MOHAMMAD TAHIR SHAH et al., J.Chem.Soc.Pak., Vol. 34, No. 1, 2012 243 Environmental Geochemistry of Surface and Subsurface Water from Dera Ismail Khan Division, Khyber Pakhtunkhwa, Pakistan 1 MOHAMMAD TAHIR SHAH * , 2 ANWAR HUSSAIN ALIZAI AND 3 SHUHAB DANISHWAR KHAN 1 NCE in Geology, University of Peshawar, Peshawar, Pakistan. 2 Geological Survey of Pakistan, Pakistan. 3 Department of Earth and Atmospheric Sciences, University of Houston, Houston, USA. tahir_shah56@yahoo.com* (Received on 30 th September 2010, accepted in revised form 22 nd September 2011) Summary: The Dera Ismail Khan division is situated in the southern most part of the Khyber- Pakhtunkhwa province in Pakistan. Majority of population in this region obtain domestic water from tube wells, dug wells, ponds, stored run off of the Indus and Gomal rivers and perennial streams. This study is aimed to determine the physio-chemical contaminants in the surface and subsurface water which could cause environmental problem. For this purpose, representative water sample were collected from tube wells, dug wells, streams and rivers. These analyses were performed using Hach DR/2000 spectrophotometer and graphite furnace atomic absorption spectrometer. Chemically both surface and subsurface water samples of the area were classified as alkaline fresh water. The comparison of the data with standard limits set by Word Health Organization (WHO) for drinking water suggested that in certain areas of the division, the drinking water samples have high concentrations of Total Dissolved Solids, NO 3 2- , SO 4 2- , F - , Cl - , Fe 2+ , Ca 2+ , Mg 2+ , Pb 2+ , Ni 2+ and Cd 2+ while pH, EC, HCO 3 - , PO 4 3- , Na + , Mn 2+ , K + , Cr 3+ and Zn 2+ were within the permissible limits. These contaminations could be attributed to the geogenic sources which might be responsible for the health related problems in certain areas of the division. Introduction Water quality can be evaluated by physical, chemical and biological parameters. It can be highly affected by wide range of geogenic and anthropogenic sources which indicates a complex variation over different spatial and temporal scales [1-3]. All over the populated part of the earth, the quality of natural fresh water is being disturbed by human activities. This is mainly due to the discharge of the municipal and industrial waste into the rivers. However, the addition of soluble matters from the catchment areas and from fertilizer of crop fields also play a role in contaminating the rivers and hence cause pollution in underground aquifers [4]. The excess of anions, cations and heavy and trace metals in the water because of their toxicity, especially in drinking water, may cause serious environmental health problems such as raising blood pressure, chronic anemia, stomach ramps, nausea, skin irritation, methemoglobinemia and carinogenisis etc. [4-6]. Water pollution in Pakistan, like other underdeveloped countries, is a widespread environmental problem which needs to be properly monitored. The water quality of Dera Ismail (D. I) Khan division has, therefore, been investigated during present study. The Dera Ismail (D.I.) Khan division is situated in the southern-most part of the Khyber- Pakhtunkhwa (KP) province between latitude 31 o 15΄ and 32 o 30΄ N and longitude 70 o 00΄ and 71 o 25΄ E (Fig. 1). It contains two main physiographic units, 1) the alluvial lowlands, which include the structurally undisturbed Indus plains, and 2) the folded belt, which includes the Khisor, Murwat, Bhittanni, and Sulaiman ranges. These ranges and highlands form a nearly continuous mountain system between Salt Range and Potwar Plateau extending to the Balochistan province in the southwest. The climate of the region is sub-arid to subtropical continental lowland type. The average annual precipitation ranges from 290 mm in the hills in the north to 200 mm in Ramak in the south. More than 80% population of the D.I. Khan division is living in rural areas. These people obtain their domestic water from dug-wells and shallow drilled wells equipped with hand-pumps, ponds, stored runoff, the Indus and Gomal rivers and perennial streams. The public Health Engineering Department (PHED) drilled tube- wells for the supply of drinking water in major towns. Indus River forms the eastern boundary of the D.I. Khan division while the Gomal River flows through most parts of the division. The total surface covered by vegetation rarely exceeds ten percent as compared to the whole land [7]. J.Chem.Soc.Pak., Vol. 34, No. 1, 2012 * To whom all correspondence should be addressed.