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

Global mining activities in Latin America have increased exponentially over the last decade. The present study aims to assess the historical impact of Artisanal and Small-scale Gold Mining activities (ASGM) in the Department of Antioquia, Colombia, a region characterized by increased mining development over the past century. Historical trends of heavy metals (i.e., Ag, Cr, Cu, Hg, Ni, Pb, and Zn) were reconstructed for the past century in a tropical wetland near the mining district. Results indicate that local mining operations did not have a significant influence in the area until the mid-20th century when metal concentrations began to increase and exceeded background values. The significant increase in both sediment accumulation rates and total organic carbon (TOC) content during the 1920s 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 as a consequence of the reactivation of alluvial gold exploitation, reaching values that exceeded up to 2-5 times the background levels. The historical metal trends in sediments from Las Palmas wetland reflected the historical socio-economic development in Antioquia and can be used as a good proxy for evaluating anthropogenic impacts in this region.

Impact of terrestrial mining and intensive agriculture in pollution of estuarine surface sediments: Spatial distribution of trace metals in the Gulf of Urabá, Colombia.

The Gulf of Urabá (northwestern Colombia) is a geostrategic region, rich in biodiversity and natural resources. Its economy is mainly based on agribusinesses and mining activities. In this research is determined the impact of these activities in bottom surface sediments of the estuary. Thus, grain size, total organic carbon, total nitrogen, carbonates, Ag, Al, Ca, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb and Zn concentrations from 17 surface sediment samples were obtained and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated to determine the contamination level in the gulf. EF and Igeo values revealed that the estuary is extremely contaminated with Ag and moderately contaminated with Zn. Therefore, the observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals and the enrichment with Zn associated mainly to pesticides used in banana plantations.