Solve problems in soil water exchange and biomedia-water partitioning 1,2,3 & 5 exclude problem four.

Please show all work. Full problem set attached in PDF form below.

Problem 1 – Partitioning of Methylene Chloride in Sediment
Some river sediment containing approximately 20% of organic matter is contaminated with methylene
chloride (MC). One cubic meter of the sediment is dredged up, placed in an open container, and packed
to porosity of about 30%. A small amount of leachate from the sediment is found to have 100 mg/L
methylene chloride. Estimate the octanol-water partition coefficient, the organic carbon partition
coefficient, and the sediment partition coefficient: The bulk density of the sediment is 1.75 kg/L. Estimate
the mass of MC adsorbed to the sediment and the mass of MC contained in pore water in grams.
Problem 2 – Sorption of Volatile Compounds
Suppose you perform a batch adsorption experiment by placing 20 mL of water containing 100 mg/L of a
compound in a 40 mL vial with 0.50 grams of soil. When equilibrium is achieved the aqueous
concentration is found to be 7.60 mg/L.
(a) Compute the linear adsorption isotherm coefficient in L/g
(b) Then, however, you realize that some of the compound may have volatilized into the airspace of the
vial. From a reference, you find that Henry’s constant is 0.700. Compute the coefficient again, this
time including the simultaneous partitioning to air. Assume that soil occupies 0.50 mL of the vial.
Problem 3 – Solids-Water Distribution Ratio of Two Organic Compounds
From the data given in Tables 1 and 2 estimate Kd for a) toluene and b) petnachlorophenol (PCP).
Assume that the compounds are present at low concentrations (i.e. assume linear sorption isotherms).
Table 1: Groundwater and Solid Matrix Composition
Solid Matrix Composition
(% by mass)
Groundwater Composition
mol/l
Quartz
Kaolinite
Iron Oxide
Organic Matter
85
10
4
1
H+
O2
Na+
K+
Ca+2
ClHCO3
–
10-6
10-3.6
10-3
10-4
10-4
10-3
10-3.5
Table 2: Properties of Toluene and PCP
Property Toluene PCP
MW, g/mol
Tm, o
C
Tb, o
C
Cw
sat, mol/l
Kow (25 o
C)
pKa
92.1
-95
110.6
5.6×10-3
4.9×102
–
266.3
174
310
1.7×105
–
4.8
Problem 4 – Methyl mercury Contaminated Fish
Methylmercury (MM) is a common name for the organometallic cation [CH3Hg]+
which is an
environmental toxicant found in ocean waters as a result of anthropogenic releases. The EPA reference
dose (RfD) for MM is 0.1 g/kgd. The average consumption of fish for a person with an average weight
of 70 kg is 7.5 g/d and the bioconcentration factor (BCF) of MM in tuna fish is 106 l/kg.
1) Write a paragraph (no less than 100 words) explaining the possible sources of MM contamination
in the oceans? [Provide reference(s)].
2) Determine the MM concentration in fish (in g MM / kg of fish) that poses an unacceptable
health risk to humans.
3) Assuming that the concentration of MM in tuna fish is equal to that determined above calculate
the maximum safe concentration of MM (in g/l) in ocean water.
4) Compare the aquatic concentration value for MM calculated in the previous step with actual
values measured in the Pacific Ocean and comment.
Problem 5 – PCB Biomagnification in American Bittern
A 1-kg adult American Bittern living in the plains of the Housatonic River consumes 0.045 kg/d of
largemouth bass containing 0.10 ppm of PCBs. Assume that the bittern excretes all PCB congeners with a
first-order rate constant of 2.510-3 d-1. Estimate the steady-state total-PCB concentration in the bittern (in
ppm) and determine the biomagnification factor.