Petroleum: Hydrocarbon Contamination

Authored by: Svetlana Drozdova , Erwin Rosenberg

Managing Air Quality and Energy Systems

Print publication date:  July  2020
Online publication date:  July  2020

Print ISBN: 9781138342675
eBook ISBN: 9781003043461
Adobe ISBN:

10.1201/9781003043461-4

 

Abstract

Contamination of water, soil, and sediment samples by petroleum hydrocarbons is a common and severe environmental problem, caused by improper handling, storage, transport, or use of petrochemical products or raw materials. Petroleum hydrocarbons represent a mixture of compounds, and some of them (e.g., benzene, polycyclic aromatic hydrocarbons) may exhibit toxic and/or carcinogenic properties. Because petroleum products are a complex and highly variable mixture of hundreds of individual hydrocarbon compounds, characterizing the risks posed by petroleum-contaminated soil and water has proven to be difficult and inexact. It is very important to have an understanding of the toxicology, analytical science, environmental fate and behavior, risk, and technological implications of petroleum hydrocarbons in order to interpret, evaluate the risk of, and make decisions about potential hazardous effects to and ensure the appropriate protection of the environment.

 Add to shortlist  Cite

Petroleum: Hydrocarbon Contamination

Introduction

Historically, environmental analyses focused on monitoring compounds that pose a threat to humans and their environment. Petroleum hydrocarbon compounds are among them. Contamination of water, soil, and sediment samples by petroleum hydrocarbons is a common and severe environmental problem caused by improper handling, storage, transport, or use of petrochemical products or raw materials.

Petroleum products are the major source of energy for industry and daily life. Leaks and accidental spills occur regularly during exploration, production, refining, transport, and storage. In addition, natural processes can result in seepage of crude oil from geologic formations below the seafloor. The total input of crude oil and petroleum into the environment is estimated to be 1.3 million tons per year. To understand the potential effect of petroleum contaminations on the environment, it is important to understand the nature and distribution of sources and their inputs. Petroleum poses a range of environmental risks when released into the environment. Catastrophic and large-scale spills have a very severe physical impact in addition to the chemical pollution that they cause; chronic discharges and small releases can damage and eventually kill the exposed flora and fauna due to toxicity of many of the individual compounds contained in petroleum. Oil contamination in the environment is primarily assessed by measuring the chemical concentrations of petroleum products in the affected environmental compartment (e.g., sediment, biota, water).

This entry provides a discussion of the environmental relevance of petroleum hydrocarbons; the principal sources of petroleum contaminations in the environment; and the nature and composition of crude oil and petroleum products derived from it. The fate of petroleum hydrocarbons in the environment, possible effects from exposure to them, and their toxicity are discussed as well. The entry is concluded by an overview of analytical methods for determination of petroleum hydrocarbon contamination.

Petroleum Hydrocarbons and Their Environmental Relevance

Oil and gas resources are organic compounds, formed by the effects of heat and pressure on sediments trapped beneath the earth’s surface over millions of years. The remains of animals and plants that lived millions of years ago in a marine environment were covered by layers of sand and silt over the years. Heat and pressure from these layers helped the remains turn into crude oil or petroleum.[ 1 ] The word “petroleum” means “rock oil” (from Greek: petra [rock] + Latin: oleum [oil])[ 2 ] or “oil from the earth.” While ancient societies made some use of these resources, the modern petroleum age began less than a century and a half ago, when in 1859, Colonel Drake discovered oil in Oil Creek in Titusville, Philadelphia, United States. From that time on, the world’s demand for fossil fuel and the production of oil have continuously increased. From the 1980s, in particular, after the second oil crisis of 1979, the petroleum business has developed into a high-technology industry. Advances in technology have greatly improved the ability to find and extract oil and gas and to convert them to efficient fuels and useful consumer products. About 100 countries produce crude oil. Russia, Saudi Arabia, the United States, Iran, and China are the top five producing countries in 2009 (Table 1).[ 3 ] In the United States, the oil and gas industry employs 1.4 million people and generates about 4% of U.S. economic activity. It is larger than the domestic automobile industry and larger than education and social services, the computer industry, and the steel industry combined.[ 4 ] At a refinery, different fractions of the crude oil are separated into useable petroleum products. Various sources of information provide a good overview of the different processes in petroleum refining.[5–7] Petroleum products are used worldwide for energy production, as fuel for transport, and as a raw material for many chemical processes. The United States is the biggest consumer of oil in the world (Table 1). Although there exist well-developed alternatives to the use of oil (particularly for energy production and transportation), our societies are still strongly dependent on oil, which is an environmental burden, an economic problem, and a political hazard. However, at the current time, the economic situation still favors the use of petroleum and petroleum products for these applications rather than its alternatives, which at the moment are not competitive from an economic point of view.

Table 1   Annual Production and Consumption of Oil by the Top 10 Industrial Nations and by the Top 10 Countries in the European Union

Oil production by country

Oil consumption by country in the world

Rank

Country

Amount bbl/day

Date

Percentage %

Rank

Countries

Amount bbl/d

Date

Percentage %

1

Russia

10,120,000

2010

11.9

1

United States

18,690,000

2009

22.6

2

Saudi Arabia

9,764,000

2009

11.5

2

China

8,200,000

2009

9.9

3

United States

9,056,000

2009

10.7

3

Japan

4,363,000

2009

5.3

4

Iran

4,172,000

2009

4.9

4

India

2,980,000

2009

3.6

5

China

3,991,000

2009

4.7

5

Russia

2,740,000

2010

3.3

6

Canada

3,289,000

2009

3.9

6

Brazil

2,460,000

2009

3.0

7

Mexico

3,001,000

2009

3.5

7

Germany

2,437,000

2009

2.9

8

United Arab Emirates

2,798,000

2009

3.3

8

Saudi Arabia

2,430,000

2009

2.9

9

Brazil

2,572,000

2009

3.0

9

Korea, South

2,185,000

2010

2.6

10

Kuwait

2,494,000

2009

2.9

10

Canada

2,151,000

2009

2.6

Total

84,764,555

Total

82,769,370

Oil production by EU member states

Oil consumption by EU member states

Rank

Countries

Amount bbl/d

Date

Percentage %

Rank

Countries

Amount bbl/d

Date

Percentage %

1

United Kingdom

1,502,000

2009

60.4

1

Germany

2,437,000

2009

16.2

2

Denmark

262,100

2009

10.5

2

France

1,875,000

2009

12.5

3

Germany

156,800

2009

6.3

3

United Kingdom

1,669,000

2009

11.1

4

Italy

146,500

2009

5.9

4

Italy

1,537,000

2009

10.2

5

Romania

117,000

2009

4.7

5

Spain

1,482,000

2009

9.9

6

France

70,820

2009

2.8

6

Hungary

1,373,000

2009

9.1

7

Netherlands

57,190

2009

2.3

7

Netherlands

922,800

2009

6.1

8

Poland

34,140

2009

1.4

8

Belgium

608,200

2009

4.1

9

Spain

27,230

2009

1.1

9

Poland

545,400

2009

3.6

10

Austria

21,880

2009

0.9

10

Greece

414,400

2009

2.8

Total (EU, 27 countries):

2,485,550

2009

Total (EU, 27 countries):

15,012,050

Norway

2,350,000

2009

Norway

204,100

Turkey

52,980

2009

Turkey

579,500

Source: Adapted from Energy Statistics: Oil-Production (Most Recent) by Country.[ 3 ] bbl, barrel; EU, European Union. 1 bbl ≈ ca. 159 L.

Petroleum poses a range of environmental risks when it is released into the environment (whether by catastrophic spills or through chronic discharges). In addition to the physical impact of large spills, the toxicity of many of the individual compounds contained in crude oils or petroleum products is significant. Information on how petroleum hydrocarbons enter and diffuse in the environment is abundant.[ 8 , 9 ] The sources of petroleum input to the environment, particularly to the sea, are diverse. They can be categorized effectively into four major groups, namely, natural seeps, petroleum extraction, petroleum transportation, and petroleum consumption.

Natural seeps are frequently encountered phenomena that occur when crude oil seeps from the geologic strata beneath the seafloor to the overlying water column as a natural process.[ 10 ] Recognized by geologists for decades as indicating the existence of potentially exploitable reserves of petroleum, these seeps release vast amounts of crude oil annually. Yet these large volumes are released at a rate low enough that the surrounding ecosystem can adapt and even thrive in their presence; which is not true in case of the catastrophic and accidental impact of a tanker or oil well spill. Natural processes are, therefore, responsible for over 45% of the petroleum entering the marine environment worldwide (Table 2).[ 11 ]

Table 2   Petroleum Input to the Sea

 

North America

Worldwide

Source of Input

Tons

%

Tons

%

Natural seeps

160,000

61

600,000

46

Petroleum extraction

3,000

1

38,000

3

Petroleum transportation

9,100

4

150,000

12

Petroleum consumption

84,000

32

480,000

37

Other

3,900

2

32,000

2

Total input:

260,000 tons

 

1,300,000 tons

 

Source: Adapted from Oil in the Sea III Inputs, Fates, and Effects.[ 11 ]

As result of human activities, about 700,000 tons of petroleum is released annually into the sea worldwide. Processes such as petroleum extraction, transportation, and consumption can cause soil and groundwater contamination in case of equipment failure or operation errors and other reasons. Petroleum extraction can result in release of both crude oil and refined products as a result of human activities associated with efforts to explore and produce petroleum. The nature and size of these releases are highly variable—see Table 3 for the largest oil spills observed until 2010[ 12 ]—and can include accidental spills of crude oil from platforms and blowouts such as that of the oil rig Deepwater Horizon in the Gulf of Mexico in April 2010 or slow chronic releases of water produced from oil- or gas- bearing formations during extraction. Under current industry practices, this “produced water” is treated to separate from crude oil and either injected back into the reservoir or discharged overboard. Produced water is the largest single wastewater stream in oil and gas production. The amount of produced water from a reservoir varies widely and increases over time as the reservoir is depleted. Petroleum transportation can result also in releases of dramatically varying sizes of petroleum products (not just crude oil) from major incidents (mostly from tankers, such as the one in 1979 off the coast of Tobago, when two tankers collided and one of these, the Atlantic Empress, sank, losing all its freight) to relatively small operational releases that occur regularly, such as those from pipelines.

