Environmental, ecological and human health risk assessment for Ba, Cr, Zn and V in minesoil after 20 years of restoration in southern Brazil

Heavy metals are a persistent threat in soils formed after mining (minesoils). This study was conducted in a 20-year randomized complete block design experiment installed within an active coal mine in Candiota, southern Brazil. Thus, this work provides a unique opportunity to assess long-term environmental and human health risks as affected by consistent and well-documented minesoil restoration practices. We aimed to assess the concentration of heavy metals (Zn, V, Ba, and Cr) in topsoil layers (0.00–0.10 and 0.10–0.20 m) and their associated ecological (with emphasis on soil fauna), environmental and human health risk as function of grass species used for revegetation of the minesoil (Hemarthria altissima, Cynodon dactylon, and Urochloa brizantha). Overall, Cr concentrations exceeded the regional quality reference value (25 mg kg−1), regardless of grass species and soil layer, despite 20 years of permanent revegetation. According to the pollution index (PI), the minesoil was classified as “moderately polluted” for Ba and Cr and as “severely polluted” for V, particularly under H. altissima (PI for V = 3.22 and Ba = 2.17). Among grass species, U. brizantha resulted in the lowest PI and ecological risk values and supported the highest abundance of soil fauna (2,309 individuals), compared to C. dactylon (2,075) and H. altissima (1,714). The human health risk assessment indicated “ingestion” as the main exposure pathway for adults, while “inhalation” accounted for approximately 75% of the total hazard index for children. Our findings highlight the persistent environmental and human health risks in the coal minesoils in Candiota, Brazil, even after 20 years of restoration. We strongly recommend the continued monitoring of these parameters to protect people and environment in Candiota region against contamination by heavy metals.