title: Investigation of severe water problem in urban areas of a developing country: the case of Dhaka, Bangladesh.
abstract: The present study evaluated water supply geochemistry in Dhaka City, Bangladesh, to provide detailed trace level (subppb) water quality data that include major ions, low dissolved oxygen (DO) and toxic trace metals for sustainable development. Dhaka Groundwater, which almost uniformly meets the World Health Organization guideline, has become the preferred source. Due to groundwater depletion and an ever-increasing need to meet water demands by city residents, Dhaka water supply and sewerage authority has initiated the treatment of river water, despite the fact that very little is known about the geochemical structure, and trace metal content in the Dhaka water supply. Major ion composition of water samples was determined, and the results used to generate Stiff diagrams. The diagrams served to visually compare water from different sources based on units of mass/volume. Hydrochemical facies analysis showed supply ground and surface waters are comprised predominately of Ca-Na-Mg-HCO3 and Ca-Na-Mg-HCO3-Cl types. Spatial distribution of ions, and Na/Cl and Na/SiO2 molar ratio indicated that silicate weathering is the dominant geochemical process. Chemical data revealed that toxic Cr metal mobilization is associated with chemical hazards from the leather industry. The vulnerability of deep wells to contamination by As is governed by the geometry of induced groundwater flow paths and the geochemical conditions encountered between the shallow and deep regions of the aquifer. Quantifying total arsenic (As) and As from interlocking geochemical cycles (Fe, Mn) may assist in interpreting As dynamics in Dhaka well water. The surface source water was hypoxic to anoxic low DO associated with very high concentrations of biological oxygen demands, and electrical conductivity compared to industrial and non-industrial urban processes and standard activity guidelines. The results of this study should be applied to future research focused on the potential to improve water quality in urban and surrounding areas.
authors.affiliation: Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan, msnahar@yahoo.com.
authors.forename: Mst Shamsun
authors.initials: MS
authors.lastname: Nahar
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Akira
authors.initials: A
authors.lastname: Ueda
authors.forename: Fujishiro
authors.initials: F
authors.lastname: Yoshihisa
mesh_terms: D001151:Arsenic / Q000032:analysis; D001459:Bangladesh; D003247:Conservation of Natural Resources; D003906:Developing Countries; D060766:Drinking Water / Q000032:analysis*; D004784:Environmental Monitoring; D060587:Groundwater; D019216:Metals, Heavy / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality; D014881:Water Supply / Q000032:analysis*
chemical_list: D060766:Drinking Water; D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D001151:Arsenic
references.citation: Environ Geochem Health. 2012 Feb;34(1):141-50
references.pmid: 21670987
references.citation: Environ Sci Technol. 2001 Sep 15;35(18):3676-82
references.pmid: 11783644
references.citation: Sci Total Environ. 2009 Apr 1;407(8):2796-807
references.pmid: 19185905
references.citation: Nature. 2004 Jul 1;430(6995):68-71
references.pmid: 15229598
references.citation: Sci Total Environ. 2009 Dec 1;407(24):6242-54
references.pmid: 19783282
references.citation: Science. 2006 Dec 15;314(5806):1687-8
references.pmid: 17170279