Extending the Kolmogorov-Zurbenko filter: application to ozone, particulate matter, and meteorological trends

Tropospheric ozone (O3) and particulate matter (PM) are pollutants of great concern to air quality managers. Federal standards for these pollutants have been promulgated in recent years because of the known adverse effects of the pollutants on human health, the environment, and visibility. Local meteorological conditions exert a strong influence over day-to-day variations in pollutant concentrations; therefore, the meteorological signal must be removed in order for air quality planners and managers to examine underlying emissions-related trends and make better air quality management decisions for the future. Although the Kolmogorov-Zurbenko (KZ) filter has been widely used for this type of trend separation in O3 studies in the eastern United States, this article aims to extend the method in three key ways. First, whereas the KZ filter is known as a useful tool for O3 analysis, this study also evaluates its effectiveness when applied to PM. Second, the method was applied to Tucson, AZ, a city in the semi-arid southwestern United States (Southwest), to evaluate the appropriateness of the method in a region with weaker synoptic weather controls on air quality than the eastern United States. Third, additional forms of output were developed and tailored to be more applicable to decision-makers' needs through a partnership between academic researchers and air quality planners and managers. Results of the study indicate that the KZ filter is a useful method for examining emissions-related PM trends, resulting in small, but potentially significant, differences after adjustment. For the Tucson situation with weaker synoptic controls, the KZ method identified mixing height as a more important variable than has been found in other cities.     

Extending the Kolmogorov–Zurbenko Filter: Application to Ozone,Particulate Matter,and Meteorological Trends

Abstract

Tropospheric ozone (O₃) and particulate matter (PM) are pollutants of great concern to air quality managers. Federal standards for these pollutants have been promulgated in recent years because of the known adverse effects of the pollutants on human health, the environment, and visibility. Local meteorological conditions exert a strong influence over day‐to‐day variations in pollutant concentrations; therefore, the meteorological signal must be removed in order for air quality planners and managers to examine underlying emissions-related trends and make better air quality management decisions for the future. Although the Kolmogorov–Zurbenko (KZ) filter has been widely used for this type of trend separation in O₃ studies in the eastern United States, this article aims to extend the method in three key ways. First, whereas the KZ filter is known as a useful tool for O₃ analysis, this study also evaluates its effectiveness when applied to PM. Second, the method was applied to Tucson, AZ, a city in the semi‐arid southwestern United States (Southwest), to evaluate the appropriateness of the method in a region with weaker synoptic weather controls on air quality than the eastern United States. Third, additional forms of output were developed and tailored to be more applicable to decision-makers’ needs through a partnership between academic researchers and air quality planners and managers. Results of the study indicate that the KZ filter is a useful method for examining emissions‐related PM trends, resulting in small, but potentially significant, differences after adjustment. For the Tucson situation with weaker synoptic controls, the KZ method identified mixing height as a more important variable than has been found in other cities.     

Effects of Acid Rain and Gaseous Pollutants on Forest Productivity: A Regional Scale Approach

Increased industrialization of the eastern U.S. over the past several decades has led to regional scale buildup of atmospheric pollutants and concern over possible losses in forest productivity within this region. This paper describes the rationale, methodology, and some preliminary results of a large regional scale study designed to characterize and quantify forest growth impacts attributable to atmospheric stress from both gaseous pollutants and acid rainfall. This research employs a variety of dendroecological techniques to examine the influence of climatic factors, tree age, soil type, competition, and air pollution on tree growth. This broadly collaborative project involves twelve government and university research stations working with a common experimental protocol to examine ≥50 year ringwidth series from approximately 6000 trees distributed over an area extending from Maine to North Carolina and as far west as Missouri. Principal objectives of this research are to determine whether a systematic pattern of decreasing forest growth has occurred, to define its temporal, spatial, and quantitative characteristics, to determine its relationship to differences in soil quality and tree species, and to evaluate its correlation with present and past indices of atmospheric deposition.     

Haze trends over the United States, 1980–1995

The patterns and trends of haze over the United States for the period of 1980–1995 are presented. Haze measurements are based on human visual range observations at 298 synoptic meteorological stations operated by the United States Weather Service. There was a significant (∼10%) decline in haziness over the 15-yr period. The reductions were evident throughout the eastern United States as well as over the hazy air basins of California. During the same period, in the eastern United States sulfur emissions also declined by about 10%. However, a causality for the reductions has not been established. This report is an update of an earlier survey of haze patterns and trends from 1950 to 1980.     

