Endogenous contamination from the newly submerged sediment may have an impact on the water quality of the Danjiangkou Reservoir, the water source of the middle route of the South-to-North Water Diversion Project. In this study, in situ sediment samples were collected at different locations (Guojiashan (DJK1), Kongqueyuan (DJK2), Shijiagou (DJK3), Shiqiao Wharf (DJK4), and Songgang Wharf (DJK5) from the north to the south) of the Danjiangkou Reservoir and the upstream tributary using a columnar sediment sampler and statically cultured in laboratory, and the distribution and release of endogenous N and P from the sediment were investigated based on a double-membrane diffusion model. The results showed that the P contents in the main reservoir and the upstream tributary followed the order of . IP accounted for the largest proportion (47.10-59.70%) of total phosphorus (TP), while LP accounted for only a small proportion (0.10-0.90%) of TP. There is a significant difference in the spatial distribution of P at different sampling points, especially for the OP content (226.90 mg·kg^-1) with a coefficient of variation of 26.90%. The contents of different forms of P and NH₄⁺-N decreased from the upstream tributary to the main reservoir, which was mainly attributed to the land use type. In the vertical distribution, the contents of different forms of P in DJK4 and DJK5 decreased with the increase of sediment depth. The contents of NH₄⁺-N and PO₄^3--P in the sediment interstitial water of DJK4 and DJK5 were higher than those in the overlying water. In addition, the contents of NH₄⁺-N and PO₄^3--P were higher in DJK5 than that in DJK4. The static culture experiments showed that N and P were mainly released from the sediment-overlying water interface to the overlying water. The release rate of NH₄⁺-N and PO₄^3--P ranged from 13.08 mg·(m²·d)^-1 to 21.39 mg·(m²·d)^-1 and from 3.06 mg·(m²·d)^-1 to 6.02 mg·(m²·d)^-1, and the release amount calculated based on the double-membrane diffusion model was  t·a^-1 and  t·a^-1, respectively. Thus, endogenous contamination from the newly submerged land is an important factor affecting the water quality of the Danjiangkou Reservoir.

中文翻译：

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丹江口水库内源性氮和磷的释放：双膜扩散模型分析

南水北调中线中线水源丹江口水库的水质可能影响新近被淹没的沉积物的内源性污染。在这项研究中，从北部到南部的不同位置（国家山（DJK1），孔雀苑（DJK2），石家沟（DJK3），石桥码头（DJK4）和松岗码头（DJK5））收集了原地沉积物样本。丹江口水库和上游支流采用柱状沉积物采样器并在实验室中进行静态培养，并基于双膜扩散模型研究了内源性N和P从沉积物中的分布和释放。结果表明，主储层和上游支流中的P含量顺序为：。IP占总磷（TP）的比例最大（47.10-59.70％），而LP仅占总磷的一小部分（0.10-0.90％）。P在不同采样点的空间分布存在显着差异，尤其是OP含量（226.90 mg·kg ^-1），变异系数为26.90％。从上游支流到主要水库，P，NH ₄ ⁺ -N形态不同，含量减少，主要归因于土地利用类型。在垂直分布中，DJK4和DJK5中不同形式的P含量随着沉积深度的增加而降低。NH ₄ ⁺ -N和PO ₄ ^3-的含量DJK4和DJK5的沉积物间隙水中的P值高于上覆水中的-P。另外，DJK5中的NH ₄ ⁺ -N和PO ₄ ^3- -P的含量比DJK4中的高。静态培养实验表明，氮和磷主要从沉积物上覆水界面释放到上覆水。NH ₄ ⁺ -N和PO ₄ ^3- -P的释放速率为13.08 mg·（m ² ·d）^-1至21.39 mg·（m ² ·d）^-1和3.06 mg·（m ² · d）^-1至6.02 mg·（m ² ·d）^-1，根据双膜扩散模型计算的释放量为  t·a ^-1和 t·a ^-1。因此，新淹没土地的内源性污染是影响丹江口水库水质的重要因素。