Heavy metals and phosphorus in tidal flat sediments of the Yangtze estuary

Concentrations of heavy metals (Cu, Pb, Zn, Cr and Cd), and phosphorous (P) were determined in surface tidal flat sediments of the Yangtze estuary and Shanghai coast. Results demonstrate that there were significant differences among the accumulation of the heavy metals in sediments, following the order: Zn > Cu > Cr > Pb > Cd. The spatial distribution and chemical forms of heavy metals in tidal flat sediments were closely related to the distribution of pollution resources (outlet of sewage) and the local sedimentary and hydrodynamic conditions. The dominated form of non-residual heavy metals is bound to Fe/Mn oxides, and the next form is bound to carbonates. Moreover, contents of total P in sediments range from 18.0 μmol.g?1 to 31.4 μmol.g?1 along the coastline, speciation of P in sediments was different, most of P in tidal flat sediments is associated with calcium phases (as Ca-P) similar to marine sediments.

Distribution and Source of Main Contaminants in Surface Sediments of Tidal Flats in the Northern Shandong Province

Twenty-nine samples of surface sediments from tidal flats in the Northern Shandong Province were collected for grain size, heavy metal(Hg, Cu, Pb, Zn, Cd, and Cr), and oil pollution analyses. The geoaccumulation index(Igeo) and factor analysis were introduced to evaluate sediment quality and source of contaminants. The mean concentrations of Hg, Cu, Pb, Zn, Cd, Cr, and oil in the surface sediments in the study area are 0.033, 17.756, 19.121, 55.700, 0.291, 59.563, and 14.213 μg g-1, respectively. The heavy metal contamination in the old delta lobe is slightly higher than that in the abandoned delta lobe; however, the opposite was observed for oil pollution. The Igeo results revealed that the overall quality of the surface sediments in the study area is in good condition. The heavy metal pollution levels show a descending order: Cd> Hg> Cr> Cu> Zn> Pb, Cd being the main pollutant. The contamination level for in the study area is relatively lower than those for China's other tidal flats. Heavy metals are mainly derived from natural sources of rock weathering and erosion, partly influenced by industrial and agricultural discharge. However, oil pollution is mainly from runoff input, motorized fishing boat sewage, and oil exploitation.

Denitrification in Chongming east tidal flat sediment, Yangtze estuary, China

From July 2003 to July 2004, samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O natural production rate was between -0.08 and 1.74 μmolN·m-2·h-1. N2O natural production rate was higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment denitrification rate was wide, from 1.12 to 33.34 μmolN·m-2·h-1. Temperature, DO and the coactions of them had the prominent effect on the tidal flat sediment denitrification.

Spatial distribution and accumulation of heavy metals in tidal flat sediments of Shanghai coastal zone

Surface and core sediments from the high, middle and low tidal flats of Shanghai coastal zone were analyzed for heavy metal (e.g. Cu, Pb, Zn, Cr, Cd, Fe, Mn) concentrations. Besides Cd, the concentrations of Cu, Zn, Cr and Pb are 2-5 times higher than their background values and show serious pollution trend due to the direct discharge of industrial and municipal sewage along the Shanghai tidal flat, as well as the wet and dry depositions of industrial dusts. It seems that heavy metals prefer to accumulate and be enriched in the sediments near large sewage outlets, high flats, and the subsurface layer at the depth of 10-30 cm. Several main factors, which include the direct sewage discharge along the tidal flat, tidal hydrodynamic action, large engineering activity, early diagenesis and windstorm tide, are considered to be responsible for influencing spatial distribution patterns of heavy metals in the Shanghai tidal flat.

