...TIIIS PAPER NOT Ta BE CITED WITHOUT PRIOR REFERENCE TO THE AUTHORS

International Council for theExploration of the Sea

CM 1983/E:11Marine EnvironmentalQuality Committee

THE TOXICITY OF ALTERNATIVE BASE-alLS AND DRILL-~ruDS FOR USE IN THENORTH SEA

RAA Blackmnn, T W Filemnn and R J Law

Ministry of Agriculture, Fisheries and FoodDirectorate of Fisheries ResearchFisheries LaboratoryBurnham-on-Crouch, Essex CMO 81IA, England

'.ABSTRACT

A large number of alternative base-oils to diesel and the drill-muds

formulated on them have been tested for acute toxicity to brown shrimp

(Crangon crangon). Most are at least an order of magnitude less toxic

than the diesel equivalent. Mud toxicity seems little altered by exchange

of low-toxicity base-oils or when different muds are formulated on the same

base-oil. Base-oil toxicity cannot always be predi~ted from simple analyses

of its aromatic hydrocarbon content. A preliminary tank experiment indicated

that applications of diesel-based mud over 10 weeksdepressed the settle­

ment of planktonic'organisms on hard and soft substrates to a greater extent

than applications of alternative-based muds.

Un grand nombre d'huiles de base jouant le meme role que le diesel et

les boues de fora ge 'formulees a partir drelles ont ete essayees pour deter­

miner l'effet toxique qu'elles exercent sur les crevettes grises (Crangon

crangon). La plupart sont au moins un degre moins toxique que l'equivalent

du diesel. 11 parait que la toxicite des boues est peu modifiee en substi­

tuant des huiles de base a faible toxicite ou en formulant une serie de

boues a part ir de la meme huile de base. La toxicite d'une huile de base ne

peut etre' toujours prevue en se fondant surde simples analyses de sa teneur

en hydrocarbures aromatiques. Un essai preliminaire de reservoir signala

que des applications de baues a base de diesel au cours de 10 semaines

decourageaient l'etablissement d'organismes planctoniques sur des substrats

tant durs que mous en plus grande mesure que des applications de boues abases alternatives.

1

INTRonUCTION

United Kingdom Government Departments have expressed concern about

the possible extent of eeologiea1 effects around oi1-rigs and p1atforms

from the inereasing quantities of diesel oi1 discharged on drill-mud eut­

tings in the NortH Sea. In response t the oi1 industry has developed and

introdueed alternative base-oi1s. These are refined produets of mueh 10wer

acute toxicity than diesel oil (Blackman~ Fileman and Law~ 1982). A 1arge

number of potential base-oils and the dri11-muds formu1ated on them have now

been tested for acute toxicity and some research carried out into the

re1ationships between the composition t aromatichydrocarbon content and

acute toxicity of the oils.

The deve10pers of alternative base-oi1s have sought refined products of

reduced 10wmo1ecular weight aromatic hydrocarbon content because these

compounds are consideredto be the primary toxins acting in acute toxicity

tests of petroleum oi1s. However, it has been suggested.that the results

cf such tests are of litt1e use in predicting the ecological field effects

of the discharge of dri1l-cuttings covered with oi1-based muds. It has

been further suggested that the substitution of alternative-base muds for

. diesel-based muds will aehieve 1itt1e reduction in benthie effeets beeause

most damage is not due to ehemiea1 toxieity but to anoxia and sulphide

production in areas physiea11y blanketed or organiea11y overloaded with

degradable materials. It therefore seemed useful to see whether differences

in toxie effeet between diesel-based mud and alternative-based muds cou1d

be detecte4 in a simple, inexpensive·microcosm whieh did not attempt to

simu1ate benthieco~ditions around offshore p1atforms,but which wou1d

give some indieations of eomparative effeets on benthie eommunities.

This paper presents some of the resu1ts so far obtained from these studies.

MATERIALS AND METHOnS

Samp1es of base-oi1s and drill-muds were supp1ied by the refining and

mud-formulating companies·for toxicity-testing and chemical ana1yses.

Base-oi1s were dissolved in pentane or dich10romethane for analysis

by u1tra-vio1et fluoreseenee spectroscopy (UVF). Muds und ~ediment samp1es

were mixed with anhydrous sodium sulphate and extraeted under reflux.

