Study on Mechanism of Arsenic Tolerance in Duckweeds from Lead-Zinc Mine by Synchrotron Radiation X-ray Fluorescenceand X-ray Absorption Near Edge Structure Spectrometry / 分析化学

ABSTRACT

Aquatic plant duckweed can enrich high concentration of arsenic, it is thus used as the representative of phytofiltration.The mechanism of arsenic tolerance in duckweeds has received much concern.In this study, synchrotron radiation X-ray fluorescence (SRXRF) and X-ray absorption near edge structure (XANES) techniques were used to study the micro-distribution and speciation of arsenic in natural As-rich duckweed from lead-zinc mine.Two monolithic duckweeds, FP1 and FP2, were analyzed by micro SRXRF, setting single point scan time and spot size were 5 s, 70 μm×80 μm and 2 s, 100 μm×100 μm respectively.Six points of FP2 were selected and analyzed by micro XANES in energy range of 11.81-11.96 keV.Pressed-pellet duckweed was analyzed by bulk XANES in energy range of 11.67-12.27 keV.The result showed that As(Ⅲ) was the major speciation of duckweed from bulk XANES and micro-XANES data.SRXRF micro analysis showed that arsenic had significant vein distribution in duckweed, and was not spread into the photosynthetic mesophyll within certain concentration, which may reduce the leaf toxicity triggered by arsenic.This vein distribution may play a role in arsenic tolerance in duckweed.