A capstone undergraduate course based on arsenic
problem in Bangladesh groundwater
Yan Zheng
Queens College, CUNY and Lamont-Doherty Earth Observatory
“Environmental Problem Solving”
Environ. Sci. & Studies Senior
A
simulation of actual environmental
problems and case histories that utilize
interactive, self-directed investigations by
student teams.
 Oral and written presentations in mock
environmental hearings are required.
Why Arsenic in Bangladesh
Groundwater
 About
40 million people exposed to > 50
mg/L As (US drinking water MCL 10 mg/L)
 Chronic exposure leads to various cancers,
skin and cardiovascular diseases.
 Multidisciplinary:
Earth Science, Health Science, Engineering, Social Science
http://superfund.ciesin.columbia.edu
•About 10 million tube wells
supply 97% population’s
drinking water
• 50% wells > 10 mg/L As
• 28% wells > 50 mg/L As
UNICEF & DPHE
50,000 well test
groundwater
25% volume
As in groundwater
7950 mg/l
Solid
75% volume
Dissolve
Desorb
Mobilizable
As in sediment
1 mg/kg
Proximate Source of As:
Reducing Condition
(Anoxic with dissolved Fe)
Ultimate Source Hypothesis:
Physically weathered but not-chemically weathered Fe-Mg minerals in
rapidly accumulating sediment (Holocene delta/fluvial plain, glacial till)
Fluvial Flood Plain
Delta Plain
Zheng et al., submitted
http://www.bgs.ac.uk/arsenic/
Age distribution of tube wells in Araihazar and in
Bangladesh
Number of wells doubled in past 5 years (van Geen et al., 2002)
As distribution in 6000 tube wells from Araihazar
(van Geen et al., WRR, 2002)
C E
A
B
G
F
Groundwater As(III) and As (Zheng et al., submitted & in prep)
A
0
400
600
200
400
0
600
0
20
20
20
Depth (m)
40
60
0
0
200
200
400
60
400
600
60
200
B
400
600 100 0
0
20
40
600
40
F
100 0
600
0
400
80
G
Depth (m)
60
60
80
20
40
40
200
20
Depth (m)
100
Depth (m)
0
Pleistocene
80
Depth (m)
0
0
Holocene
Depth (m)
200
E
C
40
60
80
80
80
100
100
100
Holocene
Deep Aquifer Sustainability
Withdrawal rate:
Drinking (10L/person day) 1 cm/yr
Irrigation
60 cm/yr

A (Dari)
B (Bay)
Residence Time (kyr)
10
1
Recharge Rate (cm/yr)
0.15
1.5
Clay thickness (m)
15
1
Hydraulic Cond. (cm/s)
5x10-8
5x10-7
Vertical hydraul. Grad (m) 1
0.1
Leakage Rate (cm/yr)
1.6
0.2
Conductivity
HCO3
Dominant cation
pH
Shallow Hol.
H
H
Ca, Mg
6-7
Deep Pleist. (A)
L
L
Na
6
Deep Hol. (B)
L
H
Na
7-7.5
14C-DIC
Tritium
Sediment As
Bomb
Bomb
H
Deep Pleist. (A)
0.3
N.D.
L
Deep Hol. (B)
0.8
(N.D.)
L
Shallow Hol.
P-ext As
mg/kg
1-2
0.1-0.2
As
ORP
Fe
Mn
SO4
NH4
PO4
Shallow Hol.
H
-
H
H
H
H
H
Deep Pleist. (A)
<5
+
L
L
L
L
L
<10
-
L
L
L
L
L
Deep Hol. (B)
Conclusions
(Zheng et al., submitted to WRR)




groundwater As concentrations can be low in deep aquifers with a very
different depositional history and a very different residence time
relative to recharge.
The concentration of easily mobilizable As present in the sediment is
a key explanatory variable for dissolved As in groundwater.
Usage of the deep aquifers for domestic water consumption appears
to be sustainable.
the deep aquifers should not be used for irrigation until the
hydrological and chemical responses to increased withdrawals are
better understood.
Targeting Safe Aquifer: Test and Map Existing Wells
Site A
S##S #S
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U#
%
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S#S%U#S%U #S #S
S
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S
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S#S# #S #S
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#S #S#S#S #S#S#S#S #S#S%U
#S
#S
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#S
#S
#S
S#
#S
S##S
#S #S
S# S#
#S #S#S #S S#
#S
S# S# #S#S#S
#S
S#
#S#S#S
As (mg/l)
<5-820
#S
S##S #S
30-55ft
132+-144
mg/L As
#S #S
#S
#S
#S #S
0
S#
#S#S#S
0.2
S##S#S
0.4
0.6
0.8
1 Kilometers
Longitude (degree)
Depth ft
90.596
0
90.598
90.6
90.602
90.604
90.606
90.608
90.61
50
14C
100
150
200
5--10"
10--50
50--100
100--400
400-800
dead
 Text:
Student Activities
BGS Phase II Report
 1-hr lecture & 2-hrs data manipulation
 Grade:
Team Presentation and Report (5-page) (1x20%)
Peer Review (1-page) (2x20%)
Proposal Presentation (10%)
Proposal (15-page; 30%)
Syllabus
Science Background: Geology, Hydrology & Geochemistry
 Science Investigation:
Team 1: three special study area
Team 2: A village survey and spatial scale of variation
time scale of variation
Mineralogy and sediment chemistry
mechanism of As release – summary
 Engineering: Remediation Measures
Geological engineering: deep well, dug well, well-switching
Water engineering: Arsenic removal techniques
 Policy
Introduction to policy issues (Strategic Plan)
Team 3: Social and economical issues in remediation policy