Ana1yses were earried out by UVF using a Baird-Atomic SFR-100 Speetrof1uori­

meter, ea1ibrated to 100% with 10 ~g m1- 1 dich10romethane or pentane solution

of reference #2 diesel oi1. Extracts were exeited at 270 and 280 nm and

their emission measured at 330 and 310 nm respectively. Synchronous speetra

(ßA = 25 nm) were also compared.

2

•

Sampies of base-oils were analysed for naphthalene and its alkylated

derivatives by computerized capillary gas chromatography-mass spectrometry

(GC-MS). ml of each oil was pipetted into a 100 ml volumetrie flask

and 1 mg of a fully deuterated internal standard, naphthalene-d8' added.

The solutions were'then made up to 100 ml with pentane,and 1 ~l aliquats

analysed by GC-MS. Injections were made via a cold on-column injectian

onto a 25 m crosslinked fused silica capillary column coated with SE-52

(Hewlett-Packard, Winnersh, Wokingham, Berkshire) in a Carlo-Erba 4160

gas chromatograph. The column temperature was raised during analysis from

60° to 230°C at 5°C min- 1 The column was directly connected to the ion

source of a Finnigan 3200/Incos 2300 computerized mass spectrometer, scan­

ning from 35-400 atomic mass units with a cycle time of 1 s. Data was

acquired for 2000 s for each sampie and the information held on computer

disc foi later processing.

Quantitation was carried out relative to the known weight of internal

standard added to each sampie, ~sing response factors calculated from

analysis of authentie standards for each class of alkylated naphthalenes

determined. In each case.the molecular ,ion was used for quantitation.

The compounds used for standardisation, their molecular ions and the suppliers

were as foliows:

naphthalene-d8

naphthalene

1-methyl naphthalene

mixed dimethyl naphthalene~somers

2,3,5-trimethyl naphthalene

m/z136

128

142

156

170

Merck, Sharp and Dohme,Hoddesdon, Herts

BDH, Poole, Dorset

BDH, Poole, Dorset

Aldrich ChemicalCo., Gillingham, Dorset

Aldrich Chemical Co., Gillingham, Dorset

The calculated response factors relative to naphthalene-da were:

naphthalene, 0.94; C1-naphthalenes, 0.49; C2-naphthalenes, 0.36;

C3-naphthalenes, 0.65.

Toxicity tests on base-oils were carried out at 15°C ± 1°C with brown

shrimp (Crangon crangon) in 20 1 cylindrical perspex tanks fitted with

protected propellers to give constant agitation (Blackman et aZ., 1977).

This maintained an even dispersion of oil droplets without causing undue

stress to the test animals. Results are given as the 96 h LC(I) 50 (Lloyd

and Tooby, '1979) based on the quantities of ail initially added. This

apparatus was not designed to keep sinking particles in suspension and thus

3

could not maintain an even suspension of drill-muds at the necessary concen- :

trations. Unstirred toxicity tests, with daily replacement of the test

materials, were therefore carried out on drill-muds in 10 perspex tanks

using the methods described by Franklin (1980). After experience had been

gained with these methods, test protocols were drawn up so that UK commercial

toxicity-testing companies could carry out, in the prescribed manner, the

large number of tes~s required as new base-oils and drill-muds were developed.

Results obtained from such commercial test data submitted to the MAFF Fisheries

Laboratory for approval have been incorporated In those presented here.

The system used to compare the effects of diesel-based mud and alter­

native base muds in sediments was a modification of that described by

Tagatz, Ivey and Oglesby (1979) where planktonic larvae from in-flowing

natural waters were allowed to settle in tanks or enclosures treated with

drill-muds or their components. In this case the bottom of each 40-litre

polyethylene tank was covered with a 1.8-2.5 cm layer of autoclaved shell,

sand and grit «4 mm diameter) and each provided with a standard sized ~

autoclaved earthenware tile and slate.' Running sea water was adjusted to

450-500 ml min- 1 and regular additions of drill-muds were made during the

10-week experimental period, after which the settled organisms were retrieved

and recorded. The'sea water was drawn from the upper 20 cm of the primary

s~ttling tanks in the laboratorysea water supply. In ,addition, plankton

hauls were made across the surface of these settling,tanks andequal ali-

quots of plankton added to the experimental systems at intervals. Sampies

were taken to thewhole depth of the sediment and mixed before chemical

analysis but in the virtual absence of bioturbation a layer of fines built

up at the sediment surface. The upper 0.5 cm of this was also carefully

sampled at the end of the experiment to determine the maximum sediment

concentrations of oil. The fine sediment, and washings from the underlying

sediment, were sieved to 90 ~m and thc retaincd organisms stained and

picked out. Estimates of very numerous meiofauna were made from equal

subsampies of the fine sediment.

