Sir

Garcia-Guinea and Huascar1 discuss the catastrophic environmental impact of huge quantities of waste materials from polymetallic ore mining in South America. A similar situation — fortunately without such dramatic consequences so far — affects the southwest Mediterranean coastline.

Spain, Morocco, Algeria and Tunisia have a variety of volcanic-related mineral deposits (especially oxides, sulphides and sulphosalts of base and precious metals). Southeast Spain has been mined since 3000 bc, and has more than 120 abandoned mines — the highest number in Europe — concentrated along approximately 300 km of the Mediterranean coastline. Immense quantities of metal sulphides (lead, zinc and silver in Cartagena, Sierra Almagrera), precious metals (gold and silver in Rodalquilar, Las Herrerías) and mercury-antimony (Valle del Azogue) have been extracted; some mines are still active (for example, the Las Herrerías open pit).

Over the past six years, I have led several mineralogical, geochemical and metallogenetic research projects in this region, in cooperation with the Spanish Comision Interministerial de Ciencia y Tecnología and IUGS/Unesco2,3. There are no regional environmental studies of the intense mining activity of the area. (There are more than 2,000 mining pits and 230 tailing dams and dumps in the province of Almeria alone4.) There are also industrial and ore-dressing plants close to the coast.

Despite this huge volume of mining waste, no geochemical mapping of the toxic element anomalies has been carried out — unlike in other major mining districts (for example the Iberian ‘Pyrite Belt’5, the Tees River basin6) — and no data exist about the geographical distribution patterns of the mining-related chemical elements. Monitoring studies of metal distribution are only local and are restricted to areas where the pollution has reached extremely high levels. The most critical case is Portman Bay (Spain): this is the most contaminated bay in the entire Mediterranean, and a perfect example of ecotoxic pollution of a coastal environment by mine tailings. The waste from mining operations was discharged directly into the inner part of the bay for more than 30 years, polluting the sea for a radius of several kilometres7.

On a larger scale, the southwest Mediterranean area is sadly contaminated, as has been shown by the high concentration of arsenic found in water, soils and sludges8, lead in bivalve shells (up to 100 parts per million, more than 30 times the average mean)9, methylmercury, selenium, cadmium, zinc and lead in dolphins10, lead and zinc in fish and other marine organisms11 and so on. This pollution is also conditioned by the interaction of cyclone and anticyclone streams through the Straits of Gibraltar and from the north of Corsica. These streams converge in the Algerian-Provençal marine basin, meeting in the Alboran sea (where high quantities of cadmium and manganese have been detected12), and cause an accumulation of mining tailings and industrial waste.

The most recent Unesco Science World Report stresses that environmental preservation and solving problems created by human activity is one of the most important challenges now facing mankind, and the World Conservation Union considers the Mediterranean a protected area. It is therefore of the utmost importance that the European Union and North African countries affected should monitor this environmental threat which is progressively poisoning rivers, aquifers, soils, beaches and the sea.