Project Copper Tailings

Study sitesThesisPapers

Abstract

The effects of copper mine tailings disposal on the littoral meiofaunal assemblages of the Chañaral area of northern Chile were studied. Tailings disposal has taken place along this stretch of coastline since the 1938. The tailings, derived from the Potrerillos (now closed) and the El Salvador mines, were sent down the dry river bed of the Rio Salado to be deposited in Chañaral bay resulting in the formation of an extensive tailings beach. In the 1975 the tailings were redirected from the Rio Salado via a tailings canal to a new dumping point at Caleta Palito, ten kilometres north of Chañaral bay. Again a large tailings beach formed in the littoral zone between Caleta Agua Hedionda and Caleta La Lancha. In 1990 after court action a tailings settlement dam was constructed at Pampa Austral where the solid component of the tailings was allowed to settle out. Since then only ‘clear water’ tailings have been delivered to the coast at Caleta Palito.

A sediment quality triad (SQT) approach was used to examine the effects of the tailings, supported by laboratory experiments designed to look at each of the perturbing components of the tailings individually. The first element of the SQT was an analysis of the physicochemical nature of the beaches studied. The concentrations of labile metals, assumed to be equivalent to the bioavailable metals, were measured in both the porewater and overlying seawater using the diffusion gel technique (DGT). An analysis of the sediment structure was also conducted. The second element of the SQT was an analysis of the meiofaunal assemblage structure on each of the beaches studied using both univariate and multivariate (PRIMER) techniques. The third element of the SQT was the use of whole assemblage meiofaunal bioassays conducted in microcosms. Finally, to provide supporting information, a series of laboratory microcosm experiments were conducted to identify the effects of copper alone and the physical impact of the tailings on meiofaunal assemblages. Twelve sites were used for the study, and were divided a priori in to three groups. The first group were the reference sites (Las Piscinas, Torres del Inca and Playa Zenteno) which lay sufficiently far to the south as to be unaffected by the tailings dumping. The second group were the northern sites within the Parque Nacional Pan de Azucar (Puerto Pan de Azucar, Frente Isla Pan de Azucar and Playa Blanca), these sites on visual inspection did not appear to be impacted by the tailings dumping. The third group were those sites located around the dumping points (Caleta La Lancha, Caleta Agua Hedionda, Palito 1000m Norte, Playa Palito, Palito 2000m Sur and Playa Chañaral) which on visual inspection showed clear signs of impact by the tailings dumping.

Though a number of metals could be associated with the tailings discharge at Caleta Palito by their distribution in the seawater samples, only in the case of copper was there a clear association with the tailings distribution in both the seawater and porewater samples. The concentrations of copper in the seawater and porewater were highly correlated and it was assumed that the tailings on the beaches was the source of copper in the adjacent seawater. When compared to the reference sites, the meiofaunal assemblages at the impacted sites (the third group) had significantly lower densities and diversities, at the northern sites only the densities were lower. The two groups within the meiofauna that proved to be most sensitive to the effects of tailings dumping were the foraminiferans and the harpacticoid copepods. Otoplanid turbellarians were identified as characteristic of the beaches impacted with tailings. BIOENV (PRIMER) analysis of the data indicated that the combination of porewater copper and the amount of tailings present were most responsible for the observed structure of the meiofaunal assemblages. The bioassay of the sediments indicated that the sediments from the northern sites were not toxic to the test meiofaunal assemblages, but confirmed the toxicity of the sediments from the impacted sites. The response of the meiofaunal assemblages to increased bioavailable copper was confirmed using the laboratory microcosm experiments. The effects of the reduction interstitial space, the physical impact of the tailings, depended upon the group under consideration. For the foraminiferans the increased surface area resulted in an increase in the population density, however the reverse was the case for the harpacticoid copepods. The effects of the reduction of interstitial space for the polychaete Saccocirrus were negative, unable to burrow it tended to congregate on the surface of the sediment were it would be exposed to an increased risk of predation and loss of position in the littoral zone.

Using the SQT methodology to summarise the findings of this research I was able to further divide the impacted sites in to two groups. The most severely impacted sites were those beaches composed only of tailings (Caleta La Lancha, Caleta Agua Hedionda and Playa Chañaral) where both the increased concentration of bioavailable copper and the reduction of interstitial space were acting on the resident meiofaunal assemblages. The less severely impacted sites were those where there were tailings present but the tailings had not completely smothered the beach (Palito 1000m Norte, Playa Palito and Palito 2000m Sur). At these sites the bioavailable concentrations of copper were generally lower and the reduction in the interstitial space less severe.

This research supports the use of the sediment quality triad as none of the individual components alone was able to predict the overall level of pollution-induced degradation at the sites studied. The combination of all three components gives a much more comprehensive picture of the state of the sites than any one component alone would have.

Thesis

Lee, M.R. (2001) The Effects of Copper Mine Tailings Disposal on the Littoral Meiofaunal Assemblages of the Chañaral Area of Northern Chile. PhD. Thesis. University of Wales, Bangor

Papers

Lee, M.R., Correa, J.A. & Castilla, J.C. (2001) An assessment of the potential use of the nematode to copepod ratio in the monitoring of metals pollution. The Chañaral case. Marine Pollution Bulletin. 42: 696-701.

Lee, M.R., Correa, J.A. & Zhang, H. (2002) 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. Marine Pollution Bulletin. 44: 956-961.

Lee, M.R. & Correa, J.A. (2004) Copper mine tailings disposal: Consequences for the interstitial polychaete Saccocirrus sonomacus. (Canalipalpata, Protodrilida). Journal of the Marine Biological Association of the United Kingdom. 84: 603-606.

Lee, M.R. & Correa, J.A. (2005) The effects of copper mine tailings on the littoral meiofaunal assemblages of the Atacama region of northern Chile. Marine Environmental Research. 59: 1-18.

Lee, M.R., Correa, J.A. & Seed, R. (2006) A sediment quality triad analysis of the impact of copper mine tailings disposal on the littoral sedimentary environment of the Atacama region of northern Chile. Marine Pollution Bulletin. 52: 1389-1395.

Lee, M.R. & Correa, J.A. (2007) An assessment of the impact of copper mine tailings disposal on meiofaunal assemblages using microcosm bioassays. Marine Environmental Research. 64: 1-20.