Trends in exceedances of the ozone air quality standard in the continental United States, 1980–1998

In 1997, the United States National Ambient Air Quality Standard (NAAQS) for ozone was revised from a 1-h average of 0.12 parts per million (ppm) to an 8-h average of 0.08 ppm. Analysis of ozone data for the ensemble of the contiguous United States and for the period 1980–1998 shows that the average number of summer days per year in exceedance of the new standard is in the range 8–24 in the Northeast and in Texas, and 12–73 in southern California. The probability of exceedance increases with temperature and exceeds 20% in the Northeast for daily maximum temperatures above 305 K. We present the results of several different approaches to analyzing the long-term trends in the old and new standards over the continental United States from 1980 to 1998. Daily temperature data are used to resolve meteorological variability and isolate the effects of changes in anthropogenic emissions. Significant negative trends are found in the Northeast urban corridor, in the Los Angeles Basin and on the western bank of Lake Michigan. Temperature segregation enhances the detection of negative trends. Positive trends occur at isolated sites, mostly in the Southeast; a strong positive trend is found in Nashville (Tennessee). There is some evidence that, except in the Southwest, air quality improvements from the 1980s to the 1990s have leveled off in the past decade.     

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.     

Trends in atmospheric sulfur and nitrogen species in the eastern United States for 1989–1995

Emission reductions were mandated in the Clean Air Act Amendments of 1990 with the expectation that they would result in major reductions in the concentrations of atmospherically transported pollutants. This paper investigates the form and magnitude of trends from 1989 to 1995 in atmospheric concentrations of sulfur dioxide, sulfate, and nitrogen at 34 rural sites in the eastern US. Across all sites, there is strong evidence of statistically significant declining trends in sulfur dioxide (median change of -35%) and sulfate concentrations (median change of -26%). In general, trends in nitrogen concentrations were not as pronounced (median change of -8%) as trends in the sulfur compounds. A regional estimate of trend for a cluster of sites in the Ohio River valley showed close correspondence between declining sulfur dioxide concentrations (-35%) and changes in sulfur dioxide emissions (-32%) in this region.     

Atmospheric aerosol over two urban–rural pairs in the southeastern United States: Chemical composition and possible sources

Positive matrix factorization (PMF) was used to infer the sources of PM_2.5 observed at four sites in Georgia and Alabama. One pair of urban and rural sites in each state is used to examine the regional and urban influence on PM_2.5 concentrations in the Southeast. Eight factors were resolved for the two urban sites and seven factors were resolved for the two rural sites. Spatial correlations of factors were investigated using the square of correlation coefficient (R²) calculated from the resolved G factors. Fourier transform was used to define the temporal characteristics of PM_2.5 factors at these sites. Factors were normalized by using aerosol fine mass concentration data through multiple linear regression to obtain the quantitative factor contributions for each resolved factor. Common factors include: (1) secondary sulfate dominated by high concentrations of sulfate and ammonium with a strong seasonal variation peaking in summer; (2) nitrate and the associated ammonium with a seasonal maximum in winter; (3) “coal combustion/other” factor with presence of sulfate, EC, OC, and Se; (4) soil represented by Al, Ca, Fe, K, Si and Ti; and (5) wood smoke with the high concentrations of EC, OC and K. The motor vehicle factor with high concentrations of EC and OC and the presence of some soil dust components is found at the urban sites, but cannot be resolved for the two rural sites. Among the other factors, two similar industry factors are found at the two sites in each state. For the wood smoke factor, different seasonal trends are found between urban and rural sites, suggesting different wood burning patterns between urban and rural regions. For the industry factors, different seasonal variations are also found between urban and rural sites, suggesting that this factor may come from different sources or a common source may impact the two sites differently. Generally, sulfate, soil, and nitrate factors at the four sites showed similar chemical composition profiles and seasonal variation patterns reflecting the regional characteristics of these factors. These regional factors have predominantly low frequency variations while local factors such as coal combustion, motor vehicle, wood smoke, and industry factors have high frequency variations in addition to low frequency variations.     

