Environmental Bases on the Exploitation of Crude Oil in Mexico

Oil is one of the most important energy resources for the global economy. Regarding this, Mexico has an economic dependency of the oil industry that has being going on for decades. Based on the current oil production, the proven and possible reserves might last for ten years; still, if we consider probable and possible oil reserves, Mexico could count with an oil production for more than 30 years. Under this consideration, Mexico requires state of the art technologies for exploring, exploiting and processing crude oil.


Introduction
Oil is one of the most important energy resources for the global economy.Regarding this, Mexico has an economic dependency of the oil industry that has being going on for decades.Based on the current oil production, the proven and possible reserves might last for ten years; still, if we consider probable and possible oil reserves, Mexico could count with an oil production for more than 30 years.Under this consideration, Mexico requires state of the art technologies for exploring, exploiting and processing crude oil.
Nowadays the technological and industrial development has to be environmentally responsible in accordance with the global needs.That is why the creation of new technologies and resources exploitation must be based on a responsible energetic development.Regarding this matter, being environmental friendly is a main goal for the society (Rodríguez et al., 2009), and gets to our attention that Mexico -until the seventiesdid not apply any environmental criteria while exercising its oil activities (Ortínez et al., 2003).In consequence, oil production, leading, transportation, storage and processing had a negative impact on soils (Trujillo et al., 1995;Rivera-Cruz & Trujillo-Narcía, 2004), waters (Adams et al., 1999), and ecosystems at the southeast of the country (Santos et al., 2011).
In Mexico there are environmental regulations about hydrocarbons pollution, although these bypass criteria about the hydrocarbons' chronic effects on the ecosystems.However, in accordance with the current development conditions, it is necessary to introduce the environmental basis for the oil exploitation, whose main goal is to analyze the effects of the traditional oil related activities.The aim is to lay down the foundations for the creation of new technologies that contribute to a responsible and affordable energetic development for the country.
The water bodies and the coastal zone are also affected by wastes derived from oil exploring, offshore production, sea and submarine transportation, shipment and storage operations, accidents during operations such as submarine oil pipes cracks, tankers accidents, spill outs and explosions at oil rigs (García-Cuéllar et al., 2004;Mei & Yin, 2009).
During the seventies, Mexico developed oil exploitation technology and intensified its crude oil production and transportation via underwater pipelines to cargo floating buoys to storage ports located at Tabasco, as well as the oil's transformation and refining at Coatzacoalcos, Veracruz, and Salina Cruz.As a consequence, this created industrial networks all over the country that raised pollution issues at coastal zones, thus impacting the ecosystems of the Gulf of Mexico and the Pacific southeast coast (Carbajal & Chavira, 1985;Botello, 1996;González-Lozano et al., 2006;Salazar-Coria et al., 2007).Nevertheless, conscience was not made until the IXTOC-I accident regarding the potential risks of the industry's activities (Jernelöv, 2010).Currently the main oil and gas production zone is located at the Gulf of Mexico, in the Campeche maritime zone where there are severely affected ecosystems after more than three decades of oil exploitation (García-Cuéllar et al., 2004).The last Gulf of Mexico disaster was estimated three times that of the Valdez spill (Trevors & Saier, 2010).
On the other hand, in Mexico was installed the first and largest oil refinery (until 2004) in Latin America, dating from 1908; the environmental deterioration is evident after more than one hundred years of oil exploitation.The effects are observed at the lower Coatzacoalcos River (Toledo, 1995;González-Mille et al., 2010) as it has suffered the impacts of the oil refining and transportation processes since the swamp areas surrounding the oil refinery are used as waste traps.In addition, accidents related to carelessness during the load and cleaning of the tankers, as well as the discharge of the cooling water from the Minatitlán refinery into the river have created a complex mixture of hazardous materials that pollute the lower Coatzacoalcos River area directly, affecting both the fishing resources and the inhabitants (Toledo, 1983;Rosales-Hoz. & Carranza-Edwards, 1998;Cruz-Orea et al, 2004;Ruelas-Inzunza et al, 2009;Ruelas-Inzunza et al., 2011).
