Portal de Cartagena
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A doctoral thesis defended at the Universidad Politécnica de Cartagena (UPCT) concludes that some parts of the Mar Menor have high sediment rates from the nearby Cartagena-La Unión mining zone, and that jellyfish turn out to be good biomonitors of the levels Of marine water pollution by metals and other trace elements.
This is the first study that has been carried out since the 1970s on the impact of metal mining waste in the marine ecosystem of the Mar Menor and has been developed by the biologist, Ana Muñoz Vera, led by the professor of the area of ​​Soil Science and Agricultural Chemistry , Gregorio García.
To perform the thesis, samples of superficial and deep sediments were collected at ten different points of the Mar Menor and two species of jellyfish were used, the most common in the lagoon, Cotylorhiza tuberculata and Rhizostoma pulmo.
Among other conclusions, the doctoral thesis reveals very high levels of iron, zinc, arsenic, tin and lead in these jellyfish;
Of the order of 50 parts per million.
This finding should alert to several problems, according to Professor Gregorio García: "There are projects planned for commercial exploitation of jellyfish and with these concentrations of metal there may be problems.
The same happens when the jellyfish are removed from the lagoon, since they accumulate tons on land and can contribute to soil contamination. "
The thesis, with the highest score, reveals that from the 14th century until the end of the 19th century, the contribution of mining waste from the mountains was constant.
The rains led through the ramblas metals and metalloids that were deposited in the Mar Menor at the rate of 4 centimeters per century.
However from that date, the sediment is multiplied by six and this coincides with the increase of human, agricultural and industrial activity in the Mar Menor and in the lagoon itself (opening of collars and dredging).
García assesses the impact of mining contributions to the lagoon and compares it with other types of pollution: "The contamination of the Mar Menor by trace elements (heavy metals and arsenic) is a process that has occurred in this ecosystem in parallel to Its evolution during the last 2,500 years.
For this reason, due to the dynamics of these pollutants and the characteristics of the Mar Menor, the risk and the negative effects associated with polymetallic pollution are relatively unremarkable and of little relevance in relation to other pollution processes in the lagoon, basically Eutrophications by organic compounds, fertilizers and pesticides ".
The Sierra Minera de Cartagena-La Unión has been used since the Phoenicians in the fifth century BC.
C. until 1991, as mining site, mainly silver and lead.
With the open-pit mining and mineral processing techniques used by the multinational Peñarroya since 1957, more than 360 million tons of rocks were mobilized and about 90 sludge and 360 tailings ponds were created that still exist today. That about 170 million cubic meters of sterile materials have been deposited.
There is no exact figure of the quantities that have gone to the Mar Menor throughout the centuries although the director of the thesis speaks of possibly millions of tons.
Source: UPCT
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