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Ecological risk assessment on heavy metals in soils: Use of soil diffuse reflectance mid-infrared Fourier-transform spectroscopy

View Article: PubMed Central - PubMed

ABSTRACT

The bioavailability of heavy metals in soil is controlled by their concentrations and soil properties. Diffuse reflectance mid-infrared Fourier-transform spectroscopy (DRIFTS) is capable of detecting specific organic and inorganic bonds in metal complexes and minerals and therefore, has been employed to predict soil composition and heavy metal contents. The present study explored the potential of DRIFTS for estimating soil heavy metal bioavailability. Soil and corresponding wheat grain samples from the Yangtze River Delta region were analyzed by DRIFTS and chemical methods. Statistical regression analyses were conducted to correlate the soil spectral information to the concentrations of Cd, Cr, Cu, Zn, Pb, Ni, Hg and Fe in wheat grains. The principal components in the spectra influencing soil heavy metal bioavailability were identified and used in prediction model construction. The established soil DRIFTS-based prediction models were applied to estimate the heavy metal concentrations in wheat grains in the mid-Yangtze River Delta area. The predicted heavy metal concentrations of wheat grain were highly consistent with the measured levels by chemical analysis, showing a significant correlation (r2 > 0.72) with acceptable root mean square error RMSE. In conclusion, DRIFTS is a promising technique for assessing the bioavailability of soil heavy metals and related ecological risk.

No MeSH data available.


Coefficients of correlation between heavy metal concentrations of wheat grain and reflectance of soil DRIFTS.Reflectances at the 400–2400 cm−1 band were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni, respectively, but not significantly correlated to those of Pb and Cr. “Sensitive band for metal” refers to the band at which soil MIR reflectance shows significant correlation to the metal concentration of wheat grain. The sensitive band ranges are marked with hollow arrows in the first diagram (for Cd, Fe and Ni) and a pink rectangle in the second diagram (for Fe, Cu, Zn and Hg).
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f1: Coefficients of correlation between heavy metal concentrations of wheat grain and reflectance of soil DRIFTS.Reflectances at the 400–2400 cm−1 band were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni, respectively, but not significantly correlated to those of Pb and Cr. “Sensitive band for metal” refers to the band at which soil MIR reflectance shows significant correlation to the metal concentration of wheat grain. The sensitive band ranges are marked with hollow arrows in the first diagram (for Cd, Fe and Ni) and a pink rectangle in the second diagram (for Fe, Cu, Zn and Hg).

Mentions: The correlation coefficients between the concentrations of heavy metals in wheat grain and the reflectance of soil DRIFTS are presented in Fig. 1. The reflectances at the band of 400–2400 cm−1 were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni in wheat grain, respectively. No significant correlations were observed for Pb and Cr. As a result, the sensitive bands of soil spectra for Fe, Cu and Zn in wheat grain were defined at 400–2400 cm−1, whereas at 400–2400 and 3530–3780 cm−1 for Hg, at 400–2980 cm−1 for Cd, and at 400–1920 cm−1 for Ni. The bands in the 400–1300 cm−1 region reflected the Si−O stretching and bending bands as well as and O−H bending bands from soil clay minerals. The bands at 400–600 cm−1 were also associated with the metal-carbon stretching of organometallic compounds19. The 650–1500 cm−1 bands were generally regarded as fingerprints of molecules. The bands at 1700–2130 cm−1 were due to metal−CO or metal−CO−metal19. The bands at 3530–3780 cm−1 may be associated to O−H and Si–O groups of silicates25.


Ecological risk assessment on heavy metals in soils: Use of soil diffuse reflectance mid-infrared Fourier-transform spectroscopy
Coefficients of correlation between heavy metal concentrations of wheat grain and reflectance of soil DRIFTS.Reflectances at the 400–2400 cm−1 band were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni, respectively, but not significantly correlated to those of Pb and Cr. “Sensitive band for metal” refers to the band at which soil MIR reflectance shows significant correlation to the metal concentration of wheat grain. The sensitive band ranges are marked with hollow arrows in the first diagram (for Cd, Fe and Ni) and a pink rectangle in the second diagram (for Fe, Cu, Zn and Hg).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5304163&req=5

f1: Coefficients of correlation between heavy metal concentrations of wheat grain and reflectance of soil DRIFTS.Reflectances at the 400–2400 cm−1 band were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni, respectively, but not significantly correlated to those of Pb and Cr. “Sensitive band for metal” refers to the band at which soil MIR reflectance shows significant correlation to the metal concentration of wheat grain. The sensitive band ranges are marked with hollow arrows in the first diagram (for Cd, Fe and Ni) and a pink rectangle in the second diagram (for Fe, Cu, Zn and Hg).
Mentions: The correlation coefficients between the concentrations of heavy metals in wheat grain and the reflectance of soil DRIFTS are presented in Fig. 1. The reflectances at the band of 400–2400 cm−1 were significantly correlated to the concentrations of Hg, Cu, Zn, Fe, Cd and Ni in wheat grain, respectively. No significant correlations were observed for Pb and Cr. As a result, the sensitive bands of soil spectra for Fe, Cu and Zn in wheat grain were defined at 400–2400 cm−1, whereas at 400–2400 and 3530–3780 cm−1 for Hg, at 400–2980 cm−1 for Cd, and at 400–1920 cm−1 for Ni. The bands in the 400–1300 cm−1 region reflected the Si−O stretching and bending bands as well as and O−H bending bands from soil clay minerals. The bands at 400–600 cm−1 were also associated with the metal-carbon stretching of organometallic compounds19. The 650–1500 cm−1 bands were generally regarded as fingerprints of molecules. The bands at 1700–2130 cm−1 were due to metal−CO or metal−CO−metal19. The bands at 3530–3780 cm−1 may be associated to O−H and Si–O groups of silicates25.

View Article: PubMed Central - PubMed

ABSTRACT

The bioavailability of heavy metals in soil is controlled by their concentrations and soil properties. Diffuse reflectance mid-infrared Fourier-transform spectroscopy (DRIFTS) is capable of detecting specific organic and inorganic bonds in metal complexes and minerals and therefore, has been employed to predict soil composition and heavy metal contents. The present study explored the potential of DRIFTS for estimating soil heavy metal bioavailability. Soil and corresponding wheat grain samples from the Yangtze River Delta region were analyzed by DRIFTS and chemical methods. Statistical regression analyses were conducted to correlate the soil spectral information to the concentrations of Cd, Cr, Cu, Zn, Pb, Ni, Hg and Fe in wheat grains. The principal components in the spectra influencing soil heavy metal bioavailability were identified and used in prediction model construction. The established soil DRIFTS-based prediction models were applied to estimate the heavy metal concentrations in wheat grains in the mid-Yangtze River Delta area. The predicted heavy metal concentrations of wheat grain were highly consistent with the measured levels by chemical analysis, showing a significant correlation (r2 > 0.72) with acceptable root mean square error RMSE. In conclusion, DRIFTS is a promising technique for assessing the bioavailability of soil heavy metals and related ecological risk.

No MeSH data available.