Paulette Middleton

Judgments of photographs vs. field observations in studies of perception and judgment of the visual environment

Abstract The use of photographs as surrogates for field observations is common in studies of perception and judgment of the visual environment despite theoretically important differences between photographs and three-dimensional scenes. The few available empirical studies of the validity of photographs as representations of the visual environment have methodological weaknesses. We describe a method for investigating the representativeness of photographs that differs from previous approaches in three important respects. First, individual subjects rather than group averages are analyzed. Second, multiple judgments are obtained so that the relations among judgments of photographs can be compared with the environment. Third, a ‘lens model equation’ analysis is used to examine relations among systematic components of variation in judgments. An illustrative study of visual air quality judgments is presented. It was found that, in the case of judgments of visual air quality, photographs provide a good representation of the visual environment.

Theoretical estimates of the relative importance of various urban sulfate aerosol production mechanisms

Abstract Theoretical estimates have been made to demonstrate the relative importance of various pathways for the production of sulfate aerosols in an urban atmosphere, away from the stationary sources under different atmospheric conditions. We have incorporated photochemical reactions, vapor condensation and catalytic and non-catalytic oxidation on a wetted aerosol surface into our theoretical consideration. From our calculations, it is found that under daytime conditions, with photochemical reactions, sulfuric acid vapor condensation and liquid phase oxidation by H 2 O 2 can be the dominant sulfate aerosol production mechanisms. Gas to particle conversion is expected to be an even more important pathway to sulfate aerosol formation under daytime conditions since reactions involving radical clusters such as HSO 3 · H 2 O, HSO 5 · H 2 O, and SO 3 · H 2 O are approximated by H 2 SO 4 condensation in our estimates. Under night-time conditions, without photochemical reactions, sulfate aerosol production in general is lower than under daytime conditions and catalytic and non-catalytic oxidation mechanisms on the wetted aerosols become important pathways for SO 2 to sulfate conversion.

Analysis of emission databases for regional models

Abstract General procedures for adapting emission inventories to regional models and for studying the impact of differences in inventories on model predictions are outlined. To illustrate the methods, analysis of two inventories which are still being validated is presented. The inventories together satisfy current requirements for the NCAR regional acid deposition model (RADM). These include anthropogenic emissions of SO 2 , sulfate aerosol, NO, NO 2 , NH 3 and volatile organic compounds (VOC) in 10 reactivity classes, from United States and Canadian point and area sources on 80-km grid resolutions, for weekend and weekday seasonally representative days on a diurnal basis during the 1980–1982 period. Application of checking procedures, designed by our group to screen for subtle anomalies not identified at previous stages of quality assurance employed by the inventory developers, resulted in adjustments primarily to VOC emissions. Comparisons of the modified inventories, which provide an indication of uncertainties in emissions due to variations in inventory development procedures, revealed differences in the eastern United States total daily emissions to be at most on the order of 5 % for SO x , and NO x , 20% for VOC and 85% for NH 3 . Studies of the impact of inventory differences on predictions of RADM were conducted for the 22–24 April 1981 period, which was monitored as part of the Oxidation and Scavenging Characteristics of April Rains program. Event total wet sulfate deposition differed by 10% or less while midday O 3 concentrations differed by 1% or less for individual grids over the modeling domain.

URBAN VISUAL AIR QUALITY JUDGMENTS: RELIABILITY AND VALIDITY

A procedure based on judgments of human observers for measuring visual air quality in urban areas is described, and its reliability and validity are examined using the results of several studies conducted in a metropolitan area. It is concluded that the procedure provides a measure that is sufficiently reliable and valid to warrant its use in studies of the causes and consequences of changes in visual air quality. Substantial agreement was found among individuals with regard to judgments of visual air quality, but the possibility of differences between experienced and inexperienced observers requires further investigation. The paper provides an example of methods that can be used, and issues that should be addressed, in the development of perceived environmental quality indices.