China’s air pollution reduction efforts may result in an increase in surface ozone levels in highly polluted areas

China, as a fast growing fossil-fuel-based economy, experiences increasing levels of air pollution. To tackle air pollution, China has taken the first steps by setting emission–reduction targets for nitrogen oxides (NO_x) and sulphur dioxide (SO₂) in the 11th and 12th Five Year Plans. This paper uses two models—the Energy–Environment–Economy Model at the Global level (E3MG) and the global Chemistry Transport Model pTOMCAT—to test the effects of these policies. If the policy targets are met, then the maximum values of 32 % and 45 % reductions below ‘business as usual’ in the monthly mean NO_x and SO₂ concentrations, respectively, will be achieved in 2015. However, a decrease in NO_x concentrations in some highly polluted areas of East, North-East and South-East China can lead to up to a 10% increase in the monthly mean concentrations in surface ozone in 2015. Our study demonstrates an urgent need for the more detailed analysis of the impacts and designs of air pollution reduction guidelines for China.     

Inhomogeneities and trends in the surface ozone record (1988–1996) at Jungfraujoch in the Swiss Alps

Ozone data at the Jungfraujoch Observatory (3580 m asl) in the Swiss Alps have been recorded continuously since 1986 in the framework of the Swiss National Air Pollution Monitoring Network (NABEL), operated by the Swiss Federal Laboratories for Materials Testing and Research (EMPA). The long-term ozone record (1988–1996) was examined with regard to potential inhomogeneities using Zugspitze (2960 m asl), a neighbouring alpine site in Germany, as a reference site. The Alexandersson test (for shift) and the Easterling–Peterson test (for trend and shift) were applied to a difference times series, calculated from monthly ozone means at Jungfraujoch and Zugspitze. The Alexandersson test revealed a significant shift discontinuity in November 1989 and the Easterling–Peterson test a trend discontinuity in September 1991. It is assumed that the shift discontinuity may be related to an instrument change, but there is not firm evidence due to lack of detailed information from the instrumental history in the earlier years of the ozone record at Jungfraujoch. Monthly ozone means at Davos (1640 m asl) in eastern Switzerland indicate that part of the trend discontinuity in September 1991 may be of natural origin. Adjustment of the monthly ozone means at Jungfraujoch for the observed shift discontinuity removed the inhomogeneity in November 1989, and reduced the trend discontinuity by a factor of 4.8. A trend analysis on both adjusted (homogenised) and unadjusted monthly ozone means (1988–1996) at Jungfraujoch showed no statistically significant linear trend. The boundaries encompassing the true linear trend are indicated by two linear regression calculations on both adjusted and unadjusted data. Trends in the cold season are positive albeit not significant. The only statistically significant trends are found in October, December, and February for the adjusted data.     

A synoptic climatology for surface ozone concentrations in Southern Ontario, 1976–1981

The synoptic climatology of ozone (O₃) for S Ontario has shown that, over the 1976–1981 period, average summer O₃ concentrations follow a relationship similar to that reported for event analysis during periods of high O₃ concentration. Highest average concentrations, 36 parts per billion (ppb), occur with ‘back of the high’ situations while lowest average concentrations (20 ppb) occur with ‘front of the high’ situations.With similar weather events in the winter, the pattern is reversed with highest average O₃ concentrations on the ‘front of the high’ (19 ppb) and lowest average concentrations on the ‘back of the high’ (13 ppb). Concentration of O₃ in the ‘front of the high’ sector is due in part to the intrusion of O₃ in the vicinity of storms from the stratosphere. The seasonal variation of average concentrations in these situations is low, ranging from 14 to 26 ppb.The very low average concentration during the winter and fall for the ‘back of the high’ situation may be the result of scavenging by NO_x from the urban/industrial areas around the Great Lakes. During the spring and summer, solar energy and warm temperatures cause the photochemical production of O₃ from NO_x and HCs precursors. In the fall and winter, photochemical production of O₃ is either very low or absent, and the NO_x consume O₃ rather than produce it. Thus, average O₃ concentrations for winter ‘back of the high’ situations are one-third of those in the summer months.The synoptic climatology of events during the months from May to September with maximum O₃ concentrations in excess of 80 ppb indicates that 78 % of these events occur under synoptic weather classes generally indicative of back or centre of the high situations.     