RESULTS AND DISCUSSION

Table, 1 summarizes the data on products considered for use as base-oils

for which information on both toxicity and total aromatic hydrocarbon

content was available. The figures for stated aromatic content usually

refer to an Infra-red absorption method but some of the apparent variation

in content could be due to the use of other methods of analysis. Even by

the UVF method, the contents vary wi?ely and cannot always.be used to

predict thc',acute toxicity to Crangon, despite the yery wide range of acute

toxicities recorded. Nor can the toxicities presented here be used to

4

rank the base-oils with any precision: for instance, oils A and AD are

stated to be identical in composition. However, while the apparent differ­

ence in their measured toxicity may be due to normal experimental varia­

bility, there is a clear difference in toxicity between these oils and

diesel and an even greater difference between these oils and those with6a 96 h LC(I)50 to Crangon of >3000 parts per 10 •

Table 2 summarizes the information available on the acute toxieity of

alternative based,muds submitted for toxicity testing in the UK. All are

of much lower toxicity than the diesel based mud and for most of them

the 96 h LC(I)50 was greater than the highest concentration tested. In

general, muds formulated using the same base-oil have similar acute toxi­

cities, and any apparent variations between them probably reflects the

degree o~ reprodueibility of the test. The acute toxi.city of the base-oil

'4It and of the mud formulated on it bear no striet relationship (Table 3),

even when the same manufacturer's mud solids formula is used with a range

of different ails (Table 4). It would therefore appear that, given some

criteria for acceptable toxicity of base-oils, any acceptable oil product will

g~ve a mud of acceptably low toxicity,whatever thesolids formula.

Conversely, the wide range in base-oil toxicity eompared to the uniformly

low toxicity of the muds formulated on them, prompts the question whethcr

this type of toxicity test is applicable to·the formulated muds and

whether other types of acutc toxicity test, or tests for long-term effects,

would not show differences bctween muds formulated on very different base-oils.

Total ion chromatograms from the GC-MS illustrate the range of basic

types of oil product submitted for use as base-oils (Figs. 1-3). Most are

simple distillation cuts over very similar ranges followed byvarying degrees

~ of refining. Some (e.g. Figure 3a) are blends of two oils. Figure 3b is

the chromatogram of a highly refined de-waxed oil.

Analysis of the base-oils for naphthalene and substituted na~hthalenes

showed some correlation between high total naphthalenes (>2g 1-1) and high

toxicity (96 h LC(I)50 < 1000 parts per 106) but there are still exceptions

(Table 5)'. The naphthalene composition varied markedly, more highly

refined productsgenerally containing lower proportions of C2- and C3

­

naphthalenes and having lower toxicities. For instance, oil R was derived

from the same source - a distillation cut of a naphthenic erude oil ­

asoilAC, but the formerhas been subjected to additional solvent ­

refiningt~ lower the aromatic content. Oils C and D are said to be derived

from the same,source and to have been through the 'same refining process,

5

but oil C contained added aromatic hydrocarbons to promote emulsification.

The addition was registered by UVF and by other methods for measuring

total aromatic content but material added was not high in naphthalenes

and produced little difference in acute toxicity. ails AC and E, from

the same refiner, 'showed a large difference in naphthalene content, parti­

cularly the C2-naphthalenes, with a corresponding difference in toxicity

and total aromatics by UVF but not by IR. Since C2-naphthalenes form over

half the total naphthalene content of diesel oil, it is tempting to conclude

that these largely determine the acute toxicity and that C2-naphthalenes

should be avoided in selecting base~oils, but the toxicity of several oils

in Table 5 seems unconnected with their C2-naphthalene content. A further

example is given in Table 6 which shows the result of blending oil E with a

ES 2869 ~uel ail to give oils X and Y. A great increase in naphthalene and

C1- and C2-naphthalenes is reflected in their increased toxicity despite the ...

total naphthalene'contents of oils E and X being similar.

The characteristics of the drill muds and sediments used in larvae

settlement experiments, are summarized in Table 7 and the results in Table 8.

