Annual Average Concentrations Of SO2 Research Articles

Association of SO2/CO exposure and greenness with high blood pressure in children and adolescents: A longitudinal study in China.

We aimed to investigate the association between greenness around schools, long-term gaseous air pollution exposure (SO2 and CO), and blood pressure in children and adolescents. From 2006 to 2018, a total of 219,956 Chinese children and adolescents aged 7-17 years in Beijing and Zhongshan were included in this longitudinal study. Annual average concentrations of SO2 and CO and the mean values of normalized difference vegetation index around schools were calculated. We used the generalized estimation equation model, restricted cubic spline model, and Cox model to analyze the health effects. Among all the subjects, 52,515 had the first onset of HBP. During the follow-up, HBP's cumulative incidence and incidence density were 23.88% and 7.72 per 100 person-year respectively. Exposures to SO2 and CO were significantly associated with SBP [β = 1.30, 95% CI: (1.26, 1.34) and 0.78 (0.75, 0.81)], DBP [β = 0.81 (0.79, 0.84) and 0.46 (0.44, 0.48)] and HBP [HR = 1.58 (1.57, 1.60) and 1.42 (1.41, 1.43)]. The risks of HBP attributed to SO2 and CO pollution would be higher in school-aged children in the low greenness group: the attributable fractions (AFs) were 26.31% and 20.04%, but only 13.90% and 17.81% in the higher greenness group. The AFs were also higher for normal-BMI children and adolescents in the low greenness group (AFs = 30.90% and 22.64%, but 14.41% and 18.65% in the high greenness group), while the AFs were not as high as expected for obese children in the low greenness group (AFs = 10.64% and 8.61%), nor was it significantly lower in the high greenness group (AFs = 9.60% and 10.72%). Greenness could alleviate the damage effects of SO2/CO exposure on the risks of HBP among children and adolescents, and the benefit is BMI sensitivity. It might offer insights for policymakers in making effective official interventions to prevent and control the prevalence of childhood HBP and the future disease burden caused by air pollution.

Evaluation of different control measures in 2014 to mitigate the impact of ship emissions on air quality in the Pearl River Delta, China

Various control measures have been proposed to reduce ship emissions. However, improvements in air quality after its implementation have rarely been evaluated on a regional scale. To fill this gap, this study employed the Weather Research and Forecast model coupled with Chemistry (WRF/Chem) model to investigate the improvement in air quality under scenarios separately implementing different control measures. The domestic emission control area (DECA) in the Pearl River Delta (PRD) region of China was selected as the target area for the study. The results suggest that the use of cleaner fuels is a promising way to improve air quality. For vessels sailing in the DECA, using 0.5% sulfur-content fuel could reduce SO2 and PM2.5 by 0.52 μg/m3 and 1.43 μg/m3, respectively, in the target cities of PRD, while 0.1% sulfur-content fuel could increase these figures to 0.59 μg/m3 and 1.62 μg/m3, respectively. The use of liquefied natural gas (LNG) fuel was predicted to be the most effective method for air quality improvement. LNG fuel could reduce the annual average concentrations of SO2, NO2 and PM2.5 by 0.63 μg/m3, 2.80 μg/m3 and 2.14 μg/m3, respectively, in the target cities of PRD. The application of shore side electricity (SSE) would reduce the ship-contributed SO2 and PM2.5 by 0.33 μg/m3 and 1.06 μg/m3, respectively. For the NOX control, the retrofit of the selective catalytic reduction (SCR) system could reduce the ambient concentrations of NO2 and PM2.5 by 2.09 μg/m3 and 0.15 μg/m3, respectively. These results suggest that the use of cleaner fuels and the retrofit SCR system all have positive effects on lowering the impact of ship emissions, while the application of SSE could be a useful supplement.

Origin and Background Estimation of Sulfur Dioxide in Ulaanbaatar, 2017

Particulate matter studies have been conducted regularly in the capital city of Mongolia. In contrast, studies related to the source and general estimation of levels of sulfur dioxide (SO2) over whole years are lacking. To explore the yearly trend in SO2, whole-year data of air pollutants were obtained from the Air Pollution Reducing Department. The results showed that the annual average concentration of SO2 was 32.43 µg/m3 at the Amgalan official monitoring station in 2017, which changed from 53 µg/m3 in 2016, representing a reduction of around 40%. The back-trajectory model and the National Oceanic and Atmospheric Administration (NOAA)’s hybrid single particle Lagrangian integrated trajectory model (HYPSLIT) were used to determine the source of SO2. A total of 8760 backward trajectories were divided into eight groups. The results showed that 78.8% of the total trajectories in Ulaanbaatar came from an area inside Mongolia. The results showed that pollutants enter Ulaanbaatar mainly from the northwest and north during the winter season. There are industrial cities, such as Darkhan and Sukhbaatar, in North Mongolia. Air pollutants created in the industrial area traveled into Ulaanbaatar during the winter season.

