Ground Water Chemistry and Quality Assessment of the Dibdibba Aquifer at Safwan- Zubair Area, Southern IRAQ

الملخص

Hydrochemical assessment of groundwater was carried out to characterize, classify groundwater and evaluate its suitability for drinking ,irrigation and industrial use in Safwan-Zubair area of south Iraq. Groundwater samples were collected during wet (October ,2016) and dry (April ,2017) seasons from 58 of operated wells (hand dug or tube) for rural water supply using standard sampling procedures. The water samples were analyzed for pH, major ions, total dissolved solids and electrical conductivity (EC), using standard methods. . It was established that groundwater is neutral to alkaline and. The six groundwater types represent (Na2SO4) ,(NaCl),( CaCl2), (MgCl2) ,(CaSO4) and (MgSO4) for both periods. The relative concentrations such as Ca/Mg, Na/Cl, Cl/(HCO3+CO3) and base exchange index are used to assess the salinity of groundwater in the study area. This study shows the origin of the water is Marine except well No.8 where is Metrologic. Hydrographical methods (i.e. Schoeller diagram) and AqQA software geochemical modeling program were used to characterize the groundwater quality. Analytical results of groundwater quality in Safwan-Zubair area indicated that the order of abundance of cation concentration were Ca > Mg < Na+ K and Na+ K > Mg > Ca in dry and wet seasons respectively while those of the anions were Cl > SO4 > HCO3 + CO3 in both seasons .
Groundwater from Safwan-Zubair area was largely supersaturated with respect to both calcite and aragonite , However, the calculated PCO2 values suggested that the groundwater system was open to soil CO2 and that there was possibility of degassing of CO2 during flow, which could increase the pH and subsequently result in the supersaturation of calcite in both districts. Groundwater water samples were stable towards calcite and aragonite stability field. This suggested that equilibrium of the groundwater with silicates is an important indicator of the hydrogeochemical processes behind groundwater quality in the study area. According to the available standards, the present study samples were unsuitable for drinking purposes but adequate for irrigation purposes depending on Electrical conductivity, soluble sodium percentage (SSP), total dissolved solids (TDS), sodium adsorption ratio (SAR), Kelly’s ratio (KR), permeability index (PI) and Magnesium ratio (MAR) values. The values of SAR ,PI , SSP , KR and MAR indicated excellent, good and permissible quality of water for irrigation uses. However, samples with unsuitable SAR (89% during wet season ), doubtful to unsuitable PI (76%during dry season ) , unsuitable KR (25% during wet season ) , The values of MAR During dry 50% of samples and 96.42% during wet fall above the permissible limit of 50 mg/ l indicating the unfavorable effect on crop yield and increase in soil alkalinity and a high salinity hazard values restrict the suitability of the groundwater for agricultural purposes, and plants with good salt tolerance should be selected for such groundwater. A detailed hydro-geochemical investigation and integrated water management is suggested for sustainable development of the water resources for better plant growth, long-term as well as maintaining human health in the study area. while all the samples are corrosive with respect to pH in both seasons period .The corrosivity ratio indicates that all samples are unsuitable for industrial use.