Assessment of potential contamination of Paramo soil and downstream water supplies in a coal-mining region of Colombia

Abstract Colombia's water supply catchments are under increasing pressure from urban development, industry, mining and agriculture and associated emissions. In particular, the impacts of coal mining on water quality are commonly questioned; however, the answers are complicated in regions with multiple types of land use and discharge. Investigation of the degree and reasons for water quality degradation in such regions has been limited. Furthermore, the impacts on soils and the Paramo ecosystems, and their relationship to water quality, are commonly disregarded. Here we present a review of the environmental impacts in the Lenguazaque catchment in the department of Cundinamarca. Surface water, sediments and soil measurements taken on a transect from Paramo to the valley were analyzed along with coal mine outlet, urban discharge and agricultural data. Observed alterations of baseline water quality include a significant decrease in dissolved oxygen concentration and an increase of electrical conductivity, turbidity, color and total solids concentration. High heavy metals were also measured, in both water and soil samples. The metal accumulation capacity of soils is effective and reduces concentrations measured in water. Nonpoint sources include runoff and airborne particles released from coke production, both difficult to quantify and characterize. Point sources such as agricultural, mining and urban wastewater discharges are commonly found in the area and their composition has been previously documented. This study indicates that in order to reduce contamination, illegal and small-scale mining in the area should be controlled and that further treatment of mine and urban discharges is needed. It also demonstrated the key role that soils play in the mitigation of metal pollution in rivers emphasizing that those should be included in Colombian environmental quality legislation.