Origin and risk assessment, and evaluation of heavy metal pollution in the soil and air of Tehran (case study: central district in Tehran city)

Heavy metal pollution has become a global issue. In this study, the concentrations of some heavy metals were measured, including chromium, arsenic, nickel, copper, zinc, lead, and cadmium. In addition, several assessments were identified, including enrichment factor, chemical partitioning, pollution index, ecological risk, health risk assessment, and the toxicity characteristic leaching procedure. The concentration of heavy metals in the air, soil, and Dust are Zn = 101 > Pb = 33.8 > Cu = 15.3 > As = 5.8 > Cr = 5.3 > Ni = 4.3 > Cd = 3.22 µg/m3, Zn = 138 > Pb = 46 > Cu = 42 > Ni = 31 > Cr = 30 > As = 10.4 > Cd = 2.5 mg/kg, and Zn = 225 > Cu = 95 > Pb = 73 > Cr = 42 > Ni = 32 > As = 9.4 mg/kg, respectively. Based on the results of the soil and particles, EF for Cr < Ni < As < Cu < Zn < Pb < Cd minimally and highly enriched, respectively, and the results related to Ni < Cr < As < Cu < Zn < Pb also suggested that they minimally and significantly enriched, respectively. The results for the ecological risk of the soil and particles were 281.47 (medium risk) and 44.69 (low risk), respectively. The results of chemical separation indicated the Cd with an anthropogenic origin with the remaining metals were originally lithogenous. The Ipoll index results for metals in the soil Ni < Cu < Zn < As < Pb < Cr < Cd were in non-contaminated and moderately-contaminated ranges except for Cd while the results for metals in particles As < Ni < Cr < Zn < Cu < Pb were in non-contaminated and moderately-contaminated ranges, respectively. The results from concentrations obtained by the TCLP method were less than the standard value, indicating no contamination. Finally, the results of non-cancer risk assessments showed a total index of 1.15E+00, which is more than1. It should be noted that one cancer patient was 1.29E−03 and the total number of cancers was 323 in a lifetime.