Sunday, 26 November 2006

Distribution Of Highly Arsenic And Fluoride Contaminated Groundwater From East Punjab, Pakistan, And The Controlling Role Of Anthropogenic Pollutants In The Natural Hydrological Cycle by Abida Farooqi, Harue Masuda, Minoru Kusakabe, Muhammad Naseem and Nousheen Firdous

This paper reports the extended study from a previously-described study on As and F contaminated groundwater from a small village, Kalalanwala, in east Punjab, Pakistan (Farooqi et al., 2007). Of the 147 groundwater samples investigated, 91% exceeded the WHO standard (10 μg/L) for As and 75% exceeded the WHO standard (1.5 mg/L) for F-. The highly contaminated As (max. 2400 μg/L) and F- (max. 22.8 mg/L) groundwaters were found from shallow depths down to 30 m from the surface. The contaminated groundwaters are characterized by high pH (max. 8.8), alkalinity (HCO3- up to 1281 mg/L), SO42- (max. 960 mg/L), Na+ (max. 1058 mg/L) and maximum electric conductivity >4.6 mS/cm. Fluoride concentrations showed positive correlations with those of Na+ and HCO3- and negative ones with Ca2+ and Mg2+. The alkaline waters were saturated with calcite in spite of the low Ca2+ concentrations. Fluoride concentration is governed by fluorite solubility. Speciation analysis showed As is mostly in the form of AsV. There was a positive correlation between As and pH, while there is no relationship between As vs. Fe and F-. Thus, the fluoride and As contamination occurred in the oxidizing and alkaline conditions of the groundwater. However, F- and As are derived from two or more sources. Suspected contaminant sources in the study area contained considerable amounts of F- and As; fertilizers (DAP, n = 5) contained leachable F- ranging from 53-255 mg/kg, and As 5-10 mg/kg, and coals (n = 8) contained F- ranging from 5-20 mg/kg. Sulfur isotopic ratios indicated that the high SO42- in groundwater (3.2-7.0‰, CDT) is mainly derived from coal combusted atmospheric pollutants, fertilizers and household wastes. Nitrogen isotope data (8-30‰, Air) showed that NO3--N is attributed to animal waste distributed in the study area. The major chemical characteristics of the groundwaters are related with anthropogenic activities on the ground surface. The resultant major chemistry, especially highly alkaline and low Ca2+ and Mg2+ concentrations, must promote the high concentrations of F- and As in the studied groundwaters. 

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