Denitrification in tidal flat sediment, Yangtze estuary

Sediment denitrification rates at six Yangtze River estuary tidal flat locations(mudflats and salt marshes)were measured from July 2003 to October 2004.In winter and summer,spatial distribution of denitrification rates was not great in the Yangtze estuary,while in spring and autumn,denitrification rates had a great spatial distribution because of the human activity effect.The temporal change of denitrification rates was greater.They ranged from 0.2 to 36.4 umolN·m^(-2)·h^(-1),and were higher in the summertime.The annual average of sediment denitrification rate was 18.2±12.3 mu molN · m^(-2)· h^(-1)in the middle tidal flat and 15.1 ±9.45 mu molN·m^(-2)·h^(-1)in the low tidal flat in the Yangtze estuary.Data analysis indicated that the temperature was the primary factor controlling the process of denitrification(significant positive correlation,P<0.01);at the same time,the content of sediment total nitrogen(TN)and the molar ratio of sediment carbon and nitrogen(C/N)had significant positive correlation(P<0.05)and negative correlation(P<0.05)with denitrification rates,respectively.In the Yangtze estuary,increasing of water salinity had no significant inhibition of denitrification because of the wide change range of water salinity.

Magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size

This paper considers the magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size. The results indicate that magnetite of multi-domain (MD)/pseudo-single domain (PSD) in size dominates the magnetic properties of the samples. In addition to detrital magnetite, spherical magnetic particles are found in the magnetically strongest sediments near Shidongkou sewage outlet, which are ascribed to the product of industrial pollution. Particle size plays a strong role on the magnetic properties of the sediments. Magnetic susceptibility (x) and saturation isothermal remanent magnetization (SIRM) are positively correlated with the proportion of the fraction of 8-16 μm. However, magnetic parameters indicating fine-grained ferrimagnetic minerals, e.g. susceptibility of anhysteric remanent magnetization (X ARM), are highly correlated with the fine fraction of <4 μm and even the fraction of <32 μm. The results indicate that, whenX is used as a proxy for pollutant content, it is necessary to consider the possible influence of particle size on it. Due to the significant relationship betweenX ARM and the fine component proportion,X ARM can be applied to the normalization of pollutant content for particle size effect.

Distribution and forms of phosphorus in tidal flat sediments of the Yangtze Estuary and coast

The distribution and forms of phosphorus (P) were investigated in the tidal flat sediments of the Yangtze Estuary and coast. The total P contents in surface sediments range from 18.0 to 31.4 μmol · g-1 along the southern coast. The spatial and temporal distribution of P in tidal flats is closely related to the location and pollution resources, especially in association with the variation of hydrodynamic conditions. Significant variations in the forms of P in different sites were observed. P bonded with Ca(Ca-P) is the dominant mineral form in all surface sediments, organic P(Org-P) is lower. Most P is of unstable form, suggesting that P has larger potential activity. P accumulation is the main behavior process between water and sediment in the coastal environment of the Yangtze Estuary.

Tidal Flat Sedimentation and Event

The concepts of tidal bundle and spring-neap cycles put forward in the studiesof sedimentary structures of sand waves in tidal channels have recently been used intidal flat sedimentation out of tidal channel. In this note, the authors will usemicrosequence and small sequence to replace tidal couplet and spring-neap cycle, soas to see whether spring-neap cycle is applicable to open tidal flats of China.

The variation of sediments organic carbon content in Chongming east tidal flat during Scirpus mariqueter growing stage

The investigations on the organic carbon （OC） of core sediments were carried out in Chongming east tidal fiat （CM） during Scirpus mariqueter growing stage （from April to December 2004） in Yangtze Estuary. The Yangtze River annually transports a runoff discharge of 30,000 m^3/s, carrying about 480 million tons of sediments to the estuarine and coastal area, which formed a great OC pool. In the sampling spots, seven quadrats of 50 cm × 50 cm and five sediments cores of 20 cm deep （40 cm deep in December） were randomly established in order to collect vegetations and core sediments samples during the low tide each month except November. After pretreatment, the core sediments were sieved and their OC contents were measured according to the potassium dichromate method. The results show that the higher surface sediment OC content in summer comes from allochthonous terrigenous particle settlements on the Chongming east middle tidal fiat S. mariqueter zone. In autumn and winter, the decomposing of the defoliated S. mariqueter increases the surface sediments OC content. Settling velocity, sediment temperature and S. mariqueter growth are the main factors that can control the sediment carbon content. Summer is the “carbon losing” period of the tidal fiat sediments, while from September, it changes into the “carbon accumulating” period of sediment OC pool because of the decomposing of dead S. mariqueter community in the sediments. From this alternation of “carbon losing” period and “carbon accumulating” period, we conclude that carbon in the OC pool of the middle tidal fiat S. mariqueter zone sediments mainly comes from the atmospheric carbon rooted by S. mariqueter photosynthesis.