Table 3   Top 10 Oil Spills in the World as of 2010

 

Incident

Location

Year

Type of Incident

Magnitude of Oil Spill (gallons)

1

Gulf War

Kuwait

1991

Oil spill due to war action and sabotage of oil drilling stations and pipelines, encompassing also the dumping of the charge of several oil tankers into the Persian Gulf by Iraqi troops during the Gulf War.

520,000,000

2

Deepwater Horizon

Gulf of Mexico

2010

Oil spill as a consequence of a methane blowout (which could not be prevented due to a technical problem) at the oil rig Deepwater Horizon, which caused an explosion and and the subsequent loss of the oil drilling platform. The well continued to leak for over 100 days.

172,000,000

3

Ixtoc I

Mexico

1979

After an unexpected blowout at the offshore oil rig Ixtoc 1 in the Gulf of Mexico, the platform exploded and collapsed. Oil escaped freely from the well for almost 1 year until the well could be capped.

138,000,000

4

Atlantic Empress/ Aegean Captain

Trinidad and Tobago

1979

Collision of two ships, the Aegean Captain and the supertanker Atlantic Empress, during a heavy storm in the Caribbean Sea. The Atlantic Empress exploded, sank, and lost its freight.

90,000,000

5

Fergana Valley/ Mingbulak

Russia

1992

Technical failure of an oil well in the Fergana Valley located between Kyrgyzstan and Uzbekistan from which oil blew out for a period of 8 months.

88,000,000

6

Nowruz Oil Field

Persian Gulf

1983

Collision of an oil tanker with an oil platform at the Nowruz Oil Field during the Iran–Iraq War. After the oil drilling platform collapsed, the wellhead was destroyed and leaked oil into the Persian Gulf for more than 6 months before being capped. A similar event at the same oilfield resulted directly form war action.

80,000,000

7

Castillo de Bellver

South Africa

1983

A fire at the tanker Castillo de Bellver caused the ship to drift and then break into two separate pieces. Relatively little damage was done to the South African coastline since the oil may have sunk into the sea or burned during the fire.

79,000,000

8

The Amoco Cadiz

France

1978

The crude oil carrier Amoco Cadiz ran aground off the French Atlantic coast and finally spilt into halves, whereby it lost its complete freight, which contaminated 200 km of the French coastline.

69,000,000

9

ABT Summer

Angola

1991

Following a fire aboard the oil tanker ABT Summer, it sank and all its freight either leaked to the sea or sank to the ground about 900 miles from the coast of Angola.

51,000,000

10

The MT Haven

Genova, Italy

1991

After unloading the oil tanker MT Haven, a fire broke out, followed by explosions after which the ship sank and continued to leak oil for 12 years.

45,000,000

Source: Adapted from Top 10 Worst Oil Spills.[ 12 ]

Releases that occur during the consumption of petroleum, whether by individual car and boat owners, non-tank vessels, or runoff from urban or industrial areas, are typically small but frequent and widespread and are responsible for the vast majority (70%) of petroleum introduced to the environment through human activity.

Because crude oil and petroleum products are a complex and highly variable mixture of hundreds to thousands of individual hydrocarbon compounds, characterizing the risks posed by petroleum-contaminated soil and water has proven to be difficult and inexact. It is very important to have an understanding of the toxicology, analytical science, environmental fate and behavior, risk, and technological implications of petroleum hydrocarbons in order to interpret, evaluate the risk of, and make decisions about the hazardous effect to and ensure the appropriate protection of the environment.

General Chemical Composition Features of Crude Oils and Petroleum Products

Crude oil is an extremely complex mixture of several thousands of different compounds; its compositions and physical properties vary widely depending on the source from which the oils are produced, the geologic environment, and location in which they migrated and from which they are extracted. The nature of the refining processes has an effect on crude oil compositions as well. As indicated in Table 4, petroleum and petroleum products contain primarily hydrocarbons, heteroatom compounds, and relatively small concentrations of (organo)metallic constituents.[ 13 , 14 ] The complexity of petroleum and petroleum products increases with carbon number of its constituents, so it is impossible to identify all components. Petroleum and petroleum products are typically characterized in terms of boiling range and approximate carbon number. Raw petroleum is usually dark brown or almost black, although some fields deliver a greenish or sometimes yellow petroleum. Depending upon the oil field and the way the petroleum composition was formed, the crude oil will also differ in viscosity. The composition of crude oil impacts certain physical properties of the oil, and it is these physical properties (e.g., density or viscosity) by which crude oils are generally characterized, classified, and traded. These physical properties can be used to classify crude oils as light, medium, or heavy. The American Petroleum Institute (API) gravity[ 15 ] is a measure of the specific gravity of a petroleum liquid compared with water (API = 10). Light oils are defined as having an API < 22.3, heavy oils are those with API > 31.1, and medium oils have an API gravity between 22.3 and 31.1.

Table 4   Main Constituents of Petroleum Hydrocarbons and Representative Examples

Petroleum Hydrocarbon Compounds

Aliphatics/Alicyclics

Aromatics

Saturated hydrocarbons

Unsaturated hydrocarbons

Benzene and alkylbenzenes (BTEX)

Polynuclear aromatics (PAH)

Heterocyclic compounds

Alkanes(paraffins)

Cycloalkanes

Alkenes (olefins)

Alkynes (acetylenes)

Single carbon bonds, straight and branched structure

Straight and cyclic structure

One or more double carbon bonds, straight, branched, or cyclic

One or more triple carbon bonds, straight, branched, or cyclic

Single aromatic ring or with attached functional group

Two or more aromatic rings fused together, can be with attached functional group

Aromatic ring structures with one or more heteroatom (N, S, O) in the ring

CnH2 n +2

CnH2 n

CnH2 n

CnH2 n -2

n-Decane

Cyclohexane

1-Octene

1-Hexyne

Benzol

Naphthalene

Pyrrole

3-Methylnonane

Toluene

Regardless of the complexity, petroleum compounds can be separated into two major categories: hydrocarbons and non-hydrocarbons. Hydrocarbons (compounds composed solely of carbon and hydrogen) comprise the majority of the components in most petroleum products and are the compounds that are primarily (but not always) measured as total petroleum hydrocarbons (TPH).[ 16 ] The nonhydrocarbon components are heterocyclic hydrocarbons (compounds containing heteroatoms such as sulfur, nitrogen, or oxygen in addition to carbon and hydrogen). These heterocyclic hydrocarbons are typically present in oils at relatively low concentrations and can be found in most refined motor fuels as they are concentrated in the heavier fractions and residues during refining. Most organic nitrogen hydrocarbons in crude oils are present as alkylated aromatic heterocycles, mostly with a pyrrolic structure. Crude oils also contain small amounts of organometallic compounds (of nickel, vanadium, and other metals up to atomic number 42, with the exception of rubidium and niobium) and inorganic salts. Although, depending on the analytical method, sulfur-, oxygen-, and nitrogen-containing compounds are sometimes included in the value reported as TPH concentration, they do not fall under the definition of petroleum hydrocarbons in the strict sense.[ 16 ]

Depending on the structure of petroleum hydrocarbons, the individual compounds are grouped into aliphatic(saturated and unsaturated) hydrocarbons and aromatics. Saturated hydrocarbons are the major class of compounds found in crude oil. The common names of these types of compounds are alkanes and isoalkanes or, as used in petroleum industry, paraffins and isoparaffins, respectively. Unsaturated hydrocarbons have at least one multiple bond (double bond [alkenes] or triple bond [alkynes]), and they are typically not present in crude oil but can be formed during the cracking process. Aromatic hydrocarbons are based on the benzene ring structure and are further categorized depending on the number of rings. Benzene rings are very stable and therefore persistent in the environment, and particularly, the mono- and polycyclic aromatic compounds can have toxic effects on organisms. Aromatic hydrocarbons with one benzene ring and with one or more side chains are alkyl benzenes and include benzene; toluene; ethylbenzene; and o-, p-, and m-xylenes (BTEX). This class of compounds has significant water solubility and is more mobile in the environment. Polycyclic aromatic hydrocarbons (PAHs) are aromatic compounds with two or more fused aromatic rings. Occurrence of PAH compounds in oils is dominated almost completely by the C1- to C4-alkylated homologues of the parent PAH, in particular, for naphthalene, phenanthrene, dibenzothiophene (a sulfur-containing aromatic heterocycle), fluorine, and chrysene. These alkylated PAH homologues form the basis of chemical characterization and identification of oil spills.[ 17 , 18 ] A typical crude oil may contain 0.2% to more than 7% total PAHs. Of the hydrocarbon compounds common in petroleum, PAHs appear to pose the greatest toxicity to the environment.

Different crude oil sources usually have a unique hydrocarbon composition.[ 19 , 20 ] The actual overall properties of each different petroleum source are defined by the percentage of the main hydrocarbons found within petroleum as part of the petroleum composition. The percentages for these hydrocarbons can vary greatly. It gives the crude oil a quite-specific compound personality depending on geographic region. The typical percentage of hydrocarbons (although covering very wide ranges) is as follows: paraffins (15%–60%), naphthenes (30%–60%), aromatics (3%–30%), and asphaltenes making up the remainder. Furthermore, due to differences in refining technologies and refinery operating conditions, each refining process has a distinct impact on the hydrocarbon composition of the product.

