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.
  1. 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.
  2. 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?
  3. 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?
  4. 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-2-oxocyclohexyl)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% Suspended solids = 5% Sediment = 5%

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?

  1. 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).
  1. 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

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.

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

3. National Toxicology Program Health and Safety Information Sheet

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.

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.