Changes in the wet precipitation of sodium and chloride over the continental United States, 1984–2006

Data on wet-only precipitation from the National Atmospheric Deposition Program/National Trends Network were analysed for trends in the sodium and chloride fluxes over the United States between 1 January 1984 and 31 December 2006. The data were first checked for consistency and for ionic balance. It was necessary to correct for changes in bicarbonate due to changes in atmospheric CO₂ levels over the study period, in order to obtain a balance. The fluxes were calculated and the trends determined by linear regression in the log domain. The significance of the trends was checked using both F- and t-tests. At 154 sites having reasonably continuous records over the assessment period, the sodium flux fell significantly at 139 and increased significantly at only one. The chloride flux similarly fell significantly at 140 and increased significantly at the same one as the sodium flux increased. At coastal sites the chloride to sodium ratio was the same as that in sea water, within experimental limits. Further from the coast the ratio changed apparently due to changes in the entire aerosol chemistry. The findings are discussed in terms of the simplicity and robustness of the methodology employed to determine the trends; the oceanic origin of most observable sodium even in the interior of the continent, probably because it occurs as a fine (<1 micron) aerosol which is poorly scavenged by precipitation; and the possibility that the drop in sodium and chloride fluxes might be driven by climate change.     

NMOC,ozone, and organic aerosol in the southeastern United States, 1999–2007: 2. Ozone trends and sensitivity to NMOC emissions in Atlanta,Georgia

Non-methane organic carbon (NMOC) measurements made in Atlanta, Georgia from 1999–2007 are used with nitrogen oxide (NO_x or NO_y) and ozone (O₃) data to investigate relationships between O₃ precursors and peak 8-hour O₃ concentrations in the city. Data from a WNW-to-ENE transect of sites illustrate that the mean urban peak 8-hour O₃ excess constitutes about 20% of the peak 8-hour O₃ measured at the area-wide maximum O₃ site when air-mass movement is from the northwest quadrant; local influence is potentially greater on days with more stagnation or recirculation. The peak 8-hour O₃ concentrations in Atlanta increase as (1) surface temperature (T), ambient NMOC and NO_y concentrations, and previous-day peak O₃ concentrations increase, and as (2) relative humidity, surface wind speeds, and ratios of NMOC-to-NO_y decrease. An observation-based statistical model is introduced to relate area-wide peak 8-hour O₃ concentrations to ambient NMOC and NO_y concentrations, while accounting for the non-linear dependences of peak 8-hour O₃ concentrations on meteorological factors. On the majority of days when the area-wide peak 8-hour O₃ exceeds 75 ppbv, meteorologically-adjusted peak 8-hour O₃ concentrations increase as ambient NMOC concentrations increase (NMOC sensitive) and ambient NO_y concentrations decrease. This result contrasts with regional conditions in which O₃ formation appears to be NO_x-sensitive in character. The results offer observationally-based information of relevance to O₃ management strategies in the Atlanta area, potentially contributing to “weight-of-evidence” assessments.     

NMOC,ozone, and organic aerosol in the southeastern United States, 1999–2007: 1. Spatial and temporal variations of NMOC concentrations and composition in Atlanta,Georgia

Volatile organic compounds (VOCs) are emitted from anthropogenic and natural (biogenic) sources into the atmosphere. Characterizing their ambient mixing ratios or concentrations is a challenge because VOCs comprise hundreds of species, and accurate measurements are difficult. Long-term hourly and daily-resolution data have been collected in the metropolitan area of Atlanta, Georgia, a major city dominated by motor vehicle emissions. A series of observations of daily, speciated C₂–C₁₀ non-methane organic compounds (NMOC) and oxygenated hydrocarbons (OVOC) in mid-town Atlanta (Jefferson Street, JST) are compared with data from three urban-suburban sites and a nearby non-urban site. Annual-average mixing ratios of NMOC and OVOC at JST declined from 1999 through 2007. Downward trends in NMOC, CO, and NO_y corroborate expected emission changes as reflected in emission inventories for Atlanta’s Fulton County. Comparison of the JST NMOC composition with data from roadside and tunnel sampling reveals similarities to motor vehicle dominated samples. The JST annual average VOC-OH reactivities from 1999 to 2007 were relatively constant compared with the decline in annual-average NMOC mixing ratios. Mean reactivity at JST, in terms of concentration*k_OH, was approximately 40% alkenes, 22% aromatics, 16% isoprene and 6% other biogenics, 13% C₇–C₁₀ alkanes and 3% C₂-C₆ alkanes, indicating that biogenic NMOCs are important but not dominant contributors to the urban reactive NMOC mix. In contrast, isoprene constituted ～50% of the VOC-OH reactivities at two non-urban sites. Ratios of 24-hour average CO/benzene, CO/isopentane, and CO/acetylene concentrations indicate that such species are relatively conserved, consistent with their low reactivity. Ratios of more-reactive to less-reactive species show diurnal variability largely consistent with expected emission patterns, transport and mixing of air, and chemical processing.     

