The planar photosynthetically available radiation (PAR),turbidity and concentration of chlorophyll a (chl a),were measured at 26 stations in the Huanghai (Yellow) Sea during a cruise of China SOLAS from 19 to 27 March 2005.Due to low chl a (<0.35 mg·m^-3) in upper layers (above 5 m),suspended particulate matter became the major factor that influenced the turbidity in early spring.The calculated vertical diffuse attenuation coefficient of PAR,K_PAR,varied with water depths with a maximum value in the upper 5 m layer.The mean K_PAR in survey area was 0.277±0.07 m^-1 that is considerably higher than most of the other case 2 waters.Within the survey area,K_PAR also showed distinct regional characteristics,corresponding to the distribution of turbidity.Based on measurements,the relationship between K_PAR and turbidity as well as chl a was established.It was suggested that suspended particulate matter plays an important role in light attenuation in the Huanghai (Yellow) Sea in spring.

Water temperature, turbidity, chlorophyll-a and suspended sediment concentration (SSC) were investigated at 61 stations of eight sections in the southern Huanghai Sea (HS) and the East China Sea (ECS) during the summer (28 June to 15 July) of 2006. The horizontal distribution of suspended parti culate matter (SPM) displayed a high concentration inshore and a low value offshore. The maximum value can reach 10.4 mg/dm³, which can be found at the Changjiang River mouth. For the same site, the SSC was generally higher at the bottom than on the surface. In the vertical direction, distribution characteristics of turbidity can be divided into two types:in the southern HS high values at the bottom while low values on the surface, and in the ECS high values inshore with low values offshore. The thermocline in the HS and the Taiwan Warm Current in the ECS could be important factors preventing the SPM from diffusing upward and seaward. Even the typhoon Ewiniar was not able to work on the major sediment transport under the thermocline during the observation.

A three-dimensional wave-current-sediment coupled numerical model is developed to understand the sediment transport dynamics in the Zhujiang (Pearl) River Estuary (ZRE), China. The model results are in good agreement with observed data, and statistics show good model skill scores. Numerical studies are conducted to assess the scenarios of suspended sediment in the ZRE under the effects of different forcing (river discharges, waves, and winds). The model results indicate that the estuarine gravitational circulation plays an important role in the development of estuarine turbidity maximum in the ZRE, particularly during neap tides. The increased river discharge can result in a seaward sediment transport. The suspended sediment concentration (SSC) in the bottom increases with both wave bottom orbital velocity and wave height. Because of the shallow water depth, the effect of waves on sediment in the west shoal is greater than that in the east channel. The southwesterly wind-induced wave affects the SSC more than those resulting from the northeasterly wind, while the northeasterly wind-driven circulation has a slightly greater influence on the SSC than that of the southwesterly wind. However, a steady southwesterly wind condition favors the increase of the SSC in the Lingding Bay more so than a steady northeasterly wind condition. If the other forcings are same, the averaged SSC under a steady southwesterly wind condition is about 1.1 times that resulting from a steady northeasterly wind.

Sediment convergence and resuspension are the two major mechanisms in forming turbidity maximum (TM) in the Changfang Estuary.Sediment convergence is mainly controlled by the interaction between runoff and tidal current, the mixing of freshwater and salt water, the former forming tidal TM, whereas the latter forming brackish TM.The TM in the Changjiang Estuary is characterized by a combination of tidal TM and brackish TM, which varies temporally and spatially.

Here, we report the results of high-resolution nitrate measurements using an optical nitrate profiler (in situ ultraviolet spectrophotometer, ISUS) along transect across a high-turbidity shelf (East China Sea) and a low-turbidity shelf (Chukchi Sea). The ISUS-measured nitrate concentrations closely reproduced the results measured by conventional bottle methods in low-turbidity waters. However, for high-turbidity waters of the East China Sea (salinity<30), a correction factor of 1.19 was required to match the standard bottle measurements. The high-resolution ISUS data revealed subtle spatial variability (e.g., a subsurface nitrate minimum) that may have been missed if based solely on bottle results. Four main structures of the nitracline on the East China Sea are apparent from the ISUS nitrate profile. High-resolution nitrate data are important for studying nitrate budgets and nutrient dynamics on continental shelves.

On the basis of the time series of AVHRR data from NOAA satellites and the geographical information system PURSIS, fluctuations of the plume front and the turbidity maximum in the Hangzhou Bay, reflected by the distributions of temperature and suspended sediment concentration respectively, are studied in view of long-term behaviors or seasonal and tidal cycles. The data suggest that the effect of front plays an important role in the development of the turbidity maximum close to the Changjiang Estuary > while the effect of tide dominates over the development of another very turbid water situated in the shoal areas in the southern Hangzhou Bay.

