Summary of 12th February 2001 presentation on,

"POSSIBLE ARSENIC-CONTAMINATION-FREE GROUNDWATER SOURCE IN BANGLADESH"

by Dipankar Chakraborti, Dhaka, Bangladesh.

What I am presenting here is a summary of the above presentation. The original report is about 400 pages with more than 50 maps, 100 tables.

Background

School of Environmental Studies (SOES), Jadavpur University, Calcutta, India and Dhaka Community Hospital (DCH), Bangladesh are working on arsenic groundwater contamination in Bangladesh for about last 6 years. During June-July, 1999, we had finished 24,000 (twenty-four thousand) water analyses for arsenic by FI-HG-AAS (our determination limit with 95% confidence is 3 mg/l) covering all 64 districts of Bangladesh and analyzed thousands of hair, nail, urine, skin scales from people living in arsenic-affected villages and screened 25,000 people from the affected villages for arsenical skin lesions (15% of 25000 people screened have arsenical skin lesions). Estimated information of all these patients with nature and magnitude of skin lesions were registered. Hair, nail, urine, and skin-scale of about 35% of these patients were also analyzed. We tried to establish the co-relation between arsenic in hair, nail, urine and concentration of arsenic in drinking water. When skin-lesions will appear on body depends on many factors like (a) concentration of arsenic in drinking water, (b) how long one is drinking the contaminated water, (c) how much one is drinking contaminated water per day (in many families we have found those drinking too much water have arsenic skin lesions when those drinking less have no skin lesions), and (d) nutritional status of the people drinking contaminated water also play an important role. We have hundreds of examples showing that poor people suffering from malnutrition show arsenical skin lesions but people getting better nutrition not showing any skin lesions drinking the same concentration (also close to same volume) of contaminated water. From our 13 years field survey screening more than 100,000 people from West Bengal and Bangladesh and having a list of 12000 registered arsenic patients with skin lesions, we can say that usually above 300 m g/l of arsenic in drinking water may show arsenical skin lesions (exceptions are always there). However, we have found a few patients with spotted melanosis drinking 90 mg/l (Kolsur village, Deganga Block, North 24-Parganas) of arsenic in drinking water in West Bengal and 80 mg/l in Samta village, Sharsha Police Station of Jessore District of Bangladesh. However these are exceptions. Children below 11 years normally don't show the skin lesions but we have registered a few hundred patients aged below 11 years from West Bengal, India and Bangladesh, when arsenic in drinking water is quite high around 700 mg/l and above. Children suffering from malnutrition are also suffering from arsenical skin lesions even with lower arsenic in drinking water (around 400 m g/l).

Groundwaters of Pleistocene Upland, Pleistocene Plain, Hill Tract areas of Bangladesh are mostly arsenic contamination free.

While evaluating our last five years water analysis report (n=24000) from all 64 districts of Bangladesh during middle of 1999, we noticed that in some parts of Bangladesh, the contamination is minimum and in fact some parts are almost arsenic-contamination free. Even we have noticed some portions within highly arsenic-contaminated areas are also quite safe. To be sure about our findings, we cross-checked samples from the same areas and facts and figures generated were almost same. While trying to find out the reason, we noticed that out of the four geo-morphological regions of Bangladesh [(A) Hill Tract, (B) Flood Plain, (C) Pleistocene Upland / Plain (Table Land), and (D) Deltaic Plain with Coastal region], Hill Tract and Pleistocene Upland and Pleistocene Plain are usually contamination free. Exceptions we have noticed in fringe area of Pleistocene Upland and Pleistocene Plain with Flood Plain; Hill Tract with Flood Plain etc. Also we have noticed that if a river had eroded Pleistocene Upland / Pleistocene Plain or Hill Tract area, some contamination is there (the reason may be Holocene deposition occurred in river-eroded area). Please find herewith a few examples.

Example A: Dhaka District

Out of six Police Stations (PS) of Dhaka District; 4 Police Stations-- Dhamrai, Savar, Dhaka City, Keraniganj are in Pleistocene Upland and all are arsenic contamination free but two Police Stations Nawabganj and Dohar are in Flood Plain area and these 2 Police Stations are highly contaminated.

Example B: Narayanganj District has 5 Police Stations-- Araihazar, Sonargaon, Bandar, Narayanganj Sadar and Rupganj and out of these 5 Police Stations only Rupganj Police Station is in Pleistocene Upland and is contamination free when the rest Police Stations are highly contaminated.