The benefits of lower ozone due to air pollution emission reductions (2002–2011) in the Eastern United States during extreme heat

ABSTRACT

Using the Community Multiscale Air Quality (CMAQ) model and the Benefits Mapping and Analysis Program – Community Edition (BenMAP-CE) tool, we estimate the benefits of anthropogenic emission reductions between 2002 and 2011 in the Eastern United States (US) with respect to surface ozone concentrations and ozone-related health and economic impacts, during a month of extreme heat, July 2011. Based on CMAQ simulations using emissions appropriate for 2002 and 2011, we estimate that emission reductions since 2002 likely prevented 10– 15 ozone exceedance days (using the 2011 maximum 8-hr average ozone standard of 75 ppbv) throughout the Ohio River Valley and 5– 10 ozone exceedance days throughout the Washington, DC – Baltimore, MD metropolitan area during this extremely hot month. CMAQ results were fed into the BenMAP-CE tool to determine the health and health-related economic benefits of anthropogenic emission reductions between 2002 and 2011. We estimate that the concomitant health benefits from the ozone reductions were significant for this anomalous month: 160–800 mortalities (95% confidence interval (CI): 70–1,010) were avoided in July 2011 in the Eastern U.S, saving an estimated $1.3–$6.6 billion (CI: $174 million–$15.5 billion). Additionally, we estimate that emission reductions resulted in 950 (CI: 90–2,350) less hospital admissions from respiratory symptoms, 370 (CI: 180–580) less hospital admissions for pneumonia, 570 (CI: 0–1650) less Emergency Room (ER) visits from asthma symptoms, 922,020 (CI: 469,960–1,370,050) less minor restricted activity days (MRADs), and 430,240 (CI: ?280,350–963,190) less symptoms of asthma exacerbation during July 2011.

Implications: We estimate the benefits of air pollution emission reductions on surface ozone concentrations and ozone-related impacts on human health and the economy between 2002 and 2011 during an extremely hot month, July 2011, in the eastern United States (US) using the CMAQ and BenMAP-CE models. Results suggest that, during July 2011, emission reductions prevented 10-15 ozone exceedance days in the Ohio River Valley and 5-10 ozone exceedance days in the Mid Atlantic; saved 160-800 lives in the Eastern US, saving $1.3 - $6.5 billion; and resulted in 950 less hospital admissions for respiratory symptoms, 370 less hospital admissions for pneumonia, 570 less Emergency Room visits for asthma symptoms, 922,020 less minor restricted activity days, and 430,240 less symptoms of asthma exacerbation.     

Resource allocation for mitigating regional air pollution–related mortality: A summertime case study for five cities in the United States