The rule of sediment transport on the Nanhui tidal flat in the Changjiang Estuary

The Nanhui tidal flat is located in the area of slow current where the ebb currents from the Changjiang Estuaryand the Hangzhou Bay converge and the flood current from the sea diverges into the estuary and the bay. The flat extends seaward in tongue shape and has a wide and gentle surface with a marked difference of tidal levels on its two sides, which results in the sediment longitudinal transport on the flat. The water-sediment conditions are diverse at different locations. The velocity and sediment concentration in intertidal zone are higher during the flood tide than those during the ebb tide. The net sediment transport is landward, resulting in a large amount of deposition of sediments on the shoal. However, the ebb current is the dominant one in deep-water area where the net sediment transport is seaward. There exist two circulation systems in plane view on the shoal and in its adjacent deep-water area, which results in the sediment exchanges between the flat and channel and between the estuary and the bay. The landward storm waves erode shoal face, causing the rise of water level on the flat, originating the formation of the vertical circulation system of the sediment transport, and consequently * accelerating the evolution process of the tidal flat.

Distribution of ^137Cs and ^210Ppb in sediments of tidal flats in north Jiangsu Province

Seven cores were collected from different sediment zones of tidal flats at Xin- yanggang in north Jiangsu province in August 2007. Sediment grain-size distribution and radioisotopes of ^137Cs and ^210Ppb analysis were carried out for these cores. Sediment rates of the cores and radioisotopes distribution in surface sediment in different zones of the tidal flat were calculated from the ^137Cs and ^210Ppb activities in sediments cores. The results indicated that each tidal zone had experienced different evolution phases, hydrological dynamics in the tidal flats made the grain-size of the surface sediment change gradually. ^137Cs and ^210Ppb activities on the superficial layer of the cores varied spatially and the reason was discussed. On tidal flats, the fluctuation of ^137Cs and ^210Ppb activities in the cores reflected the special sedimentary characteristics. Vegetation affects the grain-size distribution and the vertical profiles of ^137Cs and ^210Ppb in the upper depths. ^137Cs and ^210Ppb chronology got the comparable average sediment rates on the tidal flat. The characteristics of ^137Cs and ^210Ppb in the cores reflected various depositional dynamical environments in different tidal zones and gave information on the different evolvement phases of the tidal zones. Based on the information of grain-size distribution, texture of the cores, sediment rates and topography, the evolution lines of the tidal flat were reconstructed.

Historical trends in the anthropogenic heavy metal levels in the tidal flat sediments of Lianyungang, China

The sedimentation of metals can preserve the historical record of contaminant input from local and regional sources and provide information on the historical changes in regionalwater and sediment quality. We report the 210Pb activities and the heavy metal （Cd, Cr, Cu, Mn, Pb and Zn）depth profiles from sediment cores retrieved in 2010. The mean sedimentation rates of 0.85-1.5 cm/yr aredetermined by 210 Pbdating. The sediments in the tidal flat have recorded heavy metaldeposition and thus allow the establishment of a connection between the temporal evolution of the heavy metal pollution and the historical changes in the economicdevelopment of Lianyungang. The enrichment factors （EF） are calculated to estimate the level of contamination stored in these sediments. The results show that in the studied sites, Cr and Cudisplay low EF values and are mainly from lithogenic origin. For the other studied trace metals, a great variability in the sedimentary record is observed. Significant anthropogenic enrichment over the last 50 years is revealed at the tidal flat that receives fluvial inputs. Zinc is the elementwith the highest EF values, followed by the order of Pb 〉 Cd 〉 Mn 〉 Cu and Cr. The temporal variations of the heavy metals peakduring the late 1980s to the early2000s and show adecreasing trend afterward. The pollution intensity of the tidal flat isdetermined by using EF and thegeo-accumulation index （Igeo ）,which show that, based on the Igeo scale, the tidal flat of Haizhou Bay is unpolluted to moderately polluted.

