ASSESSMENT OF IONIC TOXICITY OF WATER SOURCES IN RAJBARI DISTRICT IN BANGLADESH

Abstract

The study was conducted to assess the degree of ionic toxicity and to classify the water on the basis of standard criteria for irrigation, drinking, livestock, poultry. aquaculture and industrial purposes of 20 ground water sources in Rajbari district. The chemical analysis included pFl, electrical conductivity (EC), total dissolved solids (IDS), sodium adsorption ratio (SAR). soluble sodium percentage (SSP). residual sodium carbonate (RSC) and hardness (111) and major ionic constituents like Ca2 . Mg2 , K. Nat. Fe2t Mn2 , B. Cu. POt, C032'. 11CO3. SOt and Clwere F were also calculated. The pH (6.85 to 7.33) showed slightly acidic to slightly alkaline. The lOS values rated all samples as 'fresh water'. F.0 and SAR were 'medium' and 'high salinity' (C2 and C3) classes and 'low alkali hazard' (SI) class, combined expressed as C2SI and C3SI. SSP was of 'excellent', 'good' and 'permissible' categories. Waters were free from RSC and belonged to 'suitable' category for irrigation. The waters were classified as 'hard'. 'very hard' and 'medium hard' based on hardness (Hi). The toxicitics of Mn and Cu were not found in the study area for irrigation, drinking and livestock but Fe, Cl, SO4 and B toxicitics were found in some sources. Iron content of all samples was suitable for irrigation but 12 samples of Fe were unsuitable for drinking and livestock. Cl concentrations of all samples were below toxic level and thus suitable for irrigation and drinking and all but one sample was suitable for livestock. All samples of NO3 were not toxic for drinking and livestock but all samples of l-lCOj were toxic for irrigation. The following combinations of pH vs SAR, SAR vs SSP Ca vs 11CO3' and Mg vs HCO3- were indicated significant as positive correlations while SSP vs H1 and RSC vs Hr revealed negative significant correlations at 1% and 5% level of significance. To the contrary. the rest combinations showed insignificant correlations. On the basis of major ionic constituents, it was observed that water from pond and deep tube-wells were comparatively better than well waters for irrigation, drinking, livestock and industrial purposes.