Arsenic geochemistry of the sediments of the shallow aquifer and its correlation with the groundwater, Rangpur, Bangladesh

Overview

Saha and colleagues analyzed shallow-aquifer sediments from the Rangpur division of Bangladesh and correlated sediment geochemistry with groundwater arsenic. This is in-scope a3/a4 evidence for groundwater-source attribution and exposure context, not mineral-water product occurrence.

Key numbers

The abstract reports that the sediment deposits were acidic, with mean electrical conductivity 1.16 dS/m. It reports median total organic carbon 0.20%, median total nitrogen 0.02%, and median sulphur 58.68 mg/kg. The average heavy-metal trend in the investigated sediments was Fe > arsenic (As) > Cu > Zn.

Table 2 reports sediment summary values across 12 locations:

The abstract and results text report mean groundwater arsenic as 1.1793 μg/L. The groundwater arsenic range was 0.6704 to 1.8692 μg/L, and all water samples were below the WHO 10 μg/L limit cited by the authors.

Table 3 reports that sediment arsenic correlated significantly with iron at p < 0.05, with Pearson r = 0.648. Figure 3f gives R2 = 0.4199 for sediment As versus Fe, and Figure 4 gives R2 = 0.0902 for groundwater As versus sediment As. The authors interpret the positive correlations with sediment As, Fe, and Cu as evidence that groundwater arsenic derived from geogenic dissolution of arsenic-bearing aquifer minerals such as pyrite and arsenopyrite.

The abstract notes that contemporary arsenic-speciation work in Bangladesh shows As(III) is common in natural water and foodstuffs and that arsenic is inorganic from source, but this study’s own sediment and groundwater measurements are reported as arsenic without a study-specific species split. The source metadata therefore uses tAs.

Methods (brief)

The authors collected groundwater in acidified 100 mL polythene bottles and collected sediment samples in polythene bags. Sediments were air dried, oven dried at 105 degrees C, and analyzed for pH, electrical conductance, sulphur, total organic carbon, total nitrogen, phosphorus, and aqua-regia-extractable As, Cu, Zn, and Fe. Arsenic was measured by AAS with graphite furnace using a Shimadzu AA6800. Groundwater arsenic was measured by AAS, and standard QA/QC protocols included replicate sample analysis.

Related evidence

• Irrigation water and soil amendments as anthropogenic inputs to cropland
• Source attribution and environmental burden apportionment
• Arsenic, Total
• Iron
• Copper
• Zinc

Update history

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