Fu et al. 2025 - Low-accumulation rice and Hg/Cd mitigation

Fu and colleagues tested low-accumulation rice cultivars, soil conditioners, foliar barrier agents, and conditioner application rates in Hg-Cd co-contaminated farmland in Tongren, Guizhou. This source is routeable rice evidence for husked/milled brown rice grain, with treatment-level field summaries for total Hg, Cd, total As, Pb, and total Cr; it should not be mistaken for an HMTc aggregate percentile or a general China rice benchmark.

Key numbers

Site and baseline soil

Table 1 reports three tested farmland setups from the Tongren field experiment. Total Hg and Cd exceeded the China GB15618-2018 agricultural-land limits cited by the source (Hg 1.0 mg/kg, Cd 0.8 mg/kg).

Rice-variety screening

The field experiment screened six rice varieties from Tongren against a CK variety. The CK rice grain had Hg 0.0287 mg/kg and Cd 0.5167 mg/kg, both above the source-cited Chinese food safety limits of Hg ⇐ 0.02 mg/kg and Cd ⇐ 0.2 mg/kg. Replacing the rice variety reduced Hg by 78.05-94.77% and Cd by 97.23-99.32%. The authors identify Longliangyouhuanglizhan (P1) as the lowest-accumulation variety; in the discussion, P1 had Hg below the detection limit of 0.003 mg/kg and Cd 0.0053 mg/kg.

With D1 conditioner added to the variety-screening comparison, Hg decreased by 91.29-94.77% and Cd by 97.75-99.19%. Under D1, all rice varieties except P5 had Hg below the detection limit (0.003 mg/kg). The authors report that after switching to improved varieties, all measured heavy metals stayed below the Chinese food-standard thresholds cited in the paper: Hg 0.02 mg/kg, Cd 0.2 mg/kg, As 0.35 mg/kg, Pb 0.2 mg/kg, and Cr 1.0 mg/kg.

As, Cr, and Pb in rice varieties

Table 7 reports rice-grain As, Cr, and Pb as mg/kg, mean +/- SD. These are total elemental measurements; no inorganic arsenic or chromium speciation is reported.

Soil conditioners and foliar barriers

For Longliangyouhuanglizhan, soil conditioners reduced rice Hg by 64.46-73.52% and Cd by 97.54-98.95% relative to CK. D4 had the largest Hg reduction (73.52%), while Cd reductions were not significantly different among conditioner treatments. Soil conditioners changed As, Pb, and Cr to varying degrees, but the authors state they remained below the source-cited thresholds.

When foliar barrier agents were combined with the four soil conditioners, rice Hg fell below the detection limit of 0.003 mg/kg, and rice Cd was reduced by 98.63-99.59%. Except for Y4, Cd levels in combined treatments were lower than the corresponding single-conditioner treatments.

Available soil Hg after conditioner treatment was D1 0.023 mg/kg, D2 0.023 mg/kg, D3 0.026 mg/kg, D4 0.026 mg/kg, and CK 0.078 mg/kg. Available soil Cd ranged from 1.18 to 1.33 mg/kg after conditioner treatment versus CK 1.14 mg/kg, a slight increase of 3.51-16.67%.

Conditioner-rate screening reduced rice Hg by 60.63-62.72%, total As by 11.49-22.56%, Cd by 98.41-99.42%, and Cr by 34.74-54.06%. Pb changed from a 54.44% reduction to a 60.46% increase depending on application rate, but remained below 0.2 mg/kg. The authors selected 100 kg/mu as the optimal application rate after considering rice traits and soil environment changes.

BCF and health-risk summaries

The CK bioconcentration factors were Hg 0.0023, Cd 0.1717, As 0.0063, Pb 0.0003, and Cr 0.0030. After soil conditioners, BCF reductions were Hg 17.48-62.05%, Cd 97.54-99.06%, and Cr 44.25-74.66%; As changed from -32.80% to +7.45%. Pb BCF in combined soil-conditioner plus foliar-barrier treatments ranged from 0.0006 to 0.0027.

