Source apportionment, carcinogenic and non-carcinogenic risks assessment of soil heavy metals in marble waste polluted environment; role of vegetation in risk mitigation

Marble industrial pollution introduce significant heavy metals contamination in soil. However, limited research studies addressed source apportionment, and carcinogenic - non-carcinogenic risks assessment of pollutants within the marble waste polluted ecosystem (MWPE). Therefore, positive matrix factorization (PMF), environmental and human health risk indices along with the Monte Carlo Simulation modeling and Structural Equation Modeling (SEM) procedures were applied to examine the health risks and role of vegetation abundance in mitigation of those risks. The PMF results comprehended four major sources of the heavy metals (HMs) pollution i.e., F1 (traffic), F2 (natural), F3 (dolomite marble) and F4 (calcite marble). Nickel (1.85 to 50.55 mg/kg), copper (3.51–91.68), cadmium (0.59–56.93 mg/kg), and zinc (0.7–148.55 mg/kg) exceeded from the recommended threshold levels given by World Health Organization (WHO). The MWPE exhibited a high degree of HMs (cadmium, chromium, iron, nickel, manganese and zinc) pollution based on the Degree of Contamination (8.43–78.61), Metal Pollution Index (>1) and potential ecological risk index (1520.11). Human health risks based on hazard quotient and hazard index (>1) indicated a high risk of individual HMs both in adults and children in the MWPE. Ni and Cd were the dominant HMs responsible for the carcinogenic as well as non-carcinogenic risk in adults and children followed by Cr>Mn>Cu>Zn. Dermal exposure has been recorded as the major contribution pathway followed by inhalation and ingestion for health risks. SEM comprehends that with the increase in HMs (Cd, Cr, Cu, Fe, Mn, Ni, Zn) concentration, the associated environmental risk (PERI, MPI & DC) also increases (β=0.97). While higher plant species abundance mitigates or reduces (β= -0.62) the environmental risks within the MWPE. It is concluded that the HMs released from marble mining and processing cause significant environmental and human health (carcinogenic and non-carcinogenic) risks, while plant species play an important role in the mitigation of these risks and toxicities. It is recommended to increase the vegetation cover by cultivating more plants especially the indicator species in the MWPE through afforestation and reforestation. Awareness programs about the health risks associated with HM exposure are necessary to educate people working in the marble industry or residing near marble processing units along, with protective pollution mitigation strategies.