HY-1C Coastal Zone Imager observations of the suspended sediment content distribution details in the sea area near Hong Kong-Zhuhai-Macao Bridge in China

The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coastal Zone Imager(CZI)and Chinese Ocean Color and Temperature Scanner on it.A new SSC inversion model was established based on the relationship between in-situ SSC and the remote sensing reflectance in red and near-infrared bands of CZI image.HY-1C satellite data obtained from October to December 2019 were applied to retrieve SSC in the Zhujiang River Estuary.The results show that SSC around the HKZMB is ranging from 20 mg/L to 95 mg/L.SSC change obviously on two sides of the bridge.During flooding and ebbing period,SSC increases obviously downstream of the bridge.SSC difference between upstream and downstream is ranging from 5 mg/L to 20 mg/L.Currents flowing across the HKZMB,the change trend of SSC in most places upstream and downstream is almost the same that SSC downstream of the bridge is higher than SSC upstream.The tidal currents interact with bridge piers,inducing vortexes downstream,leading the sediment to re-suspend downstream of the bridge piers.Other factors,including seafloor topography and wind,can also contribute to the distribution of SSC in the Zhujiang River Estuary.

Water,organic matter,nitrogen and phosphorus contents in sediment of a large-scale mariculture area in the Zhelin Bay of eastern Guangdong Province,China

The Zhelin Bay is one of the most important bays for large-scale mariculture in Guangdong Province, China. Owing to the increasing human population and the expanding mariculture in the last two decades, the ecological environment has greatly changed with frequent harmful algal blooms. A monthly survey of water content, organic matter （TOM）, and various forms of nitrogen and phosphorous in sediment from July 2002 to July 2003 in the bay was conducted. The results showed that the water content was correlated significantly with TOM and various forms of nitrogen and phosphorus and can be used as proxy for quick and rough estimate of these factors in the future surveys. TOM was also correlated significantly with various forms of nitrogen and phosphorus, indicating that it was one of the key factors affecting the concentrations and distributions of nitrogen and phosphorus in the investigated waters. Average total Kjeldhal nitrogen （TkN） content was（ 1 113.1 ± 382.5）μg/g and average total phosphorus （TP） content was（567.2± 223.3）μg/g, and both were much higher than those of similar estuaries in China and elsewhere. Average nitrogen and phosphorus tended to be higher inside than outside the bay, higher at aquaculture than non-aquaculture areas, and higher at fish-cage culture than oyster culture areas, suggesting that large-scale mariculture inside the bay played an important role in the eutrophication of the Zhelin Bay. Various forms of nitrogen and phosphorus concentrations were higher during the warm season （July--September）, which was due to the increased decomposition and concentration of organic matter resulted from the fast growth and high mortality of the cultured species. Compared with July 2002, TkN and TP contents were much higher in July 2003, in consonance with the eutrophication of the Zhelin Bay. Because exchangeable phosphorus （Ex-P）, iron-bounded phos- phorus （Fe-P） and organic phosphorus （OP） combined accounted for 34.3% of the TP and authigenic phosphorus （Au-P） accounted for 49.2% of the TP, biological phosphorus （BP） that includes Ex-P, Fe-P, OP, and a portion of Au-P, thus accounted for 34.3% to 83.5% of the TP in the Zhelin Bay, which was within the percentage range, but with a high absolute value among the estuaries. Au-P was the most important species of phosphorus and accounted for 49.2% of the TP during the investigation. Since eutrophication in the water column can lead to reduction of pH in sediment and release of phosphorus in Au-P combined with authigenic spodiosite and calcium carbonate, high content of Au-P in the sediment maybe act as a time bomb that can trigger a vicious cycle of eutrophication and large-scale harmful algal bloom in the Zhelin Bay.

