Trace metals and other constitutive components in two sediment cores from a remote glacier-fed estuarine lagoon in southern Chile

Abstract

Laguna San Rafael is an estuarine basin at the base of an active glacier in the process of regression, which forms part of Chile’s remote Northern Ice Fields. The basin is about 140 m in maximum depth and is connected indirectly to the coastal zone by narrow channels. The present report presents preliminary data obtained from the first two sediment cores obtained from the center of Laguna San Rafael as ‘‘samples of opportunity’’ on an oceanographic cruise. Results from the samples are of unusual interest due to the remote location, absence of anthropogenic insult, and need to obtain background data prior to expansion of development of tourism in the area. The sediment cores were obtained from the deepest portion of the lagoon and later examined at six levels through the core. One sediment core was analyzed for organic carbon, organic nitrogen and total phosphorus and the second was analyzed for nine metals, two metal oxides, and silicon dioxide. The sediments were formed of gray-green, well-selected clay minerals, and contained low levels of C and N. There was little variation in the distribution of trace metals throughout the core. Sediment metal abundances were Ba > V Zn > Cr > Cu > Ni > Co > Pb > Cd. Concentrations were relatively low compared with the results observed from comparable fjords, with the exception of unexplained high values obtained for sedimentary Ba, V, and Zn.