Study On Distribution And Denthic Fluxes Of Nutrients In Sediments Of Yellow Sea And East China Sea

The paper was based on the surface sediment samples of ten sites and cylindrical sediment samples of six sites which were collected by the box sediment sampler in the South Yellow Sea and the north of the East China Sea in August 2008. The distributions of the TP, TN, IP and IN in the surface sediment and the five cylindrical samples were discussed quantitatively and then the changing characteristics of distributions of five dissolved nutrients which were silicate(SiO₃-Si), phosphate (PO₄-P), nitrate(NO₃-N), nitrite(NO₂-N) and ammonium(NH₄-N) in interstitial water were also discussed of eatuary, acoast and central area of Yellow Sea and East China Sea. Cylindrial samples of four sites had been selected to do the exchange flux culture experiments at the sediment-water interface in the laboratory and calculated the exchange flux of dissolved nutrients, and then the influences of oxidation -deoxidi zation condition to the exchange flux were discussed.The distribution characteristic of nutrients in the sediment interstitial water of the South Yellow Sea and the north of the East China Sea was that the high ammonium content was a representative distribution characteristic of the nutrients in the interstitial water. The concentration scopes of NH₄-N, NO₃-N, NO₂-N, SiO₃-Si and PO₄-P in the surface sediment interstitial water were 28.97-179.90μmol·L^-1, 1.71-27.29μmol·L^-1, 0.18-2.83μmol·L^-1, 100.39-454.50μmol·L^-1 and 14.07-43.75μmol·L^-1. respectively. The concentrations of PO₄-P and NH₄-N in the north of the East China Sea were higher than those in the South Yellow Sea and the concentration of SiO₃-Si in the open sea of the East China Sea was higher than that in the South Yellow Sea and the offshore areas.In terms of the vertical distribution in the interstitial water, NH₄-N was still the chief constituent of nitrogen, The concentration of NH₄-N in interstitial water was increased with depth increased within 5cm of surface, the vertial distribution of NO₃-N,NO₂-N,PO₄-P content were decreased with depth increased, and the content of SiO₃-Si on the decline except station F0508 in hupi reef coin carrying current, else all in rising trend with depth increased. The distribution characteristics of total nitrogen, total phosphorus and exchangeable nitrogen and phosphorus in the sediment in the South Yellow Sea and the north of the East China Sea were that in surface of sediment, the highest contents of TN and TP were in the middle and coastal areas of the South Yellow Sea where the water was shale. The changing scopes of TN and TP were 0.07-0.70 mg·g^-1 and 0.43-2.13 mg·g^-1 respectively. The turbidity caused by hydrodynamic agitation acclerated the decomposition of organic matter so that the largest ratios of IP and IN of the TP and TN were at the sites which were located at the boundary of the Yellow Sea and the East China Sea. In trems of the whole research sea areas, the organic nitrogen was the chief and the distribution of TN was controlled by the distribution of organic nitrogen. While the average IP accounted for 45.82% of TP, and 76.7% in the YangzeRiver Delta, so the distribution of TP was mainly controlled by IP. But the IP just accounted for 19.8% in the South Yellow Sea, so the distribution of TP was mainly controlled by OP.The vertical distributions of TP and TN decreased with the depth and the changing scopes of TN and TP were 0.14-0.77 mg·g^-1 and 0.38-2.54 mg·g^-1 respectively. The content of IN was higher at the surface and did not change much with the depth. Its scope of concentration was 0.02-0.18 mg·g^-1. In all the cylindrical sediment samples, NH₄-N was the main exchangeable nitrogen. The distribution of IP changed largely in the depth researched in the paper but did not change largely between the surface sediment and bottom sediment expect the site located at the boundary of the Yellow Sea and the East China Sea in which the content was higher at the surface sediment. The content scope was 0.25-0.42mg/g.Because the infulence of deposition rate,the burial fluxes of nutrient with unit area greater than the content of nutrients in sediment, the burial fluxes in a year of TN, TP in long-shore currents sedimentary area, coin carrying current sedimentary area and mix sedimentary area of yellow were 1.71×10⁷,7.02×10⁷; 5.61×10⁷,16.1×10⁷å’Œ1.57×10⁷,17.9×10⁷ kg·a^-1; mix sedimentary area, hupi reef coin carrying current shale sedimentary area of east china sea were 1.81×10⁷,3.22×10⁷å’Œ1.06×10⁷,17.9×10⁷ kg·a^-1The exchange fluxes of nutrients at the sediment-water interface of the South Yellow Sea and the north of the East China Sea were that NO₃-N of all the research sites in the South Yellow Sea and the north of the East China Sea transferred from the overlying water to the sediments, and the largest was -11.72 mmol·m^-2·d^-1 in the East China Sea Mid-ocean, and NO₂-N also transferred from the overlying water to the sediments, the largest release flux of NO₂-N was in the inshore of the South Yellow Sea which was -4.06 mmol·m^-2·d^-1. On the contrast, NH₄-N all released from sediments to the overlying water, the maximum value was 2.15 mmol·m^-2·d^-1 at the boundary of the Yellow Sea and the East China Sea. PO₄-P all diffused from overlying water to the sediments, the largest exchange flux was -9.38 mmol·m^-2·d^-1 in the East China Sea Mid-ocean. SiO₃-Si all diffused from sediments to the overlying water, and the highest value was 38.65 mmol·m^-2·d^-1 which was also located at the boundary of the Yellow Sea and the East China Sea. The research result was similar to the other sea areas.Nitrogen and the air were accessed separately to the culture of the sediment of the research sites at different oxidation-deoxidization conditions and the results showed that the exchange of NH₄-N at the sediment-water interface was the main part of the exchange of inorganic nitrogen and the exchange rate which was accessed nitrogen was higher than the air. The rate of transfer of NO₂-N from overlying water to sediments under nitrogen condition was larger than the oxygen condition. The flux of NO₃-N transferred from overlying water to sediment in reductive environment was higher than that in oxidization environment. The exchange rate of PO₄-P in reductive environment was lower than that in oxidization environment. Silicate always released from sediments to the overlying water whether in oxidization environment or in reductive environment.Sediment in different sedimentary area of Yellow Sea and East of China Sea separatly were the sink of NO₃-N, NO₂-N and PO₄-P and the source of NH₄-N and SiO₃-Si. The contribution of NH₄-N to sea area primary productivity was samller in sedimet of Yellow sea and East of China Sea sedimentary area; The contribution of SiO₃-Si to primary productivity in long-shore currents sedimentary area of yellow sea was 11.05%; The contribution in mix sedimentary area, hupi reef coin carrying current shale sedimentary area, vestigital sedimentary area in East of China Sea was 193%, 8.77% and 83.6%.