a. What is the maximum concentration of TCE in water downstream of the tank, assuming the TCE fully mixes with the stream? [2 pts.

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1 FATE AND TRANSPORT CE/ESM 4/579 PROBLEM SET [2 pts.] A small lake is found to be contaminated with chloroform (CHCl 3 ), which is a by-product of the chlorine disinfection of municipal waste water that is discharged to the lake. Small fish in the lake are sampled and are found to have acquired a chloroform concentration of 24 ppb in their fatty tissue. Fish-tissue samples taken quarterly over the past year reveal steady and consistent levels of chloroform. If fatty tissue behaves similarly to octanol with respect to chloroform partitioning, what is the probable approximate concentration of chloroform in the lake water? 2. [2 pts.] A stoppered flask at 25 C contains 300 ml of water, 200 ml of octanol, and 60 ml of air. An unknown amount of o-xylene is added to the flask and allowed to partition among the phases. After equilibrium has been established, 6.0 mg of o-xylene is measured in the water. What is the total mass of o-xylene present in the flask? 3. [3 pts.] A leaking tank drips trichloroethene (TCE) into a small stream at a rate of 12.0 g/hr. Stream discharge is 6.6 m 3 /hr, and the stream depth is 120 cm. a. What is the maximum concentration of TCE in water downstream of the tank, assuming the TCE fully mixes with the stream? [2 pts.] b. Does any DNAPL accumulate on the stream bottom? Discuss your answer if necessary. [1 pt.] 4. [3 pts.] The suspended solids content of a 1-liter lake water sample is 120 mg/l. Analysis reveals this solid material contains 70% organic carbon. The lake is suspected of being contaminated with atrazine, a widely used member of the triazine family of herbicides, as well as phenanthrene, a polynuclear aromatic compound. For both compounds, an analytical laboratory offers to analyze the total concentration in the whole, unfiltered water (compound in water plus in suspended solids), and, in water passed through a 0.20 µm filter, which removes all of the particles (compound only in the water). Your boss asks you if filtration makes much difference; should you pay for the extra step? a. What is the difference in the expected concentration of each compound in unfiltered water compared to filtered water? Express in terms of the measured concentration C w, (mg/l) of the filtered sample. You do not need a particular concentration (numerical) to answer this. The answer is of the form C T = XC w where X is the factor that express the difference in concentration between unfiltered and filtered samples. (E.g., X = 1.00 means no difference, X = 1.60 means the unfiltered has 60% more compound, etc. X must be greater or equal to 1.00.) [2 pts.] b. What will you tell your boss? Is the answer the same for both compounds? [1 pt.]

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3 Some Properties of Various Chemicals Chemical (glmol)a (glcm3)a (mglliter)b (atm)b (atm m3/mol)b (dimensionless)b Kow c Comments Acetic acid l Aroclor d 1.50 d l.2 X X X 10-3 l.2 X < Polychlorinated biphenyl mixture (PCB) Aroclor l.22d l.57 d 2.7 X X X X < Polychlorin~ted biphenyl mixture (PCB) Atrazine d 33 b 4 X lo- loj 3 X 1O-9j 1 X 1O-7j 2.68 b Herbicide Benzene l.25 X X X Gasoline constituent Benz [al anthracene X 1O-4g 6.3 X 1O-9g 5.75 X 1O-6g 2.4 X 1O-4g 5.91 Polycyclic aromatic hydrocarbon (PAH) Benzo(a)pyrene X 1O-5g 2.3 X 1O-1Og l.20 X 1O-6g 4.9 X 1O-5g 6.50 PAH Carbon tetrachloride l X X b Chlorobenzene l l.6 X X 10-3 l.65 X Chloroform X X 10-1 l.97b m-cresol g l.96 Cyclohexane g O.13g 0.1& 7.3g ,1-Dichloroethane l g 3.0 X 1O-1g 6 X 1O-3g 2.4 X 1O-1g l.79 1,2-Dichloroethane l g 9.1 X 1O-2g 1O-3g 4.1 X 1O-2g l.47 (continues)

4 (continued) Chemical (glmol)a (glcm3)a Cmglliter )b (atm)h (atm m 3/mol)b Cdimensionless)b Kow c Comments cis-l,2-dichloroethene h X h 1.86h trans-l,2-dichloroethene h 0.45h 6.7 X 1O-3h 0.23 h 2.06 h Ethane X 1O-3g 39.8g 4.9 X 1O- 1g 20g Gas Ethanol X 1O-2h 6.3 X 1O-6h h Booze Ethylbenzene X X X 10-1 Lindane X X X 10-5 Pesticide Methane O.66g 27g Natural gas Methylene chloride X X X Also called dichloromethane Naphthalene X X X PAH Nitrogen Atmospheric gas n-octane O.72g 0.019g 2.95g 121g 4.00h Alkane Oxygen Atmospheric gas Pentachlorophenol X X X 10-4 n-pentane g 0.69g 1.23g 50.3g 3.62 Perchloroethene X X X Commonly used in dry cleaning; tetrachloroethene Phenanthrene g 8.9 X 1O- 7g 3.5 X 1O- 5g 1.5 X 1O-3g 4.57 PAH Styrene b (continues)

5 (continued) Chemical (glmol)a (glcm3)a (mglliter)b (atm)b (atm m3/mol)b (dimensionless)b Kow c Comments Toluene X X X A common solvent 1,1,1-Trichloroethane X X A common solvent (TCA) Trichloroethene (TCE) X X X A common solvent a-xylene X X X 10-1" 3,12 1,2-Dimethyl benzene Vinyl chloride g Degradation product of TCE avalues from Weast (1990), unless otherwise noted. Densities measured between 15.5 and 22 C, except for a-xylene at 10 C and phenanthrene at 4 C. blyman et al. (1990). Solubility, vapor pressure, and Henry's law constants are for 20 C, unless otherwise noted. cschwarzenbach et al. (1993). Note that Kow values are for 25 C. dvalues from Budavari (1989). Average number of chlorines per molecule for Aroclor 1254 and Aroclor 1260 is 4.96 and 6.30, respectively. eestimated from values in Anderson and Parker (1990). friederer (1990). gschwarzenbach et al (1993). Solubility, vapor pressure, and Henry's law constants are for 25 C. hhoward (1990). Vapor pressure for cis-l,2-dichloroethene is for 35 C. Solubility and vapor pressure for trans-l,2-dichloroethene are for 25 C. Vapor pressure for ethanol is for 25 C.