The results indicate a difference between those tanks (la, Ib) treated with a

suspension of drill solids from mud 17 in water and those treated with fully

formulated oil-based muds. Differences between Ia and Ib can largely be

ascribed to Ia being nearest to, and Ib, being furthest from, the sunlight

illumination. The Anthozoa, sponges and ascidians settled almost entirely

on the undersides of the slates. The algae on the tank walls settled mostly

near the wa~erline providing a near surface habitat for most of the copepods

and hydrobiids. Both habitats were largely protected from direct exposure

to the drill-mud additions. A distinction therefore has to be made betwecn

the direct sediment effects of exposure to drill-muds, reflected in the other ~settled organisms, and the indirect effects on the sheltered habitats.

The results also indicate an overall difference in the degree of settle­

ment which occurred between tanks receiving diesel-based mud (IVa, IVb) and

those receiving the alternative based muds. Although numbers are too small

to allow comparison of the numbers of each group of organism which settled

the absence of most organism types from diesel-based mud tanks is considered

to be significant. Whether this difference is maintained at lower sediuient

hydrocarbon concentrations remains to be seen. The treatment rates were

calculated to produce roughly 1000 ppm of base-ail if each addition were

mixed into .the sediment provided. Iiowever the rate of oil breakdown was

much less -than expected, leading to higher concentrations than this by the

end of the experiment.

6

•

•

. There did not appear to be mueh differenee in effeet between the

mud 1 in tanks lIla, IIIb and muds 7 in tanks IIa, IIb and 13 in tanks Va,

Vb respeetively despitc their very different aromatie hydroearbon eontents.

}fuds 7 and 1 were more viseous when shaken in sea water and spread over the

tank floor than the diesel mud and mud B, tending to remain as stieky

pellets. Mud globule size, and henee surface area, and the separation

between globules must affeet the rate and degree of leaching of soluble

toxins in both acute toxicity tests and long-term exposures.

Mud 13 seemed to affect sponges and anthozoa adversely, but muds 7 and

may benefit sponges under these conditions. Tanks containing muds 7, and

the diesel-mud showed the formation of heavy algal und some fungal mats on

the sediment surface and some blackening of patches of fine sediment. These

conditions may have provided Iarger quantities of micro-organisms to serve

as food for the sponges in tanks containing muds 7 and 1.

lt remains unc1ear whether the differences in acute toxicity recorded

bctween base-oils, as measured ~n tests with Crangon arangon and to be

expected from the ,varying contents of naphthalenes and total aromatics, are

realisedin the muds formu1ated on themonce a significant reduction in

toxicity by comparison with diesel based muds has been'obtained. At present

there seem no obvi~us grounds for distinguishing between the "environmental

safety" of base-oils and muds .that are >10-30 times 1ess toxie than their

diesel equivalent, and thus the use of an aeute toxicity test to Crangon

under statie conditions to measure this difference appears to be justified.

REFERENCES

BLACKMAN, R. A. A., FILEMAN, T. W. and LAW, R. J., 1982. Oi1-based drill­

muds In the' North Sea - the use of alternative base-oils.

lCES CM 1982/E:13, 8 pp. (mirneo).

BLACKMAN, R. A. A., FRANKLIN, F. L., NORTON, M. G. and Wilson, K. ,.;r., 1977.

New procedures for the toxicity testing of oi1 slick dispersants.

Fish. Res. Tech. Rep., MAFF Direct. Fish. Res., Lowestoft, (39), 1-7.

FRANKLlN, Franees L., 1980. Assessing the toxieity of industria1 wastes,

with particular rcfercnce to variations in sensitivity o[ test animals.

Fish. Res. Tech. Rep., }~FF Direct. Fish. Res., Lowestoft, (61), 1-10.

LLOYD, R. and TOOBY, T. E., 1979. New termino1ogy required for short term

static fish bioassays: LC(I)50. Bu11. Environm. Contam. Toxico1.,

22 (1)., 1-3.

TAGATZ, M; E., lVEY, J. H. and OGLESBY, J. L., 1979. Toxicity of drilling-mud

biocides to deve10ping estuarine macrobenthos communities. Northeast

Gulf Sci., 3 (2), 88-95.

7

TABLE 1. Aromatic content of alternative base-oils (as stated and by UVF

against a diesel-oil standard) and their toxicity to Crangon crangon (96hLC(I)50

under constant agitation conditions).

