OMI-based emission source classification in East China and its spatial redistribution in view of pollution control measures

This study aims to generate a satellite-based qualitative emission source characterization for the heavily polluted eastern part of China in the 2010-2016 time period. The applied source identification technique relies on satellite-based NOx and SO2 emission estimates by OMI, their SO2:NOx ratio, and the MIX anthropogenic emission inventory to distinguish emissions from different emission categories (urban, industrial, natural) and characterize the dominant source per 0.25° × 0.25° grid cell in East China. Overall, we find good agreement between the satellite- and emission inventory-based spatiotemporal distribution and characterization of the dominant emission sources in East China in 2010-2016. In 2010, the satellite measurements suggest an emission distribution less dominated by industrial areas, a somewhat larger role for urban/transportation areas and agricultural activities, and more natural emissions in the southern part compared to the bottom-up emission categorization. In 2016, more than half of the classified emission categories over East China have remained the same. At the same time, there is a notable increase of agricultural lands and decrease of areas dominated by industry/transportation in 2016, suggestive of an overall decrease in heavy air pollution in East China over the course of 7 years. This is likely attributed to the sustained efforts of the Chinese government to drastically improve the air quality, especially since 2013 when the National Air Pollution Prevention and Control Action Plan was enacted. However, signs of urban expansion (urbanization) and rural-urban migration ("Go West" motion) stemmed from China's rapid economic growth and labour demand are evident; escalating industrialization (even with cleaner means) and the urban population growth in East China resulted in stronger emissions from sources representing consumption and transportation which are strongly related to NO2 and PM10 pollution (rather than SO2) and are directly influenced by the population size. This resulted to a shift of the emissions from the east mainly to the north and northwest of East China. Overall, although the effectiveness of the Chinese environmental control policies has been successful, the air pollution problem remains an important concern.

Sulphur dioxide and fluoride co-exposure cause enamel damage by disrupting the Cl-/HCO3- ion transport

OBJECTIVE

Although there is growing evidence linking the exposure to sulphur dioxide (SO₂) and fluoride to human diseases, there is little data on the co-exposure of SO₂ and fluoride. Moreover, literature on SO₂ and fluoride co-exposure to enamel damage is insufficient. In this work, we concentrate on the concurrent environmental issues of excessive SO₂ and fluoride in several coal-consuming regions.

METHOD

To identify the toxicity of SO₂ and fluoride exposure either separately or together, we used both ICR mice and LS8 cells, and factorial design was employed to assess the type of potential combined action.

RESULT

In this study, co-exposure to SO₂ and fluoride exacerbated enamel damage, resulting in more severe enamel defects of incisor and the damage occurred earlier. Cl^-/HCO₃^- exchanger expression is increased by SO₂ and fluoride in mouse incisor. Consistent with in vivo results, co-exposure of SO₂ and fluoride decreased pHi and increased [Cl^-]i level by increasing the expression of the Cl^-/HCO₃^- exchanger in LS8 cells. Furthermore, SO₂ and F may increase merlin protein expression, and merlin deficiency causes AE2 expression to decrease in vitro.

CONCLUSION

Overall, these results indicate that co-exposure to SO₂ and fluoride may result in more toxicity both in vitro and in vivo than a single exposure to SO₂ and fluoride, suggesting that residents in areas contaminated with SO₂ and fluoride may be more likely to suffer enamel damage.

Improvements in SO2 pollution in India: role of technology and environmental regulations

India relies heavily on coal-based thermal power plants to meet its energy demands. Sulphur dioxide (SO₂) emitted from these plants and industries is a major air pollutant. Analysis of spatial and temporal changes in SO₂ using accurate and continuous observations is required to formulate mitigation strategies to curb the increasing air pollution in India. Here, we present the temporal changes in SO₂ concentrations over India in the past four decades (1980-2020). Our analysis shows that the Central and East India, and Indo-Gangetic Plain (IGP) are the hotspots of SO₂, as these regions house a cluster of thermal power plants, petroleum refineries, steel manufacturing units, and cement Industries. Thermal power plants (51%), and manufacturing and construction industries (29%) are the main sources of anthropogenic SO₂ in India. Its concentration over India is higher in winter (December-February) and lower in pre-monsoon (March-May) seasons. The temporal analyses reveal that SO₂ concentrations in India increased between 1980 and 2010 due to high coal burning and lack of novel technology to contain the emissions during the period. However, SO₂ shows a decreasing trend in recent decade (2010-2020) because of the environmental regulations and implementation of effective control technologies such as the flue gas desulphurisation (FGD) and scrubber. Since 2010, India's renewable energy production has also been increased substantially when India adopted a sustainable development policy. Therefore, the shift in energy production from conventional coal to renewable sources, solid environmental regulation, better inventory, and effective technology would help to curb SO₂ pollution in India. Both economic growth and air pollution control can be performed hand-in-hand by adopting new technology to reduce SO₂ and GHG emissions.

