Caspian Sea: State of the Environment 2019

5.4. Sediment quality The quality of bottom sediments is determined by the complex processes involved in the deposition of pollutants and the dynamics and chemical and mechanical composition of bottom sediments,. The distribution of pollutants in the bottom sedi- ments of the Caspian Sea is therefore uneven. In 2016, Jamshidi and Bastami (2016) studied con- centrations of metals, including arsenic, cadmium, copper, chromium, cobalt, vanadium, nickel, lead and zinc, in sediments from the Anzali Wetland in relation to sediment properties. Statistical analysis revealed that aluminium and iron are effective fac- tors in the distribution of metals on the sediments. The results implied that aluminium and iron are probably responsible for transporting heavy met- als into the Anzali Wetland sediments, which have a 21 per cent probability of toxicity. Jamshidi and Bastami (2016) also found that concentrations of nickel, arsenic, chromium and

copper were higher than the permissible levels stipulated in the Sediment Quality Guidelines (United States Environmental Protection Agency [EPA] 2019).This could lead to some organisms being poisoned, and the Anzali Wetland is facing the possibility of significant damage to the envi- ronment as a result of metal pollution. The uneven distribution of pollutants in the bot- tom sediments of the Caspian Sea is evidenced by pollution data for the bottom sediments of the Northern and Middle Caspian, published in the Kazhydromet State of the Environment of the Kazakhstan Part of the Caspian Sea Fact Sheet (Kazhydromet 2011; Kazhydromet 2012; Kazhydromet 2013; Kazhydromet 2014; Kazhy- dromet 2015; Kazhydromet 2016) and a similar publication dedicated to the Aktau Seaport spe- cial economic zone, obtained by analysing sed- iment samples taken at coastal stations, along long-term cross sections and near oilfields on the shelf of the Northern (Atyrau Region) and Mid- dle (Mangystau Region) Caspian.

Table 5.9: Pollutant concentration ranges in bottom sediments of the Caspian Sea (μg/g)

Sampling site/ Indicator

Chrom- ium6+

Manga- nese

Cad- mium

Zinc

TPHs

Copper

Nickel

Lead

2.1–2.2

Ural-Caspian Canal

232–237

0.5–0.7

0.1–0.2

1.37–1.46

5.1–5.2

0

0

2.0–2.5

Tengiz oilfield

224–247

0.6–1.0

0.1–10.9

1.37–1.48

4.2–5.5

0

0

Ural River coastal waters

2.1–2.8

210–275

0.8–1.2

0.2–0.8

1.25–1.43

2.56–6.40

0

0

Shalygi-Kulaly long- term cross section

2.4–3.0

211–345

1.0–1.2

0.1–0.6

1.39–1.99

2.4–4.2

0

0

Additional cross sections A and B

2.0–3.0

215–268

1.1–1.3

0.8–1.0

1.25–2.00

3.6–4.2

0

0

Middle Caspian stations

0.001– 0.002

0.09–0.14

140–160

0

0.01–0.0

0.03–0.05

1.11–1.20

-

Near oil and gas fields on the shelf Long-term cross sections in the Middle Caspian

0.08–0.09

190–220

0

0.01–0.0

0.047–0.28

0.18–0.21

0

-

2.0–3.0

226–312

1.0–1.3

0.8–1.0

1.25–2.00

3.55–4.25

0

-

Source: Kazhydromet 2017a.

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