[SIO GP Seminars] Earth Weekly Seminar--TODAY Dr. Carol Kendall

[Cassandra Gaston]

Monday May 5, 2008
 The Earth Weekly Seminar presents Dr. Carol Kendall from the USGS at
 Menlo Park.  Here is
  the title of her talk and her abstract:

  "Tracing Anthropogenic Sources of Nitrogen  in Rain Using Isotopes"

 "Global emissions of NOx have increased dramatically during the past
 150 years. Contemporary global inputs of NOx are dominated by fossil
 fuel combustion from both power plants and vehicles, and far exceed
 natural NOx sources such as lightning, biogenic soil processes, and
 wildfires. Atmospheric nitrogen deposition can alter the structure and
 function of terrestrial ecosystems because nitrogen is often a primary
 limiting nutrient on overall productivity. These alterations can drive
 losses of biodiversity, as species adapted to high-N conditions (e.g.,
 invasive annual grasses) out-compete species adapted to more pristine
 conditions. For example, high levels of NOx deposition near major
 highways in northern CA have been linked to the decline of the
 endangered checkerspot butterfly.  However, quantifying NOx
 contributions from different sources to any given location -- and
 distinguishing this nitrate from natural, agricultural, and sewage
 sources of nitrate -- remains a difficult challenge, despite the need
 for this information to develop sound regulatory and mitigation
 strategies.

 As part of a national-scale investigation of the usefulness of nitrate
 isotopes as tracers of NOx sources to terrestrial and coastal
 ecosystems, we have analyzed the 15N and 18O of nitrate in
 composited bimonthly wet precipitation samples from ~150 National
 Atmospheric Deposition Program (NADP) sites, using archived samples
 from 2000.  Nitrate samples from a subset of NADP sites in the NE have
 also been analyzed for 17O.  These data show that spatial and
 temporal variations in δ15N are strongly correlated with NOx emissions
 from power plant sources, and hence that δ15N can be a strong
 complement to existing tools for assessing relationships between NO3-
 deposition and regional emission inventories, and for evaluating
 progress towards NOx reduction goals required by recent EPA
 regulations. This talk will present an overview of the problem and
 show examples of how isotopes can help determine the relative
 contributions of nitrate derived from natural sources, vehicle
 exhaust, and power plant emissions to airsheds, watersheds, and
 groundwater."


 Please join us at 3pm Hubbs Hall 4500 for snacks followed by Dr. Kendall's
  talk at 3:15pm at the same location.  We can't wait to see you there.

  Cheers,

  Cassie

 --
 Cassandra Gaston
 PhD Student
 Scripps Institution of Oceanography
 Prather Lab
 858-822-5745
 http://atofms.ucsd.edu



-- 
Cassandra Gaston
PhD Student
Scripps Institution of Oceanography
Prather Lab
858-822-5745
http://atofms.ucsd.edu