Concurrently, we must add the petrochemical activity to the oil exploring and refining processes (Rao et al., 2007a).With the creation of petrochemical complexes since 1960, these activities increased the impact of the area conditioning where the industrial zones were located (Ortiz et al., 2005).Additionally, huge amounts of materials were dredged in order to build the artificial dock of Pajaritos.The industrial plants operation, the numerous www.intechopen.comEnvironmental Bases on the Exploitation of Crude Oil in Mexico 91 transportation networks (petrochemical ducts and pipelines) and the linking earth systems built at the lower areas caused other activities with an environmental impact for the zone (Toledo, 1995;Adams et al., 2008).Another environmental effect of the intensity of the oil exploitation has been the loss of swamps, mangroves, and other elements of the water coastal systems that must be attended given its importance for the environmental services (Gutiérrez & Zavala, 2002;Bahena-Manjarrez et al., 2002).

Crude oil toxicity
Toxicity is the ability of a chemical substance to damage and alter certain functions of the biological systems (Rivero et al., 2001).There are two toxicity criteria for the natural systems.Acute toxicity is produced by large, short-termed, accidental polluting agents' discharges (Roth & Baltz, 2009), although it may have long term effects.On the other hand, chronic toxicity is expressed by effects noticed on the long term due to relatively small amounts of a toxic compound found on air, water or soil (Scarlett et al., 2007).
Crude oil is constituted by a complex hydrocarbon mixture and a wide range of n-alkanes (C 6 -C 60 ), alkenes, aromatic hydrocarbons, as well as polar fractions formed by asphaltene and resins (Salanitro et al., 2000).From these, hydrocarbons with of the highest molecular weight are the most persistent within the environment (Rivera-Cruz & Trujillo-Narcía, 2004;Kostecki et al., 2005).The oil toxicity within the ecosystems depends on the physical and chemical characteristics of former's components (Vega et al., 2009), discharges time and types (Romaniuk et al., 2007), weathered degree (Rivera-Cruz et al., 2005), biological (Rivera-Cruz et al., 2002) and environmental (King et al., 2006) factors.In this sense, oil can affect the natural systems differentially.
In Mexico, the main oil pollution sources are the oil-well pits and the deficiencies in their maintenance, the discharges of the processing facilities, petrochemical plants and oil ducts cracks since most of the facilities are sixty years ago (Botello, 1990).There is a systemic and synergic interaction of the effects of the hydrocarbon polluted soils; in this sense, all of the ecosystems' components are altered, which affects the soils' properties, the present microorganisms, and even the plants' growth and reproduction, endangering the ecosystems' sustainability (Palma-López et al., 2007).

Ground ecosystem: soil, microorganisms and plants
The oil affectations are due mainly to oil spills; the negative effects of crude oil depend on the spill type (Kolesnikov et al., 2010), the zone's ecological characteristics, the amount and type of spilled oil, as well as the time over the soil (Hernández-Acosta et al., 2004) and weathered degree (Rivera-Cruz et al., 2005).In this sense, the pollution levels vary in accordance with the hydrocarbons' source, the age of the oil facilities and their deterioration (Adams et al., 1999).Hydrocarbon polluted soils also experience physical, chemical and biological processes (Li et al., 1997;Martínez & López, 2001;Rivera-Cruz et al., 2002;Rivera-Cruz, 2004), altering the sustainability and productivity of the systems (FAO et al., 1980).
Nevertheless, there are properties inherent to soils that favor the fixation and toxicity of the pollutants (Charman & Murphy, 2007).For instance, soils with a clay texture take a long time to recover from an oil spill, while the thick texture soils recover in short time (Hernández-Acosta et al., 2006).Still, this last texture can favor mobility towards the phreatic surfaces by the infiltration of the pollutant (Iturbe et al., 2007), thus widening the range of the hydrocarbon's toxicity (Srogi et al., 2007) towards the water tables (Fig. 1).Therefore, the aquatic organisms and the trophic chain can be severely affected, in consequence, the inhabitants consuming these products.Fig. 1.Vertical infiltration process of crude oil (Eweis et al., 1998).
There are synergic effects due to the crude oil soil pollution, since the oil blocks the gas interchange with the atmosphere -given its anoxic properties- (Leitgi et al., 2008) and the change of the physical and chemical properties of the soils (Martínez & López, 2001) severely diminish the microbial communities benefic to the soil (Labud et al., 2007).These microbiological variables are indeed a good indicator of the impact of a pollutant on the soil (Eibes et al., 2006).
The toxicity mechanisms caused by the oil on soils is not limited to the microorganisms, since it also includes plants that suffer from hydric stress (Chaîneau et al., 1997) due to the lack of water and nutrients.Concurrently, the lipid structures within the cells of the plants may be affected if the former are not quickly metabolized.In this sense, the oil has diverse effects over the plants since it inhibits the germination, growth and the biomass accumulation, reflecting these effects on a smaller plants production and, with time, in detriment of the natural resources sustainability.
The variables that have a determining effect over the plants affected by the soil hydrocarbons pollution are the soil ecology, the rhizosphere, emergence and germination, aerial and radical growth, biomass accumulation and salts present on the soil (Fig. 2).a. Soil ecology: Oil also has an effect over the soil's biological composition (Tang et al., 2011), since toxic concentrations of oil on the soil inhibit the development of different species of nematodes, protozoa, rotifers, algae, fungi, bacteria and actinomycetes (Chaîneau et al., 2003;Ilarionov et al., 2003).Likewise, it induces the loss of biodiversity of microbial communities, which are of significant relevance in the biogeochemical cycles of the ecosystem affecting, as a consequence, its productivity (Rhodes & Hendricks, 1990) and the nutrients availability.b.Rhizosphere: It is the soil area surrounding the plant's root containing, 10 to 100 times more exudates than a soil lacking plants (Rao et al., 2007b).The root exudates (sugars, alcohols, and enzymes) provide enough carbon and energy for the rhizospheric microorganisms (Olguín et al., 2007;Muñoz et al., 2010) and it is precisely on this region where the intense and complex interactions between the roots systems, the microorganisms and the environment occur, with an increase of the total microbial activity (De la Garza et al., 2008).Oil blocks the gases interchange between the soil and the atmosphere, causing death or diminishment of the bacteria and nematodes (Tynybaeva et al., 2008).Nevertheless, Freedman (1989) and Germida et al. (2002) report some microorganisms can increase its population in the presence of hydrocarbons thanks to their capabilities for surviving under such conditions.c.Emergence and germination: Oil forms a hydrophobic layer diminishing the hygroscopic water retention (Quiñones et al., 2003).This reduces the plants' water retention capability, directly affecting the seeds emergence and germination (Vázquez-Luna et al., 2010a).Other effect is reflected due to the volatile oil fractions that penetrate and damage the seeds embryo (Banks & Schultz, 2005), diminishing its viability (Chaîneau et al., 1997) and affecting the ecosystem balance (Labud et al., 2007).d.Aerial and radical growth.Recent researches find out that high hydrocarbons concentrations damage the plants growth and development since the pollutants diminish the radicle elongation and the vegetative growth (Vázquez-Luna et al., 2010a).García (2005) found a growth and dry weight reduction in rice seedlings after a 25 day exposure to 90,000 mg•kg -1 of weathered oil.This effect could be attributed to the oil since it forms a hydrophobic layer, limiting the root's water and nutriments absorption.