Refined petroleum products are primarily produced through distillation processes that separate fractions from crude oil according to their boiling ranges. Production processes may also be directed to increase the yield of low-molecular-weight fractions, reduce the concentration of undesirable sulfur and nitrogen components, and incorporate performance-enhancing additives. Therefore, each petroleum product has its unique, product-specific hydrocarbon pattern. The petroleum products are composed of both aliphatic and aromatic hydrocarbons in a range of molecules that include C6 and greater. The different classes of compounds contained in various petroleum products are summarized in Table 5.[ 20 , 21 ] The main products are gasoline (benzene), naphtha/solvents, jet fuels, kerosene, diesel fuel, and lubricating (motor) oils. Due to the variety of components in petroleum, they are typically characterized using the boiling range of the mixture and the carbon number rather than individual components. For example, diesel is a fraction with boiling points between 200°C and 325°C and is represented as C10–C22.

Table 5   Overview of Petroleum Products with Respect to Boiling Point Ranges, Approximate Carbon Number, and Average Percentage Amount of Aliphatic and Aromatic Compounds

Fractions

Hydrocarbons

 

Boiling Range

<C7 (% w/w)

C7–C10 (% w/w)

C10–C40 (% w/w)

>C40 (% w/w)

Aliphatic

Aromatic

Statfjord C (39.1) a

11.6

18.1

56.6

13.7

Crude oil (API = 18.7)

0.9

3.0

63.2

32.8

Grane a

Normal benzene b

40–200°C

~100 (C5–C12)

~70%

20%–50%

Jet fuel b

150–300oC

~100 (C6–C14, C16)

80%–90%

10–20%

Kerosene b

150–300oC

~100 (C6, C9–C16)

60%–80%

5%–20%

Diesel b

200–325oC

 

~100 (C10–C22)

60%–90%

30%–40%

Light heating oil b

200–325oC

~100 (C10–C22)

Lubricant or motor oil b

325–600oC

~100 (C20–C40)

70%–90%

10%–30%

Heavy heating oil b

325–600oC

~100 (C20–C50)

Notes:

a  Source: Data from Crude Oil Assays.[ 20 ]

b  Source: Data from Statoil Web site.[ 21 ]

While a physical property such as boiling range may establish the initial product specification, other finer specifications define their ultimate use in certain applications. A lighter, less dense, raw petroleum composition with a composition that contains higher percentages of hydrocarbons is much more profitable as a fuel source. On the other hand, other denser petroleum compositions with a less flammable level of hydrocarbons and containing higher levels of sulfur are expensive to refine into a fuel and are therefore more suitable for plastics manufacturing and other uses. In contrast to the ever-increasing demand, the world’s reserves of light petroleum (light crude oil) are severely depleted, and refineries are forced to refine and process more and more heavy crude oil and bitumen.

Petroleum fractions are among the most complex samples an analyst can face in terms of the number of compounds present. The characterization of petroleum fractions is typically done by gas chromatography (GC). As can be seen in Figure 1, the petroleum products contain such a large number of hydrocarbon constituents that complete chromatographic separation is not possible. Even then, GC remains the most informative analytical technique, providing both quantitative information (deduced from the total signal recorded in a chromatogram) and qualitative information, which derives from the fact that the retention times in the chromatograms can be correlated with the boiling points of the compounds contained in the petroleum. To illustrate the complexity of chemical composition of petroleum products, Figure 2 shows the chromatograms for six different petroleum products, including a crude oil with API of 18.7 and the BAM (Bundesanstalt für Materialprüfung, Berlin) petroleum hydrocarbon standard. The BAM standard K-010 is a certified reference material for the determination of mineral hydrocarbons, which is a synthetic mixture of a diesel and a lubricating oil. It is evident that these six samples are very different according to their carbon ranges. The difference is clearly seen from the comparison of their chromatograms. The volatile fuel with a content of hydrocarbons with less than 10 C atoms (benzene and premium gasoline) has the majority of its constituents at the beginning of chromatogram (Figure 2c). The peaks in the chromatogram of diesel are shifted to the retention time window where hydrocarbons from C10 to C22 are eluted (Figure 2d). In turn, the chromatogram of motor oil shows a characteristic “bump” (because the fraction of saturated alkanes is very small) situated in the region where heavier hydrocarbons C20–C40 are eluted (Figure 2e). Thus, GC- based methods provide important qualitative information, which in the ideal case even allows the assignment of the source of contamination. This is proven by the comparison of chromatograms of different oil samples (Figure 2).

Chromatogram of a mixture of petroleum products (diesel and
                              lubricating oil, 1:1), obtained by GC with FID.

Figure 1   Chromatogram of a mixture of petroleum products (diesel and lubricating oil, 1:1), obtained by GC with FID.

Comparison of chromatograms of different oil samples: (a) BAM; (b)
                              crude oil (API = 18.7); (c) gasoline; (d) diesel; (e) motor oil; and
                              (f) heavy heating oil with the same concentration (20 ppm oil in
                              water) obtained by GC-FID method

Figure 2   Comparison of chromatograms of different oil samples: (a) BAM; (b) crude oil (API = 18.7); (c) gasoline; (d) diesel; (e) motor oil; and (f) heavy heating oil with the same concentration (20 ppm oil in water) obtained by GC-FID method

Fate of Petroleum Hydrocarbons in the Environment

The effects of petroleum hydrocarbons entering the environment are a complex function of the magnitude and the rate of release; the nature of the released petroleum (its physicochemical properties and, in particular, the amount of toxic compounds it may contain); and the affected geographical, hydrogeological, and biological ecosystem. The fate of petroleum-type pollutants in the environment has been investigated in many studies.[ 22 ] Complex transformation and degradation processes of oil in the environment start from its first contact with the atmosphere, seawater, and soil. They depend on the physical properties (volatility, solubility, etc.), as well as on the chemical properties (chemical composition) of the oil. While the former are responsible for transport, or diffusion of the petroleum hydrocarbons in the environment, the latter are responsible for their chemical, photo-, and microbial degradation. The main processes affecting the environmental fate of petroleum hydrocarbons after their release to the environment are thus their volatilization, dissolution/dispersion and emulsification in water, adsorption to soil, oxidation, destruction, and biodegradation.[ 23 , 24 ] In addition to the parameters that characterize the oil’s composition, reactivity, and toxicity, the environmental conditions, i.e., the meteorological and hydrological factors, also play an important role in the fate of petroleum hydrocarbons.

When petroleum hydrocarbons are released to the water column, certain fractions will float on top and form thin surface films. This process is controlled by the viscosity of the oil and the surface tension of water. A spill of 1 ton of oil can disperse over a radius of 50 m in 10 min, forming a slick 10 mm thick. Later, it spreads, gets thinner, and covers an area of up to 12 km2.[ 11 ] It should be pointed out that much of the environmental and ecological damage caused by oil spills actually is due to this oil film that covers the surface of the sea, or the coastline, thus physically impairing birds and other animals and causing suffocation of fish as oxygen will not permeate the oil layers to a sufficient degree anymore. In the first days after the spill, the volatile compounds from oil evaporate. Only a small proportion of the hydrocarbon constituents of petroleum products are significantly soluble in water. Dissolution takes more time compared with evaporation, considering that most oil components are soluble in water only to a limited degree (although the degradation products typically are more polar and thus more soluble). Other heavier fractions (up to 10%–30%) will accumulate in the sediment at the bottom of the water, which may affect bottom-feeding fish and organisms. This happens mainly in the narrow coastal zone and shallow waters, where water is intensively mixing.

Crude oil released to the soil may percolate and reach the groundwater. Because petroleum has a lower specific gravity than water, free (undissolved) product and most dissolved contamination are usually concentrated near the top of the groundwater.[ 25 ] This may then lead to a fractionation of the original complex mixture, depending on the chemical properties of the compound. Some of these compounds will evaporate, while others will dissolve into the groundwater and be diffused from the release area. Other compounds will adsorb to soil or sediments and will remain there for a long period of time, while others will be metabolized by organisms found in the soil.[ 26 , 27 ]

While evaporation and dissolution redistribute the oil, photochemical oxidation and bacterial degradation transform it. Where crude oil is exposed to sunlight and oxygen in the environment, both photooxidation and aerobic microbial oxidation take place. The photochemical oxidation of hydrocarbons is dependent upon ultraviolet (UV) radiation and will therefore occur only in the upper surface layers. The aromatic hydrocarbons absorb UV radiation with high efficiency and are transformed mainly into hydrogen peroxides. Alkanes are much less efficient in absorbing UV radiation, and only small quantities are transformed by this process. The final products of oxidation (hydroperoxides, phenols, carboxylic acids, ketones, aldehydes, and others) usually have increased water solubility and toxicity. Where oxygen and sunlight are excluded in anoxic environments, anaerobic microbial oxidation takes place.[ 28 , 29 ]

Generally, saturated alkanes are more quickly degraded by microorganisms than aromatic compounds; alkanes and smaller-sized aromatics are degraded before branched alkanes, multiring and substituted aromatics, and cyclic compounds.[ 30 , 31 ] Polar petroleum compounds such as sulfur- and nitrogen-containing species are the most resistant to microbial degradation. Complex structures (e.g., branched methyl groups) and the stability of hydrocarbons decrease the rates of mineralization, which are likely a consequence of the greater stability of carbon–carbon bonds in aromatic rings than in straight-chain compounds. Emulsification also provides greater surface area for microorganisms to attach.

It has been shown in experiments that n-alkanes are among the most biodegradable hydrocarbons, and therefore, they are easily broken down and preferentially depleted from soil samples.[ 32 ] Also, it has been proven in simulation experiments of the biodegradation of two different samples of crude petroleum (paraffinic and naphthenic type) that microbial cultures that were isolated as dominant microorganisms from the surface of a wastewater canal of an oil refinery (most abundant species: Phormidium foveolarum, filamentous Cyanobacteria [blue-green algae] and Achnanthes minutissima, diatoms, algae) show a strongly differentiated degradation behavior with clear preference for the degradation of n-alkanes and isoprenoid aliphatic alkanes.[ 33 ] As can be seen in Figure 3, the largest degree of biodegradation was achieved in a medium containing the base nutrients Ca(NO3)2.4H2O, K2HPO4.7H2O, KCl, FeCl2, and K2SO4, at pH ≈ 8 and exposed to light. Biodegradation activity is somewhat lower with the same medium in the dark. With a medium containing not only the nutrient broth but also organic compounds (tryptone, yeast extract, glucose, at pH ≈ 7), degradation occurs at a much lower rate, especially without light.

Gas chromatograms of the alkane fractions derived from crude oil
                              Sirakovo (Sir, paraffinic type) after 90 days of simulated
                              biodegradation with

Figure 3   Gas chromatograms of the alkane fractions derived from crude oil Sirakovo (Sir, paraffinic type) after 90 days of simulated biodegradation with Phormidium foveolarum and Achnanthes minutissima with inorganic medium in the light (Sir-1), with inorganic medium in the dark (Sir-2), with organic medium in the light (Sir-3), and with organic medium in the dark (Sir-4), together with chromatogram of alkane fraction typical for the control experiments (Sir-1C), pristane (Pr), phytane (Phyt).

Source: Adapted from Antić et al.[ 33 ]

When crude oil or petroleum products are accidentally released to the environment, they are immediately subjected to a variety of weathering processes that lead to compositional changes and to the depletion of certain hydrocarbon compounds. Weathering processes include all previously mentioned physicochemical processes, such as dissolution, evaporation, photooxidation, polymerization, adsorptive interactions between hydrocarbons and the soil, and some biological factors. Furthermore, due to the fact that the degree of biodegradation is different for different types of petroleum hydrocarbons and varies depending on their nature, the weathering rate also depends on the type of petroleum contaminant. If we thus observe in the analysis of petroleum hydrocarbon contaminants changing patterns of hydrocarbons with time, this may be either due to the segregation of the oil according to the physical properties or due to the action of bacteria and microorganisms. As these are able to degrade only certain classes of compounds, or at least they exhibit a strong preference for some over other compounds, characteristic changes of the hydrocarbon pattern will result, as observed by GC (Figure 3).

Possible Toxic Effects from Exposure to Petroleum Hydrocarbons

As it was discussed earlier, crude oil and petroleum products are complex mixtures of groups of compounds. Many of the compounds are apparently benign, but many others are known to have toxic effects. Due to petroleum hydrocarbon toxicity, spilled hydrocarbons pose a threat that affects not only the sea and land but also the lakes, rivers, and groundwater and can be harmful for animals and human health.

Much of what is known about the impacts of petroleum hydrocarbons comes from studies of catastrophic oil spills and chronic seeps. Large oil spills usually receive considerable public attention because of the obvious environmental damage, oil-coated shorelines, and dead or moribund wildlife, including, in particular, oiled seabirds and marine animals. The acute toxicity of petroleum hydrocarbons to marine organisms is dependent on the persistence and bioavailability of specific hydrocarbons. The exposure to them may alter an organism’s chances for survival and reproduction in the environment, and the narcotic effects of hydrocarbons on nerve transmission are a major biological factor in determining the ecologic impact of any release. Marine birds and mammals may be especially vulnerable to oil spills. In addition to acute effects such as high mortality, chronic, low-level exposure to hydrocarbons may affect reproductive performance and physiological impairment of seabirds and some marine mammals as well.[ 11 ] Petroleum contamination may also cause unfavorable impacts on nearby plants and animals. Plants growing in contaminated soils or water may die or appear distressed. In turn, natural seeps, leaking pipelines, and production discharges release small amounts of oil over long periods of time, resulting in chronic exposure of organisms to oil and oil chemical compounds. The lower-molecular-weight compounds are usually the more water-soluble components of a product, and hence, attention has also been paid to the water-soluble fractions of petroleum and related products. Concentrations in the environment are usually comparatively low, and chronic effects are usually more significant.[ 26 ] The persistence of some compounds such as PAH in sediments, especially in urban areas, is also an example of chronic pollution and toxicity.

Nowadays, humans can be exposed to petroleum hydrocarbons through ingestion of contaminated drinking water and soil residues; inhalation of vapors and airborne soils; and contact of contaminants with skin (dermal exposure) from many sources, including gasoline fumes at the pump, spilled crankcase oil on pavement, chemicals used at home or work, or certain pesticides that contain petroleum hydrocarbon components as solvents. Most petroleum hydrocarbon constituents will enter the bloodstream rapidly when inhaled or ingested. Incorporated petroleum hydrocarbons are widely distributed by the blood throughout the body and quickly are metabolized into less harmful compounds. Others may be degraded into more harmful chemicals. Even other compounds are distributed by the blood to other parts of the body and do not readily break down but are accumulated instead in fat tissue. The resorption of petroleum compounds through dermal tissue is slower; that is why direct exposure of the skin to petroleum hydrocarbons is generally harmless when exposure is only occasional and of short duration.

Studies on animals have shown effects on the lungs, central nervous system, liver, kidney, developing fetus, and reproductive system from exposure to petroleum compounds, generally after breathing or swallowing the compounds. Health impacts of exposure to petroleum contamination may include lung irritation, headaches, dizziness, fatigue, diarrhea, cramps, and nervous system effects. Benzene and other chemicals found in petroleum products have been determined to be carcinogenic (cause cancer). More information regarding toxicity of petroleum chemicals is available, for example, from the Agency for Toxic Substances and Diseases Registry (ATSDR), an agency of the U.S. Department of Health and Human Services,[ 34 ] or from the European Chemicals Agency.[ 35 ]

Oil products are complex mixtures of hundreds of chemicals, with each compound having its own toxicity characteristics. There are many difficulties associated with assessing the health effects of such complex mixtures with regard to hazardous waste site remediation. This means that the traditional approach of evaluating individual components is largely inappropriate. Toxicity information is in the best case available for the pure product; however, once a petroleum product is released to the environment, it changes its composition as a result of weathering. These compositional changes may be reflected in changes in the toxicity of the product.

One approach for assessing the toxicity of oil products is to use toxicity information from studies conducted on the whole product. A second approach is to identify and quantify all components and then consider their toxicities. This approach produces data that theoretically could be compared with the known toxicity of each compound. The impracticality of this approach stems from its high analytical cost and the lack of toxicity data for many of the component chemicals found in hydrocarbon mixtures. A third approach is to consider a series of hydrocarbon fractions and determine appropriate tolerable concentrations and toxicity specific for those fractions. A number of groups have examined such an approach, but the most widely accepted and internationally used are the ones developed by the Total Petroleum Hydrocarbons Criteria Working Group (TPHCWG) and the Massachusetts Department of Environmental Protection (MA DEP) in the United States, although they have been subject to adjustments in many cases. For example, in the United Kingdom, the TPHCWG approach is modified and extended to consider heavier hydrocarbon fractions. It has been developed as part of the Environment Agency’s[ 36 ] environment sciences program and published in documents related to petroleum hydro- carbons.[ 37 ]

The MA DEP introduced in 1994 the concept of petroleum hydrocarbon size-based fractions for use in evaluating the human health effects of exposure to complex mixtures of hydrocarbons[ 38 , 39 ] and provided oral toxicity values for each of the fractions. The toxicity value assigned for each fraction is used in dose–response evaluations. Cancer risks or hazard amounts are subsequently summed across the fractions to get the total values. The TPHCWG has developed and published a series of five monographs[ 16 , 40–42 ] detailing the data on petroleum hydrocarbons and, in addition, has developed tolerable intakes for a series of total hydrocarbon fractions. The TPHCWG independently identified largely similar groupings of hydrocarbon fractions with somewhat different toxicity values in 1997. Of the 250 individual compounds identified in petroleum by the TPHCWG, toxicity data were available for only 95. Of these 95, the TPHCWG concluded that there were sufficient data to develop toxicity criteria for only 25.

As there are differences in toxicity between different hydrocarbon compounds, it is impossible to accurately predict toxic effects of contamination for which only total hydrocarbon data are available. Health assessors often select surrogate or reference compounds (or combinations of compounds) to represent TPH so that toxicity and environmental fate can be evaluated. Correspondence dates relating the toxicologically derived hydrocarbon fractions and their toxicity values to the analytically defined reporting fractions (by MA DEP) are contained in Table 6 for ingestion and inhalation exposure. Inhaled or ingested volatile hydrocarbons have both general and specific effects. The toxicity values are represented as a reference dose (RfD), which is the U.S. Environmental Protection Agency’s (EPA’s) maximum acceptable oral dose of a toxic substance. Significant efforts have been undertaken by MA DEP to describe an approach for the evaluation of human health risks from ingestion exposure to complex petroleum hydrocarbon mixtures. The methods offered by MA DEP for determination of air-phase (APH), volatile (VPH), and extractable (EPH) petroleum hydrocarbons[43–45] are designed to complement and support the toxicological approach. The ranges of quantified hydrocarbons within each method and their reporting limits are shown in Table 7.

Table 6   Oral and Inhalation Toxicity Values by MA DEP for Petroleum Hydrocarbon Fractions and Individual Compounds Present in Petroleum Products

Toxicity Value, RfD

Carbon range

Compound

Inhalation mg/m3

Oral mg/kg/day

Critical Effect

Aliphatic

C5–C8

0.2

0.04

Neurotoxicity

n-Hexane

0.2

0.06

C9–C18

0.2

0.1

Neurotoxicity, hepatic, and hematological effects

C19–C32

NA

2

Liver granuloma

Aromatic

C6–C8

Use individual RfCs for compounds in this range

Benzene

NA

0.03

Toluene

0.4

0.2

BTEX

Ethylbenzene

1.0

0.1

Styrene

1.0

0.2

Xylene (o-, p-, m-)

NA

2

C9-C18

0.05

Body weight reduction; hepatic, renal, and developmental effects

Isopropylbenzene

0.4

0.1

Naphthalene

0.003

0.02

Acenaphthene

NA

0.06

Biphenyl

NA

0.05

Fluorene

NA

0.04

Anthracene

NA

0.3

Fluoranthene

NA

0.04

Pyrene

NA

0.03

C9–C32

0.3

Neurotoxicity

C19–C32

NA

Source: Adapted from The U.K. Approach for Evaluating Human Health Risks from Petroleum Hydrocarbons in Soil[ 37 ] and Interim Final Petroleum Report Development of Health-Based Alternative to the Total Petroleum Hydrocarbon TPH Parameter.[ 38 ]

NA, not applicable.

