| Toxicological effect of heavy metals in organisms is an important subject of environmental toxicology and physiology etc. The rule of metal elements migration and transformation in plants as well as their speciation are of great importance to the restoration of contaminated soil and the comprehensive utilization of plants.This paper systematically studied the distribution and primary speciation, secondary speciation, advanced speciation and chemical speciation of excessive heavy metals (i.e., Pb, Cd, and Cu) in ZHONGJIANG Salvia.After the determination of lead, cadmium, and copper in Salvia roots, stems, and leaves by graphite furnace atomic absorption spectrometry (GFAAS) and flame atomic absorption spectrometry (FAAS), we discussed the enrichment and transfer factor in Salvia plants according to the metal contents in the soil. The contents of Pb, Cd and Cu have the trend of leaves> stems> roots in Salvia plants. The Pb, Cd contents in stems and leaves, Cu content in leaves excessed the standard of GREEN STANDARDS OF MEDICINAL PLANTS AND PREPARATIONS FOR FOREIGN TRADE AND ECONOMY. Among the three elements, Pb posseses the minimum enrichment factor of0.46and maximum transfer factor of23. Salvia plants have super enrichment capabilities to Cd, with the enrichment factor of1.88. In addition, the transfer factors of all these three elements are all over1. We can conclude that Pb, Cd and Cu in Salvia plants can be effectively transferred from roots to the stems and leaves, and the excessive heavy metals can be excreted by defoliation in order to avoid the toxic effect of heavy metal elements in root.Although the content of Pb and Cd in stems and leaves are higher than the standard values, the total amount of heavy metals does not determine their toxic effects in human body. After the decoction of roots, stems, leaves and the filtration by0.45μm filter membrane, the three primary species of Pb, Cd and Cu were separated. The contents of the primary species were determined by GFAAS and FAAS. The total leaching rates of roots, stems, and leaves in Salvia were between20%and28%; the leaching rates of Pb were between43%and46%; the leaching rates of Cd were between44%and59%. For Cu, the leaching rates varied significantly in roots, stems, and leaves, with65.8%in roots,39.3%in stems, and13.4%in stems, respectively. The recoveries of Pb, Cd and Cu total contents in decoctions and residues were in the range of89%-105%, exhibiting the reliability of the data.Using Amberlite XAD-2, Chelex-100chelating resin and strong acid cation exchange resin, the organic and inorganic species, free species and non-free species, stable species and unstable species of Pb, Cu, Cd were isolated from the filtrated solutions.The different species of lead, cadmium, and copper were determined by GFAAS and FAAS. The analytical results indicated that Pb in the whole plant was mainly inorganic, free, and unstable species. In the filtrates, Pb in inorganic species is about56%to82%, in unstable species is about45%to61%, and in free species is about49%to90%. Cd in the whole plant were mainly organic species, free species, and unstable species. In the filtrates, Cd in organic species is about46%to55%, in unstable species is about53%to71%, and in free species is about56%to81%. The Cu species in roots and stems are almost of equal amount, namely,50%. However, Cu in leaves were mainly inorganic species, free species and unstable species. Cu in inorganic species is60.6%, in unstable species is61.6%to61%, and in free species is62.6%. The recoveries of total Pb, Cd, and Cu in different species were in the range of-3.00%-14.6%,-9.30%-14.3%, and7.6%-13.4%, respectively, which were reasonable for speciation analysis.In order to further investigate integrated forms of Pb, Cd and Cu, these three metals in crude polysaccharides and crude proteins from the plant were extracted by distilled water and1mol/L sodium chloride and measured. The results showed that the contents of Pb in crude polysaccharides have the trend of stems>leaves> roots. It is about5%-30%of the total amount. The contents of Cd and Cu in crude polysaccharides have the trend of stems> roots>leaves, which are about8%-16%and3%-18%of the total amount, respectively. Pb content in crude proteins of leaves were about20%of the total amount, which is higher than roots and stems. Cd content in crude proteins of the whole plant were as high as50%of the total amount.After extracting Pb, Cd, and Cu with ethanol, distilled water, sodium chloride, acetic acid, hydrochloric acid etc., their contents were measured. The results revealed that acetic acid extractable Pb and hydrochloric acid extractable Pb are the main forms in roots and stems of salvia miltiorrhiza, which are about40%and30%of the total contents, respectively. Hydrochloric acid extractable Pb and sodium chloride extractable Pb are the main forms in leaves, which are about60%and20%of the total contents, respectively. Sodium chloride extractable Cd are the main forms in whole plant, which are in the range of43%-50%of the total contents. Acetic acid extractable Cd in roots were about32%, while ethanol extractable Cd in stems and leaves were about25%and30%, respectively. Ethanol extractable Cu and distilled water extractable Cu are the main forms in roots, which are about45%and19%of the total amount, respectively. Ethanol extractable Cu and sodium chloride extractable Cu are the main forms in stems, which are about40%and30%of the total amount, respectively. Distilled water extractable Cu and ethanol extractable Cu are the main forms in leaves, which are about35%and28%of the total amount, respectively.In this paper, we comprehensively investigated the rule of Pb, Cd, Cu migration and transformation in plants and their speciation from solubility, stablity, hydrophobicity as well as occurrence forms. The results provide deeper understanding of the speciation of Pb, Cd and Cu in salvia plant. It can also serve as a valuable reference for heavy metal control in salvia plant production and utilization. |
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