Historical reconstruction of Small-scale gold mining activities in tropical wetland sediments in Bajo Cauca-Antioquia, Colombia

Abstract

Global mining investment in Latin America has increased exponentially over the last decade, resulting in the release of vast amounts of toxic metals into the environment. Here, historical trends of trace metals (i.e., Hg, Cr, Cu, Ni and Pb) of small-scale Gold Mining (ASGM) were reconstructed using a dated (²¹⁰Pb and ¹³⁷Cs) sediment core collected from a tropical wetland located in Antioquia (Colombia), a region characterized by increased mining development over the past century. Results showed that metal concentrations at the beginning of the 20t^h century were similar to background values, indicating that there is no impact of any previous anthropogenic activities. The significant increase in both sediment accumulation rates and total organic carbon (TOC) that occurred in the 1940s reflects the deforestation of the area due to the diversification of the economy (e.g. coffee cultivation, mining or animal husbandry). Both concentrations and accumulation rates of metals increased exponentially after the 1980s due to the reactivation of alluvial gold exploitation, reaching concentrations that exceeded up to 2-5 times the background values.