Concentrations and compositions of aliphatic and

polycyclic hydrocarbons in bottom sediments of the offshore Sakhalin island

Inna Nemirovskaya, G. V. Moyseychenko, Yu. G. Blinov

Close attention paid to the hydrocarbons study in bottom sediments of Sa-khalin shelf as there are active exploration seismo-logy and oil and gas dep-letions development is held in this area (Sakhalin -1, Sakhalin -2 projects).

Bottom sediments accumu-lates the results of long term biochemical processes and unlike water that cha-racterize seasonal or even casual effects for the studied area, the data get from the bottom sediments study gives us the true ecological picture of the sea.

1 4 2 1 4 3 1 4 4 1 4 5 1 4 6

а в г у с т 1 9 9 7 г .

4 8

4 9

5 0

5 1

5 2

5 3

5 4

5 5

3

45

67

9 1 0 1 1 1 2 1 3 1 4

1 5 1 6 1 7 1 9 2 02 1

2 2 2 3 2 4 2 5 2 6

2 8 2 9 3 0 3 1 3 2 3 3

3 4 3 5 3 6 3 7 3 8

4 1 4 2 4 3

4 7 4 8 4 9

5 2 5 3 5 4 5 5 5 6

Р и с . 1 . 1 К а р т а - с х е м а р а й о н а р а б о т .

1 4 2 1 4 3 1 4 4 1 4 5 1 4 6

и ю л ь 2 0 0 2 г .

4 8

4 9

5 0

5 1

5 2

5 3

5 4

5 5

1

23

456

7 8

9 1 0 1 1 1 2 1 3

1 41 5 1 6 1 7

1 8

1 9 2 0 2 1 2 2 2 3

2 42 52 62 7 2 8

2 9 3 0 3 1 3 2

3 3

3 4

3 5

3 63 7

3 8

3 9

4 04 14 24 3

4 44 54 64 7

4 8

4 9 5 0 5 1

5 2

5 35 4

5 55 6

5 75 85 96 06 16 2

6 36 46 56 66 7

6 86 9

7 07 1

7 2

7 3

7 4

7 5 7 6 7 77 8

7 9 8 0 8 1 8 2

8 38 48 58 68 78 8 8 9

9 09 19 29 39 49 5

20 50100

200

20 50100 200

Scheme of studied area with samples collection points

AnalysisAnalysis capillary gas chromatography was carried out on a "Милихром". Gas chromatography-mass spectrometry (GC\MS) analyses were performed on GCMSQP5050A (Schimadzu), than included chromatograph Varian 3400.

Concentrations and compo-sitions of the aliphatic hyd-rocarbons (AHC) and poly-ciclic aromatic hydrocar-bons (PAH) in surface sediments of Sakhalin Is-land shelf were studied in years 1994 and 2002.

Corganic Aliphatic hydrocarbons Polyaromatichydrocarbons

concentration, mkg/g

concentration, mkg/gx* interval

x* interval x* interval

3.5-20.5 0.5-10.3

1.0-7.6 1.5-3.9

1.6-3.12.0-6.2

Lozin 0.06 0.03-0.12 3.0 5 1.8 3.2

Bautin 0.10 0.06-0.14 3.4 3 2.1 2.1

Sakha-lin bay 0.25 0.09-1.56 7.5 3 2.1 0.9

% ofCorg х10-4

% of Corg

Х 10-1

Area

The hydrocarbons’ content and composition in the upper layer of bottom sediments in the Sakhalin island’s shelf

(1994)

The hydrocarbons’ content and composition in the upper layer of bottom sediments in the Sakhalin

island’s shelf (2002)

Corganic Aliphatic hydrocarbons Polyaromatichydrocarbons

concentration, mkg/g

concentration, mkg/gx* interval

x* interval x* interval

3.4-89.9 3.1-58.7

11.9-89.9 15.9-58.7

3.1-33.43.4-54.4

silts 1.07 0.59-1.89 29.5 0.28 34.7 3.2

sands 0.12 0.03-0.32 16.4 1.23 13.1 10.9

All sampl-

es0.39 0.03-1.85 19.5 0.50 15.8 3.1

% ofCorg х10-4

% of Corg

Х 10-1

Area

It was shown that concentra-tions of hydrocarbons changed a little comparing with previous years:

1994 - Corg – 0.03-0.14%; AHC – 1.0-10 ppm;PAH – 0.4-10 ppb;

2002 -Corg – 0.03-1.85%; AHC – 3.4-89.9 ppm; PAH – 3.1-58.7 ppb.

The quantity of hydrocarbon atoms

The higher AHC and PAH concen-tration found in offshore sediments of the Sakhalin Island in 2002, as compared with those in 1994, are most likely related to the different lithological types of analyzed sedi-ments, because hydrocarbon con-centrations (5.4 times, on average) simultaneously increase with chan-ges in Corg contents (6.5 times, on average).

THE QUANTITY

OF THE HYDROCARBON ATOMS

The alcane’s distribu-tion in Sakhalin shelf’s bottom sediments.1 – transformed allochthonic2 – indigenously allochthonic3 – transformed oil

Biogenic sources are mainly responsible for the AHC concentration in muddy se-diments (50 ppm) and coarse-grained fractions (3-7 ppm). Their concentra-tions in the analyzed sam-ples do not exceed these background values.

Hydrocarbons are dominated by allochthonous natural components, which are more stable among the AHCs. At the same time, the presence of transformed anthropo-genic petroleum alcanes, which were not detected previously, im-plies increased pollution related to intensified economic activity in the area under consideration.

At the same time, the presence of transformed an-thropogenic petroleum alca-nes, which were not de-tected previously, implies the increased pollution related to the intensified economic acti-vity in the area of the oil and gas development.

The composition of hydro-carbons in bottom sediments reflects their differentiation du-ring sedimentation, i.e., sorp-tion and biotransformation ra-ther than genesis of initial orga-nic matter. Therefore, the com-position of alcanes in bottom sediments and that of the spil-led oil differ from each other.

In conclusion, it should be noticed that the lithologicaltype of sediments and natural geochemical background of hydrocarbons (concentration of hydrocarbons and their composition) should be taken into the consideration when in-terpreting data on oil pollution in bottom sediments.

This is of principal impor-tance when estimating the results of ecological monito-ring in areas of marine oil and gas deposits where pet-roleum hydrocarbons of both natural and anthropogenic origin can occur.