Temporal dynamics of SO2 and NOX pollution and contributions of driving forces in urban areas in China

SO2 and NOX pollution have significantly reduced the air quality in China in past decades. Haze and acid rain have negatively affected the health of animals, plants, and human beings. Documented studies have shown that air pollution is influenced by multiple socioeconomic driving forces. However, the relative contributions of these driving forces are not well understood. In this study, using the structural equation model (SEM), we quantified the contributing effects of various forces driving air pollution in 2015 in prefecture-level cities of China. Our results showed that there has been significant control of SO2 pollution in the past 20 years. The annual average SO2 concentration has dropped from 83 μg/m3 in 1996 to 21 μg/m3 in 2015, while the annual average NOX concentration has increased from 47 μg/m3 in 1996 to 58 μg/m3 in 2015. We evaluated data on the annual average concentrations of SO2, which in some cities may mask the differences of SO2 concentrations between different months. Hence, SO2 pollution should continue to be controlled in accordance with existing policies and regulations. However, we suggest that NOX should become the new focus of air pollution prevention and treatment. The SEM results showed that industrial scale, city size, and residents’ activities have a significant impact on NOX pollution. Among these, industrial scale had the highest contribution. The findings from our study can provide a theoretical basis for the formulation of NOX pollution control policy in China.

近年来贵阳市大气环境质量的演变特征及其与污染源排放的关系

本研究通过整理2008~2014年《贵阳市环境状况公报》中的空气质量及污染物排放量数据，运用时间序列分析法和相关性分析法研究2008~2014年贵阳市大气质量的演变特征，并分析大气中污染物浓度与其排放源强的相关性。结果显示近7年来贵阳市空气环境中的SO2年平均浓度逐渐降低，NO2年平均浓度逐渐增加，除2013年外PM10波动不大；SO2浓度降低可能与产业结构优化有关，NO2则主要受到机动车尾气排放的影响，而PM10的影响因素较为复杂；空气质量变化可分为两个阶段：2008~2012年空气质量优良率保持在94% ± 1%的水平，空气质量较好且较为稳定，第二阶段为2013~2014年，空气质量有一定程度下降；大气污染物年平均浓度和相应年份的排放量具有很好的相关性，相关程度主要受到地形和污染物粒径大小的影响。 The data of atmosphere pollutant concentration and its emission load from the Guiyang City Envi-ronment Gazette were selected during 2008-2014, and the contamination characteristics of PM10, SO2, NO2 were analysed by the time-sequential approach, together with correlation analysis was used to assess the interaction between pollutant concentration in air and its emission. Results showed that the annual average concentration of SO2 gradually reduced, and the NO2 gradually in-creased, PM10 had small fluctuations except the 2013 year. The reducing SO2 concentrations may be associated with the industrial structure optimization, the increasing NO2 concentration is mainly influenced by exhaust emissions of motor vehicle, and the impact factors of PM10 is more compli-cated. The changes of air quality could be divided into two stages during 2008-2014. Air quality was more stable and comfortable during 2008-2012, the good rate of which maintained at 94% ± 1% level. The air quality had partly decreased in the second stage during 2013-2014. The emissions of pollutants play a key role in controlling atmospheric pollutants’ concentrations, which is mainly influenced by terrain and pollutant particle size.

