"Ziman, Steve (SDZI)" <SDZI@chevrontexaco.com>
	04/05/02 02:18 PM
		 
		 To: Ellen Baldridge/RTP/USEPA/US@EPA
		 cc: John Silvasi/RTP/USEPA/US@EPA, Tom Helms/RTP/USEPA/US@EPA
		 Subject: Sensitivity of PM Nitrate paper_v0401.doc


Ellen

You asked to see this paper.  This is work that Christian Seigneur and 
Betty
Pun did using the Integrated Monitoring Program 1995-96 data to do some
initial box model calculations. It shows that nitrate formation is 
sensitive
to VOC.  It should be viewed as preliminary, with more work being done both
data analysis wise and (when we get there) modeling with a photochemical
grid model to check if this still holds.  

But the facinating thing is that if some of the urban areas are VOC limited
for Nitrate, then we have a conflict with the ozone strategy, as much of 
the
emphasis in the SJV is on NOx reduction-and that may not affect nitrate
reduction.  

I should note two other interesting things.  In the monitoring in the 
winter
of 95-96 when we had high nitrate concentrations (75 + ug/m3 for 24 hr
average), there was plenty of NO2 around to oxidize.  Much more than the
total of nitric acid and nitrate.  

Also, in 2000, we got the DOE Oil and Gas Partnership to fund Lawrence
Berkeley Labs to develop a semi-empirical indoor/outdoor PM 2.5 model. The
first phase of that ongoing work was to secure a typical home in Fresno and
fully instrument it, both indoors and outdoors. In order to avoid
interferences, the house was unoccupied, so the environment could be
controlled.  The house was a mile from the Fresno supersite. 

The most interesting finding so far is that, even on days with very high
nitrate, no nitrate was found indoors. This is due to the equilibrium
between nitrate and nitric acid and ammonia. With an indoor environment 
that
is > 60 F, somewhat dry, the nitrate immediately went to nitric acid, which
immediately deposited to surface. It was not found in the indoor atmosphere
to any extent. 

So, even if nitrate is in high concentration outdoors, it does not remain 
as
part of the particulate matter mix indoors, where people spend greater than
90% of their time. See the second attachment for this information.   

This is why we need to look at both ozone and PM together-BUT, and a huge
BUT-one needs more than routine monitoring data to do so.  Good aerometric
data is essential.

  
 
 Sensitivity of PM Nitrate paper_v0401.doc
 <<Sensitivity of PM Nitrate paper_v0401.doc>>