Changing trends in sulfur emissions in Asia: implications for acid deposition, air pollution, and climate

A first principles study of RbSnCl3 perovskite toward NH3, SO2, and NO gas sensing

The sensitivity of a RbSnCl3 perovskite 2D layer toward NH3, SO2, and NO toxic gases has been studied via DFT analysis. The tri-atomic layer of RbSnCl3 possessed a tetragonal symmetry with a band gap of 1.433 eV. The adsorption energies of RbSnCl3 for NH3, SO2 and NO are -0.09, -0.43, and -0.56 eV respectively with a recovery time ranging from 3.4 × 10-8 to 3.5 ms. RbSnCl3 is highly sensitive toward SO2 and NO compared to NH3. The adsorption of SO2 and NO results in a significant structural deformation and a semiconductor-to-metal transition of RbSnCl3 perovskite. A high absorption coefficient (>103 cm-1), excessive optical conductivity (>1014 s-1), and a very low reflectivity (<3%) make RbSnCl3 a potential candidate for numerous optoelectronic applications. A significant shift in optical responses is observed through SO2 and NO adsorption, which can enable identification of the adsorbed gases. The studied characteristics signify that RbSnCl3 can be a potential candidate for SO2 and NO detection.

Neighborhood Emission Mapping Operation (NEMO): A 1-km anthropogenic emission dataset in the United States

We present an unprecedented effort to map anthropogenic emissions of air pollutants at 1 km spatial resolution in the contiguous United States (CONUS). This new dataset, Neighborhood Emission Mapping Operation (NEMO), is produced at hourly intervals based on the United States Environmental Protection Agency (US EPA) National Emission Inventories 2017. Fine-scale spatial allocation was achieved through distributing the emission sources using 108 spatial surrogates, factors representing the portion of a source in each 1 km grid. Gaseous and particulate pollutants are speciated into model species for the Carbon Bond 6 chemical mechanism. All sources are grouped in 9 sectors and stored in NetCDF format for air quality models, and in shapefile format for GIS users and air quality managers. This dataset shows good consistency with the USEPA benchmark dataset, with a monthly difference in emissions less than 0.03% for any sector. NEMO provides the first 1 km mapping of air pollution over the CONUS, enabling new applications such as fine-scale air quality modeling, air pollution exposure assessment, and environmental justice studies.

Measurement(s)	anthropogenic emission in United States
Technology Type(s)	Census survey and computer models

Spatiotemporal Evolution and Prediction of AOT in Coal Resource Cities: A Case Study of Shanxi Province, China

As aerosols in the air have a great influence on the health of residents of coal resource-based cities, these municipalities are confronting the dilemma of air pollution that is caused by the increase of suspended particles in the atmosphere and their development process. Aerosol optical thickness could be used to explore the aerosol temporal and spatial variations and to develop accurate prediction models, which is of great significance to the control of air pollution in coal resource-based cities. This paper explored the temporal spatial variation characteristics of aerosols in coal resource-based regions. A total of 11 typical coal-resource prefecture-level cities in the Shanxi Province were studied and inverted the aerosol optical thickness (AOT) among these cities based on MODIS (Moderate Resolution Imaging Spectroradiometer) data and analyzed the significant factors affecting AOT. Through inputting significant correlation factors as the input variables of NARX (nonlinear auto regressive models with exogenous inputs) neural network, the monthly average AOTs in the Shanxi Province were predicted between 2011 and 2019. The results showed that, in terms of time series, AOT increased from January to July and decreased from July to December, the maximum AOT was 0.66 in summer and the minimum was 0.2 in autumn, and it was related to the local monsoon, temperature, and humidity. While as far as the space alignment is concerned, the figure for AOT in Shanxi Province varied significantly. High AOT was mainly concentrated in the centre and south and low AOT was focused on the northwestern part. Among the positively correlated factors, the correlation coefficient of population density and temperature exceeded 0.8, which was highly positive, and among the negatively correlated factors, the correlation coefficient of NDVI exceeded -0.8, which was highly negative. After improving the model by adding the important factors that were mentioned before, the error between the predicted mean value and the actual mean value was no more than 0.06. Considering this charge, the NARX neural network with multiple inputs can contribute to better prediction results.

Sulfur deposition changed the community structure of soil nematodes by affecting omnivores-predators

Nematodes generally occupy multiple trophic levels in detrital food webs, which play a vital role in energy flow, material conversion and nematodes community structure stability in the underground ecosystem. Sulfur (S) is one of the important soil nutrients, and it plays an important role in the nutrient cycle of grassland ecosystem. However, the impacts of S on soil fauna and subsurface detrital food webs in grassland ecosystems were rarely studied. Accordingly, to investigate the effects of sulfur deposition on soil nematodes and detrital food webs, we conducted a S addition experiment with distinct intensities from 0 to 50 g S m^-2 yr^-1 (S 0, S 1, S 2, S 5, S 10, S 15, S 20, and S 50) to simulated sulfur deposition in a meadow steppe of northern China. We documented a significant effect of S addition on the diversity and richness of nematodes, and the species richness of soil nematodes was high in the study site. But S addition had no significant effect on the total abundance and dominant species of nematodes (Cervidellus and Aphelenchus). Results of correlation analysis and structural equation modeling consistently indicated that omnivores-predators were significantly affected by sulfur addition. A significant increase in the Structural Index (which indicates food web structure) suggested increased top-down forces and changed community structure, although bacterivores, fungivores, plant parasites did not significantly. The present results suggest that sulfur deposition would change the composition of nematode community, affect the stability of nematode community structure, and increase the disturbance to the underground ecosystem. The study provides that the detailed information of the response of nematode to S deposition can be used to analyze the process of global change affecting the underground ecosystem.

Detection of sulfur dioxide at low parts-per-million concentrations using low-cost planar electrodes with ionic liquid electrolytes

Sulfur dioxide (SO₂) is a toxic gas at low parts-per-million (ppm) concentrations, with a permissible exposure limit (PEL) of 2 ppm. Its detection is mandatory, particularly in the fields of occupational health and safety, and environmental pollution. In this work, ppm concentration detection of sulfur dioxide was performed in six room temperature ionic liquids (RTILs), as well as on two different electrode materials - platinum and gold - and with two different electrode geometries, i.e. macro thin-film electrodes (TFEs) and microarray thin-film electrodes (MATFEs). Calibration curves were established for 10-200 ppm SO₂ using cyclic voltammetry to determine the optimum combination of RTIL, electrode surface and geometry for the sensing. The RTIL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonium)imide ([C₄mpyrr][NTf₂]) with a platinum thin-film electrode was found to give the best response due to the relatively low viscosity of the RTIL combined with the high sensitivity and a clean blank response. On MATFEs, deposited sulfur particles - confirmed using scanning electron microscopy (SEM) coupled to an energy dispersive spectrometer - were found to passivate and block some of the microholes, leading to unstable long-term chronoamperometric responses. To the best of our knowledge, this is the first observation of sulfur deposition from SO₂ reduction in aprotic ionic liquids. Consecutive additions of 2 ppm SO₂ were studied in [C₄mpyrr][NTf₂] on a TFE using long-term chronoamperometry, showing excellent reproducibility upon successive additions. This demonstrates that small volumes of RTILs can be combined with miniaturized, low-cost TFEs and applied for the reliable and continuous monitoring of sulfur dioxide gas at concentrations lower than the permissible exposure limit of 2 ppm.

Decoupling and decomposition analysis of industrial sulfur dioxide emissions from the industrial economy in 30 Chinese provinces

As one of the largest emitters of sulfur dioxide (SO₂), China has faced increasing pressure to achieve sustainable development. This study investigates the decoupling relationship between industrial SO₂ emissions and the industrial economy in China during 1996-2015. According to the decoupling results, the study period is divided into four stages: 1996-2001, 2001-2006, 2006-2010, and 2010-2015. These four stages are closely aligned with the major adjustments of the national socio-economic policies. Then, the logarithmic mean Divisia index (LMDI) decomposition method is used to analyze the driving factors of industrial SO₂ emissions. The results demonstrate that the SO₂ generation intensity and SO₂ abatement are the major contributors to reducing industrial SO₂ emissions, while the economic activity effect is the primary inhibitory factor. Moreover, the provincial results show that most provinces with weak decoupling state since 2006 are located in less developed provinces with energy-intensive industries. Besides, the economic structure and SO₂ generation intensity show negative contributions to reducing industrial SO₂ emissions in some of these regions. Based on the results, the attention should be focused on cleaner production to reduce industrial SO₂ emissions further, and environmental policies should be tailored to local conditions.

Air pollution reduction in China: Recent success but great challenge for the future

China's rapid economic growth has caused severe air pollution, raising serious concerns about the growing evidence of its negative health, environmental, and economic impacts. Consequently, the Chinese government has implemented a number of policies and measures to reduce air pollution. Relying on published information over the last three decades in China, we analyzed trends in air pollutant emissions (SO₂ and NO_x) and concentrations of particulate matter (PM) and ozone (O₃). During the past decade, SO₂ and NO_x emissions had declined throughout China and concentrations of PM_2.5 and PM₁₀ had considerably decreased in most cities, but average reported 90th MDA8 O₃, M7, and AOT40 O₃ for 31 capital cities showed an increasing trend between 2013 and 2017. Despite progress in air pollution reduction and an increasing number of "clear sky" days, PM concentrations throughout China remain higher than the World Health Organization guidelines, and urban smog and haze remain a major threat to human health and the environment. Thus far, significant emission reductions have occurred largely through robust administrative power, especially when emission reductions were tied to the performance evaluations and promotion of government officials. Similar to most already-industrialized nations, China is now shifting away from SO₂-dominated to NO_x- and O₃-dominated air pollution. Existing technologies and improved operations of existing control equipment appear unlikely to achieve sufficient reductions in NO_x and O₃ pollution. Considering the complex relationship between O₃, NO_x, VOCs, weather, and socio-economic changes in China, it is necessary to increase research on impacts of increasing ozone on plants and to adopt novel technologies and implemented to further reduce air pollution to levels that will protect human health and the environment.

Reducing U.S. residential energy use and CO2 emissions: how much, how soon, and at what cost?

There is growing interest in reducing energy use and emissions of carbon dioxide from the residential sector by deploying cost-effectiveness energy efficiency measures. However, there is still large uncertainty about the magnitude of the reductions that could be achieved by pursuing different energy efficiency measures across the nation. Using detailed estimates of the current inventory and performance of major appliances in U.S. homes, we model the cost, energy, and CO2 emissions reduction if they were replaced with alternatives that consume less energy or emit less CO2. We explore trade-offs between reducing CO2, reducing primary or final energy, or electricity consumption. We explore switching between electricity and direct fuel use, and among fuels. The trade-offs between different energy efficiency policy goals, as well as the environmental metrics used, are important but have been largely unexplored by previous energy modelers and policy-makers. We find that overnight replacement of the full stock of major residential appliances sets an upper bound of just over 710 × 10(6) tonnes/year of CO2 or a 56% reduction from baseline residential emissions. However, a policy designed instead to minimize primary energy consumption instead of CO2 emissions will achieve a 48% reduction in annual carbon dioxide emissions from the nine largest energy consuming residential end-uses. Thus, we explore the uncertainty regarding the main assumptions and different policy goals in a detailed sensitivity analysis.

Characteristics and recent trends of sulfur dioxide at urban, rural, and background sites in north China: effectiveness of control measures

SO2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO2 at different types of sites in Northern China. The overall average concentrations of SO2 are (16.8 +/- 13.1) ppb, (14.8 +/- 9.4) ppb, and (7.5 +/- 4.0) ppb at China Meteorological Administration (CMA, Beijing urban area), Gucheng (GCH, relatively polluted rural area, 110 km to the southwest of Beijing urban area), and Shangdianzi (SDZ, clean background area, 100 km to the northeast of Beijing urban area), respectively. The SO2 levels in winter (heating season) are 4-6 folds higher than those in summer. There are highly significant correlations among the daily means of SO2 at different sites, indicating regional characteristics of SO2 pollution. Diurnal patterns of surface SO2 at all sites have a common feature with a daytime peak, which is probably caused by the downward mixing and/or the advection transport of SO2-richer air over the North China Plain. The concentrations of SO2 at CMA and GCH show highly significant downward trends (-4.4 ppb/yr for CMA and -2.4 ppb/yr for GCH), while a less significant trend (-0.3 ppb/yr) is identified in the data from SDZ, reflecting the character of SDZ as a regional atmospheric background site in North China. The SO2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games, suggesting that the SO2 pollution control has long-term effectiveness and benefits. In the post-Olympics period, the mean concentrations of SO2 at CMA, GCH, and SDZ are (14.3 +/- 11.0) ppb, (12.1 +/- 7.7) ppb, and (7.5 +/- 4.0) ppb, respectively, with reductions of 26%, 36%, and 13%, respectively, compared to the levels before. Detailed analysis shows that the differences of temperature, relative humidity, wind speed, and wind direction were not the dominant factors for the significant differences of SO2 between the pre-Olympics and post-Olympics periods. By extracting the data being more representative of local or regional characteristics, a reduction of up to 40% for SO2 in polluted areas and a reduction of 20% for regional SO2 are obtained for the effect of control measures implemented for the Olympic Games.

Multiple effects and uncertainties of emission control policies in China: Implications for public health, soil acidification, and global temperature

Policies to control emissions of criteria pollutants in China may have conflicting impacts on public health, soil acidification, and climate. Two scenarios for 2020, a base case without anticipated control measures and a more realistic case including such controls, are evaluated to quantify the effects of the policies on emissions and resulting environmental outcomes. Large benefits to public health can be expected from the controls, attributed mainly to reduced emissions of primary PM and gaseous PM precursors, and thus lower ambient concentrations of PM2.5. Approximately 4% of all-cause mortality in the country can be avoided (95% confidence interval: 1-7%), particularly in eastern and north-central China, regions with large population densities and high levels of PM2.5. Surface ozone levels, however, are estimated to increase in parts of those regions, despite NOX reductions. This implies VOC-limited conditions. Even with significant reduction of SO2 and NOX emissions, the controls will not significantly mitigate risks of soil acidification, judged by the exceedance levels of critical load (CL). This is due to the decrease in primary PM emissions, with the consequent reduction in deposition of alkaline base cations. Compared to 2005, even larger CL exceedances are found for both scenarios in 2020, implying that PM control may negate any recovery from soil acidification due to SO2 reductions. Noting large uncertainties, current polices to control emissions of criteria pollutants in China will not reduce climate warming, since controlling SO2 emissions also reduces reflective secondary aerosols. Black carbon emission is an important source of uncertainty concerning the effects of Chinese control policies on global temperature change. Given these conflicts, greater consideration should be paid to reconciling varied environmental objectives, and emission control strategies should target not only criteria pollutants but also species such as VOCs and CO2.

Effects of reduced nitrogen and sulphur deposition on the water chemistry of moorland pools

To assess changes as a result of reduced acidifying deposition, water chemistry data from 68 Dutch moorland pools were collected during the periods 1983-1984 and 2000-2006. Partial recovery was observed: nitrate- and ammonium-N, sulphur and aluminium concentrations decreased, while pH and alkalinity increased. Calcium and magnesium concentrations decreased. These trends were supported by long term monitoring data (1978-2006) of four pools. Increased pH correlated with increases in orthophosphate and turbidity, the latter due to stronger coloration by organic acids. Increased ortho-phosphate and turbidity are probably the result of stronger decomposition of organic sediments due to decreased acidification and may hamper full recovery of moorland pool communities. In addition to meeting emission targets for NO(x), NH(x) and SO(x), restoration measures are still required to facilitate and accelerate recovery of acidified moorland pools.

Historical reconstruction of mercury pollution across the Tibetan Plateau using lake sediments

The Tibetan Plateau is described as the "Roof of the World" averaging over 4000 m above sea level; it is remote, isolated, and presumed to be a pristine region. In order to study the history of atmospheric mercury (Hg) pollution and its spatial variation across the Plateau, lakes were chosen from three areas forming a north to south transect. Sediment cores were taken from three sites in each area and dated using the radionuclides 210Pb and 137Cs. Analysis of the cores yielded the first comprehensive Hg reconstructions for the Plateau, showing clear Hg pollution at all sites. The first indication of Hg pollution is much earlier than the onset of the industrial revolution in Europe, but the most significant pollution increase is from the 1970s, followed by a further marked increase from the 1990s. The mean post-2000 atmospheric pollution Hg accumulation rates for the sampling sites were estimated at between 5.1 and 7.9 microg m(-2) yr(-1). The increase in Hg pollution over the last few decades is synchronous with the recent economic development in Asia (especially China and India), and pollution Hg levels continue to increase. Furthermore, contemporary sediment Hg accumulation rate data are in broad agreement with Hg deposition values derived from global models that attribute pollution to sources mainly within southeast Asia. As most of the sites are exceptionally remote and situated above the atmospheric boundary layer, these results underline the need to understand the local Hg cycle in both regional and global context.

Understanding the chemical properties of macerals and minerals in coal and its potential application for occupational lung disease prevention

Recent increases in oil price further strengthen the argument that coal and coal products will play an increasingly important role in fulfilling the energy needs of our society. Coal is an aggregate of heterogeneous substances composed of organic (macerals) and inorganic (minerals) materials. The objective of this review was to assess whether some chemical parameters in coal play a role in producing environmental health problems. Basic properties of coal--such as chemical forms of the organic materials, structure, compositions of minerals--vary from one coal mine region to another as well as from coals of different ranks. Most importantly, changes in chemical properties of coals due to exposure to air and humidity after mining--a dynamic process--significantly affect toxicity attributed to coal and environmental fate. Although coal is an extremely complex and heterogeneous material, the fundamental properties of coal responsible for environmental and adverse health problems are probably related to the same inducing components of coal. For instance, oxidation of pyrite (FeS2) in the coal forms iron sulfate and sulfuric acid, which produces occupational lung diseases (e.g., pneumoconiosis) and other environmental problems (e.g., acid mine drainage and acid rain). Calcite (CaCO3) contained in certain coals alters the end products of pyrite oxidation, which may make these coals less toxic to human inhalation and less hazardous to environmental pollution. Finally, knowledge gained on understanding of the chemical properties of coals is illustrated to apply for prediction of toxicity due to coal possibly before large-scale mining and prevention of occupational lung disease during mining.

Intercontinental transport of aerosols and photochemical oxidants from Asia and its consequences

The intercontinental transport of aerosols and photochemical oxidants from Asia is a crucial issue for air quality concerns in countries downwind of the significant emissions and concentrations of pollutants occurring in this important region of the world. Since the lifetimes of some important pollutants are long enough to be transported over long distance in the troposphere, regional control strategies for air pollution in downwind countries might be ineffective without considering the effects of long-range transport of pollutants from Asia. Field campaigns provide strong evidence for the intercontinental transport of Asian pollutants. They, together with ground-based observations and model simulations, show that the air quality over parts of North America is being affected by the pollutants transported from Asia. This paper examines the current understanding of the intercontinental transport of gases and aerosols from Asia and resulting effects on air quality, and on the regional and global climate system.

Mapping and prediction of coal workers' pneumoconiosis with bioavailable iron content in the bituminous coals

Based on the first National Study of Coal Workers' Pneumoconiosis (CWP) and the U.S. Geological Survey database of coal quality, we show that the prevalence of CWP in seven coal mine regions correlates with levels of bioavailable iron (BAI) in the coals from that particular region (correlation coefficient r = 0.94, p < 0.0015). CWP prevalence is also correlated with contents of pyritic sulfur (r = 0.91, p < 0.0048) or total iron (r = 0.85, p < 0.016) but not with coal rank (r = 0.59, p < 0.16) or silica (r = 0.28, p < 0.54). BAI was calculated using our model, taking into account chemical interactions of pyrite, sulfuric acid, calcite, and total iron. That is, iron present in coals can become bioavailable by pyrite oxidation, which produces ferrous sulfate and sulfuric acid. Calcite is the major component in coals that neutralizes the available acid and inhibits iron's bioavailability. Therefore, levels of BAI in the coals are determined by the available amounts of acid after neutralization of calcite and the amount of total iron in the coals. Using the linear fit of CWP prevalence and the calculated BAI in the seven coal mine regions, we have derived and mapped the pneumoconiotic potencies of 7,000 coal samples. Our studies indicate that levels of BAI in the coals may be used to predict coal's toxicity, even before large-scale mining.

Seasonal variation of chemical composition in fine particles at Gosan, Korea

PM2.5 aerosol samples were collected at Gosan in Jeju Island during six intensive measurement periods between November 2001 and August 2003. In order to investigate the chemical composition of fine particles, major ion components, trace elements, and elemental and organic carbon were analyzed. Quite different seasonal characteristic in the chemical composition of fine particles was observed. The concentration of most secondary aerosol components showed a summer minimum and a winter maximum with higher correlation between them at Gosan. This fact clearly reveals the possibility of long-range transport of such pollutants in winter. On the other hand, OC and EC had the highest concentration and good correlation with ion components, such as K+, Ca2+ in fall. It means that biomass burning could significantly influence the ambient fine carbonaceous particulate in fall, which was primarily long-range transported.

