Modelling of Mercury Fate and Transport in Soil Systems

A conceptual model was developed for mercury fate and transport in the vadose zone. This model was numerically implemented in the coupled reactive transport simulator HP1 for variable-saturated flow conditions. A sensitivity analysis was done using the method of Morris elementary effects to identify the most critical parameters and processes for different contamination sources and different indicators. Processes and parameters identified as critical based on the sensitivity analysis differed from one scenario to the other depending on pollution type (cinnabar, NAPL or aqueous Hg), on the indicator assessed (leached Hg, Hg in soil horizon originally polluted…) and on time. However, in general concentration of DOM in soil and rainwater is the most critical parameter. Other important parameters are those related to Hg sorption on SOM (thiols, and humic and fulvic acids), and to Hg complexation with DOM. Initial Hg concentration is also often identified as a sensitive parameter. Interactions between factors and non linear effects as measured by the elementary effect method are generally important, but again depend on the type of contamination and on time.