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Mechanism SAPRC

Error and bias for model predictions of A([03]-[N0]) using the SAPRC-99 mechanism. Bias is (calculated - experimental) / ealeulated. Error is the absolute value of the bias. [Pg.38]

The ability of the SAPRC-99 mechanism to simulate the total amount of NO oxidized and O3 formed in the experiments, measured by ([03]finai-[N0]fmai) - ([03]initiai-[NO]initiai) or A([03]-[N0]), is summarized for the various types of experiments on Table 2 and shown for the individual runs on Figure 5. This gives an indication of the biases and run-to-run variability of the mechanism in simulating ozone formation. Note that in experiments with excess NO the processes responsible for O3 formation are manifested by consumption of NO, so simulations of A([03]-[N0]) provides a test of model simulations of these processes even for experiments where O3 is not formed. [Pg.38]

Fits of experimental A([03]-[NO]) measurements to SAPRC-99 model calculations for the initial chamber and mechanism evaluation experiments. [Pg.39]

As indicated on Table 2, the initial evaluation experiments included nms with NOx levels as low as 2-5 ppb, which is considerably lower than in experiments used previously for mechanism evaluation. Most of the experiments used in die previous SAPRC-99 mechanism evaluation had NOx levels greater than 50 ppb, and even die low NOx TVA and CSIRO experiments had NOx levels of —20 ppb or greater, except for a few characterization nms (Carter, 2004a, and references therein). However, there is no indication in any difference in model performance in simulating the results of these very low NOx experiments, compared to those with the higher NOx levels more representative of diose used in the previous evaluation. [Pg.39]

Carter, W. P. L. Documentation of the SAPRC-99 chemical mechanism for VOC reactivity assessment. Report to the California Air Resources Board, Contracts 92-329 and 95-308, May 8 (2000). Available at http //www.certucr.edU/ carter/absts.htm saprc99. [Pg.41]

Carter, W. P. L. Evaluation of the SAPRC-99 Chemical Mechanism using new environmental chamber data. Presented at the Qordon Conference on Atmospheric Chemistry, Big Sky Resort, Montana, September 7-12, 2003 (available from http //pah.cert.ucr.edu/ carter/bycarter.htm)... [Pg.64]

Environmental chambers, Atmospheric chemical mechanisms, Ozone, Aromatic Hydrocarbons, Petroleum Distillates, Coatings VOCs SAPRC-99 Mechanism... [Pg.231]

The ability of the SAPRC-99 mechanism to simulate ozone formation in representative MIR and MOIR/2 base ease experiments is shown on Figure 2. It can be seen that good reproducibility in ozone formation is observed in the replicate experiments, but that the model consistently under prediets O3 formation in the MIR experiments, though it gives much better predictions of ozone in the experiment at the higher ROG/NOx ratio. This tendency to under... [Pg.233]

Figure 3. Plots of die bias for the SAPRC-99 mechanism to vmder predict NO oxidation and O3 formation against normalized ROG/NOx ratios for ambient surrogate -NOx experiments in three environmental chambers. Figure 3. Plots of die bias for the SAPRC-99 mechanism to vmder predict NO oxidation and O3 formation against normalized ROG/NOx ratios for ambient surrogate -NOx experiments in three environmental chambers.
Figure 4. Plots of the mechanism under prediction bias for model simulations UCR EPA ambient surrogate - NOx experiments against normalized ROG/NOx ratios for the SAPRC-99 and Carbon Bond mechanisms. The SAPRC-99 calculations show effects of varying the MONO offgasing chamber effect parameters and using a lower OH + NO2 rate constant. Figure 4. Plots of the mechanism under prediction bias for model simulations UCR EPA ambient surrogate - NOx experiments against normalized ROG/NOx ratios for the SAPRC-99 and Carbon Bond mechanisms. The SAPRC-99 calculations show effects of varying the MONO offgasing chamber effect parameters and using a lower OH + NO2 rate constant.
The results of the toluene - NOx and m-xylene - NOx experiments in the UCR EPA were reasonably consistent with the predictions of the current SAPRC-99 mechanism, though the mechanism had a slight bias towards over predicting O3 in the experiments (see Carter, 2004a for a smnmary of the fits to total NO oxidation and O3 formation in the experiments). [Pg.236]

Examples of experimental and calculated ozone in these runs are shown in Figure 5, where the open squares are the experimental data for representative aromatics - NOx experiments, and the dotted lines are the model simulations of those runs. A reasonably good fit of the model to these experiments is expeeted beeause the parameters in the mechanisms for those compounds were adjusted to optimize model simulations of such experiments. However, the NOx levels in these experiments were eonsiderably lower than those in the runs used to develop the SAPRC-99 meehanisms, and there was a concern that the parameterization may not extrapolate to lower NOx levels. Apparently the parameterization employed is no less applicable for NOx levels as low as 5 ppb than it is for the higher NOx levels in the experiments used in the mechanism development. [Pg.237]

Effects of adjustments to the SAPRC-99 toluene photooxidation mechanism on simulations of representative toluene experiments experiments. [Pg.238]

