1 arsenic contamination of bangladesh paddy field soils: implications for rice contribution to...
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Arsenic Contamination ofBangladesh Paddy Field Soils:Implications for Rice Contribution toArsenic Consumption
Professor: Pao-Nuan Hsieh ,Ph.D.
Reporter: Tzu-Hui Ho(何姿慧 )
Nov 19th, 2009
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OutlinesOutlines
• Abstract
• Introduction
• Materials and Methods
• Results and Discussion
• References
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• 世界各地砷污染之分佈( Smedley and kinniburgh, 2002 )世界各地砷污染之分佈 ( Smedley and kinniburgh, 2002 )
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台灣地區高砷含量之地下水區
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AbstractAbstract
• 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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IntroductionIntroduction(1(1/4/4))
• 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 Introduction (2(2/4/4))
• 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 Introduction (3(3/4/4))
• 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 Introduction (4(4/4/4))
• 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 Materials and Methods (1(1/3/3))
• Collection of Soil and Rice Grain Samples:Soil 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 Materials and Methods (2(2/3/3))
• 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 Materials and Methods (3(3/3/3))
• Tube-Well Data: year 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.
• Statistics:Minitab v.13
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Results and Discussion Results and Discussion (1(1/9/9))
• 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 Results and Discussion (2(2/9/9))
well age vs arsenic levels(soil)
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Results and Discussion Results and Discussion (3(3/9/9))
• Continuous variable
• Two continuous variable →covariance
• Linear regression • Linear regression of tube-well age against paddy
soil arsenic levels was significant (P=.048) 〈 .05
• Similar regressions with tube-well depth (P=.505) 〉 .05 and
tube-well arsenic levels (P =.684) 〉 .05 were not significant
Scatter plot
Regression equation
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Results and Discussion Results and Discussion (4(4/9/9))
• tube-well depth and arsenic concentrations in the well water were not significantly
Arsenic levels(GW)50-250
well depth(m)25-50
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Results and Discussion Results and Discussion (5(5/9/9))
• Arsenic Levels in Rice : Samples collected from Gazipur District at the Ba
ngladesh 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 Results and Discussion (6(6/9/9))
• 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 Results and Discussion (7(7/9/9))
• 113.5 mg kg(as soil), 0.074 mg kg(rice grain),at Guandu,╱ ╱
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Results and Discussion Results and Discussion (8(8/9/9))
• 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
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0.1
0.01
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Results and Discussion Results and Discussion (9(9/9/9))
• 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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ReferencesReferences
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!!