured sediment concentration indicates that the adopted variables can reflect the characteristics of vertical distribution of concentration of fine sediment near shore under complex dynamic conditions.
文摘This paper, with NOAA/AHHRR data for 2 years, discusses the expanding path and extent of suspended sediment from the Changjiang River, and the relationship between the suspended sediment expanding and coastal current systems by analyzing the thermal infrared imagery with the sediment imagery, which is acquired by correlating the atmosphere corrected AVHRR imagery with in-situ suspended sediment data. The coastal current systems affecting the sediment dispersal mainly include： the Taiwan Warm Current （TWC）, the Huanghai Sea Mixed Water （HSMW）, North Jiangsu near-shore current, and Zhejiang near-shore current etc. In winter, the current systems are stable. Their distribution affects the sediment from north Jiangsu expanding toward the Changjiang estuary in some degree .The front between Zhejiang coastal current and TWC blocks the expanding of sediment toward the sea. In the flood season, apart from the limitation by coastal current systems, the spatial and temporal distribution of suspended sediment is also affected by the runoff, which shows as the jet stream and fresh water. Spring and autumn are the transitional periods of the forming of expanding patterns of flood season and winter respectively. In addition, the re-suspended sediment caused by the wind wave may make the expanding range of near-shore sediment larger.
文摘The transport mechanism and settlement characteristics of suspended sediments are analyzed in this article on the basis of measured data. Results indicate that the concentration and flux of suspended sediments decrease sharply from Hangzhou Bay to the offshore area. Suspended sediment transport is mainly controlled by advection transport and gravitational circulation transport. The settling velocity of suspended sediments gradually decreases from Hangzhou Bay to the offshore area. The settlement of suspended sediments mainly takes place during the turning phase of the tidal currents.
文摘The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the North Channel of Changjiang Estuary. They were assimilated with the measured data in 2003, 2004, 2006 and 2007, using the tidal range＇s proportion conversion. Variations in TCD and TCV, preferential flow and SSC have been calculated. Influences of typical engineering projects such as Qingcaosha fresh water reservoir, Yangtze River Bridge, and land reclamation on the ebb and flood TCD, TCV and SSC in the North Channel for the last 10 years are discussed. The results show that： （1） currently, in the upper part of North Channel, the ebb tide dominates; after the construction of the typical projects, ebb TCD and TCV tends to be larger and the vertical average ebb and flood SSC decrease during the flood season while SSC increases during the dry season; （2） changes in the vertical average TCV are mainly contributed by seasonal runoff variation during the flood season, which is larger in the flood season than that in the dry season; the controlling parameters of increasing ebb TCD and TCV are those large-scale engineering projects in the North Channel; variation in SSC may result mainly from the reduction of basin annual sediment loads, large-scale nearshore projects and so on.
文摘Rahughat Hydroelectric Project is an ROR （run of river） project with the installed capacity of 40 MW. The suspended sediment study was carried out in 2008 and 2015 AD. The present study is concentrated on the study carried out in 2015 AD. The suspended sediment samples were collected in the headworks site and its analysis was done in Hydro Lab Pvt. Ltd. Concentration analysis, PSD （particle size distribution） analysis and mineral content analysis were carried out. The minimum and maximum sediment concentration is 54 PPM and 3,759 PPM respectively. The PSD analysis shows that 52% of the suspended sediment contained sand fraction and 48% is fine sediments. The mineral content analysis shows presence of quartz, feldspar, mica, kyanite, garnet, carbonates, chlorite, clay and some fragments of shale, phyllite and slate with few unidentified sediments. The proposed desander in RGHEP is designed to settle particles of size 0.2 mm and above. The sediments lesser than 0.2 mm size that reach the turbine may affect the loss of turbine material due to erosion.