e. Biomass accumulation.When the plant grows and its needs increase, the lack of absorbed water diminishes the cellular swelling, reduces or inhibits the nutriments incorporation processes and affects the vegetative growth (Inckot et al., 2011), and the later grains or fruits harvest.On this regard, researches by Rivera-Cruz & Trujillo Narcía (2004) found that the exposure to oil hydrocarbons concentrations of 2791, 9025 and 79,457 mg•kg -1 on the soil inhibited the vegetative growth and reduced the plants biomass in the seedlings of Echinochloa polystachya, Brachiaria mutica and Cyperus spp grasses.The biomass reduction is due to the damage caused in the root system (Langer et al., 2010), making more difficult the plants' growth and, consequently, reducing their biomass (Zavala-Cruz et al., 2005) (Fig. 3).Additionally, there are visual reports of chlorosis and reddish hues characteristic of phenolic compounds on the leaves, due to the roots' stress and damages (Harvey et al., 2001;Peña-Castro et al., 2006) as shown on Figure 4. f.Salts presence.Regarding salts presence, Adams et al. (2008) state that, when an oil spill occurs, high salinity is commonly associated to the production water or to the formation of the oil well.Soluble salts of calcium carbonates, nitrates and sulfates increase in presence of hydrocarbons (Ke et al., 2011), as shown on Figure 5.

Marine ecosystems
The oil toxicity in the marine environment is very complex due to the great diversity of factors intervening during an environmental risk event.When oil is spilled or introduced to the marine ecosystem (Mercer & Trevors, 2011), it becomes weathered (Fig. 6), during which a) b) several processes take place, such as the evaporation of the volatile compounds, dispersion by means of waves, winds and turbulences (Chang et al., 2011), emulsification, which constitutes the main cause of the persistence of light and medium crude oils on the sea surface, dilution depending of the crude oil type, temperature, turbulence and dispersion, sedimentation or sinking of the particles by adhesion to the sediments or organic matter, and biodegradation (Botello, 1995;Nikolopoulou & Kalogerakis, 2010;Prince, 2010).In Mexico, the Tonalá River in Veracruz and the Laguna de Términos in Campeche have shown the highest levels of dissolved hydrocarbons in the Gulf of Mexico (Botello et al., 1996).
Fig. 6.Weathering process of the oil spilled in the sea, taken from Botello (1995).
Regarding the hydrocarbons assessment in the lower Coatzacoalcos River basin, the classical works of Botello & Páez (1986) are outstanding since they found the highest polycyclic aromatic hydrocarbons (PAH) levels at the zones of fixed discharges or of intense oil activity (Garcıá-Ruelas et al., 2004).Other studies determined the presence of PAH on 19 organic species such as fish, crustaceans and mollusks (sea bass, native sea bream, scallop and prawns) and the presence of benzo(a)pyrene and benzo(ghi)perylene, which are the most hazardous given its carcinogenic potential (Sharma et al., 2002).On the other hand, oil refinement and processing also contribute to broadening the range of toxicity caused to the fishing industry.
The marine oil pollution effects are harder to estimate (Trevors & Saier, 2010), since there is no information previous to the beginning of the oil-industry activities over the effects on the ecosystems and its components; as a consequence, it is not possible to measure the magnitude of the oil industry in the marine seaway.Additionally, it has not been possible to determine the chronic effects of pollution over the ecosystems since the data available is very precise in a given time and determined concentrations (García-Cuéllar et al., 2004).Currently, there are studies proving the existence of considerable disturbances in the environment (Scarlett et al., 2007;Denoyelle et al., 2012); however, it is important to highlight www.intechopen.com Environmental Bases on the Exploitation of Crude Oil in Mexico 97 that pollutants bioaccumulate in water organisms destined to human consumption (Webb, 2011).

Human beings
Mexico's oil industry history has been characterized by conflicts, power clashes, interests differences, competence between diverse companies, oilers and political leaders discrepancies, jealous preservation of the acquired rights by foreign interests, international consumer interest to have access a strategic product to a low cost, struggle for applying the 1917 Constitution over a given industry and the pressure from the workers to obtain a higher participation of the profit sharing (Brown, 2005).
