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
Six bacterial strains were isolated from lead-zinc mine tailings with the age of about 100 years, and their phylogenetic position was determined by the analysis of partial 16S rRNA gene sequence. Three strains belonged to genus Arthrobacter, and were close to A. nicotinovorans and A. histidinolovorans. Other three strains belonged to genus Agromyces, and were close to Ag. mediolanus. All of them were resistant to Pb(NO_(3))_(2), CdCl_(2), ZnSO_(4), CuSO_(4) and CoCl_2. Relatively, minimal inhibitory concentration(MIC)of Zn~(2+) and Co~(2+) of three Arthrobacter strains was significantly higher than that of three Agromyces strains. Additionally, these strains displayed strong adsorption of Pb(NO_(3))_(2), CdCl_(2), ZnSO_(4). Averagely three Arthrobacter strains could adsorb about 400mg of Pb~(2+), 177mg of Cd~(2+) or 80mg of Zn~(2+) per gram of dried cells. Therefore, these strains were important candidates for application in bioremediation of heavy metal-contaminated environment.