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Effect of Plastic Mulching on form Distribution and Translocation of Heavy Metal in Vegetables

Author: LiuQiuYa
Tutor: HuangHaiFeng；LiFeiLi
School: Zhejiang University of Technology
Course: Environmental Engineering
Keywords: Plastic mulching Heavy metal Vegetable Form Translocation
CLC: X173
Type: Master's thesis
Year: 2011
Downloads: 59
Quote: 1
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Abstract


Plastic mulching is a widely used cultivation method in the world, which can shorten the growing season and increase production. Field contrast experiments were conducted and sequential extraction technique was used to study the effect of plastic mulching on form distribution and translocation of heavy metals in vegetables.Results showed that plastic mulching promoted the consumption of soil organic matter, while slowing the surface loss of elements, and the concentration of Fe and Mn in soil used mulched growth was significantly higher than that used un-mulched growth. Compared with un-mulched growth, the concentration of Cd in stems of lettuces and Mn in leaves of lettuces increased 16.9% and 13.8% respectively, while the concentration of Fe in leaves of lettuces decreased 36.6%. Plastic mulching had no impact on the concentration of heavy metals in greengroceries.Sequential extraction technique was used to divide heavy metal of plants into four forms, these forms were ethanol extractable, deionized water extractable, HCl extractable and residual extractable. Writer advanced a conception of evaluation index of heavy activity (α), and heavy metals could be divided into three groups of Cu, Zn; Fe, Cd, Mn and Pb in lettuces and greengroceries according to the activity performance of heavy metals. Cd and Pb were the elements easier to accumulate in lettuces and greengroceries.The results of lettuces and greengroceries showed that the effect of plastic mulching on form distribution and translocation mechanism of heavy metals in vegetables varied with the elements and the types of vegetables. In lettuce systems, compared with un-mulched growth, mulched growth was 24.3% and 34.3% lower in high activity Fe and Zn in stems of lettuces; But plastic mulching increased the activity of Cu, Fe, Cd in leaves of lettuces. In greengrocery systems, compared with un-mulched growth, the relative content of high activity Zn, Cd in roots and high activity Cu, Fe, Mn in stems increased. It indicated that they were easy to translocate from roots and stems into leaves. The activity of Cu in leaves of greengroceries used mulched growth decreased, showing accumulation in leaves. However, the results of heavy metals′forms could not explain the change of heavy metals′total content, even had contradiction, so it indicated that translocation of heavy metals in soil and vegetables was an extremely complex process. But it could be sure that plastic mulching changed form distribution and translocation mechanism of heavy metals, even brought heavy metals accumulate in vegetables, and directly affected the safety quality of vegetables.

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CLC: > Environmental science, safety science > The basic theory for the Environment and Science > Environmental Biology > Environmental botany
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