A Comparison of Measured and Simulated Ozone Concentrations in the Rural Areas of the Eastern United States during Summer 1995

ABSTRACT

The recent regulatory actions toward a longer-term (i.e., 8-hr) average ozone standard have brought forth the potential for many rural areas in the eastern United States to be in noncompliance. However, since a majority of these rural areas have generally few sources of anthropogenic emissions, the measured ozone levels primarily reflect the effects of the transport of ozone and its precursor pollutants and natural emissions. While photochemical grid models have been applied to urban areas to develop ozone mitigation measures, these efforts have been limited to high ozone episode events only and do not adequately cover rural regions. In this study, we applied a photochemical modeling system, RAMS/UAM-V, to the eastern United States from June 1-August 31, 1995. The purpose of the study is to examine the predictive ability of the modeling system at rural monitoring stations that are part of the Clean Air Status Trends Network (CASTNet) and the Gaseous Pollutant Monitoring Program (GPMP).

The results show that the measured daily 1-hr ozone maxima and the seasonal average of the daily 1-hr ozone maxima are in better agreement with the predictions of the modeling system than those for the daily 8-hr ozone maxima. Also, the response of the modeling system in reproducing the measured range of ozone levels over the diurnal cycle is poor, suggesting the need for improvement in the treatment of the physical and chemical processes of the modeling system during the nighttime and morning hours if it is to be used to address the 8-hr ozone standard.     

The carcinogenic risk of some organic vapors indoors: A theoretical survey

This exploratory report examines the risk of selected organic air pollutants measured in homes in the United States and the Netherlands. After several theoretical assumptions, estimates are made for the carcinogenic potency of each chemical; combined with the exposure measurements these give estimates of cancer risk. These estimates are compared with risks of these same pollutants outdoors and in drinking water and also with other well known indoor air pollutants: cigarette smoke, radon gas and formaldehyde. These comparisons indicate priorities for action. Some suggestions are made for future studies.     

A comparison of measured and simulated ozone concentrations in the rural areas of the eastern United States during summer 1995

The recent regulatory actions toward a longer-term (i.e., 8-hr) average ozone standard have brought forth the potential for many rural areas in the eastern United States to be in noncompliance. However, since a majority of these rural areas have generally few sources of anthropogenic emissions, the measured ozone levels primarily reflect the effects of the transport of ozone and its precursor pollutants and natural emissions. While photochemical grid models have been applied to urban areas to develop ozone mitigation measures, these efforts have been limited to high ozone episode events only and do not adequately cover rural regions. In this study, we applied a photochemical modeling system, RAMS/UAM-V, to the eastern United States from June 1-August 31, 1995. The purpose of the study is to examine the predictive ability of the modeling system at rural monitoring stations that are part of the Clean Air Status Trends Network (CASTNet) and the Gaseous Pollutant Monitoring Program (GPMP). The results show that the measured daily 1-hr ozone maxima and the seasonal average of the daily 1-hr ozone maxima are in better agreement with the predictions of the modeling system than those for the daily 8-hr ozone maxima. Also, the response of the modeling system in reproducing the measured range of ozone levels over the diurnal cycle is poor, suggesting the need for improvement in the treatment of the physical and chemical processes of the modeling system during the nighttime and morning hours if it is to be used to address the 8-hr ozone standard.     

A Critical Review

Atmospheric pollution attributed to increased combustion of fossil fuels has been implicated as a likely contributing factor in observed changes to forests in North America and Europe. Uncertainties surrounding the mechanisms and specific causes for these changes have prompted intensified interest in research on air pollution effects on forests. Major objectives of this review are 1) to provide a conceptual and historical perspective against which today's problems, concerns, and approaches can be evaluated; 2) to evaluate evidence of changes in growth and vitality of some tree species in today's forests; 3) to compare levels of principal atmospheric pollutants in Europe and the U.S.; 4) to describe mechanisms, pathways, and concentration thresholds for effects of principal pollutants on tree growth and physiology; 5) to summarize current evidence for the role of pollution in observed forest declines; and 6) to provide some perspectives on future research in this area. Evidence from laboratory and field research is examined to provide a basis for evaluating the role of atmospheric pollution in present and potential future forest responses.     