Surface Sediment Density and Moisture Content in North slope of South China Sea

Marine engineering geology is mainly based on the actual project to study the seabed.This provides a variety of engineering geological parameters for the development of marine engineering(Zhu et al.,2016).This is an early

Numerical Modeling on Suspended Sediment Transportation in the Hangzhou Bay

In this paper the characteristics of tidal flow and seasonal variation of seidment content in the Hangzhou Bay and their affecting factors are studied. Field investigations and data analysis indicate that the sediment movement is mainly influenced by the Yangtze estuary and the sediment of the Yangtze estuary is induced by wind wave and tidal flow. Owing to the variation of dynamic conditions, the instantaneous sediment content is controlled by tidal flow, wind wave, depth of water and tidal range synthetically. A sediment content relationship formula is established with related factors. A non-equilibrium 2-dimensional numerical model of suspended sediment transportation is set up, and the finite element method is applied. The computation results of the model is in accordance with field data.

Cross-shore suspended sediment flux in the salt marsh pioneer zone of Chongming eastern beach in the Chang- jiang Estuary in China

Between April 2002 and April 2003,in situ measurements of water depth,current velocity and suspended sediment content were carried out in edge region of East Chongming salt marsh and neighboring bald flat in the Changjiang （Yangtze） Estuary under different weather conditions.Cross-shore suspended sediment flux was calculated and analyzed.The results show that under calm weather conditions,the current velocity process in bald field and salt marsh area varied differently during semidiurnal tidal cycles.Owing to current velocity asymmetry,mean SSC during flood tide phase was 1.8 times higher than that of ebb tide phase.As a result,net onshore sediment flux controlled cross-shore suspended sediment transport process and salt marsh pioneer zone was generally accreting.There was significant positive correlation between total sediment flux and quartic power of maximum water depth.It indicates that tidal ranges dominate suspended sediment transport and sedimentation process in the salt marsh pioneer zone under the calm weather condition.The sedimentation rate on the adjacent mudflat was higher than the salt marsh,which induced stable accreting of salt marsh towards the sea.The wind events enhanced SSC and current velocity during the semidiurnal tides.And the remarkable onshore net sediment flux could occur on the high marsh and mudflat close to the marsh fringe during the short period under the rough weather condition.

Characterization of the Songhua River sediments and evaluation of their adsorption behavior for nitrobenzene

The explosion at a plant of the Jilin Petrochemical Corporation on 13 November,2005,and the spill of an estimated 100 t of toxic substances (nitrobenzene as the main component) into the Songhua River received worldwide attention.This study has focused on the adsorption behavior of nitrobenzene that spilled onto sediments along the Songhua River,which was one of the efforts to evaluate the fate of nitrobenzene after the spillage event.The organic carbon contents of these sediments along the Songhua River var...

Critical State Sedimentation Line of Soft Marine Clays

The compression behavior responsible for unity sensitivity is very valuable in quantitative assessment of the effects of soil structure on the compression behavior of soft marine sediments. However, the quantitative assessment of such effects is not possible because of unavailability of the formula for the compression curve of marine sediments responsible for unit sensitivity. In this study, the relationship between the remolded state and the conventional critical state line is presented in the deviator stress versus mean effective stress plot. The analysis indicates that the remolded state is on the conventional critical state line obtained at a relatively small strain. Thus, a unique critical state sedimentation line for marine sediments of unit sensitivity is proposed. The comparison between the critical state sedimentation line proposed in this study and the existing normalized consolidation curves obtained from conventional oedometer tests on remolded soils or reconstituted soils explains well the