The social conflicts attributed to the oil-zones development has been studied by different researchers; among them, Bustamante & Jarrín (2005) point that the presence of oil-related activities does not improve the population life standard nor destroys it, although it must be said that such study did not consider the analysis of violence indicators nor the environment toxicity.On this regard, Avellaneda (2004) expresses that there cannot be an "environmental conflict" study which excludes the social dimension and vice versa, since the critics toward the oil-industry activities shall be discussed from several social, political, economic and cultural angles (Avellaneda, 2005).About this, a recent study by Vázquez et al. (2010b) found negative effects over the equitable development in areas near oil zones and considers the population health as a primordial entity for development.Regarding this, Elliot (1994) says that when the degree of residues generation exceeds the atmosphere, oceans, vegetation and soils natural capacity, these are absorbed affecting human health and the ecological systems.
A study made at the Ecuador's Amazonia found that women living near oil wells zones (up to 5 km) presented symptoms such as tiredness, nasal and throat irritation, headache, eye irritation, earache, diarrhea and gastritis; these were associated with the proximity to oil wells and stations (San Sebastián et al., 2001).The main effects found in other studies regarding the acute exposure to oil after an oil spill at sea have been headache, throat and eyes irritation, tiredness, in addition to disorders such as anxiety and depression (Lyons et al., 1999).However, a repeated or long (chronic) exposure to low concentrations of oil volatile compounds can produce nausea, drowsiness, and headache (Kaplan et al., 1993).In accordance with Sánchez (2003), certain cases of pediatric intoxications are due to short chain hydrocarbons acting as asphyxiating agents given their high volatility and low viscosity, replacing the alveolar gas and producing hypoxia.When going through the alveolar membrane, they create symptoms such as the diminishment of the conscience threshold progressing towards convulsions, epileptic status or coma; additionally they induce the apparition of arrhythmias.On their side, the long chain hydrocarbons have a lower toxic power and large amounts are needed for them to produce central depression.
The symptoms related range from symmetric sensorial dysfunction in the distal zones of the extremities, weakness of fingers and toes, loss of deep sensitive reflexes, to central nervous system depression, drowsiness and motor incoordination.
The hydrocarbons pollution might have teratogenic, mutagenic and carcinogen effects on human health (Neff, 2004).The oil hydrocarbons toxicology has been reviewed by the Agency for Toxic Substances and Diseases Registry (ATSDR) in the USA.According to this www.intechopen.com Crude Oil Exploration in the World 98 environmental agency, a major part of the total repercussion over the human health of all the chemical products on the soil is due to specific compounds called worrying chemical substances with a significant toxicological power.The worrying chemical products for gasoline, kerosene, and overall fuel polluted areas are benzene, toluene, ethilbenzene and xylene (BTEX) depending on the spill and the oilfield nature, which may contain heavy metals such as nickel and vanadium (López et al., 2008).Additional to the polycyclic (or polynuclear) aromatic hydrocarbons such as benzo(a)pyrene (EA, 2003), most of these hydrocarbons of high-molecular weight are present in soils with weathered oil or previous spills (Rivera-Cruz, 2004;Rivera-Cruz & Trujillo-Narcía, 2004).About this, the International Agency for Research on Cancer (IARC), dependent of the World Health Organization (WHO), assessed benzo(a)anthracene, benzo(a)pyrene, and dibenz(a,h)anthracene as probable human carcinogens, and benzo(b)fluoranthene, benzo(k)fluoranthene, indene, pyrene, and naphthalene as possible human carcinogens (Kirkeleit et al., 2008).
Some compounds act as xenoestrogens, having the ability of stimulating the mammary gland tissue (De Celis et al., 2006); others may work as endocrine disruptors having effects on the reproduction (Chichizola, 2003).On this regard, cancer is the third cause of death on people aged 1 to 19 years; while only 5 to 10% of the malign tumors have been actually related to genetic causes; the rest might be influenced by a wide range of environmental factors (Anderson, 2001).