Real-time observations in the field and numerical simulations (with Delft3D) were combined to study the formation, distribution and the relevant influencing factors of turbidity maximum (TM) in the Zhujiang (Pearl River) Estuary (ZE). The spatial distribution pattern of the TM varies with the longitudinal distributions of salinity and suspended sediment concentration (SSC). The SSC is enhanced and the TM is intensified during dry seasons, whereas the center of the TM moves upstream by a distance of 10 km during wet seasons. The formation of the TM is influenced by a complex combination of numerous factors, including tides, river discharges and topography, wherein sediment resuspension and vertical circulation dominate the formations and variability of the TM.

Distributions and sources of total organic carbon(TOC)in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects of estuary water on the continuously increasing terrigenous organic carbon from the Changjiang River are also explored through variations of organic carbon content and water quality indicators. Results show that, hydrodynamics exert important influences on distributions of organic carbon in the turbidity maximum of Changjiang Estuary. For their redistribution effect of terrigenous organic carbon within the moving layer in the whole region, variations from land to sea are not indicated by surficial and vertical average values of TOC and total nitrogen (TN) contents in core sediment, as well as organic stable carbon isotopes in surface sediments. However, on the long-time scale, the trend of terrigenous organic carbon decreasing from land to sea is still displayed by variations of stable carbon isotopic average values becoming heavier from land to sea. Previous studies have shown that high content of Chl a cannot appear in the Changjiang Estuary in despite of adequate nourishment supply, because photosynthesis of phytoplankton is constrained by high suspended sediment concentration(SSC). However, an area with a high content of Chl a occurs, which may be caused by resuspended benthic algae with bottom fine grain-size sediments. Tremendous pressures are imposed on the environment of Changjiang Estuary, because of ultrophication trends and special hydrodynamics. Phytoplankton bloom area tends to extend from the outer sea to the mouth of Changjiang River.

Turbidity currents represent a major agent for sediment transport in lakes, seas and oceans. In particular, they formulate the most significant clastic accumulations in the deep sea, which become many of the world's most important hydrocarbon reservoirs. Several boreholes in the Qiongdongnan Basin, the northwestern South China Sea, have recently revealed turbidity current deposits as significant hydrocarbon reservoirs. However, there are some arguments for the potential provenances. To solve this problem, it is essential to delineate their sedimentary processes as well as to evaluate their qualities as reservoir. Numerical simulations have been developed rapidly over the last several years, offering insights into turbidity current behaviors, as geologically significant turbidity currents are difficult to directly investigate due to their large scale and often destructive nature. Combined with the interpretation of the turbidity system based on highresolution 3D seismic data, the paleotophography is acquired via a back-stripping seismic profile integrated with a borehole, i.e., Well A, in the western Qiongdongnan Basin; then a numerical model is built on the basis of this back-stripped profile. After defining the various turbidity current initial boundary conditions, including grain size, velocity and sediment concentration, the structures and behaviors of turbidity currents are investigated via numerical simulation software ANSYS FLUENT. Finally, the simulated turbidity deposits are compared with the interpreted sedimentary bodies based on 3D seismic data and the potential provenances of the revealed turbidites by Well A are discussed in details. The simulation results indicate that a sedimentary body develops far away from its source with an average grain size of 0.1 mm, i.e., sand-size sediment. Taking into account the location and orientation of the simulated seismic line, the consistence between normal forward simulation results and the revealed cores in Well A indicates that the turbidites should have been transported from Vietnam instead of Hainan Island. This interpretation has also been verified by the planar maps of sedimentary systems based on integration of boreholes and seismic data. The identification of the turbidity provenance will benefit the evaluation of extensively distributed submarine fans for hydrocarbon exploration in the deepwater areas.

In order to discuss the content distributions and fluxes of heavy metals in suspended matters during a tidal cycle in the turbidity maximum around the Changjiang (Yangtze) Estuary, the contents of heavy metals (Zn, Pb, Cd, Co and Ni) have been analyzed. During a tidal cycle, the average contents of heavy metals are in the order of Zn >Ni >Pb >Co >>Cd. The average contents in ebb tide are generally higher than that in flood tide. However, at the inshore Sta. 11, influenced by the contamination from the nearby waste treatment plant, the average contents of Zn and Ni in flood tide are higher than those in ebb tide and at the offshore Sta. 10, the content of Cd in flood tide higher than that in ebb tide due to marine-derived materials. The five heavy metals, mainly terrigenous, are transported towards east-northeast, and settle down with suspended matters in the area between Sta. 11 and Sta. 10. Influenced by marine-derived materials, the flux value of Cd does not alter significantly with obviously changing in flux direction towards northwest. The source of heavy metals, the salinity of water and the concentration of suspended matters are the main factors controlling the content distributions of heavy metals during a tidal cycle. There is a positive correlation between the contents of heavy metals (Zn, Pb, Co and Ni) and the salinity of water, while the opposite correlation between the contents and the concentrations of suspended matters. Because of marine-derived materials, the content of Cd is not correlated with the concentration of suspended matters and the salinity of water.