Acid Rock Drainage
During the Quaternary/Neogene period, the sulfide ore bodies in the IPB began to oxidize in the present of air and water. The oxidation releases acidic compounds such as sulfates, heavy metals and metalloids into the Río Tinto. The process is called acid rock drainage (ARD), and it is a natural process that still are ongoing today in the area (Cáceras et al., 2013).
It is an action there the Earth pollutes itself, in human perspective. In modern times, human have created a greater impact on the environment, an additionally acid mine drainage (AMD) as a result of increasing oxidation of the sulfide ore due to mining (Rodríguez-Tovar and Martín-Peinado, 2014).
Mining
The IPB is of a high relevance, because the present of elements that are of an economical interest. It is not a recent exploration, signs of mining by past civilizations have been found, already starting for 5000 years ago. Even the Romans used the area for extraction of copper and developed a large-scale exploration of the IPB. After the Roman domination, mining inactivity was present in the area until the 18th century when the operation was taking up again and was escalating during the mid 19th century as a cause of the Industrial Revolution (Cáceras et al., 2013).
Nowadays, the resources that mainly are mined along the Río Tinto is sulfidic acid, iron and copper from pyrite. Additionally in a smaller amount zinc, tin and lead is extracted from sulfides, and also some amount of gold and silver can be found in the gossans. (Cáceras et al., 2013)
The mining industry have extensively affected the region. From the origin of the river to 10 km downstream, Río Tinto is flowing through a vast mining landscape. Variete types of leaching sources from the mines are immensely contaminating the river, where (besides Fe and S) As, Cd, Cu, Co, Mo, Ni, Pb, Se and Zn are the most common elements (Rodríguez-Tovar and Martín-Peinado, 2014).