Oiltype

#2 DieselGas-oily

ACJAAA

XB

ADABZ

VF

EH*

AEoIC

D

Qp

R

Stated % aromaticcontent

25NA1210.71112.91110.54.5

194.69.45.53.39.60.20~2

7.00.81.5

3.3-4.00.9

NA0.9

NA

UVF at270/330 llm

10082.42522389061276.7

703.3

52"11

6.72.12.40.4

0.070.37.3

<0.011.40.082.5

UVF at280/310 llm

10081.7

2846

75.2

9.885

3.5

169.82.63.81.4

0.59.40.84.7

4.7

Toxicity(parts per 106 )

6-2225505060

110110130300-1000330690

>1000>1000

1000-20002000-3300

4000>3300

3000-10000>6000

6000-10000~10000

~10000

>10000>10000

•

* Two different samples

NA Not available.

Not measured.

TABLE 2. Toxicity of alternative based muds (96hLC(I)50 to Crangon ~rangon

from semi-static tests in parts perl06 )

Mud Base-oil Toxicity Mud Base-oil Toxicitytype type type type

Diesel 110-190 13 F >100001 A >3300 14 F >10000

39 AD 1000-10000 15 F >100002 B ~10000 16 F >100003 B ~10000 17 F >100004 B >10000 18 F >100005 B >10000 19 70%F/30%E >10000

29 B >10000 20 G >100006 C >10000 21 H >10000

28 ,C >10000 24 K >5000• 40 C 4000->10000 25 L >500046 C >10000 34 L >10000

7 D 3000-10000 26 M 5000-1000030 D >10000 27 N 500031 D >10000 49 N >560048 D >5600 44 Q >10000

8 D ~10000 32 S >100009 E >10000 33 T >10000

10 E >10000 37 50%F/SO%V >1000011 E >10000 45 V 700012 E >10000 38 W >10000

TABLE 3. Toxicity of some alternative base-oils and of the muds formulated on

. 6them (96h LC(I~50 to Crangoncrangon in parts per 10 )

Oiltype

DieselA

ADBV

FE

HCD

Q

Oil toxicity inagitation conditions

6-22110330300-1000

>10001000-20002000-3300

40006000-10000

?10000~10000

Mud toxicity inagitation conditions

34-80330

580

>10000

Range of mudtoxicitiesin semi-static conditions

110-190~3300

1000-10000. ~10000

7000>10000>10000>10000

4000-100003000->10000

>10000

No test.

II

I·I

I

L

TABLE 4. Toxicity of same alternative base-oils and of the muds formulated

on them using the same manufacturer's mud solids formula (96hLC (I) 50 to Crangon

crangon in parts per 106 )

Solids system Mud Base-oil Mud toxicity in Base-oil toxicity intype type type semi-static conditions agitation conditions

Alpha 3 B ~10000 300-10007 D 3000-10000 ~10000

9 E >10000 2000-330032 S >1000033 T >1000034 L >1000040. C 4000-10000 6000-10000

Beta 29 B >10000 300-100038 W >1000046 C >1000048 D >5600 ~10000

49 N >5600

Gamma' 18 F >10000 1000-200044 Q >10000 ?1000045 V 7000 >1000

No test

•

TABLE 5. Toxicity of alternative base-oils to Crangon crangon under agitation

conditions, their stated total aromatic content and that measured by UVF at 270/330nm,

and their content of naphthalenes by GC-MS (g 1-1)

Oil 96hLC(I) 50106 )

Stated % UVF (%diesel N C1-N C -N C3

-N ~Ntype (parts per aromatics equivalents)

2

Diesel 6-22 25 100 0.59 4.9 15 7.3 27.79

AC 50 10.7 22 0.09 0.53 3.2 1.4 5.22

y 50 12.3 25 0.42 1.2 1.3 1.2 4.12

J 60 11 38 <0.01 0.36 3.6 5.7 9.66

AA 110 12.9 90 <0.01 0.04 0.84 1.8 2.68

~ 110 11 61 0.06 0.60 3.2 2.8 6.66

X 130 10.5 27 0.14 0.39 0.50 1.5 2.53

AD 330 19 70 0.11 0.82 2.8 2.6 6.33

B 300-1000 4.5 6.7 <0.01 <0.01 0.04 0.07 0.11

AB 690 4.6 3.3 0.27 1.2 2.0 0.13 3.60

F 1000-2000 3.3 6.7 <0.01 <0.01 <0.01 <0.01 ND

V >1000 5.5 11 <0.01 <0.01 0.02 <0.01 0.02

Z >1000 9.4 52 <0.01 0.01 0.57 0.99 1.57

E 2000-3000 9.6 2.1 <0.01 <0.01 0.12 1.8 1.92

H 4000 0.2 0.4 <0.01 0.10 0.02 <0.01 0.12

0 3000-10000 0.8 0.07 <0.01 <0.01 0.03 <0.01 0.03

I >6000 1.5 0.3 <0.01 <0.01 <0.01 <0.01 ND

eC 6000-10000 4 7.0 <0.01 0.02 0.15 0.05 0.22

~10000 1.4 <0.01 <0.01 <0.01 <0.01 NDQ

D ~10000 0.9 < 0.01 <0.01 0.02 0.38 0.14 0.54

R >10000 2.5 <0.01 <0.01 <0.01 <0.01 ND

ND - Not detected

TABLE 6. The effect of oil blending on composition,naphthalenes content (g 1-1 by

