Spatial Variability of Arsenic in Groundwater (Case Study of Bangladesh)

The spatial variability study of arseruc concentration in Bangladesh has been
characterized in using Geostatistical method. The study involved 1636 sample points of
groundwater in 41 of 64 districts in Bangladesh. Based on the sample points,
approximately 54% and 90% of them are exceeding the Bangladesh drinking standard
(<50J..lg/L) and WHO drinking standard (<10J..lg/L) respectively. Geostatistical
characterization by semivariogram analysis indicated distances over which data are
correlated (range), the extent of variability (sill) and degree of spatial dependencies
(nugget to sill ratio). Based on the analysis, all the parameters suggested that all the
spatial dependencies, variability and autocorrelation are influenced by increasing depth
segments. It is shown that there are moderate to weak dependency (all above 50%),
higher variability and farther distant or range towards increasing depth segments of wells.
Kriging interpolated these data points and produced a smoothed contour map that
estimates unavailable data points in the map. This study indicates that geostatistical
analysis could reveal spatial variability nature of the arsenic in groundwater in
Bangladesh.