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The Jianggang sand ridges (JSR) in the southwestern Yellow Sea are a radiating tidal sand ridge system that plays crucial roles in ecological preservation, coastal protection, and terrestrial resource supply. Clay and silt fractions constitute important sediment components of the Jianggang sand ridges. In this study, the Sr-Nd isotopes of clay fractions and the Pb isotopes of K-feldspar in the silt fractions, along with their elemental geochemistry, are investigated to reveal the provenance and transport patterns of clay-size and silt-size sediments in the study areas. The results show that in both the clay-size sediments and the K-feldspar of the silt-size sediments, Ba exhibits the highest content, with the ranges of 432.24 μg/g to 531.05 μg/g and 398.02 μg/g to 2822.36 μg/g, respectively. In contrast, Lu shows the lowest abundance (<0.5 μg/g and <0.1 μg/g, respectively). The ⁸⁷Sr/⁸⁶Sr and ε_Nd(0) values of the clay fraction vary from 0.7158 to 0.7265 and from −14.65 to −10.92, respectively. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb of K-feldspar in silt fraction are 17.959~18.429, 15.450~15.689, and 38.066~38.551, respectively. Through the MixSIAR model, it is suggested that the Yangtze River Mouth is the dominant contributor to clay-size sediments in both the onshore and offshore sand ridges (53.9 ± 8.8% and 51.9 ± 8.4%, respectively), followed by the Modern Yellow River Mouth and the Old Yellow River Delta (sum of contributions: <36%). For the silt fraction, the primary sediment sources of the onshore and offshore sand ridges are the Yangtze River Mouth (46.8 ± 5.5%) and the Old Yellow River Delta (42.4 ± 5.3%), while the Modern Yellow River contributes less than 16%. The Northern Chinese Deserts and the Korean rivers make only minor contributions to both fractions. Elemental and isotopic tracers indicate that the silt-size and clay-size sediments derived from the Modern Yellow River are transported southward along the Jiangsu coast by the Subei Coastal Current. Meanwhile, the silt fraction from the Yangtze River Mouth is carried northward along the coast under the influence of the Subei Coastal Current, whereas the clay fraction of it has another longer path, which moves through the central Yellow Sea and migrates southward along the Jiangsu coast to the Jianggang sand ridges under the influence of the Yellow Sea Warm Current. This study enriches the geochemical dataset of the southern Yellow Sea. Full article

A two-dimensional hydrodynamic model for the waters off the coast of Jiangsu, where there are radial sand ridges (RSRs) (hereinafter, the RSR area), was established based on measured topographic, tide level and tidal current data. Considering the complex topographic and geomorphic characteristics of the RSR group in this area, an unstructured grid was used for the calculation. A four-layer refinement was applied to the grid from outside to inside to better fit the complex topography. The simulations were performed to examine the response of the hydrodynamic environment to the morphology of the RSRs in three scenarios, namely, when there are natural RSRs, no RSRs, and partially reclaimed RSRs. When there are no or partially reclaimed RSRs, the tidal current field still exists in a radial pattern in the RSR area. The radial tidal current field is relatively stable and is not controlled by the morphologies of the RSRs. The topographic changes do not alter the distribution pattern of the radial tidal current field but do affect the local current fields. When there are no RSRs, the flood currents can directly reach Jianggang. Under practical conditions, the RSRs block the tidal currents during a flood tide to some extent. This phenomenon is particularly pronounced when the RSRs are partially reclaimed. For example, during an ebb tide, when the tidal currents encounter sand ridges or reclamation areas, their streamlines bend, and they flow around the obstacles. This change will affect the material transport, sediment deposition and seabed erosion. Full article