Salem et al. 2024 — PTEs in tomato fruits from remediated and non-remediated contaminated soil, Egypt
This study evaluates whether bioremediation treatments applied to Cd-, Ni-, Cu-, Zn-, and Pb-contaminated agricultural soil and drainage water in El-Rahawy Village, Giza Governorate, Egypt can produce tomato fruits (Solanum lycopersicum var. cerasiforme) that are safe for human consumption. The study combines a greenhouse pot experiment with a field-scale validation and measures both PTE concentrations in harvested tomato fruits and microbiological safety. A health risk assessment (EDI, THQ) is included.
Key numbers
Soil PTE concentrations (El-Rahawy, control CCU, surface 0–30 cm):
- Cd: 6.40 ppm; Pb: 16.00 ppm; Ni: 9.50 ppm; Cu: 13.00 ppm; Zn: 180 ppm (dry weight)
Drainage water PTE concentrations (El-Hode site, untreated):
- Cd: 1.0 ppm; Cu: 0.45 ppm; Mn: 0.93 ppm; Zn: 4.14 ppm
- After DHS (down-flow hanging sponge) bioreactor treatment: Cd reduced to non-detectable; Mn reduced 97.8%
Tomato fruit PTE concentrations (greenhouse scale):
- Cd: below detection limits in all treatments (including untreated control CCU); consistent with EC maximum limit of 0.1 mg/kg for tomato
- Zn: 8.82 mg/kg (CCU control) → 6.18 mg/kg (T3 best treatment); 30% reduction
- Cu: 0.57 mg/kg (CCU) → 0.17 mg/kg (T3); 70% reduction
- Ni: 1.00 mg/kg (CCU) → 0.25 mg/kg (T3); 75% reduction
Field experiment trends: same direction as greenhouse; T3 achieved 43% Zn, 15% Cu, and 80% Ni reduction vs. CCU
THQ: below 1.0 for all metals under all treatments, indicating no significant non-carcinogenic risk from PTE content in tomato fruits at Egyptian adult consumption rates
Analytical method: AAS (Atomic Absorption Spectrophotometer ICE 3500, Thermo); microwave-assisted acid digestion (HNO3/H2O2)
Bioremediation treatments:
- T1: bentonite + rock phosphate + elemental sulfur + phosphate-dissolving bacteria + Thiobacillus sp., irrigated with untreated drainage water
- T3 (best): mixture of ball clay, Aswan clay, bentonite, kaolinite + phosphate-dissolving bacteria + Thiobacillus sp., irrigated with DHS-remediated drainage water
Methods (brief)
Split-plot greenhouse experiment (3 replicates) and field-scale experiment at El-Rahawy Village, Giza, Egypt; tomato seedlings grown September 2021; treatments applied to soil and irrigation water; mature tomato fruits harvested and analyzed for PTEs by AAS and microbiological safety by standard plate count and selective media (Salmonella, E. coli, Staphylococcus). DHS bioreactor for drainage water remediation: down-flow hanging sponge with polyurethane foam carrier; continuous flow mode.
Implications
Certification: This paper documents that tomato grown in heavily contaminated Egyptian agricultural soil (soil Cd 6.4 ppm, which is well above background) still produces fruit with Cd below detection limits and Ni/Cu within acceptable ranges when grown under contaminated conditions, demonstrating that vegetable-fruit matrices (non-leafy) accumulate far less Cd than leafy vegetables. The THQ < 1 finding supports that tomato fruit Pb, Cd, and Ni pose low immediate health risk for Egyptian adult consumers even from contaminated soils, consistent with YANG et al. accumulation hierarchy (leafy vegetables > solanaceous > root > legume > cucurbit).
Courses: Strong practical example of combined soil + irrigation-water remediation; illustrates how agricultural drainage water is a major PTE contamination pathway in Egypt; demonstrates DHS bioreactor effectiveness.
App: Tomato ingredient contamination profile: Cd below detection, Ni ~1.0 mg/kg in worst-case contaminated Egyptian conditions, Zn ~8.8 mg/kg. These are not typical global baseline values; they represent a contaminated-soil production scenario.
Microbiome: Not addressed.