Heavy Metals in Soils: An Investigation of the Contaminated Floodplains Around the Sinu River, Colombia.

Heavy metal contamination in rivers mostly originates from anthropogenic sources such as industrial activities, mining, agriculture, and urban runoff. These metals accumulate in river sediments and impact living organisms and the surrounding ecosystem. Historically, some rivers in Colombia have faced issues related to heavy metal contamination, in particular from gold mining activities, which can lead to the release of heavy metals into waterways. To assess the current status of heavy metal presence in the Sinú River, one of the most important rivers in northern Colombia, we analyzed sediment samples collected in a section of the river between the towns of Santa Isabel and Montería. ICP-MS analysis found concentrations of Hg, Cd and Ni up to five times larger than the baseline concentrations, while concentrations of Pb, Zn and Cr were consistently below the baseline. The measured concentrations varied with both geographical location and sampling depth. During the dry season heavy metals accumulate near the surface, while rains spread them below the surface and into the groundwater, and across the surrounding land. These abnormal concentrations of potentially toxic elements are probably related to the widespread use of Hg in illegal gold mining activities, which are prevalent in the region, while Cd and Ni contamination probably derives from mining, as well as from agricultural practices and industrial discharges. The results point to the necessity to continuously monitor the state of the river and develop management strategies to reduce heavy metal contamination, protecting the health of the ecosystem and of the neighboring communities.