Example C: Gazipur district has 5 Police Stations -- Sreepur, Kaliakoir, Gazipur, Kaliganj are in Pleistocene Upland and all are contamination free while Kapasia is in Flood Plain and highly arsenic contaminated with arsenic patients.

Example D: Chittagong district is mainly in Hill Tract but a few Police Stations are partly in Hill Tract and Partly in Flood Plain and the areas in Flood Plain are arsenic contaminated while the Police Stations in Hill Tract are mostly safe. Sitakundu, Mirsharai, Anowara, Banskhali are few arsenic contaminated Police Stations in Flood Plain area of Chittagong district.

Example E: Nawabganj and Rajshahi districts are mainly in Flood Plain area but one police station of Nawabganj i.e., Nachole and two police stations of Rajshahi districts i.e., Godagari and Tanore are in Pleistocene Upland and both these three police stations are almost arsenic contamination free as we expected.

Arsenic in deep tube-wells

While looking about our results in deep tubewells above 100 m from all these 4 Geo-morphological regions, we found all tubewells above 100 m in Hill Tract and Pleistocene Upland / Pleistocene Plain are arsenic-contamination free. In case of Flood Plain and Deltaic Plain (including coastal region), we had noticed that deep tubewells (n=371) above 300 m are mostly (except 4) safe with respect to 50 m g/l but about 22% of tubewells contain arsenic between 10 and 50 m g/l.

On the basis of our findings up to middle of 199,9 we went for a short communication and the paper was published at the end of 1999, please find herewith reference of the paper.

Reference: Possible Arsenic Contamination Free Groundwater Source in Bangladesh. D. Chakraborti, B.K. Biswas, G.K. Basu, U.K. Chowdhury, T. Roy Chowdhury, D. Lodh, C.R. Chanda, B.K. Mandal, G. Samanta, A. K. Chakraborti, M.M. Rahaman, S.Roy, S. Kabir, B.Ahmed, R. Das, M. Salim and Q. Quamruzzaman, J. Surface Sci. Technol. Vol. 15, Nos. 3-4, 179-187, 1999.

The text of the above paper is attached at the end.

From July 1999 till January 2001 we further made a detailed study for all the 4 geomorphological regions and mainly in Pleistocene Upland and Pleistocene Plain and its surrounding areas. Altogether we further analyzed 10000 (ten thousand) water samples from all these 4 geo-morphological regions. After getting all the results of fresh 10000 samples we found it is almost the mirror image of what we found earlier. To confirm our findings we then tried to procure all the analytical results of other organizations working in Bangladesh on arsenic contamination like DPHE/BGS, NGO-Forum, BRAC, Grameen Bank, Gonosastya Kendra, CARE, etc. It appears from the comparative study that over all the findings of others are close to our findings.

Table-1 and Table-2 show the comparative study of SOES-DCH water analysis report with others on Pleistocene Upland and Pleistocene Plain and Hill Tract area.

 

 

Table-1 COMPARATIVE STUDY OF SOES-DCH & OTHER ORGANIZATIONS ON STATUS OF GROUNDWATER ARSENIC CONTAMINATION IN PLEISTOCENE UPLAND & PLAIN AREA

Districts

Police Station

SOES-DCH

DPHE / BGS

NGO FORUM/ CARE

No. of samples analysed

>50 m g/l

Highest Conc. in m g/l

No. of samples analysed

>50 m g/l

Highest Conc. in m g/l

P.S.

Name

No. of samples analysed

>50 m g/l

Panchagarh

Panchagarh sadar, Atwari, Boda, Debiganj, Tetulia

462

0

15

234

1

110

 

 

 

Thakurgaon

Haripur, Thakurgaon sadar, Ranisankail

295

0

9

367

1

127

Sadar

39

0

 

Pirganj

86

6

60

 

 

 

 

 

 

 

Baliadangi

80

1

130

 

 

 

 

 

 

Dinajpur

Birampur, Birganj, Biral, Phulbari, Bochaganj, Khansama, Hakimpur, Kaharole, Nawabganj, Ghoraghat, Chirirandar, Dinajpur sadar, Parbatipur

728

1

77

521

5

87

Sadar, Kaharole, Biral

37

0

Joypurhat

Akkelpur, Joypurhat sadar, Kalai, Khetlal, Panchbibi

398

0

32

211

6

260

Sadra, Akkelpur, Panchbibi

43

0

Bogra

Admdighi, Dupchachia, Kahalo, Nandigram, Sherpur,

359

0

25

227

0

 

