Lesson 12: Water Pollution
This week we'll again focus on Earth's water resources, but instead of looking at freshwater supplies we'll examine the causes of water pollution (like storm drain runoff, right) and how the damage done by pollutants can, in some cases, be remediated. Water pollution is not an "uplifting" topic, but it's a critically important one. Keller points out that 40% of Earth's human population does not have regular access to clean, disease-free drinking water, and as both surface and ground water sources become increasingly depleted it's more important than ever that we learn how to prevent pollution and keep available water supplies clean and suitable for a variety of human and environmental purposes.
Keller opens chapter 14 with a discussion of the various types of pollutants (oxygen-demanding wastes, pathogens, nutrients, oil, etc.) that degrade water quality, and discusses how some of these lead to "indirect" problems through processes such as eutrophication and biomagnification. He goes on to examine some of the major settings in which surface and groundwater contamination occur, and closes with a look at how wastwater can be treated before being discharged into surface or groundwater systems. This week's exercise on groundwater contamination also provides something of a bridge between a topic we covered last week—groundwater flow—and one—water pollution—that is at the heart of this week's lesson.
As you read through the introduction to water pollution in our text and study the accompanying websites it will be helpful to take careful notes. Writing out key facts in your own words or making neatly labeled drawings will help you better understand the significance of what you've read and spot any gaps in your knowledge. Having complete notes will also make it easier for you to review for this week's quiz and and access what you've learned when you want to refer back to it for future assignments. Be sure that you are prepared to meet the learning objectives outlined below before you move on to the quiz at the bottom of the page.
Weekly Learning Objectives
Upon successful completion of this week's lesson, a student is expected to be able to:
- List the major types of water pollutants, and for each describe: what the typical sources of pollution are, what problems it causes, and what strategies we can use to minimize or remediate such pollution.
- Outline the steps that link the release of excess nutrients to the occurrence of oxygen depletion in lakes and streams due to eutrophication.
- Suggest which types of samples you might collect to determine if PCB and heavy metal contamination still lingers in an aquatic environment even if contaminant levels are too low to detect in the water, and state your rationale for studying each sample. (Hint: Consider the effects of biomagnification.)
- Distinguish between point sources and non-point sources of surface water pollution.
- Predict which of the following types of mines or quarries is likely to be sources of acid mine drainage, and explain his or her reasoning in each case: (1) a limestone quarry where calcite (CaCO3) is mined; (2) a copper mine in which chalcopyrite (CuFeS2) is the primary ore mineral; and (3) a chrome mine in which chromite (FeCr2O4) is the primary ore mineral.
- Outline concerns about disposal of wastewater using a septic tank system in an area with: (1) relatively impermeable, clay-rich soil or (2) a very permeable, sandy soil and a seasonally shallow water table.
Reading and Browsing Assignment
- Read Chapter 14, focusing on the topics outlined in the learning objectives above.
- To learn more about water pollution across the United States and how it's being monitored, check out the U.S. Geological Survey's National Water-Quality Assessment Program site.
- Lake Tahoe is one of the largest bodies of water in California, and has suffered a significant loss of water quality due to nutrient loading as development and deforestation have occurred in the surrounding alpine basin. To learn more about what's happening at Lake Tahoe and what's being done to monitor and preserve water quality there check out the UC Davis Lake Tahoe site.
- Finally, for a look at how acid mine drainage is being dealt with here in California, check out the California Geological Survey's work on the cleanup of the Spenceville Mine in Nevada County.
Exercise 12: Groundwater Contamination (Due by 9:00 AM on 7-Nov-2011)
After you have studied chapter 14 and mastered the learning objectives outlined above please point your browser to the Hazard City website and work through version 1 of the Ground Water Contamination assignment. This is a fairly involved project, so allow a couple of hours to complete it. I found it helpful to print out the various reports so that I had all of the information at hand before I began to calculate my water table elevations. If you are familiar with how to use a worksheet program (e.g., Excel) you'll find that it may be easier to enter the well elevations and depths to water into a worksheet and use the program to calculate the water table elevation rather than doing all of the calculations by hand. Be sure to jot down any useful notes on the procedure you followed and have your final map in hand before you go to fill out the report at the end of the assignment. (I suggest printing the report form, filling it in, and then adding any notes that might be helpful.) Finally, go to the "Assignments, Tests, and Surveys" area of the Etudes site to complete Exercise 12. There are nine questions (five from the report and four related questions that I added), so each is worth 1.11 points.
Quiz 12: Water Pollution (Due by 9:00 AM on 7-Nov-2011.)
After you feel you have met the learning outcomes outlined above, please complete Quiz 12 in the Etudes "Assignments, Tests, and Surveys" area. There are ten questions, each worth one point. If you can answer all of them correctly it means that you know your way around the basics of water pollution pretty well and are ready to move on to a more detailed look at minral resources next week. Remember, answers will be available for review after 10:00 AM on the Tuesday after the quiz closes, so please look over the results of your quiz and contact me if you have any questions about either content or scoring.