Table 7   The Ranges of Hydrocarbons Quantified within the Methods for Determination of APH, VPH, and EPH by MA DEP and Their Reporting Limits

APH 28°C–218°C

VPH 36°C–220oC

EPH 150°C–265oC

 

Aliphatic

C5–C8

C9–C12

1C5–C8

C9–C12

C9–C10

C9–C18

C19–C36

Aromatic

C9–C10

Reporting limits

C11–C22

PAH

For the individual target analytes

 

 

 

 

 

 

 

In air phase

2–5 g/m3

 

 

 

In soil

 

0.05–0.25 mg/kg

20 mg/kg

0.2–1 mg/kg

In water

 

1–5 μ g/L

100μ g/L

2–5 μg/L

For the collective

 

 

 

hydrocarbon ranges

 

 

 

In air phase

10–12 g/m3

 

 

In soil

 

5–10 mg/kg

20 mg/kg

In water

 

100–150 μg/L

100 μg/L

Source: Adapted from Interim Final Petroleum Report Development of Health-Based Alternative to the Total Petroleum Hydrocarbon TPH Parameter.[ 38 ]

The components of petroleum can be generally divided into broad chemical classes: alkanes, cycloalkanes, alkenes, and aromatics. A review of Table 6 shows that a U.S. EPA RfD is available for only one alkane, n-hexane. In general terms, alkanes have relatively low acute toxicity, but alkanes having carbon numbers in the range of C5–C12 have narcotic properties, particularly following inhalation exposure to high concentrations, because of their relatively high volatility and low solubility in water. Repeated exposure to high concentrations, for example, of n-hexane (RfD, 0.06 mg/kg/day) may lead to irreversible effects on the nervous system. Hexane is considered to be the most toxic compound in the C5–C8 aliphatic fraction. No RfDs are available for other alkanes, nor for any cycloalkane or alkene. Alkenes exhibit little toxicity other than weak anesthetic properties. Alkanes and cycloalkanes are treated similarly and have similar toxic effects.

Aromatic compounds with less than nine carbon atoms (such as BTEX) are evaluated separately because the toxicity values for each are well supported and these compounds have a wide range of toxicity. However, most of the smaller aromatic compounds have low toxicity, with the exception of benzene, which is a known human carcinogen (RfD, 0.029 mg/kg/day). Most petroleum hydrocarbon mixtures contain very low concentrations of PAHs. The major concern regarding PAHs is the potential carcinogenicity of some of these. Benzo(a)pyrene and benz(a)anthracene are classified as probable human carcinogens. Benzo(a)pyrene is normally considered to be the most potent carcinogenic PAH, but the carcinogenic potency of most PAHs is not well characterized. In case of spills of petroleum products affecting water, PAHs are not usually a specific concern; however, this concern becomes more specific if these compounds are released into the soil due to a bioaccumulation of PAH in soil.

Different regulations and guidelines to protect public health have been developed. These public health statements tell as well about petroleum hydrocarbons and the effects of exposure. The U.S. EPA[ 46 ] identifies the most serious hazardous waste sites in the United States. The EPA lists certain wastes containing petroleum hydrocarbons as hazardous. It regulates certain petroleum fractions, products, and some individual petroleum compounds. General health and safety data are as well discussed by the Energy Institute,[ 7 ] which is the main professional organization for the energy industry within the United Kingdom that promotes the safe, environmentally responsible, and efficient supply and use of energy in all its forms and applications. The Occupational Safety and Health Administration and the Food and Drug Administration are other agencies that develop regulations for toxic substances in the United States. The information provided by all of them is regularly updated as more information becomes available. The Dutch National Institute for Public Health and the Environment (RIVM), has been involved in a number of studies on risk assessment for petroleum hydrocarbons which were commissioned by the Dutch government and the European Commission.[ 47 ] Also the U.K. Environment Agency, mentioned before, is the leading public body protecting and improving the environment in the United Kingdom, including protection from petroleum contaminations.

Total Petroleum Hydrocarbons and Analytical Methods for Determination of Petroleum Hydrocarbons in Environmental Media

Due to the compositional complexity of petroleum products, it is impossible to assess the extent of petroleum hydrocarbon contamination by directly measuring the concentration of each hydrocarbon contaminant. For this reason, at the present time, no single analytical method is capable of providing comprehensive chemical information on petroleum contaminants. Total petroleum hydrocarbon is one parameter and definition that is currently widely used for expressing the total concentration of nonpolar petroleum hydrocarbons in soil, water, or other investigated samples. In the United States, for example, there are no federal regulations or guidelines for TPH in general. Many states have standards for controlling the concentrations of petroleum hydrocarbons or components of petroleum products. These are designed to protect the public from the possible harmful health effects of these chemicals. Analytical methods are specified as well, many of which are considered to be methods for TPH. These generate basic information that is a surrogate for contamination, such as a single TPH concentration. Such data are not suitable for risk assessment. However, they are relatively quick and easy to obtain and can offer useful preliminary information.

The term TPH is widely used, but it is rarely well defined. In essence, TPH is defined by the analytical method—in other words, estimates of TPH concentration often vary depending on the analytical method used to measure it. Thus, the ATSDR defines the TPH as a term used to describe a broad family of several hundred chemical compounds that originally come from crude oil. In this sense, TPH is really a mixture of chemicals. As per the TPHCWG, TPH, also called “hydrocarbon index,” refers sometimes to mineral oil, hydrocarbon oil, extractable hydrocarbon, oil, and grease. The TPHCWG also says that the TPH measurement is the total concentration of the hydrocarbons extracted and measured by a particular method, and it depends on the analytical method used for determination. According to the MA DEP, the TPH is also a loosely defined parameter, which can be quantified using a number of different analyses, and this parameter is an estimate of the total concentration of petroleum hydrocarbons in a sample. Again, depending on the analytical method used to quantify TPH, the TPH concentration may represent the entire range of petroleum hydrocarbons from C9 to C36 or the sum of concentrations of a number of single compounds (for instance, BTEX) and groups of compounds (fractions, e.g., primarily aliphatics C9–C18, C19-C36, and aromatics C11–C20). Great improvements in the definition and analysis of TPH were finally introduced by the International Organization for Standardization (ISO)[ 48 ] in 2000, when it published the standard method ISO 9377-2:2000[ 49 ] for the quality control of water in which a method for the determination of the hydrocarbon oil index within the C10–C40 range in waters by means of GC is specified. The definition of “hydrocarbon oil index by GC-FID” was introduced, which defines the fraction of compounds extractable with a hydrocarbon solvent, boiling point between 36°C and 69°C, not adsorbed on Florisil, and which may be chromatographed with retention times between those of n-decane (C10H22) and n-tetracontane (C40H82). (Substances complying with this definition are long-chain or branched aliphatic, alicyclic, aromatic, or alkyl -substituted aromatic hydrocarbons.)

The TPHCWG and MA DEP evaluated the risk implications and arrived at the conclusion that TPH concentration data cannot be used for a quantitative estimation of the human health risk. The same concentration of TPH may represent very different compositions and very different risks to human health and the environment because the TPH parameter includes a number of compounds of differing toxicities and the health effects associated with exposure to particular concentrations of TPH cannot be determined. For example, two sites may have the same amount of TPH, but constituents at one site may include carcinogenic compounds while these compounds may be absent at the other site. If TPH data indicate that there may be significant contamination of environmental media, then fractionated measurements and the separate determination of BTEX compounds and PAHs are necessary so that potential risk to human health can be quantitatively assessed.[ 50 ] The hydrocarbon index is thus a good indicator of the (magnitude of the) relative contamination of oil; however, it will not be suitable to give a true representation of the actual concentration of TPH in the investigated sample. There are several reasons why TPH data do not provide the ideal information for investigated samples and do not establish target cleanup criteria. This is due to many factors including the complex nature of petroleum hydrocarbons, their interaction with the environment over time, and the non-specificity of some of the methods used. The scope of the methods used for TPH determination varies greatly. There are few, if any, methods that are capable of quantifying all hydrocarbons without interference from non-hydrocarbons. All methods are subject to interferences from non-hydrocarbons, some to a greater extent than others.

There are numerous established analytical methods that are available for detecting, measuring, or monitoring TPH and its metabolites. Analytical methods used for analysis of petroleum hydrocarbons in environmental media should provide a sufficient degree of robustness. At the current time, however, the correctness and precision of results for the petroleum hydrocarbon determination strongly depend on the proper choice of method and measurement parameters whose correct selection is left to the judgment of the analyst. Besides methods that measure the TPH concentration, two other types of methods can be distinguished. These are methods that measure the concentration of a group or fraction of petroleum compounds and methods that measure individual petroleum constituent concentrations. For product identification, the results of analyses of the petroleum groups or fractions can be useful because they separate and quantify different categories of hydrocarbons. Individual constituent methods quantify concentrations of specific compounds that might be present in petroleum-contaminated samples, such as BTEX and PAHs, which can be used to evaluate human health risk.