Sherpur, Dupchhachia

28

0

Naogaon

Sapahar, Porsha, Niamatpur,Atrai, Badalgachhi, Mahadevpur, Patnitala, Damoirhat,

417

0

22

189

3

140

Badalgachhi, Damoirhat, Mahadevpur

84

0

Tangail

Madhupur, Ghatail, Mirzapur, Sakhipur,

249

0

14

227

2

90

 

 

 

Gazipur

Gazipur sadar, , Kalialair, Sreepur, Kaliganj

249

0

9

121

2

50

Gazipur Sadar, Kalialair, Kaliganj

217

0

Dhaka

Dhaka city, Dhamrai, Keraniganj,

305

0

281

17

95

Demra, Savar

170

2

92

Rajshahi

Tanore, Godagari

155

0

6

91

7

140

 

114*

1

Sirajganj

Raiganj

116

3

60

140

2

61

 

 

 

Lalmonirhat

Patgram

74

0

9

1

0

 

 

 

 

Narayanganj

Rupganj

50

0

BDL

9

0

 

 

41

0

Narsingdi

Belabo

50

1

134

13

1

121

 

 

 

Nawabganj

Nachole

50

0

BDL

27

0

15

 

101*

0

Nilphamari

Domar

125

0

9

39

0

9

 

 

 

Rangpur

Badarganj,Mithapukur, Pirganj

126

3

53

125

0

5

0

TOTAL

65

4544

17

 

2823

47

 

 

 

 

* Surveyed by CARE, Bangladesh; BDL = Below Detection Limit (Our determination limit is 3 m g/l with 95% confidence).

Table-2 COMPARATIVE STUDY OF SOES-DCH & OTHER ORGANIZATIONS ON STATUS OF GROUNDWATER ARSENIC CONTAMINATION FROM HILL TRACT AREA

Districts

Total Police station

SOES-DCH SURVEY REPORT

REPORT OBTAINED FROM OTHER ORGANIZATIONS OF BANGLADESH

DPHE/BGS

NGO FORUM

Surveyed Police station

No. of samples analyzed

As <10 m g/l

As

10-50 m g/l

As >50 m g/l

Max.Conc

m g/l

P.S. Covered

Samples Analyzed

As >50

m g/l

P.S. Covered

Samples Analyzed

As >50

m g/l

Khagrachhari

8

Khagrachhari sadar, Mahalchhari,Manikchhari

39

39

0

0

-

-

-

-

3

13

0

Rangamati

10

Rangamati sadar, Bagaichhari

47

47

0

0

-

-

-

-

-

-

-

Bandarban

7

Ali Kadam, Bandarban sadar

41

41

0

0

-

-

-

-

-

-

-

Cox's Bazar

7

Chakaria, Cox's Bazar sadar

58

58

0

0

-

7

211

1

4

100

0

Chittagong

20

Anowara*, Patiya, Boalkhali, Satkania, Banshkhali*, Raozan, Lohagara, Kotwali, Hathazari, ChandanaishFatikchhari, Rangunia,

282

262

20

0

 

 

 

 

275

5

75

0

9

295

20

Sitakunda*, Mirsharai*

42

15

6

21

67

42

TOTAL (5)

52

23

509

462

26

21

 

12

353

43

16

408

20

* Partly in Flood Plain and partly in Hill Tract. Flood Plain area is arsenic contaminated.

Arsenic contamination in Deltaic Plain (including Coastal region) and Flood Plain area

Deltaic Plain and Flood Plain region are the most arsenic contaminated area of Bangladesh. Although at present 70.5% of the tubewells show arsenic above 10 m g/l and about 55% of the samples above 50 m g/l but from our West Bengal experience we expect in long run more tubewells will become unsafe.

Status of arsenic contamination in 4 districts mostly in Flood Plain area in North, North-West part of Bangladesh lying between Pleistocene Upland and Pleistocene Plain

Table-3 shows arsenic concentration in shallow hand tubewells of Nilphamari, Lalmonirhat, Kurigram and Rangpur in NorthWest and northern part of Bangladesh. Out of total 28 Police Stations only Pirgachha of Rangpur is highly arsenic contaminated. From the analytical results of these 4 districts (Table-3) it appears that these 4 districts are almost safe except Pirgachha P.S. of Rangpur district. The reason is not known. We have an explanation. Although according to the geo-morphological map, most of these 4 districts are in Flood Plain but how truly they are in Flood Plain is a doubt! We suspect that these 4 Flood Plain districts between Pleistocene Upland and Pleistocene Plain where less Holocene deposition took place and sub-soil area is mostly in Pleistocene Upland & Pleistocene Plain.

