Kianfar Bahareh, Tian Jingya, Rozemeijer Joachim, van der Zaan Bas, Bogaard Thom A, Foppen Jan Willem
Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, the Netherlands.
Department of Water Resources and Ecosystems, IHE-Delft Institute for Water Education, Delft, the Netherlands.
J Contam Hydrol. 2022 Apr;246:103954. doi: 10.1016/j.jconhyd.2022.103954. Epub 2022 Jan 17.
In recent years, DNA-tagged silica colloids have been used as an environmental tracer. A major advantage of this technique is that the DNA-coding provides an unlimited number of unique tracers without a background concentration. However, little is known about the effects of physio-chemical subsurface properties on the transport behavior of DNA-tagged silica tracers. We are the first to explore the deposition kinetics of this new DNA-tagged silica tracer for different pore water chemistries, flow rates, and sand grain size distributions in a series of saturated sand column experiments in order to predict environmental conditions for which the DNA-tagged silica tracer can best be employed. Our results indicated that the transport of DNA-tagged silica tracer can be well described by first order kinetic attachment and detachment. Because of massive re-entrainment under transient chemistry conditions, we inferred that attachment was primarily in the secondary energy minimum. Based on calculated sticking efficiencies of the DNA-tagged silica tracer to the sand grains, we concluded that a large fraction of the DNA-tagged silica tracer colliding with the sand grain surface did also stick to that surface, when the ionic strength of the system was higher. The experimental results revealed the sensitivity of DNA-tagged silica tracer to both physical and chemical factors. This reduces its applicability as a conservative hydrological tracer for studying subsurface flow paths. Based on our experiments, the DNA-tagged silica tracer is best applicable for studying flow routes and travel times in coarse grained aquifers, with a relatively high flow rate. DNA-tagged silica tracers may also be applied for simulating the transport of engineered or biological colloidal pollution, such as microplastics and pathogens.
近年来，DNA标记的二氧化硅胶体已被用作环境示踪剂。该技术的一个主要优点是，DNA编码提供了无限数量的独特示踪剂，且无背景浓度。然而，关于物理化学地下特性对DNA标记的二氧化硅示踪剂运移行为的影响，人们了解甚少。我们首次在一系列饱和砂柱实验中，针对不同的孔隙水化学性质、流速和砂粒粒径分布，探索这种新型DNA标记的二氧化硅示踪剂的沉积动力学，以便预测能最佳应用DNA标记的二氧化硅示踪剂的环境条件。我们的结果表明，DNA标记的二氧化硅示踪剂的运移可用一级动力学吸附和解吸很好地描述。由于在瞬态化学条件下大量的再夹带现象，我们推断吸附主要发生在二级能量最小值处。基于计算出的DNA标记的二氧化硅示踪剂与砂粒的附着效率，我们得出结论，当系统的离子强度较高时，与砂粒表面碰撞的大部分DNA标记的二氧化硅示踪剂也会附着在该表面上。实验结果揭示了DNA标记的二氧化硅示踪剂对物理和化学因素的敏感性。这降低了它作为研究地下水流路径的保守水文示踪剂的适用性。基于我们的实验，DNA标记的二氧化硅示踪剂最适用于研究粗粒含水层中流速相对较高的水流路径和运移时间。DNA标记的二氧化硅示踪剂也可用于模拟工程或生物胶体污染的运移，如微塑料和病原体。