Changes in Sedimentation Rate of Tidal Flat and Environmental Significance at Qidong Foreland of the Yangtze Estuary

The sedimentation rate is an important environmental parameter to understand the evolution of coastal geomorphology. The tidal flat around Qidong foreland is located in the junction between Yangtze Estuary and Jiangsu coast,where the land-ocean interactions are strong and highly sensitive to environmental changes. The QDZ-1 core sediments collected at Qidong foreland was analyzed for137 Cs dating and grain size.The results showed that silt is the main sedimentary type with a trend of gradually fining from the bottom to the top,conforming to the sedimentation characteristic of the silt muddy tidal flat. The sedimentation rate could be divided into three distinct stages: 1963 to 1986 was 2. 61 cm/yr,1963 to 2011 was 1. 82 cm/yr,and 1986 to 2011 was 1. 10 cm/yr. Based on these,further explanation was made for the significance of environmental changes. According to the estimation of sedimentation rate,the impact of extreme environmental change was reflected by the sudden increase in sand proportion at the depth of 172. 5 cm. Since the introduction of Spartina alterniflora in the 1970 s,it has played an important role in tidal flat development. The tidal flat has a high sedimentary rate during this time. With continuous accretion of the tidal flat,low tidal flat turns to high tidal flat,the sedimentation rate gradually declines,and tidal flat sedimentation appears.

Impact of the cord-grass Spartina alterniflora on sedimentary and morphological evolution of tidal salt marshes on the Jiangsu coast,China

The tidal flats of the Wanggang area, on the Jiangsu coast, represent the largest continuously distributed coastal wetland in terms of area coverage in China, and the dynamics of tidal flat accretion and erosion is highly complicated. The cord-grass Spartina alterniflora, which was introduced artificially into the Jiangsu coast, has significant influences on the regional tidal flat evolution in terms of deposition rate, spacial sediment distribution patterns and tidal creek morphology. On the basis of the data set of bed elevation and accumulation rate for different periods of time, the applicability of the Pethick - Allen model to the Jiangsu tidal salt marshes is discussed. In addition, caesium-137 dating was carried out for sediment samples collected from the salt marsh of the Wangang area. In combination with the caesium-137 analysis and the data collected from literature, the Pethick - Allen model was used to derive the accumulation rate in the Wanggang tidal flat for the various periods. The results show that the pattern of tidal flat accretion has been modified, due to more rapid accretion following the iatroduction of S. alterniflora to the region. Surficial sediment samples were collected from representative profiles and analyzed for grain size with a laser particle analyzer. The result shows that fine-grained sediment has been trapped by the plant, with most of the sediment deposited on the Suaeda salsa and Spartina angelica flats being derived from drainage creeks rather than the from gently sloping tidal flats. Remote sensing analysis and in situ observations indicate that the creeks formed in the S. alterniflora flat have a relatively small ratio of width to depth, a relatively high density, and are more stable than the other tidal flat creek systems in the study area.

