Abstract
Abstract. Spatial point pattern is one of the most suitable methods for analysing groundwater arsenic concentrations. Groundwater arsenic poisoning in Bangladesh has been one of the biggest environmental health disasters in recent times. About 85 million people are exposed to arsenic more than 50 μg/L in drinking water. The paper seeks to identify the existing suitable aquifers for arsenic-safe drinking water along with “spatial arsenic discontinuity” using GIS-based spatial geostatistical analysis in a small study site (12.69 km2) in the coastal belt of southwest Bangladesh (Dhopakhali union of Bagerhat district). The relevant spatial data were collected with Geographical Positioning Systems (GPS), arsenic data with field testing kits, tubewell attributes with observation and questionnaire survey. Geostatistics with kriging methods can design water quality monitoring in different aquifers with hydrochemical evaluation by spatial mapping. The paper presents the interpolation of the regional estimates of arsenic data for spatial discontinuity mapping with Ordinary Kriging (OK) method that overcomes the areal bias problem for administrative boundary. This paper also demonstrates the suitability of isopleth maps that is easier to read than choropleth maps. The OK method investigated that around 80 percent of the study site are contaminated following the Bangladesh Drinking Water Standards (BDWS) of 50 μg/L. The study identified a very few scattered “pockets” of arsenic-safe zone at the shallow aquifer.
Highlights
Water resources are a prerequisite for human development and progress
The term “contamination” in this paper refers to the elevated levels of arsenic concentrations above the Bangladesh Drinking Water Standards (BDWS set by Department of Environment)
Arsenic concentrations can be classified into a number of classes (Table 1 and Figure 3): (a) WHO permissible level (≤10μg/L); (b) BDWS (10.1-50μg/L); (c) moderate contamination level (50.1-100μg/L); (d) high contamination level (100.1-300μg/L); and (e) severe contamination level (>300μg/L)
Summary
Water resources are a prerequisite for human development and progress. Groundwater is purportedly the main source of untreated pathogen-free safe drinking water in more than onethird (2.4 billion) of the total population on the globe (WHO, 2015). Spatial discontinuity of arsenic concentration has been reported in Bangladesh (Radloff et al, 2017), West Bengal in India (Biswas et al, 2014), China (Cai et al, 2015; Ma et al, 2016), Chianan Plain of Taiwan (Sengupta et al, 2014), Mekong Delta of Vietnam (Wilbers et al, 2014), the southern Pampa of Argentina (Díaz et al, 2016), the Duero River Basin of Spain (Pardo-Igúzquiza et al, 2015), Nova Scotia in Canada (Dummer et al, 2015), Wisconsin in the USA (Luczaj et al, 2015), the Águeda watershed area in Portuguese district of Guarda and the Spanish provinces of Salamanca and Caceres (Antunes et al, 2014), and so on Is it safe to drink tubewell water? Geostatistics with kriging methods can design water quality monitoring in different aquifers with hydrochemical evaluation by spatial mapping
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