Ozone policy
ozone remains one of the most perplexing air pollutants posing critical threat to human health. While stratospheric ozone 10 to 50 km above the earth's surface keeps declining, aggravating the problem of global warming, concentration of ozone in the troposphere upto 10 km above the earth's surface, also known as ground level ozone, poses a deadly threat to the respiratory system of humans. This highly authoritative book, which comes from some of the best minds working on this issue, deals with control strategies for ground level ozone, which has emerged as one of the most serious air pollution problems.
A product of research by the Committee on Tropospheric Ozone Formation and Measurement (ctofm) of the us -based National Research Council (nrc), this book comes as a comprehensive guide in framing policy to control ground level ozone. The ctofm was established in 1989 to evaluate scientific information on tropospheric formation of ozone. The product is the book under review a commendable job.
Neatly organised into fourteen chapters, the book begins by stating the problems of ozone and its trends in the us.
The book analyses the air quality data on ozone in the us and discusses the problem of non-attainment extensively. The non-attainment problem continues even today. As ozone is formed in the atmosphere by the reaction of different pollutants like reactive hydrocarbons and oxides of nitrogen (nox) and not emitted directly from any source, it has been difficult to control its levels in the air. Ozone formation has a very complex relationship with the meteorological conditions. It depends to a large extent on factors like wind speeds, mixing heights and temperature. The book deals with this in minute details.
The authors take up a number of other issues for discussion all of them backed with excellent documentation and analysis. Monitoring is definitely the first step, gradually moving on to issues of preparing inventories for emissions and air quality modelling.
They present a critique of the process of emission inventorisation followed by the usepa and point out its flaws. Inventories are usually based on a number of assumptions, which may turn out to be erroneous or inadequate. Therefore, where preparing inventories for ozone precursors like volatile organic compounds (vocs) and nox is concerned, independent tests, including monitoring of ambient vocs, should be used to assess whether emissions are indeed as they are represented by inventories.
The authors also point out that it is of utmost importance for the monitoring programmes not only to verify estimates of voc and nox emissions, but also to adequately explain the atmospheric chemistry and to assess the contributions of different sources to the ambient concentrations of these compounds.
Equally important is the issue of developing air quality models to estimate the effect of emissions control measures on ambient ozone concentrations. However, it is necessary to be careful about the uncertainties involved in the data inputs required to develop such a model, like the meteorological factors and ozone formation mechanism.
The book moves on to address the issue of prioritising control of ozone precursors. It explains that air quality models in various cities in the us show that the relative effectiveness of reducing voc and nox in ozone control varies widely. While modelling studies show that ozone should decrease in response to nox reductions, some studies also show that ozone concentrations can increase in the near field in response to nox reductions, but decrease in the far field. Thus the issue of nox control on ozone concentrations emerge as quite complex.
Since the greatest share of vocs and nox emission comes from use of fossil fuels in the transport sector, the authors deal with this issue in good detail. The book considers several options like natural gas, methanol, ethanol, hydrogen, electricity and reformulated gasoline as alternative fuels.
Vehicles that run on electricity or on hydrogen in fuel cells would emit virtually no precursors of ozone, but the production of electricity or hydrogen can contribute to ozone formation at the generation level. The book points out that the use of natural gas as an automotive fuel can reduce ozone formation compared with conventional gasoline vehicles.
All these issues are extremely important particularly in the context of developing countries like India, where air quality planning and management is still in a juvenile stage. That the usepa came forward to co-sponsor the research in 1989 even before the Clean Air Act Amendments of 1990 mandated it, with the support of other institutions like the us Department of Energy and the American Petroleum Institute is a lesson in progressive planning in framing air quality management policies.
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