Nitrogen sediment-water exchange

It has been shown that the main part of both soluble (53%) and particulate (> 99%) nitrogen was inputting into the Yellow sea from Northern China in spite of only 30% excess of river water discharge from the Chinese area. Totally riverine input from watershed drainage basin was equal to 52% from input values (2,581 kt/yr). Both wet and dry depositions were responsible for 20 and 22 % from input values with relatively small values of N fixation in marine waters. Denitrification is the main output items (37%) with similar values of sedimentation and water exchange with East the China Sea (7 and 8% from total input) and with negligible values of losses as N2O (< 1%). 

Thus, the following links of nitrogen biogeochemical cycle were accounted for mass balance calculations in Northern-East Asia and the whole East Asian domain input — deposition, fertilizers, biological N fixation, import of food and products, riverine fluxes and output — crop uptake, denitrification, volatilization, runoff, sedimentation and sea water exchange. All calculations were condncted for 1994-1997 and the mean values were used. 

The main factors governing the turnover of nitrogen at the sediment-water interface are the total amount of proteinaceous matter, diffusion, ion exchange with clay minerals, and bioturbation. 

Engvall, A.-G. (1977). Nitrogen exchange at the sediment-water interface. Ambio Sp. Rep. 5,141-146. 

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...

Henriksen, K., Hansen, J.I., and Blackburn, T.H. (1980) The influence of benthic infauna on exchange rates of inorganic nitrogen between sediment and water. Opheha 1, 249-256. 

The northern portion of Chesapeake Bay was studied. This upper section of the bay can be classified as a classic salt-wedge type estuary (15). The humic materials used in this study were extracted from several cores of sediments. Two one-meter cores gravity corer. The cores of sediments were then divided into sections and squeezed under nitrogen to remove most of the interstitial water. The squeezed sediments were then dried, weighed and washed with distilled water. The sediments were then washed with 0.5N KCl to remove iron hydroxides, carbonates and exchangeable cations from the clays. Some of the fulvic acids are lost in this acid wash procedure. The humic materials were then extracted from the remaining solids by a O.IN NaOH solution. 

Smith-Morrill, L. 1987. The exchange of carbon, nitrogen, and phosphorus between the sediments and water-column of an Amazon floodplain lake. Ph.D. Thesis. University of Maryland, p. 209. 

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