Overview
Shar and coauthors measured Pb, Cd, Cr, Cu, Zn, and Fe in 36 composite sunflower seed samples (six composites from each of six districts) collected from different ecological zones of Sindh, Pakistan during the rabi crop season 2022-2023. The source is directly routeable to sunflower seeds and provides per-site dry-weight means with SDs. Tando jam emerges as the priority Pb/Cd/Cr contamination cluster (attributed to upstream industrial effluents and urban drainage), while Kotri’s higher Fe/Zn/Cu is attributed to naturally ferruginous alluvial soils of the lower Indus plain.
Key numbers
- n=36 composite sunflower seed samples (6 districts × 6 composites) from Sindh ecological zones.
- Dry-weight per-site mean concentration ranges across the six districts were Cd 0.006-0.014 mg/kg, Pb 0.038-0.063 mg/kg, Cr 0.11-0.19 mg/kg, Cu 2.44-3.74 mg/kg, Zn 14.32-20.15 mg/kg, and Fe 36.1-47.3 mg/kg.
- Across-site grand means (mg/kg dry weight): Cd 0.009 ± 0.003, Pb 0.049 ± 0.009, Cr 0.15 ± 0.04, Cu 3.15 ± 0.46, Zn 17.77 ± 2.1, Fe 41.7 ± 3.8.
- All metal concentrations remained well within FAO/WHO permissible limits according to the authors (limits cited: Zn 99.4, Pb 0.3, Cd 0.2, Cu 73.3, Fe 425.5 mg/kg; no specific Cr limit).
- Tando jam recorded the highest Pb (0.063), Cd (0.014), and Cr (0.18) mg/kg — a distinct Pb/Cd/Cr contamination cluster the authors attribute to upstream industrial effluents and urban drainage affecting irrigation water.
- Kotri recorded the highest Zn (20.15), Cu (3.74), and Fe (47.3) mg/kg — attributed by the authors to naturally ferruginous alluvial soils of the lower Indus plain rather than anthropogenic loading.
- Spike recovery for all metals 92.4-98.6%; CV < 5%; triplicate measurements; FAAS calibration R² ≥ 0.999.
Methods (brief)
Samples were washed with deionized water, oven-dried at 80°C for 48 h, ground, and sieved through a 2 mm mesh. A 1.0 g powdered subsample was digested with HNO₃-H₂O₂ (2:1, v/v) on a hot plate at 120-150°C for 3-4 h, filtered through Whatman No. 42, and diluted to 50 mL in 0.1 M HNO₃. Six metals (Pb, Cd, Cr, Cu, Zn, Fe) were determined on a Shimadzu AA atomic absorption spectrometer with element-specific hollow cathode lamps and air-acetylene flame, using matrix-matched five-point external calibration. Cr was measured as total Cr; no hexavalent speciation was performed. Results are reported in mg/kg dry weight.
Implications
Certification: Pakistan/Sindh sunflower-seed occurrence evidence for Cd, Pb, Cr, Cu, Zn, and Fe at low concentrations. Courses: useful ecological-zone comparison with a clean anthropogenic-vs-geogenic split between Tando jam (Pb/Cd/Cr) and Kotri (Fe/Zn/Cu). App: supports jurisdiction- and region-specific sunflower-seed context for Pakistani sourcing.
Related evidence
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