Overview
Hussain and colleagues tested whether changing the cadmium (Cd):Zn ratio in contaminated soil changed cadmium uptake into edible spinach leaves. This is in-scope mitigation and soil-to-plant pathway evidence: the spinach was grown in deliberately Cd-spiked glasshouse soil, so these values should not be treated as ordinary market spinach occurrence.
Key numbers
The control soil was a sandy clay loam with pH 7.16, ECe 3.25 dS m-1, SAR 1.69 (mmol L-1)1/2, TSS 32.5 mmolc L-1, CaCO3 1.78%, and organic matter 0.72%. Table 1 reports AB-DTPA extractable Cd 0.08 mg kg-1, lead (Pb) 1.25 mg kg-1, and Zn 2.45 mg kg-1; total Cd 1.82 mg kg-1, Pb 13.55 mg kg-1, and Zn 27.5 mg kg-1.
The experiment used four soil treatments: control, Cd-contaminated soil at 3 mg kg-1, Cd-contaminated soil plus 30 mg Zn kg-1 (Cd:Zn 1:10), and Cd-contaminated soil plus 300 mg Zn kg-1 (Cd:Zn 1:100).
Table 2 reports dry matter yield as g pot-1:
| Treatment | Shoot dry weight | Root dry weight |
|---|---|---|
| Control | 5.66a | 0.87a |
| cadmium (Cd) (3 mg kg-1) | 5.50ab (2.83) | 0.83a (4.05) |
| cadmium (Cd):Zn (1:10) | 5.58a (1.36) | 0.85a (2.68) |
| cadmium (Cd):Zn (1:100) | 4.72b (16.6) | 0.60b (31.5) |
Table 3 reports Cd and Zn concentrations in spinach leaves as mg kg-1:
| Treatment | Cd | Zn |
|---|---|---|
| Control | 0.01c | 0.01c |
| cadmium (Cd) (3 mg kg-1) | 3.29a | 0.01c |
| cadmium (Cd):Zn (1:10) | 3.67a | 48.4b |
| cadmium (Cd):Zn (1:100) | 1.96b | 343a |
Table 4 reports Cd and Zn concentrations in spinach roots as mg kg-1:
| Treatment | Cd | Zn |
|---|---|---|
| Control | 0.01c | 0.02c |
| cadmium (Cd) (3 mg kg-1) | 2.96a | 0.01c |
| cadmium (Cd):Zn (1:10) | 3.14a | 51.4b |
| cadmium (Cd):Zn (1:100) | 1.97b | 350a |
Table 5 reports cadmium transfer coefficients:
| Treatment | BCF | BAC | TF |
|---|---|---|---|
| Control | 0.01 | 0.01 | 0.01 |
| cadmium (Cd) (3 mg kg-1) | 0.99 | 1.10 | 1.11 |
| cadmium (Cd):Zn (1:10) | 1.05 | 1.22 | 1.17 |
| cadmium (Cd):Zn (1:100) | 0.66 | 0.65 | 0.99 |
Table 6 reports AB-DTPA extractable Cd and Zn in post-harvest soil as mg kg-1:
| Treatment | Cd | Zn |
|---|---|---|
| Control | 0.09d | 0.14c |
| cadmium (Cd) (3 mg kg-1) | 0.62b | 0.15c |
| cadmium (Cd):Zn (1:10) | 0.45c | 3.64b |
| cadmium (Cd):Zn (1:100) | 0.87a | 57.9a |
The conclusion states that 300 mg Zn kg-1, corresponding to Cd:Zn 1:100, decreased spinach leaf Cd by 46.2% relative to the Cd:Zn 1:10 treatment, while 30 mg Zn kg-1 did not decrease spinach leaf Cd concentrations.
Methods (brief)
The study used uncontaminated soil collected at the Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad. Soil was artificially contaminated with CdCl2.2H2O at 3 mg Cd kg-1 and amended with Zn to produce Cd:Zn ratios of 1:10 and 1:100. Spinach was grown in 10 kg lined pots with three replicates per treatment. Leaves were harvested after eight weeks, washed, air-dried, ground, digested with HNO3 + HClO4 (3:1), and analyzed by atomic absorption spectrophotometry. Soil AB-DTPA extractable metals were also measured by atomic absorption spectrophotometry.
Related evidence
- Soil-to-plant transfer of heavy metals
- Remediation evidence — drivers and interventions
- Spinach
- Spinach
- Cadmium
- Zinc
- Lead
Update history
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