"Ziman, Steve (SDZI)" <SDZI@chevrontexaco.com>
	04/10/02 11:49 AM
		 
		 To: Ellen Baldridge/RTP/USEPA/US@EPA
		 cc: John Silvasi/RTP/USEPA/US@EPA, Scott Bohning/R9/USEPA/US@EPA, Carol 
Bohnenkamp/R9/USEPA/US@EPA, Brian Timin/RTP/USEPA/US@EPA, "'blanchard, 
charlie'" <cbenvair@pacbell.net>
		 Subject: RE: Information you requested

Ellen

You will note that I have cc'd Charlie Blanchard who actually has done this
analysis, and others for the Houston area, many sites in California, etc.
First, data for ozone and NOx (or NOy if actually available) is secured on
an hourly basis for the season.  The Smog Algorithm uses a set of algebraic
equations derived from a number of smog chamber simulations to determine 
the
extent of reaction on an hourly basis for each day for the hours of 7 AM
thru 6 PM on a monitor by monitor basis. These can be plotted in a circle
diagram with each hour indicative of the extent of reaction for that hour.
Additionally, the hour or hours with highest ozone can be indicated. Doing
this, one can determine how many hours a monitor is VOC limited, in the
transition zone or NOx limited. And one can see which limitation that
monitor is in when ozone peaks.  The data is not necessarily from either
PAMS or field studies, but can be taken from concurrent located ozone and
NOx monitors that are part of the SLAMS/NAMS network.  Charlie has shown
that one can use the NOx concentrations, and he has looked at how the 
extent
would vary if NOx were true NO and NO2 or if NOx is NOy.  What you have are
the analyses done for an entire ozone season for all monitors in the 
region,
done for five to 7 years.  Thus it is an aggregate analysis. The data can 
be
displayed on a monitor by monitor basis as well, as has been done in some 
of
the data analysis that Charlie has done for the San Joaquin Valley.  Carol
should have that, and can share it.  If not, I can forward it, but it is a
large file.  

As you may be aware, some of the original funding for development of the
Smog Algorithm came from EPA. API supplemented the funding, and a number of
peer review papers have been published on the methodology. In addition, 
this
type of analysis has been used to provide independent estimates of VOC or
NOx limitation for the Houston area, locations in California, and other
areas.  It is valuable to see if there are significant differences between
what it predicts, and what photochemical models predict for base case.  But
methods have uncertainties, so that neither is "absolutely correct". But it
serves as a good tool for looking at corroborative analysis for use in
weight of evidence.  Moreover, it allows one to look at all of the
non-modeled episodes during an ozone season, including those with different
meteorology. Per our discussion, this is valuable, as control of the worst
case, or for a 1-hr standard may be different than that for a lesser 
episode
or an 8-hour standard.  

Let me know if I answered your questions, and if there are other things you
need. 
Steve Ziman, Ph. D.

Here is a write-up that Charlie did as part of the SJV analysis

Sr. Staff Scientist
Air Issues and Technology
ChevronTexaco Energy Research and Technology Co
100 Chevron Way, Richmond, California 94802 sdzi@chevrontexaco.com phone
510-242-1530
fax       510-242-5577

-----Original Message-----
From: Baldridge.Ellen@epamail.epa.gov
[mailto:Baldridge.Ellen@epamail.epa.gov] 
Sent: Wednesday, April 10, 2002 4:16 AM
To: Ziman, Steve (SDZI)
Cc: 'SILVASI, oaqps'; Bohning.Scott@epamail.epa.gov;
Bohnenkamp.Carol@epamail.epa.gov; Timin.Brian@epamail.epa.gov
Subject: Re: Information you requested

I have a couple of questions:

How did you determine an hour was VOC or NOX limited?  Is this PAMS data or
special field study data?  The charts summarize the information over 5
years.  What do annual summaries look like?  Is this just the ozone season,
not the entire year?

Talk to you soon,

Ellen Baldridge
U.S. EPA, OAQPS, (D243-01)
RTP, NC   27711
Phone: 919-541-5684; Fax: 919-541-0044
baldridge.ellen@epa.gov

 

                      "Ziman, Steve

                      (SDZI)"                  To:       John
Silvasi/RTP/USEPA/US@EPA, Ellen                            
                      <SDZI@chevrontexa         Baldridge/RTP/USEPA/US@EPA,
Tom Helms/RTP/USEPA/US@EPA                   
                      co.com>                  cc:

                                               Subject:  Information you
requested                                       
                      04/04/2002 02:40

                      PM

 

 

Tom, John and Ellen

Per our discussion yesterday, here is the graph I showed you. It uses five
years of data, from 1994 on. The second document relates to the issue of
length of episode and movement towards more NOx limitation. This is a draft
which will be included in the final CCOS historic data
analysis, and was done for the Central California area.   I will forward
some other things to you for information, as I get them.

<<Extfreq1.doc>> <<SJVEpisode extent.pdf>>
Steve Ziman, Ph. D.

Sr. Staff Scientist
Air Issues and Technology
ChevronTexaco Energy Research and Technology Co
100 Chevron Way, Richmond, California 94802 sdzi@chevrontexaco.com phone
510-242-1530
fax       510-242-5577 (See attached file: Extfreq1.doc)(See attached
file: SJVEpisode extent.pdf)