Sulphur dioxide and fluoride co-exposure induce incisor hypomineralization and amelogenin upregulation via YAP/RUNX2 signaling pathway

Sulphur dioxide (SO₂) and fluoride are among the most common environmental pollutants affecting human health, and both co-exist in areas predominantly consuming coal. It is vital to analyse the combined toxicity of SO₂ and fluoride, and their effects on health and the underlying mechanisms of their co-exposure have not yet been adequately assessed. In the present study, we used ICR mice and LS8 cells to investigate the toxicity of SO₂ and fluoride exposure to the enamel, alone or in combination. Factorial design analysis was used to reveal the combined toxicity in vitro and in vivo. Co-exposure to SO₂ and fluoride exacerbated enamel injury, resulting in more severe hypomineralization of incisor, and enamel structure disorders in mice, and could induce the accumulation of protein residue in the matrix of the enamel. Amelogenin expression was increased upon exposure to SO₂ and fluoride, but enamel matrix proteases were not affected. Consistent with our in vivo results, co-exposure of SO₂ and fluoride aggravated amelogenin expression in LS8 cells, and increased the YAP and RUNX2 levels. Co-exposure to SO₂ and fluoride resulted in greater toxicity than individual exposure, both in vitro and in vivo, indicating that residents of areas exposed to SO₂ and fluoride may have an increased risk of developing enamel damage.

Links between the concentrations of gaseous pollutants measured in different regions of Estonia

The factors that determine the concentrations of air pollutants (NO, NO₂, SO₂, O₃), measured in 8 monitoring stations (4 rural background, 3 urban, and 1 industrial) in Estonia, are studied applying the factor analysis. The factor analysis reveals remarkable impact of COVID-19 lockdown, effects caused by dramatic decrease in oil-shale based energy production in Estonia provoked by new socio-economic conditions such as elevated price for CO₂ emission quota, differences between rural and urban stations, maritime-continental difference for NO₂ and ozone, and specific industrial impact in case of SO₂. The multiple regression analysis to predict the ozone concentration in one rural background station at Tahkuse was performed, based on the ozone concentrations measured in other stations and the concentrations of NO, NO₂, and CO₂, recorded in the same station. It was found that the ozone concentration at Tahkuse is rather well predictable (determination coefficient, i.e., correlation coefficient squared, R ² = 0.714), using only the concentrations from another rural station at Saarejärve that is about 110 km away from Tahkuse. Adding all the available data into the list of regression analysis arguments, the model predictability is improved moderately (determination coefficient R ² = 0.795). Large model residuals above all tend to occur with the values measured and predicted at summer nights. Surprisingly, neither NO nor NO₂ concentration measured in the Tahkuse station did appear a good predictor for ozone (R ² = 0.02 and 0.05, respectively), possibly long-range transport of ozone (that has also experienced NO and/or NO₂ influence during transport) overrides the local effects of NO and/or NO₂.

Foliar stable isotope ratios of carbon and nitrogen in boreal forest plants exposed to long-term pollution from the nickel-copper smelter at Monchegorsk, Russia

