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Case Study 1- Mercury in the Global Ocean

Case studies must be completed during the course and must be submitted by the due date and time listed on the course calendar. Note that you can submit them earlier in the semester.

The assignments must be sent to the instructor through Canvas as an attachment and the file name must include your

Last Name, class name and section number and Assignment title.

Any assignment not following this guideline will be 
not be graded. 

You must also include references for your answers.  Do not copy and paste from the internet, I do perform a SAFE ASSIGN check for plagiarism!

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107 Assignment – 25 pts FALL 2021 -Mercury in the Global Ocean-1.docx




 
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Mercury in the Global Ocean

PURPOSE


: USE THE NEWS: The following assignment uses real world data and news sources. Check your understanding of the material and then offer a well-supported response.

– 25 pts

Although the days of odd behavior among hat makers are a thing of the past, the dangers mercury poses to humans and the environment persist today.

Mercury is a naturally occurring element as well as a by-product of such distinctly human enterprises as burning coal and making cement. Estimates of “bioavailable” mercury—forms of the element that can be taken up by animals and humans—play an important role in everything from drafting an international treaty designed to protect humans and the environment from mercury emissions, to establishing public policies behind warnings about seafood consumption.

Yet surprisingly little is known about how much mercury in the environment is the result of human activity, or even how much bioavailable mercury exists in the global ocean. Until now.

A new paper
 by a group that includes researchers from the Woods Hole Oceanographic Institution (WHOI), Wright State University, Observatoire Midi-Pyréneés in France, and the Royal Netherlands Institute for Sea Research appears in this week’s edition of the journal Nature and provides the first direct calculation of mercury in the global ocean from pollution based on data obtained from 12 sampling cruises over the past 8 years. The work, which was funded by the U.S. National Science Foundation and the European Research Council and led by WHOI marine chemist Carl Lamborg, also provides a look at the global distribution of mercury in the marine environment.

“It would seem that, if we want to regulate the mercury emissions into the environment and in the food we eat, then we should first know how much is there and how much human activity is adding every year,” said Lamborg, who has been studying mercury for 24 years. “At the moment, however, there is no way to look at a water sample and tell the difference between mercury that came from pollution and mercury that came from natural sources. Now we have a way to at least separate the bulk contributions of natural and human sources over time.”

The group started by looking at data sets that offer detail about oceanic levels of phosphate, a substance that is both better studied than mercury and that behaves in much the same way in the ocean. Phosphate is a nutrient that, like mercury, is taken up into the marine food web by binding with organic material. By determining the ratio of phosphate to mercury in water deeper than 1,000 meters (3,300 feet) that has not been in contact with Earth’s atmosphere since the Industrial Revolution, the group was able to estimate mercury in the ocean that originated from natural sources such as the breakdown, or “weathering,” of rocks on land.

Their findings agreed with what they would expect to see given the known pattern of global ocean circulation. North Atlantic waters, for example, showed the most obvious signs of mercury from pollution because that is where surface waters sink under the influence of temperature and salinity changes to form deep and intermediate water flows. The Tropical and Northeast Pacific, on the other hand, were seen to be relatively unaffected because it takes centuries for deep ocean water to circulate to those regions.

But determining the contribution of mercury from human activity required another step. To obtain estimates for shallower waters and to provide basin-wide numbers for the amount of mercury in the global ocean, the team needed a tracer—a substance that could be linked back to the major activities that release mercury into the environment in the first place. They found it in one of the most well studied gases of the past 40 years—carbon dioxide. Databases of CO2 in ocean waters are extensive and readily available for every ocean basin at virtually all depths. Because much of the mercury and CO2 from human sources derive from the same activities, the team was able to derive an index relating the two and use it to calculate the amount and distribution of mercury in the world’s ocean basins that originated from human activity.

Analysis of their results showed rough agreement with the models used previously—that the ocean contains about 60,000 to 80,000 tons of pollution mercury. In addition, they found that ocean waters shallower than about 100 m (300 feet) have tripled in mercury concentration since the Industrial Revolution and that the ocean as a whole has shown an increase of roughly 10 percent over pre-industrial mercury levels.

“With the increases we’ve seen in the recent past, the next 50 years could very well add the same amount we’ve seen in the past 150,” said Lamborg. “The trouble is, we don’t know what it all means for fish and marine mammals. It likely means some fish also contain at least three times more mercury than 150 years ago, but it could be more. The key is now we have some solid numbers on which to base continued work.”

“Mercury is a priority environmental poison detectable wherever we look for it, including the global ocean abyss,” says Don Rice, director of the National Science Foundation (NSF)’s Chemical Oceanography Program, which funded the research. “These scientists have reminded us that the problem is far from abatement, especially in regions of the world ocean where the human fingerprint is most distinct.”

The Woods Hole Oceanographic Institution is a private, independent organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.

Assignment QUESTIONS: (25pts)

1. Which of the following most accurately states the question the researchers are trying to answer during the scientific inquiry? (2.5 pts)

a. How much mercury is safe for humans to consume?

b. How does mercury act as a toxin in the human body?

c. How much mercury accumulates in various types of fish?

d. How much mercury in the ocean is from natural sources versus human sources?

2. Which of the following statements most accurately describes how scientists on this project conducted their research? (2.5 pts)

a. They designed a controlled experiment by exposing tanks of seawater in a lab to various sources of mercury.

b. They used a natural experiment by taking measurements before and after a large release of mercury from a coal-fired power plant.

c. They used data gathered on mercury concentrations in ocean-floor sediments.

d. They used data gathered on mercury, phosphate, and carbon dioxide at various ocean depths to construct a model.

3. What role did observation of carbon dioxide play in this study? (2.5 pts)

a. It acted as a tracer that could help determine the human activities that released mercury into the ocean.

b. It showed how mercury is taken up into the marine food web.

c. It helped the researchers develop an estimate for deep-water mercury concentration.

d. It helped neutralize the toxic effects of mercury.

4. In a few COMPLETE sentences, how would you summarize Lamborg’s conclusion about the study results? (2.5 pts)

5. If you were one of the scientists working on this research, would you recommend that the United States act or not act on the basis of this information? In a paragraph, provide your recommendation using the information from the article and CHAPTER 16 to support your case. In your answer, consider some of the trade-offs of your decision, and why it might or might not be view as sustainable. (15 pts)