The Influence of Annual Meteorological Variations On Regional Air Pollution Modeling: A Case Study of Allegheny County,Pennsylvania

The influence of year-to-year meteorological variations on the prediction of annual average ground-level pollutant concentrations has been examined via case studies of Allegheny County, Pa. Twenty-two stability wind roses representing different averaging intervals of from one to seven years were employed in the Air Quality Display Model to predict annual average SO₂ concentrations in two multiple source sub-basins, and from two single point sources representing industrial and utility boiler stacks. Effects of annual meteorological variations were manifested by changes in the magnitude of peak concentrations, the location of peak concentrations, and the geographic distribution of pollutants. For fixed rates of emission, the peak annual average SO₂ ground-level concentration varied by an average of up to 33% of highest values for point sources and 17% for sub-basin complexes. In both cases, there was relatively little change in the location of peak concentration, though occasional directional shifts were noted. In contrast, marked variations were noted in the geographic area exposed to annual average concentrations in excess of several selected values. To aid in regional planning, several methods were formulated which considerably reduced the uncertainty in predicting peak annual concentration for varying degrees of historical data on regional stability wind rose. These methods are-especially applicable to analysis of control strategies directed at attaining annual ambient air quality standards which nominally must never be exceeded.     

C2–C5 Hydrocarbon measurements in the Netherlands 1981–1991

Measurements of C₂–C₅ hydrocarbons on an hourly basis at the TNO site in Delft from 1982 to 1984 and at Moerdijk over the period 1981–1991 are presented. In combination with meteorological data (wind direction and wind speed) the Delft and Moerdijk series are evaluated to identify source categories, annual variations, background concentrations and trends. The C₂–C₅ hydrocarbon concentrations at Delft and Moerdijk are determined mainly by emission characteristics and meteorological dispersion; the dominant sources are relatively nearby and atmospheric degradation is not of much importance. Under conditions of high wind speed the concentrations measured at Moerdijk in the marine sector are close to the Atlantic background concentrations in winter and somewhat above this in summer. The continental background concentrations are higher than the marine background concentrations by a factor of almost two. The annual variation of acetylene is more pronounced than that of the other hydrocarbons, most likely due to a different seasonal variation in acetylene emissions. The annual variation of propene is smoother, indicating stronger sources in summer than in winter. This feature of propene is observed in continental as well as in marine sectors. The observations show that at Moerdijk C₂–C₄ concentrations measured in Rijnmond sector have decreased considerably since the early 1980s, corresponding with changes in emissions in that area. Averaged over all wind directions the trend of all species is downward, but for acetylene the trend is significant at a 95% confidence interval. The acetylene concentrations show an annual downward trend of 3% during the 1980s, supporting other estimates of decreasing hydrocarbon emissions from traffic over this period at the same rate.     

Ambient Air Benzene Concentrations in Canada (1989-1993): Seasonal and Day of Week Variations,Trends, and Source Influences

Abstract

Since 1987, the Pollution Measurement Division of the Environmental Protection Service, Environment Canada, has operated a field program for measuring benzene in ambient air. With the cooperation of provincial and municipal environmental agencies, samples have been collected at over 30 urban and rural monitoring sites across the country. Samples are collected in evacuated canisters and analyzed by gas chromatography with a mass-selective detector. Using data from all sites, the composite average benzene concentration for Canada over the years 1989 to 1993 was 3.6 μg/m³ and the composite median was found to be 2.6 μ/m³. Benzene concentrations are highest at urban sites near major streets and at sites influenced by industrial sources. For eighteen urban and suburban trend sites (those with no nearby industrial sources), composite annual median benzene concentrations decreased by 20% between 1989 and 1993. For the same period, median benzene concentrations decreased by 33% at four trend sites with nearby industries. At most monitoring sites the parameters for benzene and CO are highly correlated; supporting the inventory estimate that most emissions of benzene are due to vehicle exhaust. For sites with nearby industrial sources of benzene, the industries are estimated to account for 35 to 70% of the benzene dose experienced at the sites. These site specific contributions are much more significant than the estimated national emissions assigned to industrial sources.     

