Increasing background salinity in watersheds has largely been attributed to road salt retention in groundwaters due to their long residence times. However, laboratory studies demonstrate that soils temporarily store salts, either in porewater or adsorbed onto particles. Field studies of road salt retention in soils are nevertheless rare, and mechanisms of salt transport across multiple hydrological reservoirs (e.g., from soil to groundwater) are unknown. Thus, we collected roadside soil porewater and karst spring water weekly for ~1.5 yr to determine salt transport through the vadose zone into the phreatic zone. We observed dual retention mechanisms of sodium (Na⁺) and chloride (Cl⁻) in soils due to slow porewater movement, causing ion movement through the soil as slow as 1.3 cm/day, and cation exchange processes, leading to initial Na⁺ retention followed by later release months after application. Cation exchange processes also caused base cation loss from exchange sites into mobile porewater. Rapid Na⁺ and Cl⁻ delivery to groundwater occurred through karst conduits during the winter. However, elevated background levels of salt ions in groundwater during the non-salting months indicated accumulation in the catchment due to slower porewater flow in the soil and rock matrix and delayed Na⁺ release from soil exchange sites.

流域的背景盐度增加主要归因于其滞留时间长，从而使地下水中的道路盐分滞留。但是，实验室研究表明，土壤可以暂时将盐存储在孔隙水中或吸附到颗粒上。然而，对道路中土壤中的盐分保留的田间研究很少，并且盐分跨多个水文水库（例如，从土壤到地下水）的运输机制尚不清楚。因此，我们每周收集路边的土壤孔隙水和岩溶泉水约1.5年，以确定盐通过渗流带进入潜水区的过程。我们观察到钠（Na的双重保留机制⁺）和氯化物（氯^-）在土壤中由于缓慢的孔隙水运动，导致离子以低至1.3 cm / day的速度在土壤中运动，以及阳离子交换过程，导致最初的Na ⁺保留并在施用后数月释放。阳离子交换过程还引起了阳离子阳离子从交换位点流失到流动的孔隙水中。快速的Na ⁺和Cl ^-交付给地下水在冬季通过岩溶管道发生。然而，由于盐分在土壤和岩石基质中的流动较慢，以及Na ⁺从土壤交换位点的释放延迟，非盐析月份地下水中盐离子的本底水平升高表明集水区有堆积。