Accumulation, translocation, and assessment of heavy metals in the soil-rice systems near a mine-impacted region

Paddy rice is considered as a main source for human exposure to heavy metal contamination due to its efficient accumulation of heavy metals especially when cultivated in contaminated fields. In the current study, rice grains, straws, roots, and rhizosphere paddy soils were collected from Changsha, a non-ferrous mine-impacted area in China. Heavy metals including Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Ba, and Pb in the samples were determined using ICP-MS. The heavy metal concentrations were found in the ascending order of grain < straw < root < paddy soil except As and Cd. Rice root is a main organ to retain As and Cd through chelation and adsorption. The translocation behaviors of the heavy metals in the soil-rice system were investigated through bioaccumulation factor (BF) and translocation factor (TF). Similar variation tendencies to decrease BFp-r (translocation from paddy soil to root) and TFs-g (translocation from straw to grain) associated with TFr-s (translocation from root to straw) increasing were observed for most of the heavy metals due to heavy metal detoxification and stress tolerance in rice. The potential adverse effects caused by long-term exposure to heavy metals from rice consumption were evaluated via the target hazard quotient. The results indicated potential health risk to human from exposure to Mn, As, and Cd.