"Ziman, Steve (SDZI)" 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'" 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 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. <> <> 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)