Table-3 SOES-DCH ARSENIC CONTAMINATION REPORT FROM 4 DISTRICTS IN NORTHERN PART OF BANGLADESH WHERE CONTAMINATION IS MINIMUM

Districts

SOES-DCH STUDY REPORT

Total P.S.

P.S. Covered

Samples Analyzed

<10 m g/l

10-50 m g/l

>50 m g/l

Max.Conc.

in m g/l

Nilphamari

6

6

523

505

18

0

50

Lalmonirhat

5

5

464

434

29

1

104

Kurigram

9

7

539

467

70

2

70

Rangpur

8

7*

240

187

50

3

53

TOTAL

28

26

1766

1593

167

6

 

* Except Pirgachha Police Station which is highly contaminated

Conclusion

In Bangladesh Police Stations situated in Hill Tract, Pleistocene Upland, Pleistocene Plain are almost arsenic-contamination free except the fringe area or where river erosion took place. Also some Flood Plain areas between Pleistocene Upland and Pleistocene Plain like Nilphamari, Kurigram, Rangpur, Lalmonirhat are almost contamination free.

12% of the deep-tubewells analyzed between 100 and 300 meter from Flood Plain and Deltaic regions including Coastal are arsenic-contaminated above 50 m g/l. But deep tubewells above 300 meter are mostly safe with respect to arsenic above 50 m g/l but 22% of these deep tubewells above 300 meter contain arsenic between 10 and 50 m g/l.

Key Words

Hill Tract; Pleistocene Upland; Pleistocene Plain; Deltaic Plain (including Coastal); Flood Plain; Barind, Madhupur; Lalmai Hills; Dupitila; arsenic concentration above 50 m g/l in deep tubewells between 100 and 300 meters; arsenic concentration between 10 and 50 m g/l.

For Information

  • Magnitude of arsenic contamination in 47 districts of Bangladesh with 22003 hand-tubewells analyses
  • Analyses of large no. of hair, nail, urine, skin-scales from arsenic affected area (both patient and non-patient)
  • Dermatological details of about 4000 registered patients.
  • Number of hand-tubewells in Bangladesh.
  • People drinking arsenic contaminated water >10, >50, >300 m g/l.

Read the Ph.D. Thesis

"GROUNDWATER ARSENIC CONTAMINATION IN BANGLADESH"

December 2000

Bhajan Kumar Biswas

School of Environmental Studies

Jadavpur University

Calcutta - 700 032, India

You can purchase the Ph.D. thesis by paying US $ 100

 

 

POSSIBLE ARSENIC CONTAMINATION FREE GROUNDWATER SOURCE IN BANGLADESH

D. Chakraborti*, B. K. Biswas, G.K. Basu, U.K. Chowdhury, T. Roy Chowdhury, D. Lodh, C.R. Chanda, B. K. Mandal, G. Samanta, A. K. Chakraborti, M. M. Rahman, K. Paul

School of Environmental Studies, Jadavpur University, Calcutta - 700 032, India

S. Roy, S. Kabir, B. Ahmed, R. Das, M. Salim, Q. Quamruzzaman

Dhaka Community Hospital, Bara Magh Bazar, Dhaka - 1217, Bangladesh

Journal of Surface Science and Technology Vol. 15, Nos. 3-4, 179-187, 1999.

Our present study with respect to arsenic in water from different environment of aquatic systems considering both surface and sub-surface geological condition with an emphasis to surface erosion and deposition of soil sediment in the Bangladesh Flood Plain and Deltaic Region reflects some clue for possibility of huge arsenic free reservoir water.

The present communication is the outcome of our last 5 years field survey in 64 districts of Bangladesh and on the basis of 25,897 hand tube-well analyses for arsenic from four existing geomorphological regions of Bangladesh. In this report we will highlight (1) the area in Bangladesh where groundwater is not arsenic contaminated and possibility to use shallow hand tube-wells as potential groundwater resource for drinking purpose (2) arsenic contamination scenario of deep tubewells (above 100 meters) all over Bangladesh and suitable depth in arsenic contaminated area to get safe water.

