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In coastal marine environment, acid volatile sulfide (AVS) is usually one of the most important or reactive phases. We report first set of data on AVS contents in sediments of south Yellow Sea. The AVS contents are less than 11.14 µmol/g (dry sediment weight), with most below 3 µmol/g in the sediment of south Yellow Sea. The average AVS contents of surface sediments (0~10 cm) range from 0.02 µmol/g to 2.30 µmol/g, with an average value of 0.94 µmol/g. There are three zones with high AVS content in sediments and they are dominated by the Yellow River sediments and the old Yellow River transported by coastal current and the Yellow Sea Cold Water Mass, respectively. The AVS content in sediments of these three zones increases initially with burial depth, reaching a maximum at about 13 cm (6cm for east section), then decreases. One core from the south section, however, shows an exceptionally high AVS content at the surface (4.96 µmol/g) and a minimum at around 7 cm burial depth. This AVS abnormal profile is located at the place where enrichment of methane at shallow layer reported. Except those three high value areas, the AVS content of sediment is very low and does not show significant variations. It is apparent that sediment AVS content is closely related to the organic matter in different sediment environment, since the content of Fe is quite high (average 3.13%) in the sediment of Yellow Sea.

This work purposes a general mean velocity and a suspended sediment concentration (SSC) model to express distribution in every point of the cross section of turbulent shear flow by using a probability density function method. In order to solve turbulent flow and avoid multifarious dynamical mechanics, the probability density function method was used to describe the velocity and concentration profiles interacted on directly by fluid particles in turbulent shear flow. The velocity profile model was obtained by solving for the profile integral with the product of the laminar velocity and probability density, through adopting an exponential probability density function to express probability distribution of velocity alteration of a fluid particle in turbulent shear flow. An SSC profile model was also created following a method similar to the above and based on the Schmidt diffusion equation. Different velocity and SSC profiles were created while changing the parameters of the models. The models were verified by comparing the calculated results with traditional models. It was shown that the probability density function model was superior to log-law in predicting stream-wise velocity profiles in coastal currents; and the probability density function SSC profile model was superior to the Rouse equation for predicting average SSC profiles in rivers and estuaries. Outlooks for precision investigation are stated at the end of this article.ABSTRACT

Based on the finite volume method of computational fluid dynamics and k-ε turbulence model equations, combines the volume of fluid method with the moving mesh method to deal with air-water interface, a 3d unsteady paddlewheel-induced pond circulation while running and shutting off the paddlewheel machineries across the air-water interface is simulated in this paper. In this simulation, some monitory points are arranged at the section far ahead and near the front of the aerator to monitor the evolution of velocity in the pond circulation. Growing and decaying characteristics of velocity are analyzed. Analysis result shows that: At the location near the front of the aerator, growing characteristics of velocity are significantly different between upper layer and lower layer; the main decaying characteristic of velocity is that velocity decays rapidly after the moment when machineries shut off. At the location far ahead the aerator, the growing characteristic curves of velocity fit for the quadratic polynomial function, and the decaying characteristic curves of velocity fit for the exponential function.

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