Control strategies for urban ozone traditionally have been based on mass reductions in volatile organic compounds (VOCs). Studies show, however, that some organic gas species (such as alkanes and alcohols) form an order of magnitude less ozone than equal mass emissions of others (such as alkenes and aldehydes). Chemically detailed photochemical models are used to assess uncertainty and variability in reactivity quantification. VOC control strategies based on relative reactivity appear to be robust with respect to nationwide variations in environmental conditions and uncertainties in the atmospheric chemistry. Control of selective organic gas species on the basis of reactivity can offer cost savings over traditional strategies.

This study applied Monte Carlo analysis with Latin hypercube sampling to evaluate the effects of uncertainty in air parcel trajectory paths, emissions, rate constants, deposition affinities, mixing heights, and atmospheric stability on predictions from a vertically resolved photochemical trajectory model. Uncertainties in concentrations of ozone and other secondary compounds and in predicted changes due to 25% reductions in motor vehicle nonmethane organic compound (NMOC) and nitrogen oxide (NO x ) emissions were examined. Surface wind measurements were interpolated over the modeling domain, and uncertainties were quantified using data withholding. The resulting wind fields and uncertainties were used to generate ensembles of trajectories ending at four Southern California air quality monitoring sites. A motor vehicle emissions inventory and associated uncertainties were derived from remote sensing and fuel sales data. Uncertainties in chemical rate parameters were obtained from expert reviews. Estimated uncertainties in O 3 range across the four sites from 24% to 57% (1 standard deviation (1σ) relative to the mean). Seven variables contribute almost 80% of this uncertainty. Reductions in motor vehicle NMOC reduce O 3 from 10 ( 10% (1σ) to 28 ( 10%. With reductions in motor vehicle (NO x ) emissions, the change in O 3 ranges from an increase of 14 ( 14% to a decrease of 6.6 ( 6.2%.

No abstract

The regional nature of several important air pollutants, which include acids, ozone, particulate matter, mercury, and persistent organics (POPs), is widely recognized by researchers and decision makers. Such pollutants are transported regionally over scales from about 100 to a few 1000s of kilometers, large enough to cross state, provincial, national, and even continental boundaries. Managing these regional pollutants requires overcoming political, economic, and cultural differences to establish cooperation between multiple jurisdictions, and it requires recognition of the linkages between pollutants and of impacts at different geographic scales. Here, regional dynamics of the pollutants are discussed, addressing them individually and as a tightly linked physical and chemical system. Collaborative efforts to characterize and manage regional pollution are presented, along with potential directions for future efforts.

No abstract