Arsenic Contamination and the Chemical Composition of

Groundwater in Bangladesh

Peter Ravenscroft

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 Bangladesh’s 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@arcadisgmi.com.

Contents

• Arsenic concentration in wells <150 m deep

• Probability of arsenic exceeding threshold values

• Depth Distribution of Arsenic in Groundwater

• Comparison of arsenic distribution with that of other parameters

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.

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.

Exceedance of Arsenic Concentration Thresholds

Click to continue

Depth Distribution of Arsenic in Groundwater

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BGD Standard (50 µg/l)

WHO Guideline (10 µg/l)

HTW 's (potable)

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D TW 's (irrigation)

D eep HTW 's (potable)

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Depth (m. bgl)

Distribution of various hydrochemical parameters in groundwater compared to the distribution of arsenic

The geostatistical surface was interpolated using the ArcView Spatial Analyst® software

Click to continue

Wells < 150 m Deep

Wells > 150 m Deep

BORON

zoom to deep wells in coastal area

Bibliography

2003 (in press). J.M. McArthur D.M. Banerjee, 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 groundwater of the Bengal Basin, Bangladesh: distribution, field relations, and hydrogeological setting. Hydrogeology Journal.

2003. P. Ravenscroft. An Overview of the Hydrogeology of Bangladesh. In: Rahman AA and Ravenscroft P (Eds.). Groundwater Resources and Development in Bangladesh– background to the arsenic crisis, agricultural potential and the environment . Bangladesh Centre for Advanced Studies. University Press Ltd, Dhaka.

2001. J M. McArthur, P Ravenscroft, S. Safiullah and M.F. Thirlwall. ‘Arsenic in groundwater: testing pollution mechanisms for sedimentary aquifers in Bangladesh’ Water Resources Research, 37(1), 109-117.

2001. P Ravenscroft, , J.M. McArthur and B.A. Hoque. Geochemical and Palaeohydrological Controls on Pollution of Groundwater by Arsenic. In: Chappell, W.R, Abernathy, C.O, and Calderon, R.O. Arsenic Exposure and Health Effects. P53-77. Elsevier Science BV, Netherlands.

2001. P Ravenscroft. Distribution of groundwater arsenic in Bangladesh related to geology. In: G Jacks, P Bhattacharya and A A Khan (Eds). Groundwater arsenic in the Bengal Delta Plain of Bangladesh. Proceedings of the KTH-Dhaka University Seminar. KTH Special Publication, TRITA-AMI Report 3084, p41-56.

2000. ‘Extensive Arsenic Contamination of Bangladesh Groundwater: Curse of Unmanaged Development?’ K M Ahmed and P Ravenscroft. Proceedings of the 4th International Symposium on Environmental Geotechnology and Global Sustainable Development (Eds. H I Inyang & V O Ogunro), CEEST, University of Massachusetts, Volume I, pp. 105-114.

2000. R Nickson, J M McArthur, W G Burgess, P Ravenscroft, and K M Ahmed.‘Mechanism of arsenic release to groundwater, Bangladesh and West Bengal. Applied Geochemistry.15, 403-413.

1999. ‘Groundwater Studies for Arsenic Contamination in Bangladesh. Rapid Investigation Phase’. Final Report. Mott MacDonald Ltd and British Geological Survey. Report prepared for Department of Public Health Engineering (Bangladesh) and Department for International Development (UK).

1998. ‘Occurrence and origin of water well methane gas in Bangladesh.’ with K M Ahmed, M. Hoque, M.K. Hasan, P Ravenscroft and L.R. Chowdhury. J. Geol. Soc. India, 51, 697-708.

1998. R Nickson, J M McArthur, W G Burgess, P Ravenscroft, K M Ahmed, and M Rahman. ‘Arsenic poisoning in Bangladesh groundwater’ Nature (London), v395: 338.