基于同步辐射X射线荧光光谱和X射线吸收近边结构谱研究铅锌矿区浮萍中砷的耐受机制

Study on Mechanism of Arsenic Tolerance in Duckweeds from Lead-Zinc Mine by Synchrotron Radiation X-ray Fluorescence and X-ray Absorption Near Edge Structure Spectrometry

水生植物浮萍能够富集高浓度的砷,是植物过滤修复技术的代表,其耐受机理备受关注。本研究利用同步辐射X射线荧光光谱(Synchrotron radiation X-ray fluorescence,SRXRF)和X射线吸收近边结构谱(Xray absorption near edge structure,XANES)技术,开展了铅锌矿区天然富砷浮萍样品中砷元素的微区分布和形态特征研究。微区SRXRF分析了两个单片浮萍样品FP1和FP2,单点扫描时间分别为5 s和2 s,光斑尺寸分别为70μm×80μm和100μm×100μm;对FP2样品选择了6个位置进行了微区XANES单点形态分析,扫描的能量范围为11.81~11.96 keV;整体XANES形态分析是针对压片的浮萍样品,扫描的能量范围为11.67~12.27 keV。结果表明,浮萍样品整体和微区XANES数据均表明砷形态为As(Ⅲ);SRXRF微区分析发现浮萍中砷元素具有显著的叶脉分布特征,在一定浓度范围内,砷并不扩散到进行光合作用的叶肉中,有利于减轻砷对叶片的毒害作用,可能是浮萍耐受砷的一个保护机制。

Aquatic plant duckweed can e nr i c h h ig h c o n c e n t r a t io n o f a r s e n i c , i t i s th u s u s e d a s th e representative of phytofiltration . The mechani sm o f a r s e n i c to l e r a n c e i n d u c k w e e d s h a s r e c e iv e d m u c h concern . In this study , synchrot ron r adi at ion X- r a y f lu o r e s c e n c e （ S RXRF ） a n d X - r a y a b s o r p t io n n e a r e d g e structure （XANES ） techniques wer e us ed to s tu d y th e mi c r o - d i s t r ib u t io n a n d s p e c i a t io n o f a r s e n i c in n a tu r a l As-rich duckweed from lead-zinc mi ne . T wo mo n o l i th ic d u c k we e d s , F P 1 a n d F P 2, w e r e a n a ly z e d b y m ic ro SRXRF , setting single point scan t ime and s p o t s iz e we r e 5 s , 70 滋 mx 80 滋 m a n d 2 s , 100 滋 mx 100 滋 m respectively . Six points of FP 2 wer e s el ect ed a nd a n a ly z e d b y m ic ro X A N E S i n e n e r g y r a n g e o f 11. 81 - 11.96 keV . Pressed-pellet duckweed wa s a na lyz e d b y b u lk X A N E S i n e n e r g y r a n g e o f 11.67-12. 27 k e V . The result showed that As髥 was the major s pec i a t ion o f d u c k we e d f rom b u lk X A N E S a n d m ic r o -X A N E S d a t a . SRXRF micro analysis showed that ar s eni c ha d s ig n i f i c a n t v e in d i s t r ib u t io n i n d u c k we e d , a n d w a s n o t s p r e a d into the photosynthetic mesophyl l wi thin cer t ai n c onc e nt r a t i on , wh ic h m a y r e d u c e th e le a f to x ic i ty t r ig g e r e d b y arsenic . This vein distribution may play a r o le i n a r s e n i c to l e r a n c e i n d u c k we e d .