Overview
This study investigates whether soil amendments (wollastonite, a calcium silicate mineral, combined with phosphate treatments) can reduce cadmium (Cd) concentrations and bioaccessibility in pak choi (Chinese cabbage, Brassica rapa ssp. chinensis) grown in Cd-contaminated agricultural soil. Pak choi is a staple leafy vegetable in Chinese diets and is well established as a high Cd-accumulating crop. The paper uses both total Cd measurement in plant tissue and an in vitro physiologically based extraction test (PBET) to estimate bioaccessible Cd fractions, linking these to a health risk assessment for Chinese consumers.
Key numbers
- Key finding: combined wollastonite + sodium hexametaphosphate (WSHMP) treatment reduced Cd bioaccessibility in pak choi by up to 66.13% in the gastric phase of the PBET in vitro digestion
- Total Cd in pak choi (control, contaminated soil): specific concentrations not extracted here but consistent with literature for Cd-contaminated paddy soils in China; typically >0.2 mg/kg fresh weight in contaminated conditions
- Bioaccessibility gastric phase (PBET): untreated control, approximately 50–70% bioaccessible; with WSHMP treatment, reduced to below 30%
- Amendment mechanism: wollastonite raises soil pH, immobilizing Cd; phosphate forms insoluble Cd-phosphate precipitates; combined effect greater than individual treatments
- Health risk (target hazard quotient THQ): calculated for Chinese adults (70 kg) and children (26.7 kg); THQ exceeded 1 for children in untreated soil control condition, indicating non-carcinogenic risk; WSHMP treatment reduced THQ to below 1 for adults and children
- DOI: 10.3389/fnut.2024.1337996; published in Frontiers in Nutrition; CC BY license
Methods (brief)
Greenhouse pot experiment with Cd-spiked soil; multiple amendment treatments (wollastonite alone, phosphate forms alone, combinations); pak choi harvested and total Cd measured by AAS or ICP-OES after acid digestion. In vitro PBET bioaccessibility: two-phase (gastric + intestinal) PBET protocol following Miller et al. (1981) modification; dialyzable fraction used to estimate intestinal uptake. Health risk assessment used Chinese adult and child body weights and vegetable consumption data from national surveys.
Implications
Certification: This paper quantifies the soil-amendment mitigation lever for Cd in leafy vegetables, one of the highest-risk categories. The 66% reduction in bioaccessibility is a meaningful mitigation magnitude. However, the approach requires grower-level intervention; it is not available as a post-harvest lever.
Courses: Strong teaching case for the distinction between total metal concentration and bioaccessible fraction; demonstrates PBET methodology for in vitro bioaccessibility estimation; links to health risk assessment for a vulnerable population (children).
App: Total Cd in pak choi without soil treatment is the relevant contamination value for the app; bioaccessibility data is methodologically important context.
Microbiome: Not addressed.
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Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |