Back to Search
Start Over
The development of varying methodologies to speciate and monitor the interactions of selenium and environmental contaminants in plants
- Publication Year :
- 2008
-
Abstract
- There is a multitude of contaminated waste sites worldwide due to anthropogenic activities. When assessing the potential toxicological effects of environmental contaminants, prior concern has dealt with simply quantifying the total concentration of the particular contaminating element. With the increasing awareness of the often significant differences in toxicity between the varying environmental contaminants, elemental speciation and percent distribution must be determined. Conventional remediation efforts have been effective in contaminant removal, but are generally very costly. As a result, phytoremediation, which utilizes plants, has recently gained popularity for removing contaminants from soil. It is also known that a toxic concentration of selenium and arsenic/mercury, if administered simultaneously, produce a nontoxic metabolite in a mammal. The studies in this dissertation utilize novel methodologies to speciate and monitor the interactions of selenium and environmental contaminants, arsenic and mercury, in plants. Eight predominant selenium and arsenic species were simultaneously separated using ion-pairing reversed phase liquid chromatography (IPRP) coupled with inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization ion trap mass spectrometry within 18 minutes and applied to river water, plant extract and urine matrices. The differences metabolic pathways, including location and identity, of selenium and arsenic species were elucidated after single and simultaneous supplementation in the Chlorophytum comosum, spider plant via size exclusion chromatography (SEC) and IPRP coupled to ICPMS. Although total elemental analysis demonstrates a selenium and arsenic antagonism, a compound containing selenium and arsenic was not found in the general aqueous extract of the plant.Increasing the difference between the voltage on the extraction lens and the octopole, plus using a positive voltage between the octopole and quadrupole provided the lowest sulfur detection limits using xenon as the collision reaction cell (CRC) gas in ICPMS. Energy discrimination is the predominant mechanism for removing the 32O2+ interference of 32S+. Optimization parameters were also suggested for a standard solution comprised of 52 elements, including sulfur. Similar detection limits were acquired when comparing Xe to He or H2 CRC gas with a general trend comparable to detection levels for He.Capillary reversed phase chromatography (capRPLC) and SEC were coupled to ICPMS to investigate the metabolic fate of mercury in conjunction with or exclusion of selenium in the Allium fistulosum. The data suggests a possible selenium-mercury association in a proteinaceous macromolecule which is not readily translocated to the aerial plant regions. Data from x-ray fluorescence mapping of a freshly excised root and capRPLC-ICPMS of homogenized root extract suggest the formation of a mercury-selenium species and a similarly structured mercury-sulfur species predominantly residing in the cell wall of the epidermal root tissue. Utilizing x-ray absorption near edge structure analysis, the local environment of mercury and selenium qualitatively coincided with the mercury-selenium species formed in a mammal via a Hg-Se-S(GSH) moiety. The local environment of mercury also coincided with (GS)2Hg.
Details
- Language :
- English
- Database :
- OpenDissertations
- Publication Type :
- Dissertation/ Thesis
- Accession number :
- ddu.oai.etd.ohiolink.edu.ucin1227296686