Nitrogen forms in marine sediment play an important role in its biogeochemical cycling.Up to now,most studies focus on total nitrogen(TN),organic nitrogen(ON) and inorganic nitrogen and could not yield integrated information on nitrogen cycling because different nitrogen forms contributing to their cyclings are different.In this work,nitrogen of Bohai Sea sediment in natural size was divided into transferable and untransferable parts by sequential extraction method for the first time.Estimation of transferable nitrogen and its function in sediment-water exchange showed that the contributions of different nitrogen forms in nitrogen recycling vary on time scale.Estimation indicated that IEF-N and OSF-N exist mostly at the surface of the sediment grain,and act as dominant participator in recycling,IMOF-N and CF-N are mainly present inside the sediment grain and contribute little to recycling.The nitrogen cycling budget for Bohai Sea shows that the contribution of pelagic recycling (74.4%) to primary productivity is much more than benthic recycling(26.1%). Analysis of the correlation between sediment nitrogen and primary production showed that it is very close.IEF-N acts as a “buffer pool” for nitrogen nutrient which can enhance primary productivity.Benthos bioturbation is conducive to enhancement of mineralization,which results in high NH+ 4 and NO- 3 distribution in deep sediments.Contribution of nitrogen forms in recycling varies on time scale.The absolute contribution of each state is consistent with its content in sediment,which has the sequence OSF-N (84.6%)>IEF-N (13.0)> IMOF-N (1.4%)>CF-N (1.0%).Untransferable nitrogen account for 69.15% of TN, among which 49% is due to inclusion in sediment grain interior.
As the important resource and sink of biogenic element nitrogen, marine sediments have significant effect on nitrogen biogeochemical cycling. It is the key of this research to make clear nitrogen forms in sediments. Nitrogen biogeochemical cycling in marine sediments is a complex process. This research is focused on nitrogen early diagenesis, counter-eutrophication, nitrogen cycling (including mineralization, nitrification and denitrification), and nitrogen flux at the sediment-water interface. Various theory models and analysis methods have been built up. By now, systematic knowledge of nitrogen cycling has been obtained. Therefore, little was known about the distribution and forms of nitrogen, the relationship between nitrogen and other nutrients cycling, the effect of strong metals in nitrogen cycling, especially idiographic forms of nitrogen in different grain-size sediments in various sea areas. To research on the distribution and forms of nitrogen in sediments is the key for learning how nitrogen forms and transports in sediments, utilization and burying degree of nitrogen, the effect of nitrogen in the biological chain, and the relationship between nitrogen and marine biological activities.The effect of nitrogen on marine ecological evolvement and marine biogeochemical cycling must be deeply studied. The ocean is the last region rich in resources that has not been completely exploited. How to exploit it properly is an important problem.
以D 甘露醇为原料,先与丙酮缩合合成1,2,5,6 二 O 异亚丙基 D 甘露醇,再对剩下的3,4位上的羟基进行甲醚化,同时脱去异亚丙基保护基团,经两步反应合成了目标化合物3,4 二 O 甲基 D 甘露醇,产率约60%。抗肿瘤活性表明IC50(宫颈癌细胞样)为4 5μg/mL,IC50(口腔表皮样癌细胞样)为10μg/mL。
