Contents of pollutant and nutrient elements in rice and wheat grown on the neighboring fields

Because of recent agricultural policy to suppress rice production, a rather rare situation occurred in one prefecture in Japan that rice and winter wheat were grown in fields neighboring each other, rice being grown from May to October, and wheat from November to June of the next year. Grains of such rice and wheat were analyzed for cadmium (Cd) and lead (Pb) by atomic absorption spectrometry, and eight nutrient minerals by inductively coupled plasma emission spectrometry. Concentrations of nutrient minerals were higher in wheat grains than in unpolished rice grains (without husk), and similar trends were observed also for Cd and Pb. Flour obtained by milling of the wheat grains had significantly less Cd and nutrient minerals than the mother grains, and such reduction was also observed by treatment of unpolished rice to polished grain. Pb concentration was also reduced by the polishing of rice. Pb in wheat flour appeared to be higher than that in whole grain. Comparisons between the final edible forms of the two cereals showed that K and Cu were higher in polished rice than in wheat flour and that such may also be the case for Cd, whereas the reverse was the case for Ca and Fe, and possibly for Pb.