Development of a Fuzzy Pattern Recognition Model for Air Quality Assessment of Howrah City

The district of Howrah is one of the most highly industrialized districts in West Bengal, India. Howrah City continues to suffer from poor ambient air quality due to the dense siting of small scale industries without air pollution management, huge traffic congestion and high levels of human settlement. This paper presents the trends of air pollution concentration (O3, CO, SO2, NO2, and PM10) in Howrah City, and also demonstrates a new methodology for air quality assessment using an AHP coupled fuzzy pattern recognition model. The annual average of PM10 concentration has decreased from 2009 (185.57 ± 121.16 µg/m3) to 2011 (160.01 ± 117.32 µg/m3). A similar trend was observed for the CO concentration. The eight-hour average concentration of CO in 2011 (0.939 ± 0.632 mg/m3) was found to be lower than that in 2009 (1.59 ± 0.72 mg/m3), while the reverse trend was observed for SO2 and NO2. The annual average concentration of SO2 increased from 2009 (17.68 ± 20.92 µg/m3) to 2011 (43.048 ± 31.47 µg/m3). The annual average concentration of NO2 increased from 2009 (63.87 ± 39.73 µg/m3) to 2011(78 ± 61.51 µg/m3). There was no uniform trend observed in the annual the eight-hour average concentration of ozone. An approach was developed in this study to determine fuzzy air quality based on the observed air pollution concentration. This will help to identify the air pollution control measures that are required in a certain area. The proposed method is a multi-pollutant aggregation method with varying weighting, and has the capability to consider subjective factors like sensitivity and population density. The concentrations of the five air pollutant parameters (O3, CO, SO2, NO2, and PM10) were used to develop the model for air quality assessment.

Ozone Monitoring Instrument Observations of Interannual Increases in SO2 Emissions from Indian Coal-Fired Power Plants during 2005–2012

Due to the rapid growth of electricity demand and the absence of regulations, sulfur dioxide (SO2) emissions from coal-fired power plants in India have increased notably in the past decade. In this study, we present the first interannual comparison of SO2 emissions and the satellite SO2 observations from the Ozone Monitoring Instrument (OMI) for Indian coal-fired power plants during the OMI era of 2005-2012. A detailed unit-based inventory is developed for the Indian coal-fired power sector, and results show that its SO2 emissions increased dramatically by 71% during 2005-2012. Using the oversampling technique, yearly high-resolution OMI maps for the whole domain of India are created, and they reveal a continuous increase in SO2 columns over India. Power plant regions with annual SO2 emissions greater than 50 Gg year(-1) produce statistically significant OMI signals, and a high correlation (R = 0.93) is found between SO2 emissions and OMI-observed SO2 burdens. Contrary to the decreasing trend of national mean SO2 concentrations reported by the Indian Government, both the total OMI-observed SO2 and annual average SO2 concentrations in coal-fired power plant regions increased by >60% during 2005-2012, implying the air quality monitoring network needs to be optimized to reflect the true SO2 situation in India.

Study on the Countermeasures of SO<sub>2</sub> Emission Reduction in Chengdu Economic Circle

Based on a detailed survey on the source and volume of SO2 emission over Chengdu economic circle, the third-generation air quality model CMAQ is adopted for simulating the concentration of SO2 in the air over Chengdu Economic Circle. The results show that the hourly average concentration, daily average concentration and annual average concentration of SO2 in air exceed the limit of national standard, and the affected areas respectively account for 0.12%, 0.18% and 0.03% of the total area of the economic circle. Meanwhile, according to the result of calculation, the SO2 emissions of thermal power plants, chemical industry, building materials plants and industrial area sources make the largest contribution to the SO2 concentration in the air, with ratios of 36.15%, 18.67%, 11.81% and 8.34% respectively. thus,main measures to reduce emissions of SO2 in Chengdu economic circle are proposed as follows: focusing on the control of the emissions of SO2 from industrial enterprises, especially in the thermal power plants, chemical industry, building materials plants as well as industrial boilers; joint prevention and control measures should be implemented between the cities, so as to reduce the interaction caused dy emissions of SO2. With the application of the above measures, the total SO2 emissions can be reduced by 50% and the concentration of SO2 in the air can meet with the Class II of national ambient air quality Standard.

Current status and future trends of SO2 and NOx pollution during the 12th FYP period in Guiyang city of China