不同泥沙含量下受淹胁迫对鄱阳湖平原双季稻生长与产量的影响

为探究鄱阳湖平原区洪涝时期不同泥沙含量下受淹胁迫对双季稻生长及产量的影响,采用大田试验与室内分析相结合的方法,设置淹2/3株高和全淹2种受淹深度,S1(0 kg/m^(3))、S2(0.5 kg/m^(3))、S3(1.0 kg/m^(3))3种泥沙含量,对淹水后6、9 d早稻和中稻的生长指标和水稻产量进行了观测研究。结果表明:适度受淹刺激水稻伸长,节间不断分化,叶片伸长、增宽。早稻抽穗开花期受淹株高、节间长增加9.35%、12.75%,2/3淹下叶面积增加11.00%。但胁迫过大抑制水稻生长,中稻全淹下株高和分蘖数减小33.49%、29.28%,叶面积减小30.94%,此时中稻难以伸出水面,导致功能叶片附沙严重,泥沙含量增大进一步抑制了水稻生长。受淹导致早稻和中稻穗干物质量平均减小32.35%、58.72%(P<0.05)。结实率和千粒质量减小是早稻抽穗开花期受淹后产量下降的主要原因,此时泥沙含量和淹水时间的影响并不明显。中稻全淹下泥沙导致减产加剧,S2、S3下减产率比S1下显著增加31.63%、52.20%(P<0.05),此时产量下降是穗长、有效穗数、穗粒数、结实率、千粒质量综合作用的结果。研究结果可为鄱阳湖平原区洪涝灾害治理和粮食安全保障提供理论和技术支撑。

九龙江口表层沉积物碘含量分析

于2021年5—6月对九龙江红树林保护区与非红树林保护区进行布点采样,测定其表层沉积物碘含量和有机碳含量。结果表明:13个采样点中,碘含量范围为3.7~24.8 mg·kg^(-1),差值最高可达7倍,平均值为12.3 mg·kg^(-1);有机碳含量范围为16~45 g·kg^(-1),平均值为30 g·kg^(-1)。不同类型样品碘含量大小依次为:长林龄林下沉积物>河道清淤沉积物>非林下沉积物>短林龄林下沉积物,其中长林龄林下沉积物碘含量范围为15.7~24.8 mg·kg^(-1),平均值为19.2 mg·kg^(-1);短林龄林下沉积物含量为5.5~6.9 mg·kg^(-1),平均值为6.2 mg·kg^(-1);二者相差3倍以上。有机碳含量最高的为长林龄林下沉积物和河道清淤沉积物,平均值均为32 g·kg^(-1);最低值为短林龄沉积物,含量为22 g·kg^(-1)。不同类型沉积物有机碳含量与碘含量基本呈正相关关系,但相关性不显著;同等有机碳含量的样品,长林龄林下沉积物碘含量显著高于其它样品。

浅水湖泊沉积物生源要素与浮游藻类和沉水植物的关系

为探究长江中下游浅水湖泊沉积物碳、氮、磷等生源要素的含量及其对浮游藻类和沉水植物的影响,以长江中下游11个浅水湖泊为研究对象,分析2003-2020年夏季沉积物总氮(TN_(Sed))、总磷(TP_(Sed))和有机碳(TOC_(Sed))含量与浮游藻类和沉水植物的关系。结果表明:(1)在长江中下游湖泊中,TP_(Sed)在藻型湖泊中最高,为(0.71±0.21)g/kg,草型湖泊中最低,为(0.52±0.13)g/kg。TN_(Sed)和TOC_(Sed)则在草型湖泊中最高,分别为(4.64±3.57)g/kg和(55.89±50.28)g/kg,中间态湖泊最低,分别为TN_(Sed)(1.86±1.26)g/kg,TOC_(Sed)(20.00±12.13)g/kg。(2)回归分析结果显示,夏季浮游藻类Chl-a含量在TP_(Sed)较高的湖泊中更高(P=0.01),沉水植物生物量(BMac)则在TP_(Sed)较低的湖泊中更高(P=0.03),而TN_(Sed)和TOC_(Sed)与Chl-a和BMac的回归关系不显著(P>0.17)。(3)长江中下游湖泊夏季沉水植物消失的沉积物总磷阈值约为0.87~0.98 g/kg。在长江中下游湖泊的沉积物中,磷含量对浮游藻类和沉水植物生物量的预测力比碳、氮含量更高,进一步研究二者定量关系后可为评价水生态系统沉积物污染状况及确定水生植被修复的沉积物条件需求提供科学依据。

