不同溶解氧条件下沉积物-水体系磷循环

磷是控制富营养化水平和水环境演变的关键元素.沉积物-间隙水体系是影响近海水体磷循环的主要界面，而上覆水溶解氧（DO）则是影响这一界面磷转化行为和界面通量的控制因子.针对近海环境特征，利用沉积物多管培养装置进行室内实验和动力学过程研究，探讨了DO变化对沉积物-间隙水体系磷的赋存形态、转化和释放的影响.结果表明，上覆水DO变化对沉积物-水界面溶解态活性磷酸盐（DRP）交换通量有显著的影响，低氧条件下沉积物具有较富氧和无氧更高的DRP交换通量；富氧条件下沉积物中总磷在表层富集量最高，具有较高的保存能力，低氧和无氧状态下沉积物对磷的保存能力降低；低氧条件下沉积物中铁结合磷的还原溶解和有机质的矿化是水体的主要磷源.在不同DO条件下，磷的转换呈现出差异化的特征，其中低氧状态下沉积物-水界面的变化和理想的早期成岩模式最为接近.可见，溶解氧对沉积物-间隙水体系磷的释放和转化有着显著的影响，是控制磷循环的重要因素.

Phosphorus Cycling in a Sediment-water System Controlled by Different Dissolved Oxygen Levels of Overlying Water

Phosphorus (P) is the major limiting element of marine primary productivity, which controls the eutrophication and evolution of the environment. The variability in dissolved oxygen (DO) in overlying water is the key factor affecting the regional P cycle. In this study, a series of laboratory simulation experiments and numeral simulations were conducted using a multi-tube sediment columnar culture device under different DO levels, and the effects of DO changes on the occurrence form of P and the release and transformation of P in a sediment-water system were evaluated. The results showed that the change in DO had a significant effect on P transformation, thereby influencing the exchange flux of dissolved active phosphate (DRP) at the sediment-water interface, and the sediment had a higher DRP exchange flux under hypoxic conditions in comparison with oxic and anoxic conditions. Furthermore, the total P preservation was the highest in oxygen-enriched sediments, whereas the preservation ability of P decreased in sediments under hypoxic and anoxic conditions. The reductive dissolution of iron-bound P and mineralization of organic matter in sediments under low oxygen conditions were the main P sources of the water column. The transformation of P exhibited differentiated characteristics under different DO conditions, among which the change in the sediment-water interface in the hypoxic state was most similar to the ideal early diagenetic model. Our study documented that the P transformation and release were largely controlled by the variation in DO, which has important environmental significance in the coastal area.