人工回灌过程中富里酸和Cu(Ⅱ)对多孔介质悬浮物堵塞的影响

Effect of fulvic acid and Cu(Ⅱ)on the suspended particles clogging of porous media during artificial recharge

地下水人工回灌是解决地下水超采问题的有效措施,悬浮颗粒物堵塞是影响回灌进行的技术瓶颈。目前多数研究聚焦在悬浮物堵塞方面,然而地表回灌水中重金属离子以及腐殖质对多孔介质物理堵塞的影响缺乏研究。本研究采用室内渗流砂柱试验研究富里酸、Cu(Ⅱ)以及两者共存对多孔介质悬浮物堵塞的影响,分别采用高岭土(SS组)、富里酸+高岭土(SS+FA组)、富里酸+Cu(Ⅱ)+高岭土(SS+FA+Cu组)配置模拟回灌用水。研究结果表明:(1)回灌结束时,SS组、SS+FA组、SS+FA+Cu组多孔介质整体相对渗透系数K’分别降至0.233,0.095,0.182。SS组和SS+FA+Cu组在中上层(0~7.50 cm)相对渗透系数K’均降至0.28以下,而在底层(7.50~10.50 cm)相对渗透系数K’仅降至0.45左右,说明2组多孔介质中上层重度堵塞(0<K’<0.30)、底层中度堵塞(0.30<K’<0.60);SS+FA组在各渗流段(0~10.50 cm)相对渗透系数K’均降至0.18以下,说明SS+FA组各渗流段多孔介质均为重度堵塞,相对其它2组,SS+FA组中悬浮物更易向深层迁移。(2)富里酸、Cu(Ⅱ)的存在会改变悬浮颗粒粒径、荷电性及内部氢键作用,从而影响多孔介质的堵塞发生。(3)相对SS组,SS+FA组富里酸的存在会加剧多孔介质堵塞;SS+FA+Cu组多孔介质整体堵塞程度比SS+FA组小,说明Cu(Ⅱ)会缓解富里酸对堵塞的加剧作用。探明富里酸和Cu(Ⅱ)对多孔介质堵塞的影响机制,能够为人工回灌过程中多孔介质堵塞的防治提供理论基础和科学依据。

Artificial recharge is an effective technology to solve the problem of groundwater over-exploitation.Clogging of porous media is the bottleneck affecting groundwater recharge.Most studies have focused on the clogging of suspended particles.Few studies focus on the effects of heavy metal ions and humus in recharge water on the physical clogging.This study conducts sand column experiment to explore the influence of fulvic acid,Cu(Ⅱ)and their coexistence on the suspended particles clogging of porous media.Kaolin(SS group),fulvic acid+kaolin(SS+FA group),fulvic acid+Cu(Ⅱ)+kaolin(SS+FA+Cu group)are added to recharge water,respectively.The results show that(1)the relative hydraulic conductivity(K')of SS group,SS+FA group and SS+FA+Cu group decrease to 0.233,0.095 and 0.182,respectively.The K'of SS group and SS+FA+Cu group in 0−7.50 cm decrease to below 0.28,while the K'in the bottom layer(7.50−10.50 cm)decrease to about 0.45,which indicates that 0−7.50 cm of the porous media in SS group and SS+FA+Cu group are severely clogged(0<K'<0.30)and the bottom layer is moderately clogged(0.30<K'<0.60).The K'of the porous media in SS+FA group among different layers(0−10.50 cm)decrease to below 0.18,which shows that the porous media of SS+FA group in different layers are severely clogged.Compared with the other two experimental groups,the suspended particles in SS+FA group are more likely to migrate into the deeper layer in the sand column.(2)Fulvic acid and Cu(Ⅱ)can change the particle size,charge and internal hydrogen bonding of the suspended particles,thus affect the clogging process.(3)Compared with SS group,fulvic acid aggravates the clogging of the porous media.The clogging degree of the porous media in SS+FA+Cu group is slighter than that in SS+FA group,which indicates that Cu(Ⅱ)would alleviate the aggravating effect of fulvic acid on clogging.Exploring the influence mechanism of fulvic acid and Cu(Ⅱ)on porous media clogging can provide a theoretical and scientific basis for the prevention and treatment of porous media clogging in the process of artificial recharge.