Caspian Sea: State of the Environment 2019

Table 4.3: Average concentration of pollutants in atmospheric precipitation at the integrated back- ground monitoring station

Year

Pb µg/l tons/km 3

Hg µg/l tons/km 3

Benzopyrene ng/l kg/km 3

DDT ng/l kg/km 3

HCCHγ-isomer ng/l kg/km 3

Cu µg/l tons/km 3

1987–2016*

0.05–91.0

0.02–376.0

0.05–22.72

1.5–994

0.3–1,397

NA

2012

2.18

2.39

0.46

27.1

BDL**

12.0

2013

2.06

0.38

0.69

134.4

BDL**

13.0

2014

1.55

0.84

0.69

23.2

12.60

7.0

2015

0.92

1.62

0.58

67.2

3.68

1.9

2016

0.48

1.31

1.23

87.7

1.90

1.5

average

1.44

1.31

0.73

67.91

6.06

7.1

from the atmosphere is even higher than that which flows in with the river (Figure 4.9). The volume of precipitation falling on the Caspi- an Sea is about five times lower than the volume of water flowing into it from rivers, and the salin- ity level of the precipitation is approximately 10 times lower than the salinity of the river waters. Precipitation therefore plays a minor role in the salt balance of the Caspian Sea, but the signifi- cance of some of the salts entering the sea (for example, nitrates and phosphates) is not limited to their role in the salt balance; they are much more important as nutrients. The volume of mineral nitrogen entering the sea with precipitation in the water area adjacent to the Russian Federation (7,900 tons per year) is very similar to the volume which is discharged into the sea from the Terek River (Figure 4.10). Precipitation falling on the Caspian Sea therefore plays an important role in supplying nutrients to its ecosystem (a role which is at least comparable to that played by river run-off). In addition to determining ionic composition, the network of Roshydromet stations also mea- sures the zinc concentration in precipitation * limits of variability during observation period 1987–2016 ** below detection limit Sources: Monakhov 2014a; Monakhov 2014b; Monakhov 2015.

samples (Glavnaya Geofizicheskaya Observatori- ya imeni A.I. Voyeykov 2011–2015). Analysis of the available data shows that atmospheric pre- cipitation brings 7,200 tons of zinc into the sea, a comparable amount to that which comes from the Volga River (Figure 4.10). Overall, run-off from the Volga River is the leading contributor to sea pollution from land-based sourc- es in the Russian Federation. In absolute terms, the volume of pollutants entering the sea with river run- off at the beginning of this century was significantly lower when compared with the previous century.

Terek

Volga

Precipitation

Mineral nitrogen

Zinc

Figure 4.10: Intake of mineral nitrogen and zinc from precipitation and from Volga and Terek River run-off (%)

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