DEVELOP National Program
Langley Research Center
MyNgoc Nguyen, Old Dominion University (project lead)
Stephen LaPointe, American Public University System
Brittney Jennings, Christopher Newport University
Angela Zoumplis, Christopher Newport University
On April 20, 2010, the Deepwater Horizon drilling rig belonging to oil company BP exploded and leaked a huge volume of oil into the Gulf of Mexico. In an effort to control the spread of the oil, BP applied dispersants such as Corexit and conducted in situ burnings of the oil. This catastrophe created a complex chain of events that affected not only the fragile water and land ecosystems, but the humans who breathe the air every day. Thousands of people were exposed to fumes associated with oil vapors from the spill, burning of the oil, and the toxic mixture of dispersants.
While aiding in clean-up efforts, local fishermen were directly exposed to fumes when working in the Gulf. Many Gulf Coast residents were also exposed to the oil fumes as seasonal southeasterly winds blew vapors toward land. The Volatile Organic Compounds (VOC) found in the oil vapor include: benzene, toluene, ethyl benzene, xylene, naphthalene, hydrogen sulfide and particulate matter (PM). With the approach of summer, the increases in water temperature and sunlight resulted in more rapid evaporation of VOCs and PM. Moreover, the dispersant that was used to break up the oil is highly toxic and is thought to be even more toxic than the oil itself (EPA website, 2010).
To protect human health, the environment, and to make informed policy decisions relevant to the spill, the U.S. Environmental Protection Agency Region 6 (EPA) has continuously monitored the affected areas carefully for airborne pollutants that are associated with petroleum products and the burning of oil along the coast. In an effort to prevent, prepare for, and respond to future oil spills that occur in and around inland waters of the United States, the EPA has been working with local, state, and federal response partners.
CALIPSO and HYSPLIT Augment Fixed Monitoring Stations
Air quality measurements were collected by the EPA at five active monitoring systems stationed along the coast. There are fixed monitors in Alabama, Louisiana, Mississippi, and Florida. However, the EPA does not have any fixed monitoring stations over the water, which makes it extremely difficult to collect data on the amount and intensity of aerosols over the sea. To assist the EPA Region 6 air quality monitoring efforts, the DEVELOP team investigated the use of the CALIPSO lidar (CALIOP) level 2 version 3.01 night-time aerosol products and the HYSPLIT model to monitor aerosols and dispersants over the ocean resulting from the Deepwater Horizon oil spill. CALIOP is a two-wavelength polarization-sensitive lidar that provides high-resolution vertical profiles of aerosols and clouds. Since CALIOP has a 5km horizontal resolution and a 16-day repeated orbit, aerosol information from the affected oil spill area can be obtained with great spatial and temporal resolution. The lidar produces already processed aerosol information in 3 different swaths that correspond to a geo-specific area of interest.
One swath was selected and tracked according to its precision compared to the actual coordinates of the oil spill. As a result of the swath analysis, one CALIOP image was obtained for each month from April 2009 to October 2010. The 2009 aerosol information served as a reference for peak analysis. Discrepancies that were found between the 2009 and 2010 data resulting from the peak analysis were further investigated for possible confounding factors. These factors included the Yucatan burning, and in situ burnings from non-BP sources. After investigation, these sources of confounding were found to have minimal affect on aerosol activity in the surface level, the primary level of interest for the project.
Resolving CALIOP and EPA Data Differences
In addition, correlations were made between the CALIOP aerosol profile and the air quality data provided on the EPA website. Since the results from the CALIOP data analysis were qualitative and the results from the EPA PM 2.5 were quantitative, a major obstacle was finding an easier method of making the two sets of data more comparative. To achieve this feat, the CALIOP data was first analyzed for a trend in overall aerosol activity before and after the occurrence of the oil spill and the EPA data was then pulled from the same time and area of interest. Any discrepancies that were found in the peak analysis of the aerosol profiles were further analyzed using the EPA PM 2.5 data. Results of the peak analysis from the CALIOP data revealed that there is a significant amount of aerosol activity in 2010 compared to 2009 within the area of the Gulf of Mexico Oil Spill. Similarly, a linear regression of the EPA PM 2.5 data from 2010, 2008 and an established EPA baseline revealed a significantly higher level of PM 2.5 in 2010 after the occurrence of the oil spill. When correlating the CALIOP and EPA data, it was found that both sources of data showed more aerosol activity in 2010 compared to previous years. CALIOP aerosol profile information can supplement EPA air quality monitoring and serve as a tool to help EPA understand the aerosol activity over the ocean.
The HYSPLIT model from the U.S. National Oceanic and Atmospheric Administration (NOAA) was also used to supplement EPA air quality monitoring in the Gulf of Mexico. A detailed analysis of all trajectories ran before, during and after the Horizon oil spill was conducted. Trajectories were analyzed for smoke plume travel patterns and directly correlated with wind pattern and EPA data. Great attention was given to the elevation of each new trajectory and how uniform the overall trajectories appeared monthly. Forward trajectories were utilized due to the ability to predict and track the distribution and direction of pollutants that have been dispersed across the areas. Specifically, the forward trajectories allow the path of the oil spill smoke plume to be tracked and utilized for mitigation purposes. This gives the EPA significantly improved monitoring abilities to issue air quality alerts or even early evacuation for coastal residents. The results of the trajectory analysis conducted showed that smoke plume trajectories for all oil burnings resulting from the Horizon oil spill correlated well with wind pattern data collected from NOAA and the National Geographics. In addition, the direction of the smoke plume was northeast and towards the inland populations. The created and analyzed forward trajectories were then passed on to one of the project partners, the Mobile Health Department DEVELOP team, for thorough analysis of the extent and impacts of the smoke plume on coastal residences.
Recommendations for Continued Air and Additional Water Quality Monitoring
At the conclusion of the project, EPA Region 6 will be given a methodology describing the use of various products to monitor air quality measurements in relation to the Deepwater Horizon oil spill. CALIPSO Level 2 Version 3.01 Aerosol Extinction data and the HYSPLIT model from NOAA will be among the products utilized. The methodology will serve to supplement sparse monitoring stations and to further the EPAÛªs understanding of air quality levels at sea. In addition, this methodology can be implemented as a feasible air quality monitoring tool in the occurrence of future oil spills.
Although this project took into account many issues besides air quality, future work in this area should also address the water quality issues arising from the spill and the long-term impacts on the coastal habitats in the Gulf of Mexico. Developing a methodology to easily measure water quality in reference to the oil spill by using NASA EOS products will not only be beneficial to the people of the Gulf of Mexico but also be a helpful way NASA DEVELOP can help project partners such as the EPA address public issues.
Dr. Richard Ferrare ÛÒ NASA Langley Research Center
Dr. Jim Szykman ÛÒ NASA Langley Research Center
Brian Getzewich – NASA Langley Research Center
For more information about the DEVELOP National Program and other student projects, please visit http://develop.larc.nasa.gov.