Investigation of changes in organochlorine pesticides and its comparison with previous decades in the southern region of Caspian Sea

The Caspian Sea is a unique brackish system in terms of water salinity, so evaluation of pollution criteria based on the water quality of the same sea is past and present. In this study, information was collected from 2008 to 2010 and analyzed during the project during these years, sampling of eight transects shorelines was performed seasonally at stations 10, 20, 50 and 100 m of depth in two summer and winter seasons for water and sediment. The results showed that the concentration of organochlorine toxins in the aquatic environment depends on its entry through the rivers leading to it and its concentration in water varies in different seasons and regions. The results showed that the concentration of organochlorine pesticides in the aquatic environment increased in winter of 2008 with the highest percentage of pesticides in spring, summer, autumn and winter in middle, middle, east and west and maximum percentages, respectively. Toxins were found in the water samples of the eastern part of the region by 75% in spring. Also the maximum concentration of organochlorine toxin belonged to α-Endosulfan toxin with a concentration of 3.86μg/l which was recorded in Nowshahr at 50 m depth of surface water. Conclusion In the current situation, the concentration of chlorine toxin compounds in the appropriate range and distance from the shore of water quality conditions is more suitable for fish farming in cages. Therefore, it is suggested to consider the establishment of fish cage culture at 50 m of depth.