Problem set 1. Due Sept. 10
1. page 23, # 1.
2. page 23 # 3;
3. Write a balanced equation for the microbial oxidation of octane to CO2.
4. page 77, # 3
5. page 77, # 4
Problem set
2. Due
Sept. 19
1. Using the data for the Berino soil in the lecture notes answer the following questions. a) If 5 cm of water are ponded on the a 10 cm column of soil, (diameter = 5 cm) what will be the rate of water flow, in L d-1, from the column under saturated conditions. What is the pore water velocity if the porosity is 0.4? First calculate the Darcy velocity, then calculate the pore water velocity.
2. Two piezometric
wells, wells designed to allow good measurement of water table height,
are 100 m apart and the surface of the water table in well 1 is
measured at -10.0 m relative to a benchmark on the surface. The
water table in well 2 is at -10.25 m. The hydraulic conductivity in the
aquifer is 5.0 m d-1. Bromide (Br-) is added to well 1
as potassium bromide. (Bromide does not degrade nor adsorb to soil
particles and can be used as a tracer). In how many days will you
expect bromide to appear at well 2 assuming plug flow (no
dispersion). How might dispersion affect the appearance of
bromide? Hint: First calculate the Darcy velocity, then calculate
the groundwater (pore water) velocity. Assume effective porosity = 0.3.
3. Using the data in problem 2 and the Bioscreen computer program
simulate the development of a Br plume over 10 years. Use default
dispersivities and retardation factor of 1 (no adsorption). Leave
the default water table thickness at 10 ft. Br
solution is added as a 1000 mg/L solution which defines the solution
concentration at plus and minus 14 ft from the centerline of the
axis of flow at time zero. At greater distances the initial
concentrations are zero. Total added Br = 10 kg . Effective
porosity = 0.3. Since Br- does not degrade, ignore the the
degradation components and just look the nondegradation output
plots. Report your input hydrologic parameters. Print
the results of concentration plot along the length of the plume after
10 years. Have a look at the animation. If the edge of the plume
is defined by 1 ppm Br what are the leading edge and trailing edge
distances from the source and what is the maximum width
of the plume. You will have to play with the plume length
and width settings.
Note: You may have to
reset the secrurity level for your Excel program, so you can run the
macros. Use the tools pull-down menu. The program does not
work well on a Mac computer.
Problem set 3. Due Oct. 1.
1. A solution contains 0.0010%
cadmium (wt/wt). Express concentration in water as:
g L-1
mg L-1
microgram L-1
nanogram L-1
ppm
ppb
ppt
M (molar)
m mol L-1
micro mol L-1
nanogram L-1
2. If soil water
contains trichloroethene (TCE) at 0.5 mg L-1 what is the
equilibrium
concentration of the TCE in the soil
air. Use TOXNET for any data you
might need. The Henry's Law constant in TOXNET is
atm-m3/mol. This requires soluble concentration of in mol/m3
(1000 L = 1 m3 ). The answer then will be in
partial
pressure units in atmospheres.
3. The tabulated Koc for naphthalene
sorption in soil is 870 L/kg. A soil analysis shows a contaminated soil
to contain 50 mg kg-1 of naphthalene and has 2% organic
carbon. What is the
retardation coefficient for a soil with a bulk density of 1.3
g/cm3 and a volumetric water content of 30%. Comment
on the
mobility of
naphthalene in soils
4. A herbicide with a half-life of
14 days in soil is added to a soil.
What is the fraction of
herbicide remaining after 21 days? Hint: First calculate the rate
constant.
5 and 6. Use the Bio Screen model
for the estimation of concentration distribution with distance from a
spill of toluene in a shallow aquifer after 1, 5 and 10 years following
the spill of
300 kg of toluene through a small hole in an underground pipe. Initial
concentration +/- 10 ft
from source is 1/4 the solubility limit, and it drops off beyond
that . The aquifer is anaerobic and first order biodegradation
takes place at at the rate reported for anaerobic degradation in
TOXNET. The hydraulic conductivity is 10.0 m/d and the gradient
is 0.5 ft per 100 ft in a shallow aquifer at 10 ft from the
surface. The organic C in the aquifer is 0.1% and the bulk
density is 1.7 g/cm3. The aquifer is 15 ft
thick. Use the
default dispersion data in Bio Screen. You can work in pairs on this
problem. Assume and effective porosity of 0.3.
In the box where you set the
distances from the centerline of the initial plume use 10, 30 and 60
ft. Thus the "center" is at 10 feet (this is actually plus or
minus 10 feet). You will sometimes get odd results if this is set this
to zero. Enter a concentration of 1/4 the solubility. At 30
ft enter 1/8 the solubility and at 60 ft enter 0.
Change the simulation time to 10
years and report the results at 1, 5, and 10 years. You will need
to look at quite a long plume length to find out how far the TCE will
move.
Model the centerline and the lateral
spread of the plume (see Array). Show the development of the plume at
1, 5, and 10 years. Show your input values. What is the seepage
(groundwater) velocity? What is the first order decay constant?
Problem set 4. Due Oct. 21.
1
and 2. Use the data in IRIS to estimate a the maximum allowable
concentration of As in drinking water for a lifetime exposure to
a single source of water. Use standard exposure assumptions and
assume the water is the only exposure to As. Calculate the
allowable concentration two ways; 1) assume non cancerous risk only and
use the RfD for oral exposure, 2) assume cancerous risk only and use
the slope factor for oral exposure. Assume a 50 kg adult.
Compare with the current MCL. For #2 assume the standard upper
bound for cancer risk of 10-5 (1 in a hundred thousand)
3 and 4. Soil data from a highly contaminated site show mean
concentrations of; Pb = 500 ppm, Sb (antimony) = 25
ppm, barium = 1000 ppm, beryllium = 50 ppm, cadmium = 25 ppm, copper =
10 ppm, nickel = 125 ppm, thallium = 3 ppm, tin = 8000 ppm, 1, 2
dicholro benzene 25 ppm, 1, 3 dicholor benzene = 25 ppm,
pentachorophenol = 5 ppm and benzo [a] pyrene 1.5 ppm and PCB = 1
ppm. Evaluate the risk to human health for two possible future
land uses; industrial (industrial chronic exposure) and
residential. Use the MPCA Tier 2 Soil Risk Assessment
spreadsheet. What is are the hazard quotients for target
organs and increased cancer risk for each scenario.
Given the assumption of no excess cancer risk of greater that 10-5 and
the MPCA assumptions for non-cancer risk, will cleanup be needed?
Suggest reasonable cleanup goals. Explain the differences between the
different results for the different land uses. You can work in
pairs on this.
Problem set 5. Due Nov. 5
1. problem 1. p. 311 Assume first order decay.
2. problem 3. p. 311
5. problem 9. p. 449
4. Use the data from lecture for dairy manure to calculate the quantity
of anaerobic liquid manure application using, a) N-need based
application and b) P-need based application. Assume 20% volatile
losses. Apply to corn assuming that that all of the
ammonium N is available and use the availability for organic N
(mineralization) given in lecture for the first year after
application. Assume the manure is injected. Assume the soil test
calls for an application of 50 lb/ac of P2O5. Assume the corn will
require 200 lb/ac of N and the soil will supply little N.
Calculate in lb and acre units .
Problem set 6. Due Nov. 24
Problem
Solutions