Air quality and its possible impacts on the terrestrial ecosystems of the North American Great Plains: an overview

Over the past several decades, numerous studies have been conducted on the impacts of air pollutants (air quality) on terrestrial ecosystems (crops and forests). Although ambient air is always composed of pollutant mixtures, in determining the relative air quality and its ecosystem impacts at a given geographic location and time, a predominant number of studies have shown that at the present time surface-level O(3) is the most important phytotoxic air pollutant. Within the North American Great Plains, the precursors for surface-level O(3) are mainly anthropogenic NO(x) and VOCs (volatile organic compounds). Texas and Alberta are the top regions of such emissions in the United States and Canada, respectively. This appears to be due mainly to the prevalence of natural gas and/or oil industry in the two regions and the consequent urbanization. Nevertheless, the total emissions of NO(x) and VOCs within the North American Great Plains represent only about 25-36% of the corresponding total emissions within the contiguous United States and the whole of Canada. Within the Great Plains many major crop and tree species are known to be sensitive to O(3). This sensitivity assessment, however, is based mainly on our knowledge from univariate (O(3) only) exposure-plant response studies. In the context of global climate change, in almost all similar univariate studies, elevated CO(2) concentrations have produced increases in plant biomass (both crop and tree species). The question remains as to whether this stimulation will offset any adverse effects of elevated surface O(3) concentrations. Future research must address this important issue both for the Great Plains and for all other geographic locations, taking into consideration spatial and temporal variabilities in the ambient concentrations of the two trace gases.     

Evidence for trans-cuticular uptake of HNO3 vapor by foliage of Eastern white pine (Pinus strobus L.)

Forest declines in Europe and the northeastern United States are widely believed to be associated with deposition of air pollutants, perhaps including nitric acid vapor. The experiments presented here, which were conducted in indoor chambers, involved measurement of steady-state rates of nitric acid deposition on foliage of seedlings of eastern white pine. Nitric acid concentrations ranged from 37 to 1260 ppb, but were mostly in the 130-180 ppb range. Between 130 and 180 ppb, much of the deposited nitric acid could be removed by washing leaf surfaces with water. Amounts of nitrate removed by washing increased with exposure duration to a maximum of 7.6 nmol cm(-2) after about 8 h. Although nitrate concentrations in the washings remained constant after 8 h, nitric acid deposition nonetheless continued at a steady-state rate. We have termed this steady-state deposition 'trans-cuticular' on the assumption that the nitric acid diffuses through the cuticle. Resistance to trans-cuticular uptake (69 m(2) s mol(-1)) far exceeded resistance to diffusion across the unstirred layer at the surface of the leaf (5 m(2) s mol(-1)). High concentrations used in these experiments preclude quantitative extrapolation to ambient conditions; however, we have demonstrated that the white pine cuticle is both a major storage pool and a major barrier to uptake of deposited nitric acid.     

Economic Benefits of Improvements in Visibility: Acid Rain Provisions of the 1990 Clean Air Act Amendments

The Acid Rain Provisions (Title IV) of the Clean Air Act Amendments of 1990 call for about a 10 million ton reduction in annual SO₂ emissions in the United States. Although the provisions apply nationwide, most of the reduction will occur in the eastern half of the country, where use of high-sulfur coal for electricity generation is most common. One potentially large benefit of Title IV is the expected improvement in visibility conditions in the eastern United States due to the reductions in secondary sul-fate aerosols. This paper combines available economic estimates of willingness to pay for improvements in visibility with current estimates of the difference between expected visibility conditions in the eastern United States with and without Title I V, to estimate the expected visibility benefits of Title IV. The results suggest an annual value of $2.3 billion (in 1994 dollars) in the year 2010, as a result of visibility improvements due to Title IV in residential areas of the eastern United States. The results also suggest a possible additional annual value for eastern U.S. residents of as much as $1-2 billion for visibility improvements at national parks in the Southeast.     

Improved space–time forecasting of next day ozone concentrations in the eastern US

There is an urgent need to provide accurate air quality information and forecasts to the general public and environmental health decision-makers. This paper develops a hierarchical space–time model for daily 8-h maximum ozone concentration (O₃) data covering much of the eastern United States. The model combines observed data and forecast output from a computer simulation model known as the Eta Community Multi-scale Air Quality (CMAQ) forecast model in a very flexible, yet computationally fast way, so that the next day forecasts can be computed in real-time operational mode. The model adjusts for spatio-temporal biases in the Eta CMAQ forecasts and avoids a change of support problem often encountered in data fusion settings where real data have been observed at point level monitoring sites, but the forecasts from the computer model are provided at grid cell levels. The model is validated with a large amount of set-aside data and is shown to provide much improved forecasts of daily O₃ concentrations in the eastern United States.     

