Total Petroleum Hydrocarbons

Total petroleum hydrocarbons (TPHs) are one of the common contaminants in the environment. They include a broad family of several hundred hydrocarbon compounds that originally come from crude oil which is used to make petroleum products. The widespread use of crude oil and other petroleum products for transportation, heating, and industry leads to the release of these petroleum products into the environment through long-term leakage, accidental spills, or operational failures. Since there are so many different chemicals in crude oil and other petroleum products, it is not practical to measure each one separately. However, it is useful to measure the amount of TPHs at a contaminated site. The TPHs include both volatile and extractable petroleum hydrocarbons (VPHs and EPHs) encompassing the gasoline range organics (>C₆–C₁₀), diesel range organics (>C₁₁–C₂₈), and oil range organics (C₂₉–C₃₅). Gasoline, kerosene, diesel fuels, jet fuels, Stoddard solvent, mineral-based motor oils, fuel oils No. 5 and 6, hexane, benzene, toluene, xylenes, and polycyclic aromatic hydrocarbons are the important chemicals that constitute TPHs. These chemicals have carbon ranges between ≥C₅ and ≤C₃₅. Detailed information about each of these chemicals included in TPHs is presented in this chapter.

Analysis of total petroleum hydrocarbons (TPHs) from impacted media involves the collection and preservation of samples followed by extraction, concentration, and clean-up of the sample extract as well as detection and quantification of the petroleum hydrocarbons (PHs). Extraction involves the use of methods such as continuous liquid-liquid extraction, purge and trap extraction, headspace analysis, separatory funnel extraction, solid-phase extraction, accelerated solvent extraction, mechanical shaking, microextraction, Soxhlet extraction, ultrasonic extraction, or supercritical fluid extraction, while the concentration of the extract is executed using the trapping method, Snyder column, Kuderna-Danish concentrator, or nitrogen evaporator. Extract clean-up before analysis is done directly using solid-phase cartridges or indirectly using alumina clean-up, silica gel clean-up, gel permeation clean-up, acid-base partition, and desulfurization technique. The measurement of TPHs in impacted media is most frequently done using gas chromatography (GC) coupled with a flame ionization detector, photoionization detector, or mass spectrometric detection. Other methods of final TPHs determination include infrared spectroscopy, gravimetry, ultraviolet fluorescence spectroscopy, immunoassay, and high-performance liquid chromatography. More importantly, the profile of unresolved complex hydrocarbon mixtures in a TPH-polluted sample is amply characterized and resolved using two-dimensional GC. Of all the analytical methods, ultraviolet fluorescence spectroscopy, gravimetry, and GC are more frequently used to determine TPHs levels in the environment.

An oil spill is the release of liquid petroleum hydrocarbons (PHs) into the environment, especially the terrestrial (land) and aquatic ecosystems, due to human activities, and is a form of pollution. When the oil is spilled, it normally spreads out and moves in and on the surfaces of spilled sites while undergoing several physico-chemical changes. These processes are collectively termed as “weathering” or “oil weathering processes” (OWP) and determine the “fate of the oil.” The speed and relative importance of the processes depend on several factors such as (i) the quantity of spill, (ii) the oil’s initial physical (surface tension, specific gravity, and viscosity) and chemical characteristics, (iii) existing environmental conditions, and (iv) whether the oil remains at or runs off from the spilled site. In land-oil spill, there is a high-level possibility of leaching of spilled oil into groundwater or entering waterways (i.e., rivers and streams) as runoff and to return the soil to productive use as quickly as possible. Various hydrocarbon fractions of spilled oil in marine environments are selectively subjected to evaporation (very volatile fractions), oxidation, and dissolution into the water table (dissolved oxygen combines with oil to produce water-soluble compounds), spreading, accumulation as persistent residues, and biodegradation by microorganisms. In certain cases, the contaminated area can be flooded, wherein oil floats or moves to water surface since some of the fractions of crude oil are lighter (i.e., propane and benzene) than water. The present chapter emphasizes the fate of total petroleum hydrocarbons (TPHs) in various environments immediately after the spill.