In order to investigate the future trends of SO2 and NOx pollution in Guiyang city of China, the MM5/CALMET/CALPUFF modeling system is applied to assess the effects of air pollution improvement that would result from reduction targets for SO2 and NOx emissions during the 12th Five-Year Plan (2011–2015). Three scenarios are established for the objective year 2015 based on the reference emissions in base year 2010. Scenario analysis and modeling results show that emissions are projected to increase by 26.5% for SO2 and 138.0% for NOx in 2015 Business-As-Usual (BAU) relative to base year 2010, respectively, which will lead to a substantial worsening tendency of SO2 and NOx pollution. In comparison, both the 2015 Policy Reduction (PR) and 2015 Intensive Policy Reduction (IPR) scenarios would contribute to improve the urban air quality. Under 2015 PR scenario, the maximum annual average concentration of SO2 and NOx will reduce by 54.9% and 31.7%, respectively, relative to the year 2010, with only 2.1% of all individual gridded receptors exceed the national air quality standard limits; while the maximum annual average concentrations of SO2 and NOx can reduce further under 2015 IPR scenario and comply well with standards limits. In view of the technical feasibility and cost-effectiveness, the emission reduction targets set in the 2015 PR scenario are regarded as more reasonable in order to further improve the air quality in Guiyang during the 12th FYP period and a series of comprehensive countermeasures should be effectively implemented.

Long-term exposure to gaseous air pollutants and cardio-respiratory mortality in Brisbane, Australia

This study examines the association of long-term exposure to gaseous air pollution with cardio-respiratory mortality in Brisbane, Australia, in the period 1996-2004. The pollutant concentrations were estimated using geographical information system (GIS) techniques at the statistical local area (SLA) level. The generalized estimating equations model was used to investigate the impact of nitrogen dioxide (NO2), ozone (O3) and sulphur dioxide (SO2) on mortality due to cardio-respiratory disease after adjusting for a range of potential confounders. An increase of 4.7% (95% confidence interval = 0.7-8.9%) in cardio-respiratory mortality for 1 part per billion (ppb) increment in annual average concentration of SO2 was estimated. However, there was no significant association between long-term exposures to NO2 or O3 and death due to cardio-respiratory disease. The results indicate that the annual average concentration of SO2 is associated with cardio-respiratory mortality at the SLA level and this association appears to vary with the geographical area.

Health Impact of Outdoor Air Pollution in China: Current Knowledge and Future Research Needs

Outdoor air pollution is one of China’s most serious environmental problems. Coal is still the major source of energy, constituting about 75% of all energy sources. Consequently, air pollution in China predominantly consists of coal smoke, with suspended particulate matter (PM) and sulfur dioxide (SO2) as the principal air pollutants. In large cities, however, with the rapid increase in the number of motor vehicles, air pollution has gradually changed from the conventional coal combustion type to the mixed coal combustion/motor vehicle emission type. Currently, inhalable particles (PM <10 μm in aerodynamic diameter; PM10), SO2, and nitrogen dioxide (NO2) are the criteria pollutants of concern in China. Generally, PM levels in cities in the north are higher than those in the south, whereas SO2 and NO2 levels do not differ much. In 2004, the annual average PM10 concentrations for major Chinese cities were 102 μg/m3 in southern cities, 140 μg/m3 in northern cities, and 121 μg/m3 in cities nationwide. The annual average concentrations of SO2 and NO2 nationwide were 66 μg/m3 and 38 μg/m3, respectively (China State Environmental Protection Agency 2005). Although its ambient air quality has improved substantially, China is still facing the worst air pollution problem in the world. Outdoor air pollution has become a major concern for public health. The World Bank (2007) estimated that the total health cost associated with outdoor air pollution in urban areas of China in 2003 was between 157 and 520 billion Chinese yuan, accounting for 1.2–3.3% of China’s gross domestic product. Health end points studied in China in association with air pollution include all-cause mortality, mortality and morbidity due to cardiopulmonary disease, and numbers of outpatient and emergency department visits (Chen et al. 2004). Changes in respiratory and other clinical symptoms, lung function, and immune function are also studied. Dozens of time-series studies have been conducted in large Chinese cities, including Beijing, Shanghai, Chongqing, Shenyang, Wuhan, and Taiyuan, to assess the association of short-term exposure to air pollution with mortality or morbidity (Chen et al. 2004). Mortality or morbidity risk estimates per unit increase in air pollution level among Chinese populations are generally similar in magnitude to risks estimated in other parts of the world. A recent multicity time-series analysis in Hong Kong, Shanghai, and Wuhan provided further evidence of short-term risks (Wong et al. 2008), with significant health effects detected at air pollution levels below minimum air quality standards in China. Currently, a new national-level air pollution time-series study, the China Air Pollution and Health Effects Study (CAPES), is under way. In addition, several ongoing panel studies are examining associations between air pollution and subclinical health outcomes before, during, and after the 2008 Summer Olympic Games in Beijing. These panel studies should provide a unique opportunity to assess the public health benefits of air pollution reduction in a city where air pollution levels have been high. Relatively few studies have examined long-term effects of air pollution in China. Several prospective cohort studies in North America and Europe have estimated effects of long-term exposure to air pollution on mortality (Pope and Dockery 2006), but it is not clear whether the findings from developed countries apply to China, given differences in the levels and characteristics of air pollution, and in sociodemographic characteristics. So far, there has been no cohort study of air pollution in China, but results of cross-sectional analyses in Beijing, Shenyang, and Benxi have suggested that long-term exposure to air pollution is associated with increased mortality (Chen et al. 2004). However, results of these analyses are difficult to interpret because of the lack of information on potential confounders. In short, there is sufficient evidence that exposure to outdoor air pollution is a health hazard in China. The importance of these increased health risks is greater than in developed countries because air pollution in China is at much higher levels and because the Chinese population accounts for more than one-fourth of the world’s total population. Most of the Chinese studies discussed above were ecologic in nature, thus limiting their power for causal inference. Future research will need to clarify the lifetime course of air pollution effects with full control of potential confounders (e.g., prospective cohort studies), examine the relevance of cumulative exposures, disentangle effects of multiple pollutants, investigate gene–environment inter actions and other factors that may modify air pollution health effects, and identify pathophysiologic links between air pollution and health hazards for the Chinese population. Finally, pollution needs to be reduced and air quality and health indicators need to be monitored; this will enable the people and relevant authorities to be aware of the trends and consequences of air pollution, so they can determine how to ameliorate the situation.

Trends in Air Pollution During 1996 - 2003 and Cross-Border Transport in City Clusters Over the Yangtze River Delta Region of China

Air quality data from city clusters in the fast developing Yangtze River Delta (YRD) region of China during 1996 - 2003 were analyzed, with a cross-border transport study using the Regional Acid Deposition Model System (RegADMS). Investigations show that the annual average concentrations of SO2, NO2, PM10 are 12 ~ 64 , 13 ~ 57, and 79 ~ 184 µg m 3 − , respectively. As the primary air pollutants in the target area, surface NO2 levels increased by 13% while PM10 levels decreased by 39% from 1996 to 2003. The surface SO2 concentration showed fluctuations during the study period, reaching a minimum in 1999 and rising again in 2003. Acid rain still remains an important atmospheric environmental issue. The frequency of acid rain was about 23.5 ~ 36.7%, and the pH value of precipitation ranged from 5.09 to 5.48, with little change in these years. Modeling studies indicated that sulfur deposition and nitrogen deposition were in the ranges 0.5 ~ 10 and 0.2 ~ 5 g m -2 yr -1 , respectively; these levels exceed the critical load in some regions. The trans-boundary transport of sulfur deposition and nitrogen deposition due to SO2 and NOx emission among city clusters (Shanghai and the other 8 cities in Jiangsu Province, including Nanjing, Wuxi, Changzhou, Suzhou, Nantong, Yangzhou, Zhenjiang, and Taizhou) in the YRD region was significant. The emission from Shanghai contributes 5% ~ 29% of sulfur deposition and 3% ~ 30% of nitrogen deposition

Air Quality Status of an Open Pit Mining Area in India

This investigation presents the assessment of ambient air quality carried out at an open pit coal mining area in Orissa state of India. The 24-h average concentrations of suspended particulate matter (SPM), respirable particulate matter (RPM, particles of less than 10 microm aerodynamic diameter), sulphur dioxide (SO2) and oxides of nitrogen (NO(x)) were determined at regular interval throughout one year at 13 monitoring stations in residential area and four stations in mining/industrial area. During the study period, the 24-h and annual average SPM and RPM concentrations exceeded the respective standards set in the Indian ambient air quality standard (NAAQS) protocol in most of the residential and industrial areas. However, the 24-h and annual average concentrations of SO2 and NO(x) were well within the prescribed limit of the NAAQS in both residential and industrial areas. A management strategy is formulated for effective control of particulate matter at source and other mitigative measures are recommended including implementation of green belts around the sensitive areas.

Outdoor air pollution and lung cancer: recent epidemiologic evidence.

Outdoor air pollution and lung cancer: recent epidemiologic evidence.