Rural Ozone Across the Eastern United States: Analysis of CASTNet Data, 1988–1995

ABSTRACT

A predominantly rural ozone monitoring network was operated under the auspices of the Clean Air Status and Trends Network (CASTNet) from 1988 until 1995. Ozone data from sites in the eastern United States are presented and several indices are used to describe the spatial and temporal distribution of ozone concentration and exposure. These indices are SUM06, W126, the 8-hour rolling average (MAX_8hr>80), and the current National Ambient Air Quality Standards (NAAQS) for ozone. Ozone indices were selected to illustrate the spatial and temporal distribution of ozone, and the sensitivity of this distribution to different representations of concentration or exposure.

CASTNet is unique in that a uniform set of site selection criteria and uniform procedures, including traceability to a single primary standard, provide a high degree of comparability across sites. Sites were selected to avoid undue influence from point sources, area sources, or local activities. The sites reflect a wide range of land use and terrain types including agricultural and forested, in flat, rolling, and complex terrain from the eastern seaboard across the Appalachian Mountains to the Midwest.

Results indicate that ozone concentrations varied greatly in time and space across the eastern United States. Sites in the upper northeast, upper midwest, and southern periphery subregions experienced relatively low ozone during the years of record compared to sites in the northeast, midwest, and south central subregions. Ozone exposures at an individual rural site are dependent on many factors, including terrain, meteorology, and distance from sources of precursors. Relative to the current (as of 1996) NAAQS, only a handful of CASTNet sites near major urban areas report exceedances. In contrast, the majority of CASTNet sites might exceed the proposed new primary standard for ozone.

Sites at high elevation (>900m) in the east exhibit relatively high exposure statistics (e.g., SUM06 and W126), but no exceedance of the current ozone standard from 1988 through 1995. Terrain effects explain some of the variability within subregions and are an important consideration in the design of monitoring networks for ozone and possibly other pollutants.     

Lime/Limestone Scrubber Operation and Control

This paper examines operating and control experience obtained at full-scale lime-limestone scrubber systems both in the eastern and western United States. Methods of resolving typical problems in pH control of reagent feed, water balance closure, and slurry solids de-watering are discussed and described. Control problems can be severely aggravated by scale formation inside scrubbing equipment, especially on control sensors. If the sensor reliability problems can be resolved in a properly-designed scrubbing system, then the scrubber chemistry can generally be controlled and scale formation can usually be prevented. Current regulatory trends towards zero blowdown requirements increase scrubber operating and control problems, both from a process control standpoint (due to system complexity) and from a sensor reliability standpoint (due to an increased likelihood for chemical scale formation). These factors highlight the need for continuing development of improved scrubbing systems.     

PM10 pollution episodes as a function of synoptic climatology in a mountainous industrial area

In this study an attempt is made to investigate the prevailing meteorological conditions during days with high concentrations of PM10 (particles with diameter < 10 microns), collected in the Eordea mountain basin. This is an industrial area in the northwestern mountainous region of Greece. Over the 4-year data-gathering period, the days in which the United States Environmental Protection Agency 24-h PM10 standard was exceeded (episode days), were identified in relation to prevailing synoptic scale and local meteorological conditions. The results indicated that days with increased PM10 concentrations in this area can be grouped into four categories in relation to their synoptic circulation characteristics. The highest concentrations were found to be associated with stagnant conditions. Under these conditions, local circulations developed in the area, resulting in recirculation and accumulation of pollutants.     

Spatial pattern of ozone injury in Aleppo pine related to air pollution dynamics in a coastal-mountain region of eastern Spain

In eastern Spain, studies combining the tracking and meso-scale circulations of air pollutants with the evaluation of their effects on plants have been undertaken since 1994. Meso-scale processes are very important from the point of view of how and where forest ecosystems are affected by point sources and regional air pollution in the Mediterranean area. The first results of these field surveys show that in 1994, 1995 and 1996, the distribution pattern of ozone visual injury (chlorotic mottle) in Pinus halepensis correlated with the penetration of pollutants transported by the sea-breeze into coastal valleys of Castellón (eastern Spain). In this tree species, longer needles are associated with higher chlorotic mottle, and ozone injury seems to be among the factors affecting needle retention and crown transparency.     