基于挟沙力方法的潮滩剖面形态演变数值模型

为研究波流共同作用下的潮滩剖面形态演变,推导了基于切应力方法的挟沙力公式,开发了基于挟沙力方法的潮滩剖面形态演变数值模型,模拟结果与Delft3D模型基本一致,计算效率明显提升。分别采用切应力方法和挟沙力方法模拟潮滩形态的演变过程,挟沙力方法在潮间带上部区域的模拟效果优于切应力方法,更容易模拟出淤积条件下的上凸形剖面,整体剖面形态更接近实测剖面。计算模拟了潮滩剖面在不同波浪条件下的演变过程,波浪对潮滩形态有极强的塑造作用,入射波高的提升加剧了潮间带的侵蚀,形成明显的下凹形剖面。

Sequence stratigraphic framework and sedimentary model of Shanxi Formation in northeast Zhoukou Depression of the North China Plate

The sequence stratigraphic framework of Shanxi Formation in the northeast Zhoukou Depression was established based on detailed sequence stratigraphical and sedimentological analysis by utilizing the logging and core data of six wells drilled in the eastern tectonic unit of Zhoukou Depression.It was divided into three third-order sequences,namely SQs1,SQs2,and SQs3 from bottom to top.Each sequence can be divided into a transgressive system tract(TST)and a highstand system tract(HST).Furthermore,four sequence boundaries and three maximum flooding surfaces were identified,and they are the bottom interface SBs and maximum flooding surface mfss1 of SQs1,the bottom interface SBs1 and maximum flooding surface mfss2 of SQs2,the bottom interface SBs3 and maximum flooding surface mfss3 of SQs3,and the top interface SBx from bottom to top.Carbonate tidal flat–clastic tidal flat sedimentary system developed in Shanxi Formation in the northeast Zhoukou Depression(also referred to as the study area)under the control of regression.Meanwhile,four sedimentary microfacies were identified in the sedimentary system,which are lime-mud flats,sand flats,mixed flats,and mud flats.The transgression in the study area occurred from the southeast to the northwest.Therefore,the northwestern part is the seaward side,and the southeastern part is the landward side.As revealed by relevant drilling data,SQs1 of the Shanxi Formation is characterized by the development of limestone and carbonaceous mudstone,with limestone,dark mudstone,and carbonaceous mudstone mainly developing.Meanwhile,lime-mud flats were mainly deposited in it.During the periods of SQs2 and SQs3,the sedimentary environment of the study area changed from the carbonate tidal flats to clastic tidal flats as the coastline migrated towards the sea.In these periods,sand flats mainly developed near the maximum flooding surfaces and were relatively continuous in the eastern and southern parts of the transgressive system tract;mixed flats were relatively continuous in the western and northern parts of the transgressive system tract as well as the eastern and southern parts of the highstand system tract;mud flats widely developed in the highstand system tract.Peat flats mainly developed in the period of HSTs2,with coal seams relatively developing in the southeastern part of the study area as revealed by drilling data.The peat flats in SQs2 are favorable hydrocarbon source layers,the lime-mud flats in SQs1 and sand flats formed in the transgression periods of SQs2 and SQs3 constitute favorable hydrocarbon reservoirs,and the mud flats form in the transgressions periods serve as favorable cap rocks.Therefore,the study area features a reservoir-cap assemblage for self-generating and self-storing of hydrocarbon,and the southeastern part of the study area can be taken as a favorable exploration area.

浙江海岸带泥质滩涂物源示踪研究:来自矿物包裹体中磁性矿物的证据

土地资源是浙江沿海地区发展的重要限制性因素。丰富的滩涂资源一直被视为当地最重要的后备土地资源。准确示踪其物质来源,是科学管理滩涂的重要基础。由于在海水中的长期浸泡,矿物被部分溶解,进而影响沉积物的地球化学和矿物学性质,增加示踪结果的不确定性。通过矿物包裹体的磁学特征研究浙江沿海滩涂的物质来源,由于不受海水溶蚀影响,其结果更可靠。对浙江滩涂沉积物中矿物包裹体的环境磁学研究发现:(1)样品的主要载磁矿物依然是磁铁矿;(2)磁铁矿的含量明显降低,饱和等温剩磁(SIRM)值为9.1×10^(-5)—28.6×10^(-5)A·m^(2)·kg^(-1),仅是原样的2%—8%;(3)样品的赤铁矿与磁铁矿比重较原样明显降低。酸处理后样品的磁化率值(χ)仅为1.0×10^(-8)—2.3×10^(-8)m^(3)·kg^(-1),极易受到测量误差的影响,因此无法准确反映样品中磁铁矿含量的空间分布特征,而在强磁场下获得的磁学参数更适合于矿物包裹体的环境磁学研究。基于非磁滞剩磁磁化率(χ_(ARM))、SIRM及饱和等温剩磁退磁参数的散点图和模糊聚类方法可以区分长江和浙江当地河流的物质,是可信赖的物源示踪手段。根据矿物包裹体的磁学特征,提出浙江滩涂沉积物主要来源于当地河流的悬浮颗粒物。