Collateral benefits and hidden hazards of soil arsenic during abatement assessment of residential lead hazards

Abatement of soil-lead hazards may also reduce human exposure to other soil toxins, thereby achieving significant collateral benefits that are not accounted for today. This proposition was tested with the specific case of soil-arsenic, where 1726 residential soil samples were collected and analyzed for lead and arsenic. The study found that these two toxins coexisted in most samples, but their concentrations were weakly correlated, reflecting the differing sources for each toxin. Collateral benefits of 9% would be achieved during abatement of the lead-contaminated soils having elevated arsenic concentrations. However, a hidden hazard of 16% was observed by overlooking elevated arsenic concentrations in soils having lead concentrations not requiring abatement. This study recommends that soil samples collected under HUD programs should be collected from areas of lead and arsenic deposition and tested for arsenic as well as lead, and that soil abatement decisions consider soil-arsenic as well as soil-lead guidelines.     

A modeling study of coarse particulate matter pollution in Beijing: regional source contributions and control implications for the 2008 Summer Olympics

In the last 10 yr, Beijing has made a great effort to improve its air quality. However, it is still suffering from regional coarse particulate matter (PM10) pollution that could be a challenge to the promise of clean air during the 2008 Olympics. To provide scientific guidance on regional air pollution control, the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality Model (CMAQ) air quality modeling system was used to investigate the contributions of emission sources outside the Beijing area to pollution levels in Beijing. The contributions to the PM10 concentrations in Beijing were assessed for the following sources: power plants, industry, domestic sources, transportation, agriculture, and biomass open burning. In January, it is estimated that on average 22% of the PM10 concentrations can be attributed to outside sources, of which domestic and industrial sources contributed 37 and 31%, respectively. In August, as much as 40% of the PM10 concentrations came from regional sources, of which approximately 41% came from industry and 31% from power plants. However, the synchronous analysis of the hourly concentrations, regional contributions, and wind vectors indicates that in the heaviest pollution periods the local emission sources play a more important role. The implications are that long-term control strategies should be based on regional-scale collaborations, and that emission abatement of local sources may be more effective in lowering the PM10 concentration levels on the heavy pollution days. Better air quality can be attained during the Olympics by placing effective emission controls on the local sources in Beijing and by controlling emissions from industry and power plants in the surrounding regions.     

Statistical inquiry into the causes of global temperature changes

Observed changes in average global temperatures over time have led to two general avenues of discussion in the environmental literature. The scientific community has concentrated on the statistical detection of global warming and the determination of biological and industrial factors causing average world temperatures to rise. A second avenue of thought considers the issue of economic abatement by attempting to measure the pecuniary costs of global warming and the elimination of factors influencing this problem. This paper concentrates not on developing an economic model of global warming and environmental damage, but rather on examining the problem from a purely statistical vantage point. Utilising annual data from 1950 to 1991 and optimally determined vector auto regression specifications, it is shown that general industrial growth and greenhouse gas emission levels statistically cause a persistent increase in average global temperatures. In addition, this analysis shows that increasing average world temperatures have a statistically significant negative causal impact on agricultural productivity. Given that global warming is a long-term process culminating from decades of industrial activity, statistically significant causal results derived in this paper using short term data are interesting. Statistical results suggest that trends in average temperatures respond to short-run fluctuations in industrial activity and population growth.     

Observations and Interpretations from the Canadian Fine Particle Monitoring Program

ABSTRACT

Canadian particle monitoring programs examining PM10, PM2.5, and particle composition have been in operation for over 10 years. Until recently, the measurements were manual/filter-based with 24-hr sample collection varying in frequency from daily to every sixth day, using GrasebyAnderson dichotomous samplers. In the past few years, these monitoring activities have been expanded to include hourly measurements using tapered element oscillating microbalances (TEOMs). This continuous monitoring program started operation focusing on PM_10, but now emphasizes PM_2.5 through the addition of more TEOMs and switching of the inlets of some of the existing units. The data from all of these measurement activities show that there are broad geographical differences and also local- to regional-scale spatial differences in mass and composition of PM2.5. Due to variations in sources, significantly different PM2.5 concentrations are not uncommon within the same city. Comparison of nearby urban and rural sites indicates that 30 and 40% of the PM_2.5 is from local urban sources in Montreal and Toronto, respectively. Hourly PM_2.5 measurements in Toronto suggest that vehicular emissions are an important contributor to urban PM_2.5. There has been a decreasing trend in urban PM_2.5, with annual average concentrations between the 1987–1990 and 1993–1995 periods decreasing by 11 to 39%, depending upon the site. The largest declines were in Montreal and Halifax, and the smallest decline was in Toronto. Comparison of 24-hr TEOM and manual dichotomous sampler PM_2.5 measurements from a site in Toronto indicates that the TEOM results in lower concentrations. The magnitude of this difference is relatively small in the warmer months, averaging about 12%. During the colder months the difference averages about 23%, but can be as large as 50%.     

