Uptake and Translocation of Some Heavy Metals by Rice Crop (Oryza sativa) in Paddy Soils

Accumulation of heavy metals in edible crops is amongst major international concerns today. While consuming Lenjan variety of rice is very popular in Iran, limited evidence exists on its safety. Amid increasing public concern about the safety of locally grown and imported rice in the market, a field study was carried out to investigate uptake and translocation of Cd, Pb, Ni, and Zn by a local variety of rice crop (Oryza sativa) exposed to contaminated water. At harvest time and in paddy fields, 41 soil and plant samples were collected from four locations of Lenjan, central Iran; irrigated from Zayandeh Rood River. In the laboratory, different parts of the plant were milled, digested via acid digestion method, and then analysed for Cd, Pb, Ni and Zn using atomic absorption spectrophotometry. The results showed that average concentrations of Cd, Pb, Ni and Zn were 1.07, 17.22, 1.73 and 13.75 mg/kg in the plant’s stem; and 1.27, 12.32, 1.099 and 19.39 mg/kg in its grain, respectively. In general, both in the plant’s stem and grain, the Cd and Pb concentrations were much higher than the FAO/WHO standard and labelled as harmful for consumers. Moreover, among the studied heavy metals, Ni transported very weakly, while Cd and Zn conveyed most easily into the plant’s stem and grain. Of course, Pb was the least mobile metal. However, it had highly accumulated in the plant’s stem and grain.