Contamination of soil with potentially toxic metals and their bioaccumulation in wheat and associated health risk

The present study was conducted to investigate the concentrations of potential toxic metals (PTMs) in agricultural soil (n = 25) and their bioaccumulation in wheat crop (n = 25) collected from alongside the Kurram River, Pakistan. The highest concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in soil samples were 0.16, 19.5, 14.7, 46.5, 13.5, 14.5, 14.0, and 19.7 mg kg−1, respectively. In the edible tissues of cultivated wheat crop, the highest concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were 0.15, 10.00, 8.75, 22.25, 11.00, 11.25, 10.50, and 7.50 mg kg−1, respectively. The selected PTM concentrations in soil samples were observed within their respective permissible limits set by the Food and Agriculture Organization (FAO) and State Environmental Protection Administration (SEPA) China, while in wheat crops, the Cr and Pb concentrations were above the permissible limits of both FAO and SEPA China. The results showed that the orders of PTMs were Fe > Zn > Cr > Cu > Ni > Pb > Mn in soil and Fe > Ni > Mn > Pb > Cr > Cu > Zn in wheat. The highest PTM concentrations were reported in the sample collected near dumping sites. The results of different soil pollution indices including geo-accumulation index (Igeo), contamination factor (CF), and enrichment factor (EF) indicated that the soil of the study area was moderately to severely contaminated. The ADI values of wheat crops were less than 1, while the HQ varied among different PTMs with the highest value of 2.118 for Pb, and the lowest for Zn (0.007). The results indicated that anthropogenic intervention has made a substantial contribution to soil contamination with PTMs and subsequent uptake by wheat, which may exert potential human health risk.