Study On Behavior Of Lead In System Of Soil And Tea Plant Under The Condition Of Soil Acidification In Tea Plantation

By field experiment and laboratory experiment, it discussed current status and main problem of soil environmental quality in Jiamgsu tea plantation, effects of simulated acid rain on dissolution and transformation of lead in tea plantation soil, transference of lead in system of soil and tea plant, as well as mechanism of tea plant absorbing lead.In order to find out the foremost problem in Jiangsu tea plantation, we carried a two-year field research and analyzed the soil and tea samples from the typical tea plantation. The results showed that acidification and content of lead exceeding standard were the main problem of soil environmental quality in tea gardens. And the soil fertility was generally enriched, but the soil organic matter content was appreciably low in some gardens. The results also showed that the copper content of tea was up to snuff, while the lead content of tea was appreciably high. Otherwise, there were some weak sides need to be improved in tea plantation managements. Such as fertilizer that used in tea gardens simplified, fertilizing time was usually delayed 1~2 months, organic fertilizer ratherish lacked.Soil was the carrier of lead, and lead in soil would be activable when the soil acidity added. According to the research results, acidification was severe in soil of tea plantation, so the probability that lead transferring from soil to tea plants would increase. For the sake of seeking for the rule of lead behavior in acidity soil, continuous simulated acid rain was used. Through simulated acid rain experiment, the releasing characteristics and the transformation of lead in tea plantation soil with different content of lead were studied. The results showed that the leaching of acid rain induced increase of soil acidity; the lower pH value of acid rain was, the more severe acidification occurred in the soil. The amount of lead released from the soil increased with the decrease in pH value of acid rain and with the augment of lead content in soil. But the curve's characteristics of lead in the filtrate fromthe soil are only affected by pH value of acid rain.Lead in soil was in five forms, and different forms of lead had different quantities. Distribution rule of content of lead in different forms was commonly as follows: residual Pb >exchangeable Pb> organic Pb > Fe-Mn oxide Pb > carbonate Pb. But when lead was added into soil, lead content of each form would change, and content of active forms got more than that of inactive forms. Under this condition, leaching of acid rain would accelerate lead releasing from soil, especially from soil with severe lead pollution. Once pH value of acid rain was lower than 3.5, inactive forms of lead would transform into active forms of lead, so the environment risk was higher in this case.The research aim about lead pollution in tea plantation is how to effectively control lead content of tea. As we all know, content of lead in tea related with transfer of lead in soil and absorbency of tea plant to lead. Through field experiment, the characteristics of horizontal distribution of lead in tea plantation and difference of lead content in each part of tea plant were analyzed. Consequently, the rule of tea plant absorbing lead was obtained. It was shown that contents of lead in soil and each part of tea plant relate with the distance from roads. There was significant negative correlation between lead content in soil or tea and distance from roads, the farther the distance from roads was, the lower was content of lead in tea and soil. It was because that lead sedimentation of the motor epilogue affected content of lead in tea plantations where were near roads. But the relationship between distance and content in tea was less obvious than content in soil. At the same time, there was obvious difference in content of lead in each part of tea plant, the distribution rule was as follows: lateral branch>old leaf>stalk>side root>main root>young leaf, and content of lead in lateral branch was very higher than other part of tea plant. Content of lead in each part of tea plant...