There is a fundamental need to understand and possibly quantify the bioavailable fraction of total petroleum hydrocarbons (TPHs) present in the environment. Bioavailability can be defined as the amount of a pollutant that can be readily taken up by microorganisms for biodegradation. The bioavailability of TPHs governs the rate of biodegradation or bioremediation. There are several constraints including low aqueous solubility, sorption, and micropore exclusion that limit the bioavailability of TPHs to microorganisms. Surfactants enhance TPHs bioavailability and thereby increase the rate of biodegradation. To quantify the bioavailable fractions, many techniques have been employed ranging from solvent-based extractions to the use of biota. Chemical techniques used to determine TPHs bioavailability include mild organic solvent extraction, supercritical fluid extraction with pure CO₂, persulfate oxidation, cyclodextrin extraction, solid-phase extraction using Tenax, and surfactant extraction. The biological assays developed for assessing the bioavailability of TPHs in the environment include the respirometry, bioluminescence assay, quantitation of mRNA, earthworm toxicity test, human dermal uptake test, animal oral uptake test, microtox toxicity test, springtail toxicity test, Ames assay, seed germination/root elongation test, algal growth inhibition test, and Daphnia immobilization test.

Contamination of soil and aquatic ecosystems by petroleum hydrocarbons (PHs) is a serious global issue. The total petroleum hydrocarbons (TPHs) that originate from the distillates of crude oil in the form of diesel, gasoline, lubricating oil, and other typical PHs received much attention globally as contaminants since they are highly toxic, mutagenic, and carcinogenic in nature. Toxicity of PHs increases with increasing molecular weight. Low-molecular-weight cyclic alkanes are more toxic to aquatic organisms than aliphatic and aromatic hydrocarbons of the same molecular weight. In a terrestrial environment, aromatic hydrocarbons are more toxic than aliphatic compounds. Even lower aromatic compounds other than polyaromatic hydrocarbons (PAHs) are toxic. Importantly, the toxicity of PHs in an organism is directly proportional to its bioavailability. Hydrophilic PHs are more bioavailable than the hydrophobic and/or bound PHs. The bioavailable pollutant is highly accessible and adsorbed/absorbed by an organism, causing sublethal or lethal effects by interacting with specific sites/receptors in the organisms. During toxicity development, PHs usually disrupt the cell membrane, which results in the fluctuations in membrane fluidity, integrity, and functioning in the organisms. In aquatic system, non-bioavailable and/or hydrophobic PHs become bioavailable to several benthic organisms (e.g., invertebrates, fish, deposited fish eggs, etc.) as they get adsorbed onto particulates and sediments. Certain aquatic invertebrates (e.g., mussels, oysters, crabs, cockles, etc.) that ingest suspended oil droplets/oil-bound particulates are highly sensitive to PHs. Human beings suffer potential health disorders upon exposure to petroleum compounds via inhalation, ingestion, and dermal contact. An impact in a population that causes no mortality is called sublethal effect, and these effects usually include the development of lesions, developmental defects, changes in molecular functions, and behavioral changes in feeding and breeding. Lethal effects occur in the aquatic environment due to short-term exposure to oil spills, where they disrupt the central nervous system through partitioning into cell membranes and nerve tissues. Fatality caused by PHs is broadly termed as narcosis. In all, the accumulation and persistence of PHs in the environment can bring about harmful effects in both terrestrial and aquatic ecosystems. The present chapter describes several ecological impacts of TPHs on microorganisms, plants, and animals (invertebrates and vertebrates) of both terrestrial and aquatic systems.