Long-term exposure to primary air pollutants, such as sulphur dioxide (SO2) and nitrogen oxides (NOx), alters the structure and functions of forest ecosystems. Many biochemical and biogeochemical processes discriminate against the heavier isotopes in a mixture; thus, the values of δ13C and δ15N (i.e. the ratio of stable isotopes 13C to 12C and that of 15 N to 14 N, respectively) may give insights into changes in ecosystem processes and identify the immediate drivers of these changes. We studied sources of variation in the δ13C and δ15N values in the foliage of eight boreal forest C3 plants at 10 sites located at the distance of 1-40 km from the Monchegorsk nickel-copper smelter in Russia. From 1939‒2019, this smelter emitted over 14,000,000 metric tons (t) of SO2, 250,000 t of metals, primarily nickel and copper, and 140,000 t of NOx. The δ13C value in evergreen plants and the δ15N value in all plants increased near the smelter independently of the plant mycorrhizal type. We attribute the pollution-related increase in the foliar δ13C values of evergreen species mainly to direct effects of SO2 on stomatal conductance, in combination with pollution-related water stress, which jointly override the potential opposite effect of increasing ambient CO2 concentration on δ13C values. Stomatal uptake of NOx and root uptake of 15N-enriched organic N compounds and NH4+ may explain the increased foliar δ15N values and elevated foliar N concentrations, especially in the evergreen trees (Pinus sylvestris), close to Monchegorsk, where the soil inorganic N supply is reduced due to the impact of long-term SO2 and heavy metal emissions on plant biomass. We conclude that, despite the uncertainties in interpreting δ13C and δ15N responses to pollution, the Monchegorsk smelter has imposed and still imposes a great impact on C and N cycling in the surrounding N-limited subarctic forest ecosystems.

Evaluation of oil palm fiber biochar and activated biochar for sulphur dioxide adsorption

The emission of sulphur dioxide (SO₂) gas from power plants and factories to the atmosphere has been an environmental challenge globally. Thus, there is a great interest to control the SO2 gas emission economically and effectively. This study aims to use and convert abundantly available oil palm fiber (OPF) biomass into an adsorbent to adsorb SO₂ gas. The preparation of OPF biochar and activated biochar was optimised using the Response Surface Methodology (RSM) based on selected parameters (i.e., pyrolysis temperature, heating rate, holding time, activation temperature, activation time and CO₂ flowrate). The best adsorbent was found to be the OPF activated biochar (OPFAB) compared to OPF biochar. OPFAB prepared at 753 °C for 73 min of activation time with 497 ml/min of CO₂ flow yields the best adsorption capacity (33.09 mg/g) of SO₂. Meanwhile, OPF pyrolysed at 450 °C of heating temperature, 12 °C/min of heating rate and 98 min of holding time yield adsorption capacity at 18.62 mg/g. Various characterisations were performed to investigate the properties and mechanism of the SO₂ adsorption process. Thermal regeneration shows the possibilities for the spent adsorbent to be recycled. The findings imply OPFAB as a promising adsorbent for SO₂ adsorption.

A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission conditions

This global study, which has been coordinated by the World Meteorological Organization Global Atmospheric Watch (WMO/GAW) programme, aims to understand the behaviour of key air pollutant species during the COVID-19 pandemic period of exceptionally low emissions across the globe. We investigated the effects of the differences in both emissions and regional and local meteorology in 2020 compared with the period 2015-2019. By adopting a globally consistent approach, this comprehensive observational analysis focuses on changes in air quality in and around cities across the globe for the following air pollutants PM_2.5, PM₁₀, PMC (coarse fraction of PM), NO₂, SO₂, NOx, CO, O₃ and the total gaseous oxidant (OX = NO₂ + O₃) during the pre-lockdown, partial lockdown, full lockdown and two relaxation periods spanning from January to September 2020. The analysis is based on in situ ground-based air quality observations at over 540 traffic, background and rural stations, from 63 cities and covering 25 countries over seven geographical regions of the world. Anomalies in the air pollutant concentrations (increases or decreases during 2020 periods compared to equivalent 2015-2019 periods) were calculated and the possible effects of meteorological conditions were analysed by computing anomalies from ERA5 reanalyses and local observations for these periods. We observed a positive correlation between the reductions in NO₂ and NOx concentrations and peoples' mobility for most cities. A correlation between PMC and mobility changes was also seen for some Asian and South American cities. A clear signal was not observed for other pollutants, suggesting that sources besides vehicular emissions also substantially contributed to the change in air quality. As a global and regional overview of the changes in ambient concentrations of key air quality species, we observed decreases of up to about 70% in mean NO₂ and between 30% and 40% in mean PM_2.5 concentrations over 2020 full lockdown compared to the same period in 2015-2019. However, PM_2.5 exhibited complex signals, even within the same region, with increases in some Spanish cities, attributed mainly to the long-range transport of African dust and/or biomass burning (corroborated with the analysis of NO₂/CO ratio). Some Chinese cities showed similar increases in PM_2.5 during the lockdown periods, but in this case, it was likely due to secondary PM formation. Changes in O₃ concentrations were highly heterogeneous, with no overall change or small increases (as in the case of Europe), and positive anomalies of 25% and 30% in East Asia and South America, respectively, with Colombia showing the largest positive anomaly of ~70%. The SO₂ anomalies were negative for 2020 compared to 2015-2019 (between ~25 to 60%) for all regions. For CO, negative anomalies were observed for all regions with the largest decrease for South America of up to ~40%. The NO₂/CO ratio indicated that specific sites (such as those in Spanish cities) were affected by biomass burning plumes, which outweighed the NO₂ decrease due to the general reduction in mobility (ratio of ~60%). Analysis of the total oxidant (OX = NO₂ + O₃) showed that primary NO₂ emissions at urban locations were greater than the O₃ production, whereas at background sites, OX was mostly driven by the regional contributions rather than local NO₂ and O₃ concentrations. The present study clearly highlights the importance of meteorology and episodic contributions (e.g., from dust, domestic, agricultural biomass burning and crop fertilizing) when analysing air quality in and around cities even during large emissions reductions. There is still the need to better understand how the chemical responses of secondary pollutants to emission change under complex meteorological conditions, along with climate change and socio-economic drivers may affect future air quality. The implications for regional and global policies are also significant, as our study clearly indicates that PM_2.5 concentrations would not likely meet the World Health Organization guidelines in many parts of the world, despite the drastic reductions in mobility. Consequently, revisions of air quality regulation (e.g., the Gothenburg Protocol) with more ambitious targets that are specific to the different regions of the world may well be required.

Arsenic and SO2 hotspot in South-Eastern Europe: An overview of the air quality after the implementation of the flash smelting technology for copper production

This extensive study considered the air pollution data after the flash smelting technology for copper production had become fully operational. The assessment of the air quality after the implementation was significantly important, since the modernisation was necessary for reducing the environmental contamination in one of the most polluted regions in South-Eastern Europe. The concentrations of SO₂, PM₁₀ and toxic elements (As, Pb, Cd, Ni) in PM₁₀ samples were monitored at different sites, with respect to the copper smelter, in the period 2016-2019. The air quality evaluation was performed concerning the corresponding limit and target values defined by the Serbian and European legislation, as well as the World Health Organization Air Quality Guidelines (WHO AQG). The measured SO₂ concentrations indicated frequent exceedances of the defined daily and annual limit values, at both national and European level. Although exceedances were not as pronounced as in the period before the implementation of the new technology, the episodes of extreme air pollution with SO₂ persisted on the daily basis. The maximum daily SO₂ concentration of 2125 μg m^-3 was more than 100 times higher compared to the WHO AQG, but lower compared to the period before the implementation of the flash smelting technology. The air quality considering PM₁₀ and especially As levels in PM₁₀ samples was notably poorer after the modernisation. The annual target value for As, defined by the European and Serbian Regulation, was exceeded at all the measuring sites, with maximum exceedance of more than 90 times at the suburban site during 2019. The frequent exceedances of the corresponding annual limit and target values were also denoted for Pb and Cd in PM₁₀ samples. The analysed data emphasised that the Bor area could still be characterised as an environmental hotspot in Serbia and beyond.

Potential health impacts from sulphur dioxide and sulphate exposure in the UK resulting from an Icelandic effusive volcanic eruption