Increasing concentrations of nitrogen dioxide pollution in rural Wales

Monitoring of nitrogen dioxide pollution was carried out in rural environments throughout Wales during a 1-year survey to quantify any changes in background concentrations and distribution of the pollutant since an earlier survey in 1986. There were 23 sites in the present survey of which 16 had been monitored during the 1986 survey. The remaining 7 sites were based on moorland in mid-Wales within map squares for which critical loads for soil acidification are expected to be exceeded by the year 2005. All sites were chosen so as to be remote from major local sources of NO(2) and the values obtained were deemed to be minimum concentrations for the different regions. Measurements were made using diffusion tubes which aimed to provide mean concentrations of NO(2) for 2-week exposure periods. Concentrations of NO(2) were found to be higher in the winter months for most sites and this is probably related to a greater use of fossil fuels for heating buildings at this time of year. The exception was the high concentrations of NO(2) in May and June for several sites in North Wales, and in July and August for a site on Mount Snowdon. These high summer concentrations in North Wales are thought to be related to increased traffic associated with tourism. It is apparent that there has been a substantial increase in rural concentrations of NO(2) throughout Wales since the earlier survey of 1986. As an average of all 16 sites used in both surveys, there was a 53% increase in the annual mean concentration of NO(2). Also, it is evident that, since 1986, there has been a substantial increase in the area of south-eastern Wales which has a background level in excess of 10 ppb NO(2) and a notable reduction in land area with concentrations below 6 ppb NO(2) as an annual mean concentration. The possible future impact of increasing rural concentrations of NO(2) on Welsh vegetation is discussed with references to estimates of critical levels of NO(2) for adverse effects on plants.     

Seasonal variation of black carbon aerosols over a tropical urban city of Pune,India

Black carbon (BC) aerosols were monitored continuously at Pune, a tropical urban location in southwest India, using aethalometer AE-42 model. Results of the data for the 1-year period (January to December 2005) have been discussed here. Seasonal and diurnal variations of BC in relation to changes in the regional meteorological conditions and local boundary layer characteristics have been studied along with the mass fraction of BC to the total suspended particulates (TSP) in different months. Also, using the Hysplit model, back-trajectories are studied to assess the sources for transported BC particles. The data collected during January to December 2005 indicated that annual average BC concentration (4.1 μg m⁻³) at Pune was comparable to that reported for other urban locations in southern Indian region. During winter season, BC concentrations were maximum (about 80% more than annual mean), mainly due to prevailing meteorological conditions like low wind speeds and low ventilation coefficients; as well as due to the transport from northeast regions. Minimum BC concentrations were observed during monsoon season (about 68% less than annual mean), which could be attributed to the wash-out effects due to precipitation as well as due to southwesterly winds coming from marine areas. Diurnal variation of BC showed two peaks, one in morning and another in the evening, which are mostly related to the daily changes in the local boundary layer. However, the intensity of local traffic emissions could have some impact on the magnitude of these peaks. BC aerosols formed about 2.3% of the total aerosol mass fraction at Pune.     

Seasonal evolution of gas-phase PCB concentrations in the Venice Lagoon area

The concentrations of gas-phase PCBs were measured from March 2002 to June 2003 at two sites of the Venice Lagoon and at one site of the Euganei hills. The aims of this study were to evaluate the various gas-phase PCB sources, the spatial and temporal variability of PCB concentrations in the gas-phase that enter the Venice Lagoon atmosphere and the influence of the air temperature on PCB trends. The highest annual average concentration of summation PCBs was observed at the station directly influenced by "urban" sources with values about 3 and 1.5 times higher compared to the concentrations found at the stations where "marine" sources and "not subjected to direct local sources" were respectively sampled from. The temporal trends of summation PCBs concentrations were similar at the three sampling stations corresponding to seasonal temperature changes. Greater concentrations occurred in the summer and first autumn months while the lower ones occurred in late autumn and winter. The temperature dependences were investigated using plots of the natural logarithm of the summation PCBs concentrations vs. reciprocal mean temperatures.     

