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Effects of the 1990 Clean Air Act amendments on distributions of visual impairment

Description: The Acid Rain Provisions (Title IV) of the 1990 Clean Air Act Amendments (1990 CAAA) focus on emission policies designed to reduce the amount of deposition of acidifying pollutants, particularly in the Northeast. The primary strategy is a significant reduction in SO{sub 2} emissions, with lesser reductions scheduled for NO{sub {times}} emissions. However, lessening of acid deposition is not the only important benefit of the emission control strategy. Decreasing SO{sup {minus}} and NO {sup {minus}} emissions will decrease atmospheric concentrations of sulfate and nitrate particles, which account for much of the visibility reduction associated with regional haze. Although one can get a qualitative sense of how visibility might improve by examining historical large-scale trends in regional emission totals and regional visibility, quantification of the expected improvement requires model simulations. One must model the spatial and temporal patterns of emissions reductions; the relevant pollutant transport, transformation, and removal processes in the atmosphere; and the changes in particulate loading. For this initial examination of the visibility improvement at Shenandoah National Park associated the the Phase I and Phase II SO{sub 2} emission reductions, we have linked emission trend projections taken from ongoing analysis of the 1990 CAAA at Argonne National Laboratory, regional transport modeling with the Advanced Statistical Trajectory Regional Air Pollution (ASTRAP) model and visual impairment modeling with the Visibility Assessment Scoping Model (VASM).
Date: February 1, 1996
Creator: Shannon, J.D.; Camp, J. & Trexler, E.C. Jr.
Partner: UNT Libraries Government Documents Department

Visibility assessment : Monte Carlo characterization of temporal variability.

Description: Current techniques for assessing the benefits of certain anthropogenic emission reductions are largely influenced by limitations in emissions data and atmospheric modeling capability and by the highly variant nature of meteorology. These data and modeling limitations are likely to continue for the foreseeable future, during which time important strategic decisions need to be made. Statistical atmospheric quality data and apportionment techniques are used in Monte-Carlo models to offset serious shortfalls in emissions, entrainment, topography, statistical meteorology data and atmospheric modeling. This paper describes the evolution of Department of Energy (DOE) Monte-Carlo based assessment models and the development of statistical inputs. A companion paper describes techniques which are used to develop the apportionment factors used in the assessment models.
Date: December 12, 1997
Creator: Laulainen, N.; Shannon, J. & Trexler, E. C., Jr.
Partner: UNT Libraries Government Documents Department

Assessing the potential visibility benefits of Clean Air Act Title IV emission reductions

Description: Assessments are made of the benefits of the 1990 Clean Air Act Title IV (COVE), Phase 2, SO2 and NOX reduction provisions, to the visibility in typical eastern and western Class 1 areas. Probable bands of visibility impairment distribution curves are developed for Shenandoah National Park, Smoky Mountain National Park and the Grand Canyon National Park, based on the existing emissions, ``Base Case``, and for the COVE emission reductions, ``CAAA Case``. Emission projections for 2010 are developed with improved versions of the National Acid Precipitation Assessment Program emission projection models. Source-receptor transfer matrices created with the Advanced Statistical Trajectory Regional Air Pollution (ASTRAP) model are used with existing emission inventories and with the emission projections to calculate atmospheric concentrations of sulfate and nitrate at the receptors of interest for existing and projected emission scenarios. The Visibility Assessment Scoping Model (VASM) is then used to develop distributions of visibility impairment. VASM combines statistics of observed concentrations of particulate species and relative humidity with ASTRAP calculations of the relative changes in atmospheric sulfate and nitrate particulate concentrations in a Monte Carlo approach to produce expected distributions of hourly particulate concentrations and RH. Light extinction relationships developed in theoretical and field studies are then used to calculate the resulting distribution of visibility impairment. Successive Monte Carlo studies are carried out to develop sets of visibility impairment distributions with and without the COVE emission reductions to gain insight into the detectability of expected visibility improvements.
Date: June 1, 1995
Creator: Trexler, E.C. Jr. & Shannon, J.D.
Partner: UNT Libraries Government Documents Department

Climatological variability in regional air pollution

Description: Although some air pollution modeling studies examine events that have already occurred (e.g., the Chernobyl plume) with relevant meteorological conditions largely known, most pollution modeling studies address expected or potential scenarios for the future. Future meteorological conditions, the major pollutant forcing function other than emissions, are inherently uncertain although much relevant information is contained in past observational data. For convenience in our discussions of regional pollutant variability unrelated to emission changes, we define meteorological variability as short-term (within-season) pollutant variability and climatological variability as year-to-year changes in seasonal averages and accumulations of pollutant variables. In observations and in some of our simulations the effects are confounded because for seasons of two different years both the mean and the within-season character of a pollutant variable may change. Effects of climatological and meteorological variability on means and distributions of air pollution parameters, particularly those related to regional visibility, are illustrated. Over periods of up to a decade climatological variability may mask or overstate improvements resulting from emission controls. The importance of including climatological uncertainties in assessing potential policies, particularly when based partly on calculated source-receptor relationships, is highlighted.
Date: June 1, 1995
Creator: Shannon, J.D. & Trexler, E.C. Jr.
Partner: UNT Libraries Government Documents Department

Visibility assessment : coping with incomplete emissions and modeling.

Description: The availability of complete emissions and entrainment data, topographic data and statistical meteorology data, and the modeling to account for all aerosol constituents presently found in our atmospheres, is not likely to improve substantially in the foreseeable future. This inability to model all of the transformation and transport processes which result in visibility-impairing aerosol species arriving at a point of interest, does not necessarily prevent our assessment of the benefits of reducing emissions from sources that can be modeled. We must, however, have an adequate statistical record of the concentrations of these materials and we must have a reliable means to apportion the concentration into controllable (i.e., those we can quantify and model) and uncontrollable fractions. Statistical concentration data, for remote scenic regions, are available for relevant aerosol species from the IMPROVE Network, for years beginning in 1988. A comparable network is unfortunately not available for urban areas. Here we describe the evolution of our source apportionment assumptions for two remote sites of much current interest, Grand Canyon and Shenandoah National Parks. Ingenuity and in some cases additional field investigations are necessary to improve such apportionment assumptions. To that end we briefly summarize promising approaches, such as receptor analysis and characterization of the particulate loading of on-shore flows, and current DOE research relevant to the issue.
Date: December 12, 1997
Creator: Laulainen, N.; Shannon, J. & Trexler, E. C., Jr.
Partner: UNT Libraries Government Documents Department