Ash, gases and particles emitted from volcanic eruptions cause disruption to air transport, but also have negative impacts on respiratory and cardiovascular health. Exposure to sulphur dioxide (SO₂) and sulphate (SO₄) aerosols increases the risk of mortality, and respiratory and cardiovascular hospital admissions. Ash and gases can be transported over large distances and are a potential public health risk. In 2014-15, the Bárðarbunga fissure eruption at Holuhraun, Iceland was associated with high emissions of SO₂ and SO₄, detected at UK monitoring stations. We estimated the potential impacts on the UK population from SO₂ and SO₄ associated with a hypothetical large fissure eruption in Iceland for mortality and emergency hospital admissions. To simulate the effects of different weather conditions, we used an ensemble of 80 runs from an atmospheric dispersion model to simulate SO₂ and SO₄ concentrations on a background of varying meteorology. We weighted the simulated exposure data by population, and quantified the potential health impacts that may result in the UK over a 6-week period following the start of an eruption. We found in the majority of cases, the expected number of deaths resulting from SO₂ over a 6-week period total fewer than ~100 for each model run, and for SO₄, in the majority of cases, the number totals fewer than ~200. However, the 6-week simulated period with the highest SO₂ was associated with 313 deaths, and the period with the highest SO₄ was associated with 826 deaths. The single 6-week period relating to the highest combined SO₂ and SO₄ was associated with 925 deaths. Over a 5-month extended exposure period, upper estimates are for 3350 deaths, 4030 emergency cardiovascular and 6493 emergency respiratory hospitalizations. These figures represent a worst-case scenario and can inform health protection planning for effusive volcanic eruptions which may affect the UK in the future.

Assessment of air pollution status during COVID-19 lockdown (March-May 2020) over Bangalore City in India

The coronavirus disease 2019 (COVID-19), which became a global pandemic by March 2020, forced almost all countries over the world to impose the lockdown as a measure of social distancing to control the spread of infection. India also strictly implemented a countrywide lockdown, starting from 24 March to 12 May 2020. This measure resulted in the reduction of the sources of air pollution in general: industrial, commercial, and vehicular pollution in particular, with visible improvement in ambient air quality. In this study, the impact of COVID-19 lockdown on the ambient concentration of air pollutants over the city of Bangalore (India) is assessed using Continuous Ambient Air Quality Measurement (CAAQM) data from 10 monitoring stations spread across the city. The data was obtained from Central Pollution Control Board (CPCB) and Karnataka State Pollution Control Board (KSPCB). The analysis of the relative changes in the ambient concentration of six major air pollutants (NO, NO₂, NO_X, PM_2.5, O₃, and SO₂) has been carried out for two periods: March-May 2020 (COVID-19 lockdown) and the corresponding period of 2019 during when there was no lockdown. The analysis revealed significant reduction in the concentration of ambient air pollutants at both daily and monthly intervals. This can be attributed to the reduction in sources of emission; vehicular traffic, industrial, and other activities. The average reduction in the concentration of NO, NO₂, NO_X, PM_2.5, and O₃ between 01 March and 12 May 2020 was found to be 63%, 48%, 48%, 18%, and 23% respectively when compared to the same period in 2019. Similarly, the comparative analysis of pollutant concentrations between pre-lockdown (01-23 March 2020) and lockdown (24 March-12 May 2020) periods has shown a huge reduction in the ambient concentration of air pollutants, 47.3% (NO), 49% (NO₂), 49% (NO_X), 10% (SO₂), 37.7% (PM_2.5), and 15.6% (O₃), resulting in improved air quality over Bangalore during the COVID-19 lockdown period. It is shown that the strict lockdown resulted in a significant reduction in the pollution levels. Such lockdowns may be useful as emergency intervention strategies to control air pollution in megacities when ambient air quality deteriorates dangerously.

Simultaneous sulfur dioxide and mercury removal during low-rank coal combustion by natural zeolite

Sulfur dioxide (SO₂) and trace metal such as mercury emission during combustion of low-rank coal cause a significant impact on the environment and health. Flue gas at coal-fired power stations is one of the main sources for the emissions of SO₂ and mercury metal. Low-cost and sustainable technologies for the removal of SO₂ and mercury from flue gas have become increasingly important nowadays. This paper presents the study of simultaneous removal of SO₂ and mercury over natural zeolite as an adsorbent in briquette and pulverized. The research is focused on evaluating adsorbent to coal optimum ratio towards adsorption performance on SO₂ and mercury removal. The experiments on the removal of SO₂ and mercury were carried out using horizontal electric furnace with different combustion temperature and adsorbent ratio. SO₂ in the flue gas as the result of the combustion process which exits from the outlet was analyzed using Gas Combustion and Emission Analyzer (E4400, E-Instrument). Mercury metal residues in the bottom ash were analyzed using NIC Mercury SP Analyzer. An increasing zeolite adsorbent SO₂ content in flue gas decreased. The optimum SO₂ removal was determined on 4% zeolite adsorbent ratio. It also has been found that 8% natural zeolite ratio to low-rank coal show optimum condition to adsorb mercury for all temperature condition for both briquette and pulverized conditions.

Changing air pollution scenario during COVID-19: Redefining the hotspot regions over India

The present study investigates the air pollution pattern over India during the COVID-19 lockdown period (24 March-31 May 2020), pre-lockdown (1-23 March 2020) and the same periods from 2019 using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra aerosol optical depth (AOD) with level 2 (10 km × 10 km) and level 3 (1° × 1° gridded) collection 6.1 Dark Target Deep Blue (DT-DB) aerosol product the Tropospheric Monitoring Instrument (TROPOMI) NO₂ and SO₂ data with a spatial resolution of 7 km × 3.5 km. We also use long-term average (2000-2017) of AOD for March-May to identify existing hotspot regions and to compare the variations observed in 2019 and 2020. The aim of the present work is to identify the pollution hotspot regions in India that existed during the lockdown and understanding the future projection scenarios reported by previous studies in light of the present findings. We have incorporated Menn-Kendall trend analysis to understand the AOD trends over India and percentage change in AOD, NO₂ and SO₂ to identify air pollution pattern changes during the lockdown. The results indicate higher air pollution levels over eastern India over the coal-fired power plants clusters. By considering the earlier projected studies, our results suggest that eastern India will have higher levels of air pollution, making it a new hotspot region for air pollution with highest magnitudes.

Fuel consumption and air emissions in one of the world's largest commercial fisheries

The little information available on fuel consumption and emissions by high seas tuna fisheries indicates that the global tuna fleet may have consumed about 2.5 Mt of fuel in 2009, resulting in the production of about 9 Mt of CO2-equivalent greenhouse gases (GHGs), i.e., about 4.5-5% of the global fishing fleet emissions. We developed a model of annual fuel consumption for the large-scale purse seiners operating in the western Indian Ocean as a function of fishing effort, strategy, and vessel characteristics based on an original and unique data set of more than 4300 bunkering operations that spanned the period 2013-2019. We used the model to estimate the total fuel consumption and associated GHG and SO2 emissions of the Indian Ocean purse seine fishery between 1981 and 2019. Our results showed that the energetic performance of this fishery was characterized by strong interannual variability over the last four decades. This resulted from a combination of variations in tuna abundance but also changes in catchability and fishing strategy. In recent years, the increased targeting of schools associated with fish aggregating devices in response to market incentives combined with the IOTC management measure implemented to rebuild the stock of yellowfin tuna has strongly modified the productivity and spatio-temporal patterns of purse seine fishing. This had effects on fuel consumption and air pollutant emissions. Over the period 2015 to 2019, the purse seine fishery, including its support vessel component, annually consumed about 160,000 t of fuel and emitted 590,000 t of CO2-eq GHG. Furthermore, our results showed that air pollutant emissions can be significantly reduced when limits in fuel composition are imposed. In 2015, SO2 air pollution exceeded 1500 t, but successive implementation of sulphur limits in the Indian Ocean purse seine fishery in 2016 and 2018 have almost eliminated this pollution. Our findings highlight the need for a routine monitoring of fuel consumption with standardized methods to better assess the determinants of fuel consumption in fisheries and the air pollutants they emit in the atmosphere.

Phenylacetaldehyde real-time release kinetics in wine like model solutions

The present work shows key possibilities in modelling the kinetics of phenylacetaldehyde formation as a function of sugar, phenolic compounds, metals and sulphur dioxide. The release kinetics were measured online by proton transfer reaction-mass spectrometry (PTR-MS). Phenylacetaldehyde formation was fitted using Weibull models and an activation energy of 73 kJ/mol estimated. Also, a confirmation that glucose can inhibit the aldehyde formation was demonstrated, and the sequential additions in real time showed that the inhibition level was dependent on metal ions presence. Moreover, for the first time it was observed in real time the capacity of SO₂ to bind with phenylacetaldehyde, and by trapping it, lowering its release. Finally, the impact of pH and temperature in the stability of the formed adducts and underling release mechanism is also elucidated.