Thus the new data suggest that there is a fundamental problem with the formulation of the eurrent aromatics mechanism, and more extensive modifications are required in order for model simulations to be consistent with the available data. We have been funded by the California Air Resomces Board to update the SAPRC mechanism, and developing an improved aromatics mechanism is a priority in this project. Work on a new, more explicit mechanism that incorporates more recent laboratory data such as that summarized by Calvert et al (2004) is now underway, but progress is slow. Presently, we are encountering problems similar to those discussed by Pilling (2004) for the MCM. It is likely that there are reactions occurring that none of the mechanisms are adequately representing. [Pg.239]

Although the UCR EPA chamber has only been in operation for a relatively short time, it has already obtained usefiil information concerning the performance of current mechanism in predicting the effects of VOCs and NOx on ozone formation. As discussed here and also in our companion paper (Carter, 2004a), the SAPRC-99 mechanism predicts O3 formation reasonably well in low NOx experiments, and in ambient simulation experiments at the high ROG/NOx levels where maximum ozone formation potentials are achieved. However, die new data indicate problems with the mechanisms that were not previously realized. The SAPRC-99 mechanism consistently under predicts O3 formation in the lower ROG/NOx experiments where O3 formation is most sensitive to VOCs, and the problem is even worse for CB4. Other experiments indicate that there are problems with the formulation wifli die current aromatics photooxidation mechanisms. It is possible that the problems with the under prediction at low ROG/NOx ratios may be caused by problems with the aromatics mechanisms. Experimental and mechanism development work to investigate and hopefully resolve these problems is underway... [Pg.239]

There are a large number of condensed chemical reaction mechanisms to describe and represent atmospheric chemical transformations involving air pollutants. On the contrary only a very limited number of mechanisms exist with a detailed description of chemical transformation processes for primary and secondary atmospheric species. The Master Chemical Mechanism (MCM) (Jenkin et al, 1997) and SAPRC (Carter and Liumann, 1991) are two well known examples. [Pg.241]

This work therefore develops a base for the evaluation of degradation mechanism for a number of VOC represented in MCM v3, using the SAPRC environmental chamber datasets. [Pg.242]

Data from the following environmental chambers were used in the present evaluation Indoor Teflon Chamber 1 (ITC) Indoor Teflon Chamber 2 (ETC) Dividable Teflon Chamber (DTC) Xenon Arc Teflon Chamber (XTC) and CE-CERT Xenon Arc Teflon Chamber (CTC). The available datasets from these chambers were used previously in the development and evaluation of the SAPRC-99 mechanism (Carter, 2000). [Pg.242]

A database for mechanism evaluation is therefore not complete without reeommendations for appropriate inputs to auxiliary mechanisms. Such chamber effects models have aheady been developed for the SAPRC chambers as part of the process of evaluating SAPRC-99 and related mechanisms (e.g. Carter, 2000), and these form the basis of the auxiliary mechanisms applied in the present study. [Pg.243]

Initial simulations were carried out to compare the SAPRC-99 and MCM v3 butane mechanisms for the conditions of the butane-NOx experiments, using the auxiliary mechanism parameters defined by Carter, (2000), and a consistent set of inorganic reaction... [Pg.244]

As with previous assessments (e.g. Carter, 2000), the quantity D(Oj-NO) was used as the main criterion of model performance. This quantity is defined as D(03-NO)t = [Oajt -[NO]t - ([Osjo - PMO]o), where [03]o [NO]o, and [Osh, [NO]t are the concentrations of O3 and NO at the beginning of the run, and at time t , respectively. As described in detail previously (e.g., Carter and Lurmann, 1991, Carter et al, 1995a, Carter, 2000), D(Os-NO) is an indicator of the ability of the mechanism to simulate the chemical processes fliat cause O3 formation, giving a useful measure, even when O3 is suppressed by the presence of excess NO. In addition, use of this measure allows a direct comparison wifli die SAPRC-99 published results. The precursor decay rate and formation of die carbonyl products and PAN were also used as criteria of model praformance. [Pg.245]

Throughout the study, the performance of MCM v3 and the refined mechanism (denoted MCM v3a) was simultaneously compared with that of the SAPRC-99 mechanism, which was developed and optimized in conjunction with the chamber datasets (Carter, 2000). The performance of MCM v3a was found to be very similar to that of SAPRC-99. [Pg.251]

Carter W. P. L. Documentation of the SAPRC-99 Chemical Mechanism for VOC reactivity Assessment, Final Report to California Air Resources Board Contract 92-329 and Contract 95-308, Air Pollution Research Center and College of Engineering Center for Environmental Research and Technology University of California Riverside, California (2000). [Pg.252]

Carter, W.P.L. (2000), Development and evaluation of the SAPRC-99 chemical mechanism. United States Environmental Protection Agency, Research and Development, (EPA/6(X)/R-00/076, Proceedings Sixth US/Germany Workshop on Ozone/Fine Particle Science, 1999), 19-41. [Pg.1407]


See other pages where Mechanism SAPRC is mentioned: [Pg.33]    [Pg.50]    [Pg.231]    [Pg.232]    [Pg.232]    [Pg.232]    [Pg.234]    [Pg.234]    [Pg.236]    [Pg.236]    [Pg.242]    [Pg.245]    [Pg.1236]    [Pg.1366]    [Pg.1367]   
See also in sourсe #XX -- [ Pg.37 , Pg.99 , Pg.231 , Pg.242 ]




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