Spatial and Temporal Variability of Ozone Exposure in Forested Areas of the United States and Canada: 1978—1988

Ambient O₃ exposures have reduced growth rates of tree genotypes in some areas of the United States. For characterizing O₃ exposures in forested areas, data from primarily population-oriented sites have been used. It has been speculated that exposures calculated from population-oriented sites provide estimates greater than those that would actually be experienced in the majority of forested areas. Accordingly, we compared 1988 O₃ data from three remote forested sites with data from several population-oriented monitoring sites in and around the mid? and southern Appalachian Mountains. The number of hours ≥0.08 ppm was lower at the remote forested sites than at the nearby population-oriented locations. In addition, we characterized the temporal variability of O₃ exposures in forested regions of the United States and Canada for the period 1978-1988. We found that the years of highest O₃ exposure in the eastern United States during 1978-1988 were 1978, 1980, 1983, and 1988, with 1988 being the worst year in four of seven eastern forest regions. In 1988, the Whiteface Mountain summit site (1483 m) experienced approximately 10 percent more hourly average concentrations ≥0.08 ppm than in the second highest O₃ exposure year (i.e., 1979). Consistently throughout the 11-year period, the highest O₃ exposures at the Whiteface Mountain site occurred during the late evening and early morning hours, with the result that the longterm 7-h (0900-1559h) exposure index could not distinguish those years in which the highest exposures occurred from those in which the lowest occurred. Similar to the Whiteface Mountain site, two high-elevation Shenandoah National Park sites experienced their highest O₃ exposures in 1988. With the exception of 1986, the lower elevation site (Dickey Ridge) consistently experienced more frequent occurrences of hourly average concentrations ≥0.08 ppm than the higher elevation site (Big Meadows).     

Air pollution and forest decline in Central Europe

The term 'Waldsterben' was introduced in the early 1980s to describe the progressive death of forests that was believed to be occurring in Central Europe as a result of air pollution. Subsequent surveys and investigations have failed to confirm that forests are dying or are even declining over large areas of Central Europe, defined here as consisting of Germany, Switzerland, southeastern France (Alsace), the Czech Republic, northern Italy and Austria. Foliar injury by air pollutants, together with mortality, has occurred, but is generally restricted to specific locations in the Czech Republic and in eastern Germany, such as the Fichtelgebirge. Where foliar damage has been recorded, it can often be attributed to high concentrations of sulphur dioxide, often acting in combination with other stresses (e.g. frost or insects). Outside areas affected by local sources of pollution, there is little, if any, evidence that the crown condition of trees has been adversely affected by pollution over large areas. Instead, climate appears to have a major effect on the crown condition and growth of trees. Measurements and surveys have revealed a very different picture to that forecasted in the mid-1980s. Growth rates of trees and stands in Central Europe are currently higher than have been recorded at any time in the past; the reasons for this are uncertain, although increases in forest area have not substantially contributed to the observed trends. Although declines in individual species in specific areas have been recorded, past records indicate that these do not represent a new phenomenon. Consequently, the terms 'Waldsterben' (forest deaths) and 'neuartige Waldsch?den' (novel type of forest damages) should not be used in the context of the phenomenon reported in Central Europe in the 1980s. Instead, different problems should be described separately and the term forest decline used only when there is clear evidence of a general deterioration in the condition of all tree species within a forest.     

The effects of meteorology on ozone in urban areas and their use in assessing ozone trends

The United States Environmental Protection Agency issues periodic reports that describe air quality trends in the US. For some pollutants, such as ozone, both observed and meteorologically adjusted trends are displayed. This paper describes an improved statistical methodology for meteorologically adjusting ozone trends as well as characterizes the relationships between individual meteorological parameters and ozone. A generalized linear model that accommodates the nonlinear effects of the meteorological variables was fit to data collected for 39 major eastern US urban areas. Overall, the model performs very well, yielding R² statistics as high as 0.80. The analysis confirms that ozone is generally increasing with increasing temperature and decreasing with increasing relative humidity. Examination of the spatial gradients of these responses show that the effect of temperature on ozone is most pronounced in the north while the opposite is true of relative humidity. By including HYSPLIT-derived transport wind direction and distance in the model, it is shown that the largest incremental impact of wind direction on ozone occurs along the periphery of the study domain, which encompasses major NO_x emission sources.