## 1 Introduction
### The Abbadia San Salvatore Mining Area  
The ASS mining area is located on the eastern flank of the 200-300 ky old volcanic silicic complex of Mt. Amiata. The composition of the volcanic products is trachytic to olivine latitic and mostly consisting of lava flows and domes [19, 20, 21, 22]. According to ([23] and reference therein), the 65 ha wide ASS mining area was divided into 7 different sectors (Figure 1), each one being characterized by different criticalities in terms of Hg concentration. While sectors 0 and 1 represent areas where Hg was found at low concentrations, sectors 2 and 3 host buildings of miners and management executives, the grounding area of the mining material, the conveyors and the Garibaldi well and old furnaces, dryers, and condensers, respectively. Sector 4, namely \"Le Lame\", is the site where most mining wastes were accumulated. Sector 5 includes the armory and the house of the guardians. Eventually, Sector 6 became the most Hg-contaminated area, since this portion hosted the edifices of the Gould and Nesa furnaces, the new driers and condensers, and the main mining material storage area. Between 1897 and 1909, the two largest Hg-deposits from the Mt. Amiata district were discovered at Abbadia San Salvatore. In [25] reported that the exploited ore had a content between 0.6 and 2.0 wt% of Hg and was exploited up to the depth of 400 m [26]. Liquid mercury was obtained from retort or rotary furnaces (e.g., Spirek, Cermak-Spirek and Gould furnaces). The cinnabar, inside the furnaces, reacted with O\({}_{2}\) up to the temperature of 600-700 \({}^{\circ}\)C to produce sulfur dioxide and elemental gaseous mercury, according to the following reaction (1):  
\[\text{HgS}+\text{O}_{2}=\text{Hg}^{0}+\text{SO}_{2} \tag{1}\]  
Sulfur dioxide was removed by water washing, whereas mercury vapors were then condensed by cooling systems to obtain liquid mercury and sold to the international market. The post-roasting products and unprocessed materials were stored in the adjacent building hosting the Spirek and Cermak-Spirek furnaces, which were later destroyed and replaced by the most efficient Gould furnaces. The stored waste material was mainly derived by the ASS area, although tailings from nearby Hg-exploitation sites of Mt. Amiata (e.g., Siele, Bagnore and Morone), whose ganga composition was different from that of Abbadia San Salvatore ([27], and reference therein), were also accumulated. From mid-1950, the mining waste of ASS was stored in silos and then transferred to Le Lame mining dump, which is located in the northern part of the mine concession (Section 4, Figure 1). The Study Area  
The Le Lame mining landfill (Figure 2) is situated on the eastern flank of Mt. Amiata a few kms north of the Abbadia San Salvatore mine and has an extension of about 120,000 m\({}^{2}\)[28]. The transfer of the post-processing products (calcines) (locally named \"_rosticci_\"), to the mining dump began in the 1950s when, to reach higher production of liquid mercury, new automated and conveyor belt systems to transfer the Hg-rich material  
Figure 1: Location of the Hg-mining district of Abbadia San Salvatore (Central Italy) and the seven sectors into which the mining are was divided according to the different reclamation activities (modified from [24]). Scale 1:15,000.  
from the extraction well to the Gould Furnaces were established [29]. To the best of our knowledge, no documentation is available on how the material deriving from the roasting plants was distributed at Le Lame. This implies that the waste material deriving from the Abbadia San Salvatore and other Mt. Amiata mining sites cannot be located. Additionally, the slopes of Le Lame were modified in time to avoid slumping or landslide processes. It then became difficult to define the thickness and calculate the volume occupied by the post-roasting products.