Biogeochemical Processes of Phosphorus

A six-step extraction method was used to operationally discriminate the chemical species of P (e.g., authigenic apatite and refractory organic P). The six-step extraction procedure separates the major reservoirs of sedimentary P into six pools, including loosely adsorbed P (LSor-P), iron-bound inorganic P (Fe-P), leachable organic P (Lea-OP), authigenic apatite (CFAP), detrital apatite (FAP), and refractory organic P (Ref-OP). The location of studied cores was as shown in Fig. 3.35. 

Anal 4ical results for the concentrations of IP, OP, and TP in surface sediments are listed in Table 3.26 (Liu et al., 2004). The results indicate that IP is the most important P speciation representing 73% 98% of the TP. The 

In the YS, the concentrations of IP increased slightly with depth, whereas OP and TP fell gradually from the surface to depth at station T4. This might indicate that slow decomposition of P occurs at station T4 and a transfer within P fractions exists at station T4. 

The differences in phosphorus speciation among stations were significant at the 95% confidence level. Sediment phosphorus distribution ranges were 0.8% 2% for LSor-P, 3% 10% for Fe-P, 4% 19% for Lea-OP, 3%-15% for CFAP, 35% 66% for FAP, and 14% 36% for Ref-OP (Fig. 3.37). This can partially explain the higher proportions of FAP relative to the other species of P in the sediments of the YS. 

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Biogeochemical Processes of Phosphorus and Silicon of Surface Sediments in the southern Bohai Sea... 

Song JM, Luo YX, Lii XX, Li PC (2002a) Biogeochemical processes of phosphorus and silicon in southern Bohai Sea surface sediments. Chin J Oceanol Linrnol... 

The purpose of this paper is to outline the physical environmental factors involved in the functioning of the intertidal system and briefly review the impact on the biogeochemical processing of nitrogen, phosphorus and silicon. Consideration of saltmarshes is excluded. Discussion is focused on the often extensive areas of non-vegetated sand and mud flats that are uncovered by the tides on a daily basis and for which there is a limited amount of published information. 

Of the forms of transferable phosphorus in surface sediments, OSF-P was the predominant form, accounting for 10.7% of the total phosphorus CF-Si was the predominant form of transferable silicon, accounting for 0.05% of the total silicon. There was a certain similarity in the diagenesis of various forms of phosphorus. The content of the transferable form of silicon accounted for less than 0.12%, indicating that previous research on the biogeochemical process of silicon by means of the determination of the total silicon content cannot give us any valuable information (Song et ah, 2003). 

The major ions are removed from seawater by a variety of biogeochemical processes. These processes collectively operate at slower rates than those acting on the biolimited and particle-scavenged elements, such as phosphorus and iron. This causes the major ions to spend very long periods of time dissolved in seawater before being removed to the sediments. 

From an elemental perspective, most of the mass of POM and DOM is carbon. Thus, DOC and POC concentrations are generally representative of the entire DOM and POM pools. Because DOC and POC concentrations are more easily measured than those of the other elements (nitrogen, phosphorus, oxygen, and hydrogen), far more data has been collected on their concentrations and reactivity as compared to that of DON, PON, DOP, or POP. DOM and POM concentrations are not measured for technical reasons and because the total mass of organic matter provides little insight into the biogeochemical processes responsible for its formation and destruction. 

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