长期植被覆盖对紫色土坡面减流减沙能力的影响

[目的]研究长期林草植被覆盖小区减流减沙能力的变化速率,为西南土石山区水土保持植被恢复提供科学依据。[方法]2018—2021年在贵州省赤水市天台镇径流场观测了15°裸地、15°草地、15°林地、30°林地与30°草地5个径流小区的产流产沙、植被覆盖、土壤表层含水量数据,用径流系数和含沙量的变化反映各小区减流减沙能力的变化。[结果]5个小区减流减沙效益排序为30°草地>15°林地>30°林地>15°草地>裸地。其中,30°草地小区植被覆盖度最高,为92.8%,其径流量和土壤侵蚀模数分别为2.43 mm和6.51 t/(km^(2)·a)。裸地小区径流量最高,为153.49 mm,土壤侵蚀模数最高,为1214.5 t/(km^(2)·a);15°草地小区径流系数降低速率最快,为-0.292%/a,其含沙量降低速率也最快,为-14.6 g/(L·a)。植被覆盖度与径流量之间负相关关系极显著,与含沙量负相关关系显著,与土壤表层含水量呈极显著正相关关系。[结论]高植被覆盖度有利于植被恢复、水源涵养和控制水土流失。对于水土流失相对严重的15°草地坡面,其长期植被覆盖的水土保持效益更为明显。

基于VOF-DPM模型的明渠含沙数值模拟及量水方案比选

为探究含沙水流对明渠流量测量精度的影响,基于Fluent软件采用VOF-DPM模型对明渠进行数值模拟,分别模拟不同进口流速和含沙量组合条件下渠道内流量、液位及泥沙颗粒分布,并将数值模拟结果与试验结果进行对比分析,计算出各量水设施的流量误差与液位误差。结果表明:采用VOF-DPM模型可以较好地模拟含沙水流在明渠的流态,通过开展不同流量级的流量测试可知,在不同含沙量条件下,巴歇尔槽流量计误差最小(-3%~1%),超声流量计(-4%~3%)和电磁流量计(-9%~2%)量测效果均较好,雷达流量计误差较大(-20%~4%),说明非接触式流量计在高含沙量、大流量的情况下需进一步提高测量精度;超声液位、电磁液位与雷达液位误差均较大,试验中尾部巴歇尔槽壅水以及泥沙在渠道底部淤积是造成较大液位误差的原因之一。

我国疏浚淤泥处置与利用研究进展

淤泥处理处置与资源化利用是当前困扰工程技术人员和阻碍清淤疏浚工程顺利开展的重大难题。梳理了目前我国疏浚淤泥处置与利用的主要技术方法,简要介绍和评述了每种技术的主要特点、原理和应用情况,同时对相关基本概念内涵进行了梳理,对疏浚淤泥处置利用的未来发展方向进行了展望。

西霞院水库场次洪水排沙规律及影响因素

西霞院水库作为小浪底水库的反调节水库,在调节小浪底水库下泄的不稳定流方面起着重要作用。西霞院水库自运行以来,水库呈持续淤积趋势,研究西霞院水库排沙能力对于减缓水库淤积具有重要意义。基于西霞院水库2011—2022年实测水沙资料,对西霞院水库的历年排沙过程以及排沙影响因素进行深入分析,结果表明:西霞院水库排沙受水库运用方式、来水来沙条件等多种因素影响;流量沿程变化系数、入库含沙量对水库排沙比影响较大,且排沙比与流量沿程变化系数显著正相关,与入库含沙量显著负相关;选取流量沿程变化系数、入库含沙量两个显著相关的参数,通过回归分析建立水库排沙比计算公式,决定系数为0.79,排沙比计算值与实测值拟合效果较好。

