Determination of BTEX concentration in the groundwater of east region of Isfahan using passive sampling method

Aims: This study was conducted to determine Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) concentration regarding broken petroleum transmission pipeline in the east region of Isfahan, using passive sampling method. Materials and Methods: Dialysis bags as passive sampling devices with molecular cut-off diameter of 12000 Dalton, 3.2 cm width and around 12 cm lengths were used that contain 2 ml of olive oil as an absorbent. These devices were placed, in 10 sampling wells for 45 days. In order to determine the absorption efficiency of these devices, laboratory calibration operations were performed at the same time. Nitrate as an indicator of contamination of groundwater with chemical fertilizers and also electrical conductivity (EC) as an indicator for cations and anions concentration was measured. Results: The laboratory absorption efficiencies of BTEX were found to be 90%, 85%, 79%, and 81%, respectively. Concentration of these compounds in field samples were less than 10 μg/l. Nitrate concentration varied between 2.1 to 69.2 mg/l, and EC varied between 1.7 to 15.1 mS/cm. Conclusion: BTEX compounds were absorbed with high efficiency in the laboratory test, but their concentrations in wells were found to be negligible. Average concentration of nitrate in the wells was less than water quality guidelines, and had no relation with the direction of movement or depth of water. EC tended to increase in the direction of groundwater movement, but there were no correlations among depth of water, nitrate concentration, and mean of EC.X