An important issue of regional air quality management is to allocate air quality management funds to maximize environmental and human health benefits. In this study, we use an innovative approach to tackle this air quality management issue. We develop an innovative resource allocation model that allows identification of air pollutant emission control strategies that maximize mortality avoidances subject to a resource constraint. We first present the development of the resource allocation model and then a case study to show how the model can be used to identify resource allocation strategies that maximize mortality avoidances for top five Metropolitan Statistical Areas (MSAs) (i.e., New York, Los Angeles, Chicago, Dallas-Fort Worth, and Philadelphia) in the continental United States collectively. Given budget constraints in the U.S. Environmental Protection Agency’s (EPA) Clean Air Act assessment, the results of the case study suggest that controls of sulfur dioxide (SO₂) and primary carbon (PC) emissions from EPA Regions 2, 3, 5, 6, and 9 would have significant health benefits for the five selected cities collectively. Around 30,800 air pollution–related mortalities could be avoided during the selected 2-week summertime episode for the five cities collectively if the budget could be allocated based on the results of the resource allocation model. Although only five U.S. cities during a 2-week episode are considered in the case study, the resource allocation model can be used by decision-makers to plan air pollution mitigation strategies to achieve the most significant health benefits for other seasons and more cities over a region or the continental U.S.Implications: Effective allocations of air quality management resources are challenging and complicated, and it is desired to have a tool that can help decision-makers better allocate the funds to maximize health benefits of air pollution mitigation. An innovative resource allocation model developed in this study can help decision-makers identify the best resource allocation strategies for multiple cities collectively. The results of a case study suggest that controls of primary carbon and sulfur dioxides emissions would achieve the most significant health benefits for five selected cities collectively.     

Black Carbon and Polycyclic Aromatic Hydrocarbon Emissions from Vehicles in the United States–Mexico Border Region: Pilot Study

The investigators developed a system to measure black carbon (BC) and particle-bound polycyclic aromatic hydrocarbon (PAH) emission factors during roadside sampling in four cities along the United States–Mexico border, Calexico/Mexicali and El Paso/Juárez. The measurement system included a photoacoustic analyzer for BC, a photoelectric aerosol sensor for particle-bound PAHs, and a carbon dioxide (CO₂) analyzer. When a vehicle with measurable emissions passed the system probe, corresponding BC, PAH, and CO₂ peaks were evident, and a fuel-based emission factor was estimated. A picture of each vehicle was also recorded with a digital camera. The advantage of this system, compared with other roadside methods, is the direct measurement of particulate matter components and limited interference from roadside dust. The study revealed some interesting trends: Mexican buses and all medium-duty trucks were more frequently identified as high emitters of BC and PAH than heavy-duty trucks or passenger vehicles. In addition, because of the high daily mileage of buses, they are good candidates for additional study. Mexican trucks and buses had higher average emission factors compared with U.S. trucks and buses, but the differences were not statistically significant. Few passenger vehicles had measurable BC and PAH emissions, although the highest emission factor came from an older model passenger vehicle licensed in Baja California.     

Trend analysis of monthly sulfur dioxide emissions in the conterminous United States, 1975–1984

Trends in monthly sulfur dioxide emissions for the 48 conterminous United States during the decade 1975–1984 are identified using a robust nonparametric procedure. Statistically significant downward trends are indicated in 32 States, upward trends appear in 10 States, and no significant trend is apparent in six States. Geographically, a distinct regional pattern of emission increases and decreases is evident with declines dominating the Eastern and Western States; increases aligning longitudinally from border to border in most of the Great Plains States, in several New England States, and in Georgia; and no trends frequently occurring in proximity to the upward trending emissions in the Plains States. A time-series decomposition of the monthly values indicates that one distinct emissions pattern commonly occurred through the period of record. This pattern is characterized by an initial emissions increase that peaks between 1977 and 1978, followed by a shallow and undulating decrease through the end of 1984. It is suggested that this signature represents the ‘national’ trend for the period. In addition, five regions of coherent sulfur dioxide emissions behavior are defined on the basis of seasonal occurrence of maximum and minimum emission loadings. A winter-summer, latitudinal opposition is apparent in the timing of emissions maxima, whereas an equinox-summer, longitudinal opposition is apparent in the timing of emissions minima.     

Increase in springtime tropospheric ozone at a mountainous site in Japan for the period 1998–2006

The trend of tropospheric ozone from 1998 to 2006 was examined based on continuous measurements made at a site on Mt. Happo, Japan. We focused our study on springtime ozone, to coincide with the East Asian continental outflow that dominates the lower tropospheric ozone over Japan during this season. The observed increase of ～1 ppbv yr^?1 in the mean ozone level was statistically significant. We also found that the probability distribution of the springtime ozone mixing ratios was substantially modified, with the ozone mixing ratios greatly increasing at the upper end of the probability distribution. This increase has been particularly large since 2003, with larger increases occurring at the higher percentiles. The number of high-ozone days doubled during 2003–2006 compared to 1999–2002. One of the very likely explanations is the enhancement of regional ozone pollution due to rapidly increasing anthropogenic emissions from East Asia.     

