Evaluation of soil contamination surrounding an abandoned ore processing plant in Northeastern Algeria: spatial variability and seasonality effect

Abstract

Abandoned ore processing plants represent critical, long-term sources of environmental contamination and therefore constitute an important field of research for the subsequent rehabilitation of the area. The objective of this study was the evaluation of the level and spreading of soil contamination by trace metal elements in the vicinity of an abandoned ore processing plant in northeastern Algeria. Superficial soil samples were collected from 8 sampling stations located upstream, downstream, and directly at the abandoned ore processing plant during the wet and dry seasons. An environmental assessment of soil samples was conducted through the analysis of physicochemical characteristics: pH, electrical conductivity, and concentration of nutrients and potentially toxic elements in the available and total fractions.Soil samples showed marked spatial variability in pH values and electrical conductivities although, in general, soils collected in the both seasons showed an acid pH (3.66-4.19) and low-moderate EC (250-446 µS/cm)The total concentrations of S, Fe, Cr, As, Cu, Pb and Zn were elevated in all soil samples, exceeding the maximum values permitted for industrial land use according to soil legislation in several countries (e.g. Canada). For Ni and Cd, only some soil samples exceeded the maximum allowed values. The variation in the elements' availability revealed clear spatial heterogeneity between locations upstream and downstream of the abandoned ore processing plant. However, values remained consistently high near the plant regardless of position, which confirmed its role as the primary contamination source through multidirectional dispersion via runoff and wind.This work was funded by national funds through FCT – Fundação para a Ciência e a Tecnologia, I.P., under the projects UIDB/04129/2020 and UID/04129/2025 of LEAF-Linking Landscape, Environment, Agriculture and Food, Research Unit and LA/P/0092/2020 of Associate Laboratory TERRA