Spatial variation of biological and pedological properties in an area affected by a metallurgical mercury plant: Almadenejos (Spain)

Almadén, Spain, has the most important known cinnabar deposits, which have provided a third of the entire world production of Hg, and has been the scene for numerous studies on Hg. This mining district includes several mines where cinnabar has been extracted in the past two millennia as well as facilities related to the production of primary Hg. The aim of the work is to evaluate the spatial distribution of Hg in the soil-plant system within an area where intense activity occurred over a long period. An abandoned metallurgical plant from the 17th-18th centuries was chosen as the study area, situated in Almadenejos a distance of 12 km from Almadén. Nowadays, this plot is covered with cinnabar mine tailings and it is used by village inhabitants for livestock grazing. The area has elevated Hg concentrations of natural origin and from human activities. Soil parameters are similar within the study area; however, data reveal high variability in total and available Hg concentrations in soils, making it difficult to establish a trend. Marrubium vulgare L. has been studied due to its abundance in the plot, and there is no evidence of phenological toxicity. In spite of elevated Hg concentrations, high biological activity is found in the sampled soils. All these characteristics, spatial variation, high Hg concentration, good biological activity, make this a particularly good area for studies involving Hg.