Pre-fermentative maceration with SO2 enhanced the must aromatic composition

SO₂ is the additive most used in winemaking, due to its antioxidant and antiseptic activities. There have been several studies focused on these activities; however, there are hardly any studies that address its role as extractant. Therefore, the objective of this work was to study the effect of SO₂ on the must volatile composition after a pre-fermentation maceration. The results showed that the influence of SO₂ on the extraction of the two most important families of varietal compounds, terpenoids and C₁₃ norisoprenoids, was different: the content of total terpenoids increased by 95%, while for the total of C₁₃ norisoprenoids no significant differences were observed. The other three families of volatile compounds studied, benzenoid compounds, esters, and C6 compounds, were found in greater quantity in the samples with SO₂, increasing by 51%, 164%, and 45%, respectively. Consequently, SO₂ can enhance the must aromatic composition of neutral varieties, such as Tempranillo.

Significant change in air quality parameters during the year 2020 over 1st smart city of India: Bhubaneswar

Prevention of Coronavirus results in lockdown in India from 24 March 2020 to 31 May 2020. Eastern India, which is having a dense cluster of coal-fired power plants and home to many mines, mineral industries, has not shutdown power plants and coal mines during this lockdown period, though other industrial and vehicular emissions were almost zero. The present study attempts to find the change in various atmospheric pollutants during this lockdown period over an eastern tropical Indian station-Bhubaneswar, which is the first smart city proposed in smart city mission of Government of India. The study analyses hourly concentrations of PM_2.5, PM₁₀, NO _X , O₃, and CO for March-May 2019 and 2020. The study shows a significant increase (rather than decrease) in PM_2.5 and PM₁₀, increase in O₃ and a decrease in CO and NO _X during the lockdown period. Results are advocating the impact of transported pollution over the study area for maintaining the PM_2.5 and PM₁₀ values even during the lockdown situation.

Mortality risks due to long-term ambient sulphur dioxide exposure: large variability of relative risk in the literature

Several studies have been published about the potential health effects due to long-term exposure to sulphur dioxide (SO₂) and the relative risks (RRs) for different causes of mortality. Broad differences in the RR values are found, however. In this study, we performed an analysis of these studies aiming finding potential explanations for the high variability of the RR reported. The RRs for stratified subgroups were also analysed to identify more susceptible subgroups. A total of 14 studies were identified. Some of them related strong associations between mortality and long-term ambient SO₂ exposure, while others found insignificant or no associations to the same mortality indexes. The mean RR values ranged from 0.95 to 1.14 for mortality due to all causes, 0.99 to 3.05 for lung cancer, 0.87 to 1.3 for respiratory diseases, 0.96 to 1.14 cardiovascular diseases and 0.97 to 1.05 for cardiopulmonary diseases mortality. Among the factors that may affect the RR estimations, only the size of studied population and the spatial scales used in exposure assessment showed notable influences. The female population was found to be more susceptible to long-term SO₂ exposure. For other stratified subgroups including age, smoking status and income levels, no obvious relationship with RR was observed.

Assessment of the potential for in-plume sulphur dioxide gas-ash interactions to influence the respiratory toxicity of volcanic ash

BACKGROUND

Volcanic plumes are complex environments composed of gases and ash particles, where chemical and physical processes occur at different temperature and compositional regimes. Commonly, soluble sulphate- and chloride-bearing salts are formed on ash as gases interact with ash surfaces. Exposure to respirable volcanic ash following an eruption is potentially a significant health concern. The impact of such gas-ash interactions on ash toxicity is wholly un-investigated. Here, we study, for the first time, whether the interaction of volcanic particles with sulphur dioxide (SO₂) gas, and the resulting presence of sulphate salt deposits on particle surfaces, influences toxicity to the respiratory system, using an advanced in vitro approach.

METHODS

To emplace surface sulphate salts on particles, via replication of the physicochemical reactions that occur between pristine ash surfaces and volcanic gas, analogue substrates (powdered synthetic volcanic glass and natural pumice) were exposed to SO₂ at 500 °C, in a novel Advanced Gas-Ash Reactor, resulting in salt-laden particles. The solubility of surface salt deposits was then assessed by leaching in water and geochemical modelling. A human multicellular lung model was exposed to aerosolised salt-laden and pristine (salt-free) particles, and incubated for 24 h. Cell cultures were subsequently assessed for biological endpoints, including cytotoxicity (lactate dehydrogenase release), oxidative stress (oxidative stress-related gene expression; heme oxygenase 1 and NAD(P)H dehydrogenase [quinone] 1) and its (pro-)inflammatory response (tumour necrosis factor α, interleukin 8 and interleukin 1β at gene and protein levels).