Formaldehyde measurements in Dutch houses,schools and offices in the years 1977–1980

Many formaldehyde concentration measurements were performed in houses, schools and offices where chipboard material was used during the period 1977–1980 following complaints made by inhabitants. In one building the reason for the complaints was formaldehyde emission from urea-formaldehyde insulation foam instead of chipboard.The threshold limit value, established in the Netherlands at 120 μg formaldehyde m⁻³ (0.1 ppm) for living accommodation was exceeded in most cases. The limit was exceeded in 80% of the investigated houses, in 90% of the investigated schools and in 60% of the investigated offices.The efficiency of measures taken to decrease the formaldehyde concentration were investigated in several rooms by repeated measurements afterwards. In some cases the formaldehyde concentration could be reduced to a level lower than the limit value. This was shown to be difficult when the formaldehyde concentration is higher than 300–500 μg m⁻³, due to emission from chipboard. In one building where formaldehyde was emitted from insulation foam in the cavity wall, the formaldehyde concentration could be decreased from 2300 μ μ⁻³ to 80 μg m⁻³.The influence of the temperature and the ventilation rate could be verified in some cases in practice.     

Disturbed boundaries extraction in coal–grain overlap areas with high groundwater levels using UAV-based visible and multispectral imagery

Environmental Science and Pollution Research - With high groundwater levels, coal–grain overlap areas (CGOAs) are vulnerable to subsidence and water logging during mining activities, thereby...     

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).     

Predicting black smoke levels from deposit gauge and SO2 data to estimate long-term exposure in the United Kingdom, 1956–1961

BackgroundIn the UK air quality has been monitored systematically since 1914, providing valuable data for studies of the long-term trends in air pollution and potentially for studies of health effects of air pollutants. There are, however, challenges in interpreting these data due to changes over time in the number and location of monitored sites, and in monitoring techniques. Particulate matter was measured as deposited matter (DM) using deposit gauge monitors until the 1950s when black smoke (BS) filters were introduced. Estimating long-term exposure to particulates using data from both deposit gauge and BS monitors requires an understanding of the relationships between DM, SO₂ and BS.AimsTo explore whether DM and/or SO₂, along with seasonal and location specific variables can be used to predict BS levels.MethodsAir quality data were abstracted from hard copies of the monthly Atmospheric Pollution Bulletins for the period April 1956–March 1961 for any sites with co-located DM, SO₂ and BS data for three or more consecutive years. The relationships between DM, SO₂, and BS were assessed using mixed models.ResultsThere were 34 eligible sites giving 1521 triplets of data. There was a consistent correlation between SO₂ and BS at all sites, but the association between DM and BS was less clear and varied by location. Mixed modelling allowing for repeat measurements at each site revealed that SO₂, year, rainfall and season of measurement explained 72% of the variability in BS levels.ConclusionsSO₂ can be used as a surrogate measure for BS in all monitoring locations. This surrogate can be improved upon by consideration of site specific characteristics, seasonal effects, rainfall and year of measurement. These findings will help in estimating historic, long-term exposure to particulates where BS or other measures are not available.     

Relationships between air quality measurement methods in japan and the United States—II: Suspended particulate matter

Measurements of suspended particulate matter in the atmosphere are commonly determined by the use of the high volume air sampler. Concentrations of sulfate, nitrate and organic fractions of these measurements are also routinely determined in many countries. As part of the United States-Japan Cooperative Air Pollution Measurement Studies, parallel sampling employing the instruments and analytical methods from each country was conducted in Kawasaki, Japan between January and February and between March and May 1966. A significant difference of results between the methods was found for suspended particulate matter. Fair agreement was obtained between analytical results of the sulfate, nitrate and organic fractions. Relationships between the suspended particulate concentrations determined by these two methods are discussed.