The Bohai Sea sediments

Ma HB, Song JM, Lii XX, Yuan HM (2003) Nitrogen forms and their functions in recycling of the Bohai Sea sediments. Geochimica 32(l) 48-54 (in Chinese with Enghsh abstract)... 

Fig. 2.17. Vertical profiles of OC in the Bohai Sea sediments. A Bohai Bay B Huanghe River Estuary C Liaodong Bay...

The Bohai Sea is one of the main China marginal seas, which has its own particular state and hydrography characteristics. This includes the topography, chemical environment, hydrography, sediment pattern, riverine input, and biological characteristics. 

The sediments in the Bohai Sea are generally fine (Fig. 1.12, Jiang et al., 2004). They consist of soft clay mud (sediment with sizes smaller than 0.01 mm amounts to a portion of more than 70%), fine silt mud (sediment with sizes smaller than 0.01 mm amounts to a portion of 50% 70%), coarse silt, and fine sand. In Liaodong Bay the coarse silt (0.1 0.05 mm) and fine sand (0.25 0.1 mm) dominate in the sediment. In Laizhou Bay the sediment consists of silt deposits, whereas in the central basin fine sand spreads widely. At the Laotieshan waterway (entrance to the Bohai Sea), the tidal flow is very strong, the area is often eroded and therefore the sediment particles are coarse there. The constituents of SPM in the Bohai Sea are mainly inorganic... 

Fig. 1.12. Sediment type distribution of the Bohai Sea. 1, Gravel 2, Medium sand 3, Fine sand 4, Coarse silt 5, Fine silty mud 6, Silty clay mud 7, Clay mud 8, Shell 9, Nodule (Jiang et al., 2004) (With permission from Elsevier s Cop5u ight Clearance Center)...

The sources of SPM are the adjacent rivers and resuspension. Atmospheric dust transported by the wind is a further source of SPM in the Bohai Sea (Qin and Li, 1982). The seasonal and regional variation of SPM concentration is evident, which is closely related to the flow and the sediment concentration of the rivers. 

The Huanghe River annually discharges 1.08x10 t of sediment into the Bohai Sea. A portion of this sediment load is then transported southward via the Yellow Sea Coastal Waters (YSCW) and the Jiangsu Coastal Waters (JCW) into the East China Sea. 

An outline of the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea and the feature of surface sediments in China s seas are given in chapter 1. The contents and methods of studying the marine sediment-seawater interface are summarized in chapter 1 and chapter 2. The chemical features of overlying waters of marine sediments are described in chapter 3. 

Song JM, Ma HB, Li XG, Yuan HM, Li N (2004) Geochemical characteristics of adsorbed inorganic nitrogen in the south Bohai Sea sediments. Oceanol Limnol Sin 35(4) 315-322 (in Chinese with English abstract)... 

Abstract In this chapter the biogeochemical processes in the Bohai Sea are described. The main contents deal with the distributions, transformation, and their controlling factors of carbon, nitrogen, phosphorus, silicon, and pollutants such as heavy metals and persistent organic pollutants (POPs) in the seawaters and sediments. In the Bohai Sea, human activity and riverine input are the most important controlling processes in the variation of biogenic elements and pollutants. 

Liaodong Bay (Fig. 2.11) is located in the northeastern part of the Bohai Sea (longitude 119°50 00"-121°08 01" E, latitude 38°20 00"-39°59 05" N). More than 10 rivers enter the bay, and a mass of sand inputs the bay every year from these rivers. The sediments in the eastern bay mainly consist of sand and muddy sand. But in the central and southern bay, sediments are sandy mud... 

The vertical distribution of OC in Bohai sea sediments is shown in Fig. 2.17. The core sediments can be divided into three parts surfacial/subsurfacial... 

Distributions and Transformations of Nitrogen in the Bohai Sea 163 Table 2.7. OC decomposition rate constants (yr ) in surface/subsurface sediments... 

Table 2.14. The exchange flux (mniol/(m d)) of nitrogen at sediment-water interface in the Bohai Sea (Zhang et ah, 2004) (With permission from Elsevier s Copyright...

Fluxes across the Sediment-Water Interface of P and Si in the Bohai Sea... 

The fluxes of phosphorus and silicon exchange between the sediment and seawater in the Bohai Sea are shown in Table 2.18 (Liu et al., 2004). Liu et al. (2004) reported the following results. In the autumn cruise, the dissolved oxygen concentration of near-bottom waters was 5.60 6.99 mg/L, saturation of 80% 99%, at our incubation stations. In the spring cruise, the dissolved oxygen concentration of near-bottom waters increased to 9.63 10.5 mg/L, saturation of 105% 112%. This implied that the exchange fluxes of nutrients in the Bohai Sea were better approached by incubation under air conditions, while the exchange fluxes of nutrients under N2 conditions should be considered as an approach of anaerobic conditions. 

For incubation with air, the phosphate, DOP, and TDP fluxes varied from -0.043 to A).001, A).068 to 0.001, and -0.071 to -0.042 mmol/(m -d), respectively, which showed that phosphorus moved from water to sediment. In the incubation with N2, the fluxes of phosphate ranged from -0.003 to 0.063 mmol/(m d), indicating a transport from sediment to water. The fluxes of DOP and TDP varied from -0.036 to 0.087 and from -0.071 to 0.151 mmol/(m d), respectively, which indicated that they moved from sediment to water at stations A2 and E3, and in the opposite direction at stations El and G2 (Table 2.18). The sediments in the Bohai Sea are mainly terrestrial detritus, on average, composed of 71% clay, 23% silt, and 6% sand. Taking into account the sediment type, the geometric mean fluxes of phosphorus were calculated and shown in Table 2.18. The average fluxes of PO , DOP, and TDP... 

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