Caspian Sea: State of the Environment 2019

run-off into the Caspian Sea with the waters of the Volga and Terek rivers (Monakhov 2014a; Monakhov 2014b; Monakhov 2015). During the period 2011–2015, total chemical run-off from these rivers averaged 4.1 million tons of organ- ic substances per year, 72,200 tons of mineral nitrogen, 5,200 tons of mineral phosphorus, 2,000 tons of nickel, 1,100 tons of manganese, 900 tons of copper, 500 tons of lead, 70 tons of aluminium and molybdenum, 20 tons of co- balt, 9.7 tons of cadmium, 2.3 tons of mercury, 16,800 tons of oil products, 400 tons of phenols, 0.5 tons of DDT and 0.7 tons of HCH (Figure 4.4, Table 4.2).

If the effect of the long-term trend resulting from the reduction in polluted wastewater discharge is subtracted from the time series of pollutant run-off, then a directly proportional relationship between pollutant run-off and water run-off can be clearly seen in the remaining fluctuations (smoothed rows or series of annual increments). 2016 serves as an example of this: after a series of low-water years, the water run-off increased by 65 km 3 compared to the previous year, and the volume of oil products dis- charged rose by 33,000 tons (Figure 4.3). Roshydromet’s annual reviews of onshore sur- face water quality include data on pollutant

km 3

thousand tonnes

Volga

Volga

Terek

Terek

Figure 4.5: Volume of water run-off (km 3 ) and amount of organic substances discharged (thousand tons), 2011–2015

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