Development and Validation of Robust Satellite Techniques (RST) for Oil Spill Detection and Monitoring

Chapter one Introduction 
NRT monitoring of oil spills may, in principle, be provided by optical 
satellite packages having higher repetition rate but, up to now, no 
techniques really suitable to automatically detect oil spill presence with 
sufficient accuracy and reliability have been proposed. A new technique 
based on the general RST (Robust Satellite Techniques) approach 
(Tramutoli, 1998, 2005) is presented in this work that is finalized to 
detect, automatically and timely, the presence of the oil spill on the sea. 
The results achieved during these three years applying the RST approach 
on validated oil spill events and using optical satellite data, will be 
described here. These results surely confirm that the use of the sensors 
onboard of the meteorological satellites, thanks to their high repetition 
rate, could represent a good alternative chance for the oil spill detection 
and monitoring. 
Besides, considering the increase on new research fields, that try to 
harmonise GIS (Geographic Information Systems) technology and 
different remote sensing technologies, could be a key component to create 
new systems and platforms to support all those final users really involved 
in the emergencies management and responses. 
2
Chapter tw0 The oil pollution problem of the seas 
Chapter two 
The oil pollution problem of the seas 
2.1 - Introduction 
Oil pollution is one of the most serious threat for the seas. The main 
cause of oil spills is due to the human activity and namely by the presence 
of the oil industry. 
The presence of the oil industry has meant a real social and 
environmental impacts, from the accidents and intentional damage as 
instrumental terrorism and warfare, to the routine activities (as leakage 
during normal conditions), the seismic exploration and polluting 
perforations and refuse. The oil extraction is expensive and often damages 
the atmosphere. As an example, the search and the extraction of offshore 
oil, seriously disturb the surrounding marine environment. The extraction, 
in fact, often can be preceded from the dredging that damages the marine 
bottom and the algae, fundamental in the marine alimentary chain. The 
crude oil and the oil refined that out-comes from damaged oil tankers and 
the illicit discharges from passing ships, damage fragile ecosystems (as 
happened in Alaska, the Galapagos Islands, Italy, Spain, Lebanon and in 
many other geographic zones) and, as usually occur, a great amount of oil, 
each year, enter in the marine alimentary chain and then in our 
1
alimentary chain contaminating fishes, birds, etc. (WWF reports, 2007). 
In the next sections, will be briefly explained the main processes that 
usually occurs after an oil spill, a qualitative classification of the type of oil 
spills and some statistical data related to the oil spills. 
1
 World Wildlife Foundation 
3
Chapter tw0 The oil pollution problem of the seas 
fig. 1 - graphic representation (A) and detailed interactions (B) of conceptual 
model for the fate of petroleum in the marine environment. Various models 
depicted are often included as significant components of computer models 
attempting to simulate or predict behaviour and fate of petroleum 
compounds 
4
Chapter tw0 The oil pollution problem of the seas 
2.2 - Fate of oil at the sea 
The presence of petroleum compounds on the marine surface can 
prime many physical, chemical and biological processes in the marine 
environment (Oil at sea III, national research council of the national 
academies, 2003). 
In fig. 1, are shown two models describing the main interrelationships 
among physical, chemical, and biological processes that crude oil 
undergoes when introduced in the marine environment, subsequently 
weathers and then transported away from the source (Oil at sea III, 
national research council of the national academies, 2003). 
The main processes that affect the impact of oil releases at the sea can 
be summarized as following: 
• EVAPORATION 
evaporation is the most important process in term of mass balance. 
Within a few days following a spill, light crude oil can lose up to 75 
% of their initial volume and medium crudes up to 40 %. In 
contrast, heavy or residual oils will lose no more than 10 % of their 
volume in the first few days following a spill. Most oil spill 
behaviour models include evaporation as a process and as a factor 
in the output of the model. Despite the importance of the process, 
relatively little work ha been conducted on the basic physics and 
chemistry of oil spill evaporation. 
Fingas (1995), conducting some test in laboratory, found a simple 
experimental equation that can be used to model evaporation of 
petroleum compounds: 
5
Chapter tw0 The oil pollution problem of the seas 
Percentage evaporated=⋅ (T) ⋅ln (t) 
Where C is a constant that can be empirically-determined or 
predicted on the basis of distillation data, T is temperature, and t is 
time. Empirical equations for many oils have been determined, and 
the equation parameters found experimentally for the evaporation 
of oils can be related to commonly available distillation data for the 
oil (Fingas, 1999). 
