Speciation Characteristics and Ecological Risk Assessment of Heavy Metal Elements in Soils of Typical Industrial City

The development of urban industrialization causes soil heavy metal pollution and other environmental problems. Studies have shown that the damage caused by soil heavy metals to the ecological environment is not only related to the total content, but also depends on the speciation of heavy metals.

To investigate the content characteristics, speciation and risk status of heavy metals in soil of a city in the Hetao Plain.

52 soil samples were collected from different functional areas of the Hetao Plain, heavy metals were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS), atomic fluorescence spectrometry (AFS) and other analytical methods to study the total content and speciation. The ecological risk of soil heavy metals was evaluated using the RAC risk assessment method.

The results showed that the contents of heavy metal elements (except As) in surface soil were higher than the background values in the Hetao Plain, the variation coefficients of Pb, Cr, Mn, Cd and Zn were large and the spatial distribution was not uniform, which were significantly affected by human activities. The heavy metal content in the industrial area exceeded the background value, especially Cd (5.83 times of background value) and Pb (3.58 times of background value). Road heavy metal contents were also significantly higher than the background value, Cd was nearly 4 times the background value. Except for Cd in industrial areas, other heavy metals were mainly in residual fraction. The residual fractions of Cr, Ni, Cu and As were more than 70%. The residual fraction of Cd in each functional region accounted for about 30%. RAC risk assessment results showed that Cd and Pb in industrial areas reached the high-risk level.

The research results provide scientific basis for identifying the potential environmental risks in urban area soil and proposing effective prevention.