## 3 Results and Discussion
### Ecological Conditions of the Caspian Sea
#### 3.3.3.1 Pesticide Contamination  
According to the results of studies [52; 61], organochlorine pesticides-metabolites of DDT and isomers of HCH are registered in the water of the Caspian Sea. In the north-eastern Caspian Sea in 2003-2005, HCH isomers were found in all analyzed samples, but their concentration is low. The most contaminated section with pesticides is the northwestern zone of the Kazakh sector, which is under the influence of the Volga River inflow. More elevated concentrations of DDT metabolites in 2004 were registered in the water between the Volga River and the Ural River. During spring 2005 the content of pesticides was decreased compared to previous years. The main results obtained in 2008-2010 are presented in Table 4.  
Attention is drawn to the presence of DDT metabolites in the water of the entire surveyed Caspian Sea area. Their concentrations are quite high in spring, up to 14.20 \(\upmu\)g/L and in summer up to 22.48 \(\upmu\)g/L. The analysis of the spatial distribution of HCH and DDT allows us to identify three areas where increased concentrations of these pesticides were registered. First: the Caspian Sea area affected by the inflow of the Volga and Ural Rivers, where increased concentrations were recorded only in spring of HCH 1.11-2.0 \(\upmu\)g/L, DDT 7.80-49.80 \(\upmu\)g/L. The second sector covers the southern and south-eastern section of the Northern Caspian Sea. In this zone, the maximum concentrations of HCH 1.70 and 2.08 \(\upmu\)g/L were recorded in spring, and DDT metabolites during summer and spring in the range of 7.00-22.48 \(\upmu\)g/L. According to specialists of Caspian Fisheries Research Institute [50], the presence of local areas with increased concentrations of pesticides is a consequence of the atmospheric transport and dynamic dispersion. The increase in the concentration of pesticides in the water of this zone can also be explained by the fact that it tends to be geographically to the Kulalinskiy deep water area, within which there is an active sedimentation and deposition of a significant proportion of airborne toxic materials in the convergence of water streams from the eastern and western parts of the Northern Caspian Sea. The third area is the eastern coast of the Middle Caspian Sea near the border of Turkmenistan, where DDT concentration reached 9.10-10.8 \(\upmu\)g/L. The presence of DDT and HCH in the water of this area was also revealed by the research of the Caspian Fisheries Research Institute. These facts are explained by the authors both by the arrival of pesticides with drainage drains and dry and wet depositions from the atmosphere. Thus, our research has determined the facts of continuing pesticide contamination of the Caspian Sea at the present time, despite the fact that the use of these classes of pesticides in agriculture has been prohibited long time before. The impact of these contaminants of high potential toxicity into both the tributaries and the Caspian Sea waters is probably \begin{table}
\begin{tabular}{c c c} \hline \hline
**Period** & **Northern Caspian Sea** & **Middle Caspian Sea** \\ \hline  & HCH (\(\alpha\), \(\gamma\)) & \\ \hline Spring, 2008, 2009, 2010 & 0.59 & 0.35 \\ \hline Summer, 2008, 2009, 2010 & 0.12 & 0.08 \\ \hline  & DDT (4.4 \(\upmu\) 2.4) & \\ \hline Spring, 2008, 2009, 2010 & 7.51 & 7.82 \\ \hline Summer, 2008, 2009, 2010 & 5.59 & 4.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average pesticide concentrations in the Caspian Sea water, in \(\upmu\)g/L. due to their high resistance to biodegradation and a long half-life especially under the dry conditions of the semi-arid and arid climate of the northern and eastern Caspian Sea areas, which, according to various authors, ranges from 7 to 38 years. Therefore, experts conclude that the water contamination by pesticides is and will be still a great danger [62]. In 2004-2005, we subjected small fish and sturgeon to toxicological analysis. The results are presented in Table 5.  
In 2004, no HCH isomers were founded in the muscles of _Acipenseridae_ species.