Studies About The Source Of Lead Coming From And The Absorption And Accumulation Of Lead In Tea

By field investigation, field trial and pot trial, we studied the sources of the lead coming from and the absorption and the accumulation of the lead on the tea plant, found the lead's activity in tea is lower, most of the lead absorbed are fixed in feeding roots, only a little are transported to above ground parts. In the normal statute, the distribution of lead in tea has it's law: the absorption roots>the stems>main root>fresh leaves. When the tea plants were polluted, all the tea plants' apparatus, from bottom to top, especially the absorption roots and main roots ,acted as a buffer and defence, will hold back the lead not transporting into the tea fresh. The lead content in tea fresh is increased when the leaves become older. Also, we found that even we add 100mg/kg into the soil of tea garden, there had no significant negative effects on the biomass, the chlorophyll contents ,therate of photosynthesis, the rate of tea plants' transpiration of leaves and the quality of tea shoots (P>0.05 ) . Maybe the tea plant could endure more lead then other plants, or this harm led by the lead to the tea plants doesn't represent on the growth and tea quality. The lead in the soil-tea plants system could be effectiveness for a long time. The available lead contents in soil and the total leads in tea were hoisted continuously with the time's process. The more the lead wasadded, the more apparent of this hoist. In the soil-tea plants system, the total lead in tea shoots has a significant positive relation with the soil's total lead content in the soil(P<0.05 ), and has a significant positive relation with the available lead content in the soil (P0.01) . Reduce the available lead contents in the soil by change the pH of soil would be a good way to reduce the lead contents in tea. The subsidences in air ,such as the automobile's exhausted gas and the dust ,maybe another main reason to increase the lead's content in tea fresh. The subsidences in air could increase the lead contents in the tea within 150 meters. If the tea shoots were cleaned by water, the lead contents will be cut down to a certian extent. So, controlling the tender of the tea raw material could reduce the lead contents in the made-tea. During the tea processes, the quality of the facilities' material and the state of sanitation will effect on the lead contents in Longjin tea.