EA 4592 G&E, Bordeaux INP - Université Bordeaux Montaigne - Carnot ISIFoR, 1 allée F. Daguin, 33607 Pessac, France.
EA 4592 G&E, Bordeaux INP - Université Bordeaux Montaigne - Carnot ISIFoR, 1 allée F. Daguin, 33607 Pessac, France.
Sci Total Environ. 2021 Oct 15;791:148210. doi: 10.1016/j.scitotenv.2021.148210. Epub 2021 Jun 5.
Soils and groundwater are often contaminated by complex organic mixtures also called Non Aqueous Phase Liquids (NAPLs). Several techniques such as drilling, monitoring of soil gas or injection of tracers are traditionally used to quantify NAPLs in aquifers but are complex to perform. The use of natural soil gas such as Rn could be an easy and cheap alternative. This method requires the knowledge of the radon NAPL-water partitioning coefficients (K.). Once spilled on soil, NAPL will undergo degradation (evaporation, effects of sun light among others) and this degradation could impact the K. This study aims at investigating the partitioning coefficients of complex NAPLs such as commercial diesel fuel and gasoline in relation to degradation such as evaporation and UV-degradation. For that purpose, batch experiments and GCMS investigations were carried out. The results show different K for the commercial diesel fuel (60.7 ± 6.1) and gasoline (37.4 ± 5.6). The results also show different K behaviors in relation with degradation. Degraded diesel fuel display opposite K values (74.8 ± 7.5 and 25.1 ± 2.5 for UV degraded and evaporated diesel fuel, respectively), compared to fresh one. Degraded gasoline shows no significant variations of the K compared to fresh one. The molecular investigation reveals the removal of the most volatile fraction for the evaporation treatment, whereas UV-degradation do not have pronounced effects on the chromatogram pattern. For the gasoline molecular investigation, no difference is observed between the treatments excepted a very slight removal of the lightest compounds under evaporation. These results show that NAPL degradation have effects on the K for diesel fuel and no significant effects for gasoline, at least with these degradation paths. This K variation will have in fine effects on Rn activity interpretation and NAPL subsurface quantification.
土壤和地下水经常受到称为非水相液体（NAPL）的复杂有机混合物的污染。传统上，通常使用钻探、土壤气体监测或示踪剂注入等技术来量化含水层中的 NAPL，但这些技术执行起来比较复杂。使用天然土壤气体（如氡）可能是一种简单且廉价的替代方法。该方法需要了解氡 NAPL-水分配系数（K）。一旦 NAPL 溅到土壤上，它将经历降解（蒸发、阳光等的影响），这种降解可能会影响 K 值。本研究旨在调查复杂 NAPL（如商用柴油燃料和汽油）与降解（如蒸发和 UV 降解）相关的分配系数。为此，进行了批量实验和 GCMS 研究。结果表明，商用柴油燃料（60.7±6.1）和汽油（37.4±5.6）的 K 值不同。结果还表明，K 值与降解有关的行为也不同。与新鲜的相比，降解的柴油燃料显示出相反的 K 值（UV 降解和蒸发的柴油燃料分别为 74.8±7.5 和 25.1±2.5）。与新鲜的相比，降解的汽油显示出 K 值没有明显变化。分子研究表明，蒸发处理会去除最易挥发的部分，而 UV 降解对色谱图模式没有明显影响。对于汽油的分子研究，除了蒸发处理会轻微去除最轻的化合物外，处理之间没有观察到差异。这些结果表明，NAPL 降解会影响柴油燃料的 K 值，但对汽油的影响不大，至少在这些降解途径下是这样。这种 K 值的变化最终会对氡活度解释和 NAPL 地下定量产生影响。
