Human health risk assessment and riskiest heavy metal origin identification in urban soils of Yerevan, Armenia.

The pollution of urban soils by heavy metals remains a topical issue because of the risks it represents to human health. Heavy metal pollution levels of Yerevan's soils were evaluated using Pollution index and Enrichment factor, while associated health risk was assessed by US EPA model. The heavy metals with significant amount of PI > 1 values were observed for V (100%), Cr (95.4%), Ni (92.5%), Cu (95.6%), Zn (92.9%), Hg (89.0%), Pb (99.9%), As (72.0%), and Ba (61.6% of samples). EF showed that Yerevan topsoils were significantly contaminated with Hg, and moderately contaminated with V, Ni, Cu, Zn, Cr, and As. Topsoils near the smelting plants of molybdenum concentrate have moderately to extremely high contamination levels for Mo. Topsoils were moderate to extremely highly contaminated with Pb, too. The high amounts of samples with heavy metal contents greater than Maximum Acceptable Concentrations were observed for Pb, Cr, Zn, Ni, and Cu. Pb and Cr exceeded corresponding Soil Screening Levels in 3.39% and 2.43% of samples, correspondingly. The risk assessment showed children's multi-elemental non-carcinogenic risk and low level of arsenic carcinogenic risk in the whole Yerevan. The riskiest element was Pb which high contents in 72 risky sites correlate only with the metals having a natural origin. Moreover, its main source is historically polluted soils and Pb supposed to be redistributed in the city environment linked to the sorption complexes of Fe and Mn oxides.