There are several basic steps related to the separation of analytes of interest from a sample matrix prior to their measurement, such as extraction, concentration, and cleanup. These steps are common to the analytical processes for all methods, irrespective of the method type or the environmental matrix. Each of these steps together with the sampling, which is also an important step in performing petroleum analyses, affects the final result and has a certain impact onto the measurement uncertainty.[ 51 , 52 ]

Sample taking and sample handling have been recognized as probably the most significant factors that contribute random errors and uncertainties in the analysis of offshore oil in produced water. There are some general guidelines available through a number of studies that have been carried out on this subject. To separate the analytes from the matrix, extraction is performed using one of the many available extraction methods. Heating of the sample or purging with an inert gas can be used in the analysis of volatile compounds; solid-phase extraction or extraction into a solvent is usually applied for water samples, the latter extraction method also being used for soil samples. For some types of solid samples, the extraction efficiency depends on the extraction method and time. However, ultrasonication and extraction by shaking are equally used for this purpose. It was demonstrated by some studies that extraction and cleanup are the most crucial steps in sample preparation procedures. According to the results. the most critical factors affecting TPH recovery are extraction solvent and type of cosolvent, extraction time, adsorbent and its mass, and the TPH concentration.[ 53 ] The results of a study where the occurrence of matrix effects in the gas chromatographic determination of petroleum hydrocarbons in soil was evaluated indicate that solid-phase extraction does not appear to be effective enough in removing interfering matrix components from the extract.[ 54 ]

Most of the methods for the determination of TPH involve a cleanup step using Florisil (a particular form of magnesium silicate) and sodium sulfate (anhydrous), which essentially aims at removing the polar, non-petroleum hydrocarbons of biological origin and remaining traces of water. It appears that the found hydrocarbon concentration strongly depends on the used cleanup technique. The efficiency of the cleanup procedure for removing polar compounds is not limited to heteroatomic substances like O-, N-, or Cl-containing compounds. Also, some hydrocarbons have a tendency to adsorb on Florisil, e.g., aromatic compounds with p- electrons or alkyl aromatics. The TPH recoveries after a cleanup procedure might depend on the composition of the oil investigated. Lower TPH recoveries may be expected for oils containing high concentrations of unsaturated hydrocarbons or PAHs. Also, lubricating oils often contain different amounts and types of (non-petrogenic) additives that may behave differently from the other compounds during the cleanup procedure.[ 55 ] The results demonstrate also that the ratio of Florisil amount and extract volume are of importance for the recovery of the purified extracts.[ 56 ]

The three most commonly used TPH testing methods include GC,[ 49 , 57–60 ] infrared absorption (IR),[ 61 , 62 ] and gravimetric analysis.[63–65] Conventional TPH methods are summarized in Table 8.

Table 8   Summary of Common TPH Methods

Analytical Method

Method Name

Matrix

Scope of Method

Carbon Range

Approximate Detection Limits

Advantages

Limitations

Reference

GC based

DIN ISO 9377-2:2000

Water

Solvent (hydrocarbon) extraction, cleanup using Florisil, evaporation, 1 μL injection, GC-FID

C10-C40

0.1 mg/L

Detects broad range of hydrocarbons; provides information (e.g., a chromatogram) for identification

Does not quantify below C10; chlorinated compounds can be quantified as TPH

[49]

OSPAR (2007)

Water

n-Pentane extraction, cleanup using Florisil, 50 μL injection, GC-FID

C7–C40 + TEX compounds

0.1 mg/L

Does not need preconcentration step; detect broad range of hydrocarbons and polar hydrocarbons; provide information for identification

Does not quantify below C7

[57s]

DIN ISO 16703:2005–12

Soil

Acetone/n-heptane extraction, cleanup using Florisil, evaporation, GC-FID

C10–C40

10 mg/kg

Detects broad range of hydrocarbons; provide information (e.g., a chromatogram) for identification

Does not quantify below C10; chlorinated compounds can be quantified as TPH

[58]

DIN EN 14039:2004

Wastes

Acetone/n-heptane extraction, cleanup using Florisil, evaporation, GC-FID

C10–C40

10 mg/kg

[59]

IR based

EPA 418.1 (1991/1992)

Water, soil

Freon extraction, silica gel treatment to remove polar compounds

Most hydrocarbons with exception of volatile and very high hydrocarbons

1 mg/mL in water, 10 mg/kg in soil

Technique is simple, quick, and inexpensive

Freon is banned now; low sensitivity; lack of specificity; prone to interference; provides quantitation only

[62]

ASTM D7678-11 (2011)

Water, wastewater

Solvent (cyclic aliphatic hydrocarbon) extraction, cleanup using Florisil, IR Absorption in the region of 1370–1380 cm–1 (7.25–7.30 mm)

Most hydrocarbons with volatile

0.5 mg/mL

Technique is simple, very quick; a more complete fraction of extracted petroleum hydrocarbon is accessible

[61]

Gravimetry

EPA 413.1 (1979) ASTM D4281– 95(2005)el

Most appropriate for wastewater, sludge, sediment

Freon extraction, solvent evaporation

Anything that is extractable (with exception of volatiles which are lost)

5 mg/mL in water, 50 mg/kg in soil

Technique is simple, quick, and inexpensive

Freon is banned now; low sensitivity; lack of specificity not suitable for low boiling fractions; prone to interference (organic acids, phenols, and other polar hydrocarbons); provides quantitation only

[63,65]

EPA 1664 (1999)

Most appropriate for water and wastewater

n-Hexane extraction, silica gel treatment to remove polar compounds, solvent evaporation

Anything that is extractable (with exception of volatiles which are lost)

5 mg/mL

Technique is simple, quick, and inexpensive

Low sensitivity; lack of specificity not suitable for low boiling fractions; prone to interference; provides quantitation only

[64]

Methods based on solvent extraction followed by quantitative IR measurement (at a frequency of 2930 cm-1, which corresponds to the stretching vibration of aliphatic CH2 groups) have been widely used in the past for TPH measurement because they are simple, quick, and inexpensive. However, the use of these methods has been discontinued, since the sale and use of Freons (required for the extraction of hydrocarbons from the sample) is no longer allowed, and Freons are generally phased out worldwide due to their ozone layer–destructing potential. Recently, a new IR-based method was introduced, based on Freon- free extraction. This method defines oil and grease in water and wastewater as the fraction that is extractable with a cyclic aliphatic hydrocarbon (for example, cyclohexane) and measured by IR absorption in the narrow spectral region of 1370–1380 cm–1 (which corresponds to the excitation frequency of the symmetrical deformation vibration of CH3 groups) using mid-IR quantum cascade lasers.[ 62 ] The method also considers the volatile fraction of petroleum hydrocarbons, which is lost by gravimetric methods that require solvent evaporation prior to weighing, as well as by solventless IR methods that require drying of the employed solid-phase material prior to measurement. Similarly, a more complete fraction of extracted petroleum hydrocarbon is accessible by this method as compared with GC methods that use a time window for quantification, as petroleum hydrocarbons eluting outside these windows are also quantified. On the other hand, IR-based methods hardly provide any information on the chemical composition of the oil or the presence or absence of other relevant compounds (aromatics, PAHs). In contrast, they even detect compounds that are not typically considered as TPH, such as surfactants, which also may absorb IR radiation due to the presence of CH bonds. However, this statement is only partially true, since it depends mainly on the cleanup whether the IR method determines also compounds other than the TPH.

Gravimetric-based methods are also simple, quick, and inexpensive; they measure anything that is extractable by a solvent, not removed during solvent evaporation, and capable of being weighed. Consequently, they do not offer any selectivity or information on the type of oil detected. Gravimetric-based methods may be useful for oily sludges and wastewaters at high(er) concentrations but are not suitable for measurement of light hydrocarbons (less than C15), which will be lost by evaporation below 70–85°C.

Gas chromatography–based methods are currently the preferred laboratory methods for TPH measurement because they detect a broad range of hydrocarbons, they provide both sensitivity and selectivity, and they can be used for TPH identification as well as quantification. The potential of GC for producing information on the product-specific hydrocarbon pattern has been long recognized by researchers in the field of petroleum hydro-carbon analysis. [66–68]

Currently, there are several standard methodologies based on GC for different types of samples (water, soil, wastes). The ISO has published the standard ISO 93772:2000 for the quality control of water and specifies a method for the determination of the hydrocarbon oil index within the C10–C40 range in waters by means of GC. The method is suitable for surface water, wastewater, and water from sewage treatment plants and allows the determination of the hydrocarbon oil index in concentrations above 0.1 mg/L. Due to systematic differences, which became evident between the results from the DIN ISO method and those from the IR-based method, the GC-based method was subsequently modified.[ 69 , 70 ] As a result, the modified version of DIN ISO 9377-2:2000, the OSPAR (Oslo–Paris commission) reference method,[ 58 ] was published in 2005 and taken into force as a reference method in the field of petroleum production in January 2007. The OSPAR reference method is applicable for the determination of dispersed oil content in produced water and other types of wastewater discharged from gas, condensate, and oil platforms. It also allows the determination of the dispersed mineral oil content in concentrations above 0.1 mg/L and includes the determination of certain hydrocarbons within the C7–C10 range, with the TEX (toluene, ethylbenzene, and o-/p-/m-xylene) compounds being reported separately.

Gas chromatography–based methods are based on the extraction of water samples with a nonpolar (hydrocarbon) solvent, the removal of polar substances by cleanup with Florisil, and capillary GC measurements using a nonpolar column and a flame ionization detector (FID), cumulating the total peak area of compounds eluted between n- decane (C10H22) and n-tetracontane (C40H82) for the DIN ISO 9377-2:2000 standard method and for the DIN ISO 16703:2005–12[ 59 ] standard method for soil samples. The OSPAR method was modified in order to include the determination of certain hydrocarbons with a boiling point between 98°C and 174°C (that is, from n-heptane to n-decane), with the TEX compounds being determined separately by integration and subtraction of their peak areas from the total integrated area. The GC-based methods usually cannot quantitatively detect compounds with a lower boiling point than n-heptane because these compounds are highly volatile and are interfered by the solvent peak. Furthermore, the EPA method 8240,[ 61 ] which is used to determine volatile organic compounds in a variety of waste matrices by GC/mass spectrometry (MS), exists. It can be used to quantitate most volatile organic compounds that have boiling points below 20°C and that are insoluble or slightly soluble in water. The estimated quantitation limit of the EPA 8240 method for an individual compound is approximately 5 μg/kg (wet weight) for soil/sediment samples, 0.5 mg/kg (wet weight) for wastes, and 5 μg/L for groundwater.

