Abstract：
It has been recently demonstrated that free DNA tracers have the potential in tracing water flow and contaminant transport through the vadose zone. However, whether the free DNA tracer can be used in flood irrigation area to track water flow and solute/contaminant transport is still unclear. To reveal the infiltration process and retention mechanisms of surface applied free DNA tracer through soil under flood irrigation, we tested the fate and transport behavior of surface applied free DNA tracers through packed saturated sandy soil columns with a 10 cm water head mimicking flood irrigation. From the experimental breakthrough curves and by fitting a two-site kinetic sorption model (R2 = 0.83-0.91 and NSE = 0.79-0.89), adsorption/desorption rates could be obtained and tracer retention profiles could be simulated. Together these results revealed that 1) the adsorption of free DNA was dominantly to clay particles in the soil, which took up 1.96 % by volume, but took up >97.5 % by surface area and densely cover the surface of sand particles; and 2) at a pore water pH of 8.0, excluding the 4.9 % passing through and 3.1 % degradation amount, the main retention mechanisms in the experimental soil were ligand exchange (42.0 %), Van der Waals interactions (mainly hydrogen bonds), electrostatic forces and straining (together 44.7 %), and cation bridge (5.3 %). To our knowledge, this study is the first to quantify the contribution of each of the main retention mechanisms of free synthetic DNA tracers passing through soil. Our findings could facilitate the application of free DNA tracer to trace vadose zone water flow and solute/contaminant transport under flood irrigation and other infiltration conditions.
摘要：
最近已经证明，游离的DNA示踪剂具有追踪水流和污染物通过渗流带的潜力。然而,目前尚不清楚游离DNA示踪剂是否可用于漫灌区的水流和溶质/污染物的运输。为了揭示漫灌条件下表面施用游离DNA示踪剂在土壤中的渗透过程和保留机制，我们通过填充的饱和沙质土壤柱测试了表面施用的游离DNA示踪剂的命运和运输行为，水头为10厘米，模仿洪水灌溉。从实验穿透曲线和通过拟合两位点动力学吸附模型（R2=0.83-0.91和NSE=0.79-0.89），可以获得吸附/解吸速率，并可以模拟示踪剂保留曲线。这些结果表明，1）游离DNA的吸附主要集中在土壤中的粘土颗粒上，按销量计算占1.96%，但占表面积>97.5%，并密集覆盖砂粒表面；2)孔隙水pH值为8.0时，不包括4.9%的通过量和3.1%的降解量，在实验土壤中的主要保留机制是配体交换(42.0%)，范德华相互作用（主要是氢键），静电力和应变（合计44.7%），和阳离子桥(5.3%)。据我们所知,这项研究是第一个量化自由合成DNA示踪剂穿过土壤的每个主要保留机制的贡献。我们的发现可以促进游离DNA示踪剂在洪水灌溉和其他渗透条件下追踪渗流区的水流和溶质/污染物的运输。
