Phosphorus Forms In Sediments In The Yangtze River Estuary And Its Adjacent Sea

Phosphorus(P) is essential for growth and reproduction of marine plankton,and it isthe foundation of marine primary productivity and food chain.The primary source of P inocean is river input.Sediment is an important reservoir of phosphorus. Particulatephosphorus exists in different forms with different physical and chemical properties andbioavailability. The determination of the content of different forms of phosphorus andexploring the influencing factors help us understand the impact of nutritional status ofdownstream and estuary area. Study on morphological characteristics of phosphorus in thecore sediments reflects the influence of natural environment and social environmentchanging on the area. According to the change of phosphorus forms in the sediment,we caninfer and invert the environmental conditions of the corresponding period.Sediment servesas the source and sink of nutrients, and plays an important role in the budget and dynamicsof nutrients recycling in the marine water. Therefore, a study on the diffusion fluxes ofnutrients between bottom sediment and water layer in this typical sea area is necessary.Two cruises were carried out in June2011and August2013.The contents of differentforms of P in surface sediment and core sediment were analyzed using the improvedSEDEX method. Combined with the particlate characteristics,oxidationreductionpotentialand isotope,particulate phosphorus distribution rule was discussed.Primary conclusions arelisted as follows:The particulate P forms in surface sediments of Changjiang Estuary wereanalysed in Augest,2013.Various forms of phosphorus in surface sediments in the studyarea were mainly controlled by source and sediment type, with significant spatialdifference.Bioavailable phosphorus consisited of higher content of organic phosphorus,while the unbioavailable phosphorus consisited of higher content of detrital phosphorus.InChangjiang estuarine sediments,exchangeable P,organic P,authigenic P,iron-bound Pandrefractory P had the similar distribution pattern with higher contents appeared just out of the Changjiang Estuary and Hangzhou Bay.Three core sediments in Changjiang Estuary and its adjacent area were sampled inJuly,2011.The exchangeable phosophorus increased with the increasing depth.Detritalphosphorus and refractory phosphorus did not change with the depth basically.Iron boundphosphorus and orgnic phosphorus were basically followed the distribution: in the surfaceand subsurface sediment had high value,while decreased with the increasing depth.The content of different P forms in the core sediments is controlled by threefactors:(1)Oxidation reduction potential effected the content of iron bound phosphorus.With the oxidation environment enhanced, the content of iron bound phosphorusincreased.(2)Authigenic phosphorus content increased with the increasing content of activephosphorus content in the pore water.(3)The constantly redeposition and resuspensionprocess in the mixed layer had an important impact on bioavailable phosphorus verticaldistribution.