Gas chromatography–based methods are suitable for surface water, wastewater, and other types of wastewater discharged from gas, concentrate, and oil platforms and allow the determination of hydrocarbon oil concentration above 0.1 mg/L. To reach the required detection limit, the method according to DIN ISO 9377-2:2000 foresees preconcentration of the extracts by solvent evaporation, which bears the risk of losing the more volatile constituents of the sample. In contrast to this, the OSPAR method does not allow for any external apparatus for preconcentration, for which reason the GC must be equipped with an injection system that allows the injection of a volume of up to 100 μL of the extract. This is most easily realized with programmed-temperature vaporizer large-volume injectors. This technique can reduce the loss of volatile analytes, can increase sensitivity, and is a viable, fast, and automated alternative to an external preconcentration procedure.[ 71–73 ]

Petroleum products easily contain thousands of different compounds. Classical capillary GC cannot resolve such mixtures up to the level of individual compounds. A powerful analytical tool for separation of complex mixtures, such as petroleum hydrocarbons, is comprehensive two-dimensional GC (GC×GC or 2D-GC).[ 74–76 ] The use of 2D-GC with MS detection (GC×GC/MS) is expected to not only allow the separation of the various constituents of complex TPH samples but also to identify them based on MS detection (Figure 4b). It is known that a certain class of chemical compounds (a series of “homologues”) forms a very distinct, clearly identifiable pattern in the two-dimensional space of the GC×GC separation. The diesel total ion (TIC) GC×GC/MS chromatogram, illustrated in Figure 4a, is characterized by very typical group-type patterns: saturated hydrocarbons, which present low second-dimension retention times, are followed by monocyclic and dicyclic aromatics; tri-and tetracyclic aromatics are the most retained on the secondary polar column.[ 77 ] Moreover, partial overlapping between chemical groups occurs, the monocyclic aromatics are situated in a rather narrow band, and the tri-and tetracyclic aromatics are hardly visible in the two-dimensional chromatogram. The analytical potential of such a two-dimensional system is great.

(a) TIC GC×GC-qMS (quadruple-mass spectrometry) chromatogram of
                              diesel oil. SH, saturated hydrocarbons; MCAH, monocyclic aromatics;
                              DCAH, dicyclic aromatics; TriCAH, tricyclic aromatics; TetraCAH,
                              tetracyclic aromatics. (b) TIC LC-GC×GC- qMS chromatogram of the
                              monocyclic aromatic fraction of diesel oil. A) Indane, B)
                              1,2,3,4-Tetrahydro-2,7-dimethyl naphthalene, C) 1-Cyclohexyl 3-methyl
                              benzene, D) 1,2,3,4-Tetrahydro-2,5,8-trimethyl naphthalene.

Figure 4   (a) TIC GC×GC-qMS (quadruple-mass spectrometry) chromatogram of diesel oil. SH, saturated hydrocarbons; MCAH, monocyclic aromatics; DCAH, dicyclic aromatics; TriCAH, tricyclic aromatics; TetraCAH, tetracyclic aromatics. (b) TIC LC-GC×GC- qMS chromatogram of the monocyclic aromatic fraction of diesel oil. A) Indane, B) 1,2,3,4-Tetrahydro-2,7-dimethyl naphthalene, C) 1-Cyclohexyl 3-methyl benzene, D) 1,2,3,4-Tetrahydro-2,5,8-trimethyl naphthalene.

Source: Adapted from Sciarrone et al.[ 77 ]

Conclusion

Due to the importance and widespread use of petroleum hydrocarbons for energy production, for transport, and as a raw material in the chemical industries, there are many routes for their inadvertent or accidental release into the environment. Thus, they do represent one of the most important sources of large-scale environmental pollution. While petroleum hydrocarbons also are introduced into the oceans from natural seeps, these continuous emissions of comparatively low intensity represent a less significant environmental problem since the resident flora and fauna have adapted to this continuous input of hydrocarbons and effects are limited to local scale. Large oil spills in contrast exceed the self-cleaning capacity of the ecosystem, which cannot regenerate without human intervention to both physically and chemically immobilize, bind, and remove oil from the affected region. Although such techniques are available, large-scale oil spills always have caused severe damage to the environment, with the affected ecosystems recovering only slowly. Analytical methods are available for the qualitative and quantitative determination of the composition of oil samples and the assessment of pollution levels in various environmental compartments. Gas chromatographic techniques mostly have supplanted the former analytical standard method based on Freon extraction and mid-IR determination, but there is further research and development going on to develop either more powerful analytical methods—such as two-dimensional GC—or alternative detection methods, such as the ones based on mid-IR lasers as light sources.

Acknowledgments

This report was compiled within the frame of project 818084-16604 SCK/KUG of the Austrian Science Foundation (FFG), whose financial support is gratefully acknowledged.

