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Ethylbenzene

What is Ethylbenzene?

Ethylbenzene is a naturally occurring and industrially produced aromatic hydrocarbon commonly found in crude oil, gasoline, and other petroleum products. It is also used primarily in the manufacture of styrene, which is then used to produce polystyrene plastics, resins, and synthetic rubber.

Because of its widespread occurrence in petroleum products, ethylbenzene is frequently detected in soil and groundwater at petroleum release sites, refineries, fuel terminals, pipelines, bulk storage facilities, and other locations where fuels or petroleum-related materials have been handled.

Ethylbenzene is one of the four primary compounds that make up the BTEX group of petroleum hydrocarbons: benzene, toluene, ethylbenzene, and xylenes.

How Tersus Can Help with Ethylbenzene 

Tersus Environmental provides several technologies that can be used to address ethylbenzene in soil and groundwater. Treatment selection depends on site geochemistry, contaminant distribution, source conditions, and remediation objectives.

Sustainable Treatment of Petroleum Hydrocarbons

Commonly utilized products include:

Chemical Properties

Ethylbenzene is lighter than water and is classified as a Light Non-Aqueous Phase Liquid (LNAPL). When released as part of gasoline or other petroleum products, ethylbenzene may remain within free-phase product, dissolve into groundwater, sorb to soil, or partition into soil gas.

Property Value
Chemical Name Ethylbenzene
Common Name Ethylbenzene
Chemical Formula C₈H₁₀
CAS Number 100-41-4
Molecular Weight 106.16 g/mol
Density Approximately 0.87 g/cm³
Solubility in Water Approximately 150 mg/L at 20°C

Common Sources of Ethylbenzene

Ethylbenzene may be present due to:

  • Petroleum releases from underground storage tanks (USTs)
  • Gasoline spills and leaks
  • Petroleum pipelines
  • Fuel terminals and bulk storage facilities
  • Refineries and petrochemical facilities
  • Styrene and plastics manufacturing
  • Solvent and chemical manufacturing operations
  • Former manufactured gas plant (MGP) sites

Ethylbenzene is commonly found alongside other petroleum hydrocarbons, particularly benzene, toluene, and xylenes (BTEX compounds).

Environmental Concerns

Ethylbenzene is a mobile and volatile petroleum hydrocarbon that can migrate from contaminated soil into groundwater and soil gas.

Unlike chlorinated solvents, ethylbenzene does not undergo reductive dechlorination. Instead, biodegradation may occur through aerobic or anaerobic processes, with aerobic biodegradation generally occurring more readily when sufficient dissolved oxygen is present.

Under anaerobic conditions, biodegradation may also occur through nitrate-reducing, sulfate-reducing, iron-reducing, or methanogenic pathways, although the rate and extent of degradation depend on site-specific geochemical conditions.

Because ethylbenzene is less soluble in water than benzene and toluene, it may be somewhat less mobile in groundwater. However, significant dissolved plumes may still develop at petroleum release sites, especially where long-term source material remains in place.

Behavior in Soil and Groundwater

Ethylbenzene contamination may exist as:

  • Free-phase petroleum product (LNAPL)
  • Dissolved contamination in groundwater
  • Sorbed contamination attached to soil particles
  • Vapor-phase contamination within the vadose zone

Ethylbenzene can dissolve into groundwater and migrate away from a release area, although it generally exhibits lower aqueous solubility than benzene and toluene.

Because ethylbenzene is volatile, it also readily partitions from contaminated soil and groundwater into soil gas and may contribute to vapor intrusion concerns where contamination is located beneath or near occupied buildings.

Ethylbenzene also tends to sorb somewhat more strongly to soil organic matter than benzene, which may reduce mobility somewhat but can also contribute to persistent residual mass in source areas.

Human Health Effects

Exposure to elevated concentrations of ethylbenzene may affect the:

  • Central nervous system
  • Liver
  • Kidneys
  • Respiratory system
  • Eyes and skin

Short-term exposure to high concentrations may cause dizziness, headache, fatigue, irritation, or impaired coordination.

Long-term or repeated exposure to elevated concentrations may affect the liver and kidneys.

Because of these potential health effects, ethylbenzene concentrations in groundwater, drinking water, soil gas, and indoor air may be evaluated as part of environmental investigations and risk assessments.

Regulatory Standards

Regulatory criteria vary by jurisdiction; however, the United States Environmental Protection Agency has established a Maximum Contaminant Level (MCL) for ethylbenzene in drinking water of 0.7 mg/L (700 µg/L).

Many states have additional groundwater, soil, soil gas, vapor intrusion, and risk-based screening criteria for ethylbenzene.

Frequently Asked Questions

What is ethylbenzene commonly used for?
Ethylbenzene is used primarily in the manufacture of styrene, which is then used to produce polystyrene plastics, resins, and synthetic rubber. It is also present in crude oil, gasoline, and other petroleum products and may be used in some solvent and chemical manufacturing applications.

Is ethylbenzene an LNAPL?
Pure ethylbenzene has a density less than water and is classified as a Light Non-Aqueous Phase Liquid (LNAPL). At petroleum-release sites, however, it is more commonly encountered as a dissolved constituent of gasoline or other petroleum products rather than as a separate pure-phase liquid.

Can ethylbenzene biodegrade naturally?
Yes. Ethylbenzene can biodegrade under both aerobic and anaerobic conditions. Aerobic biodegradation is often effective where sufficient dissolved oxygen is present, while anaerobic degradation may occur under nitrate-reducing, iron-reducing, sulfate-reducing, or methanogenic conditions.

How does ethylbenzene behave compared with benzene and toluene?
Ethylbenzene is less soluble in water than benzene and toluene and generally sorbs more strongly to soil organic matter. As a result, it may be somewhat less mobile in groundwater, although dissolved plumes can still develop where petroleum source material remains present.

How is ethylbenzene removed from groundwater?
Tersus supports several approaches for ethylbenzene remediation, including enhanced aerobic bioremediation, sulfate-enhanced anaerobic biodegradation, source-area treatment, and in-situ chemical oxidation. Treatment selection depends on contaminant concentrations, groundwater geochemistry, source conditions, geology, and remediation objectives.

Can ethylbenzene contribute to vapor intrusion?
Yes. Ethylbenzene is volatile and can partition from contaminated soil and groundwater into soil gas. Vapor intrusion may therefore be a concern where impacted soil or groundwater is located beneath or near occupied buildings.

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