Homework: Redox Homework 2016 due: 5/3/2016
Reading: National Lakes Assessment (Executive Summary and Chapter 7), Stormwater control, Monitoring Uncovers Mysterious Phosphorus Pollution (Full paper in ES&T)
Homework: None. Study for Second Exam.
Exam Content: Example Exam – CH217 Exam II 2013. Exam II will focus on topics since exam I, but will also build on fundamental knowledge such as residence time, reaction rates, concentration scales, and steady state processes.
Reading: Nutrient Cycling in Lakes
In the News: Bubbles as a remedy for ocean acidification?
Homework: Due 4/14/2015 – Key: P and O2 flux in lakes 2016
Consider a lake of infinite horizontal dimension, a depth of 20 meters, and a thermocline at 10 meters. The epilimnetic temperature is 25 oC. The hypolimnetic temperature is 6oC. Both layers are well mixed vertically. The alkalinity of the lake is 0.10 mM. The hypolimnion volume is 10% of the epilimnetic volume. Draw a sketch of the lake and use it to answer the questions below.
1) Calculate the equilibrium concentration of oxygen at depths of 5 and 15 meters in units of ppm and moles/liter.
2) Lakes in Maine tend to bloom when the dissolved phosphorus in the springtime is above 12 ppb (as P). Assume that all of 12 ppb P is converted to biomass in the epilimnion. What fraction of the epilimnetic biomass is required to reduce the oxygen in the deep water to below 1 ppm?
3) If bacterial oxidation of the deep biomass is complete, what is the phosphourus concentration in the deep water just before the fall overturn?
4) Qualitatively, will the pH of the deep water increase or decrease over the course of the summer?
Overview of Water Properties – Look UP – Ice Floats
Homework: We are beginning a series of homework assignments calculating the physical and chemical properties of water. Please create ONE Workbook with multple worksheets, one for each assignment. You will be able to use your workbook for the next exam. This week you will create two worksheets.
1) Calculate the density of water as a function to temperature and salinity. Plot the density as a function of temperature for four different salinities (0 to 35 o/oo). At what salinity will cold water no longer have a density maximum? Assume that you have two 1 meter cube blocks of water sitting on top of each other. The top block is 25 0C and the bottom block is 15 oC. How much mechanical energy would be required to mix the water in both blocks?
2) Calculate the solubility of oxygen in mg/L and micro mole/L as a function of temperature and salinity. Plot the solubility of oxygen as a function of temperature for four different salinities (3 to 35 o/00).
Hand in each worksheet printed on a single page of paper. Due 4/7/2016
http://pubs.acs.org/doi/pdf/10.1021/es040686l – Surface Water Trends
Reading: Jacobs: Chapter 11 and 12.
Homework: Due: 3/31/2016. In May 2015 I purchased a VW Golf Diesel Wagon due to the excellent performance and fuel economy (50 mph at highway speeds). In September 2015 VW acknowledged that they cheated on the emissions test: Everything You Need to Know About the VW Diesel Emissions Scandal. My car is producing more NOx than is allowed by EPA emission limits. It is also producing a lot less CO2 than most other cars. VW is required to provide a fix for the car, but everyone expects this will come with decreased mileage and performance. What are the environmental tradeoffs for a 2015 Turbo Diesel Golf Sportwagon assuming that I drive the car in Waterville? Is the NOx or CO2 a greater environmental concern?
Parameters for the Model:
- Cars in greater Waterville – 10,000.
- Assume all cars are 2015 diesels that drive 15,000 miles per year
- Area of Greater Waterville is 5 km x 5 km
- Assume VW NOx emissions are 10X the legal limit for all cars
- VW diesel fuel economy is 50 mpg diesel
- We will use the EPA emission standard of 0.91 g/mile for NOx.
- Assume a troposphere mixed layer height of 2 km.
- The 2015 EPA CO2 limit is 245 g/mi (CO2 emissions)
We will focus on ozone and CO2 as the primary pollutants of concern. How much will ozone increase in Waterville on a warm summer day, with no appreciable wind, if everyone drove a VW diesel? Outline your calculation and assumptions in detail. How does this compare to the environmental impact of less CO2?
Reading: Chapters 18, 19, 20, IPCC Reports
Homework: 1) Calculate the average global temperature of the earth if it were 20% closer and 20% further away from the sun. 2) How would this average global temperature change with increasing CO2? 3) How would doubling the volume of the deep ocean impact atmospheric CO2 concentrations? 4) Why is the global warming potential of some gases many times higher than the GWP of CO2? – due 3/8/2016.
First Exam: 3/10/2016. Examples Exam – CH217 Final 2013
Reading: Jacobs 10: Oxone Hole
Homework: due – 3/3/2016
- Using the attached ozone model ( ozone model) calculate how much faster the rate constant k4 in the Chapman mechanism needs to be to decrease stratospheric ozone by 10%. How does Cl in the stratosphere catalyze reaction 4?
- Using the link (http://aura.gsfc.nasa.gov/science/feature-022207.html) as a starting point, sketch the concentrations of HNO3, HCl, CLO, and O3 (as a function of time) in the Antarctic stratosphere during the winter of 2006. On your figure list the most significant reactions that drive the observed concentrations. What do you predict for the residence times of each of these species?
Resources: CH217-L5.Atms2 2016
Reading: Chapter 15 and 16
In the News: How Lead Ended Up in Flint’s Water
Homework: (due 2/25) Consider the following global phosphorus cycle:
Calculate the evolution of atmospheric oxygen assuming zero oxygen in the atmosphere at time zero. Assume that the flux of oxygen TO the atmosphere is 138 times (mole/mole) the flux of P from the surface to deep ocean and the flux of oxygen FROM the atmosphere is 138 times the flux of P from the deep to surface ocean. Modeling the figure above using simple finite difference approximations is tricky because the surface box needs short time steps (<100 years) and the evolution of oxygen in the atmosphere takes at least 0.6 billion years. It would be a very long spreadsheet indeed!
An alternative is to assume that the entire ocean rapidly reaches steady state between the surface and deep reservoirs.
The net rate of oxygen production is F2-F3, where F2 is a small fraction of the total phosphorus added to the ocean via weathering. Over time, net photosynthesis will increase atmospheric oxygen with 138 O2 produced per mole of P consumed. A problem is that the ocean can’t hold enough organic material [(CH2O)106(NH3)16PO4] to produce significant amounts of oxygen. Significant amounts of organic material must be buried through subduction or precipitation (Prec. Flux).
Using the attached model as a guide, global oxygen flux V2, please answer the following questions:
- Write the coupled equations describing the formation and consumption of oxygen. (Notice the conversion between mass of P and moles of O2).
- How was the pressure of O2 in the atmosphere calculated?
- How long does the model take to produce the current levels of oxygen? How does this compare to figure 16-12 in your text? Play with the fraction of biogenic P to improve the model
- Using table 16-1, does the simple oxygen flux model agree with the estimates for reduced carbon (organic material) abundance on the Earth?