Table 8 reports EDI and RI values for each treatment. The CK rice Cd RI was 1.0205, while all treated Cd RI values were below 1.

Methods (brief)

The one-year field experiment was conducted in May 2023 in Tongren City, Guizhou, China, in Hg-Cd co-contaminated karst farmland. Treatments used three replicate plots for conditioner type, foliar barrier combinations, rice-variety screening, and conditioner-rate screening. Rice plants and corresponding rhizosphere soils were collected at maturity. Soil samples were taken at 0-20 cm using a five-point composite method and kept cold during transport.

Rice samples were washed, dried at 40 degrees C to constant weight, dehusked, and milled. Husked brown rice was digested with HNO3/HClO4 (5:2). Hg was measured by atomic fluorescence spectrometry on an AFS-933 (Jitian Instruments, Beijing, China); As was measured by AFS on an AFS-8220 (Jitian Instruments). Cd, Pb, and Cr were measured by ICP-MS on an ICAP RQ instrument (Thermo Fisher, Waltham, MA, USA). Detection limits were Hg 0.003 mg/kg, Cd 0.002 mg/kg, As 0.002 mg/kg, Pb 0.02 mg/kg, and Cr 0.05 mg/kg. Soil available Hg was extracted with thioglycolic acid-dibasic sodium phosphate and measured by atomic fluorescence spectrometry; available Cd was extracted with DTPA-CaCl2-TEA and measured by ICP-MS on an Avio 200 (PerkinElmer, Waltham, MA, USA).

Implications

Certification: Route as treatment-level brown-rice evidence from a Chinese contaminated-field mitigation experiment. Use for source-level occurrence and mitigation context, not as a standalone benchmark distribution or as an HMTc percentile.

App: Useful for mitigation/sourcing notes around low-accumulation rice cultivars, soil conditioners, foliar barriers, Hg/Cd co-contamination, and Guizhou karst farmland.

Courses: Useful for teaching how cultivar selection, soil chemistry, selenium/silicate conditioners, and foliar barriers change grain metal uptake while preserving basis, species, and treatment context.

Wiki pages this source may touch

• Rice (white, brown, wild — bulk grain)
• Rice
• Agronomic mitigation
• Remediation evidence — drivers and interventions
• Mercury
• Cadmium
• Arsenic
• Lead
• Chromium
• Testing

Verification notes

This page was built from the full PDF, including the abstract, Tables 1-8, Figures 3-8, rice and soil collection methods, digestion and analytical methods, health-risk equations, discussion, conclusions, and data-availability statement. The source reports total Hg, Cd, total As, Pb, and total Cr in husked/milled rice grain; it does not separate inorganic arsenic, methylmercury, or chromium species. Several Hg/Cd treatment results are reported as source-text reductions rather than extractable numeric concentration tables because the underlying Figure 3, Figure 4, and Figure 6 values are plotted graphically in the PDF. D1, D2, D3, D4, and Y1-Y4 are source treatment labels, not product brands. This page omits brand names and uses category-level conditioner labels.

Merge-enhance pass 2026-06-02: trimmed matrices: from five entries to the two actual measurement matrices (paddy-soil, brown-rice-grain); the prior rice-variety-field-trial, soil-conditioner-field-trial, and foliar-barrier-field-trial entries described the experimental design rather than what was measured, and are removed.

Audit-application 2026-06-02 (subagent PROMOTE verdict): added instrument vendor and model identifiers to the Methods section (AFS-933 and AFS-8220 from Jitian Instruments Beijing; ICAP RQ from Thermo Fisher; Avio 200 from PerkinElmer) per CLAUDE.md Part 12 Exception 2 (scientific-method vendor names are not brand-firewall violations and aid reproducibility). Audit also flagged that [[mitigation/agronomic]], [[mitigation/remediation-evidence]], and [[testing/index]] in Wiki-pages-touched fall outside the four-list taxonomy snapshot; verified that all three target pages exist in the live wiki (wiki/mitigation/, wiki/testing/), so the links are valid — the snapshot is the file with limited scope, not the wiki structure.

Page history

The five most recent substantive edits to this page. 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.