Accumulation, interaction and fractionation of fluoride and cadmium in sierozem and oilseed rape (Brassica napus L.) in northwest China.

Soil fluoride (F) and cadmium (Cd) pollution are of great concern in recently years, due to the fact that considerable amounts of wastewater, gas and residue, containing F and Cd, have been discharged into the environment through ore smelting. Soil F and Cd contamination may result in their interaction in soil and plant, which affects their fractionation distribution in soil and accumulation in oilseed rape. Oilseed rape, which is widely planted and consumed as a popular vegetable in arid and semi-arid land of northwest China, has been believed to a hyperaccumulator for Cd. However, there is limited information about the accumulation, interaction and fractionation of F and Cd in soil-oilseed rape system under F-Cd stresses. A pot-culture experiment, with single (F or Cd) or double elements (F-Cd) being added to soil, was carried out study the accumulation, interaction and fractionation of F and Cd in sierozem and oilseed rape. We found that soil F applications increased the contents of Cd in exchangeable fraction (EX-Cd), the bound to carbonate fraction (CAB-Cd) and the bound to iron and manganese oxides fraction (FMO-Cd) in soil and also increased plant Cd accumulation. Therefore, we suggest that the permitted level of F should be confined within soil quality standards for farmland of China in order to upset the effect of high F concentration on bioavailability of soil Cd. However, soil Cd applications showed negative effects on the content of F in water soluble fraction (Water-F), hence decreased plant F accumulation. A better understanding of the accumulation, interaction and fractionation of F and Cd in sierozem-oilseed rape system are of great importance for environmental protection and for human health. The present study may serve as a basic understanding of the accumulation, interaction and fractionation of F and Cd in sierozem-oilseed rape system, and provide a suggestion for the environmental management.