闸控河流潜流带沉积物-水界面营养盐分布及交换通量研究

Nutrient Distribution and Exchange Flux at the Sediment-water Interface in the Hyporheic Zone of the Sluice-controlled River

为揭示闸控河流潜流带营养盐“源/汇”特征,本研究以淮河流域沙颍河槐店闸河道为研究对象,于2021年1月中旬实施了蓄水调控背景下的原位沉积物采集实验,通过分析氮磷营养盐在沉积物-水界面的分布与扩散通量,识别了潜流带营养盐“源/汇”角色,探明了闸控河道内源风险。结果表明:1)间隙水NH_(4)^(+)-N与TP浓度分别是上覆水体的6.5与1.1倍,表明沉积物-水界面营养盐存在显著浓度梯度,极易造成潜流带NH_(4)^(+)-N、TP向上覆水迁移;2)经综合污染指数评价得出,上覆水与间隙水水质处于重污染或严重污染状态,且闸下污染程度显著大于闸上,表明蓄水调控对闸下水域产生了负面影响;3)沉积物-水界面的NH_(4)^(+)-N、NO_(3)^(-)-N、TP交换通量分别为0.39~10.07、-3.45~-2.04、-0.09~0.17 mg/(m^(2)·d),表明沉积物为NH_(4)^(+)-N的“源”,NO_(3)^(-)-N的“汇”,TP的“源”和“汇”;4)空间上,S2(闸下消力坎处)、S4(闸下营养盐沉积段)是氮磷营养盐的主要富集场所,其中,S2主要以氨态氮形态存在,对水质影响贡献率(59.03%)最大,氮磷比(13.25)最高,适宜藻类爆发性生长;5)S2内源NH^(+)_4-N释放是蓄水调控背景下槐店闸河道内源防治的关键,减少外源污染物输入、优化闸坝调度对改善闸控型河道水环境至关重要。

To reveal the "source/sink" characteristics of nutrients in the hyporheic zone of sluice-controlled river, this study took Huaidian sluice channel of Shaying River in Huaihe River Basin as the research object, and carried out an in-situ sediment collection experiment under the background of water storage regulation in mid-January, 2021. By analyzing the distribution and diffusion flux of nitrogen and phosphorus nutrients at the sediment-water interface, the "source/sink" role of nutrients in the hyporheic zone was identified, and the endogenous risk of sluice-controlled rivers was ascertained. The results show that: 1) the concentrations of NH^(+)_4-N and TP in interstitial water are 6.5 and 1.1 times of those in overlying water, respectively, which indicates that there is a significant concentration gradient of nutrients at the sediment-water interface, which easily leads to the migration of NH^(+)_4-N and TP in the hyporheic zone to overlying water;2) According to the comprehensive pollution index evaluation, the water quality of overlying water and interstitial water is in a state of heavy pollution or serious pollution, and the pollution degree under the sluice is significantly greater than that above the sluice, which indicates that the regulation of water storage has a negative impact on the waters downstream the sluice;3) The exchange fluxes of NH^(+)_4-N, NO^(-)_(3)-N and TP at the sediment-water interface are 0.39-10.07,-3.45--2.04 and-0.03-0.17 mg/(m^(2)·d) respectively, indicating that the sediment is the "source" of NH^(+)_4-N, “sink” of NO^(-)_(3)-N, and both “source and sink” of TP;4) Spatially, S2(at the stilling basin downstream the sluice) and S4(at the nutrient deposition section downstream the sluice) are the main enrichment places of nitrogen and phosphorus, among which S2 mainly exists in the form of ammonia nitrogen, with the largest contribution ratio to water quality(up to 59.03%) and the highest nitrogen to phosphorus ratio(13.25), which is suitable for the explosive growth of algae;5) The release of endogenous NH^(+)_4-N in S2 is the key to the endogenous prevention and control of Huaidian sluice River under the background of water storage regulation. Reducing the input of exogenous pollutants and optimizing the regulation of sluices are crucial to improving the water environment of sluice-controlled rivers.