Liu Geng, Guo Linxi, Wang Chaozi, Liu Jiarong, Hu Zengjie, Dahlke Helen E, Xie En, Zhao Xiao, Huang Guanhua, Niu Jun, Fa Keyu, Zhang Chenglong, Huo Zailin
College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China.
College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China.
Sci Total Environ. 2023 Dec 20;905:167378. doi: 10.1016/j.scitotenv.2023.167378. Epub 2023 Sep 25.
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 (R = 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.
最近的研究表明，游离DNA示踪剂在追踪水流以及污染物在包气带中的运移方面具有潜力。然而，游离DNA示踪剂能否用于洪水灌溉区来追踪水流以及溶质/污染物的运移仍不明确。为了揭示在洪水灌溉条件下，表面施用的游离DNA示踪剂在土壤中的入渗过程和滞留机制，我们通过模拟洪水灌溉，在10厘米水头下测试了表面施用的游离DNA示踪剂在饱和砂土柱中的归宿和运移行为。根据实验突破曲线并拟合双位点动力学吸附模型（R = 0.83 - 0.91，NSE = 0.79 - 0.89），可以获得吸附/解吸速率并模拟示踪剂的滞留曲线。这些结果共同表明：1）游离DNA主要吸附在土壤中的粘土颗粒上，粘土颗粒体积占比为1.96%，但表面积占比>97.5%，并紧密覆盖砂粒表面；2）在孔隙水pH值为8.0时，除了4.9%通过和3.1%降解量外，实验土壤中的主要滞留机制是配体交换（42.0%）、范德华相互作用（主要是氢键）、静电力和过滤（共44.7%）以及阳离子桥（5.3%）。据我们所知，本研究首次量化了游离合成DNA示踪剂通过土壤时各主要滞留机制的贡献。我们的研究结果有助于游离DNA示踪剂在洪水灌溉和其他入渗条件下追踪包气带水流以及溶质/污染物运移方面的应用。
