Study On The Relationship Of Se And Heavy Metal And Selenium Uptake Of Crop In Se-rich Red Soil

Selenium (Se) is one of the essential trace elements to human, which plays an important role in human health. The region where selenium is rich (the content of Se>0.4mg/kg) of Fujian account for nearly 20% of the land area of the province, which has the great potential advantages to develop characteristic industry Se resources. A large number of domestic and foreign research shows that selenium-rich soil may be associated with heavy metal enrichment phenomenon, moreover selenium-rich soil may not be able to produce selenium-rich agricultural products, while the research of effective use of Se on selenium-rich soil and the safety production of selenium-rich agricultural products are still insufficient. So, to produce the safety natural selenium rich agricultural products, the soil and crop with different content of Se on selenium-rich area were collected to study the relationship among selenium and heavy metals(Pb、Cd、Cr、Cu、Zn、Ni、La、Ce and Rb), explore the characteristics of Se distribution in Se-rich soil, select the effective selenium extractant, analyze the content of Se and heavy metal in soil-vegetable system and the selenium absorption rules of vegetables and rice on selenium-rich red soil, in order to provide a theoretical basis for the production of selenium rich crops. The main results were as follows:(1) The selenium-rich soil resource in Zhaoan, Datian and Shouning were abundant. The correlations between Se and heavy metals were different with the different place. The selenium and heavy metals had no significant correlation in Zhaoan and Shouning, only a few samples of which went over the National Soil Environmental Standard about heavy metal, but the possibility of compound pollution of soil heavy metals was a little big.The concentration of Se has a significant positive relationship with Cu and Pb in Datian. Only garlic and radish reached the Standards of Se-rich Food in many plant samples which growed on Se-rich soil, so it may not be able to produce Se-rich agricultural products in Se-rich soil. The correlation among heavy metal, and Se content in plant also showed difference in different place. In Zhaoan, the Se and Cu, Rb, Ni showed a significant positive relationship. However, the Se had not significant relationship with heavy metals in plants in Datian, while the Se and Cr had a significant positive relationship in Shouning. Thus,the correlation between selenium and heavy metals in soil is not necessarily related to the crop, which may be related to the physical and chemical properties of soil and crop type..(2) It showed significant positive correlation or extremely significant positive correlation between the content of different forms of selenium and the content of total selenium in soil, the content of different forms of selenium was mainly affected by the content of total selenium in soil.The percentage of organic-sulfide and elemental selenium in all forms of Se were the highest, which occupied 47.09%-55.84%.The residual Se was the Secondly, which occupied 26.04%-34.56%. Exchangeable and carbonate combination of Se were higher than Fe-Mn oxide combination of Se, and the soluble selenium was the lowest, which occupied 2.26%-4.16%. Effective Se of soil extracted by 0.5mol·L-1NaH2PO4 solution was significantly correlated with crop selenium content, and the correlation between effective selenium content and the total selenium content of the soil reached a significant level, which applied to the available selenium extraction of red soil in Fujian.(3) Study on the absorption of selenium and heavy metal on the soil with different contents of selenium of three types of vegetables. Selenium content of water spinach, mustard and garlic in Se-rich soil were higher than those treated with low selenium soil. On Se-rich soil, Se content were 1.6-2.6 times in roots and 1.1-4.5 times in edible parts than those on Se-low soils. The content of selenium in roots (bulb) were higher than that of stems and leaves in three vegetables. The order of Se accumulation in three vegetables showed garlic (0.029-0.143 mg-kg-1> mustard (0.007-0.016 mg·kg-1)> water spinach (0.002～0.007 mg·kg-1). The content of Pb, Cd, Zn, Cu, Cr and Ni in roots of mustard and water spinach were higher than those in stems and leaves,which can be seen through treatments of two kinds of soil, while the content of Pb, Cu, Cr and Ni in garlic showed leaf> bulbs, the content of Cd and Zn showed bulbs> leaf.(4) In the study of Se absorption of 3 kinds of vegetables on soil with different Se content, The selenium content in the upper part of vegetables increased during the whole growing period. Se content in the same part of mustard and spinach and garlic on different soil treatment showed Se2.07> Seo.98>Seo.58>Seo.29, The content of Se in different parts of spinach and mustard showed underground>upper part in all soil treatments, Se content were 4.8～7.05 times in underground part of spinach than upper part, and mustard were 5.78～12.06 times in underground than upper part. The content of garlic showed the order of root>bulb>leaf in Seo.29 and Se0.58 soil treatments, while the Se0.98 and Se2.09 treatments showed bulb>root>leaf, Se content in three different parts of vegetables showed garlic>mustard>spinach. In three types of vegetables, the organic Se content in edible parts were a little high, occupied 73.53% to 84.67% of total, at the same time, with the increasing of soil Se content, the content of organic Se increased. Available Selenium or total selenium content in soil showed significant or extremely significant positive correlation with the content of vegetable, and the effect of Available Selenium and total selenium content of soil on vegetable selenium was significant.(5) The upper part of Se content in rice were increased from tillering stage to maturation stage; the content of Se in different parts of rice showed roots>leaves>stems>shell>grain, on the different Se content soil, Se in each parts of rice showed Se0.98(0.111～0.570 mg·kg-1)>Se0.72(0.059-0.519 mg-kg-1)>Se0.23(0.031～0.345 mg·kg-1),The root absorption index of selenium in rice was decreased with the increasing content of Se in soil, while the secondary transport index increased with the increasing content of Se in soil, and the content of organic Se in grain had the same regulation, the percentage of organic Se increased from 77.69% to 80.73% in total.