Accumulation Of Heavy Metals In Lotus Root (Nelumbo Nucifera) And Investigation Of Their Residues In Soil

Heavy metals such as Cd, Pb and Hg can cause serious contamination of Nelumbo nucifera(Lotus). In this reserch, the concentration of Cd, Pb and Hg in different organs of Nelumbo nucifera (Elian No.5) after supplemented different concentrations of Cd, Pb and Hg to the soil were studied. And physiological changes of Lotus were also measured. On the other hand, Samples of different organs of Lotus and the soil were collected from 36 sampling plots in five provinces of China. The concentrations of heavy metal (Cd, Pb, Hg, As) in the soil and different organs of Lotus were researched and analysised, and making a reasonable pollution evaluation for the heavy metal pollution. The results as follows:1. The concentrations of Cd, Pb and Hg in all tested organs increased when more Cd, Pb and Hg were added to the soil, with different accumulation feature in these organs. Creeping stem can accumulate more Cd and Pb than other ogans. The highest accumulation of Hg was in the leaf with low concentration of Hg supplemented into the soil. But with high concetration of Hg added into the soil, the highest accumulation of Hg was in lotus root. The lotus root can accumulate less heavy metal when the supplemented Cd, Pb and Hg to the soil were lower than 0.6mg/kg,250mg/kg and 1.5mg/kg, respectively. Accumulation was increased rapidly when the supplemented Cd, Pb and Hg to the soil were beyond these concentrations.2. The content of Cd and Pb in different organs of Lotus increases with the concentration of chemical compounds (Pb/Cd), and the accumulative feature of Cd and Pb varies in different organs of Lotus. At low concentration, Cd or Pb mostly accumulates in the leaves, and accumulates in the lotus with high concentration. Moreover, combined pollution makes Cd or Pb accumulate in Lotus more easily than the single pollutant. When the concentration of Pb/Cd. mixed reaches 100+0.2 mg/kg in the soil, the content of Cd, Pb in different organs of Lotus exceeds the specified value of agricultural industry standards (0.05mg/kg,0.2mg/kg).3. Under the Hg and Pb/Cd mixed, lotus root produced a physiological change, thereby affecting the yield and quality of Lotus. Under heavy metal stress, the chlorophyll content decreased, SOD activity increased, MDA levels also increased, while the economic output of the lotus root declined slightly, Vc content and soluble protein first increased and then showed a downward trend, and soluble sugar content also decreased. 4. The investigative results of soil in the 36 sampling plots across 5 provinces showed that Cd concentrations of the soil in 6 sites above 0.3mg/kg (SEQSⅡ). Hg in the soil of 8 sampling plots were above 0.3mg/kg. Pb and As below the Agricultural Standards (250 mg/kg and 0.5mg/kg).5. In 36 sampling sites, the preliminary result showed that the heavy metals mainly accumulated in leaves and lotus root. The Cd, Pb, Hg and As was above the standard determined by AVHS in 6,8,7 and 4 sites.