Guidelines for the use of dispersants for combating oil pollution at sea in the Mediterranean region
Yüklə 454,96 Kb. Pdf görüntüsü
|
- Bu səhifədəki naviqasiya:
- Table 7: Effectiveness tests parameters
- Figure 15: the Labofina / WSL test apparatus
- Figure 16: The IFP / flow through test apparatus (source SINTEF)
Guidelines for the use of dispersants for combating oil pollution at sea in the Mediterranean region Part II: Basic information on dispersants and their application – Page 22
Table 7: Effectiveness tests parameters Test ID
Energy source
Energy level
Water volume
Oil/water ratio
Dispersant application method Dispersant/oil ratio Settling time IFP
Oscillating hoop
1-2 4-5
1:1000 Dropwise variable 1
Labofina rotating flask Rotating vessel 3 0.25 1:50 Dropwise 1:25 1
flask Shaker
table 1-2
0.12 1:1200
Premix/dropwise 1:10 to 1:25 10
Among the main effectiveness laboratory test procedures:
funnel in rotation to provide strong energy to promote the dispersion process (ref to WSL Report LR448. appendix A).
which the water is renewed in order to reproduce the dilution which would occur at sea; in this test the mixing energy brought by a wave generator remains gentle (ref: French standard AFNOR NFT 90-345).
The Swirling test, used in North America, carried out on oil samples premixed which dispersant in a very small funnel which rotate gently to promote the dispersion process (ref . ASTM F2059 - 06 Standard Test Method).
The MNS is a very high energy test used in Norway .
Figure 15: the Labofina / WSL test apparatus Guidelines for the use of dispersants for combating oil pollution at sea in the Mediterranean region Part II: Basic information on dispersants and their application – Page 23
Figure 16: The IFP / flow through test apparatus (source SINTEF)
Figure 17: The swirling flask test method (source: www.marinemanagement.org.uk/protecting/pollution/documents/approval_lr448.pdf )
Figure 18: The MNS test apparatus
At last, when a vessel is on site, it is possible to assess the oil dispersibility by collecting a sample in a glass jar directly from the slick and by testing it in the field. The field test procedure consist in comparing the dispersion of a sample containing dispersant and oil and one containing only oil following manual agitation (hand checking). (e.g. National Plan Oil Spill Dispersant Effectiveness Field Test Kit - Nat-DET ). Such tests can be useful to oil spill responders to decide on the opportunity of applying dispersant on oil which degree of weathering is unknown. Guidelines for the use of dispersants for combating oil pollution at sea in the Mediterranean region Part II: Basic information on dispersants and their application – Page 24
9.2 Toxicity tests
Test materials are usually dispersants, dispersed oil (oil/dispersant mixture) and sometimes oil alone. Test species could be fish, arthropods (usually decapod crustaceans), molluscs (pelecypods), annalids (polychaetes) and algae. Ideally, test species should be selected among locally significant populations. Tests may be acute (short term) single species, lethal or sublethal.
The main goals of these tests are to determine the relative toxicity of a certain dispersant versus other previously tested products.
Due to the increase of toxicity with the increase of temperature, toxicity tests should take into consideration expected changes in seawater temperature.
Measure of the Lethal Concentration 50 (LC 50 ) in a determined period (usually 24 or 48 hours) is a common criteria used in toxicity tests.
Toxicity testing issue can be considered from two different approaches: (i)
either, checking the intrinsic toxicity of the dispersant in order to reject the most toxic ones, in that case only the dispersant is tested;
(ii)
or, checking that the dispersant does not increase the oil toxicity; in that case the tests are performed on the oil alone and on the oil and dispersant mixture.
Due to the fact that dispersing the oil in the water column lead to increase the oil toxicity of oil towards the animals living in the water column, the toxicity of the mixture oil and dispersant should be higher than the one of the oil alone. The more efficient the dispersant, the more toxic the mixture of oil and dispersant may appear as the oil will be better dispersed. Therefore, such approach can be more restrictive and eventually reject the most efficient dispersant. This is in contradiction with the goal of an approval procedure which should be designed to select the more efficient and less toxic ones.
Considering the objectives of the approval procedure (selection of the best products, i.e. the less toxic ones), the control of the intrinsic toxicity of the dispersant is sufficient. However the issue of the toxicity of the dispersed oil remains a concern when considering the policy for the use of dispersants. The toxicity of the di spersed oil (toxicity of the “oil and dispersant” mixture)
is required when defining scenarios (environmental conditions) for which the use of dispersant will remain environmentally acceptable (e.g. part of the NEBA process).
Among the main toxicity tests procedure: The test procedures in force in United Kingdom : o the sea test -comparison on brown shrimp of the toxicity of the oil with and without dispersant- o the rocky shore test – effect of the dispersant on the common limpet- ref:
MAFF
Fisheries Research Technical Report Number 102.
The test procedure used in France: comparison of the LC 50 (6h) of the dispersant alone with the one of a reference toxicant on white shrimp. (ref French standard NF T90-349).
shrimp to concentrations of the test product and No. 2 fuel oil alone and in a 1:10 mixture of product to oil
(ref:
http://www.epa.gov/osweroe1/docs/oil/cfr/appendix c.pdf )
Yüklə 454,96 Kb. Dostları ilə paylaş:
|