Characteristics and Mechanisms of Soil Co-Contamination Affecting the Transfer of Cadmium and Arsenic in Peanut (Arachis hypogaea L.)

Overview

Ding and colleagues studied how cadmium and arsenic co-contamination in soil affected transfer into peanut plants, including edible peanut grains. The source is an experimental outdoor pot study, not a market-basket survey, so its peanut-grain values are supply-chain transfer evidence rather than consumer-market occurrence. Arsenic is reported as total/unspecified arsenic (As); no inorganic arsenic speciation is reported.

Key numbers

The experimental soil initially contained total cadmium (Cd) 0.14 mg/kg and total As 11.78 mg/kg. Four soil treatments were used: control, single Cd contamination at 0.6 mg/kg, single As contamination at 40 mg/kg, and Cd-As co-contamination at 0.6 mg/kg Cd + 40 mg/kg As. After twelve months of soil aging, available Cd was 0.29 +- 0.03 mg/kg under Cd-As and 0.21 +- 0.06 mg/kg under Cd alone; available As was 9.76 +- 0.02 mg/kg under Cd-As and 8.65 +- 0.03 mg/kg under As alone.

Table 2 reports Cd and As content in peanut plant parts as mean +- SD, n = 4, in mg/kg. The edible product-relevant grain values are:

The same table reports whole-plant total accumulation amounts of Cd 166 +- 25.0 µg in control, 1126 +- 189 µg under Cd, and 1588 +- 334 µg under Cd-As. Total As accumulation was 49.6 +- 8.11 µg in control, 153 +- 17.3 µg under As, and 215 +- 23.0 µg under Cd-As.

Table 3 reports root-to-grain translocation factors. For Cd, root-grain TF was 0.10 +- 0.03 in control, 0.08 +- 0.00 under Cd, and 0.11 +- 0.01 under Cd-As. For As, root-grain TF was 0.20 +- 0.03 in control, 0.11 +- 0.02 under As, and 0.11 +- 0.01 under Cd-As.

Methods (brief)

The authors used outdoor pots containing 8 kg of red soil and aged the amended soils for about twelve months before sowing peanuts in April 2021. Mature plants were harvested at the end of August and separated into roots, shoots, shells, and grains. Dried plant powder (0.25 g) was digested with 5 mL nitric acid and 3 mL hydrogen peroxide in high-pressure sealed digestion vessels; plant-certified reference materials GSB-23a for Cd and GSB-6a for As were used for quality control, with Cd recovery 95% to 103% and As recovery 94-106%. Available soil Cd and As were measured by ICP-MS after CaCl2 and NH4H2PO4 extraction, respectively.

Implications

This source provides peanut supply-chain evidence showing that Cd-As soil co-contamination increased measured Cd in peanut grains relative to single-Cd treatment, while measured total As in grains was lower under Cd-As co-contamination than under single-As treatment. The values should not be treated as market-distribution concentrations because the study used experimental soil amendments and four replicate pots per treatment.

Update history

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