Trend and seasonal variation of precipitation chemistry data in the Netherlands

A multiple regression model is introduced to describe temporal variations in precipitation chemistry data. The model considers the effects of the annual cycle, a linear trend and precipitation-quantity simultaneously. The paper discusses the application of the model to concentrations and depositions of hydronium, ammonium, nitrate and sulfate for monthly bulk samples in The Netherlands for the period 1978–1984.Statistical conclusions about the annual cycle and the trend are hardly influenced by the choice of the dependent variable (depositions, concentrations or logarithms of concentrations). With the exception of H⁺ concentrations, a large part of the temporal variations was due to precipitation-quantity effects. Significant annual cycles were found for nitrate, ammonium and sulfate. There was statistical evidence of a downward trend for sulfate and nitrate. A complex, non-linear trend was observed for H⁺ which resulted in a significant autocorrelation of the residuals from the regression equation.Much attention is paid to the detectability of trend. For ammonium, nitrate and sulfate it is possible to discriminate small systematic changes in quite short records (a mean annual change of 4–6% in a 5-year record). This is not the case for H ⁺, because temporal variations of this component are insufficiently explained by the systematic annual cycle and precipitation-quantity.     

Source apportionment of airborne particulate matter using organic compounds as tracers

A chemical mass balance receptor model based on organic compounds has been developed that relates source contributions to airborne fine particle mass concentrations. Source contributions to the concentrations of specific organic compounds are revealed as well. The model is applied to four air quality monitoring sites in southern California using atmospheric organic compound concentration data and source test data collected specifically for the purpose of testing this model. The contributions of up to nine primary particle source types can be separately identified in ambient samples based on this method, and approximately 85% of the organic fine aerosol is assigned to primary sources on an annual average basis. The model provides information on source contributions to fine mass concentrations, fine organic aerosol concentrations and individual organic compound concentrations. The largest primary source contributors to fine particle mass concentrations in Los Angeles are found to include diesel engine exhaust, paved road dust, gasoline-powered vehicle exhaust, plus emissions from food cooking and wood smoke, with smaller contribution from tire dust, plant fragments, natural gas combustion aerosol, and cigarette smoke. Once these primary aerosol source contributions are added to the secondary sulfates, nitrates and organics present, virtually all of the annual average fine particle mass at Los Angeles area monitoring sites can be assigned to its source.     

Rural ozone in the southeastern United States

Ozone measurements are reported for five rural sites in the Tennessee Valley region of the southeastern U.S. for periods ranging from 18 to 83 months during the years 1977 through 1984. Rural ozone (O₃) levels were found to equal or exceed urban values for the same region. The daily maximum 1-h average concentration was found to peak during the summer months, while the 24-h average concentrations were greatest in the spring. The annual cycle of daily maximum concentrations is related to the seasonal photochemical cycle. The annual cycle in 24-h average concentrations is best explained by the combined effects of the annual cycles in solar intensity and noctural O₃ depletion. There was no indication that stratospheric intrusions exhibited a significant influence on the annual O₃ cycles. Evidence was found for elevated O₃ levels during touchdown of plumes from large power plants. No long-term trend in rural O₃ concentrations, either daily maxima or means, was discernible.     

Mobile source emission inventories--monthly or annual average inputs to MOBILE6?

In many urban areas, on-road vehicles are the biggest contributing source category of volatile organic compounds (VOCs) and nitrogen oxides (NOx). Based on a recently completed emission inventory study for three counties in central Florida, the major source by far of anthropogenic VOCs and NOx was on-road mobile sources, even though other sources (such as construction equipment, lawn and garden equipment, and various point sources) were also significant. Although there is specific guidance for conducting an ozone-season inventory for mobile sources, there is a lack of detailed guidance as to how to employ the U.S. Environmental Protection Agency's (EPA) latest mobile source emission factor program, MOBILE6, for an annual inventory. Several of the MOBILE6 inputs that significantly influence emission factors (e.g., temperature) can vary widely throughout the year, and the annual average value may not be appropriate. Rather, it may be better to utilize monthly values of these parameters. This paper investigated the sensitivity of the annual emission inventory results to using annual or monthly values of temperature, Reid Vapor Pressure of gasoline, and humidity. The results show that, for a three-county area in central Florida representing metropolitan Orlando, the annual emission inventory based on the sum of individual monthly averages is not significantly different from that calculated using one set of annual average inputs to MOBILE6.     

