疏浚对练江峡山大溪流域沉积物营养盐的影响分析

以练江峡山大溪流域为研究对象，通过分析疏浚前后10个点位表层沉积物有机质（OM）、总氮（TN）和总磷（TP）浓度以及间隙水和上覆水中氨氮（NH₄ ⁺-N）、TN和TP浓度，以揭示疏浚对表层沉积物营养盐的时空分布及释放过程的影响，并对疏浚后表层沉积物污染状况进行评价。结果表明：疏浚后间隙水和上覆水中TP、TN、NH₄ ⁺-N浓度均显著下降，表层沉积物中OM和TN平均浓度较疏浚前分别下降53.3%、54.5%，有接近1/2点位的表层沉积物出现TP浓度高于疏浚前的现象，疏浚对表层沉积物中营养物移除能力为TN>OM>TP；疏浚后表层沉积物OM、TN和TP污染情况较疏浚前有所改观，但污染程度依然处于较高等级；疏浚后，沉积物中的氮表现为“源”，而磷经历了从“源”到“汇”的转换，表明本次疏浚对表层沉积物间隙水中氮的内源释放有促进作用，对磷的内源释放存在抑制作用，这与本次疏浚的深度、沉积物的理化性质及赋存环境的改变有关。

Effects of dredging on nutrients in sediments in Xiashan Daxi Basin of Lianjiang River

To reveal the effects of dredging on the temporal and spatial distribution and the release process of nutrients in surface sediments, the contents of organic matter (OM), total nitrogen (TN) and total phosphorus (TP) of the surface sediments as well as the concentrations of ammonia nitrogen (NH4 +-N), TN and TP of the interstitial water and the overlying water at 10 points from Xiashan Daxi Basin of Lianjiang River were analyzed before and after dredging, and the pollution status of surface sediments after dredging was also evaluated. The results showed that TP, TN, and NH4 +-N concentrations in interstitial water and overlying water decreased significantly after dredging. The average concentrations of OM and TN of surface sediments decreased by 53.3% and 54.5%, respectively, compared with those before dredging. TP concentration of surface sediment was higher than that before dredging at nearly half of the points, and the ability of dredging to remove nutrients in surface sediments was TN>OM>TP. The pollution of OM, TN and TP in surface sediments after dredging improved compared with that before dredging, but the pollution level was still high. After dredging, the nitrogen in the sediments displayed as "source", and phosphorus changed from "source" to "sink", indicating that this dredging promoted the internal release of nitrogen in the interstitial water of surface sediment and inhibited the internal release of phosphorus. This was related to the dredging depth, the changes in the physicochemical characteristics of the sediments and the occurrence environment.