Spatial distribution, pollution characteristics and risk assessment of heavy metals in soils: A case study in the desert city of India

The study aims to assess the accumulation of ten heavy metals (As, Cd, Cr, Co, Cu, Fe, Mn, Ni, Pb, and Zn) in soils of the desert city of Rajasthan. Heavy metals analysis in industrial soils was assessed by following standard methods for two consecutive years. Principal component analysis (PCA), correlation matrix, spatial distribution, contamination factor (CF), degree of contamination (CD), pollution load index (PLI) and potential ecological risk index (PERI) in soil and plants were assessed to find out the metal contamination level. Furthermore, this study also conducted human health risk assessment for adults and children by using the health risk assessment model recommended by the United States Environmental Protection Agency (USEPA). The highest concentration of heavy metals such as As (7.74 mg/kg), Cu (18.22 mg/kg), Fe (2981 mg/kg), Ni (25.11 mg/kg), and Zn (106.12) in Rani Bazar, Co (5.54 mg/kg) and Pb (13.86 mg/kg) in Bichhwal and Cr (14.32 mg/kg) and Mn (71.8 mg/kg) in Khara in 2019. Whereas, Cd (4.50 mg/kg) was maximum in Karni industrial soil in 2020. Whereas, the high metal content in plants was observed mainly in 2020 such as As (30.9 mg/kg) and Zn (376.7 mg/kg) in Abutilon indicum, Cd (29.93 mg/kg) in Calotropis procera, Cr (341.6 mg/kg), Cu (400.61 mg/kg) and Ni (301.99 mg/kg) in Aerva pseudotomentosa, Fe (14496 mg/kg) and Mn (1319.89 mg/kg) in Cicer arietinum, Pb (976.7 mg/kg) in Coriandrum sativum. Though only Citrullus colocynthis contain high concentration of Co (11.96 mg/kg) in 2019. Plant species show hyperaccumulation towards As, Cd, Cr, Cu, Co, Fe, Mn, Ni, Pb, and Zn with more than 1 values of bioconcentration factor and translocation factor specifying their effectiveness in uptake and transfer of more than one element from soil to shoot. The non-carcinogenic heath risk assessment shows that HQ values for heavy metals such as As, Cd, Cr, Cu, Fe, Ni, Mn, Pb in plants were above the recommended guideline level. In carcinogenic risk assessment, CRI in adult group of Rani Bazar industrial soil in 2019 were found at high cancer risk. Moreover, selected plants also show cancer risk for As, Cd, Cr, Ni and Pb metals. Therefore, consumption of plants may produce cancer risk in humans too. Henceforth, monitoring and management of heavy metals is advocated to avert the metal health hazards to humans. The study can be utilized as baseline for further human health risk assessment of heavy metals.