HEAVY METAL CONTAMINATION IN LAKE IZABAL, GUATEMALA: PRELIMINARY STUDY OF A SHORT SEDIMENT CORE

Mining activities near Lake Izabal, the largest freshwater lake in Guatemala, and the lake’s catchment, are a major concern due to their possible role in contaminating this aquatic ecosystem. Significant contamination in the area could be catastrophic, as it hosts significant protected forest land and many endangered species. X-ray fluorescence (XRF) data obtained from a five-meter sediment core taken as part of a pilot study in the interdistributary bay of the Polochic Delta, Lake Izabal, eastern Guatemala, contains a record of recent heavy metal contamination. The core contains a 420-year record of sedimentation based on chronology obtained by ²¹⁰Pb dating and by extrapolation of six ¹⁴C dates from organic matter obtained throughout the core. The core is characterized by muddy homogeneous beds with intervals of thinly laminated and thinly bedded silty and sandy mud. XRF data shows background levels of lead (Pb) ranging between 200-300 counts/second (c/s) and zinc (Zn) levels ranging between 800-1200 c/s. From 90 cm (ca. 1950 CE) to 70 cm (ca. 1970 CE), Pb and Zn levels increase to 1200 c/s and 5000 c/s, respectively. Nickel mining activities in Lake Izabal has been carried out since 1960 with several interruptions. However, no significant increase in nickel was observed, with levels ranging between 1000-1300 c/s. One of the most significant deposits of lead, zinc, and silver that has been discovered in Guatemala is located near Cobán, Alta Verapaz, ~ 130 km away from Lake Izabal. The mine is located near the Cahabon River, a main tributary of the lake. Mining activity in the area started in 1948 and ceased in the 1980s, correlating well with the increase in lead and zinc observed in the core. The results of this study are useful to reconstruct historical changes in heavy metal concentrations, especially those that derive from mining activities. These results allow us to assess the anthropogenic impacts in the lake system and can be helpful with the current remediation efforts carried out by national entities in charge of managing and protecting this aquatic ecosystem. These data could provide a solid baseline to regulate mining activities that are taking place in the watershed.