Alyssa De La Rosa
2009 JISAO/NCAS Research Internship
Measuring CO2 levels in the ocean
As someone who has lived the majority of her life in the desert, I didn't know what to expect from the opportunity to conduct research in chemical oceanography at NOAA's Pacific Marine Environmental Lab (PMEL). During my eight weeks in Seattle I worked within PMEL's CO2 group which concentrates on measuring CO2 levels in the ocean.
About a third of the CO2 released into the atmosphere is absorbed by the world's oceans. Once absorbed, CO2 reacts with water to form carbonic acid which then dissociates into even more carbon species (HCO3- and CO32-). CO2's reactivity with water prohibits researchers from measuring CO2 directly, so CO2 is measured indirectly using any two of the following parameters: alkalinity, Dissolved Inorganic Carbon, pH, and pCO2.
The indirect measurement of CO2 is part of PMEL's larger project to monitor ocean acidification. An increased concentration of CO2 in the world's oceans results in a decrease in the pH level, causing acidification. This acidification negatively impacts the marine ecosystem by decreasing an organism's ability to produce carbonate shells.
Throughout the summer I measured the alkalinity and the Dissolved Inorganic Carbon of sea water samples from around the world.
Dissolved Inorganic Carbon [DIC] measures CO2 as well as HCO3- and CO32- ions in sea water. The sample is acidified and the CO2 gas that is yielded is carried into a cell where a coulometer measures how much electricity it takes to neutralize the CO2 present. I was involved with loading samples as well as the assembly of the cell and dry traps.
Alkalinity measures the negatively charged ions HCO3- and CO32- and a variety of other negatively charged ions in solution. To measure alkalinity acid is titrated into an open cell that contains a sample of sea water. The amount of acid needed to neutralize the negatively charged ions is used to calculate alkalinity. I prepared sea water samples to be analyzed and maintained the cells and electrode.
Working at NOAA reinforced my interest in environmental science and opened my eyes to a different aspect of chemistry.
I would like to thank Dr. Chris Sabine, Cynthia Peacock, NOAA and JISAO for this great experience.