# Long-Term Dynamics of Persistent Organic Pollutants in Water Bodies of the Aral Sea-Syrdarya Basin
### Causes of the Ecological Crisis and Its Consequences
At the end of 1987, the Aral Sea level had dropped by 13 m and reached a critical level of 40 m a.s.l., at which point, the Berg Strait connecting the Small and the Large Aral Sea basins dried up, resulting in the division of the Aral Sea into two water bodies [14; 15; 16]. At the end of 1989, the level of the Large Aral Sea had dropped to 38.6 m a.s.l. The long-term dynamics of the main characteristics of the Aral Sea are shown in Figure 2.  
Figure 2: Water volume dynamics of the Aral Sea [17]. Thus, the unprecedented build-up of irrigated areas in the Aral Sea basin, the diversion of large volumes (one-third) of the water outside the basin through the Karakum Canal, and the almost complete regulation of river flow were the leading factors for the destabilization of the ecological conditions of the vast Aral Sea region [10; 18; 19; 20]. Irrigated agriculture was the main consumer of river water destined for the Aral Sea, accounting for 95% of the water consumption in Central Asia. Over thirty years (1960-1990), about 750-800 km\({}^{3}\) of water did not reach the Aral Sea, of which about 600 km\({}^{3}\) was lost as a result of extensive irrigation [21]. The Aral Sea ecological crisis holds a special place among global disasters and is a consequence of the largest anthropogenic intervention in the natural environment. According to UN experts, the Aral Sea ecological crisis is one of the greatest disasters of the 20 th century. That is why it is called Aral Sea syndrome [5; 22]. Among the scale of degradation of all components of the natural environment of the Aral Sea region, deep changes in the aquatic environment of water bodies stand out as an independent problem. There is no analog in the world where these deep processes and changes took place in the aquatic ecosystem of such a huge lake. The catastrophic drop in the water level of the Aral Sea and the intensive pollution of the entire Aral Sea region caused deep degradation of the natural environment and created environmental, social, and economic problems that are unprecedented in their acuteness and urgency. First of all, they include the death of commercial ichthyofauna and, therefore, the loss of fishery significance of the Aral Sea and other water bodies within the Aral Sea region. Other consequences were fundamental changes in economic activities, employment problems, and migration of the population [23]. It is known that annual catches in the Aral Sea in the late 1950s reached 43,000 tons, on average. During the period from 1930 to 1960, the annual fish catches reached 34,000 tons, and more than 80% of the catches were of valuable fish species: carp, barbel, zander, asp, roach, cherry salmon, and others. The deterioration of the water quality in reservoirs for household and drinking purposes caused a tense sanitary-epidemiological situation in the Aral Sea region, including the deterioration of public health, especially that of children. The decrease in irrigation water quality aggravated the processes of salinization of irrigated lands and reduced crop yields. In total, more than 4 million hectares of land have been degraded in the Aral Sea basin. The level of the Large Aral Sea after its separation (in 1989) from the Small (Northern) Aral Sea is constantly decreasing. The process of its intensive salinization has been continuing; even this lake part is in a state of ecological disaster. The continuing lake level drop has led to the formation of residual reservoirs, i.e., to the partitioning of the lake water area into separate deep-water areas. The dynamics of changes in the Large Aral Sea in recent decades are shown in Figure 3 [24]. The presented images clearly show a dramatic picture of the Aral Sea water mirror area shrinking from the beginning of the crisis to the present day. This reduction has important consequences, both for the ecosystem and for the people living in the region. Overall, the shrinking of the Aral Sea remains a serious environmental problem and its solution requires concerted and long-term efforts at the global level.