Air quality standard exceedance and management in an Indian mining area

Detailed studies are essential in India to evaluate air quality and implement measures for effective control of mining in sensitive locations. A study for this purpose was carried out in the Basundhara area of the Ib Valley coalfield in Orissa State, India. The 24-hr average concentrations of suspended particulate matter (SPM), respirable particulate matter (RPM), sulphur dioxide (SO2) and oxides of nitrogen (NOx) were determined at regular intervals throughout one year at seven monitoring stations in residential areas and two stations in mining/industrial areas. The 24-hr average SPM and RPM concentrations were 312.7–598.4 μg m−3 and 100.2–199.6 μg m−3 in industrial areas, and were 95.6–275.7 μg m−3 and 28.5–86.8 μg m−3 in residential areas. During the study period, 24-hr and annual average SPM and RPM concentrations exceeded the respective standards set in the Indian national ambient air quality standard (NAAQS) protocol in certain residential and industrial areas. However, 24-hr and annual average concentrations of SO2 (residential: 20.5–24.3 μg m−3, industrial: 15.3–30.8 μg m−3) and NOx (residential: 19.7–25.3 μg m−3, industrial: 14.3–33.5 μg m−3) were well within the prescribed limit of the NAAQS in both residential and industrial areas. The temporal variations of SPM and RPM fitted polynomial trends well and on average in the mining area 31.38% of the SPM was RPM. The linear regression correlation coefficients between SPM and RPM and between NOx and SO2 were 0.90 and 0.52, respectively. The kriging technique determined that maximal concentrations of SPM and RPM occurred within the mining site. A management strategy is formulated for effective control of air pollution at source, and mitigative measures should include implementation of green belts around the sensitive areas where the concentration of air pollutants exceeds the standard limit.

Long‐term SO2 dispersion modeling over a coastal region

Air dispersion modeling over coastal regions has proven to be a remarkable challenge in the field of air quality. Many conventional plume dispersion models, such as ISC2 and HYSPLIT, are unable to model such dispersion with the precision that is necessary to accurately predict ground‐level concentrations in coastal areas. Considering this, the present work was carried out with two primary objectives: i) to evaluate the effectiveness of currently available mathematical models in predicting plume dispersion over a coastal region and ii) to study the impact of sulfur dioxide emissions from a petroleum refinery over a different community located in the adjacent area. This study demonstrates that CALPUFF predictions are more reliable compared to those of the other models studied, however the operation of CALPUFF is highly data intensive and in many instances, it is difficult to obtain all required input data. This is a particular problem for regions outside of the United States of America where sufficient data is difficult to obtain. In addition, the study concluded that the predicted annual average SO2 concentrations in the nearby communities are well within regulatory limits

Specifics and Temporal Changes in Air Pollution in Areas Affected by Emissions from Oil Shale Industry, Estonia

Atmospheric air pollution levels and long-term effects on the environment caused by simultaneous presence of SO2 and oil shale alkaline fly ash during the last five decades (since 1950) were investigated. The annual critical value of SO2 for forest (20 µg m−3) was surpassed in 1% (∼35 km2) of the study area where the load was 30–40 µg m−3. No effect of long-term SO2 concentrations of up to 10–11 µg m−3 (0.5-h max up to 270 µg m−3) and simultaneous fly ash loads of up to 95 µg m−3 (1000 µg m−3) on the growth and needle longevity of Pinus sylvestris was established. The yearly deposition (average load up to 20–100 kg S ha−1) was alkaline rather than acidic due to an elevated base cation deposition in 1960–1989. Since 1990, the proportion of SO2 in the balance of components increased: about 70–85% of the total area was affected while the ratio of annual average concentrations of SO2 to fly ash was over 1. The limit values of fly ash for Sphagnum mosses and conifers in the presence of SO2 are recommended.

Low temperature so2 sampling by passive samplers in a northeastern Chinese industrialized area

Due to its reliability, simple and portable structure and low costs, the passive sampler is the ideal measuring device for developing countries. In spite of this, there has been no reporting on its reliability in extremely low temperate areas such as those associated with Northeastern China. The measuring of SO2 by passive samplers was attempted at extremely low temperatures in the heavy industrialized area of Shenyang, China from December 25 to 28,1995. The measurements associated with the passive sampler were accompanied by reference analysis utilizing conventional gas bubble sampling. The calibration equation generated from the parallel tests for the passive sampler at an extremely low temperature was 100×265×Wso2/t (‐11≈‐4°C, ppb). The annual average concentration of SO2, as sampled by the passive sampler, was 79ppb, 33ppb, and 24ppb in heavily polluted, intermediate and reference areas, respectively. The multi‐regressional analysis applied to data collected during the mornings (6: 00 am ‐8: 00 pm), afternoons (11: 00 am ‐ 1: 00 pm) and night (10: 00 pm ‐ 12: 00 pm) shows that SO2 concentrations in the morning and night were the most significant variables associated with daily concentration averages.