Global sulfur emissions from 1850 to 2000

The ASL database provides continuous time-series of sulfur emissions for most countries in the World from 1850 to 1990, but academic and official estimates for the 1990s either do not cover all years or countries. This paper develops continuous time series of sulfur emissions by country for the period 1850-2000 with a particular focus on developments in the 1990s. Global estimates for 1996-2000 are the first that are based on actual observed data. Raw estimates are obtained in two ways. For countries and years with existing published data I compile and integrate that data. Previously published data covers the majority of emissions and almost all countries have published emissions for at least 1995. For the remaining countries and for missing years for countries with some published data, I interpolate or extrapolate estimates using either an econometric emissions frontier model, an environmental Kuznets curve model, or a simple extrapolation, depending on the availability of data. Finally, I discuss the main movements in global and regional emissions in the 1990s and earlier decades and compare the results to other studies. Global emissions peaked in 1989 and declined rapidly thereafter. The locus of emissions shifted towards East and South Asia, but even this region peaked in 1996. My estimates for the 1990s show a much more rapid decline than other global studies, reflecting the view that technological progress in reducing sulfur based pollution has been rapid and is beginning to diffuse worldwide.

Speciation of iron and sulfate in acid waters: aqueous clusters to mineral precipitates

Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, FeIII, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy. The molalities of sulfate (15 mmol/ kg) and iron (10, 20, and 50 mmol/kg), and pH (1, 2, and 3) were chosen to mimic the concentration of ions in AMD waters. Sulfate and FeII either associate in outer-sphere complexes or do not associate at all. In contrast, sulfate interacts strongly with FeIII. The predominating species in FeIII-SO4 solutions are hydrogen-bonded complexes; inner-sphere complexes account only for 10+/-10% of the total sulfate. Our results show that the mode of interaction between FeIII and sulfate is similar in aqueous phase and in nanocrystalline precipitate schwertmannite (approximately FeO(OH)3/4(SO4)1/8). Because of this similarity, schwert-mannite should be the phase that controls solubility and availability of FeIII, SO4, and indirectly also other components in the AMD solutions.

Cost-effective control of SO2 emissions in Asia

Despite recent efforts to limit the growth of SO(2) emissions in Asia, the negative environmental effects of sulphur emissions are likely to further increase in the future. This paper presents an extension of the RAINS-Asia integrated assessment model for acidification in Asia with an optimisation routine that can be used to identify cost-effective emission control strategies that achieve environmental targets for ambient SO(2) concentrations and sulphur deposition at least costs. Example scenarios developed with this optimisation module demonstrate a potential for significant cost savings in Asia, if emission controls are allocated to those sources that have the largest environmental impact and are cheapest to control. It is shown that strategies that simultaneously address harmful population exposure and the risk of vegetation damage from acid deposition result in the most cost-effective use of resources spent for emission controls.

Laboratory and field measurements of dry deposition of sulfur dioxide onto Chinese loess surfaces

Laboratory and field measurements were conducted to examine dry deposition of SO2 onto Chinese loess surfaces using native soil sampled in the loess plateau, China. The field tests were employed in Beijing and Lanzhou, China, by directly measuring the dry deposition of SO2 on soil, which uses soil put on a collector as an SO2 passive sampling medium. In the laboratory, a high rate of uptake to SO2 deposition for Chinese soil surfaces due to the highly alkalinity was found. The uptake of SO2 deposition was dependent on the pH soil and relative humidity. Furthermore, we evaluated some factors that affect the measurement precision: response of SO2 uptake, repeatability, recovery factor, and variability associated with the weight and the surface coverage on the collectors. As a result, it was shown that the measurement precision was primarily related to the ratio of the SO2 deposition amount relative to the sulfur content of the original soil. This result was consistent with the field observations. The laboratory and field results indicated an excellent agreement on the SO2 uptake inherent in the results from the soil surfaces in different regions.

Intercontinental transport of air pollution: will emerging science lead to a new hemispheric treaty?

We examine the emergence of InterContinental Transport (ICT) of air pollution on the agendas of the air quality and climate communities and consider the potential for a new treaty on hemispheric air pollution. ICT is the flow of air pollutants from a source continent (e.g., North America) to a receptor continent (e.g., Europe). ICT of air pollutants occurs through two mechanisms: (i) episodic advection and (ii) increasing the global background, which enhances surface concentrations. We outline the current scientific evidence for ICT of aerosols and ozone, both of which contribute to air pollution and radiative forcing. The growing body of scientific evidence for ICT suggests that a hemispheric-scale treaty to reduce air pollutant concentrations may be appropriate to address climate and air quality concerns simultaneously. Such a treaty could pave the way for future climate agreements.