Geomorphologically Bangladesh is mainly divided in four regions (a) Deltaic (including coastal) (b) Flood Plain (c) Tableland (d) Hill Tract. Total sixty-four districts of Bangladesh are in these four regions. In first phase during our last 5 years field survey up to May 2000 we had analysed 24145 water samples for arsenic from hand tubewells by FI-HG-AAS (95% confidence of arsenic determination limit in our FI-HG-AAS system is 3 m g/l) from all these four regions (Table 1). It appears from the results of Table 1 that groundwater of Hill Tract, Tableland are almost free from arsenic contamination and Flood Plain and Deltaic Region including Coastal Belt are highly arsenic contaminated.

____________________________________________________________________________

* Corresponding Author, Tel: 91 33 4735233, Fax: 91 33 4734266, Email: dcsoesju@vsnl.com

Although we could not identify any sample above 50 m g/l from Tableland area but we have found 28 samples having arsenic between 10 and 40 m g/l from 3 police stations (Table 1) out of 23 police stations we had surveyed. So in 20 police station in Table 1 all samples (937) were below 10 m g/l. The reason why these 28 (2.9%) samples have some amount of arsenic in tubewell water can be that we had collected the samples without filtering through membrane filter and thus small invisible particle containing some arsenic compound had dissolved when preservative added (1 ml of concentrated HNO3 per liter of sample) or the area of these police station are slightly contaminated. However, over all data of 937 tube-wells of 20 Police stations from Tableland and 489 samples of Hill Tract indicate the area is free from arsenic contamination (below WHO guideline value of arsenic in drinking water1).

To be sure whether groundwater of Tableland is free from arsenic contamination or not we collected further 1611 hand tube well water samples from 21 new Police stations during July 2000 from 11 districts in Tableland area. Here we had also found 15 samples (0.93%) having arsenic between 21& 40 m g/l. It is important to mention that these 15 samples were again from 4 police stations out of 21 police stations we had covered. Thus 2533 water samples from 38 police stations we surveyed appears safe to drink according to WHO guideline value1.

During our study we noticed that fringe area of Tableland with Flood Plain might get contamination so also if some river passes or history of river eroded the Tableland. The probable reason of contamination may be heavy deposition of Holocene sediments due to severe surface erosion of Tableland and creating aquifer. Again confusion arise when we try to find out the actual extension of Tableland with respect to geographical boundary of the area. The available Tableland map of BGS/DPHE2 and Bangladesh Physical Map3 differs to some extends mainly in bordering area.

When we compare our total 2576 water sample analysis from 44 Police stations from 11 districts of Tableland area with the available report published by BGS/DPHE2 about arsenic contamination, we find that in 40 police stations out of 44 we reported BGS/DPHE also did not report contamination but in rest 4 police stations [Sripur of Gazipur district (2 samples); Mirzapur of Tangail district (1 sample), Porsha of Thakurgaon district (3 samples), Panchagar Sadar of Panchagarh district (1 sample)] they reported arsenic contamination above 50 m g/l). But all these police stations are in fringe area of Flood Plain with Tableland. Moreover, BGS/DPHE arsenic analysis report2 also mentions 20 more police stations in Tableland area free from arsenic contamination. The recent report published by Disaster Forum4 also reported Nachole police station of Nawabganj district and Godagari police station of Rajshahi district are free (no. of samples 188) from arsenic contamination. This also supports our findings (Table-2).

When further we look to the available hand tube-well arsenic analysis report in Bangladesh we find that BGS/DPHE had also reported analytical results for 2887 samples from 65 police station2 which according to our assessment and BGS/DPHE map is in Tableland and results show 51 police stations are arsenic contamination free. But 30 samples out of 790 analysed from 14 police stations showed contamination above 50 m g/l. 12 police stations out of these 14 according to our assessment are mainly in fringe area of Flood Plain and Tableland and the rest 2 police station which are according to us in Tableland. Out of 136 samples analysed from these 2 police stations only 2 samples show arsenic above 50 m g/l. The report of BGS/DPHE mentions above 50 m g/l, so we do not know exact arsenic concentration of these two samples.

Arsenic concentration in hand tube-wells from 100 to 415 meters in all four different geomorphological regions of Bangladesh

So far up to July 2000 from all 4 geomorphological regions of Bangladesh we had analyzed 1217 hand tube-wells from 100 to 415 meters depth. Table-3 shows the arsenic concentration with different depth from each geomorphological region. It appears that deep tube-wells of Tableland and Hill Tract are arsenic contamination free. Deep tube-wells of both Deltaic region (including coastal belt) and Flood Plain are arsenic contaminated but over all result shows higher the depth lower is the arsenic concentration5.