• EMULSIFICATION 
Emulsification is the process of formation of various states of water 
in oil, often called chocolate mousse or mousse among oil spill 
workers. These emulsions significantly change the properties and 
characteristics of spilled oil. Stable emulsions contain between 60 
and 85 percent water thus expanding the volume by three to five 
times the original volume of spilled material. The density of the 
resulting emulsion can be as great as 1.03 g/ mL compared to a 
starting density ranging from about 0.95 g/ mL to as low as 0.80 g/ 
mL. Most significantly, the viscosity of the oil typically changes from 
a few hundred to a few hundred thousand milli Pascal-seconds, a 
typical increase of three orders of magnitude. This increase in 
viscosity can change a liquid petroleum product into a heavy, semi-
solid material. Emulsification, if it occurs, has a great effect on the 
behaviour of oil spills at sea. As a result of emulsification, 
evaporation slows spreading by orders of magnitude, and the oil 
rides lower in the water column, showing different drag with respect 
6
C 
Chapter tw0 The oil pollution problem of the seas 
to the wind. Oils will generally take up water once spilled at sea, but 
emulsions may not always form. Water can be simply entrained by 
the oil due to viscous forces, without forming a more stable 
emulsion. Thus, emulsification also has significant effects on the 
choice of oil spill recovery methods. 
• DISSOLUTION 
Dissolution is the chemical stabilization of oil components in water. 
Dissolution accounts for only a small portion of oil loss, but it is still 
considered an important behaviour parameter because the soluble 
components of oil, particularly the smaller aromatic compounds, 
are more toxic to aquatic species than the aliphatic components. 
Modelling interest in dissolution is directed at predicting the 
concentrations of dissolved components in the water column. Most 
models in existence do not separate the dissolution component. The 
entrainment model is sometimes used but fails to distinguish 
between dispersion and dissolution. 
• SPREADING 
Spreading is the distribution of the oil on the superficial layer of the 
water column due to the action of the natural waves or dispersants. 
There are many models trying to describe the spreading and the 
diffusion of oil. The most used models for spreading are based on 
the work by Fay (1969). Fay suggested that spreading is best 
described in three phase: inertial, viscous and surface tension. The 
inertial phase is dominated by gravity forces, the viscous phase by 
gravity and viscosity forces, and the surface tension phase by 
7
Chapter tw0 The oil pollution problem of the seas 
surface tension spreading. Many works based on Fay suggestion are 
used to compute, combining also other physical processes 
(oceanographic and meteorological), oil spills drift. 
• OXIDATION 
Crude oil is a complex mixture of organic compounds, mostly 
hydrocarbons. Oxidation alters these mixtures by creating new 
compounds and by rearranging the distribution of residual 
compounds, based on their susceptibility to the oxidative process. 
The ultimate oxidative fate of all of the organic compounds, given 
an unrestricted supply of oxygen and time, is conversion to carbon 
dioxide and water, as expressed in the following equation: 
CHO+O⇔CO+HO 
2222
where CHO is a symbol for all organic compounds. Oxidation of 
2
crude oil is mediated by two processes, photo-oxidation and 
microbial oxidation, that provide the energy to drive the oxidative 
reactions. Where crude oil is exposed to sunlight and oxygen in the 
environment, both photo-oxidation and aerobic microbial oxidation 
take place. Where oxygen and sunlight are excluded in anoxic 
environments, anaerobic microbial oxidation takes place. 
These processes, here briefly described, are really important in many fields 
of primary intervention that try to contain the oil spills at the sea but, also 
if we consider the use of satellite remote sensing sensors for oil spill 
detection and monitoring. In some cases, in fact, these processes can 
influence spectral signatures of oil spills on the sea surface. These facts 
8
Chapter tw0 The oil pollution problem of the seas 
enhance the importance of a timely and accurate detection of oil spills 
when they occur. Only in this way, and better the start of the other 
processes just mentioned (emulsion, spreading and oxidation), a detection 
“for sure” of oil spills can be performed and exploited by final users 
involved in the emergency response (as, for example, the coast guard). 
In the following chapters, will be analyzed and discussed main satellite 
remote sensing techniques for oil spill detection and monitoring as well as 
the approach proposed in this work to the same purpose. 
