Assessment of groundwater quality and Arsenic (As) contamination in Qayyuma

تاریخ : جولائی ۲۰۱۸ - جنوری ۲۰۱۹

<p>The aim of the study is to assess the groundwater quality for drinking purpose. Qayyumabad and its surrounding areas were selected as study sites. Twenty groundwater samples were collected from wellbores at various depths (12-300feet) from both banks of the Malir River. Water quality was assessed through the estimation of physical parameters including, pH, Eh, TDS, EC, hardness, temperature, taste, color and odor while chemical parameters included major cations (Na, K, Ca, Mg), anions (Cl, NO₃, SO₄, HCO₃) and minor/trace elements (Fe, As). Groundwater of study area has very high TDS content (805-40340mg/l) and EC (1610-80680 µS/cm) while Eh is found to be negative showing reducing condition (-180 to +125 mV). PH varies in the range of 6.557.75. Major cation solutes varied in the order of Na (mean: 2587mg/l) > Mg (433mg/l) > Ca (231mg/l) > k (91mg/l) while anions span in the order of Cl (3385mg/l) > SO₄ (580mg/l) > HCO₃ (343mg/l) > NO₃ (11.43mg/l). Both arsenic and iron contents occur within the WHO permissible limits except sample 09 which showed elevated Fe (4950ppb) and sample 16 which has As (100ppb). Physio-chemical results suggest that groundwater along the Malir River is not suitable for drinking purposes. Principal component analysis (PCA) revealed four factors where F1 suggest the leaching of salts, F2 indicated decomposition of organic matter creating reducing conditions, F3 suggest water rock interaction and F4 explains the prevalence of anoxia and arsenic release. Result of Water quality index (WQI) is 138 which suggests that the groundwater is very poor and it is restricted to use for irrigation and also unfit for drinking.</p>