Proposal of precipitation–dissolution models in a channel affected by acid mine drainage in the Iberian Pyrite Belt during torrential rain regimes

Abstract

Two sampling points were defined in the Meca River, which receives leachates from the tailings of the Tharsis Mining Complex in the Iberian Pyrite Belt, SW Spain: ‘MECA A’, which is located at the base of the tailings, and ‘MECA B’, located downstream at a distance of 14,165 m. 24 h of sampling was scheduled for a date in which precipitation intensity would be very high, so observations of the system were undertaken under high flow conditions. The study of the physico-chemical parameters obtained from the analysis of the samples, combined with rainfall data, enabled us to characterise the processes which govern the precipitation–dissolution phenomena along the analysed river, by applying graphic statistical tools, such as the autocorrelation functions, cross-correlation functions and spatial evolution, as well as geochemical modelling tools. The compositional differences between both points are fundamentally due to two phenomena: the first is a consequence of the proximity to the pollutant source, where the waters have not yet evolved, while the second is due to the development of hydrolysis processes in areas further away from the source focus.