Spatio-temporal geostatistical modelling of sulphate concentration in the area of the Reocín Mine (Spain) as an indicator of water quality.

Water stored in open-pit lakes can be a water resource when the mine is closed. This study aimed to develop a reliable model to evaluate the water quality, based on the sulphate concentration, in the Reocín Mine area (Spain) by using geostatistical algorithms. To this end, water samples were taken from the beginning of the flooding period in November 2004 until August 2020. The model showed that the sulphate concentration was highest between February 2009 and February 2012 and decreased as the flooding process progressed. The area with the highest concentration (2000 mg L-1) was the central part of the study area, where the mine is located, while in the northeast and southwest, the values from the beginning of the flooding period were lower, below 500 mg L-1. In the last obtained model, the values decreased considerably to 1300 mg L-1 in the central area and below 250 mg L-1 in the northeast and southwest areas. The modelling conducted to assess the water quality in the area of influence of the mine determined that the flooding process has little influence on the water in the rivers and streams in the area, since the sulphate concentration measured in the adjacent rivers and streams was less than 250 mg L-1, indicating that anomalous concentrations were only found in the open-pit area. It was shown that geostatistical algorithms are useful tools that can be used to model the intensity and extension of water pollutants in space over time.

Hydrochemical evolution of the Reocín mine filling water (Spain).

The Reocín mine is located in Cantabrian region, in northern Spain. Its exploitation ended in 2003 due to the exhaustion of its reserves. In November 2004, the controlled flooding of the openpit began. During this process, both the qualities of stored water and piezometric levels have been monitored to control the possible water detraction from the Saja-Besaya hydrographic system. This paper deals with the water chemistry analysis of the pit lake surface, as well as the different conditions of the area. Geological and hydrogeological contexts play an important role in the lake water chemistry. The lake water quality continues improving. The sulphate content and zinc concentrations are already below the permitted pouring limits. Three factors are distinguished: the washing of the mine shafts is completed; the water supply from the aquifer contributes to the dissolution of the salt content and the bedrock, and dolomite, which neutralizes acid waters and improves the water quality during the flooding process with a pH value of 8. Owing to these conditions, the stored water meets the necessary conditions for discharge and provides the opportunities to use it.