CIVL6603 Module 1 Contaminant Fate and Transport Aspects of Benzene Discuss Use this journal to reflect on concepts you learned in Modules 1 and 2. Think h
CIVL6603 Module 1 Contaminant Fate and Transport Aspects of Benzene Discuss Use this journal to reflect on concepts you learned in Modules 1 and 2. Think how this material can be useful as you work on the Contaminant Characterization section of your term project. As you obtain information about your target contaminants physical, chemical, biological and toxicological properties (including possible adverse human health effects based on medical literature), try to relate properties these properties to contaminant behavior in the various environmental domains (air, water, soil).In an approximately 250 word entry, respond to the following:What properties may play a key role in assessing a contaminants mobility in the three environmental domains (air, water, soil)?What properties may be of relevance in assessing a contaminants reactivity (transformational tendency) with various reactants(e.g. oxygen, water, sunlight etc.) present in the three environmental domains (atmosphere, hydrosphere, pedosphere)? The presentations on Environmental Media could be particularly useful for this task.Depending on the contaminants physical/chemical nature, what may be the dominant mechanisms of intra- and inter-domain transport? The Notes on Dominant Transport and Transformation Mechanisms may be particularly useful here.Attached within is my group members dicussion post that provides much of the leg work. Discussion 1
CIVL 6603: Contaminant Fate and Transport in the Environment
Ryan Wagner
28 March 2019
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Table of Contents
1. Introduction to Benzene ………………………………………………………………………………………. 3
2. History………………………………………………………………………………………………………………. 3
3. Physical Properties ……………………………………………………………………………………………… 3
4. Benzene in the Environment …………………………………………………………………………………. 4
5.0 Transport …………………………………………………………………………………………………………. 6
6.0 Fate of Benzene in the Environment……………………………………………………………………… 7
7.0 Contaminant Chemistry ……………………………………………………………………………………… 8
8.0 Health Effects …………………………………………………………………………………………………… 8
9.0 Regulations………………………………………………………………………………………………………. 9
10 Conclusion ………………………………………………………………………………………………………. 10
11. References ……………………………………………………………………………………………………… 11
Tables:
Table 1: Physical Characteristics of Benzene
4
Table 2: States and territories with Reported Amounts of Benzene Released to Water, Land, and
Underground Injection
4
Figures:
Figure 1: Benzene chemical structure
Figure 2: Schematic of a potential source and receptors.
3
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3
1. Introduction to Benzene
Benzene, also known as benzol or mineral naptha, is a colorless, sweet smelling, highly toxic,
flammable, liquid hydrocarbon (1). Benzene may be produced naturally through natural
processes such as volcanic eruptions and forest fires; and is a primary component of crude oil,
gasoline and tobacco smoke. Benzene is used to manufacture a wide variety of petrochemical
products (e.g. styrofoam, resins, phenols, cyclohexanes, and lubricants) and in industrial solvents
in paints, vanishes, lacquer thinners. Additionally, benzene is used in the pharmaceutical
industry, as well as in the manufacturing of detergents, and pesticides (3).
2. History
Michael Faraday was the first scientist to discover benzene in 1825 (10). He extracted benzene
from cylinders of compressed illuminating gas, used to illuminate buildings in London, which
had been collected from the pyrolysis of whale oil. In 1833, Eilhard Mitscherlich a German
chemist produced what he called benzin via the distillation of benzoic acid (from gum benzoin)
and calcium oxide (lime). In 1845, benzene was found in coal tar by the English chemist Charles
Mansfield. Four years later, Mansfield began the first industrial-scale production of benzene,
based on the coal-tar method. Coal tar is made by destructively distilling coal and is still a
source of benzene today. Benzene was first synthesized in a laboratory in 1870 by Pierre
Berthelot who passed acetylene through a red-hot tube.
3. Physical Properties
Benzene is a liquid aromatic hydrocarbon, volatile organic compound (VOC), with the following
chemical structure: C6 H6
Figure 1: http://www.chem.ucla.edu/~harding/IGOC/B/benzene_ring.html (4)
4
Physical characteristics are listed in Table 1 below (2):
Table 1: Physical Characteristics of Benzene
Physical State
Molecular weight
Melting Point
Boiling Point
Water solubility
Vapor pressure
soil organic sorption coefficient Koc
log octanol/water partition coefficient (log
Kow)
Colorless liquid
184. 26 g/mol
5.5 0C
80 0C
4.00 x 102 mg/L
1.00 x 10 mmHg at 176oC
8.30 x 10 mL/g
2.12
Additionally, benzene evaporates into the air very quickly and dissolves in water.
4. Benzene in the Environment
Sources of benzene released to either water or soil include domestic manufacturing and process
facilities, treated and untreated industrial waste water, leaks from underground storage tanks,
leachate from landfills and other contaminated soils sources, regulated and unregulated
hazardous waste sites (under CERCLA and RCRA), and underground injection (1). Other
sources may include accidental spills or leaks from above ground transfers or poorly maintained
infrastructure. Data collected from the USCG Emergency Response Notification System
indicated that benzene was one of the most occurring spilled non-petroleum chemicals in U.S.
waters (3).