Our 1217 hand tube-wells analysis above 100 meters indicate that out of 931 hand tube-wells above 200 meters 185 have arsenic between 10 and 49 m g/l and 58 tubewells (6.2%) have arsenic above 50 m g/l. The available deep tubewell report above 200 meters from BGS/DPHE2 shows out of 909 deep tubewells from all over Bangladesh 34 (3.7%) are above 50 m g/l. Our result of Table 3 indicating that at depth above 300 meters (except one in Flood Plain and 3 Deltaic Region) the rest are free from arsenic contamination (< 10 m g/l). To get a better understanding of arsenic concentration in deep tubewells we were looking for a police station in a district where maximum numbers of deep tubewells above 200 meters are available. We finally found police station of Kalkini of Madaripur district where more than 1500 deep tube-wells between depth 200 & 310 meters were installed during last 2-3 years. We made a field collection in Kalkini police station on and from 4-6th August 2000, Table-4 shows the results.

It appears from Table-4 that 82 numbers of samples out of 304 we had analyzed have arsenic between 10 & 49 m g/l. Only one sample has arsenic 129 m g/l and the depth is 242 meters. This is only tube-well out of 304 containing high arsenic and the water is saline in nature. We collected the same sample at 2 different date and found the arsenic concentration quite similar.

From Table 4 it appears that above depth 227 meters except one, other tubewells have arsenic below Bangladesh recommended value of arsenic in drinking water. Finally, we expect Bangladesh may have arsenic in groundwater below 50 m g/l at depth above 200 meters. However, the success will depend on aquifer composition as well as design, construction and development of tube-well.

Conclusion

Our analytical result for arsenic from some selected geological units developed by surface erosion from Himalayan terrain and transportation by the Ganga, Bhrahmaputram Meghna river systems during Holocene period in Bangladesh and stratigraphic correlation of these soil sedimentary formations (Table 5) indicate a possibility of an environment of arsenic contamination free huge reservoir of usable water in some areas of Bangladesh. Stratigraphically the Barind Tract, Madhupur Garh, Lalmai Hills of Comilla are same. The Barind Tract, Madhupur Garh and Lalmai Hills of comilla are known as Tableland consists of Pleistocene red clay, silt and sand. Barind Tract and Madhupur Garh are marginally overlain by arsenic bearing Holocene sediments2,6. Arsenic analysis report in some geographical locations in the districts like Gazipur, Bogra, Tangail, which are in Tableland but partially filled up by Holocene Flood Plain deposit show presence of considerable amount of arsenic in its groundwater. The possible reason of such contamination is due to Flood Plain deposition on the eroded surface of Tableland. An unique example is Kapasia police station of Gazipur district, where out of 5 police stations of Gazipur, 4 are in Tableland and free from arsenic contamination while Kapasia the eroded Tableland of Gazipur district filled up by Holocene Flood Plain deposit is found arsenic contaminated. In the Eastern hills of Chittagong the Holocene Flood plain deposit is absent. All the above areas are underlain by a thick medium to coarse sand and gravel bed of Pliocene epoch known as Dupi Tila2,7-13. The Dupi Tila

Sandstone Formation extends all over Bangladesh excepting probably the western two third of the Delta2,14. The Pliocene sandstone gravel beds remains practically unexposed in these regions and forms the main aquifer beneath these areas. The notable geological control on arsenic occurrence in groundwater is in the oldest unit, where the Pleistocene Barind clay, Madhupur clay and Lalmai Hills and East and northeast of hilly areas overlies the Dupi Tila sands are found to contain arsenic free aquifer water. The total area occupied by the Dupi Tila measured roughly 91,000 sq. km. and the total thickness at places attains more than 300 m14. Pliocene Dupi Tila present undisputed evidence as a basement rock of Barind Tract, Madhupur Garh, Lalmai Hills of Comilla having considerable arsenic free water resource.

