| This essay studys the main factors that influence the Pb content of the Oolong tea in Fujian province through analysising the soil (the Pb content and the organic matters in soil ; the pH value of the soil ) ;the tail gas of auto mobiles and the alien-soil Pb ; the manufacture and the fuels and the machincary in processing. We expect to find out an effective method that can control and solve the problem of the Pb pllution of the Oolong tea in Fujian province.It is proved that the Pb content of the fresh leaves is in positive propotion of the Pb content of soil ,but in negative propotion of the organic matters content and the pH value of soil . The Pb in soil causes a little Pb increasing in fresh leaves. The content of the available Pb content affects greatly the tea plants to absorb the Pb in soil. The pH value and the organic matters of the soil affect the availability of the Pb in soil .The alien-soil Pb can also change the Pb content of tea .The more the available Pb is, the more searious the pllution is.The reason that the Pb content of the fresh tea leaves nearby road is higher than that of the fresh tea leaves in tea garden is due to the Pb of the tail gas of auto mobiles to cling to the surface of tea leaves. Washing can reduce Pb content of the surface of tea leaves.About 40% of Pb is added to tea in the initial producing process. Different processes cause different extent pollution. South in Fujian: firing> boll rolling>rolling>enzyme-inhibiting;North in Fujian:rolling>firing>enzyme-inhibiting.The enzyme-inhibiting process results in negative increasing. In different fuels coal causes the most extent Pb pollution of tea, the following is wood, and liquefied gas is the last .The machinery that made from the Pb alloy also results in Pb pllution - specially in rolling process and boll rolling process. Additionary , the cloth for boll rolling that is not clean and touches frequently with the producing tea machinery also adds the Pb content to tea. |
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