基于机器学习算法的清涧河流域径流及含沙量预测研究

为分析黄河中游水沙特征及趋势,预报径流及泥沙的变化,本研究选取黄河中游清涧河流域为研究区域,选用梯度提升回归(GBR)、支持向量回归(SVR)、极端梯度提升(XGBoost)和随机森林回归(RFR)四种机器学习模型,对延川和子长水文站未来3小时的径流和泥沙进行预测。结果表明,根据流域产汇流规律对训练样本方案进行优化有助于提升预测能力。对于流量预报,XGBoost模型表现最好,子长和延川未来第1、2、3小时流量预报的平均NSE分别为0.76和0.90,MAE分别为1.53 m^(3)/s和2.64 m^(3)/s;对于含沙量预报,GBR模型表现最好,子长和延川未来第1、2、3小时含沙量预报的平均NSE分别为0.82和0.90,MAE分别为10.02 kg/m^(3)和6.83 kg/m^(3)。本研究结果可为基于机器学习算法的黄河流域中游水文泥沙预报提供参考。

碎石含量对三峡库区坡耕地土壤氮磷流失特征的影响

坡耕地是三峡库区水土流失的主要来源,导致土壤养分的损失,严重影响库区生态环境建设与社会经济可持续发展。库区坡耕地土壤浅薄化和砾质化特征明显,但目前对含碎石坡耕地土壤侵蚀和养分流失特征的研究尚不多见。该研究通过设置3个降雨梯度(60、90、120 mm/h)和4种碎石含量(0、10%、20%、30%),开展人工模拟降雨试验,分析各试验条件下含碎石土壤产流产沙和氮磷流失特征。结果表明:1)碎石主要通过改变土壤结构以增大产流产沙量来促进氮磷流失,而对相应流失速率与流失浓度的变化规律影响较小,不同碎石含量下泥沙产量的变异系数更高,且泥沙中不同碎石含量下的氮磷流失量显著性差异更强(P<0.05);2)泥沙中累计磷流失量略微大于氮流失量,有效磷几乎不随泥沙流失,有效氮约占全氮流失量的15%;径流中氮素流失量几乎为磷素的10倍且以有效氮为主,占总氮流失量的75%,有效磷占总磷流失量的25%;3)不同碎石含量下有效氮流失规律大致相同,径流中硝态氮约占有效氮流失量的70%,而泥沙中则以铵态氮为主,约占65%;4)不同碎石含量下土壤中氮磷元素均以随侵蚀产沙流失为主,累计产沙量与氮磷元素随侵蚀产沙流失量均在20%碎石含量下达到极大值,10%碎石含量下流失量相对较小,因此泥沙库区坡耕地氮磷流失防治应以减少侵蚀产沙为主,注意大雨暴雨多发季节的水质监测与施肥控制。同时可对土中碎石进行清除使其保持在不高于10%水平。研究结果可为三峡库区含碎石坡耕地水土流失防治和氮磷流失治理提供科学参考。

山区河流流量及悬浮泥砂含量自动监测装置的初步研究

针对山区河流在监测悬浮泥砂含量过程中缺乏实时性的问题,研发了山区河流流量及悬浮泥砂含量自动监测装置。研发中,基于堰槽组合结构设计流量及悬浮泥砂含量监测试验,建立了水位-流量及浑浊度-悬浮泥砂含量模型关系式,利用C语言将2种模型关系式编译写入单片机,设计测量模块、数据存储显示模块及供电模块。实地测试结果表明,该仪器监测的流量相对误差<3%,悬浮泥砂含量相对误差<10%,可以实现连续监测河流流量及悬浮泥砂含量动态变化过程。