References

  1. WHO, Arsenic, Environmental Health Criteria 18, World Health Organization, Geneva, 1981.
  2. Groundwater studies for arsenic contamination in Bangladesh, Phase I: Rapid Investigation Phase, Final Report (MAIN REPORT), British Geology Survey, Mott MacDonald Ltd (UK), 1999.
  3. Bangladesh Physical Map; source: Bangladesh in Maps, Dhaka University, World Graphosman World Atlas, 1981, Dhaka, Bangladesh January 1996, pp 7.
  4. Fact Sheet 12 on Arsenic (A Compilation of Information of Arsenic Related issues), Disaster Forum (Source: CARE , Bangladesh), Dhaka, Bangladesh, March 2000, pp 5.
  5. T. Roy Chowdhury, G.K. Basu, B.K. Mandal, B.K.Biswas, U.K. Chowdhury, C.R.Chanda, D. Lodh, S.L. Roy, K.C.Saha, S. Roy, S.Kabir, Q. Quamruzzaman, & D. Chakraborti,. Nature, 401, 545, (1999).
  6. Arsenic pollution in groundwater in West Bengal, June 1991, Steering Committee, Arsenic Mitigation project. Final report PHED, Govt. of west Bengal 1991.
  7. M.K.Alam, A. K. M. S. Hassan, M. R. Khan & J. W. Whitney. Geological Map of Bangladesh, Geological Survey of Bangladesh, 1990.
  8. Monsur Hussain. Stratigraphical and palaeomagnetic studies some Quaternary deposits of the Bengal Basin, Bangladesh. Ph. D. Thesis. Free University of Brussels, Belgium, 1990.
  9. Monsur Hussain. An Introduction to the Quaternary Geology of Bangladesh. International Geological Correlation Programme IGCP-347. Rehana Akhter, Dhaka, 1995.
  10. J. Davies. Pilot study into Optimum Well Design: IDA 4000 Deep Tubewell II Project. Volume 2: The geology of the alluvial aquifers of Central Bangladesh. British Geology Survey Technical Report WD/89/9, 1989.
  11. M.A.Bakr. Quaternary geomorphic evolution of the Brahmanbaria Noakhali area. Geol. Surv. Babgladesh Rec. V. I, 2, 1977.
  12. Final report of the Deep tubewell II project; vol 2.1 Natural resources, vol 2.1/1 Groundwater resources, vol.2.1/3 Groundwater salinity study, (Mott MacDonald International in association with Hunting Technical services). Report prepared for the Bangladesh agricultural development Corporation under assignment to the Overseas development administration, UK, 1992a.
  13. Feasibility study report for Jamuna River bridge construction project. Volume VI: geology and stone material (Japan International Co-operation Agency), 1976.
  14. F. H. Khan, Geology of Bangladesh, University Press, Dhaka, 1991.

Table-1: Hand tubewell arsenic concentration in different geo-morphological area in

Bangladesh (n = 24145) from September 1995 to May 2000

Geo-morphological region

No. of districts within region

Total Police Station

No. of Police Station surveyed

Total no. of samples analysed

Distribution of total samples in different arsenic concentration (m g/l) range

<10

10-50

51-99

100-299

300-499

500-699

700-1000

>1000

Tableland

9

86

23

965

937

28*

 

 

 

 

 

 

Hill Tracts

6

58

23

489

489

 

 

 

 

 

 

 

Flood Plain

27

209

100

8870

1854

1191

900

2646

1103

624

316

236

Delta

22

137

86

13821

2964

3321

1838

3326

1285

768

235

84

Total

64

490

232

24145

6244

4540

2738

5972

2388

1392

551

320

* Out of 28 samples: 17 samples were from Dhaka (arsenic range 10-29 m g/l); 2 samples from Jaipurhat

[(Arsenic range 20 - 30 m g/l) and 9 samples from Bogura:

7 samples arsenic ranges 20 - 30 m g/l; 2 samples arsenic range 34-40 m g/l)].

Table 2 1611 Hand Tubewells water samples collected from 21 Police stations

assured to be in Tableland in 11 districts

Name of the districts

Total Police stations

Name of the Police stations surveyed

No. of samples analysed

Distribution of total samples in different arsenic concentration (m g/l) range

Below 10

10 - 50

Above 50

Thakurgaon

5

Thakurgaon Sadar, Horipur

169

169

 

 

Panchagarh

5

Atoari, Boda, Debiganj

262

2

 

 

Nilphamari*

6

Domar

98

98

 

 

Dinajpur

13

Biral, Hakimpur

159

157

2

 

Gazipur

5

Kaliakair, Sreepur

155

155

 

 