Continuing Lichen Recolonization in the Upper Ohio River Valley

Improvement in the air quality of the upper Ohio River valley has led to lichen recolonization at previously depauperate sites. Between 1973 and 1996 the number of corticolous macrolichen species in the area increased from 6 to 20. During the same time the mean species richness per site increased from 0.8 to 6.5. An indicator species, Flavoparmelia caperata, was absent from all study sites in 1973, but present at 27 of 28 study sites in 1996. Lichen studies performed over time provide a good tool to document air quality improvement, but a single study in a changing air quality environment may give problematic results. There are many published accounts of the detrimental effects of air pollution, especially sulfur dioxide, on lichen species distribution and community success (Ferry et al. 1973; Nash & Wirth 1988). Recently, however, industrial modernization and clean air legislation have led to decreases in sulfur emissions with concomitant decreases in ground-level SO2 concentrations both in North America and Europe. One source (Placet & Streets 1987) estimated that total SO2 emissions in the United States decreased from 26.8 million metric tons in 1975 to 21.2 million metric tons in 1985. There have been further decreases to 16.6 million metric tons in 1995 (USEPA 1996). Ohio has shown similar decreases in emissions with 2.99 million metric tons in 1975, 2.43 in 1985 and 1.90 in 1995. The upper Ohio River valley was once reputed to have the dirtiest air in the nation (Showman 1990). This area was heavily industrialized with coal-burning power plants, steel mills, foundries, and coking ovens. However, the region was severely affected by the economic recession in the late 1970s that led to the decline of the steel industry. Old plants were closed and others were upgraded and modernized. At the same time, clean air legislation led to particulate and gaseous emission controls on most electric power generation and industrial plants. This decrease in emissions had a dramatic effect on the ambient SO2 levels measured at upper Ohio River valley locations. Monitoring data (North Ohio Valley Air Authority, pers. comm.) show that in 1975, Steubenville, Ohio had an annual average SO2 concentration of 118 iggm-3. In 1985, this had almost halved to 60 agm-3, and by 1995 the value was further reduced to 34 agm-3. Likewise, East Liverpool, Ohio reported annual average SO2 concentrations of 120, 44, and 31 agm-3 during the same years. For comparison, the National ambient air quality standard (annual average) for SO2 is 80 Igm-3. Data from the several monitoring sites in the area consistently show a sharp decline from high to much lower values about 1981 (North Ohio Valley Air Authority, pers. comm.). Lichen studies in the upper Ohio River valley were first conducted in 1973 around Cardinal Power Plant, located just south of Steubenville, Ohio (Fig. 1). After the initial study, it was apparent that the regional SO2 background overwhelmed any contribution to ground-level concentrations by the power plant. Lichens were depauperate throughout a 570 km2 study area with no discernible differences between sites upwind and downwind from the Cardinal Plant. Studies were continued in order to monitor the impact of regional SO2 on lichens. Lichen re-surveys were performed in 1983, 1988, and then yearly to the present. Lichen improvement was first seen in 1988 and a note reporting this was published in 1990 (Showman 1990). The purpose of this paper is to describe lichen recolonization up to 1996 in greater detail, and to relate the observed changes in the lichen flora to potential associations with improved air quality over the same timespan.

A Sensitivity Analysis of the Treatment of Area Sources by the Climatological Dispersion Model

The area-source contributions calculated by the Climatological Dispersion Model (CDM) are sensitive to the size of the grid square used to specify the area source emissions. The authors recommend estimation of highest long term concentrations be accomplished by specifying the emissions with as small a grid size as convenient in that portion of the region having the largest area-source emissions. These conclusions are based on a sensitivity study employing the SO2 emissions inventory developed as part of the St. Louis Regional Air Pollution Study. This inventory specifies the SO2 emissions over a 200-km (east-west) by 140-km (north-south) region. The CDM was used to estimate annual average SO2 concentrations from area-source emissions for 13 locations in the St. Louis metropolitan area for 1976. Although the area source emissions constituted only 3.5 % of total area and point source emissions, estimated concentrations from area sources ranged from 14 to 67% of the total concentration estimated at the 13 si...