Data Manipulation: Excel
As (ug/L)
0
0
50
100
Depth (m)
150
200
250
300
350
400
500
1000
1500
2000
Data Manipulation: ArcView
 Map
of As distribution in groundwater
Proposal Guideline
Propose a solution for a specific aspect of the
arsenic problem in Bangladesh groundwater
A.executive summary
B.statement of the problem
C. objective
D.hypothesis
E.approach
F. expected results and significance

Summary of Student Proposals









Well sharing as short-term solution
Deep well and pond sand filter on a community level
Removing arsenic from groundwater: treatments vs. deep tube wells
The principle of arsenic removal from groundwater by iron
impregnated sand
Alternative source of drinking water: rain water harvesting
Rain water harvesting using a large polyethylene storage container
Solving arsenic problem using educational and economical approach
Evaluation of safe water options and recommendation
Possible treatment of arsenic related affliction
Examples of Hypothesis



Through a number of different methods, year-round supplies of arsenic-safe
drinking water can be made available to the people of Bangladesh at relatively
low cost.
Until the effects of metabolic methylation of AsV and AsIII are completely
understood, no treatment advocating the acceleration or aiding of this
process should be recommended as a primary mode of treatment.
By educating the people of Bangladesh through BRAC schools, the people of
Bangladesh would come to the realization of the poison in their water and
hence not use the contaminated water as their drinking water. My other
hypothesis is that if the American public were aware of the catastrophe in
Bangladesh, the people of America would sympathize and make monetary
contributions. This in turn would help out with some of the cost of treating
the arsenic in Bangladesh.
What works: anecdotal evidence
 Data
manipulation enhances learning
 Peer
review keeps the student engaged
 Oral
presentation before submission of
written reports or proposal
Student Evaluation (n=10)
Communication
4.4
Assignments, Grading 4.3
Faculty Interaction
4.3
Outcomes
3.9
1: strongly disagree; 5: strongly agree
Q: The instructor clearly presented course
requirements and objectives early in semester
Learned a great deal but only enjoyed the course moderately
Moderately difficult, taught at just about right speed,
with moderate to somewhat heavy workload
6
5
5
Enjoyed the course
Learned a great deal
6
4
3
2
4
3
2
1
1
0
0
0
1
2
Current GPA
3
4
0
1
2
Current GPA
3
4
Acknowledgement
Collaborators
Columbia: A. van Geen, M. Stute,
M. Steckler, R. Versteeg, J.
Simpson, Z. Cheng
SUNY Stony Brook: S. Goodbred
Israeli Geol. Survey: I. Gavrieli
Dhaka: K. M. Ahmed
 Students
CUNY: R. Dhar, Y. He, Z. Mo
Columbia: A. Horneman
SUNY Stony Brook: B. Weinman
Dhaka: M. Shanewaz, M. Shams,
A. Sedique, M. Hoque

Funding Agency
NIEHS/Super Fund Basic
Research Program
NSF EAR & INT
Columbia Earth Institute

Geology and Human Health Workshop Conveners
What is Environmental Science?



What is the core knowledge expected of an
environmental science major?
Does it make sense to have biology, chemistry and
geology tracks?
Should geologists take an active role in defining
the core knowledge of environmental science?
A textbook for introduction to
the environment
 Resources
(energy, air, water, food)
 Human impact on the environment
 Human impact on human health
 Case studies of environmental issues of
global impact
 Laboratory modules based on local
environmental issues
a bit of background about your issue (e.g. As in groundwater in Bangladesh), and
then how you use this topic or issue in your own instructional activities.
What do the students have to know about the subject? What activities do
you have them do? Do they do projects? Modeling? Access databases and
tools and plot results? etc. Most of the participants will want to know
"what works" based on your experience in teaching about this, and also
what barriers or problems you might expect to encounter (i.e. teaching tips
about how to design and implement your type of project). Again, after
doing many workshops of this type, it's our experience that folks will not
want to use your materials/approaches directly, but they will want to
develop similar activities for their own students, in their own instructional
setting, in their own courses, etc. So, any advice you can give folks to take
home about how to design, implement and assess student activities would
be a really nice contribution
hyperpigmentation
keratosis
skin cancer
fatalities due to internal cancers
neurological problems
miscarriages
premature delivery in reproductive females
Hypothesis: Floodplain
evolution can explain the
distribution of arsenic in
Araihazar
Weinman et al., in prep