潏河冬季潜流带水交换对沉积物间隙水水质的影响

潜流带作为河流地表水-地下水系统相互作用的交汇区域带,是影响河水、间隙水与地下水水质的主要驱动力之一,对河流生态系统中的水文循环、污染物迁移转化等过程具有重要的意义.本研究采用基于一维热扩散对流方程的温度梯度法,于2016年12月对潏河研究河段21个测试点位进行了沉积物的野外原位垂向温度同步测试,并对其与沉积物间隙水中阴阳离子含量之间的关系进行了分析.结果表明:21个测试点位的潜流带水交换方式均为上升流,水交换量值变化范围较大,左右两岸水交换量值均大于河道中心水交换量值,影响其变化的主要因素是河床地形和沉积物粒径大小;Ca~(2+)、Na~+、Mg~(2+)、HCO_3~-和SO_4~(2-)在沉积物间隙水中的平均含量更接近于其在地下水中的平均含量,而K~+、NH_4~+和Cl~-在沉积物间隙水中的平均含量与其在地下水中的平均含量具有显著差异性;此外,沉积物间隙水中主要阴阳离子含量在河流横断面具有明显的横向空间变化特征,与河道中心相比,河道左右两岸沉积物间隙水中Ca~(2+)、Mg~(2+)和SO_4~(2-)含量均较高,而NH_4~+和Cl~-含量较低;采用Pearson相关分析和线性拟合方法发现,潜流带水交换量与沉积物间隙水中Ca~(2+)、Mg~(2+)和SO_4~(2-)含量呈正相关关系,与K~+、NH_4~+、Cl~-含量呈负相关关系,而与Na~+、HCO_3~-含量的相关性未通过检验,说明其不存在显著相关性.

Influence of hyporheic water exchange on quality of sediment pore water for the Juehe River in winter

Hyporheic zone is the ecotone between groundwater and surface water. It is one of the controlling factors for the quality of river water, pore water and groundwater, which has great significance in the hydrological cycle and contaminant transportation. Twenty one test sites in the Juehe River were selected to conduct the in-situ synchronous test of vertical temperature profiles in December 2016. One-dimension heat advection-diffusion equation was used to estimate the pattern and magnitude of hyporheic water exchange. Its relationship with main cations and anions in sediment pore water was subsequently analyzed. The results showed patterns of upward hyorheic water exchange and relatively large magnitude of water exchange exsited in 21 test sites. Stream topography and sediment grain size were the main elements to influence this distribution. The average concentrations of Ca²⁺, Na⁺, Mg²⁺, HCO₃^- and SO₄^2- in sedeiment pore water was comparatively close to those in groundwater. However, for K⁺, NH₄⁺ and Cl^-, the average concentrations in sediment pore water were significantly different from those in groundwater. Furthermore, spatial variability existed across longitudinal section. Specifically, the concentrations of Ca²⁺, Mg²⁺ and SO₄^2- in the left and right banks were higher than the central channel, but for NH₄⁺ and Cl^-, the pattern was reversed. Pearson correlation analysis and linear fit demonstrated good agreement between the water exchange magnitude and concentrations of Ca²⁺, Mg²⁺ and SO₄^2-. For the concentrations of K⁺, NH₄⁺ and Cl^-, a negtive correlation with water exchange magnitude existed. However, the relationship between the concentrations of Na⁺ and HCO₃^- and water exchange magnitude failed to pass the test, indicating no significant correlation.