Rice seedlings exposed to trivalent chromium retained chromium in roots and surface iron plaques. Synchrotron speciation distinguished ferrihydrite-bound from organic-associated Cr(III), with different proportions in root tips and mature zones; the study concerns an upstream uptake mechanism rather than grain contamination.
Key numbers
| Treatment | Compartment | Cr mean±SE mg/kg | Fe mean±SE mg/kg | Cr distribution % | Fe distribution % |
|---|---|---|---|---|---|
| Fe80-CK | iron-plaque-DCB | 0 ± 0 | 41.26 ± 2.8 | — | 90.7 |
| Fe80-CK | root | 0 ± 0 | 1.95 ± 0.43 | — | 4.3 |
| Fe80-CK | shoot | 0 ± 0 | 0.4 ± 0.04 | — | 5.0 |
| Fe80-Cr(III) | iron-plaque-DCB | 1.89 ± 0.14 | 62.73 ± 2.6 | 37.3 | 88.7 |
| Fe80-Cr(III) | root | 2.66 ± 0.14 | 3.87 ± 0.65 | 53 | 5.3 |
| Fe80-Cr(III) | shoot | 0.04 ± 0 | 0.34 ± 0.01 | 9.7 | 6 |
Figure 4 c ferrihydrite-bound/organic-associated Cr(III): root-tip spot 2 42/58%, tip spot 1 36/64%, mature spot 2 87/13%, mature spot 1 83/17%. Table 2 isotope results and Table 1 LSD values are preserved separately.
Root and shoot tissues were oven-dried for analysis. DCB plaque extraction begins with fresh roots; its concentration denominator is not expressly defined and remains basis-not-reported.
Methods (brief)
Rice grown under controlled conditions, iron plaque induced by an 80 mg/L ferrous treatment for 24 h and exposed to a 1 mg/L CrCl 3·6 H 2 O-labelled treatment for 3 days. Nominal salt-versus-element wording is retained as a method ambiguity. DCB plaque extraction; dried tissues nitric-acid digested and analyzed by ICP-OES with blanks/reference material. µ-XRF, µ-XANES and 13 C NanoSIMS support spatial/speciation interpretation; a 16-day dissolution experiment samples days 1, 3, 7, 10, 16.
Implications
Supports chromium uptake and iron-plaque pathway evidence. Hotspot spectral fractions are not bulk rice-grain species fractions and cannot substitute for a Cr(VI) food result. Release of plaque-bound chromium (Cr) during dissolution qualifies any assumption of permanent sequestration.
Evidence Fitness: EF-2 for controlled tissue concentrations and hotspot speciation; pathway context only for consumer products. Source-reported distribution calculations require qualification.
Related evidence
- Soil-to-plant transfer of heavy metals
- Remediation evidence — drivers and interventions
- Chromium
- Iron
Update history
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