叶甜菜对土壤中汞的吸收分配及土壤汞安全阈值研究

为保障土壤汞污染地区叶甜菜的安全生产,通过土壤模拟试验方法,研究了叶甜菜对土壤汞的吸收、分配及其安全生产的土壤汞质量比临界值。结果表明:1)土壤中有效态汞占全汞的比例很低,各处理均在2.5%以下;2)叶甜菜生长对土壤汞污染有较强抗性,但不同器官间存在差异;3)叶甜菜根系对土壤中汞的吸收能力较强,但向地上部的转运能力较弱,根系对土壤汞富集系数为5.16%~9.30%,地上部器官富集系数仅0.16%~1.64%,各汞处理为0.16%~0.48%;4)叶甜菜根系汞质量比与土壤汞质量比间的关系为乘幂关系,而茎和叶柄、叶片汞质量比与土壤汞质量比间的关系为直线关系;5)叶甜菜根系、茎和叶柄、叶片中汞质量比符合国家标准(10μg/kg,GB 2762—2012)的土壤汞质量比安全阈值分别为0.21 mg/kg、5.12mg/kg、3.23 mg/kg。

On the uptake and translocation of mercury in Beta vulgaris and the safety thresholds of soil mercury content

In order to guarantee the safety production of Beta vulgaris in the Hg-contaminated soil fields,the paper has been engaged in a pot soil growing experiment under the different Hg content levels,i.e.,0.14 mg/kg (the control),1.5 mg/kg,5 mg/kg,10 mg/kg and 15 mg/kg.At the same time,it has also traced the changes of the soil' s total Hg content and its available Hg mass ratio,the effects of the soil' s Hg stress on the biomass of the different organs of the vegetable,through the uptake,translocation and accumulation of Hg in the plants,as well as an analysis of the critical ratios of the soil Hg content for the safety production.The results of its experimental study show that,(1) The ratios of the available Hg content to the total Hg are very low,which account for merely less than 2.5％ under all the soil Hg levels.Moreover,the ratio may turn to be minor later when Beta vulgaris was planted than it was before;(2) The resistance of Beta vulgaris against the soil Hg stress in the plant growth has been found fairly strong,though different organs of the plant tend to be somewhat discrepant.As compared to the control group,the biomass of the above ground parts of the organs (stem and leaf stalk,and the leaf blade) tends to increase under the soil Hg levels being ≤5 mg/kg,but tends to decrease under the condition when the soil' s Hg level is ≥ 10 mg/kg.Thus,the biomass of the roots tends to get reduced with all the soil' s Hg treatments (1.5-15 mg/kg);(3) Though the uptake of Hg is relatively strong by Beta vulgari of the roots,it tends to be rather weak in the transfer of Hg from the part of roots to the above ground surface organs,whose content concentration factors (CFs) in the roots turn to be 5.16％-9.30％,whereas the CFs in the up-ground organs prove to be 0.16％-1.66％ with only 0.16％-0.48％ be ing for the soil' s Hg treatment;(4) There exist somewhat energy relationship between the root Hg mass ratio and that of the soil Hg mass,which should be in the linear relationship between the Hg mass ratio of the above ground organs and that of the underground part;(5) It is necessary of the great need to control the Hg mass ratio of its different organs of Beta vulgari within its maximal limit allowance (e.g.10 pg/kg) in accordance with the Chinese standard (GB 2762-2012).Thus,from what is said above,the soil Hg mass ratios ought to be controlled below 0.21 mg/kg for the root,5.12 mg/kg for the stem and the leaf stalk,with 3.23 mg/kg being for the leaf blade.