Identifying Sources and Assessing Potential Risk of Exposure to Heavy Metals and Hazardous Materials in Mining Areas: The Case Study of Panasqueira Mine (Central Portugal) as an Example

Carla Candeias,João Teixeira,Eduardo Da Silva,Paula Ávila

doi:10.3390/geosciences4040240

Abstract

The Sn-W Panasqueira mine, in activity since the mid-1890s, is one of the most important economic deposits in the world. Arsenopyrite is the main mineral present as well as rejected waste sulphide. The long history is testified by the presence of a huge amount of tailings, which release considerable quantities of heavy metal(loid)s into the environment. This work assesses soil contamination and evaluates the ecological and human health risks due to exposure to hazardous materials. The metal assemblage identified in soil (Ag-As-Bi-Cd-Cu-W-Zn; potentially toxic elements (PTEs)) reflects the influence of the tailings, due to several agents including aerial dispersion. PTEs and pH display a positive correlation confirming that heavy metal mobility is directly related to pH and, therefore, affects their availability. The estimated contamination factor classified 92.6% of soil samples as moderately to ultra-highly polluted. The spatial distribution of the potential ecological risk index classified the topsoil as being of a very high ecological risk, consistent with wind direction. Non-carcinogenic hazard of topsoil, for children (1–6 years), showed that for As the non-carcinogenic hazard represents a high health risk. The carcinogenic risks, both for children and adult alike, reveal a very high cancer risk mostly due to As ingestion.

Highlights

Mine tailings, with considerable amounts of sulfides, left in the vicinity of environmentally sensitive locations, constitute one of the greatest threats to the surrounding environment
With considerable amounts of sulfides, left in the vicinity of environmentally sensitive locations, constitute one of the greatest threats to the surrounding environment. These materials when exposed to air and water are oxidized through chemical, electrochemical, and biological reactions, forming ferric hydroxides and sulfuric acid, leading to the generation of acid mine drainage with high contents of metals and sulfates, related to the alteration of sulfides, the equilibrium of which depends on their solubility [1,2,3,4,5]
The Panasqueira deposit is a classic example of postmagmatic hydrothermal ore deposit, which is associated with Hercynian plutonism [36,41]

Summary

Introduction

With considerable amounts of sulfides, left in the vicinity of environmentally sensitive locations, constitute one of the greatest threats to the surrounding environment These materials when exposed to air and water are oxidized through chemical, electrochemical, and biological reactions, forming ferric hydroxides and sulfuric acid, leading to the generation of acid mine drainage with high contents of metals and sulfates, related to the alteration of sulfides, the equilibrium of which depends on their solubility [1,2,3,4,5]. Wind-blown dust originating from polluted soil is responsible for the aerial dispersion of trace metals [7] Exposure to these hazardous elements may have different pathways, e.g., through the direct ingestion of soils and dust, ingestion of vegetables grown on contaminated soil or dust adhering to plants or dust inhalation. According to several authors [9,10,11,12,13,14]

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