基金Fund from the Ministry of Science and Technology of China,No.2010CB429002
文摘Based on the analysis of suspended sediment elements at estuaries, influence of human activities and estuarine regulation projects on the turbidity maximum zone was studied according to the measurement data between 1959 and 2011. It was found that human activi- ties had little effect on the seaward water while the sharp decrease of sediment volume and concentration in runoff led to the sharp decrease of turbidity maximum zone in the estuary. The concentration at outside sea and Hangzhou Bay did not change, and that along the Subei coast also decreased a little, which had no influence on the turbidity maximum zone. Com- pared with the concentration between 1959 and 1999, the peak of concentration moved up- stream in the estuary, and the concentration in 2000-2009 decreased by about 24.73% with a narrower variation range along the river to the sea. The suspended sediment concentration in North Passage was low in upstream and downstream because of the decrease of seaward sediment and coarsening of bed material, while it was relatively high in the middle due to the influence of sediment cross the north jetty.
基金the National Key Basic Research Science Foundation (973 Project)‘Marine Physical Variations in Eastern Marginal Seas of China and Their Environmental Impacts’ (2005CB422303)the Program for New Century Excellent Talents in University (NCET-05-0592)
文摘The monthly mean suspended sediment concentration in the upper layer of the East China Seas was derived from the retrieval of the monthly binned SeaWiFS Level 3 data during 1998 to 2006. The seasonal variation and spatial distribution of the suspended sediment concentration in the study area were investigated. It was found that the suspended sediment distribution presents apparent spatial characteristics and seasonal variations, which are mainly affected by the resuspension and transportation of the suspended sediment in the study area. The concentration of suspended sediment is high inshore and low offshore, and river mouths are generally high concentration areas. The suspended sediment covers a much wider area in winter than in summer, and for the same site the concentration is generally higher in winter. In the Yellow and East China Seas the suspended sediment spreads farther to the open sea in winter than in summer, and May and October are the transitional periods of the extension. Winds, waves, currents, thermocline, halocline, pycnocline as well as bottom sediment feature and distribution in the study area are important influencing factors for the distribution pattern. If the 10rag L^-1 contour line is taken as an indicator, it appears that the transportation of suspended sediment can hardly reach 124^o00＇E in summer or 126^o00＇E in winter, which is due to the obstruction of the Taiwan Warm Current and the Kuroshio Current in the southern Yellow Sea and the East China Sea.
基金The National Science Foundation of China under contract Nos 50939003 and 41176069the Foundation of State Key Laboratory of Estuarine and Coastal Research,East China Normal University of China under contract No.SKLEC-2012KYYW06
文摘Profles of tidal current and suspended sediment concentration （SSC） were measured in the North Branch of the Changjiang Estuary from neap tide to spring tide in April 2010. The measurement data were analyzed to determine the characteristics of intratidal and neap-spring variations of SSC and suspended sediment transport. Modulated by tidal range and current speed, the tidal mean SSC increased from 0.5 kg/m3 in neap tide to 3.5 kg/ma in spring tide. The intratidal variation of the depth-mean SSC can be summarized into three types： V-shape variation in neap tide, M-shape and mixed M-V shape variation in medium and spring tides. The occurrence of these variation types is controlled by the relative intensity and interaction of resuspension, settling and impact of water exchange from the rise and fall of tide. In neap tide the V-shape variation is mainly due to the dominant effect of the water exchange from the rise and fall of tide. During medium and spring tides, resuspension and settling processes become dominant. The interactions of these processes, together with the sustained high ebb current and shorter duration of low-tide slack, are respon- sible for the M-shape and M-V shape SSC variation. Weakly consolidated mud and high current speed cause significant resuspension and remarkable flood and ebb SSC peaks. Setting occurs at the slack water periods to cause SSC troughs and formation of a thin flufflayer on the bed. Fluxes of water and suspended sediment averaged over the neap-spring cycle are all seawards, but the magnitude and direction of tidal net sediment flux is highly variable.
