The Accumulation And Distribution Characteristics Of Pb、Cu And Cd From Soil By Tea Plant

The tea plant absorbs heavy metals such as lead(Pb), copper(Cu), Cadmium(Cd) from the environment by roots and leaves. Then the heavy metals are transported,accumulated and distributed in all the parts of tea plants. Finally, the heavy metals go into the leaves of tea plants and the tea product, which influences the quality safety of tea. There are many researches about the absorption and accumulation character of Pb, Cu and Cd in tea plants by the method of soil plant and hydroponics. The researches are on the transportation, accumulation and distribution character of heavy metals. On the other hand, many investigations about heavy metals in tea plant and soil from field have been carried out.All these researches provide a theory foundation for further investigations. The tea garden is a complex environment because of the agricultural inputs. Tea plants have a strong ability of toleration and resistance from heavy metals. The residual heavy metals in tea relates to environment of tea garden, plant, production, storage and transport. The key point of the management of tea quality safety is "precaution from source" and "trace the whole process", especially the source of the heavy metals in tea planting and environment, and the relation among the accumulation character of tea plant, the environment and the tea plant are focused.The paper chose Pb, Cu and Cd which are hazardous for the quality safety of tea as subject, sampled from representative tea garden, and systematically investigated the content of Pb, Cu and Cd. On the base, the paper investigated the two closely related aspects of tea plant and soil.The paper was conducted by the science of tea cultivation, soil science, soil chemistry and tea physiology and such science theory, took the method of instrumental analysis, tea testing and statistical analysis. By the FAAS way, the paper systematically investigated the content of Pb, Cu and Cd in the parts of tea plant and the soil the tea planted in. Further more, the paper investigated the accumulation character of tea plant cultivated in field, the heavy metal content of tea garden soil, the relation between heavy metals in tea plant and in soil. Therefore, the paper can provide a theory foundation for the building of green (organic) tea garden, and the control of heavy metal pollution of tea from the source.The results are as follows:(1) The content of Pb,Cu and Cd in the leaves and stems of the new shoots are significantly different.Pb:Fleaf=112.72> F[12,26]=2.96, p<0.01, Fstem=58.52>F[12,26]=2.96,p<0.01 Cu:Fleaf=25.44>F[12,38]=3.63,p<0.01,Fstem=46.53>F[12,38]=3.63,p<0.01Cd:Fleaf=30.42>F[12,38]3.63, p<0.01, Fstem=27.01>F[12,38]=3.63,p<0.01The content of Pb and Cu in leaves and stems decreased with the increase of order on the shoots, while the Cd content decreased. The content of heavy metal in shoots of different seasons sort as:Pb spring shoot> autumn shoot> summer shoot; Cu autumn shoot> summer shoot> spring shoot; Cd summer shoot> autumn shoot> spring shoot. The content of Pb, Cu and Cd in different tea varieties showed a significant difference.(2) Both Pb and Cu distributed in vigorous new shoot and new root of young tea plants, while Cd mostly in root. In old tea plants, The order of Pb content sorts as: absorbing root> new shoot> old leaf> lateral root> product stem> main root> main stem> backbone stem (F=60.41>F[7,23]=3.35, p<0.01), The order of Pb distribution rate sorts as:new shoot> lateral root>old leaf> absorbing root> product stem> backbone stem> main root> main stem; The order of Cu content sorts as:absorbing root> new shoot> lateral root>old leaf> main root> product stem> backbone stem> main stem(F=24.83>F[4,40]=3.83,p<0.01); The order of Cu distribution sorts as:new shoot> lateral root>old leaf> absorbing root> product stem> backbone stem> main root> main stem; The order of Cd content sorts as:absorbing root> lateral root> new shoot, old leaf, product stem> main root> backbone stem, main stem (F=586.98>F[7,23]=3.35, p<0.01); The order of Cd distribution sorts as:absorbing root> lateral root> new shoot, old leaf, product stem> main root> backbone stem, main stem.Pb, Cu and Cd content in tea plants of different tea gardens are significantly different.FPb=12.45>F[4,4o]=3.83,p<O.OlFCu=3.41>F[10,40]=2.78,p<0.01FCd=3.82>F[10,40]=2.78,p<0.01The content decreases with the increase of the distance between the tea garden with the high way.(3) The content of available Pb,Cu,Cd and total Pb,Cu,Cd in different tea garden are significantly different.Available Pb(F=14.41>F [10,10]=4.85,p<0.01),Total Pb(F=12.45> F[10,10]=4.85,p<0.01)Available Cu (F=13.84>F[10,10]=4.85,p<0.0l), Total Cu(F=50.81>F[10,10]=4.85,p<0.01)Available Cd(F=106.61>F[10,10]=4.85,p<0.01),TotalCd(F=95.06>F[10,10=4.85,p<0.01)In different tea garden are significantly different. In all the tea gardens, the content of the heavy metals in topsoil are higher than in the subsoil.(4) There is no obvious relation between Pb and Cd content in tea plant and Pb and Cd content in soil. While Cu content in product stems and backbone stems are negatively correlated with Cu content in soil (rproduct stem.=-0.7841(p<0.01, rbackbone stem=-0.7670,(p<0.01).Cu content in product stem negatively correlated with available Cu content in soil.The accumulation coefficient of the three heavy metals in different parts of tea plant are significantly different, The order of Pb lateral root> main root>leaf>product stem> backbone stem(F=4.88>F[4,40]=3.83,p<0.01); The order of Cu lateral root>leaf, main root> product stem> backbone stem (F=12.75>F [4,40]=3.83,p<0.01); The order of Cd lateral root> product stem> leaf> main root> backbone stem (F=11.38>F[4,40]=3.83,p<0.01)The above results aim to provide a theory foundation for the building of green (organic) tea garden, and the control of heavy metal pollution of tea from the source.