Exposure to oil and oil products either directly or indirectly causes severe health issues in humans, and the effects are principally dependent on the nature of contact with the oil spill. Direct exposures include breathing contaminated air (volatile fractions which are emitted as gases) and direct contact with the skin (while walking in contaminated areas). Indirect exposures to oil are due to bathing in contaminated water and eating contaminated food. Human health is badly affected by the contamination of total petroleum hydrocarbons (TPHs), and the effects depend largely on the type of site (land, river, and ocean) of oil spilled. Other contributing factors that affect the human health upon oil exposure include the kind and extent of exposure. Cleaning workers at the oil spill site are at greater risk. Health disorders include skin and eye irritation, breathing and neurologic problems, and stress. TPHs have a strong impact on mental health and induce physical/physiological effects, and they are potentially toxic to genetic, immune, and endocrine systems. Even though the long-term effects of TPHs in humans are not fully understood yet, certain symptoms may persist for some years of postexposure period. Thus, health protection in TPHs-exposed individuals is a matter of serious concern. Health risk assessments have the greatest impact in enabling the detection of any potential exposure-related harmful effects either at the time of exposure or for prolonged periods following the exposure. In this direction, the present chapter provides comprehensive insights into understanding the effects of TPHs on human health.

For more than a decade, the primary focus of environmental experts has been to adopt risk-based management approaches to clean-up the total petroleum hydrocarbons (TPHs)-polluted sites that pose potentially destructive ecological consequences. This attention led to the development of several physico-chemical, thermal, and biological technologies that are widely implementable. Established remedial options available for treating TPHs-contaminated sites are dig and dump, soil washing, soil vapor extraction, incineration, thermal desorption, natural attenuation, landfarming, slurry bioreactors, composting, bioaugmentation, biostimulation, biopiling, bioventing, and phytoremediation. Integrating physico-chemical, thermal, and/or biological technologies is also practiced for better clean-up of TPHs-contaminated environments. Bioelectrochemical system, nanoremediation, electrokinetic remediation, genetic engineering, and ultrasound technology-assisted remediation are still at the development stage. Though several treatment methods to remediate TPHs-polluted sites currently exist, a comprehensive overview of all the available remediation technologies to date is not available and is necessary so that the right technology for field-level success is chosen. Hence, this chapter presents a brief overview of all the traditional and newly emerging technologies for TPHs remediation.

The contamination of land with total petroleum hydrocarbons (TPHs) is a serious environmental and development issue in many nations. If managed well, it can be an opportunity for urban renewal and development. However, if not managed or remediated, it can pose deleterious effects on public health and the environment. Fortunately, industrialized nations such as the USA, the UK, Canada, New Zealand, the Netherlands, and Australia have developed comprehensive and proven regulatory frameworks for TPHs site management. However, developing countries lack regulations for TPHs. This chapter presents an overview of the TPHs contamination management in both developed and developing countries and identifies the gaps in existing policy and regulations. Finally, we provide a series of recommendations that could enhance TPHs-contaminated land legislation, especially in the developing countries.

Contamination can be defined as the abnormal presence of pollutants that adversely or negatively impacts an object. “Environmental remediation” is a very broad term used to define any effort employed to solve the problems caused by contaminants that affect either soils or waters in or on the ground surface. Protection of human health and the environment is the important objective of any remediation approach concerning soil, water, or sediment. The chief objective of the remediation, however, is to remove or reduce concentrations of the contaminants to the “safe” levels for the environment and human health. Though it seems simple with the correct advice and guidance, selection of the best method(s) to remediate polluted site is challenging. Thus, remediation of the areas contaminated with pollutants represents a growing challenge, and cleaning of such areas is of international concern. In this direction, the present chapter has been designed to present the details of several case studies from different countries which dealt with full-scale applications of different technologies to remediate the sites contaminated with total petroleum hydrocarbons (TPHs). This information could be very useful in providing more insights into various issues such as practical difficulties in the application of the remedial technologies at larger scale as to how clean-up goals are designed, what are the characteristics of contaminated sites (e.g., soil, water, etc.), what are the treatment options, how the levels of contaminants will be changed before and after the treatment in a stipulated time frame, what about the cost factors and economic feasibilities, etc.