Worldwide cadmium accumulation in soybean grains and feasibility of food production on contaminated calcareous soils

Sha Zhang, Jing Song*, Longhua Wu, Zheng Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

Elevated toxins in soybeans extensively threaten Asian residents and over one billion vegetarians worldwide. An integrated dataset of toxic trace metal(loid)s especially cadmium (Cd) analysis in soybean grain samples (n = 5217) from 12 countries/regions of origin was compiled for risk analysis. Worldwide grain Cd averaged 0.093 mg kg−1, but mean values varied 16-fold between regions, with South China (0.32 mg kg−1) > Argentina (0.15 mg kg−1) = German (0.13 mg kg−1) > Japan (0.11 mg kg−1) > the United States (0.064 mg kg−1) > Central-North China (0.020–0.60 mg kg−1) ≥ Iran (0.042 mg kg−1) = Brazil (0.023 mg kg−1) = South Korea (0.020 mg kg−1). Regression analysis suggested widespread contamination and acidic soil features significantly contributed the elevated food Cd contamination worldwide. Arsenic (As) and lead (Pb) are also of concern because excessive levels were often observed in grains. Given that soil Cd bioavailability is generally low in alkaline pH ranges, the feasibility of producing safe food from contaminated land was investigated by greenhouse experiments with one low-Cd soybean cultivar grown on 20 contaminated calcareous soils. Equilibrium-based approaches i.e., 0.01 M CaCl2 and in-situ porewater extractions, and diffusion-based diffusive gradients in thin-films technique were used to determine the plant-available fractions of soil metal(loid)s to explain the bioaccumulation variation. The results suggested that soybean grains bioaccumulated mean 0.76 mg Cd kg−1, ranging from 0.16 to 2.1 mg kg−1, whereas As and Pb bioaccumulation was low. Cadmium accumulation was closely correlated with plant-available Cd fractions especially the 0.01 M CaCl2-extractable Cd, but negatively correlated with soil pH. Even in the alkaline pH range, a slight decrease of soil pH would increase grain Cd significantly. Study region and those arable lands that have similar soil conditions are not recommended for growing soybean unless novel remediation strategies are developed.

Original languageEnglish
Article number116153
JournalEnvironmental Pollution
Volume269
DOIs
Publication statusPublished - 15 Jan 2021

Keywords

  • Guizhou plateau
  • Karst area
  • Land policy
  • Liming effect
  • Meta-analysis
  • Surficial contamination

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