基金The National Natural Science Foundation of China under contract Nos 41176069 and 48505350the Major State Basic Research Development Program of China under contract No.2013CB956502
文摘Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in the current velocity was observed in the South Branch as a result of high river runoff and tide deformation, in which the magnitude and duration of ebb currents were significantly greater than those of flood currents. The suspended sediment concentration（SSC） and suspended median grain size also exhibited remarkable flood-ebb variation; these variables were considerably larger during the ebb than during the flood and increased from neap to spring tide. Affected by the strong asymmetry in the current velocity and SSC between the flood and ebb,suspended sediment flux during the ebb was notably larger than during the flood, and a seaward tidal net flux was observed in each tidal cycle. The balance of sediment flux illustrates that the seaward sediment transport was dominated by river flow and tidal trapping and the landward sediment transport was dominated by the Stokes drift and the shear effect. Notable resuspension occurred during the spring and moderate tides. The critical velocity for the resuspension of bed sediments was estimated based on the correlation between current velocity with SSC and suspended median grain size. The results show that the critical velocity was approximately 40 cm/s during the flood phases and approximately 80 cm/s during the ebb phases because the surficial flood bed sediments located in the lower reach are much finer than the surficial ebb bed sediments located in the upper reach. The flood-ebb variation in the critical erosion velocity has significant effect on the intratidal variation of SSC and sediment transport process, and it is a common phenomenon in many estuaries of the world due to the complicated spatial distribution of bed sediments.
基金Fund from the Ministry of Science and Technology of China,No.2010CB429002National Natural Science Foundation of China,No.51209112No.41331174
文摘The sediment discharge from the Yangtze River Basin has a stepwise decreasing trend in recent years. The impounding of the Three Gorges Reservoir exacerbated this de- creasing trend and affected the change of the suspended sediment concentration （SSC） in the Yangtze River Estuary through the transmission effect. The SSC data of the Yangtze River Estuary during 1959-2012 showed that： （1） The SSC in the South Branch of the Yang- tze River in the estuary and in the off-shore sea area displayed decreasing trends and de- creased less towards the sea. At the same time, the difference in decreasing magnitude be- tween SSC and sediment discharge became bigger towards the sea. （2） For the North Branch the preferential flow did not change much but the SSC tended to decrease, which was mainly caused by the decrease of SSC in the South Branch and China East Sea. （3） Due to the de- creased runoff and the relatively strengthened tide, the peak area of the SSC in the bar shoal section in 2003-2012 moved inward for about 1/6 longitude unit compared with that in 1984-2002, and the inward-moving distance was in the order of flood season 〉 annual average 〉 dry season. （4） In the inlet of the South Passage, the SSC decreased mainly because the increase caused by resuspension and shore-groove exchange was less than the decrease caused by the sharp SSC decrease in the basin and the sea areas. The reverse was true in the middle section, where the SSC showed an increasing trend. （5） In the inlet of the North Passage, under the combined influence of decreased flow split and sediment split ratios, the decreased SSC in the basin and the sea area and decreased amount of resuspension, the SSC displayed a decreasing trend. In the middle section, because the increased amount caused by sediment going over the dyke was markedly more than the decreased amount caused by external environments, the SSC tended to increase. Holistically, the sharp decrease in sediment discharge caused synchronized SSC decreases in the Yangtze River Estuary. But there were still areas, where the SSC displayed increasing trends, indicatingsynchronicity and difference in the response of SSC to the sharp decrease in sediment discharge from the basin.
基金Supported by the National Basic Research Program of China(973Program)(No.2011CB707106)the National Natural Science Foundation of China(Nos.41071261,41023001,41021061,40906092,40971193,41101415)+3 种基金the Opening Foundation of Institute of Remote Sensing and Earth Sciences,Hangzhou Normal University(No.PDKF2010YG06)the Fundamental Research Funds for the Central Universities,the China Postdoctoral Science Foundation(No.20100480861)LIESMARS Special Research Funding,the Natural Science Foundation of Hubei Province,China(No.2009CDB107)the Natural Science Foundation of Zhejiang Province,China(No.Y5090143)
文摘We explored the potential of the environment and disaster monitoring and forecasting small satellite constellations (HJ-1A/1B satellites) charge-coupled device (CCD) imagery (spatial resolution of 30 m, revisit time of 2 days) in the monitoring of total suspended sediment (TSS) concentrations in dynamic water bodies using Poyang Lake, the largest freshwater lake in China, as an example. Field surveys conducted during October 17-26, 2009 showed a wide range of TSS concentration (3-524 mg/L). Atmospheric correction was implemented using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) module in ENVI with the aid of aerosol information retrieved from concurrent Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) surveys, which worked well at the CCD bands with relatively high reflectance. A practical exponential retrieval algorithm was created between satellite remote sensing reflectance and in-situ measured TSS concentration. The retrieved results for the whole water area matched the in-situ data well at most stations. The retrieval errors may be related to the problem of scale matching and mixed pixel. In three selected subregions of Poyang Lake, the distribution trend of retrieved TSS was consistent with that of the field investigation. It was shown that HJ-1A/1B CCD imagery can be used to estimate TSS concentrations in Poyang Lake over synoptic scales after applying an appropriate atmospheric correction method and retrieval algorithm.
