Mercury contamination in chile: a chronicle of a problem foretold.

Abstract

This review analyzes the effects of environmental mercury contamination in Chile. This contamination generates one of the most important environmental conflicts in the country in that it affects air, ground, and water (rivers and oceans), which are fundamental in maintaining natural biotic equilibrium and at the same time important for the nation's economy. Chile possesses extraordinarily wealthy mining resources between Regions I and IV that have developed into an extraction industry essential for the economy of the country. However, waste discharges from this production have created an environmental problem in that the majority of the mines are located in the Andes mountain range, or areas close by, and the water used in the extraction process is deposited into the rivers, significantly increasing the amount of chemical contamination. Therefore, the cities and downstream waters used in agriculture suffer the negative consequences of a natural resource that is becoming more and more scarce. In addition, minerals released from mills into the atmosphere are deposited onto the soil, drastically affecting the biological resources of these areas. One of these affected areas is the Metropolitan region, where one of the highest contamination levels of mercury in the country was found in one of its affluents due to industrial and domestic waste discharge. In a country that is only 200 km in width, the gathering of all these contaminants in the rivers results in a rapid flow to the ocean, thereby contaminating coastal waters and the biota. In general, this contamination has been detected in semiclosed bodies of water (bays). Between Regions VII and IX, the principal sources of mercury contamination are related to cellulose industrial sites (Regions VII and VIII) and, until the 1980s, the bleach-soda industry. The most important industrial and fishing activity is also found in this area. In San Vicente Bay, waste discharges released into the ocean include sewage, industrial residues, residues from fishing and mining industries, hydrocarbons, petrochemical derivatives, oils, and detergents. This combination of chemical assault makes the San Vicente Bay the most contaminated in the country and the area where the majority of mercury contamination studies have been carried out. Between Regions X and XII, mercury contamination is reduced due to decreased release of domestic residues, especially batteries and sanitary waste. Beginning with the decade of the 1990s, Chile made a great effort to decrease contamination through governmental organizations (CONAMA, SERNAGEOMIN, DGA, ECOMIN, SONAMI), nongovernmental organizations (NGOs), universities, government mining industries (CODELCO, ENAMI), and private mining industries (El Indio, La Escondida, La Candelaria, Fachinal, etc). These reduction efforts within the last 10 years exceed $900 million, and in the private mining sector alone more than 1,100 monitoring stations have been installed and more than 100,000 environmental measurements have been carried out each year. Furthermore, an important educational program on the use of mercury has been implemented in the small mining area to decrease contamination to the air, water, and soil. However, the consequences of mercury accumulation are seen in their damaging effects to the rivers that deliver water to crops and cities, in the bays where food is extracted, and in the air of some cities where there exist mills that release chemical substances into the atmosphere.