ENE 802
Physicochemical Processes in Environmental Systems
Fall Semester 2004
Dr. Susan J. Masten
Homework 1
Due: Wednesday, September 22, 2004. Completed assignments are to be turned in
by 4 pm to either myself or to Lori Hasse in the Research Complex. Please do not
turn assignments into the CEE office in the Engineering Building.
1. A 55-gallon drum is half-filled with water and half-filled with air. A technician
disposes of 1500 mL of toluene in the drum and then seals it. What is the
equilibrium concentration of toluene in the water and what is the partial pressure of
toluene in the gas phase.
2. In a factory in which metal parts are degreased with organic solvents, someone
drops a full glass bottle containing a mixture of 10 liters of tetrachloroethylene
(PCE) and 7 liters of 1,2-cis-dichlorethylene (DCE) in a closed room at 20 oC. The
room has a total volume of 50 m3. The bottle breaks and the solvent mixture is
spilled on the floor. Soon several employees report that they can smell solvent
vapors in the air. Answer the following questions by assuming that PCE and DCE
form an ideal mixture in the liquid phase.
a. What was the composition (in mole fractions) of the liquid mixture in the
bottle, and what is it at equilibrium in the remaining liquid on the floor of the
room?
b. What are the maximum (=equilibrium) concentrations of PCE and DCE in
the air of the room? How much of each solvent component has evaporated?
Has the OSHA limits for PCE and DCE been exceeded?
c. If the same accident happened in your sauna (volume = 15 m3, T=80 oC), to
what maximum PCE and DCE concentrations would you and your friends
been exposed?
3.
The FBI has suggested that various pesticides could be used as a “mass
poisoning agent”. You work for United Water Utilities in NJ and are in charge of
protecting the Oradell Reservoir (in New Milford, NJ). The Oradell Reservoir has
a storage capacity of 250 million gallons. You are to perform a Level 1 fugacity
model calculations for the chemical Acti-dione (3-[2-(3,5-Dimethyl-2oxocyclohexyl)2-hydroxyethyl-] glutarimide) to determine the fate of this chemical
should someone decide to poison the water by dumping Acti-dione into the
reservoir, at an amount that would result in human toxicity. You may assume that
the temperature of the environment is 20 oC. In addition, the Office of Homeland
Security has asked you to determine the feasibility of someone actually poisoning
the water in this way. As such, you must determine the mass of commercially
available product required to produce the amount of Acti-dione needed. Be sure
to record all assumptions made in performing these calculations.
Media
Volume, m3
Air
2 x 1011
Water
9.5 x 105
Biota
4.2
Suspended
solids
45
Sediment
2.9 x 103
Organic carbon contents: Soil = 2%
5%
Sediment = 5%
Suspended solids =
Media densities (kg/m3) : Air = 1.19; Biota = 1050; Suspended solids =
1500; Water = 1000; Sediment = 1500
Compare your result with the Level 1 fugacity model available from the Canadian
Environmental Modelling Center.
4. The fugacity of 2,4,4'-trichlorobiphenyl (PCB) in a lake water at 25 oC is 10-6 Pa
(Pascals). The air water partition coefficient for this PCB is KAW = 0.006, and the
log octanol water partition coefficient is Log KOW = 5.74, both at 25 oC. The weight
fraction concentration of organic carbon in the lake sediment is 0.075 and the dry
bulk density of sediment is 1.65 kg/L. The upper 1 cm of lake sediment is assumed
to be in equilibrium with the lake water. In answering the following questions,
briefly discuss important assumptions that you make.
a. What is the meaning of the following statement: The fugacity of this PCB in lake
water equals 10-6 Pa? How might you measure the fugacity?
b. If the PCB concentration in the lake water is at equilibrium with the concentration
in air, what is the partial pressure of this PCB in the air phase?
c. Calculate the Henry’s Law constant (Pa m3/mol) for this PCB.
d. Calculate the expected sediment-water partition coefficient (KSW) for this PCB.
e. Calculate the fugacity capacities of the air, water, and sediment (upper 1 cm)
phases for this PCB.
f. Calculate the expected concentrations (mol/m3) of this PCB in the water, air, and
sediment phases.
g. If fish in this lake are exposed to the PCB by direct uptake from the lake water
(bioconcentration), calculate the expected concentration of the PCB in the fish.