基金National Natural Science Foundation of China.No.40276027No.40231010Shanghai Priority Academic Discipline
文摘A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls spatial distribution of SSC.
基金supported by the National Marine Renewable Energy Program(No.GHME2011ZC03,GHME2010ZC08,GHME 2010ZC11 and GHME2010ZC01)Study of the Key Technology of the Forecast of Global Ocean Circulation and Sea Ice(2011BAC03B02)
文摘Information on the concentration of suspended sediments in coastal waters is necessary for the understanding and management of the coastal environment. Traditionally, suspended sediment concentration （SSC） has been measured by time-consuming and costly boat surveys which allow the accurate measurement of SSC for single points in space and time. In order to obtain the instantaneous measurement of SSC, a variety of remote sensing method has been adopted. Remote sensing from airborne and spaceborne sensors has been proven to be a useful adjunct to such surveys as it provides an instantaneous and synoptic view of sediments that would otherwise be unavailable. Dominique Durand and Jerome Bijaoui in 2000 presented a feasible study on optical remote sensing of shallow-water environmental parameters. Yogesh C. Agrawal and H. C. Pottsmith in 2001 tried to use Laser Diffraction Sensors to measure Concentration and Size Distribution of Suspended Sediment. Francisco Pedocchi and Marcelo H. Garcia in 2006 made an evaluation of the LISST-ST instrument for suspended particle size distribution and settling velocity measurements. H.K.Ha and W-Y.Hsu in 2009 tried to measure suspended cohesive sediment concentration using ADV backscatter strength. Shuisen Chen, Ligang Fang in 2009 managed to use remote sensing of turbidity in seawater intrusion reaches of Pearl River Estuary. In this article, the brief review of most of the technologies or methods used to observe the suspended sediment concentration is executed. As the most powerful technology in the remote sensing, acoustic backscatter device is discussed in detail. A comparison between those traditional and modern technologies is made to clarify its future application and development.
基金Under the auspices of National Key R&D Program of China(No.2017YFC0505902)Project of the Cultivation Plan of Superior Discipline Talent Teams of Universities in Shandong Province,National Natural Science Foundation of China(No.41471005,41271016)
文摘Accurate assessment of surface suspended sediment concentration （SSSC） in estuary is essential to address several important issues： erosion, water pollution, human health risks, etc. In this study, an empirical cubic retrieval model was developed for the retrieval of SSSC from Yellow River Estuary. Based on sediments and seawater collected from the Yellow River and southeastern Laizhou Bay, SSSC conditions were reproduced in the laboratory at increasing concentrations within a range common to field observations. Continu- ous spectrum measurements of the various SSSCs ranging from 1 to 5700 mg/1 were carried out using an AvaField-3 spectrometer. The results indicated the good correlation between water SSSC and spectral reflectance （Rrs） was obtained in the spectral range of 726-900 nm. At SSSC greater than 2700 mg/L, the 740-900 nm spectral range was less susceptible to the effects of spectral reflectance saturation and more suitable for retrieval of high sediment concentrations. The best correlations were obtained for the reflectance ratio of 820 nm to 490 nm. Informed by the correlation between Rrs and SSSC, a retrieval model was developed （R2 = 0.992）. The novel cubic model, which used the ratio of a near-infrared （NIR） band （740-900 nm） to a visible band （400-600 nm） as factors, provided robust quantifica- tion of high SSSC water samples. Two high SSSC centers, with an order of 103 mg/1, were found in the inversion results around the abandoned Diaokou River mouth, the present Yellow River mouth to the abandoned Qingshuigou River mouth. There was little sedi- ment exchange between the two high SSSC centers due to the directions of the residual currents and vertical mixing.