Table 2 below tabulates all the states and territories with reported amounts of benzene released
(in lbs/year) to water, land, and underground injection from regulated facilities that produce,
process or use benzene (1).
Table 2: States and territories with Reported Amounts of Benzene Released to Water,
Land, and Underground Injection
State
Water (lbs/year)
Land (lbs/year)
Underground
Injection (lbs/year)
AK
19
375
0
AL
290
280
0
AR
66
0
0
AZ
0
9
0
CA
129
1,292
228
CO
0
10
0
5
CT
DE
FL
GA
GU
HI
IA
ID
IL
IN
KS
KY
LA
MA
MD
ME
MI
MN
MO
MP
MS
MT
NC
ND
NE
NJ
NM
NV
NY
OH
OK
OR
PA
PR
RI
SC
SD
TN
TX
UT
VA
VI
WA
WI
WV
2
6,006
41
128
1
30
1
No data
102
805
164
799
1,688
55
8
23
8
2,724
0
0
25
5
0
0
No data
443
7
0
56
67
14
8
419
7
4
6
1
63
621
750
787
0
14
0
284
0
26
0
9
0
12
0
0
2,152
4,654
259
766
1,075
26
184
0
127
131
0
0
14
15
5
1
6
150
0
0
10
730
278
41
345
0
0
250
0
280
8,326
809
26
9
95
251
393
0
0
0
0
0
0
0
0
0
14,001
231
0
122,723
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
5
0
0
0
0
0
0
0
0
298,595
0
0
0
0
0
0
6
WY
0
1
0
(Data is from 2004)
Estimated releases of benzene to surface water is 16,051 pounds (~7tons) from 986 domestic
manufacturing and processing facilities in 2004, accounted for about 0.2 % of the estimated total
environmental releases from facilities required to report to the TRI (1). Benzene has been
detected in groundwater samples collected at 832 of the 1,684 current and former NPL sites and
in surface water samples collected at 208 of the 1,684 sites.
Estimated release of benzene to soil is approximately 24,033 pounds (~11 metric tons) from 968
domestic manufacturing and processing facilities, accounting for about 0.3 % of the estimated
total environmental releases from facilities required to report to the TRI (1). An additional
435,000 pounds (~197 metric tons), consisting of about 6% of the total environmental emissions,
were released via underground injection.
It is noted that the state with the highest release to water was Louisiana with 1,688 lbs/year,
release to land was Texas with 8,326 lbs/year, and release via underground injection was also
Texas with 298,595 lbs/year.
5.0 Transport
Benzene may be directly released into subsurface soils and/or groundwater, or may occur
through leaching from surface spills, releases and/or discharges, or from landfills or other
contaminated sources. The influential parameters that determine the leachability include the soil
type (sandy vs clayey soils or fractured vs non-fractured rock), amount of rainfall, depth to
groundwater and seasonal fluctuations of the groundwater table, and extent of degradation (1).
Benzene is highly volatile, therefore once the contaminant is released to either a surface water
source or a near sub-surface soil source a high volatilization rate back to the atmosphere will
occur.
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6.0 Fate of Benzene in the Environment
As indicated in Table 1, the soil organic carbon sorption coefficient (Koc) is 83 mL/g, this
indicates that benzene is highly mobile in soil and highly capable of leaching into groundwater.
Once benzene has reached the groundwater table, and depending on the permeability of the soil
matrix, benzene has the capability of transporting many meters from the initial contaminated
source.
Therefore, the fate and potential impact in the environment can be averse to many sources either
through impacts directly into groundwater or through expression of groundwater into surface
water sources.
In determining the risk of either of these contaminant transport methods, it must be taken into
consideration the potential affects upon environmental sensitive areas and potential extraction or
beneficial uses (i.e. drinking water, recreational use, protection of ecosystems, agricultural uses
(stock watering and irrigation), and industrial uses). Figure 2 below, provides a schematic of a
potential source and receptors.
Figure 2: Schematic of a potential source and receptors. (source: Wagner, Ryan 2019)
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7.0 Contaminant Chemistry
Benzene (C6H6) is an aromatic compound and the parent to which numerous other aromatic
compounds are related. Aromatic compounds consist of a large class of unsaturated chemical
compounds characterized by one or more planar rings of atoms joined by covalent bonds of two
different kinds. The unique stability of these compounds is referred to as aromaticity.
In benzene, the six carbon molecules are joined in a ring, having a planar geometry of a regular
hexagon in which all of the C C bond distances are equal. The six ? electrons circulate in a
region above and below the plane of the ring, each electron being shared by all six carbons,
which maximizes the force of attraction between the nuclei (positive) and the electrons
(negative).
8.0 Health Effects
Benzene exposure may occur through a number of pathways (5). The first being ingestion, this
may occur through drinking water from a groundwater source contaminated with the benzene.