Abundance and sources of ambient dioxins in Hong Kong: a review of dioxin measurements from 1997 to 2001

Ambient measurements of seventeen 2,3,7,8-polychlorinated dibenzo-p-dioxin/dibenzofuran congeners (2,3,7,8-PCDD/Fs) have been taken in a number of monitoring programs or ad-hoc studies in Hong Kong. The longest monitoring program started at two locations in the territory in July 1997. The other monitoring efforts are ad-hoc studies, varying from a few coordinated sampling events at multiple sites to a year-long monitoring project that targeted suspected local dioxin sources. In this paper, we examined these measurements to understand the ambient levels, temporal and spatial variation, and possible sources of the 2,3,7,8-PCDD/Fs in Hong Kong. The territory-wide annual average concentration of the dioxins was 0.052 pg I-TEQ/m3 measured at the regular monitoring stations in the most recent annual cycle of 2000/2001. This level fell at the lower end of the range of dioxin concentrations measured at other urban locations around the world. The dioxin levels showed a clear seasonality in that elevated concentrations were observed in the winter and lower concentrations in the summer at all monitoring sites with one year or more regular measurements. The measurements indicated that the few known local dioxin sources, including a major chemical waste incinerator facility, landfill sites, and vehicular traffic, are not important contributors to ambient dioxins in Hong Kong. On days of high dioxin concentrations, the 2,3,7,8-PCDD/F congeners were observed to have almost identical compositions with a north-northwest to south-southeast spatial gradient in concentrations at different sampling locations in Hong Kong. This observation, along with other collaborative evidence, established a strong link between high dioxin concentration days in Hong Kong and regional transport of the polluted air masses from the north.     

Pollution Abatement Energy Usage of Gas Treating and Processing Plants

The body of information presented in this paper is directed to individuals dealing with energy distribution and environmental issues. Production of natural gas demands energy for abatement of air pollutants. Perspective of energy requirements for natural gas production is presented by analysis of a survey of about 20% of the operating gas plants in Texas. The variation of fuel requirements for production is determined for inlet gas streams with increasing concentrations of toxic contaminants. Then the energy requirements of specific abatement devices is presented and the resultant cost of preparing natural gas for distribution is outlined. The average abatement energy requirement is 1.5% of the total energy requirement for gas processing or consumption of less than 0.1 % of the marketed production of natural gas.     

Real-time indoor and outdoor measurements of black carbon in an occupied house: an examination of sources

Black carbon (BC) was measured every 5 min for two years (May 1998-May 2000) inside and immediately outside a northern Virginia house (suburban Washington, DC) occupied by two nonsmokers. Two aethalometers, which measure BC by optical transmission through a quartz fiber tape, were employed indoors and outdoors. Meteorological parameters were obtained on an hourly basis from nearby Dulles airport. Indoor activities were recorded to identify indoor sources such as combustion activities, which occurred 9% of the time during the first year and 4% of the time during the second year. At times without indoor sources, indoor/outdoor BC ratios averaged 0.53 in the first year and 0.35 in the second year. The main outdoor source of BC was the general regional background, contributing 83-84% of the total during each of the two years. Morning rush hour traffic contributed 8-9% of the total BC. An evening peak in the fall and winter, thought to include contributions from wood burning, was responsible for approximately 8% of the annual average BC concentration. The main indoor sources of BC were cooking and candle burning, contributing 16 and 31%, respectively, of the annual average indoor concentrations in the two years. Relative humidity (RH) affected the outdoor aethalometer in both years. An artifact associated with the tape advance was noted for the aethalometer, but a correction factor was developed that reduced the associated error by a factor of 2.     

