Retention and remobilization mechanisms of environmentally aged silver nanoparticles in an artificial riverbank filtration system.
Retention and remobilization mechanisms of environmentally aged silver nanoparticles in an artificial riverbank filtration system.
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DOI：
10.1016/j.scitotenv.2018.07.079
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发表时间：
2018-12
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通讯作者：
L. Degenkolb;G. Metreveli;A. Philippe;Anja Brandt;K. Leopold;Lisa Zehlike;H. Vogel;G. Schaumann;T. Baumann;M. Kaupenjohann;F. Lang;S. Kumahor;S. Klitzke
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作者：
L. Degenkolb;G. Metreveli;A. Philippe;Anja Brandt;K. Leopold;Lisa Zehlike;H. Vogel;G. Schaumann;T. Baumann;M. Kaupenjohann;F. Lang;S. Kumahor;S. Klitzke
河岸过滤系统是确保渗透地表水清洁用于饮用水生产的重要结构。在我们的研究中，我们调查了环境老化的银纳米粒子（Ag NP）通过这些系统突破的潜在风险。此外，我们确定了导致银NP在表层沉积物层中积累的再活化的因素，以深入了解再活化mechanism.We进行了柱实验与银NP在室外中试植物组成的水饱和的沉积物柱模仿河岸过滤系统。NP之前已经分别在河水、土壤提取物和超纯水中老化。我们研究了NP的深度依赖性穿透和保留。在随后的批处理实验中，我们研究了负责银NP保留在沉积物的上10厘米，诱导离子强度降低，天然有机物（NOM），和机械力的再动员的过程。我们通过ICP-MS测定了再活化的Ag的量，并使用GFAAS在再活化后区分颗粒状和离子状Ag。含银的杂聚集体的存在下进行了研究，通过结合过滤与单粒子ICP-MS。单一和不稳定的Ag突破事件主要发现在30 cm的深度和Ag NP积累在上20 cm的列。土壤老化的Ag NP表现出最低的保留率，仅为54%。再动员是由离子强度的降低和NOM的存在结合机械力诱导的。老化介质和再动员介质中钙的存在降低了再动员潜力。银纳米粒子在河岸渗滤系统中的穿透能力一般较低，但在土壤中的老化增加了其迁移能力。再动员过程与天然胶体的共动员有关。
Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms.We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS.Single and erratic Ag breakthrough events were mainly found in 30 cm depth and Ag NP were accumulated in the upper 20 cm of the columns. Soil-aged Ag NP showed the lowest retention of only 54%. Remobilization was induced by the reduction of ionic strength and the presence of NOM in combination with mechanical forces. The presence of calcium in the aging- as well as the remobilizing media reduced the remobilization potential. Silver NP were mainly remobilized as heteroaggregates with natural colloids, while dissolution played a minor role.Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.