Outlines

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Arsenic Contamination of Bangladesh Paddy Field Soils Implications for Rice Contribution to Arsenic Consumption
ProfessorPao-Nuan Hsieh ,Ph.D. ReporterTzu-Hui Ho(???) Nov 19th, 2009
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Outlines

• Abstract
• Introduction
• Materials and Methods
• Results and Discussion
• References

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• ??????????(Smedley and kinniburgh, 2002)

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• (Smedley and kinniburgh, 2002)

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Abstract

• Arsenic contaminated groundwater is used
  extensively in Bangladesh to irrigate the staple
  food of the region, paddy rice.
• A survey of arsenic levels in paddy soils and
  rice grain was undertaken.
• Regression of soil arsenic levels with tube-well
  age was significant.

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Introduction(1/4)

• The digging of tube-wells for drinking water
  supply into aquifers elevated in arsenic in
  Bangladesh and West Bengal has been described as
  the greatest mass poisoning in human history.
  ---36 million people exposed
• Groundwater arsenic concentrations approaches 2mg
  L-1, 200,000-270,000 people will die of cancer
  from drinking arsenic contaminated drinking water

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Introduction (2/4)

• Arsenic contaminated groundwater is not just used
  for drinking water but is also widely used for
  irrigation of crops,and particularly for the
  staple food paddy rice,provides 73 of calorific
  intake
• Groundwater is used extensively to irrigate rice
  crops in Bangladesh, particularly during the dry
  season with 75 of the total cropped area given
  over to rice cultivation and 83 of the total
  irrigated area used for rice cultivation.

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Introduction (3/4)

• Levels of arsenic in rice grain are typically
  0.05-0.4 µg g-1 for North America, Europe, and
  Taiwan(0.074 µg g-1 ).
• Arsenic levels in rice grain reached 0.7 µg g-1
  in rice grown on paddy soils containing 68 µg g-1
  arsenic in China , showing the potential for
  arsenic contamination of rice grain from
  contaminated paddy soils.

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Introduction (4/4)

• Contamination of soil was related to tube-well
  arsenic levels, depth, and age to understand the
  mechanism of soil contamination by arsenic.
• Arsenic levels in Bangladesh produced rice, were
  determined to calculate baseline exposure of the
  population to rice derived arsenic.
• Dietary arsenic exposure was then modeled using
  these data.

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Materials and Methods (1/3)

• Collection of Soil and Rice Grain SamplesSoil
  and rice samples were collected during the period
  of January-February, 2001.
• Soil samples were collected from 27
  administrative districts of Bangladesh, and a
  total of 71 samples were obtained.

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Materials and Methods (2/3)

• Analysis
• soil and rice grain(husk)?oven dry(70
  ºC)?grinding
• ?digested?nitric acid-hydrogen peroxide
• ?heating block(60 ºC)?cooled ?diluted in
  deionized water
• ?filtered(Whatman no. 42 filter paper)
• ?soil(Perkin-Elmer 3300)
• ?rice grain(Perkin-Elmer Aanalyst 300?FIAS
  100 hydride generator)

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Materials and Methods (3/3)

• Tube-Well Datayear constructed, depth, arsenic
  levels obtain from the British Geological Survey
  (BGS) web-site.
• The BGS tube-well data was similarly averaged per
  district for comparison with the soils data.
• StatisticsMinitab v.13

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Results and Discussion (1/9)

• Arsenic in Paddy Soils
• ?surface paddy soils 3.1 to 42.5 µg g-1
• ? the age and depth of the tube-wells need to
  be
• considered as arsenic will accumulate in
  the
• soil with long period of time
• ? the soils had become contaminated through
• irrigation with arsenic contaminated water

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Results and Discussion (2/9)
well age vs arsenic levels(soil)
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Results and Discussion (3/9)

• Continuous variable
• Two continuous variable ?covariance
• Linear regression
• Linear regression of tube-well age against paddy
  soil arsenic levels was significant (P.048)lt.05
• Similar regressions with tube-well depth (P.505)
  gt.05 and
• tube-well arsenic levels (P .684) gt.05
  were not significant

Regression equation
Scatter plot
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Results and Discussion (4/9)

• tube-well depth and arsenic concentrations in the
  well water were not significantly

well depth(m)25-50
Arsenic levels(GW)50-250
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Results and Discussion (5/9)

• Arsenic Levels in Rice
• Samples collected from Gazipur District at the
  Bangladesh Rice Research Institute had an average
  level of
• 0.092 µg g-1 dry wt,
• highest 0.21 µg g-1

Arsenic content 10.9,14.6 µg g-1
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Results and Discussion (6/9)

• Western Bangladesh Districts arsenic levels
  ranging from 0.058 to 1.83 µg g-1
• arsenic levels within the same range as the
• field trials at Gazipur

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Results and Discussion (7/9)

• 113.5 mg?kg(as soil), 0.074 mg?kg(rice grain),at
  Guandu,

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Results and Discussion (8/9)

• calculate daily human intake of arsenic from
  rice.
• With a drinking water intake of 0.1 mg L-1,
  arsenic intake from rice will account for 17.3
  and 29.6 of arsenic consumption if rice
  contained 0.1 and 0.2 µg g-1 of arsenic,
  respectively.
• These grain values are typical of what has been
  observed in a range of studies in Asia, Europe,
  and N. America

0.01
0.1
1
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Results and Discussion (9/9)

• the bioavailability of arsenic in rice
• arsenic in rice grain ?inorganic arsenic?toxic
  and readily assimilated into the blood stream
• provide a safe water source
• decrease dietary exposure from arsenic still
  exists.

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References

• Meharg, A. A., and Rahman A. A., 2003.
  Arsenic Contamination of Bangladesh Paddy Field
  Soils Implications for Rice Contribution to
  Arsenic Consumption, Environmental Science
  Technnology, 37(2)229-334.

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• Thanks for your attention!!