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To investigate the heavy metal concentrations in soil-corn system, 30 pairs of soil (0–20 cm) and corn grain samples were collected from Baiyin City, China, a typical industrial oasis in Loess Plateau. The results indicated that the mean concentrations of Cu, Zn, Cd and Pb in agricultural soils from the Dongdagou and Xidagou stream valleys exceeded the soil background concentrations of Gansu Province, China. Correlation analysis showed that the correlation among the total Cu, Zn, Cd and Pb in soils were significant at P < 0.01. Results showed that only a fraction of Cd and Pb in the corn grain samples exceeded the limits of eight elements in cereals, legume, tubes and its products and the maximum levels of contaminants in foods in China. The spatial distribution pattern of Cd in corn grains was highly similar to that in sampled soils. Correlation analysis revealed that the main source of Zn, Cd and Pb in corn grains was soils. Temporal distribution of heavy metals showed that heavy metal content in soils was still high, and the Cu, Cd, Pb content in corn grains showed a decreasing trend over 20 years. The values of pollution index (PI) and Nemerow integrated pollution index (NIPI) indicated that the heavy metal pollution level was Cd > Zn > Cu > Pb, and Cu, Zn, Cd and Pb belong to safe to heavy pollution. The results of hazard quotient (HQ) indicated that there was no obvious adverse health effect for children and adults. [ABSTRACT FROM AUTHOR]

The in situ immobilization of metal-contaminated sediment, using various amendments, has attracted great attention owing to their cost-effectiveness. The present study investigated the effectiveness of Chinese loess on Cu, Zn, Cd and Pb stabilization by decreasing their bioavailability in contaminated sediment. The loess was mixed with the sediment in doses of 0, 0.5, 1, 2, 5, 10 and 20 kg. Approximately 70 d after loess application, the effectiveness was evaluated using the Tessier sequential extraction procedure and single extractants, including ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), diethylenetriaminepentaacetic acid (DTPA), calcium chloride (CaCl 2 ) and hydrochloric acid (HCl). The results indicated that the loess can effectively transform Cu from the carbonate fraction into the residual fraction when the loess dose was ≥5 kg. However, loess had little effect on Zn, Cd and Pb immobilization. Correlation analysis showed that these four extractants can provide a good indication of the toxicity of Cu, Zn, Cd and Pb in the amended sediment. Additionally, the organic matter content in the amended sediment decreased by 1.4% for CK, 1.6% for L0.5, 1.7% for L1, 1.5% for L2, 1.5% for L5, 1.9% for L10 and 1.9% for L20 (CK: untreated sediment; L0.5 to L20 represent loess doses of 0.5, 1, 2, 5, 10 and 20 kg, respectively) compared to the initial organic matter content in the unamended sediment, which may increase the atmospheric carbon dioxide owing to the degradation of organic matter. [ABSTRACT FROM AUTHOR]