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Donald M. Maynard, P.E. / The Johnson Company, Inc. Seth H. Frisbie, Ph.D. / Better Life Laboratories, Inc. Erika J. Mitchell, Ph.D. / Better Life Laboratories, Inc. Ahmad Zaki Yusuf / Bangladesh Association for Needy Peoples Improvement Mohammad Yusuf Siddiq, Ph.D. / Bangladesh Association for Needy Peoples Improvement Raul E. Sanchez / Green Mountain Laboratories, Inc. Richard Ortega, Ph.D. / Université de Bordeaux 1 Bibudhendra Sarkar, Ph.D. / University of Toronto and The Hospital for Sick Children Aerial photographs by GlobeXplorer™ Presented at the Twenty-first Annual Conference on Contaminated Soils, Sediments and Water, University of Massachusetts, Amherst, MA, 2005. |
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Aerial photographs and interviews were used to determine the effects of geologic deposits, depth of tubewell (drinking water well), age of tubewell, and number of users per tubewell on the concentration of groundwater arsenic (As) in western Bangladesh.
Groundwater samples were collected from 4 neighborhoods in western Bangladesh during July 18 to 21, 2002 (Figure 1). A total of 71 random samples were collected from 67 tubewells in these 4 neighborhoods. A total of 18 random samples were collected from 17 tubewells in each of 3 neighborhoods (Bualda, Fulbaria, and Jamjami). Access was denied at 1 sampling location; therefore, a total of 17 random samples were collected from 16 tubewells in the fourth neighborhood (Komlapur).
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Figure 1. Aerial photographs of western Bangladesh showing the 4 neighborhoods where groundwater samples were collected from tubewells. These 4 neighborhoods are centered in the villages of Bualda, Fulbaria, Jamjami, and Komlapur. Each sampling location is labeled with a +. |
To the extent possible, the sampled tubewells in each neighborhood were distributed at 500-meter intervals along perpendicular axes that radiated in 4 equal lengths from the center (Figure 2). Two samples were collected from the centermost tubewell in each neighborhood. One sample was collected from each of the remaining tubewells. The latitude and longitude of these tubewells were measured using a Garmin Global Positioning System 12 Channel Personal Navigator™.
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Figure 2. Aerial photographs showing the 4 neighborhoods where groundwater samples were collected from tubewells. The arsenic (As) concentration (µg/L) is shown at each sampling location. |
Established collection, preservation, and storage methodologies were used to ensure that each sample was representative of groundwater quality. Accordingly, all sampled tubewells were purged by pumping vigorously for 10 minutes immediately before sample collection. All samples were collected directly into polyethylene bottles. These samples were not filtered. All samples were preserved immediately after collection by acidification to pH < 2 with 5.0 Molar (M) hydrochloric acid (HCl). All samples were stored at 0º to 4º Celsius (C). All samples were analyzed for total As by the arsenomolybdate method (Frisbie et al. 2005).
In addition, an interview of the principal user of each tubewell was conducted in Bangla to determine the depth of each tubewell, the age of each tubewell, and the number of users per tubewell (Figure 3).
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Figure 3. Graphs of the depth of each tubewell (meters), the age of each tubewell (years), and the number of users per tubewell versus the As concentration (µg/L) from tubewells in each of the 4 neighborhoods in this study. In addition, contour maps of this As concentration are shown. |
The effect of geologic deposits on groundwater As concentration was evaluated from the aerial photographs shown in Figures 4 and 5.
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Figure 4. The rivers and lakes currently in western Bangladesh. |
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Figure 5. Interpretation of geologic deposits and groundwater As concentrations from aerial photographs. |
