ABSTRACT
Moss has high tolerance and accumulating capacity to heavy metal.In this study, the distribution of heavy metal elements in moss sampled from lead-zinc mine was analyzed by X-ray fluorescence spectrometry.The speciation of lead was analyzed by X-ray absorption near-edge spectroscopy.Research showed that the contents of Pb, Zn, Cd and As in the moss of the mining area were extremely high, and their maximum concentration were 1.06 mg/g , 1.23 mg/g, 30.5 μg/g, 13.2 μg/g, respectively.Besides, the shoots especially the new tissue of the moss were the major sites for accumulation and storage of heavy metals.The micro-distribution characteristics varied among Hypnum plumaeforme and Brachytheciumprocumbens, indicating the difference of different species of moss in absorption pathway, accumulation and tolerance mechanisms for heavy metal.Linear combination fitting results indicated that the main lead speciation in moss was lead phosphate (78%) and lead oxide (22%), which suggested that the precipitation of lead phosphate might be the main mechanism of tolerance for moss.
ABSTRACT
To investigate the mechanism of lead biosorption and biotransformation in lead-resistant bacteria in microcosmic scale, synchrotron radiation micro X-ray fluorescence (μ-SRXRF ) and X-ray absorption near edge structure ( XANES) was used to determine the element distribution characteristics and speciation of lead ( Pb) in lead-resistant bacteria strain isolated from farmland soil samples taken from a lead-zinc mine in Lanping county, Yunnan province in China. The isolated species was identified to be Arthrobacter sp. The concentration of Pb biosorpted in lead-resistant bacteria was directly determined byμ-SRXRF, and the results showed that the highest concentration was 5925μg/g and the bioaccumulate factor was 14 . 8 . Speciation of Pb in lead-resistant bacteria B2, LB ( Lysogeny Broth) medium and soil were also presented after using Pb LⅢXANES. Compared with Pb LⅢ XANES peak shape and peak position between standard samples, it was demonstrated that the Pb in lead-resistant bacteria was mainly formed by amorphous forms like PbS (58. 0%), (C17H35COO)2Pb (22. 2%), Pb5(PO4)3Cl (19. 8%) rather than organic Pb speciation which was exist in LB medium. Therefore, the isolated lead-resistant bacteria could biotransform Pb to sulfuric compounds. The biotransformation regular could be of great interest for other investigators as reference in study of bioavailability impact factor of heavy metals.
ABSTRACT
Synchrotron radiation X-ray fluorescence analysis technology (SRXRF) can effectively reduce the detection limit for the determination of heavy metal elements, especially suitable for in situ nondestructive analysis of biological samples with low contents. By corn seed germination test, and combining with SRXRF technology, the effects of Pb on corn seed germination and Pb micro-distribution in the corn seed were studied. X-ray absorption near edge structure (XANES ) technique was used to analyze the Pb chemical speciation in different parts of corn seed. The above experiment was taken to understand the absorption and transformation mechanism of Pb by corn seeds. Results showed that germination rate, bud length and root length decreased with increased Pb contents. The analysis of variance showed that P-value of the germination rate, bud length and root elongation of corn seeds which were exposed to different concentration of Pb were 2. 0×10-3, 1. 4×10-4 and 2. 39×10-8, which were all less than 0. 01, therefore there were highly significant differences during these three indicators and the content of Pb. In addition, the inhibition effect on root growth was greater. SRXRF analysis results showed that Pb was mainly enriched in episperm and embryo, which would inhibit embryonic develop into bud and root. The Pb-LⅢ(13035 eV) XANES spectra of all samples include of root, shoot and the different part of seed were the same, they were the same speciation. Linear combination fitting results indicated that the lead phosphate chloride and lead stearate accounted for 74 . 3 %and 24. 2 % respectively, which suggested that the main Pb speciation of corn was lead phosphate chloride which deposited inside of corn, and a few combined with carboxylic to form the organic lead.