4D dispersion of total gaseous mercury derived from a mining source: Identification of criteria to assess risks related to high concentrations of atmospheric mercury

Abstract

Mercury (Hg) is a global pollutant that can be transported long distances after its emission from primary sources. The most common problem of gaseous Hg in the vicinity of anthropogenic sources is its presence in inorganic forms and in the gaseous state in the atmosphere. Risk assessments related to the presence of gaseous Hg in the atmosphere at contaminated sites are often based on episodic and incomplete data, which do not properly characterize the Hg cycle in the area of interest or consider spatial or temporal terms. The aim of this work was to identify criteria to obtain the minimum amount of data with the maximum meaning and representativeness in order to delimit risk areas, both in a spatial and temporal respect. Data were acquired from May 2014 to August 2015 and included vertical and horizontal Hg measurements. A statistical analysis was carried out, and this included the construction of a model of vertical Hg movements that could be used to predict the location and timing of Hg inhalation risk. A monitoring strategy was designed in order to identify the relevant criteria, and this involved the measurement of gaseous Hg in a vertical section at low altitude (i.e. where humans are present) and in horizontal transects to appropriately characterize the transport cycle of gaseous Hg in the lower layers of the atmosphere. The measurements were carried out over time in order to obtain information on daily and seasonal variability. The study site selected was Almadenejos (Ciudad Real, Spain), a village polluted with mercury related to decommissioned mining and metallurgical facilities belonging to the Almaden mercury mining district.