FACTORS AFFECTING THE BIOAVAILABILITY OF HEAVY METALS IN SOIL-CORN SYSTEMS IN THE TAIHANG MOUNTAINS FRONT PLAIN

摘要

Based on a multi-target geochemical investigation of Hebei Province, 219 representative pairs of corn seed and root soil samples were selected from agricultural soils on the Taihang Mountains1 front plain. We analyzed the effective distribution of heavy metals in root soil and the bioavailability of and factors influencing heavy metals in corn seeds. The results showed that Cd had the highest ratio of available and potential effective states, indicating that it had the highest potential for migration, transformation, and harm. Its migration coefficient was far greater than of the Pb, Cr, Hg, and As coefficients, showing potential for migration and harm to the environment. The residual states and total amounts of As, Hg, Cd, and Cr had significant correlations, indicating that the total amount of each heavy metal was an important factor affecting the heavy metal form in root soil. Soil pH increased the proportion of Cd, Cr, and Pb7s ion-exchange state, which directly led to the increase of Cd, Cr, and Pb in crops. The soil was weakly alkaline, which can effectively reduce the absorption of Cd, Cr, and Pb in crops. Soil organic carbon affected the accumulation of heavy metals. The ion-exchange state of As had a positive correlation with organic carbon, unlike other heavy metals. The ratio of Cr, Cd, As, Hg, and Pb's water- soluble and ion-exchangeable states to the total amount of each heavy metal decreased slightly with the increase in the clay content. This shows that the clay surface absorbed some heavy metal ions, which can influence the geochemical behavior of heavy metals.