输电线路工程不同类型塔基边坡径流产沙特征

[目的]探究输电线路工程塔基边坡水土流失特征,为输电线路工程水土流失治理提供理论依据。[方法]以黄土丘陵区输电线路工程为研究对象,通过野外调查及模拟降雨试验,分析输电线路工程各侵蚀单元水土流失特征及不同类型塔基边坡径流的产沙特征。[结果](1)输电线路工程各侵蚀单元水土流失量占项目总水土流失量的大小依次为塔基区>施工便道>牵张场区>跨越施工场地。塔基区水土流失量占项目总水土流失量的60%以上;(2)与原地面相比,修建塔基边坡增加了地表产流,各类型塔基边坡径流率是原地面的1.8~8.7倍。与偏土质塔基边坡相比,偏石质塔基边坡径流率下降4%~35%,植草的塔基边坡减少20%~48%的径流率;(3)与原地面相比,修建塔基边坡下垫面的径流含沙量增大了0.5~345倍,偏土质塔基边坡增加最大。偏石质比偏土质塔基边坡减少39%~92%径流含沙量,植草可减少83%~98%的含沙量。[结论]输电线路工程建设过程中塔基区是水土流失最大的侵蚀单元,种植草被可以显著减少塔基边坡产沙量,塔基边坡修建后应及时进行植被恢复。

三峡水库干流含沙量对不同形态磷浓度的影响分析

磷是水环境质量评价和污染控制考核的重要指标,其在天然水体中以溶解态、颗粒态等形态存在。研究水中含沙量的改变对不同形态磷浓度的影响,对磷污染控制有着重要意义。选取三峡水库干流为研究对象,采用Mann-Kendall非参数检验法和Pearson相关系数分析了该河段含沙量变化对总磷、溶解磷、颗粒磷等不同形态磷浓度的影响。结果表明:①2003~2019年三峡水库干流的平均流量无明显变化,含沙量则明显减少。②总磷浓度在2003~2012年间起伏波动、缓慢上升,2013~2019年则持续下降;溶解磷浓度呈先上升后下降的趋势,各断面峰值出现在2013、2014年;颗粒态磷浓度呈波动下降趋势。③与2003~2012年浓度均值相比,2013~2019年浑浊水样磷浓度、沉降水样磷浓度以及颗粒磷浓度分别下降了40%,25%和65%;溶解磷浓度则出现明显上升,库尾朱沱断面、变动回水区寸滩断面上升约60%,常年回水区清溪场和万县断面分别上升约20%和12%;溶解磷/沉降水样磷的比值快速上升,2013~2019年溶解磷/沉降水样磷均达到68%以上。④在新水沙条件影响下,三峡水库干流不同形态磷浓度已发生明显改变,最易被浮游生物利用的溶解磷已成为三峡水库干流磷的主要存在形式。研究成果可为三峡库区营养盐控制和治理提供科学依据。

连续降雨条件下工程堆积体产流产沙对砾石含量的响应

[目的]探究连续降雨条件下不同砾石含量对陕北沙壤土上方有来水工程堆积体坡面产流产沙的影响,为生产建设项目水土流失治理提供数据支撑和理论参考。[方法]通过室内模拟降雨试验,研究不同砾石含量(0,10%,20%,30%,40%)工程堆积体坡面土壤水动力学特性及产流产沙特征。[结果]①降雨强度相同,随砾石含量增加,工程堆积体坡面初始产流时间表现为递减趋势,减幅为27.22%~64.62%,35.09%~71.70%,47.37%~78.77%,51.75%~82.31%。次降雨径流率表现为“迅速增加—稳定波动”的变化趋势,平均径流率随砾石含量、降雨时间的增加显著增大;但产流峰值随砾石含量增加而降低,且出现时间逐渐提前。②试验各场次雷诺数的变化范围介于74.13~165.05,均小于500,水流属于层流;弗劳德数的变化范围集中在2.14~3.71,表现为急流。水流剪切力、水流功率和单位水流功率随降雨场次的增加而显著增加。③0%~40%砾石含量工程堆积体坡面侵蚀速率介于0.45~6.73,0.13~4.09,0.25~1.26,0.14~0.96,0.13~0.88 g/(m^(2)·min),各砾石含量堆积体减沙幅度分别为36.06%,49.05%,55.23%和56.62%,其中砾石高覆盖度(40%)的沙壤土工程堆积体坡面土壤侵蚀强度较小。[结论]砾石覆盖在沙壤土工程堆积体坡面的水土流失过程中可显著降低土壤侵蚀速率,从而实现拦蓄水土,保持较高的减沙效益。