MAPPING HEAVY METALS CONCENTRATION IN THE SIERRA DE CARTAGENA (SOUTH EASTH SPAIN) USING FOSS GIS
Mining activity in the Sierra de Cartagena (SE Spain) started more than 2500 years ago, reaching its maximum activity in 1840. Galena, sphalerite and pyrite are the main minerals extracted. Today most of the area is covered by accumulations of sterile materials in mining wastes creating a distinctive landscape.
The area is characterized by a semiarid climate with intense storms during the autumn and strong wind events due to the proximity to the sea. Several small watersheds with step slopes are surrounding the mining wastes, facilitating the erosion and transport of sediments to the sea located nearby. With these conditions, the sterile materials are mobilized by wind and runoff, producing high concentrations of heavy metals (zinc, lead, iron) and sulphur in the soils of the surrounding areas.
In this work several interpolation methods have been used to generate concentration maps (splines, universal krigging, regresion-krigging) using cross-validation to check the accuracy of the different methods. One important hypothesis to be tested in the process is if there are significant differences between samples taken in the channel and out of the channel due to differences in the relative importance of wind and run-off in the dissemination of heavy metals.
The data collection followed a random sampling of 22 samples in channels and 52 out of the channel, measuring concentrations of heavy metals and other elements. Another sampling, longitudinal to the main channel in the area, has been used to set the changes in concentration in the different sectors of the channel profile.
The software used is GRASS, SAGA and R (using package gstat for geostatistical analysis on a GNU-Linux environment); data bases are stored in a PostgreSQL DBMS. Several scripts with R have been developed to integrate the software used.
Francisco Alonso Sarría - Universidad de Murcia
Jesús Moreno Brotóns - Universidad de Murcia
Francisco Belmonte Serrato - Universidad de Murcia