DISTRIBUTION AND BIOACCUMULATION OF RARE EARTH ELEMENTS IN PLANTS UNDER FIELD CASE STUDY CONDITIONS WITH AND WITHOUT RARE EARTH ELEMENT FERTILIZER APPLICATION

摘要

This field case study described the distribution and bioaccumulation of rare earth elements (REEs) in wheat, rice and vegetables grown in Jiangxi, Anhui, Beijing and Heilongjiang provinces, located in southern and northern China with various REE fertilizer application at different levels. The results indicated that REE accumulation trends in different parts of plants followed the order: root>leaf>stem>grain. The concentrations of REEs in roots, leaves and stems were increased remarkably when the REE fertilizers were applied. However, no significant accumulation was found in cereal grains except for that grown in Jiangxi site. A significant accumulation of REEs in the edible parts of vegetables is observed, therefore, no REE fertilizer should be recommended. In the meantime, the exogenous REEs in the fertilized soil were extracted by a three-stage sequential extraction procedure into three fractions: water soluble, exchangeable and carbonate bound (B1), Fe-Mn oxide bound (B2) and organic matter and sulfide bound (B3). Chemical fractions showed that all exogenous REEs were in the fractions B1, B2 and B3, ranging 1.49-13.91, 35.23-70.34 and 19.14-60.78%, respectively, and no exogenous REEs entered the residual form within the field study period. However, the chemical forms of exogenous REEs in the fertilized soil and their bioavailability were dependent on the physico-chemical properties of soil. It seems that REEs in fraction B1 is more easily available by plants.