Hydrogeochemistry and distribution of potentially toxic elements in a metallogenic province – The Iberian Pyrite Belt, Portugal

Patricia Gomes,Filipa Moreno,Orquídea Neves,Rita Fonseca,Ana Costa,Teresa Valente,Maria Rosário Costa,Maria Rosário Costa

doi:10.1051/e3sconf/20199801016

Abstract

Contamination by acid drainage is an environmental problem in mineralized regions, especially in the surroundings of sulphide mines. The water rock interaction process involves the oxidative dissolution of sulphides, naturally or by mining activity, that generates acidity which, in turn, produces sulfate, and water pollution by sulphide-hosted metals. The particular geology of the Iberian Pyrite Belt (IPB) in the southwestern Iberian Peninsula creates the ideal conditions for such water contamination. Different water types were sampled at 28 locations across the entire IBP metallogenetic province. Anions, metals, and arsenic were analysed to assess the influence of acid drainage. The results demonstrate the sulfate nature of waters in the vicinity of mines. Other types of water in the IPB region are mainly mixed chloride and bicarbonate (river and groundwater) and mixed and sodium-bicarbonate (lakes) types. Water quality assessment indicated strong contamination of surface waters that are directly influenced by mine wastes. There is the additional concern that some lakes and groundwaters exhibit concentrations of potentially toxic elements (e.g. Al, As) that are above the regulatory limits established by the European Commission Water Framework Directive.

Highlights

In areas of water scarcity, such as across the Mediterranean region, protection of water resources is a major management concern
acid mine drainage (AMD) caused by historic mining, as well as acid rock drainage (ARD) associated with natural oxidation of sulphides, has resulted in unique manifestations of water contamination [e.g., 4]
This study focused on understanding the chemical character of waters sources in a mineralized region with long tradition of metal exploitation that has both closed and active mines

Summary

Introduction

In areas of water scarcity, such as across the Mediterranean region, protection of water resources is a major management concern. Certain anthropogenic activities, like mining exploitation, is characterized by its potential for water contamination by toxic elements (e.g. metals and arsenic) through the production of acid mine drainage (AMD). This phenomenon occurs by oxidative dissolution of sulphide minerals that generates acidity which, in turn, produces sulfate, and water pollution by sulphide-hosted metals. These elements can be carcinogenic and, pose a threat to human health. AMD caused by historic mining, as well as ARD associated with natural oxidation of sulphides, has resulted in unique manifestations of water contamination [e.g., 4]

Methods

Results

Conclusion