The second pathway may occur through inhalation, this may occur through breathing air
contaminated with benzene vapor. And Thirdly, through dermal contact, this may occur through
skin contact if you handle gasoline or other products that may contain benzene (including
contaminated soils or sediments). The US EPA classifies benzene as carcinogenic to humans.
Long term exposure to high levels of benzene can cause leukemia and cancers of the bloodforming organs (bone marrow, lymph nodes, and spleen). Health impacts are dependent on how
much, how long, how often, and the way one is exposed. Young children, the elderly, and
people with on-going health problems are more at risk for negative health impacts from benzene
exposure. Breathing high levels of benzene may result in a rapid heart rate, dizziness, tremors,
headaches, and drowsiness. Breathing high levels of benzene for long periods of time may cause
serious problems with the production of blood. Benzene causes harmful effects on the bone
marrow and can cause a decrease in red blood cells, leading to anemia. Additionally, it can also
cause excessive bleeding and affect the immune system. Drinking high concentrations of
benzene can cause an irritated stomach, vomiting, rapid heart rate, dizziness, convulsions, and
sleepiness.
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9.0 Regulations
Many chemicals are listed as toxic substances for specific regulatory purposes (2). Benzene is
designated a priority pollutant under the Clean Water Act. Listed as a hazardous substance,
designated under the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA). Designated as a listed chemical under Appendix IX of 40 CFR Part 264 (7). The
regulation requires that benzene is monitored in groundwater monitoring wells surrounding
Resource Conservation and Recovery Act (RCRA) land based hazardous waste disposal units.
The monitoring must take place when groundwater contamination is first detected, and then
again once per year. Additionally, benzene is designated a hazardous air pollutant under the
1991 Clean Air Act Amendment.
In 1974, Congress passed the Safe Drinking Water Act (8). This law required the US EPA to
determine the level of contaminants in drinking water at which no adverse health effects are
likely to occur. These goals non-enforceable health goals, based solely on possible health risks
and exposure over a lifetime with an adequate margin of safety, are called maximum
contaminant level goals (MCLG).
MCLG for benzene is zero (8). The EPA set this level of protection based on the best available
science to prevent potential health problems. Additionally, the EPA has set an enforceable
regulation for benzene, referred to as the maximum contamination level (MCL), at 0.005 mg/L
or 5 ppb. MCLs are set as close to the health goals as possible, considering cost, benefits and the
ability of public water systems to detect and remove contaminants using suitable treatment
technologies.
The Act also requires the EPA to conduct a Six Year Review of the Drinking Water Standards.
The reviews have indicated that EPA still determines that the level of 0.005 mg/L or 5 ppb are
still protective to human health (8).
Additionally, individual states may set more stringent drinking water MCLGs and MCLs for
benzene than EPA.
In comparison to the EPA drinking water guideline, the World Health Organization (WHO) has
determined that for the protection of human health a safe drinking water level of 0.001 mg/L is
suitable (9).
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10 Conclusion
The fate and potential impact of Benzene in the environment can be averse to many sources
either through impacts directly into groundwater or through expression of groundwater into
surface water sources.
In determining the risk of either of these contaminant transport methods, it must be taken into
consideration the potential affects upon environmental sensitive areas and potential extraction or
beneficial uses (i.e. drinking water, recreational use, protection of ecosystems, agricultural uses
(stock watering and irrigation), and industrial uses).
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11. References
1. ATSDR. (2018) Potential for Human Exposure. Retrieved from
https://www.atsdr.cdc.gov/toxprofiles/tp3-c6.pdf.
2. LaGrega, M.D., Buckinghams, P.L. & Evans, J.C. (2010). Hazardous waste management.
Long Grove, IL: Waveland Press.
3. Roy J. Irwin, National Park Service (1997). Environmental Contaminants Encyclopedia.
Retrieved from https://nature.nps.gov/water/ecencyclopedia/assets/contaminantpdfs/benzene.pdf.
4. UCLA. (2018). http://www.chem.ucla.edu/~harding/IGOC/B/benzene_ring.html.
5. Carey, Francis A. (2018). Aromatic Compound. Retrieved from
https://www.britannica.com/science/aromatic-compound.
6. IDEM. (2018). Benzene Factsheet. Retrieved from
https://www.in.gov/idem/files/factsheet_benzene.pdf
7. Federal Register (1987), Vol 52, No 131, Environmental Protection Agency, 40 CFR
Parts 264 and 270. Retrieved from https://www.epa.gov/sites/production/files/201603/documents/52fr25942.pdf.
8. US EPA. (2018). EPAs drinking water regulations for benzene. Retrieved from
https://safewater.zendesk.com/hc/en-us/articles/211403568-4-What-are-EPA-s-drinkingwater-regulations-for-benzene9. WHO. (2018). Benzene in Drinking-water, Background document for development of
WHO Guidelines for Drinking-water Quality. Retrieved from
https://www.who.int/water_sanitation_health/dwq/benzene.pdf
10. Thompson, Mike & Style, Charlie. (2011). BENZENE. Retrieved from
http://www.chm.bris.ac.uk/motm/benzene/benzeneh.htm
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