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Biogeochemistry Of Biogenic Elements In The Intertidal Flat And Adjacent Seawater Within The Changjiang (Yangtze River) Estuary

Posted on:2007-10-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:L GaoFull Text:PDF
GTID:1100360212958132Subject:Physical geography
Abstract/Summary:PDF Full Text Request
Knowledge on the nutrient profiles in sediment porewater as well as benthic nutrient fluxes in the large estuarine areas is of fundamental importance to a series of questions, such as the distribution patterns and biogeochemical cycles of biogenic elements in estuarine systems, the impacts of the estuary and the Maximal Turbidity Zone on the terrestrial fluxes delivered by the rivers, as well as the contributions of the estuarine, coastal, and shelf areas to the inventories and budgets of biogenic elements worldwide.From March 2005 to February 2006, twelve investigations were carried out once a month in Dongtan intertidal flat within the Changjiang (Yangtze River) estuary. The present paper mainly focuses the porewater nutrient profiles and nutrient fluxes at the sediment-overlying interface at three typical sampling locations (they are chosen to represent the high, middle, and low marsh, respectively) in Dongtan. In the current paper, Chapter 1 is the introduction, in which a review of previous researches about the relevant aspects is presented. In Chapter 2, the study area and the sampling locations, as well as all the sampling and analytical methods involved in the paper are provided. From Chapter 3 to Chapter 8 are the detailed results and discussions, among them Chapter 3 mainly focuses on the solid phase characters of sediments in Dongtan, Chapter 4 and Chapter 5 deal with the nutrient profiles in sediment porewaters, and Chapter 6 and Chapter 7 is primarily about the nutrient fluxes at the sediment-overlying water interface. Moreover, in Chapter 8, quasi-simultaneous observations were carried out for 25 h (approximately two M2 tidal cycles) at twelve stations within Changjiang estuary adjacent to Dongtan to study the influence of tidal currents on the nutrient distributions in the seawater column; also, a sample box model is established to study the impacts of all the possible contribution pathways to the nutrient inventories in the assigned area. Finally, in Chapter 9 is the summary of all the above results.In Chapter 3, contents of biogenic silica (BSi) were measured in three sediment columns representing the high, middle, and low marsh of Dongtan, respectively. Due to the abundant terrestrial material inputs, sequential extraction method is chosen to extract BSi from sediment. Our results indicate that the BSi levels in the Dongtan sediments are lower (generally no more than 0.5 Si%) than other study areas worldwide, but similar to those in the Bohai and Yellow Sea. The high clay contents...
Keywords/Search Tags:sediment, nutrient, porewater, early diagenesis process, seasonal variation, biogenic silica (BSi), numerical modeling, sediment-water interface, bioturbation, dissolved oxygen, denitrification, M2 tide, budget, Dongtan intertidal flat, Chongming Island
PDF Full Text Request
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