Prediction and risk assessment of five heavy metals in maize and peanut: a case study of Guangxi, China

Overview

Gu and colleagues assessed cadmium (Cd), Cu, mercury (Hg), lead (Pb), and Zn in Guangxi soil-crop systems for maize and peanut. The paper includes measured grain/soil relationships, bioaccumulation models, and model-estimated grain concentrations used for adult maize-ingestion risk assessment. Table 5 values are model-estimated grain concentrations rather than raw measured sample distributions; measured grain values in Figure 5 are not numerically extractable from the PDF text layer.

Key numbers

Table 5 reports estimated concentrations of heavy metals in grains, in mg·kg−1:

Additional source-reported grain findings:

• The text states that Cd in all measured maize grains was below 0.1 mg·kg−1 and Pb in maize grains was below 0.2 mg·kg−1.
• The text states that 5.17% of measured peanut-grain Cd and 8.57% of measured peanut-grain Pb exceeded the MHC values of 0.5 and 0.2 mg·kg−1, respectively.
• The text states that Cd, Cu, Hg, Pb, and Zn in maize grains scarcely exceeded MHC maximum values of 0.2 mg·kg−1 for Cd, 0.02 mg·kg−1 for Hg, and 0.2 mg·kg−1 for Pb.
• Model-estimated PCS (percentage of estimated grain concentrations from Table 5 exceeding the MHC, 2012 limits) was 0.01% for Cd, 0.04% for Hg, and 0.04% for Pb in maize grains, and 8.58% for Cd and 22.11% for Pb in peanut grains. These are distinct from the measured-grain exceedance percentages above and derive from the regression-model output rather than direct sample distributions.
• Table 6 maize-grain risk outputs: mean CDI values were Cd 6.78E-05, Cu 1.40E-02, Hg 5.52E-06, Pb 2.45E-04, and Zn 1.69E-01 mg·kg−1·d−1.
• Table 6 mean HQ values were Cd 6.78E-02, Cu 3.49E-01, Hg 1.84E-02, Pb 6.14E-01, and Zn 5.62E-01; the mean HI was 1.61E+00 and maximum HI was 7.72E+00.
• The authors did not assess health risk via peanut-grain consumption because peanut grains were described as oils that were not consumed directly by local residents.

Methods (brief)

The study area covered Binyang County of Nanning City and Xingbin District of Laibin City in Guangxi, China. Sampling included 65 paired maize grain/rhizosphere soil samples, 35 paired peanut grain/rhizosphere soil samples, and 8542 topsoil samples. Soil properties and metal concentrations were analyzed for pH, CaO, total organic carbon, Mn, Cd, Cu, Hg, Pb, and Zn. Grain concentrations of Cd, Cu, Hg, Pb, and Zn were analyzed according to Chinese national food-safety methods. Bioaccumulation factors were calculated as grain concentration divided by paired rhizosphere soil concentration. The paper then developed regression models using soil properties and used those models to estimate grain concentrations and maize-grain CDI/HQ/HI.

Implications

This source contributes supply-chain evidence for Cd, Cu, total Hg, Pb, and Zn in maize and peanut grain grown in Guangxi. It supports a soil-to-grain routing link, with direct relevance to maize/corn grain and peanut rows, but the most complete numeric concentration table is model-estimated and should not be treated as raw sample-level occurrence. Soil-only concentrations are context for the supply-chain pathway and should not be pooled as product concentrations.

Related evidence

• maize
• Corn
• Peanuts
• Other grain products (oat, millet, quinoa, barley)
• Peanuts
• Nuts and Seeds, Other
• Cadmium
• Copper
• Mercury, Total
• Lead
• Zinc

Update history

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