Tangail

11

Madhupur, Mirzapur, Ghatail

200

196

4

 

Sirajganj*

9

Raiganj

90

82

8

 

Bogra

11

Sherpur, Kahaloo,Nandigram

270

269

1

 

Naogaon

11

Porsha, Sapahar

77

77

 

 

Rajshahi*

13

Godagari

88

88

 

 

Nawabganj*

5

Nachole

43

43

 

 

Total

11

94

21

1611

1596 (99.07%)

15 (0.93%)

 

* Nilphamari, Sirajganj, Rajshahi and Nawabganj districts are in mixed geo-morphological

region but Police Stations Godagari and Godagari & Nachole are in Tableland

 

 

 

 

 

 

 

 

Table-3 Distribution of deep tubewells in different arsenic concentration range (m g/l) with

depth collected from four geo-morphological regions of Bangladesh*

Geomorphological regions

Depth range in meter

No. of deep tubewells analysed

Distribution of samples in different arsenic concentration (m g/l) range

<10

10-49

50-99

100-199

200-299

Hill Tract

205 - 250 m

82

82 (100%)

-

-

-

-

Tableland

Total

102 - 204 m

205 - 250 m

25

47

72

25 (100%)

47 (100%)

72 (100%)

-

-

-

-

Flood Plain

 

 

 

Total

102 - 204 m

205 - 250 m

253 - 300 m

305 - 350 m

360 - 415 m

106

96

82

74

70

428

59 (55.66%)

48 (50%)

41 (50%)

46 (62.16%)

62 (88.57%)

256 (59.81%)

8 (7.55%)

28 (29.17%)

33 (40.24%)

27 (36.48%)

8 (11.43%)

104 (24.30%)

17 (16.04%)

8 (8.33%)

2 (2.44%)

-

-

27 (6.31%)

18 (16.98%)

11 (11.46%)

5 (6.10%)

-

-

34 (7.94%)

4 (3.77%)

1 (1.04%)

1 (1.22%)

1 (1.36%)

-

7 (1.64%)

Delta including coastal

 

 

Total

102 - 204 m

205 - 250 m

253 - 300 m

305 - 350 m

360 - 415 m

155

140

113

114

113

635

118 (76.13%)

105 (75%)

84 (74.34%)

71 (62.28%)

102 (90.26%)

480 (75.59%)

28 (18.06%)

22 (15.71%)

16 (14.16%)

40 (35.09%)

11 (9.74%)

117 (18.42%)

1 (0.65%)

3 (2.14%)

5 (4.42%)

3 (2.63%)

-

12 (1.89%)

4 (2.58%)

9 (6.43%)

8 (7.08%)

-

-

21 (3.31%)

4 (2.58%)

1 (0.72%)

-

-

-

5 (0.79%)

Grand Total

 

1217

890 (73.13%)

221 (18.16%)

39 (3.20%)

55 (4.52%)

12 (0.99%)

* Depth information received from local people/owner.

Table 4 Distribution of deep tubewells (between 227-303 meters depth) in different arsenic

concentration range (m g/l), collected from Kalkini police station (PS) of Madaripur

district, Bangladesh

Total samples analysed

Distribution of deep tubewells in different arsenic concentration (m g/l) range

<10

10 - 19

20 - 29

30 - 39

40 - 49

50 - 99

100 - 299

304

221

(72.69%)

40

(13.15%)

28

(9.21%)

11

(3.62%)

3

(0.98%)

-

1

(0.35%)

Table 5 Simplified stratigraphic correlation of the study area2,9

PERIOD

Epoch

F O R M A T I O N

Barind

Madhupur

Lalmai Hills

 

Q

U

A

T

E

R

N

A

R

Y

Holocene

 

Rohonpur Silty Clay

(4 To 10 meters)

~ U.C ~

Barind Clay And Sand (16 meters)

 

 

~ U.C ~

 

Dupi Tila Sand, Red, (Oxidised)

Bashabo Silty Clay

(5 meters)

~ U.C ~

Madhupur Clay & Sand (19 meters)

 

 

~ U.C ~

 

Dupi Tila (Quartz - Chalcedony Gravel Bed)

 

 

 

Pleistocene

 

 

 

Madhupur Clay and Sand (Dhaka clay, Mirpur Silty Clay, Bhaluka Sand

~ U.C ~

 

Dupi Tila

(Quartz Chalcedony Gravel Red)

 

 

Pliocene

~ U.C ~ Unconformity