## 1 Introduction  
Concerns about mercury as an industrial pollutant have led to increased interest in the detection and regulation of mercury in the environment.  
The most widely noted Hg reaction in soils is the reduction of Hg\({}^{2+}\) to Hg\({}^{0}\)[1], which is the first step in the volatilization of mercury to the atmosphere. Although the volatilization of Hg\({}^{0}\) from soils has been studied extensively, it still represents a primary source of uncertainty in the global/regional annual budget of nonpoint source mercury transport [1, 2].  
Once released into the air, mercury (Hg\({}^{0}\)) can be transported to remote areas by atmospheric cycles due to its long residence time in the atmosphere [3, 4]. Both natural and anthropic processes can emit a considerable amount of gaseous Hg to the atmosphere [3]. It has been estimated that from the time of the Industrial Revolution, the average Hg concentration in the troposphere has been elevated by a factor of three [5], and a recent publication estimated that the anthropogenic gaseous Hg emissions were 2190 in 2000 [6, 7].  
In recent decades, considerable progress has been made regarding the understanding of Hg emission from Hg-enriched areas [8; 9; 10]. The results of these studies have demonstrated that Hg emission rates from Hg-enriched areas are higher than background areas [11] and that the contribution of gaseous Hg into the atmosphere from Hg-enriched soil in the mercuriferous belt has largely been underestimated [8; 10].  
Soils from decommissioned mercury mine sites usually exhibit high concentrations of mercury as a consequence of inefficient mining operations and the usually null restoration actions undertaken [12]. The Principality of Asturias in the north of Spain is a region with mercury mines dating back to the Roman era [13]. The largest Asturian mercury deposits exploited in the past were the La Soterrana (Lena) and El Terronal (Mieres) mines. These mercury mines were part of a substantial and thriving industry in the 19 th and 20 th centuries. Although mining ceased in 1974, the geochemical dispersion of mercury from abandoned spoil heaps throughout the area continues to be of concern [14; 15; 16].  
Previous studies on these mines [17] showed a high concentration of gaseous mercury near polluted soil, reaching these last concentrations up to 2-4 orders of magnitude the national background value. Nevertheless, at present, no studies regarding Hg diffusion from waste produced by the demolition of the metallurgical plant have yet been carried out.  
The objective of this work is to study the behavior of mercury in the atmosphere in the decommissioned mining area of La Soterrana in Asturias (Spain). More concretely, the study is focused on the behavior of gaseous mercury emitted from contaminated rubble or debris present in the area as a result of the demolition of a metallurgical facility. The study was carried out in the framework of the SUBproducts4 LIFE project, a research project co-funded by the European Union as part of the LIFE program. The project SUBproducts4 LIFE aims to employ the concept of a circular economy by repurposing industrial waste (coal ash and gypsum from coal power plants and blast furnace slag and steelmaking slag from steel factories) for the large-scale remediation of contaminated soils and brownfield areas associated with Hg mining [17]. The study was carried out in two steps. First, the mercury concentration in the air was monitored in the central contaminated area and in the surroundings, up to 150 m from the central focus. This allowed for the development of an empirical model described in a previous study, [18]. Secondly, a new chemical-physical model was developed and validated by means of the results measured in situ to explain the emission and diffusion of Hg over a short-distance.