中文摘要：

磷是长江口外邻近海域潜在的限制性营养元素,沉积物中磷的转化与保存对于指示区域环境变化和物质循环具有重要的作用.通过对长江口外低氧区和非低氧区柱状沉积物中磷和氧化还原敏感参数的分析,探讨了沉积物中磷的形态、分布及其环境意义.研究表明,Detr-P是沉积物中磷主要的赋存形态;其次是Org-P、Fe-P和Auth-P,Exch-P对总磷的贡献〈5%;磷的含量与分布受陆源输入和早期成岩作用的影响;活性磷组分在沉积-保存过程中发生了明显的形态转化,Auth-P主要来源于Fe-P和Org-P的转化.长江口低氧区沉积物中磷的保存与陆源输入和水体环境变化密切相关,磷的形态能够较好地反映区域环境变化.低氧区与非低氧区沉积物中活性磷的分布具有一定的差异性,突出表现在低氧区沉积物具有更高的C/P值.研究区域内DRP的释放通量为0.90~1.13μmol·（cm~2·a）~（-1）;磷的埋藏效率高于70%,其中Detr-P的埋藏效率约为100%,Fe-P和Org-P分别为38%和26%.Auth-P是活性磷最主要的埋藏形态,大约51%的Auth-P来源于Fe-P和Org-P的转化.长江口低氧区磷的埋藏效率低于东海内陆架海域,低氧现象降低了磷的埋藏效率,并可能对富营养化等生态环境问题产生深远影响.陆源输入的变异显著影响长江口沉积物中磷的组成,流域磷的输入与河口初级生产和低氧等一起深刻影响着长江口磷的循环模式.

英文摘要：

Phosphorus（ P） is a potential limiting nutrient in Changjiang Estuary. Sedimentary P preservation and regeneration play an important role in indicating regional environmental changes and buffering P limitation in the water column. A series of coring experiments was implemented in the hypoxic area of Changjiang Estuary to explore sedimentary P speciation and distribution and their environmental significance. The results showed that the contents and distributions of P in the cores were largely influenced by terrestrial loading,and Detr-P was the dominant P form in the sediments,followed by Org-P,Fe-P,and Auth-P,whereas Exch-P was the minor phase of Tot-P（〈5%）. Auth-P was predominantly yielded by Org-P and Fe-P transformations. P preservation in Changjiang Estuary was significantly related to terrestrial inputs and environmental changes in the water column. P speciation in cores tracked the regional environmental changes effectively. Distribution of reactive P in the hypoxic area was significantly different from that in the oxic area,with fairly high C/P ratios. The benthic diffusive flux of DRP in the study area ranged from 0. 90 to 1. 13 μmol·（ cm~2·a）~（-1）. Tot-P burial efficiency（ PBE） was higher than 70% and the PBE for Detr-P was nearly 100%,whereas the PBEs for Fe-P and Org-P were38% and 26%,respectively. Auth-P was the dominant fraction of reactive P preserved in the sediments,and about 51% of Auth-P originated from Fe-P and Org-P transformations. The PBE in the hypoxia area of Changjiang Estuary was fairly lower than that in the continental shelf of the East China Sea. Hypoxia leads to a decrease in the PBE,which would have long-term influence on ecological environmental problems,especially eutrophification. Changes in terrestrial inputs played a key role in P composition in the sediments;the P loads of Changjiang River coupled with primary production and hypoxia greatly affected the P cycling in the Estuary.