On the use of human judgment and physical/chemical measurements in visual air quality management

Application of existing human judgment and physical/chemical measurement techniques in developing visual air quality management programs is discussed. The measurement techniques are reviewed in terms of their abilities to provide information on several important management concerns: 1) public recognition of the problem, 2) public acceptability of different levels of visual air quality, 3) the relationship between emissions and visual air quality, and 4) trends in visual air quality. Major characteristics of measures affecting these abilities include: 1) how directly each measures visual impact, 2) the cost of achieving a desired level of reliability, and 3) the availability of a historical data base. From this review it is concluded that different measurement techniques are needed to address different management concerns. Ratings of visual air quality made by observers in the field provide the most direct measurement of human responses to the visual environment. Surveys and tradeoff analyses are useful fo...

Physical and chemical indicators of urban visual air quality judgments

Abstract Key issues in the selection of physical/chemical measures of atmospheric properties as indicators of judgments of visual air quality are addressed. The relations between measures and judgments made over a variety of times, observation locations and atmospheric conditions are examined experimentally. Light scattering measured throughout the day at a site characterized by high aerosol concentrations was the single measure most strongly related to judgments of visual air quality. A combination of measures taken at a single site and/or other sites are somewhat better indicators of visual air quality than light scattering alone. Light extinction measured by a telephotometer is strongly related to midday visual air quality. The 4-h averaged fine particle sulfur and 12-h averaged fine particle S, sulfate, nitrate and ammonium are all strongly related to the corresponding mean visual air quality. Although these midday hourly and 4-h and 12-h average measures may be used to indicate trends in visual air quality, hourly measures taken throughout the day are required for monitoring diurnal patterns or worst case visual air quality. The application of the method and findings to understanding visual air quality in other urban areas is discussed.

Modeling human judgments of urban visual air quality

Abstract The overall approach to establishing a complete predictive model link between pollutant emissions and human judgments of urban visual air quality (UVAQ) is presented. The field study design and data analysis procedures developed for analyzing the human components of visual air quality assessment are outlined. The air quality simulation model which relates pollutant emissions to human judgments of visual cues which comprise visual air quality judgments is described. Measured and modeled cues are compared for five typical visual air quality days in the winter of 1981 for Denver, Colorado. The comparisons suggest that the perceptual cue model, based on dispersion and radiative transfer theory, does not adequately predict human judgments of UVAQ cues. Analysis of the limits of predictability of the human judgments and the predictive capability of the model components indicates that the greatest improvements toward achieving a predictive UVAQ model lie in a reformulation of the theoretical descriptions of visual cues.

Acid rain and drinking water degradation.

Acid deposition-induced drinking water degradation is discussed with respect to the geographical extent of and the potential for dealing with possibly adverse human health impacts. Qualitative evidence from the northeastern United States and Sweden strongly suggests the existence of a linkage between these two environmental concerns. It is argued that water treatment and reduction of acid rain as solutions to the problem of water toxicity need closer evaluation. More research into the causal link is warranted since the addition of human health impacts to acid rains environmental insults could have a significant bearing on discussions relating to acid rain controls.

A Simple Model for Urban Ozone Impact Predictions

A simple urban ozone model for air quality management analysis is presented. The model is evaluated by comparing predicted and observed patterns in monthly average ozone maxima and dosages for two distinct urban areas and by comparing the simple model results for altered sources to the results of the Empirical Kinetic Modeling Approach (EKMA) and the Graedel complete urban air chemistry model. From these comparisons it is concluded that the simple ozone model can be used for accurate yet efficient qualitative analysis of the influence of various air quality policy options on future ozone impacts.

A re-examination of atmospheric sulfuric acid aerosol formation and growth

Abstract Atmospheric sulfuric acid aerosol formation and growth is re-examined using the Middleton-Kiang kinetic aerosol model revised to include new information on aerosol nucleation and coagulation rates. The recent modifications in the coagulation rate coefficient are shown to have little effect on our previous analysis of aerosol growth process. Use of the new sulfuric acid vapor pressure data, which is higher than previously assumed, leads to an increase in the nucleation rates. As a result, secondary aerosol formation in the presence of pre-existing particles is enhanced. In addition, growth of these tiny new particles into the submicron particle size range which contribute to adverse effects such as visibility degradation becomes even more pronounced.