Impact of open-air dumping of urban solid waste on soil toxicity and properties in a tropical environment

Open dumping (OD) is uncontrolled dumping of solid waste (SW) in an environment. It involves the illegal practice of dumping waste in areas not designated for waste management, such as open lands, flowing water bodies, or exposed waste piles. OD can contain a complex mixture of organic fractions, and various contaminants that, when infiltrated into the soil through leachate, compromise its stability and resistance. These contaminants can reach aquatic ecosystems and natural resources through runoff. In this study, the impact of OD on soil and sediments toxicity and properties in the Caribbean region of Colombia, specifically in a tropical dry forest (Td-F) environment, was evaluated. A characterization of samples was performed, assessing their chemical composition, concentration of trace elements, physical properties, toxicity, and associated risks. The physicochemical conditions were determined using standardized methodologies, while trace elements were determined by inductively coupled plasma mass spectrometry (ICP-MS) after a microwave-assisted digestion method. Additionally, toxicological bioassays were carried out with the Caenorhabditis elegans biological model. Soil and sediments samples were collected at nine sampling points distributed throughout the area, at a depth of 20 cm, and weighing approximately 1 kg. The results suggest that the soil in the OD exhibits slight to moderate deterioration associated with the continuous accumulation of SW. The results reveal soil with organic matter (OM) (3 to 8%), density of 2.0 to 2.44 g cm⁻³, pH from 7.67 to 8.40, carbon content from 5.94% to 6.89%, and phosphorus up to 14.8 g L⁻¹. The decreasing concentration order in soils was chromium (Cr) > nickel (Ni) > copper (Cu) > lead (Pb) > cobalt (Co) > arsenic (As) > cadmium (Cd). The soil and sediment samples showed contamination by Ni, Cu, and Cd. Analyzing the impact of solid waste dumping in the Caribbean region directly contributes to the goal of promoting more sustainable cities, ensuring the conservation of terrestrial ecosystems. Finally, this study provides key information to strengthen environmental policies and sustainable solid waste management strategies in coordination with local stakeholders and territorial authorities. The results may serve as a baseline for monitoring, prevention, and mitigation programs related to contamination by potentially toxic elements, while also contributing to the strengthening of environmental governance and the protection of ecosystems and public health.