Document Type : علمی - پژوهشی


1 Department of environmental engineering, University of Tehran, Tehran, Iran

2 Department of Chemistry, Faculty of Science, University of Tehran, Tehran, Iran


Introduction: Nowadays, the study of estuarine zones is essential because more than half of the world’s population is living along estuaries. As a result, estuaries are potentially facing a lot of different pollutants, including heavy metals. For this purpose, estuary conditions must be simulated. Since the formation of estuaries is the result of mixing of fresh river water with saline sea water, they can be simulated by creating different salinity regimes.Materials and methods: this simulation was an attempt to study the behaviour of heavy metals (Zn, Pb, Ni, Cu and Mn) in the estuary of the biggest river of northern Iran, the Sefidrud River that flows into the Caspian Sea. For this purpose, fresh and saline water were mixed in 5 different proportions until salinity regimes of 1 to 3.4 psu were created. After flocs were formed, each of samples was filtered separately by 0.22 -µm Millipore membrane filters. Filters containing the flocs were put in small beakers, and 5 cc of acid nitric was added to the beakers. After 6 hours both filters and the flocs on the filters were digested. The volume of liquid inside the beakers was increased to 10 cc by using 1 N HCl. The metal contents of the metals were measured by ICP. Cluster analysis, a statistical method, was used to determine the effect of chemical and physical parameters on the flocculation process. Results and discussion: Estuaries act as filters to reduce the load of heavy metals in saline water environments such as seas. The present investigation provides a laboratory experimental study of eliminating soluble and colloidal elements of manganese, zinc, lead, nickel and copper during the estuarine mixing of Sefidrud River water with Caspian Sea water due to the flocculation process. The results obtained show that the two elements zinc and lead are, respectively, flocculated at 100% and 0% during the estuarine mixing. Such extremely high and low flocculation is indicative of the conservative and non-conservative nature, respectively, of Pb and Zn.The flocculation rates of copper, nickel and manganese are as follows: Cu (55%)> Ni (41%)>Mn (4%). In other words, various portions of the studied metals are removed during estuarine mixing in the form of tiny flocculants. Statistical analyses indicate that S, E, C, pH and Eh govern the flocculation of zinc. Dissolved oxygen was the only parameter that affected the flocculation of copper. It should be pointed out that the flocculation of nickel and manganese is not governed by S, EC, pH and Eh. Conclusion: estuarine zone has different effects on different metals because of the various forms of the metals and chemical and physical parameters.


  1. Anderson, A.J., 1971. Numerical examination of multivariate soil samples. Journal of the International Association for Mathematical Geology. 3(1), 1-14.
  2. Biati, A. and Karbassi, A., 2012. Flocculation of metals during mixing of Siyahrud River water with Caspian Sea water. Environmental Monitoring Assessment. 184: 6903-6911.
  3. Biati, A., Karbassi, A., Hassani, A., Monavari, S. M. and Moattar, F., 2010. Role of metal species in flocculation rate during estuarine mixing. International Journal of Environmental Science. 7 (2), 327- 336.
  4. Boyle, E.A., Edmond, J.M. and Sholkovitz, E.R., 1977. The mechanism of Fe removal in estuaries. Geochimica et Cosmochimica Acta. 41 (9), 1313- 1324.
  5. Davis, J.B., 1973. Statistic and Data Analysis in Geology. Wiley, New York, pp 456-473.
  6. Day, J., Hall, C., Kemp, W. and Ynez-Arancibia, A., 1989. Estuarine Ecology. New York, U.S.A.: John Wiley.
  7. Fazelzadeh, M., Karbassi, A.R. and Mehrdadi, N., 2012. An Investigation on the Role of Flocculation Processes in Geo-Chemical and Biological Cycle of Estuary (Case Study: Gorganrood River). International journal of environmental science. 6(2), 391-398.
  8. Karbassi, A., Valikhani Samani, A.R., Fakhraee, M., Heidari, M. and Vaezi, A.R., 2015. Effect of dissolved organic carbon and salinity on flocculation process of heavy metals during mixing of the Navrud River water with Caspian Seawater. Journal of Desalination and Water Treatment. 55(4):926-934.
  9. Karbassi, A., Bassam, S. and Ardestani, M., 2013. Flocculaton of Cu, Mn, Ni, Pb and Ni during Estuarine Mixing (Caspian Sea). International Journal Environmental Research.7(4), 917-92.
  10. Karbassi, A. and Heidari, M., 2013. An investigation on role of Salinity, PH and DO on heavy metals elimination throughout estuarial mixture. global journal of Environmental Science Management.1(1):41-46.
  11. Karbassi, A., Nouri, J., Nabi Bidhendi, G. and Ayaz, G.O., 2008a. Behavior of Cu, Zn, Pb, Ni and Mn during mixing of freshwater with the Caspian Seawater. Desalination. 229: 124−118.
  12. Karbassi, A.R., Nouri, J., Mehrdadi, N. and Ayaz, G., 2008b. Flocculation of heavy metals during mixing of freshwater with Caspian Sea water. Environmental Geology. 53(8), 1811–1816.
  13. Lance, G.N. and William, W.T., 1966. A generalized sorting strategy for computer classification. Nature, 212-218.
  14. Meybeck, M., 1982. Nutrients (N, P, C) transport of world rivers. American Journal of Science. 282, 401-450.
  15. Saeedi, M., Karbassi, A. and Mehrdadi, N., 2003. Flocculation of dissolved Mn, Zn, Ni, and Cu during the estuarine mixing of Tajan river water with Caspian seawater. International Journal of Environmental Study. 60(6), 567–576.
  16. Shamkhali Chenar, S., Karbassi, A., Hajizadeh, Zaker, N. and Ghazban, F., 2013. Electroflocculation of Metals during Estuarine Mixing (Caspian Sea). Journal of coastal research. 29(4), 847-854.
  17. Sholkovitz, E.R., 1976. Flocculation of dissolved organic and inorganic matter during the mixing river water and seawater. Geochimica et Cosmochimica Acta. 40 (7), 831- 845.
  18. Zhiqing, L.E., Jianhu, Z. and Jinsi, C., 1987. Flocculation of dissolved Fe, Al, Si, Cu, Pb and Zn during estuarine mixing. Acta Oceanologica Sinica. 6, 567-576.