Geochemical mobilization of arsenic to ground water
This presentation is the property of its rightful owner.
Sponsored Links
1 / 12

Geochemical Mobilization of Arsenic to Ground Water PowerPoint PPT Presentation


  • 144 Views
  • Uploaded on
  • Presentation posted in: General

Sara Baldvins CHEM 4101 December 9, 2011. Geochemical Mobilization of Arsenic to Ground Water. Greatest Mass Poisoning in History. Naturally occurring arsenic (As) contamination in ground water is causing widespread health problems. 35 million in Bangladesh and

Download Presentation

Geochemical Mobilization of Arsenic to Ground Water

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Geochemical mobilization of arsenic to ground water

Sara Baldvins

CHEM 4101

December 9, 2011

Geochemical Mobilization of Arsenic to Ground Water


Greatest mass poisoning in history

Greatest Mass Poisoning in History

  • Naturally occurring arsenic (As) contamination in ground water is causing widespread health problems.

  • 35 million in Bangladesh and

    6 million in Bengal are at risk.

  • As poisoning has also been

    reported in China, Argentina,

    Chile, Mexico, Thailand, and Taiwan.


Analytical problem

Analytical Problem

Hypothesis

  • The speciation of arsenic in soils impacts how mobile the arsenic is which contributes to the high concentrations found in the ground water of some regions.

Problem Summary

  • Certain soils easily mobilize As to the ground water.

  • In these soils certain hydrological, geological, and chemical conditions make arsenic more mobile.


Species separation methods

Species Separation Methods


Sample prep sequential extraction

Sample Prep: Sequential Extraction

Once the soil is ground to the appropriate particle size the reagents will be applied stepwise as follows:


Analytical techniques

Analytical Techniques


Hydride generator

Hydride Generator

The are large interferences when using AAS to detect As so a Hydride Generator must be used.


Atomic absorption spectrometer

Atomic Absorption Spectrometer

For the PerkinElmer PinAAcle 900T:

  • With HG precision ≤ 4.5% for As

  • LOD ≤ 5 ppb

  • LOQ approx. 1 ppb


Xanes

XANES

  • X-ray Absorption Near-Edge Structure

  • The absorption edge corresponding to the liberation of a core electron from an element will exhibit several identifiable features which change depending on the chemical environment of the element being probed. 

  • Answers questions about the oxidation state, coordination, and spin state of the probed element.


Xanes1

XANES


Conclusions

Conclusions

  • Multiple methods are generally required for speciation analysis.

  • Method choice is highly dependant on operating budget since so many samples are needed.

  • HG-AAS is cheap and effective and a good method for bulk analysis.

  • XANES adds validity to the HG-AAS findings by providing an exact picture of the structures in the sample.


References

References

  • Berg, J. A., 2008. Hydrogeology of the Surficial and Buried AquifersRegionalHydrogeological Assessment, RHA-6, part B, Plates 1-6. State of Minnesota, Department of Natural Resources, Division of Waters.

  • Erickson, Melinda L., and Randal J. Barnes. "Glacial Sediment Causing Regional-Scale Elevated Arsenic in Drinking Water." Ground Water 43(2005a): 796-805.

  • Keon, N.E., C.H. Swartz, D.J. Brabander, C. Harvey, and H.F. Hemond. "Validation of an Arsenic Sequential Extraction Method for Evaluating Mobility in Sediments." Environmental Science and Technology. 35(2001): 2778-2784 .

  • Smedley, P. L. and Kinniburgh, D. G., 2002. A review of the source, behaviour and distribution of arsenic in natural waters. Applied Geochemistry 17, 517-568.


  • Login