O-buoy Project

Ozone chemistry in the Arctic is of interest due to the importance of ozone as an oxidizing agent, and because it undergoes near complete depletion events in early spring.  These ozone depletion events (ODEs) were first observed in the mid-eighties by Bottenheim et al.  Since then, people have been trying to understand how they happen, why they happen, and how they influence other important chemical reactions in the region.  It is believed that these ODEs are a product of a catalytic bromine cycle that can only happen under special conditions (e.g. low temperature, presence of sunlight, large bromine source, and ice/aerosol surface upon which to regenerate the chain precursors).  Bromine comes from sea salt, which is readily available at the Arctic coastal sites where ODEs are observed.  However, how the bromide converts to Br2 and BrCl, and subsequently reacts with ozone, is slightly less well understood.  The current mechanism involves the bromide ion reacting with ozone, or a BrCl molecule (rxns 1-2; both of which are relatively slow).  In an appropriately acidic solution (1) can go on to form the hypohalous acid and eventually molecular bromine (3), which can then photolyze to bromine radical and react with ozone (4, yields a Br radical which has a much faster rate constant for the ozone reaction than does Br-).  The monoxide will then self react to form molecular oxygen and bromine (5).  Since reaction 3 involves one Br atom in the gas phase (HOBr) reacting with a surface to produce two reactive bromine atoms (Br2), this is called the bromine explosion.                      

                                 (1)

               (2)

     (3)

                      (4)

                                          (5)

To date there have been many measurements of the BrO radical and ozone over coastal Arctic land masses; however, there have been few over the ocean (source of bromine and reactive surfaces), and certainly none for extended periods of time.  The goal of our research is to measure ozone, bromine monoxide radical, CO2, and various meteorological parameters over the Arctic sea ice for periods on the order of a year without human intervention. 

To achieve our goals we have collaborated with groups at U.S. Army Corps of Engineers’ Cold Regions Research and Environmental Laboratories, Monterey Bay Aquarium Research Institute, University of Alaska Fairbanks, Bigelow Laboratory for Ocean Sciences, Environment Canada, Jonathan Amy Facility for Chemical Instrumentation at Purdue University, and SRI International to build an autonomous buoy that will be placed on the ice to make the above mentioned measurements and relay the data back to the lab via satellite. 

Instruments can be seen in the figures below.  The buoy will be launched in a lagoon in Barrow, Alaska in Fall of 2008 (presumably October or November, depending on when the ice is thick enough) for first stages of testing.  Such a site is ideal as it is close enough to monitor the buoy, instrumentation, and battery packs and make any changes before deploying the following year in the ocean. 

Figure 1: Instrumentation that will be put in the buoy (not pictured is the central computer and satellite communications box (Iridium)).

Figure 2: Picture of the mast that will be the top of the buoy including the various meteorological instruments (wind speed, humidity, temperature, orientation).