再生水补给下湿地沉积物中营养盐空间分布特征

以北京市近郊汉石桥湿地为研究对象，分析再生水补水对湿地沉积物中营养盐空间分布特征的影响，通过采集湿地25个表层沉积物样品和3个柱状沉积物样品，分析了沉积物中有机质（OM）、总氮（TN）和总磷（TP）含量，揭示了湿地沉积物中OM、TN、TP水平空间分布和垂直分布特征。结果表明:汉石桥湿地沉积物中OM、TN、TP含量整体处于较高水平，三者含量平均值分别为70.65，4.72，，0.96 g/kg；在水平空间分布上，OM和TN表现出一致的分布特征，均为上游含量低、中游和下游含量高，TP含量在不同区域间无显著差异；在垂直空间分布上，表层0~10 cm沉积物中OM、TN、TP含量最高，呈现随剖面深度增加含量先降低后逐渐稳定的趋势；化学计量特征表明，湿地表层沉积物中OM、TN、TP呈现显著正相关性（P<0.01）；综合污染指数表明汉石桥湿地沉积物整体上呈中-重度污染。再生水补给加剧了湿地沉积物中氮、磷元素的富集，湿地沉积物营养盐空间分布受补水中残存污染物浓度、水动力条件和湿地地形结构的影响，在水流速度缓慢、滞水区域，沉积物中营养盐含量明显升高，再生水补给是湿地富营养化的重要推力。

SPATIAL DISTRIBUTION OF SEDIMENT NUTRIENTS IN A WETLAND WITH RECLAIMED WATER SUPPLEMENT

To reveal the impact of reclaimed water supplement on the spatial distribution characteristics of nutrients in Hanshiqiao wetland sediments, 25 samples of surface sediments and 3 samples of core sediments were collected to explore the spatial and vertical distribution characteristics and stoichiometric characteristics of total organic matter (OM), total nitrogen (TN) and total phosphorus (TP). The results showed that:the average OM, TN and TP contents in the surface sediments in Hanshiqiao wetland were 70.65, 4.72, 0.96 g/kg, respectively, which were significantly higher than those in other wetlands. The contents of OM and TN were higher in the midstream and downstream than that in the upstream, while TP was evenly distributed in the whole wetland. In vertical direction, the content of OM, TN, and TP was the highest in the surface layer of sediment (0~10 cm), and showed a tendency of decreasing first and then gradually stabilizing with the increase of sediment profile depth, indicating the risk of C, N, P in surface sediment releasing to the overlying water. Stoichiometric characteristics indicated that there were significant positive correlations between OM, TN and TP in surface sediments (P<0.01). The comprehensive pollution evaluation and organic pollution evaluation showed that the whole wetland was in moderate to severe pollution level. The reclaimed water supplement intensified the accumulation of nutrients in the wetland sediments. The spatial distribution of nutrients in the wetland sediments was affected by the residual concentration of nutrients in the recharge water, hydrodynamic conditions and the wetland topographic features. In the areas with slow water flow and mostly stagnant water, the nutrient content in the sediments increased significantly. The replenishment of reclaimed water was an important driving force for wetland eutrophication.