Effective metal concentrations in porewater and seawater labile metal concentrations associated with copper mine tailings disposal into the coastal waters of the Atacama region of northern Chile.

The objective of BASELINE is to publish short communications on different aspects of pollution of the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to 'Baseline—The New Format and Content' (Mar. Effective metal concentrations in porewater and seawater labile metal concentrations associated with copper mine tailings disposal into the coastal waters of the Atacama region of northern Chile Tailings dumping on the coast of the Atacama region takes place in the area around the small city of Cha~ n naral. The coast of this area is open to the Pacific Ocean swell and consists of rocky shores interspersed with sandy beaches of coarse sediments. Freshwater in this area is a scarce resource and significant freshwater input to the coastal environment occurs in rare flash floods only. As a result of the desert nature of the area population density is low, there is no agricultural activity and the only industrial activity is mining. Therefore , the only significant source of pollution in this costal environment is that derived from the mining activities , providing a unique opportunity to study the effects of tailings disposal and elevated metal concentration in the absence of the confounding effects of other groups of pollutants. Mine tailings from the copper mines at Potrerillos (now closed) and El Salvador have been dumped into coastal waters since 1939. Initially the tailings were deposited on to the beach at Playa Cha~ n naral (Fig. 1) and as a result the shore line is now a kilometre further out to sea than it had been originally (Castilla, 1983). In the 1970s the tailings were diverted to a new dumping point ten kilometres to the north of Cha~ n naral, adjacent to Playa Palito (Fig. 1). Again a large tailings beach formed in the littoral zone between Caleta La Lancha and Caleta Agua Hedionda, with significant amounts of tailings mixed in with the natural sediments on the beaches around Caleta Palito. In 1990, after local court action, a tailings settlement dam was constructed inland at Pampa Austral (60 km east of Cha~ n naral) and since then only 'clear water' tailings have been delivered to the coast with a legal maximum concentration of 2000 lg Cu l À1 (Castilla, 1996). The data included in this report were collected as part of a larger study on the …