2.3 - Classification of the type of oil spills at sea 
In the previous section the consequences on the marine environment 
after an oil spill event have been described. 
As mentioned, when an oil spill occur it is important to describe the 
type its position and its extension. Besides, in many real cases, an 
important problem is to predict the future movement of the oil spelt, to 
better understand if and when the oil spelt will arrive to the coast. 
Another very important factor that must be considered after an oil spill 
event is related to the thicknesses of oil film on the surface. This factor, 
many times less considered, is really important in the context of the oil 
spill detection using satellite and airborne remote sensing sensors. 
Thicknesses variations indeed can influence the spectral responses of oil 
films on the sea surface. 
The U.S. Environmental Protection Agency (EPA), uses the following 
qualitative classification of oil spills, given in the order of decreasing 
thickness (Sabins, F., 1997): 
9
Chapter tw0 The oil pollution problem of the seas 
Slick: relatively thick layer (0.1 mm - 1 mm) with a definite brown or 
black colour; 
Sheen: thin silvery layer (0.0001 - 0.0003 mm) on the water surface 
with no black or brown colour; 
Rainbow: very thin (< 0.0001 mm) iridescent multicoloured bands 
visible on the water surface. 
Using satellite remote sensing, slicks can be detected but is really difficult 
to detect sheens and rainbows and so, in many cases, sheens and rainbows 
classes are merged in a unique class. 
How these thicknesses ranges can influence the oil spill detection will 
be discussed more in details in the sections of the next chapter, where it 
will be reported the state of art and the main satellite sensors and 
techniques used for oil spill detection and monitoring. 
2.4 - Oil spills statistics 
2
Since 1974, ITOPF has maintained a database of oil spills from 
tankers, combined carriers and barges (Oil spill statistics, ITOPF, 2006). 
All the statistics covers all accidental spillages except those resulting 
from acts of war. For historical reasons, spills are generally categorised by 
size (<7 tonnes, 7-700 tonnes and >700 tonnes) although the actual 
amount spilt is also recorded. Information is now held on nearly 10,000 
incidents, the vast majority of which (84%) fall into the smallest category 
i.e. <7 tonnes. 
2
 International Tanker Owners Pollution Federation 
10
Chapter tw0 The oil pollution problem of the seas 
as the shipping press and other specialist publications, and also from 
vessel owners and their insurers. 
Not surprisingly, information from published sources generally relates 
to large spills, often resulting from collisions, groundings, structural 
damage, fires and explosions, whereas the majority of individual reports 
relate to small operational spillages. Complete reporting of this latter type 
of spill is clearly difficult to achieve. It should be noted that the figures for 
amount of oil spelt in an incident include all oil lost to the environment, 
including that which is burnt or remains in a sunken vessel. 
There is considerable annual variation in both the incidence of oil spills 
and the amounts of oil lost and so the following tables, and any averages 
derived from them should be viewed with caution. 
The incidence of large spills is relatively low and detailed statistical 
analysis is rarely possible, consequently emphasis is placed on identifying 
trends. Thus, it is apparent from the table 1 below, that reports the 
numbers of oil spills for year, the number of large spills (>700 tonnes) has 
decreased significantly during the last thirty years. The average number of 
large spills per year during the 1990s was less than a third of that 
witnessed during the 1970s. 
The vast majority of spills are small (i.e. less than 7 tonnes) and data on 
numbers and amounts is incomplete. However in most years it is probable 
that they make a relatively small contribution to the total quantity of oil 
spilled into the marine environment as a result of tanker accidents. 
11
Chapter tw0 The oil pollution problem of the seas 
year 7-700 tonnes> 700 tonnes
 1970 6 29 
1971 18 14 
1972 48 27 
1973 27 32 
1974 89 28 
1975 95 22 
1976 67 26 
1977 68 17 
1978 58 23 
1979 60 34 
1980 52 13 
1981 54 7 
1982 45 4 
1983 52 13 
1984 25 8 
1985 31 8 
1986 27 7 
1987 27 10 
1988 11 10 
1989 32 13 
1990 51 14 
1991 29 7 
1992 31 10 
1993 31 11 
1994 26 9 
1995 20 3 
1996 20 3 
1997 28 10 
1998 25 5 
1999 19 6 
2000 19 4 
2001 16 3 
2002 12 3 
2003 15 4 
2004 16 5 
2005 21 3 
2006 14 4 
table. 1 – number of oil spills over 7 tonnes 
12
Chapter tw0 The oil pollution problem of the seas 
In the table 2, instead, is reported the annual quantity of oil spilt 
during the years 1970-2006. It is notable that a few very large spills are 
responsible for a high percentage of the oil spilt. For example, in the ten-
year period 1990-1999 there were 358 spills over 7 tonnes, totalling 1,138 
thousand tonnes, but 830 thousand tonnes (73%) were spilt in just 10 
incidents (just under 3%). 
