The transfer of fluorine in the soil–wheat system and the principal source of fluorine in wheat under actual field conditions

Very few studies of F in soil and wheat grain, straw and root under actual field conditions have been reported. In order to study F concentration (contamination) in wheat and its relationship to soil F and other elements, the present study collected and analyzed 150 pairs of topsoil and wheat samples (root, straw and grain) from the Yangtze River delta region, China. Compared with the Chinese maximum permissible concentration in wheat grain for F, 36.7% of wheat grain samples in the present study area are contaminated with F. The concentrations of F in different wheat tissues generally decreased in the order of root > straw > grain. Fluorine in wheat tissues showed significant correlations with Fe, S, P and heavy metals. The soil total F and water soluble F concentrations in the present study area range from 0.29 to 0.79 g kg−1 and 2.28 to 30.11 μg g−1, respectively. The soil total F and water soluble F exhibits no significant correlations with wheat root F or grain F. It is inferred that the major source of F in wheat is not from the soil, whereas F in wheat grain may mainly derive from the atmosphere.

► The F concentrations of different wheat tissues decrease in the order of root > straw > grain. ► Fluorine in wheat tissues shows significant correlations with Fe, S, P and heavy metals. ► Soil total F and water soluble F show no significant correlations with wheat F. ► The major source of F in wheat is not the soil but the atmosphere.