Impact of acid mine drainages on surficial waters of an abandoned mining site.
Weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This paper aims to characterise surface waters affected by mining activities in the Sierra Minera of Cartagena-La Union (SE, Spain). Water samples were analysed for trace metals (Zn, Cd, Pb, Cu, As and Fe), major ions (Na(+), K(+), Ca(2+) and Mg(2+)) and anions (F(-), Cl(-), NO3 (-), CO3 (2-), SO4 (2-)) concentrations and were submitted to an "evaporation-precipitation" experiment that consisted in identifying the salts resulting from the evaporation of the water aliquots sampled onsite. Mineralogy of the salts was studied using X-ray diffraction and compared with the results of calculations using VISUAL MINTEQ. The study area is heavily polluted as a result of historical mining and processing activities that has produced large amount of wastes characterised by a high trace elements content, acidic pH and containing minerals resulting from the supergene alteration of the raw materials. The mineralogical study of the efflorescences obtained from waters shows that magnesium, zinc, iron and aluminium sulphates predominate in the acid mine drainage precipitates. Minerals of the hexahydrite group have been quantified together with minerals of the rozenite group, alunogen and other phases such as coquimbite and copiapite. Calcium sulphates correspond exclusively to gypsum. In a semiarid climate, such as that of the study area, these minerals contribute to understand the response of the system to episodic rainfall events. MINTEQ model could be used for the analysis of waters affected by mining activities but simulation of evaporation gives more realistic results considering that MINTEQ does not consider soluble hydrated salts.
Department of Petrology and Geochemistry, Faculty of Geology, University Complutense of Madrid, Jose Antonio Novais 2, 28040, Madrid, Spain. mglorenzo@geo.ucm.es.
M L
ML
García-Lorenzo
Department of Agricultural Chemistry, Geology and Pedology, Faculty of Chemistry, University of Murcia, Campus de Espinardo, 30100, Murcia, Spain.
J
J
Marimón
Department of Agricultural Chemistry, Geology and Pedology, Faculty of Chemistry, University of Murcia, Campus de Espinardo, 30100, Murcia, Spain.
M C
MC
Navarro-Hervás
Department of Agricultural Chemistry, Geology and Pedology, Faculty of Chemistry, University of Murcia, Campus de Espinardo, 30100, Murcia, Spain.
C
C
Pérez-Sirvent
Department of Agricultural Chemistry, Geology and Pedology, Faculty of Chemistry, University of Murcia, Campus de Espinardo, 30100, Murcia, Spain.
M J
MJ
Martínez-Sánchez
Department of Physical Geography, Human Geography and Regional Geographical Analysis, Faculty of Geography, University of Murcia, Murcia, Spain.
José
J
Molina-Ruiz
D004777:Environment; D004784:Environmental Monitoring; D007501:Iron / Q000032:analysis; D008903:Minerals / Q000032:analysis; D008906:Mining; D012492:Salts / Q000032:analysis; D013030:Spain; D013431:Sulfates / Q000032:analysis; D013440:Sulfides / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014961:X-Ray Diffraction
D008903:Minerals; D012492:Salts; D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D007501:Iron
Acid mine drainage; Environmental minerals; Mining activity; Sulphate efflorescences; Trace elements; X-ray diffraction