中文摘要：

磷是一种重要的生源要素,在河口、边缘海的初级生产中发挥重要作用,了解沉积物中磷的形态分布和迁移转化有助于深入了解该区域生态系统动力学。于2013年3月在长江口及邻近海域采集了表层沉积物样品,利用水淘选方法对沉积物进行了分级,并采用化学连续提取法分析了未分级和分级沉积物样品中的6种磷形态含量：可交换态磷、活性有机磷、铁结合态磷、自生磷灰石磷、碎屑磷和难分解有机磷,讨论了该区域沉积物中磷的形态分布、选择性输运过程和迁移转化。沉积物中总磷含量在14.0~18.4μmol/g,其中碎屑磷是其主要成分,占54.5%,其次是有机磷和难分解有机磷,分别占到15.1%和13.1%。不同粒级沉积物中磷形态含量不同,可交换态磷、活性有机磷、铁结合态磷、自生磷灰石磷和难分解有机磷随粒级增加含量逐渐降低,而碎屑磷主要集中在粗粒级（大于32μm）沉积物中。基于各粒级磷形态的质量分布,发现小于32μm粒级的沉积物中各磷形态含量从长江口向浙闽沿岸逐渐增加,向外海方向逐渐减小,而大于32μm沉积物的变化趋势与此相反,体现了不同形态磷的选择性输运。随粒径增大,总有机碳对有机磷比值（TOC/Or-P）先降低后升高,在大粒级沉积物中,TOC/Or-P比值较高主要是因为陆源有机碳贡献较高,而在小粒级沉积物中,主要是由于有机磷的迁移和转化更为活跃,体现了细颗粒物中有机磷相对有机碳的优先分解。本研究表明,从分级的角度可以对河口、边缘海的磷循环有一个更全面的认识。

英文摘要：

Phosphorus is an important biogenic element playing a key role in primary production in estuarine and coastal environments.Knowledge of the speciation and transformation of phosphorus in sediments contributes to a better understanding of the ecosystem dynamics in these regions.Surface sediment samples were collected in the Changjiang Estuary and adjacent shelf in March,2013,and were separated into different size fractions via water elutriation.P speciation was analyzed by a modified sequential extraction method（SEDEX）to obtain six sedimentary P forms：exchangeable or loosely-sorbed P（Ex-P）,organic P（Or-P）,Fe-bound P（Fe-P）,authigenic P（Au-P）,detrital P（De-P）and refractory P（Re-P）in order to investigate the distribution and transformation of different phosphorus forms in the sediments of this area.The total phosphorus（TP）in sediments ranged from 14.0-18.4μmol/g,and De-P was the major form and accounted for 54.5% of the TP,followed by Or-P and Re-P,which accounted for 15.1% and 13.1%,respectively.The contents of phosphorus forms in different size fractions were different.Ex-P,Or-P,Fe-P,Au-P and Re-P decreased gradually with increasing grain size,while De-P was concentrated in coarser particles（more than 32μm）.Based on the mass distribution of phosphorus speciation,less than 32μm fractions gradually increased from Changjiang Estuary to Zhe-Min Coast and decreased seaward,while the variation tendency of more than 32μm fractions was opposite,reflecting the selective transport of phosphorus of different forms.With the increase of particle size,TOC to Or-P（TOC/Or-P）ratios first decreased and then increased.High TOC/Or-P values in the larger size fractions were possibly caused by the high terrestrial OC contributions in this fraction,while in fine particles,high TOC/Or-P values are largely attributed to the more efficient transformation and remobilization of Or-P,indicating preferential regeneration of Or-P relative to OC.This study shows that a more comprehensive understanding