| Popis: |
This paper, the first of a two-part series, presents a new semi-empirical methodology that allows estimation of the percentage improvements in annual average visual range that can be expected from a percentage reduction of SO 2 emissions. This methodology relies on an intuitive mathematical approach that combines four separate effects: (1) the transport of atmospheric sulfur; (2) the possible nonlinearity of the SO 2 -to-SO 2− 4 chemical transformation; (3) the fraction of sulfates in fine particulate matter, taking into account the role of the water adsorbed by the fine particles; and (4) the fraction of light extinction that is due to fine particles. By looking at these four effects, within the context of each of the various meteorological regimes that have distinct influences on visual air quality, the problem can be broken down into manageable components that model a portion of the source-receptor interaction. If the necessary arrays that specify these four terms, which are expressed in fractional form, can be quantified for each region and meteorological classification, then the methodology can estimate the average ‘efficiency’ of reductions in SO 2 emissions for producing improvements in long-term regional averages of visual range. Then, annual averages can be computed if the relative frequency of occurrence of each meteorological regime in each region is known. Moreover, the method estimates the uncertainty in the calculated percentage improvements in visual range, based on the uncertainties in input data. The second paper in this series will present an example of the application of this methodology to the eastern U.S., where the effect of SO 2 emissions on visibility has received significant attention. |