GC-MS)and toxicity (96hLC(I)50 to Crangon crangon under agitation conditions in

parts per 106).

Oil % Total UVF N C -N C -N C -N ~N ToxicityAromatics (%)*

1 2 3type

(by IR)

E 9.6 2.1 <0.01 <0.01 0.12 1.8 1.92 2000-3000

X(89% EI11 % Fuel oil) 10.5 27 0.14 0.39 0.50 1.5 2.53 130 •Y(70% EI30% Fuel Oil)

Fuel Oil

12.3

18.5-20

25

9.0

0.42

1.4

1.2

5.2

1.3

3.7

1.2 4.12

0.10 10.40

50

«50

I

I

I

b

*% Diesel oil equivalents by UVF at 270/330nm.

TABLE 7. Characteristics of drill-muds used in a larval settlement experiment (Aromatic

content as % diesel equivalents by UVF; toxicity as 96hLC(I)50 to Crangon in parts per 106 )

-1and the measured sediment concentrations of oil (~g g wet weight diesel equivalents by

UVF) •

Tank Mud Mud Mud Mud Base-oil Sediment Concentrationstype S.G. Aromatic toxicity * toxicity Day 0 Week 3 Week 10 Week 10

Content Mixed Mixed Mixed Surface

Ia }17

513 11 35

(Solids 1.46 15only

Ib in 16 12 19

e water)

Ha} 16 18 357 1.48 2.3 3000- ~10000

10000IIb22 17 110

IIIa) 260 160 58001 1.62 40.5 . ~3300 110

IIIb .. 1900 680 3800

IVa 3 620 320 8100Diesel 1.3,4 78.1 110-190 6-22

IVb 760 150 9300

~}65 90 530

13 1.20 5.3 >10000 1000-2000 72 94 590

---

* From previous laboratory samples.

-------- - --------- ~-- ~ ------- --------------------------

TABLE 8. Total numbers of organisms settling in tanks exposed to successive additions of drill-muds over 10 weeks.

Organism Tanks receiving:

Mud Solids Only Alternative based muds Diesel-based mudIa Ib IIa IIb IIIa IIIb Va Vb· IVa IVb

Red alga~ + + +Brown algae + + +Harvested green algae(Total dry wt. in g.) •60.64 50.55 50.68 55.09 46.57Hydrobiids 124 77 31 41 45 44 56 35· 21 49Anthozoa 165 275 133 ·73 159 119 50 33 158 152Sponges 39 56 96 283 103 35 1 20 26 55MytHus 9 5 4 1 6 2 6 4Barnac.Les 2 5 2 3 5 1 1Polychaetes 3 3 1 3 2 1Eggmasses 2 1 7 2 1 2Crepidula 3Tellinids 2 1 1 1Ascidians 5 4Ostracods, type I + +Ostracods, type II + +Copepods, type I J (in many many few few many several many saveralCopepods, type II sediments) +Nematodes many numerous

(. numerous > many > several >few)

+ present but not counted

not found..

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Figure 1 Total ion Ge-MS chromatograms for diesel oi1 and a disti11ation-cut alternative base-oi1with mild hydro-su1phurisation and solvent refining:

(a) dieseloH.

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Figure 1 Total ion GC-MS chromatograms for diesel oil and a·distil1ation-cut alternative base~il

with mild hydro-sulphurisation and solvent refining:

(b) oil AB. .. .

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Figure 2 ~otal ion GC-MS chromatograms for two distillation-cut alternative base-oils:

(a) oil B.

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Figure 2 Total ionGC-MS chromatograms for two distillation-c~t alternative base-oils: , .

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Figure 3 . Total ion GC-MS chromatograms for a blended oil and a highly-refined de-waxed alternativebase-oi!:

(a) oll AC.

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Figure 3 Total ion GC-MS chromatograms for a blended oi1 and a high1y-refined de-waxed alternativebase-oil:

(b) oil 1.

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