Geochemistry pollution status and ecotoxicological risk assessment of heavy metal(oid)s in soil influenced by co-landfilling of MSW and sewage sludge, Morocco

Abstract

Landfilling activities are one of themajorsources of heavy metal(loid)s contamination. Thus, assessing the spatial distribution ofthese elementsand evaluatingtheirpotentialhazards to public health in the areas surrounding landfills is of utmost importance. In this paper, the synergistic effects of co-landfilling of Municipal Solid Waste (MSW) and Sewage Sludge (SS) were assessed using pollution indicators, PCA, HCA, and Montecarlo probabilistic human risk assessment. To do so, 19 soil, leachate, and sewage sludge samples were collected around the landfill and their content of heavy metal(oid)s was analyzed using Inductively Coupled Plasma (ICP-AES). The average concentrations of As, Cd, Cu, Pb, Zn, Cr, Ni, Co, and Fe were 0.98, 3.14, 36.87, 41.90, 148.43, 21.64, 32.07, 4.02, and 3143.74 mg/kg dry weight, respectively. The concentration of all metal(oid)s was higher than the geochemical background and the highest amount was observed at the first 100 m from the landfill and the sampling sites affected directly by sewage sludge. The values of pollution indexes (geo-accumulation index, enrichment factor, pollution load index, ecological risk index) showedthat soils in the vicinity of the landfill displayed moderate to high contamination level, with a strong potential ecological impact. Furthermore, multivariate statistical analysis demonstrated that anthropogenic sources related to disposal practices of MSW and SS are the main responsible behind the revealed pollution. In addition, the deterministic and probabilistic human risk assessment highlighted that the non-carcinogenic risk for children and adults still within the acceptable limits. However, carcinogenic risk was well above the threshold values (10−4) for children. The elevated pollution level reflected the dangerousness of synergistic dumping of SS and MSW, which renders the avoidance of their co-landfilling mandatory.