Phosphorous Forms in Sediments and Their Distribution in the Yangtze Estuary and Coastal Areas

Based on analyses of surface and core sediments in the tidal flats of the Yangtze Estuary and coastal areas, the present study reveals phosphorous forms existing in sediments and their distributions. The results show that phosphorus in tidal flat sediments in the study area mainly consists of inorganic phosphorous forms, involving DP, Fe-P, Al-P, and Ca-P and organic phosphorous forms, in which Ca-P and OP are dominant compositions. This finding indicates that spatial distributions of various phosphorous forms are related to sedimentary environments in water and grain sizes of sediments, and are influenced by sewage discharges and effluents from aquacultivation in the coastal areas.

Interaction between Estuarine Microphytobenthos and Physical Forcings: The Role of Atmospheric and Sedimentary Factors

The goal of this study was to analyze microbial mats and biofilms from the lower supratidal area of the Bahía Blanca estuary (Argentina), and explore their relationship with sediments and other physical forcings. Thirteen monthly sediment samples (uppermost 10 mm) were taken and their composition and abundance in microorganisms was determined by microscopy. Physical parameters (solar radiation and sediment temperature at -5 cm) were recorded with a frequency of 5 minutes by a coastal environmental monitoring station. Additionally, sediment grain size and moisture content were determined for distinct layers in the uppermost20 mm, and the rate of inundation of the supratidal area was estimated from tidal gauge measurements. There were significant seasonal differences in the biomass of the microphytobenthic groups considered (filamentous cyanobacteria and epipelic diatoms), with the former consistently making up >70% of the total biomass. The relationships between microphytobenthos and sediment temperature and solar radiation fitted to linear regressions, and consistently showed an inverse relationship between microphytobenthic abundance and either one of the physical parameters. The granulometric analysis revealed a unimodal composition of muddy sediments, which were vertically and spatially homogeneous;additionally, there were significant seasonal differences in water content loss with drying conditions prevailing in the summer. Several Microbially-Induced Sedimentary Structures (MISS) were identified in the supratidal zone such as shrinkage cracks, erosional pockets, gas domes, photosynthetic domes, mat chips and sieve-like surfaces. In contrast to studies from analogous environments in the Northern Hemisphere, we found reduced microphytobenthic biomass in summer, which were explained by increased evaporation/desiccation rates as a consequence of increased radiation, despite frequent tidal inundation. In conclusion, the observed density shifts in the benthic microbial communities are attributable to physical forcings dependent upon seasonal variations in interplaying factors such as sediment temperature, solar radiation and tidal inundation.

潮滩底栖动物对泥沙运动的影响研究进展

潮滩底栖动物通过摄食与掘穴等生命活动能够显著影响泥沙运动过程,是潮滩泥沙运动力学的研究热点之一。分析了潮滩底栖动物的种群空间分布及其作用下的滩面特征,从改变土体性质和水流结构两方面剖析了底栖动物对泥沙运动的影响机制,归纳总结了现场原位观测、室内物理模型试验和数值模拟等研究手段和方法。后续研究可加强潮滩原位泥沙起动测量技术及室内扰动研究装置的改进,结合底栖动物扰动结构形态及种群分布特征,深入研究底栖动物对泥沙起动的影响机制。