The photochemical evolution of the Sacramento urban plume: A guide to controlling ozone now and in a warmer climate. Idalia Magdalena Perez

ISBN: 9781109096248

Published:

NOOKstudy eTextbook

148 pages


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The photochemical evolution of the Sacramento urban plume: A guide to controlling ozone now and in a warmer climate.  by  Idalia Magdalena Perez

The photochemical evolution of the Sacramento urban plume: A guide to controlling ozone now and in a warmer climate. by Idalia Magdalena Perez
| NOOKstudy eTextbook | PDF, EPUB, FB2, DjVu, AUDIO, mp3, ZIP | 148 pages | ISBN: 9781109096248 | 8.56 Mb

High ozone and PM mixing ratios in the outflow from urban centers affect the health of millions of people in suburban communities as well as the health and productivity of natural and managed (e.g. farmland) ecosystems downwind.-In locations whereMoreHigh ozone and PM mixing ratios in the outflow from urban centers affect the health of millions of people in suburban communities as well as the health and productivity of natural and managed (e.g.

farmland) ecosystems downwind.-In locations where there are large biogenic VOCs sources downwind of urban centers, the outflow is characterized by a high VOC reactivity due to biogenic emissions and low NOx, due to the mixing in of cleaner background air into the urban plume. To date, relatively little effort has focused on this chemical regime with low NOx and high VOC reactivity, at least compared to extensive efforts on high NOx high VOC and low NOx, CH4, CO chemical regimes.

Understanding the chemistry at high VOC and low NOx is crucial in understanding air quality downwind of urban centers.-We use a Lagrangian model representing chemistry based on Master Chemical Mechanism v3.1, a chemical mechanism used widely in the atmospheric chemistry community, along with mixing and deposition to describe the chemical evolution of an urban plume.

The model is tested by comparison of its predictions with observations of NOy partitioning and O3 as a function of temperature and of day of week. This ensemble is used to assess the accuracy of the model and to identify some changes to the chemical mechanism that might improve the model-observation comparison. In particular, we focus on the fate of the products of the reaction between alkyl nitrates and OH and the effect of varying the branching ratio in the production of isoprene nitrates.

We then use the model to predict atmospheric response to control strategies for ozone reduction.-Comparisons of model predictions with observations indicate (1) the NO x lifetime in the base model plume is too long, (2) OH concentrations are underestimated in current models and (3) 60% reductions in NOx concentrations are needed to reduce O3 in the Mountain Counties air basin region, without negatively affecting the regions upwind. We show that current models do not reproduce the observed temperature dependence of NOy partitioning because they do not represent the temperature dependent increase in OH.

We also show that current models underestimate OH during weekends, a low NOx---high VOC reactivity regime.



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