白洋淀夏季入淀区沉积物间隙水-上覆水水质特征及交换通量分析

为揭示白洋淀夏季入淀区上覆水-间隙水氮磷营养盐相互作用，本研究于2019年7月对白洋淀主要6条入淀河流取样，通过分析上覆水、间隙水水质特征以及营养盐在沉积物-水界面的扩散通量，评估了营养盐扩散对沉积物与上覆水的影响.结果表明白洋淀水质呈弱碱性；溶解氧（DO）含量较低，为沉积物内源污染物的释放提供了厌氧环境；氨氮（NH₄⁺-N）浓度在0.35~1.76mg·L^-1，作为主要给水来源的潴龙河淀区最高；硝氮（NO₃^--N）浓度在0.75~1.97mg·L^-1；溶解性总氮（TDN）浓度在0.99~2.70mg·L^-1，位于自然区的S2瀑河含量最高；溶解性总磷（TDP）浓度在0.03~0.15mg·L^-1，靠近居民区的白沟引河含量最高.间隙水氨氮浓度在5.24~10.64mg·L^-1，是上覆水体的10倍，内源污染严重；硝氮浓度在0.36~0.79mg·L^-1；溶解性总氮浓度在5.36~12.02mg·L^-1，是上覆水体的5倍；溶解性总磷浓度在0.03~0.3mg·L^-1.应用综合污染指数法对水质进行评价发现间隙水污染程度远高于上覆水，各采样点呈现出严重污染状态.对NH₄⁺-N、TDN和TDP进行交换通量分析显示，NH₄⁺-N的扩散通量在1.71~7.43mg·（m²·d）^-1，作为保定市纳污河流的府河采样点内源氨氮向上覆水扩散速率最快；TDN的扩散通量除白沟引河较低，其余5个采样点均值达到9.11mg·（m²·d）^-1，夏季水体中溶解氧含量较低且沉积物-水界面TDN浓度差较大，导致沉积物中含氮营养盐在厌氧条件下大量释放到上覆水中，对水质造成严重污染；萍河采样点TDP的扩散通量是负值表示上覆水体的磷污染物向沉积物聚集的状态，剩余5个采样点的扩散通量范围在0.03~0.16mg·（m²·d）^-1，表现出磷营养盐向上覆水释放的状态.扩散通量显示内源污染物是上覆水污染物的重要来源，为有效治理入淀区水质，沉积物氮磷营养盐的清淤处理迫在眉睫.

Analysis of Water Quality and Exchange Flux of Interstitial Water-Overlying Water in Sediments of Baiyangdian Entrance Area in Summer

In order to reveal the interaction of overlying water-interstitial water nitrogen and phosphorus nutrient salt in summer at the entrance region of Baiyangdian Lake, this study sampled six main rivers in the region during July 2019. An analysis of the overlying water and interstitial water quality characteristics and the diffusion flux of applied nutrients at the sediment-water interface revealed the effects of nutrient diffusion on sediments and overlying water. The overlying water analysis showed that the water quality was slightly alkaline in the Baiyangdian Lake. The content of dissolved oxygen (DO) was lower, which provided an anaerobic environment for the release of endogenous pollutants from sediments. The ammonia nitrogen (NH₄⁺-N) ranged from 0.35 to 1.76 mg·L^-1, and the content of ammonia nitrogen was the highest in the Zhulong River, which was the main source of water supply. The nitrate nitrogen (NO₃^--N) content ranged from 0.75 to 1.97 mg·L^-1. The total dissolved nitrogen (TDN) ranged from 0.99 to 2.70 mg·L^-1, and the content of TDN was the highest in Puhe River. The content of total dissolved phosphorus (TDP) was 0.03 to 0.15 mg·L^-1, and the content of TDP was the highest was Baigouyin River, which is near the residential area. The results indicated that the content of ammonia nitrogen in the interstitial water was between 5.24 and 10.64 mg·L^-1, which was 10 times that of the overlying water, and endogenous pollution in the former was severe. The nitrate nitrogen content ranged from 0.36 to 0.79 mg·L^-1. The total dissolved nitrogen content was between 5.36 and 12.02 mg·L^-1, which was 5 times higher than that of the overlying water. The total dissolved phosphorus was between 0.03 and 0.3 mg·L^-1. According to integrated pollution index, the degree of interstitial water pollution was much higher than that of overlying water, and the sampling points are seriously polluted. The exchange flux analysis of NH₄⁺-N, TDN, and TDP demonstrated that the diffusion flux of NH₄⁺-N was between 1.71 and 7.43 mg·(m²·d)^-1, and the diffusion rate of endogenous ammonia nitrogen to the overlying water was fastest in Fu River, the absorbing river in Baoding. The diffusion flux of total dissolved nitrogen was lower in the Baigouyin River, and the other five sample points averaged 9.11 mg·(m²·d)^-1. In summer, the dissolved oxygen was lower and the water-sediment had a larger concentration difference, which led to massive nitrogen nutrient of sediment in anaerobic conditions released to the overlying water in great quantities that caused the serious pollution. The diffusion flux of dissolved total phosphorus showed that the sediment of Pinghe River acted as a "sink" of phosphorus nutrients, and the other sampling points ranged from 0.03 to 0.16 mg·(m²·d)^-1, showing the state of phosphorus nutrient released upward to the overlying water. Finally, diffusion flux indicated that endogenous pollutants are crucial sources of overlying water pollutants. In order to effectively control the water quality in the entrance area, desilting the nitrogen and phosphorus nutrient salt of sediment is urgently required.