Study On The Bio-availability Of Selenium And The Influence Of Trace Elements In Different Parent Material Soils In The Selenium Rich Tea Plantations

The selenium is a necessary trace element to maintain the normal life functions. When people are lack of selenium, they will suffer from the drop of body’s immune ability, clinical medical proved that more than40diseases are associated with selenium deficiency. In addition, China’s widespread diseases kaschin-beck and keshan have also proved were related with the lack of selenium in the local environment conditions.There are more than40countries and regions are lack of selenium in the world, and include our country. In China,72%of the counties belong to the low selenium or deficiency selenium regions, and they distribute in22provinces in China, about a total of seven hundred millions people living in low or lack selenium areas, about100millions people are lack of selenium in their diets, they are in a state of deficiency selenium.Selenium is an essential trace element to human health, and we living in a serious lack of selenium area, a large number of populations’daily intake of selenium are deficiency. So how to improve this status has became a significant subject.International environmental and security academics consider that the most safety way to supplement the nutrient elements is the food, and domestic scientists got the same conclusion. Most of the selenium in food is organic selenium, is easier to be absorbed by bodies, long time to eat won’t cause selenium poisoning. Tea is the most extensive daily drink in China, there is a large drinking population. Tea tree is natural Se-rich plant species, the organic Se occupies80%of the total Se content in tea leaves, and the organic Se can be absorbed easier by human bodies, tea is an ideal natural source of selenium. Therefore, tea could be used as a safe and effective means to improve the selenium deficiency in China, especially the selenium-rich tea.The plants absorb the trace elements from soil is selective, only certain part, it is bio-availability part. In recent years, with the research deepening, the bio-availability problem is becoming more and more important. Selenium as an important essential trace element, the bio-availability problems influence the health of the human race, is very necessary to do further research.Selenium followed the law of "rock�'soil�'plant" migration process. Rock is the main source of selenium of the ecosystem, soil is the direct source of selenium of ecosystem. The parent material and soil types are the key factors that influence the selenium contents in the soils and plants.This article use the perspective of environmental geochemistry, analyzed the contents of selenium in different parent material soils and tea leaves, tested the contents of trace elements in soil samples and tea leaves samples, using different extraction agents to leach the bio-availability selenium from soil samples, hope to find out a extracting agent which can accurately reflect all kinds of soils’bio-availability selenium as the best extracting agent for the future research. The conclusions as follows:1、The average contents of selenium in the soil in Wanyuan is higher than the background values in China and Sichuan Province, and the most contents are in Se-rich ranges, therefore, Wanyuan belong to the Se-rich area.2、The content of selenium in soil is mainly affected by the parent material,the selenium contents in four types soils in the order:carbonaceous slate soil> shale soil> Triassic sandstone soil> Jurassic sandstone soil.3、The selenium contents in tea leaves in the order:Triassic sandstone soil> shale soil> carbonaceous slate soil> Jurassic sandstone soil, this order inconsistent with the order of selenium content in the soil, and the correlation about the selenium content between tea and soil is low, therefore, the selenium content of tea is not controlled by the total selenium content in soil.4、The Cd, Cr, Zn, Mn, V contents in soil are higher than the background values but under the secondary soil standard limit, no risk of the environment pollution; Low toxic element contents in tea leaves, the tea belong to a high quality. The concentration coefficient of Mn and Sr with tea leaves is very high, especially element Mn, tea belongs to the strong rich Mn plants.5、Analysis the existing forms of selenium in soils, the residue state has the highest content, more than50%and even up to80%, it can proved that most of selenium in soil is not biological availability; The weak acid extract state in the order:Triassic sandstone soil> Jurassic sandstone soil> shale soil> carbonaceous slate soil, this part has been confirm to be the biological availability, and the order is consistent with the order of selenium content in tea leaves, it shows that this part accounts for a large proportion of the total absorbed selenium by tea.6、The biological availability of selenium in four types soil inn the order:Triassic sandstone soil>Jurassic sandstone soil>shale soil>carbonaceous slate soil, it is in accordance with the the weak acid extraction state, this could indirect proof conclusion5.7、The best extraction agents for the extracting of biological availability of selenium from four type soils respectively are:0.1mol/L KH2PO4for carbonaceous slates soil,0.5mol/L NaHC03for Jurassic and Permian sandstone soils,0.43mol/L HAC for shale soil.8、Add fertilizer which containing with strontium and vanadium in the carbonaceous slates and sandstone soils can contribute to the absorption of selenium by tea leaves; In shale soil, strontium, vanadium and rare earth elements could contribute to the selenium contents in tea leaves, but the effect of rare earth elements is stronger.