Overview
Taghavi and colleagues measured trace elements in agricultural soils used for saffron cultivation in Gonabad County, Iran. This is upstream supply-chain evidence: it reports the soil reservoir and soil-exposure indices that can inform saffron-origin contamination context, but it does not measure saffron stigmas or finished spice. The page therefore treats the values as soil-to-crop pathway context, not as saffron occurrence data.
Key numbers
The study sampled 16 saffron farmlands and reported trace-element concentrations in mg/kg dry weight. Table 3 gives average soil concentrations of cadmium (Cd) 0.102 mg/kg, Co 6.968 mg/kg, chromium (Cr) 22.550 mg/kg, Cu 29.263 mg/kg, Mn 457.281 mg/kg, nickel (Ni) 34.234 mg/kg, lead (Pb) 13.617 mg/kg, Zn 54.482 mg/kg, and Fe 19,683.6 mg/kg.
Table 3 gives observed ranges of Cd 0.072-0.14 mg/kg, Co 6.194-8.185 mg/kg, Cr 20.25-25.91 mg/kg, Cu 24.325-35.895 mg/kg, Mn 371.441-516.136 mg/kg, Ni 32.027-37.743 mg/kg, Pb 11.628-15.527 mg/kg, Zn 35.469-99.827 mg/kg, and Fe 14,254.5-24,005.2 mg/kg. The local Gonabad background values used for pollution-index calculations were Cd 0.409 mg/kg, Co 9.13 mg/kg, Cr 41.88 mg/kg, Cu 40.34 mg/kg, Mn 546.704 mg/kg, Ni 20.3 mg/kg, Pb 20.08 mg/kg, Zn 92.99 mg/kg, and Fe 17,963.1 mg/kg.
The authors report soil pH values ranging from 7.2 to 7.9, described as neutral to sub-alkaline. They compared soil results with FAO/WHO and Iranian agricultural-soil standards and concluded that the sampled soils were safe for agricultural purposes in terms of the measured trace elements.
For non-carcinogenic soil-exposure risk, Table 6 reports summed hazard indices of 6.97E-02 for adults and 4.38E-01 for children, both below 1. The route contribution order was ingestion > inhalation > skin contact for both subpopulations.
For carcinogenic soil-exposure risk, Table 7 reports adult total cancer risk values of Cd 6.90E-10, Cr 1.66E-05, Pb 1.65E-07, and Ni 9.14E-05. Child total cancer risk values were Cd 5.42E-09, Cr 1.52E-04, Pb 1.54E-06, and Ni 5.82E-05.
For soil pollution indices, mean contamination-factor values decreased in the order Ni 1.68, Mn 0.83, Co 0.76, Fe 0.73, Cu 0.72, Pb 0.67, Zn 0.58, Cr 0.53, Cd 0.24. The authors state that CF values for Ni and Zn exceeded 1 in 100% and 6.25% of the farmlands, respectively. Mean enrichment-factor values were Cd 0.34, Co 1.04, Cr 0.74, Cu 1, Mn 1.15, Ni 2.32, Pb 0.93, Zn 0.80, and Fe 1.
Methods (brief)
Composite soil samples were collected from 16 saffron farms in Gonabad County, with background samples from three control sites with no farming or human activity. Soil was air-dried, oven-dried at 80 degrees C for 72 h, ground, homogenized, sieved through 2 mm mesh, and digested with HNO3/HCl at 1/3 before filtration through 0.45 µm cellulose acetate. Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and Fe were measured by ICP-OES. The reported LOQs were Cd 0.001 mg/kg, Co 0.007 mg/kg, Cr 0.001 mg/kg, Cu 0.005 mg/kg, Mn 0.001 mg/kg, Ni 0.05 mg/kg, Pb 0.07 mg/kg, Zn 0.003 mg/kg, and Fe 0.003 mg/kg; recovery values were Cd 94.5%, Co 93.5%, Cr 95.4%, Cu 109.8%, Mn 98.5%, Ni 97.5%, Pb 79.8%, and Zn 98.1%.
Related evidence
- Soil-to-plant transfer of heavy metals
- Cadmium
- Cobalt
- Chromium
- Lead
- Nickel
- Copper
- Manganese
- Zinc
- Iron
Update history
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