5. A WI DNR employee has just returned from the field where he/she has taken a
sample of groundwater next to a leaky tetrahydrofuran solvent storage tank. The
bottle is transparent and it is readily apparent that there are three separate phases
– air, water, and tetrahydrofuran. A detailed GC-MS analysis of extracts from the
water and tetrahydrofuran phases also indicates that, in addition to air, water, and
dichloromethane, the following compounds are also present: acetone, benzene,
toluene, and hexane. As environmental chemists we are interested in knowing how
the organic solutes are partitioned between air, water and dichloromethane. We
also know that it will take some time for the components in the flask to come to
equilibrium after sampling.
a. What is the minimum number of intensive variables that must be determined at
equilibrium in order to completely define the system? (Hint: the following intensive
properties are those that are needed – Temperature, Pressure, concentrations of
air (O2, N2, CO2, Ar, H2O) + all the organic compounds in the air phase,
concentrations of water, air + all organic compounds in the water phase, and the
concentrations of air, water and all the other organic compounds in the
dichloromethane phase.
b. Which ones would you specify?
6. Partial pressures of acetone and chloroform in the vapor in equilibrium with liquid
solution at 35.2oC are given in Table 1, below. (A) Plot the resulting vapor-liquid
diagram for this system! (B) Explain why there is a negative or positive deviation
from Raoult’s Law in this system (try to explain this in terms of what you have
learned about intermolecular forces).
7. What is the fugacity of pure 1,4-dichlorobenzene at 25 oC? What is the fugacity of 2
mg 1,4-dichlorobenzene dissolved in one liter of water at 25 oC? The benzene = 1.25
x 104 in water.
Table 1. Partial Pressures of Acetone and Chloroform in the Vapor in Equilibrium with Liquid
Solutions at 35.2oC.
Mole Fraction
Chloroform in
Liquid Solution
Chloroform
Acetone
Total
In mmHg
Mole Fraction
Pobs
PCElc
Pobs
PCElc
Pobs
PCElc
0
0
0
344
344
344
344
0.2
34
59
270
275
304
334
0.4
82
117
183
207
265
324
0.6
148
177
102
137
250
314
0.8
225
234
42
69
267
303
1.0
293
293
0
0
293
293
Pressures expressed in mm Hg; Pobs = measured Vapor pressure; PCElc = Calculated from
Raoult’s law.
Information on potential attacks to water utilities
http://www.epa.gov/safewater/publicoutreach/
http://www.agri.state.id.us/PDF/Ag%20Resources/Updates%2010-4-2001.pdf
Information on Tetrahydrofuran
1. New Jersey's Department of Health, Right to Know Program's Hazardous Substance
Fact Sheets provide chemical information on acute and chronic health hazards,
identification, workplace exposure limits, and risk reductions.
http://www.state.nj.us/health/eoh/rtkweb/1823.pdf
2. The Environmental Defense Fund's Chemical Scorecard summarizes information
about health effects, hazard rankings, industrial and consumer product uses,
environmental releases and transfers, risk assessment values and regulatory coverage
http://www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=109-99-9
3. National Toxicology Program Health and Safety Information Sheet
http://ntp-db.niehs.nih.gov/NTP_Reports/NTP_Chem_H&S/NTP_Chem1/Radian109-999.txt
4. Synopsis--Noncancer Inhalation Risk Values
RIVM has evaluated the noncancer oral toxicity data for tetrahydrofuran (THF) and
determined that there were no appropriate studies upon which to derive a tolerable daily
intake (TDI). Therefore, RIVM chose to do a route-to-route extrapolation from the tolerable
concentration in air (TCA) to estimate a provisional TDI of 10 ug/kg-day (0.01 mg/kg-day).
This TDI is provisional because it is derived via route-to-route extrapolation. The TDI was
estimated assuming 100% absorption for both inhalation and oral exposure. Taking the
daily breathing volume of an adult as 20 cu.m/day and the body weight as 70 kg, the TDI
can be derived by multiplying the TCA of 0.035 mg/cu.m by 20 and dividing the product by
70, resulting in a pTDI of 0.01 mg/kg-day. Click on the green circle(s) for more
information.
http://iter.ctcnet.net/publicurl/pub_view_l2_non.cfm?crn=109%2D99%2D9&type=NCO
5. Synopsis--Noncancer Inhalation Risk Values
RIVM has evaluated the noncancer inhalation toxicity data for tetrahydrofuran (THF) and
derived a tolerable concentration in air (TCA) of 35 ug/cu.m (0.035 mg/cu.m) based on a
12-week inhalation study in rats (Katahira et al., 1982). In this study, animals were
exposed 4 hours/day, 5 days/week, during 12 weeks. Therefore, the NOAEL of 295
mg/kg-day (for liver dysfunction and irritation of nose epithelium) was corrected for
continuous exposure by multiplying with 4/24 x 5/7, equaling 35 mg/cu.m (Basis ADJ).
Applying a UF of 1000 (100 for inter- and intraspecies variation and 10 for extrapolating
from the short duration study to lifespan exposure) results in a TCA of 35 ug/cu.m (0.035
mg/cu.m). Click on the green circle(s) for more information.
http://iter.ctcnet.net/publicurl/pub_view_l2_non.cfm?crn=109%2D99%2D9&type=NCI