Physico-Chemical Influence of Surface Water Contaminated by Acid Mine Drainage on the Populations of Diatoms in Dams (Iberian Pyrite Belt, SW Spain).

Maria José Rivera,José Miguel Dávila,Francisco Córdoba,Aguasanta Miguel Sarmiento,Ana Teresa Luís,José Antonio Grande,María Santisteban,Juan Carlos Fortes,Jesus Diaz-Curiel

doi:10.3390/ijerph16224516

Abstract

Twenty-three water dams located in the Iberian Pyrite Belt were studied during March 2012 (early spring) in order to carry out an environmental assessment based on diatom communities and to define the relationships between these biological communities and the physico-chemical characteristics of the dam surface water. This is the first time that a diatom inventory has been done for dams affected by acid mine drainage (AMD) in the Spanish part of the Iberian Pyrite Belt (IPB). It was found that the pH was the main factor influencing the behaviour of the diatom communities. Then, using a dbRDA approach it was possible to organize the aggrupation of diatoms into four groups in response to the physico-chemical conditions of the ecosystem, especially pH: (1) Maris, Aac, Gos, Cmora (pH 2–3); (2) Andc, San, And, Dpin (pH 3–4.5); (3) Gran, Pleon, Oliv, Lagu, Chan, SilI, SilII, Joya, Gar, Agrio, Camp, Corum (pH 4.5–6); (4) Herr, Diq I, Diq II (pH 6–7). The obtained results confirmed the response of benthic diatom communities to changes in the physico-chemical characteristics of surface water, and helped to understand the role of diatoms as indicators of the degree of AMD contamination in those 23 dams. Special attention was given to those that have an acidophilic or acid-tolerant profile (pH 2–3 and pH 3–4.5) such as Pinnularia aljustrelica, Pinnularia acidophila, Pinnularia acoricola and Eunotia exigua, which are the two groups found in the most AMD contaminated dams.

Highlights

The main problem with sulfide mining is the contamination of water resources caused by acid mine drainage (AMD) processes
The specific objectives of this work were (1) to describe benthic diatom communities, (2) to assess their relationship with water physico-chemistry specially the pH, and (3) to understand the effectiveness of diatoms as indicators of the degree of AMD contamination, several acidic Pinnularia species are highlighted as they are among the few organisms able to live in such extreme conditions
As a consequence of this wide pH range (AMD unaffected dams and AMD affected dams) there is a wide range of total dissolved solids (TDS), electrical conductivity (EC), SO4 2 and metals in dissolution, which is typical of AMD

Summary

Introduction

The main problem with sulfide mining is the contamination of water resources caused by acid mine drainage (AMD) processes. AMD occurs when sulfurous minerals are exposed to atmospheric [1], hydrological (oxygen, water) or biological weathering (chemoautotrophic bacteria) and they become oxidized, resulting in sulfuric acid (low pH), dissolved metal ions, elevated sulfate content [2], low alkalinity and high conductivity. The AMD process is widely described in the scientific literature because globally, it is one of the most serious and widespread contamination problems, affecting a large number of water resources in five continents (e.g., [3,4,5]). The problem becomes even more critical when these AMD polluted streams enter water dams, and reduce their use

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