Appraisal of heavy metal status in water for irrigation usage of the Bangshi River, Bangladesh

An attempt was made to assess the status of heavy metals in the Bangshi River water for irrigation usage. River water was sampled from 20 sampling points for chemical analysis of physicochemical parameters and metal ions. Our analyses revealed that water samples were slightly alkaline to alkaline. All samples had reasonable electrical conductivity, and these samples were from low to medium salinity classes as being fit for irrigation on soils having moderate level of permeability. Water samples were categorized freshwater as per total dissolved solids (TDS). All water samples were excellent indicating low alkalinity hazard, based on sodium adsorption ratio (SAR), but most of the samples were doubtful to unsuitable for soluble sodium percentage (SSP). All samples were free from residual sodium carbonate (RSC) suggesting suitability for irrigation purpose. For water hardness, samples were rated as moderately hard, hard, and very hard. The status of Fe, Zn, Pb, Cd, and Ni in water samples were within permissible levels but Cr, Cu, and Mn content in water samples were in excess of recommended limits and these ions would be considered toxic in long-term irrigation system. Significant relationships existed between EC versus TDS, SAR versus SSP, SSP versus RSC, and SAR versus RSC. There were significant correlations between metal ions: Fe-Cu, Fe-Pb, Cu-Pb, Fe-Mn, Cu-Mn, and Mn-Pb. This finding showed that Cr, Cu, and Mn ions were considered contaminants in river water used for irrigation because the present status of these metals may pose a harmful impact on human health.