Analysing some sandy mine tailings transported by a creek (rambla) towards Mediterranean sea near Cartagena, SE Spain

Resumen

Although mining activity ceased in 1991, huge piles of mining wastes can be found in Cartagena-La Union Mountains, SE Spain. Erosion and transport of waste materials throughout the no permanent creeks called “rambla” in this region are associated to strong storms that occur during fall season under Mediterranean climate. The objective was to determine the effect of water transport on mining wastes along the watercourse in order to evaluate the mineral species changes that the different original sulphides have undergone, regarding qualitative, quantitative, and environmental aspects. In order to study weathering of minerals and the heavy metals release to water and soil were used techniques such as SEM-EDX analysis, and XRF. The transport along the studied riverbed seems not to have a big influence on the weathering status, but only on the different frequencies of sulphides and heavy sulphates in relation to their specific gravity. Besides, the oxidation level of the sulphide grains seems not to be very high because of the important presence of clayey materials in these mining wastes what could be packing up the sulphide crystals so partly protecting them against the aggressive factors. Mineralogical as well as chemical analyses show that a strong enrichment of heavy metal sulphides is forming nearby the riverbed mouth. This constitutes a noteworthy environmental hazard due to occurrence of several toxic elements such as Pb, Zn, and As.