Contents and Transport of Heavy Metals in Grain Parts of Rice Grown on Cd-Contaminated Soil

Contents and transport of heavy metals in various parts of a grain from the rice grown on Cd-contaminated soil were determined. The contents of Cd, Pb, Cu and Zn in specimens collected from the mining regions in western Fujian were analyzed to study the distribution and transport characteristics of these heavy metals in the parts of the grain. The results showed that although the metal distribution was not affected by the severity of soil pollution, the Cd, Cu or Zn contained in a grain increased in the order of:bran > brown rice > milled rice > hull, and, the Pb in the order of:hull > bran > brown rice > milled rice or bran > hull > milled rice > brown rice. There seemed a significant correlation between the contents and transport of heavy metals in the grains. And, the bran appeared to absorb the heavy metals more readily than other tissues, as it was easier for Cd in the hull to transport to the brown rice grains, or Pb, Cu and Zn in brown rice to the bran; but more difficult for Cd, Pb, Cu and Zn in the bran to move to the milled grains. As a result, the contents of Cd, Pb, Cu and Zn in the grains could be maximally reduced by 70.2%, 95.0%, 97.1% and 81.4%, respectively, through the milling process with the removal of bran, thereby, an improvement for the safety of rice consumption.