Influence of Soil Colloids on Ni Adsorption and Transport in the Saturated Porous Media: Effects of pH, Ionic Strength, and Humic Acid  
Zhanxi Wei  
Qinghai 906 Engineering Survey and Design Institute, Qinghai Bureau of Environmental Geology Exploration, Xining 810007, China; [EMAIL_ADDRESS] (Z.W. ); [EMAIL_ADDRESS] (Y.W. ); [EMAIL_ADDRESS] (Y.W.) Yidan Zhu  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
[PERSON]  
Yuanzhao Wu  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Wenli Ma  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Yongxia Hou  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Wenqing Zhang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Yuesuo Yang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Wenqing Zhang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Yuesuo Yang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Wenqing Zhang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
Yuesuo Yang  
Qinghai Research Center for Geo-Environment Protection and Disaster Prevention Engineering Technology, Xining 810007, China  
W.M.W.Z. nanomaterials, can transport from soil to groundwater, resulting in groundwater contamination [6; 7]. Generally, colloids have the characteristics of large specific surface areas and high activity, causing them to exhibit strong affinities to hydrophobic contaminants, heavy metals, and pharmaceuticals [8; 9; 10; 11; 12]. At the same time, these colloids can carry the adsorbed pollutants for long-distance transport, greatly enhancing the dispersion of pollutants in soil and water environments and increasing the ecological risk [13; 14; 15; 16]. It was reported that heavy metals in groundwater are strongly associated with small-sized colloidal matter and organic molecules [17; 18]. Moreover, as reported in the study, the colloids have the potential to promote the transport of heavy metals in soils and groundwater [19]. In recent years, the co-transport of colloids and contaminants has attracted widespread attention regarding environmental remediation due to its prevalence and efficient treatment in groundwater [20; 21; 22]. It was reported that colloids are well dispersed, which can provide highly potential adsorption material for heavy metal removal [23; 24]. Based on the conclusion of the soil column experiment [19; 25], it seems that colloids and heavy metals are discharged into the groundwater through the vadose zone. The presence of colloids may alter the propagation of heavy metals in contaminant plumes [26]. The effect of colloids on contaminant transport is dependent on hydrogeological conditions and physicochemical properties of the aquifers [27; 28; 29; 30]. Both groundwater chemistry and site-specific conditions may promote or hinder the co-transport of heavy metals and natural colloids in the subsurface environment [20; 28; 29]. Clay colloid is one of the most significant colloidal carriers for many contaminants in the subsurface environment [11; 31]. The facilitated transport of some heavy metal ions in porous media by clay colloid particles has been widely reported [32]. However, few studies have investigated the adsorption and transport of Ni\({}^{2+}\) with natural colloids in soil and groundwater. The high toxicity of Ni\({}^{2+}\) can result in serious ecological damage and cause disorders and diseases in humans due to long-term exposure.