The table 3, instead, gives a brief summary of major oil spills since 
1967. A number of these incidents, despite their large size, caused little or 
no environmental damage as the oil did not impact coastlines but there are 
also listed a number of accidents that have created serious environmental 
damage. In fact, looking at the table, the most serious oil spill of last years 
is related to Jiyeh power plant accident in Lebanon. After this accident, 
most of Lebanon coast was completely submerged by the oil (around 150 
km of coast) and, besides, all the sea floor was almost covered by a toxic 
carpet of heavy oil up to 10 cm thick. 
Considering all these data, is clear that the politics of the seas control 
must be changed. Therefore, is obvious that the traditional instruments of 
control and also of the monitoring of the seas are clearly inadequate to 
respond to the oil spill accidents. New technologies, thus, must be used to 
effectively give a support to all the authority devoted to the respond of 
these kind of emergencies. Among these new technologies, surely satellite 
remote sensing is assuming a key role in this field. In the following 
chapter, the capability of remote sensing sensors for oil spill detection and 
monitoring will be considered starting from an excursus of techniques 
used in the past in this field, up to last works. 
13
Chapter tw0 The oil pollution problem of the seas 
year quantity (tonnes)
1970 330,000 
1971 138,000 
1972 297,000 
1973 164,000 
1974 175,000 
1975 357,000 
1976 364,000 
1977 291,000 
1978 386,000 
1979 640,000 
1970s total3,142,000 
1980 206,000 
1981 48,000 
1982 12,000 
1983 384,000 
1984 28,000 
1985 85,000 
1986 19,000 
1987 30,000 
1988 190,000 
1989 174,000 
1980s total1,176,000 
1990 61,000 
1991 430,000 
1992 172,000 
1993 139,000 
1994 130,000 
1995 12,000 
1996 80,000 
1997 72,000 
1998 13,000 
1999 29,000 
1990s total1,138,000 
2000 14,000 
2001 8,000 
2002 67,000 
2003 42,000 
2004 15,000 
2005 17,000 
2006 13,000 
table.2 – annual quantity of oil spilt 
14
Chapter tw0 The oil pollution problem of the seas 
Spill/tanker Location Date Tonnes of crude oil 
Gulf War oil spill Persian Gulf January 780,000 - 1,500,000 
23,1991 
Ixtoc I oil well Gulf of Mexico June 3,1979 – 454,000 - 480,000 
March 
23,1980 
Atlantic Trinidad and July 19, 287,000 
Empress Tobago 1979 
/ Aegean 
Captain 
Fergana Uzbekistan March 2, 285,000 
Valley 1992 
Nowruz Persian Gulf February, 260,000 
oil field 1983 
ABT 700 nautical 1991 260,000 
Summer miles 
(1,300 km) off 
Angola 
Castello de Bellver Saldanha Bay, August 6, 252,000 
South Africa 1983 
Amoco Brittany, March 16, 223,000 
Cadiz France 1978 
Haven Mediterranean 1991 144,000 
Tanker Sea near 
Genoa, Italy 
Odyssey 700 nautical 1988 132,000 
miles 
(1,300 km) off 
Nova Scotia, 
Canada 
Sea Star Gulf of Oman December 115,000 
19, 1972 
Torrey Scilly Isles, March 18, 80,000 - 119,000 
Canyon UK 1967 
Irenes Navarino Bay, 1980 100,000 
Serenade Greece 
Urquiola A Coruña, May 12, 100,000 
Spain 1976 
Guimaras oil spill Philippines August 11, 172 – 1540 
2006 
Jiyeh power Lebanon July 13, 20,000 - 30,000 
station oil spill July 15, 
2006 
Citgo Lake Charles, June 19, 2006 ~6,500 
refinery LA 
15