Because of this, it is important to regulate the oil refinement processes since they can pour into the atmosphere a large number of chemical compounds such as naphthalene, considered a dangerous airborne compound in accordance with the US Environmental Protection Agency (USEPA) since it can cause eye, skin and respiratory tract irritation.If inhaled for long periods it can damage the kidneys and the liver, in addition to skin allergies and dermatitis (Baars, 2002), cataracts, retina damage and also can attack the central nervous system.In high concentrations it can destroy red blood cells, causing hemolytic anemia (USEPA, 2003); as well, it is considered as a possible human carcinogen (Carmichael et al., 1991;ATSDR, 2004).
The main health risks are due to contact, inhalation and ingestion, and may increase depending on age, gender and exposure degree (Chen & Liao, 2006).Some surveys show that among the 13 fractions of TPH, the aliphactics EC8-16 and aromatics EC10-21 are the main contributors to human health risks along all of the exposure routes (Park & Park, 2010).

The challenge: responsible energy development
The Responsible Energy Development in Mexico is an immediate need in view of the holistic analysis of the effects of the oil industry over the natural resources (Patín, 2004).For a proposal to work, it is required the joint efforts of the scientific, technological, industrial, political, regulatory, legal and social sectors.In this sense, the environmental problems must be attacked from different angles, involving all of its elements (Fig. 7).
Mexico needs a holistic political view of the oil hydrocarbons pollution including the social, ecological and economical aspects, and -most of all-to create the conditions required for the Responsible Energy Development with an integral regulatory, economical and legislative frame.Fig. 7. Holistic approach in order to achieve a Responsible Energy Development.
On one hand, the oil spills and accidents that may occur due to maintenance deficiencies can be prevented with the proper maintenance and technological design on the side of the industry.On the other hand, citizens must avoid the clandestine oil valves and inform the authorities about fails; this information has been added into the environmental Mexican regulations.Nevertheless, there is still the need to increase the ecosystems protection due to the chronic effects of the polluting agents via strict legislation and regulations regarding the industrial wastes poured into the atmosphere, water bodies and soils, incorporating the periodic evaluation to the fishing resources for human consumption.
The economy is a subsystem within the whole development system and it is necessary that part of the oil surplus is used to finance research as well as for the technological development of adequate oil exploring, extraction, production, storage, transportation and processing technologies that are environmentally responsible and less disturbing for the ecosystems.
Finally, it is urgent to invest in the creation, research and development of new alternative energy sources for them to be gradually introduced within the country's energetic development.Such investments would enable the exploitation of profitable and sustainable energy sources, as well as the technological development in the fields of bioenergetics, biofuels, wind, tidal and solar energies and an efficient use of the existing natural resources without jeopardizing others resources' sustainability.

Conclusion
The environmental bases for the oil exploitation are the mainstays in order to analyze the effects of the traditional exploitation of oil in Mexico.The technological and scientific advances must be built over these bases, towards the development of new and better www.intechopen.com Crude Oil Exploration in the World 100 technologies for the resources exploitation.Consequently, this must cover the knowledge of the effects of pollution and thus promote the energetic sustainability without compromising human health, the environmental balance and the national economy.
Oil is fundamental for the economy of many countries.Therefore, it is not convenient to propose a radical change in the energetic system; rather, the proposal should consider the scientific and technological development based on two actions.The first one must focus on the exploring, extraction, processing, storage and transportation of crude oil with less risk and minimal disturbances of the natural resources.The second must bear in mind the gradual and integrated incorporation of the sustainable energies, allowing the efficient exploitation of resources without endangering others.

Fig. 2 .
Fig. 2. Variables that have a determining effect over the plants affected by hydrocarbon polluted soils are: a) soil ecology, b) rhizosphere, c) emergence and germination, d) aerial and radical growth, e) biomass accumulation and f) salts presence.

Fig. 5 .
Fig. 5. Salts presence in polluted soils (with 12,276 mg•kg -1 of HTP) as a collateral effect of the oil industry pollution.