Study of heavy metals in urban runoff

A cross-sectional survey was conducted through Tehran city and a field study was conducted to prepare main and accessory drainage channels map. Three main drainage channels were identified for this research and some sampling stations were chosen. Three stations selected in south of Tehran. The reason for selecting these stations is that all urban surface runoff completely pass through these points and samples taken from these points are representative of all kinds of pollutants that transit from city surface. Another Three stations were selected in center and further three stations were selected at north of Tehran. Surface runoff flow in three main channels, from north to south of Tehran, converge at south of Rey city and finally end up to Ghom Salt lake. The stations were chosen at three trajectories, Sorkhe Hesar, Emad Avard, Kan. At each month two samples were prepared from nine different stations. After collection of samples with respect to standard methods, they were dissolved in nitric acid and then analyzed by atomic absorption device. The results show that the concentrations of pollutants increased from north to south. For instance, Zinc had most concentration with monthly average of 0.98 mg/l and Nickel had the lowest amount with 0.02 mg/l in southern stations. Average concentration of Zn, Pb, Cd, Cu and Ni were: 0.638, 0.097, 0.04 and 0.035 mg/l respectively. Total average concentrations of heavy metals at three main channels were of 0.177, 0.176 and 0.145 mg/l. Emad Avard was the most polluted channel.