References

1
Tissot, B.P. ; Welte, D.H. Petroleum Formation and Occurrence; Springer-Verlag: Berlin, 1984.
234
Available at http://www.eia.gov/petroleum/ (accessed September 2011 ).
5
Leffler, W.L. Petroleum Refining in Nontechnical Language, 4th Ed.; PennWell Corporation: Tulsa, OK, 2008.
6
Fahimm, M.A. ; Al-Sahhaff, T.A. ; Lababidii, H.M.S. ; Elkilanii A. Fundamentals of Petroleum Refining, 1st Ed.; Elsevier: Oxford, U.K., 2010.
7
Available at http://www.energyinst.org (accessed September 2011 ).
8
Nancarrow, D.J. ; Adams, A.L. ; Slade, N.J. ; Steeds, J.E. Land Contamination: Technical Guidance on Special Sites: Petroleum Refineries; R&D Technical Report P5–042/ TR/05; Environment Agency: Bristol, 2001.
9
Toxicological Profile for Total Petroleum Hydrocarbons (TPH); U.S. Department of Health and Human Services, Public Health Service Agency for Toxic Substances and Disease Registry: Atlanta, GA, 1999.
10
Leifer, I. ; Kamerling, M.J. ; Luyendyk, B.P. ; Douglas, S.W. Geologic control of natural marine hydrocarbon seep emissions, Coal Oil Point seep field, California. Geo-Mar. Lett. 2010, 30, 331–338.
11
Oil in the Sea III Inputs, Fates, and Effects; The National Academies Press: Washington, DC, 2003.
12
Available at http://www.toptenz.net/top-10-worst-oil-spills.php (accessed September 2011 ).
13
Weggen, K. ; Pusch, G. ; Rischmüller, H. Oil and gas. In Ullmann’s Encyclopedia of Industrial Chemistry; Wiley-VCH: Weinheim, 2000.
14
Sanin, P.I. Petroleum hydrocarbons. Russ. Chem. Rev. 1976, 45 (8), 684–700.
15
Available at http://api-ep.api.org/ (accessed September 2011 ).
16
Analysis of petroleum hydrocarbons in environmental media. In Total Petroleum Hydrocarbon Criteria Working Group Series; Weisman. W. , Ed.; Amherst Scientific Publishers: Amherst, MA, 1998; vol. 1.
17
Wang, Z. ; Fingas, M.F. Development of oil hydrocarbon fingerprinting and identification techniques. Mar. Pollut. Bull. 2003, 47, 423–452.
18
Wang, Z. ; Fingas, M. ;Pag.e, D.S. Oil spill identification. J. Chromatogr. A 1999, 843, 369–411.
19202122
Spills of Emulsified Fuels: Risks and Responses; The National Academy of Sciences: Washington, DC, 2001.
23
Petroleum Products in Drinking-Water; Background document for development of WHO Guidelines for Drinking-water Quality, WHO/SDE/WSH/05.08/123; World Health Organization: Geneva, 2005.
24
Fate of Spilled Oil In Marine Waters: Where Does It Go? What Does It Do? How Do Dispersants Affect It?; An Information Booklet for Decision Makers, Publication 4691; American Petroleum Institute: Virginia, 1999.
25
Afifi, S.M. Petroleum hydrocarbon contamination of groundwater in Suez: causes severe fire risk. Proceedings 24th AGU Hydrology Days, March 10–12, 2004, pp. 1–9. Colorado State University (2004).
26
Vaajasaar, K. ; Joutti, A. ; Schultz, E. ; Selonen, S. ; Westerholm, H. Comparisons of terrestrial and aquatic bioassays for oil-contaminated soil toxicity. J. Soils Sediments 2002,2 (4), 194–202.
27
Guidelines for Assessing and Managing Petroleum Hydrocarbon Contaminated Sites in New Zealand; Module 2—Hydrocarbon contamination fundamentals; Ministry for Environment: New Zealand, 1999.
28
Das, N. ; Chandran, P. Microbial degradation of petroleum hydrocarbon contaminants: An overview. Biotechnol. Res. Int. 2011, Article ID 941810, 13 pages.
29
Atlas, R.M. Microbial degradation of petroleum hydrocarbons: An environmental perspective. Microbiol. Rev. 1981, 45, 180–209.
30
Van Hamme, J.D. ; Singh, A. ; Ward, O.P. Recent advances in petroleum microbiology. Microbiol. Mol. Biol. Rev. 2003, 67 (4), 503–549.
31
Kaplan, I.R. ; Galperin, Y. ; Lu, S.T. ; Lee, R.P. Forensic environmental geochemistry: Differentiation of fuel-types, their sources and release time. Org. Geochem. 1997, 2, 289–317.
32
Šepieč, E. ; LeskovŠek, H. ; Trier, C. Aerobic bacterial degradation of selected polyaromatic compounds and n-alkanes found in petroleum. J. Chromatogr. A 1995, 697, 515–523.
33
Antić, M.P. ; Jovaneičević, B.S. ; Ilić, M. ; Vrvić, M.M. ; Schwarzbauer, J. Petroleum pollutant degradation by surface water microorganisms. Environ. Sci. Pollut. Res. 2006, 13 (5), 320–327.
34
Available at http://www.atsdr.cdc.gov/ (accessed September 2011 ).
35
Available at http://echa.europa.eu/home_en.asp (accessed September 2011 ).
36
Available at http://www.environment-agency.gov.uk/ (accessed September 2011 ).
37
The U.K. Approach for Evaluating Human Health Risks from Petroleum Hydrocarbons in Soil; Science report P5–080/TR3; Environment Agency: Bristol, U.K., 2005.
38
MA DEP 1994. Interim Final Petroleum Report Development of Health-Based Alternative to the Total Petroleum Hydrocarbon TPH Parameter; Massachusetts Department of Environmental Protection: Boston, Massachusetts, 1994.
39
MA DEP 2003. Updated Petroleum Hydrocarbon Fraction Toxicity Values for the VPH/EPH/APH; Massachusetts Department of Environmental Protection: Boston, Massachusetts, 2003.
40
Edwards, D.A. ; Andriot, M.D. ; Amoruso, M.A. ; Tummey, A.C. ; Tveit, A. ; Bevan, C.J. ; Hayes, L.A. ; Youngren, S.H. ; Nakles, D.V. Development of fraction specific reference doses (RfDs) and reference concentrations (RfCs) for total petroleum hydrocarbons. In Total Petroleum Hydrocarbon Criteria Working Group Series; Amherst Scientific Publishers: Amherst, Massachusetts, 1997; Vol. 4.
41
Potter, T.L. ; Simmons, K.E. Composition of petroleum mixtures. In Total Petroleum Hydrocarbon Criteria Working Group Series; Amherst Scientific Publishers: Amherst, Massachusetts, 1998; Vol. 2.
42
Vorhees, D.J. ; Weisman, W.H. ; Gustafson, J.B. Human health risk-based evaluation of petroleum release sites: implementing the working group approach. In Total Petroleum Hydrocarbon Criteria Working Group Series; Amherst Scientific Publishers: Amherst, Massachusetts, 1999; Vol. 5.
43
MA DEP 2003. Method for the Determination of Air-Phase Petroleum Hydrocarbons (APH); Massachusetts Department of Environmental Protection: Boston, Massachusetts, 2009.
44
MA DEP 2004. Method for the Determination of Volatile Petroleum Hydrocarbons (VPH); Massachusetts Department of Environmental Protection: Boston, Massachusetts, 2004.
45
MA DEP 2004. Method for the Determination of Extract-able Petroleum Hydrocarbons (EPH); Massachusetts Department of Environmental Protection: Boston, Massachusetts, 2004.
46
Available at http://www.epa.gov/ (accessed September 2011 ).
47
Verbruggen, E.M.J. Environmental Risk Limits for Mineral Oil (Total Petroleum Hydrocarbons); RIVM report 601501021; National Institute for Public Health and the Environment: Bilthoven, the Netherlands, 2004.
48
Available at http://www.iso.org/iso/home.html (accessed September 2011 ).
49
DIN ISO 9377-2:2000. Water Quality—Part 2, Method Using Solvent Extraction and Gas Chromatography; International Organization for Standardisation: Geneva, 2000.
50
Pollard, S.J.T. ; Duarte-Davidson, R. ; Askari, K. ; Stutt, E. Managing the risk from petroleum hydrocarbons at contaminated sites achievements and future research directions. Land Contam. Reclam. 2005, 13 (2), 115–122.
51
Saari, E. ; Perämäki, P. ; Jalonen, J. Measurement uncertainty in the determination of total petroleum hydrocarbons (TPH) in soil by GC-FID. Chemom. Intell. Lab. Syst. 2008, 92 (1), 3–12.
52
Becker, R. ; Buge, H.G. ; Bremser, W. ; Nehls, I. Mineral oil content in sediments and soils: Comparability, traceability and a certified reference material for quality assurance. Anal. Bioanal. Chem. 2006, 385 (3), 645–651.
53
Saari, E. ; Perämäki, P. ; Jalonen, J. Evaluating the impact of extraction and cleanup parameters on the yield of total petroleum hydrocarbons in soil. Anal. Bioanal. Chem. 2008, 392 (6), 1231–1240.
54
Saari, E. ; Perämäki, P. ; Jalonen, J. Effect of sample matrix on the determination of total petroleum hydrocarbons (TPH) in soil by gas chromatography–flame ionization detection. Microchem. J. 2007, 87 (2), 113–118.
55
Muijs, B. ; Jonker, M.T.O. Evaluation of clean-up agents for total petroleum hydrocarbon analysis in biota and sediments. J. Chromatogr. A 2009, 1216 (27), 5182–5189.
56
Koch, M. ; Liebich, A. ; Win, T. ; Nehls, I. Certified Reference Materials for the Determination of Mineral Oil Hydrocarbons in Water, Soil and Waste; Forschungsbericht 272; Bundesanstalt für Materialforschung und - prüfung (BAM): Berlin, 2005.
57
OSPAR. Reference Method of Analysis for Determination of the Dispersed Oil Content in Produced Water; OSPAR Commission, ref. no. 2005–15: Malahide, published in 2005, taken into force in 2007.
58
DIN ISO 16703:2005–12. Soil Quality—Determination of Content of Hydrocarbon in the Range C10 to C40 by Gas Chromatography; International Organization for Standardisation: Brussels, 2005.
59
DIN EN 14039: 2004. Characterization of Waste—Determination of Hydrocarbon Content in the Range of C10 to C40 by Gas Chromatography; German version; International Organization for Standardisation: Brussels, 2004.
60
EPA Method 8240. Gas Chromatography/Mass Spectrometry for Volatile Organics, Test Methods for Evaluating Solid Wastes; US Environmental Protection Agency: Washington, 1986, Vol. 1B.
61
ASTM Standard D7678111. Standard Test Method for Total Petroleum Hydrocarbons (TPH) in Water and Wastewater with Solvent Extraction using Mid-IR Laser Spectroscopy; ASTM International: West Conshohocken, PA, 2011; DOI: 10.1520/D7678–11.
62
EPA Method 418.1. Total Recoverable Petroleum Hydrocarbons by IR, Groundwater Analytical Technical Bulletin; Groundwater Analytical Inc.: Buzzards Bay, MA, 1991/1992.
63
EPA method 413.1. Standard Test Method for Oil and Grease Using Gravimetric Determination; issued in 1974, editorial revision in 1978 (withdrawn).
64
EPA method 1664. Revisiow A: w-Hexawe Extractable Material (HEM; Oil awd Grease) awd Silica Gel Treated n-Hexawe Extractable Material (SGT-HEM: Now-polar Material) by Extractiow awd Gravimetry; US Environmental Protection Agency: Washington, 1999.
65
ASTM D4281–95(2005)e1. Standard Test Method for Oil awd Grease (Fluorocarbow Extractable Substawces) by Gravimetric Determiwatiow; ASTM International: West Conshohocken, PA, 2005.
66
Blomberg, J. ; Schoenmakers, P.J. ; Brinkman, U.A.T. GC methods for oil analysis. J. Chromatogr. A 2002, 972 (2), 137–173.
67
Beens, J. ; Brinkman, U.A.T. The role of GC in compositional analyses in the petroleum industry. Trends Anal. Chem. 2000, 19 (4), 260–275.
68
Saari, E. ; Perämäki, P. ; Jalonen, J. Evaluating the impact of GC operating settings on GC–FID performance for total petroleum hydrocarbon (TPH) determination. Microchem. J. 2010, 94 (1), 73–78.
69
Thomey, N. ; Bratberg, D. ; Kalisz, C. A comparison of methods for measuring total petroleum hydrocarbons in soil. In Proceedings of the Petroleum Hydrocarbons and Organic Chemicals in Groundwater: Prevention, Detection and Restoration, November 15–17, 1989; National Water Well Association: Houston, Texas, 1989.
70
Xie, G. ; Barcelona, M.J. ; Fang, J. Quantification and interpretation of total petroleum hydrocarbons in sediment samples by a GC/MS method and comparison with EPA 418.1 and a rapid field method. Anal. Chem. 1999, 71 (9), 1899–1904.
71
Hoh, E. ; Mastovska, K. Large volume injection techniques in capillary gas chromatography. J. Chromatogr. A 2008, 1186, 2–15.
72
Miñones Vázqiez, M. ; Vázquez Blanco, M.E. ; Muniategui Lorenzo, S. ; Loópez Mahía, P. ; Fernández-Fernández, E. ; Prada Rodríguez, D. Application of programmed-temperature split/splitless injection to the trace analysis of aliphatic hydrocarbons by gas chromatography. J. Chromatogr. A 2001, 919, 363–371.
73
Dellavedova, P. ; Vitelli, M. ; Ferraro, V. ; Di Toro, M. ; Santoro, M. Applicatiow of enhawced large volume injectiow; an approach to the analysis of petroleum hydrocarbons iw water. Chromatographia 2006, 63, 73–76.
74
Van De Weghe, H. ; Vanermen, G. ; Gemoets, J. ; Lookman, R. ; Bertels, D. Application of comprehensive two-dimensional gas chromatography for the assessment of oil contaminated soils. J. Chromatogr. A 2006, 1137, 91–100.
75
von Mühlen, C. ; Alcaraz Zini, C. ; Bastos Caramão, E. ; Marriott, P. Applications of comprehensive two-dimensional gas chromatography to the characterization of petrochemical and related samples. J. Chromatogr. A 2006, 1105, 39–50.
76
van Deursen, M.M. ; Beens, J. ; Reijenga, J.C. ; Lipman, P.J.L. ; Camers, C.A.M.G. ; Blomberg, J. Group-type identification of oil samples using comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometer (GCxGC-TOF). J. High Resolut. Chromatogr. 2000, 23 (7–8), 507–510.
77
Sciarrone, D. ; Tranchida, P.Q. ; Costa, R. ; Donato, P. ; Ragonese, P. ; Dugo, P. ; Dugo, G. ; Mondello, L. Offline LC-GCxGC in combination with rapid-scanning quadrupole mass spectrometry. J. Sep. Sci. 2008, 31, 3329–3336.
Search for more...
Back to top

Use of cookies on this website

We are using cookies to provide statistics that help us give you the best experience of our site. You can find out more in our Privacy Policy. By continuing to use the site you are agreeing to our use of cookies.