Arsenic Contamination and the Chemical Composition of Groundwater in Bangladesh

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Arsenic Contamination and the Chemical
Composition of Groundwater in Bangladesh

• Peter Ravenscroft

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Introduction

• The following slides were prepared by Peter
  Ravenscroft using data collected during the
  Groundwater Studies for Arsenic Contamination in
  Bangladesh project during 1998 and 1999. The
  project was funded by DFID on behalf of the
  Bangladeshs Department of Public Health
  Engineering (DPHE), and carried out Mott
  MacDonald Ltd and the British Geological Survey.
• Anybody downloading these is welcome to use these
  slides for non-commercial purposes provided that
  they acknowledge the source of the information.
• The author accepts no responsibility for
  interpretations or decisions made on the basis of
  these slides. It is the responsibility of each
  individual to verify that the information content
  of each slide meets their needs.
• Peter Ravenscroft previously worked in Bangladesh
  with Mott MacDonald. He is now a Principal
  Hydrogeologist with Arcadis Geraghty Miller
  International Inc. He can be contacted by email
  at pravenscroft_at_arcadisgmi.com.

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Contents

• Arsenic concentration in wells lt150 m deep
• Probability of arsenic exceeding threshold values
• Depth Distribution of Arsenic in Groundwater
• Comparison of arsenic distribution with that of
  other parameters

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Average Arsenic Concentration
The map shows the average (or most probable)
arsenic concentration in the upper 150 m of the
alluvial aquifer system. The geostatistical
surface was interpolated using the ArcView
Spatial Analyst software. The grid was
calculated from the logarithms of arsenic
concentration with the IDW algorithm using 12
nearest neighbours.
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Exceedance of Arsenic Concentration Thresholds
The animated maps that follow show the
probability of arsenic exceeding various
concentration thresholds in wells of any depth.
The maps automatically progress through
thresholds of 10, 50, 200 and 400 ppb.
Click to continue
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Depth Distribution of Arsenic in Groundwater
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Distribution of various hydrochemical parameters
in groundwater compared to the distribution of
arsenicThe geostatistical surface was
interpolated using the ArcView Spatial Analyst
software
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BORON

• Wells lt 150 m Deep

zoom to deep wells in coastal area
Click to continue
Wells gt 150 m Deep
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Bibliography

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  K.A. Hudson-Edwards, R. Mishra, R. Purohit,
  P. Ravenscroft et al. Natural organic matter and
  iron(III) oxides in alluvial sedimentary basins
  their role in releasing arsenic to anoxic
  groundwater the example of West Bengal and its
  worldwide implications. Applied Geochemistry.
• 2003 (in press). P. Ravenscroft, W G Burgess, K M
  Ahmed, M Burren and J Perrin. Arsenic in
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  distribution, field relations, and
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