SECA Program - Ambient Measurement
This page last reviewed April 22, 2010
CARB funded Professor Mark
Thiemens of the University of California at San
Diego in a pilot study to determine the utility of multi-stable isotope
ratio measurements of aerosol sulfate and nitrate to identify the
impact of ship emissions in the San Diego region. All sulfur, nitrogen,
and oxygen isotope ratios will be determined for aerosol sulfate and
nitrate. The proposed technique has the advantage of not only
specificity, but also sensitivity. If the pilot study is successful,
then additional funds will be sought to analyze high-volume PM10
samples collected from other areas of North America.
CARB amended the project by adding aerosol time-of-flight mass spectrometer (ATOFMS) measurements to help interpret the 24-hour average isotopic measurements since ATOFMS provides size-resolved information in real time.
This project will conduct ambient monitoring of CO and SO2 at the Bodega Bay Marine Lab on the Northern California coast (north of San Francisco) to estimate regional ship emissions from this currently unregulated source of pollutants. By scaling the estimated emissions ratio of SO2 to NOx from the marine combustion sources, the principle investigator expects to also be able to provide a good estimate of the corresponding regional NOx emissions. In this study, the researchers will measure individual ship plumes intercepting the shoreline, survey the local fishing community to ascertain engine characteristics and offshore traffic habits (small GPS tracking units will provide the locations and speed of the volunteer ships on their expeditions so that the orientation and speed of the tracks upwind of the shoreline sensors will be known for a subsample of the data), and develop an inventory of shipping emissions in the area. The researchers will compare their statistics of regional emissions based on local observations of ships, activities, and ambient measurements to the most current and thorough database of Dr. James Corbett (University of Delaware) to check the agreement between both techniques (i.e., inference from direct plume observations versus bottom-up estimates). The improved understanding of the engine make-up of the local fleet and the relative S emissions can also then be applied to the past CO measurements at this shoreline site to extend the temporal results of this study to a seasonal, annual, and interannual scope.