Long-term trends and spatial variability in nitrate leaching from alpine catchment-lake ecosystems in the Tatra Mountains (Slovakia-Poland)

Relationships between catchment characteristics of 31 alpine lakes and observed trends in lake water concentrations of nitrate were evaluated in the Tatra Mountains. Nitrate concentrations increased from background levels <4 microeql(-1) in the 1930s to maxima (up to 55 microeql(-1)) in the 1980s, after which they declined to 4-44 microeql(-1) by the late 1990s. In-lake nitrate concentrations correlated negatively with parameters characterising catchment-weighted mean pools (CWM; kgm(-2)) of soil, i.e. with percent land cover with meadow and soil depth, and positively with grade of terrain, annual precipitation, and the highest elevation in the catchment. The CWM pool of soil and annual precipitation explained together 65% of the current spatial variability in nitrate concentrations. Denitrification and direct N deposition on surface area explained 14% of the variability. Increased atmospheric N deposition and declining net N retention in soils were responsible for long-term changes in nitrate concentrations. Long-term decline in %N retention in soils decreased along with the estimated decline in C:N ratios (from 21 to 18 on average during the last 70 years). An empirical model linking nitrate concentrations in different types of alpine Tatra Mountain lakes to four independent variables (CWM soil pool, annual precipitation, increased N deposition, and average trend in soil C:N ratios) explained 80% of the observed spatial and temporal nitrate variability over the period 1937-2000.     

The effects of land use change on mercury distribution in soils of Alta Floresta, Southern Amazon

This study presents the spatial distribution, degree of contamination and storage capacity of Hg in surface forest and pasture soils from Alta Floresta, Southern Amazon, a significant gold mining site from 1980 to 1996. During that period, average annual gold production was about 6.5 tons, with an estimated Hg annual emission to the environment of about 8.8 tons, 60-80% of it being emitted to the atmosphere. Mercury sources to the region are mining sites and gold-dealer shops at the city of Alta Floresta, where gold is smelted and commercialized. Mercury concentrations in forest soils (15-248 ng g(-1), average=61.9 ng g(-1)) were 1.5-3.0 times higher than in pasture soils (10-74 ng g(-1), average=33.8 ng g(-1)), suggesting strong re-mobilization after deforestation. Highest Hg concentrations were found within a distance of 20-30 km from mining sites in both soil types. The influence of the refining operations within the city of Alta Floresta, however, was less clear. Somewhat higher concentrations were observed only within a 5 km radius from the city center where gold-dealer shops are located. Wind direction controls the spatial distribution of Hg. Background concentrations (15-50 ng g(-1)) were generally found at the outer perimeter of the sampling grid, about 40 km from sources. This suggests that Hg released from mining and refining activities undergoes rapid deposition. Estimated cumulative Hg burdens for the first 10 cm of soil averaged 8.3 mg m(-2) and 4.9 mg m(-2), for forest and pasture soils respectively and compare well with ultisols and hydromorphic oxisols, but were lower than those found in yellow-red and yellow latosols and podsols from other Amazonian areas. Our results show that changing land use in the Amazon is a strong re-mobilizing agent of Hg deposited on soils from the atmosphere.     

The Release of Methyl Chloride from Biomass Burning in Australia

Abstract

Black carbon (BC) was measured every 5 min for two years (May 1998–May 2000) inside and immediately outside a northern Virginia house (suburban Washington, DC) occupied by two nonsmokers. Two aethalometers, which measure BC by optical transmission through a quartz fiber tape, were employed indoors and outdoors. Meteorological parameters were obtained on an hourly basis from nearby Dulles airport. Indoor activities were recorded to identify indoor sources such as combustion activities, which occurred 9% of the time during the first year and 4% of the time during the second year. At times without indoor sources, indoor/outdoor BC ratios averaged 0.53 in the first year and 0.35 in the second year.

The main outdoor source of BC was the general regional background, contributing 83–84% of the total during each of the two years. Morning rush hour traffic contributed 8–9% of the total BC. An evening peak in the fall and winter, thought to include contributions from wood burning, was responsible for ~8% of the annual average BC concentration. The main indoor sources of BC were cooking and candle burning, contributing 16 and 31%, respectively, of the annual average indoor concentrations in the two years. Relative humidity (RH) affected the outdoor aethalometer in both years. An artifact associated with the tape advance was noted for the aethalometer, but a correction factor was developed that reduced the associated error by a factor of 2.