Probabilistic Assessment of the Heavy Metal Pollution in Debrecen’s Topsoil

Understanding better the spatial and subsurface infiltration patterns of heavy metal distribution in urban soils can help in environmental and health risk assessment and the development of effective environmental policy. The present paper investigates the overall environmental quality of the Debrecen area in terms of heavy metal pollution and describes a simulation procedure for the spatial and statistical patterns of heavy metals in atmospheric deposited dust samples and the spatial diversity of health vulnerability. The research is based on the evaluation of 300 soil samples from Debrecen and its surroundings. Maps of topsoil major heavy metal distributions, including As, Cd, Cr, Co, Cu, Mo, Ni, Pb, and Zn, were obtained using sequential Gaussian simulation. Then, the pollution levels were determined from the stochastic maps, thus obtaining a comprehensive quantitative pollution characterization of the nine elements in the city. According to the results, the potential risk of pollutants to the environment is in the order of Cd > Mo > As > Cu > Ni > Cr > Pb > Co > Zn, with a pollution load of 0.66. Cd, Mo, and Cu are the main toxic pollutants in Debrecen topsoils, with mean concentrations of 1.9 mg/kg, 77.3 mg/kg, and 1.4 mg/kg, exceeding the threshold values by 0.9 mg/kg, 2.3 mg/kg, and 0.4 mg/kg, respectively. The stochastic models assessed the uncertainties and risks related to the spatial distribution of heavy metals in soil within the contaminated areas, and a positive correlation can be found between the increase in pollution values above the predetermined threshold limits and the corresponding increase in threshold levels. Additionally, there is a consistent decrease in the relative area of excess contamination, although the ecological pollution index (96.9) revealed the Debrecen region as a hotspot area for considerable risk of contamination that needs continuous monitoring and remediation.