ABSTRACT
Forty one groundwater samples were collected for physico-chemical analyses from hand pumps and tubewells ranging in depths of 25 to 90 m. Locations of the wells were marked with Global Positioning System (Fig. 1). Temperature, pH, Electrical Conductivity (EC), and turbidity were meausered in the field along with As by using Hach field test kit. The groundwater samples were analyzed for chemical species [chloride (Cl−), carbonate (CO32−), bicarbonate (HCO3−), nitrate (NO3−), phosphate (PO43−), sulfate (SO42−), sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), fluoride (F−), iron (Fe) and As]. The groundwater samples
1 INTRODUCTION
Arsenic (As) enrichment has been reported in the groundwater of the deltaic flood plains in several regions of South Asia (Bhattacharya et al. 1997). Arsenic has recently been encountered in the deltaic flood plains of the Indus River in Punjab and Sindh provinces of Pakistan (Husain 2009). Arsenic hot spots in Sindh include Tando Mohammad Khan and Tando Allayar districts (25°8'N and 68°32'E) through which Indus River passed during Holocene period depositing younger alluvium constituting inter-layered deposits of very fine sand, silt and clay. The response of Indus river basin to the intensification of the South Asian monsoon shows that summer monsoon strengthened as global climate warmed between Last Glacial Maxima (ca. 20 Ka) and the Holocene (ca. 8 Ka). The area is mainly covered by thick alluvium with low to very low relief comprising deposits of active flood plains, meanders and channel levee. The rocks exposed in the study area belong to Laki Formation of Eocene age comprising of soft, chalky to nodular limestone with some marl, gypsiferrous shale and sandstone.
