Arsenic transfer in water, soil and crop environments of Bangladesh and Australia
ACIAR
project LWR1/1998/003
This project is being conducted in Bangladesh with the
collaboration of Dr S.M. Imamul Huq at
Dhaka University. This four
year study commenced in 1999 and focused on the pathways of arsenic
transfer from arsenic contaminated groundwater to humans.
Field surveys have collected groundwater, soil, plant and human
health information from three villages in the districts of
Munshigang, Narayanganj and Comilla. These three districts have a
well documented history of patients presenting with symptoms of
arsenocosis at the Dhaka
Community Hospital.
Analysis of groundwater samples found that:
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Total arsenic concentrations ranged from less than 1 to 800 parts per billion, whereas the current Australian drinking water standard for arsenic is only 7 parts per billion
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Groundwater samples collected from wells deeper than 250 feet contained arsenic concentrations less than 1 part per billion
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Drinking water is mainly obtained from wells deeper than 250 feet
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Groundwater samples collected from shallow wells (less than 200 feet deep) contained arsenic concentrations greater than 50 parts per billion, the current Bangladeshi drinking guideline
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Irrigation water for vegetable crops was typically obtained from shallow wells less than 150 feet deep
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Speciation of groundwater found that arsenic was present as the more toxic arsenite species.
Analyses
of soil and plant samples collected from agricultural areas around
each village found that:
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Soil concentrations of arsenic were less than 20 parts per million which is relatively small when compared to soil arsenic concentrations observed in many other countries
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Elevated arsenic concentrations accumulated in some plant materials such as Arum and potato
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Glasshouse studies revealed that Arum root (Colocasia antiquorum) consistently accumulated higher concentrations of arsenic than other crop studied irrespective of the environmental conditions under which the crops were grown.
In
conjunction with research undertaken in Bangladesh, research was
conducted on the significance of arsenic contamination from the
application of arsenic-based herbicides along former railway
corridors in South Australia and in the historical
Golden Triangle
gold-mining area of Victoria.
Research in South Australia was conducted with support of
Transport SA
and the Department for Environment
and Heritage and the
University of Ballarat in Victoria.
Over three hundred kilometres of former railway corridor were
assessed during the 1999 to 2002 period for the extent and severity
of arsenic contamination. Analysis of soil, water and plant samples
collected found that
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Arsenic concentrations along the former railway corridors was extremely variable but was generally restricted to the former track area
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Railway sidings or depots contained higher and more extensive areas of arsenic contamination than the former railway corridors
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No evidence was observed for the migration or accumulation of arsenic into water environments or crops except where contaminated soil had been removed for other uses.
The
assessment of the severity and extent of arsenic contamination in
the Golden Triangle
region of central Victoria was conducted during the 1999 to 2002
period. Analysis of soil, water and plant samples collected found
that:
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Arsenic concentrations in surface waters collected from streams and storage dams were extremely variable with elevated arsenic concentrations located in many areas where former mining had been conducted
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Arsenopyrite oxidation of mine waste is the predominant cause of elevated arsenic concentrations in the surface waters sampled
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Arsenic concentrations in uncontaminated soil samples were less than 40 parts per million
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Arsenic concentrations in contaminated soils collected from selected townships was significantly greater with arsenic concentrations up to 16, 000 parts per million being recorded in surface soils
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The extent of contamination at the contaminated sites was generally localised and rapidly declined away from contaminated site
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Native plant samples collected from the contaminated sites contained elevated arsenic concentrations up to 47 parts per million
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Plant studies with bean and silverbeet plants grown in mining waste materials found that arsenic concentrations in edible portions of bean and silverbeet plants exceeded the Australian Food Quality standard of 1 part per million fresh weigh.