Synchrotron micro-scale study of trace metal transport and distribution in Spartina alterniflora root system in Yangtze River intertidal zone

Abstract

This study is focused on micro-scale measurement of metal (Ca, Cl, Fe, K, Mn, Cu, Pb, and Zn) distributions in Spartina alterniflora root system. The root samples were collected in the Yangtze River intertidal zone in July 2013. Synchrotron X-ray fluorescence (XRF), computed microtomography (CMT), and X-ray absorption near-edge structure (XANES) techniques, which provide micro-meter scale analytical resolution, were applied to this study. Although it was found that the metals of interest were distributed in both epidermis and vascular tissue with the varying concentrations, the results showed that Fe plaque was mainly distributed in the root epidermis. Other metals (e.g., Cu, Mn, Pb, and Zn) were correlated with Fe in the epidermis possibly due to scavenge by Fe plaque. Relatively high metal concentrations were observed in the root hair tip. This micro-scale investigation provides insights of understanding the metal uptake and spatial distribution as well as the function of Fe plaque governing metal transport in the root system.

Synchrotron X-ray microfluorescence measurement of metal distributions inPhragmites australisroot system in the Yangtze River intertidal zone

“…Ca, Cu and Zn) and non-essential nutrients (e.g. Cr and Pb) (Feng et al, 2015(Feng et al, , 2016Qian et al, 2015). The defensive nature of the plants will not actively uptake and translocate non-essential metal nutrients to the root vascular tissues in a large quantity.…”

“…Usually, the root tip is an active site for oxygen transport and nutrient uptake. For example, relatively higher metal (Ca, Cu, Fe, Mn, Pb and Zn) concentrations in new root tip than those in the main root base were found in Spartina alterniflora collected in the Yangtze River intertidal zone (Feng et al, 2015). Therefore, although the possibility of spatial variation cannot be excluded, the difference between the root tip section and the root basal section may also cause these differences (Feng et al, 2015 Metal concentrations and distributions in the root tip cross-sections of Sample 1-1, Phragmites australis, collected at Site 1.…”

“…In this study, as synchrotron X-ray diffraction (XRD) measurements were not conducted on the samples here, there is no Fe-containing mineral information that can be reported. Nevertheless, synchrotron X-ray microbeam techniques, such as synchrotron X-ray fluorescence (XRF), have important applications in studying metal translocation and accumulation in plants with micrometer-scale resolution (Martin et al, 2001(Martin et al, , 2006Naftel et al, 2001;Sutton et al, 2002;Zimmer et al, 2011;Feng et al, 2013Feng et al, , 2015Feng et al, , 2016Rouff et al, 2013). Unlike conventional wet chemical analyses, the synchrotron-based techniques have demonstrated advantages in sample preparation and measurement.…”

Nanoscale measurement of trace element distributions in Spartina alterniflora root tissue during dormancy

“…Although NanoSIMS has a distinct advantage over synchrotron X-ray techniques in being able to detect light elements, the technique is not effective in studying heavy metals (e.g., Cd, Mn and Zn) due to its low ion yield14. The synchrotron μXRF technique has the advantage of overcoming this drawback of NanoSIMS and other traditional methods (e.g., DCB method) and has been successfully applied to studying metal concentrations and distributions in plants with micrometer scale resolution151617181920212223.…”

“…Unlike conventional wet chemical analyses, the synchrotron-based techniques have demonstrated advantages in sample preparation and measurement. Synchrotron radiation measurement gives detailed views of the accumulation of metals and their chemistry on individual spots or within small areas in the plants including roots, stems, and leaves181920212223. For example, a multilayer Laue lens (MLL)-based scanning hard-X-ray microscope24 has been developed at the Hard X-ray Nanoprobe (HXN) beamline at National Synchrotron Light Source II (NSLS-II).…”