RESULTS

In the lung cell model no significant effects were observed between the pristine and SO₂-exposed particles, indicating that the surface salt deposits, and the underlying alterations to the substrate, do not cause acute adverse effects in vitro. Based on the leachate data, the majority of the sulphate salts from the ash surfaces are likely to dissolve in the lungs prior to cellular uptake.

CONCLUSIONS

The findings of this study indicate that interaction of volcanic ash with SO₂ during ash generation and transport does not significantly affect the respiratory toxicity of volcanic ash in vitro. Therefore, sulphate salts are unlikely a dominant factor controlling variability in in vitro toxicity assessments observed during previous eruption response efforts.

Air pollutants and outpatient visits for cardiovascular disease in a severe haze-fog city: Shijiazhuang, China

Background

Many studies have reported the impact of air pollution on cardiovascular disease (CVD), but few of these studies were conducted in severe haze-fog areas. The present study focuses on the impact of different air pollutant concentrations on daily CVD outpatient visits in a severe haze-fog city.

Methods

Data regarding daily air pollutants and outpatient visits for CVD in 2013 were collected, and the association between six pollutants and CVD outpatient visits was explored using the least squares mean (LSmeans) and logistic regression. Adjustments were made for days of the week, months, air temperature and relative humidity.

Results

The daily CVD outpatient visits for particulate matter (PM₁₀ and PM_2.5), sulphur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃) in the 90th-quantile group were increased by 30.01, 29.42, 17.68, 14.98, 29.34%, and − 19.87%, respectively, compared to those in the <10th-quantile group. Odds ratios (ORs) and 95% confidence intervals (CIs) for the increase in daily CVD outpatient visits in PM₁₀ 300- and 500-μg/m³, PM_2.5 100- and 300-μg/m³ and CO 3-mg/m³ groups were 2.538 (1.070–6.020), 7.781 (1.681–36.024), 3.298 (1.559–6.976), 8.72 (1.523–49.934), and 5.808 (1.016–33.217), respectively, and their corresponding attributable risk percentages (AR%) were 60.6, 87.15, 69.68, 88.53 and 82.78%, respectively. The strongest associations for PM₁₀, PM_2.5 and CO were found only in lag 0 and lag 1. The ORs for the increase in CVD outpatient visits per increase in different units of the six pollutants were also analysed.

Conclusions

All five air pollutants except O₃ were positively associated with the increase in daily CVD outpatient visits in lag 0. The high concentrations of PM₁₀, PM_2.5 and CO heightened not only the percentage but also the risk of increased daily CVD outpatient visits. PM₁₀, PM_2.5 and CO may be the main factors of CVD outpatient visits.

Optimization of activated palm oil sludge biochar preparation for sulphur dioxide adsorption

Palm oil sludge (POS) is an organic waste generated from the palm oil industry. POS causes environmental pollution if it is improperly disposed. In this study, the potential of activated POS biochar, as an adsorbent for the removal of SO₂ gas was tested. POS biochar was physically activated using CO₂ gas. The effects of activation preparation variables i.e. activation temperature (300-700 °C), activation time (30-150 min) and CO₂ flow rate (100-500 ml/min) were investigated using design expert version 8.0.7.1 software. Central Composite Design (CCD) was used to develop a quadratic model to correlate the operating variables with the activated biochar adsorption capacity. Analysis of variance (ANOVA) was performed to identify the significant factors on the experimental design response. The optimum preparation conditions of activated POS biochar were found to be at activation temperature of 442 °C, activation time of 63 min and CO₂ flow rate of 397 ml/min. The maximum adsorption capacity at the optimum conditions was recorded as 16.65 mg/g. The adsorption capacity increased significantly after the activation process. Characteristics of the activated POS biochar proposed that SO₂ was physically adsorbed. Furthermore, it was found that the adsorption capacity can be further enhanced by increasing the reaction temperature to 100 °C or with 15% of relative humidity in the inlet gas. The prepared adsorbents can be regenerated by thermal treatment.

A PET/paper chip platform for high resolution sulphur dioxide detection in foods

A convenient assay platform comprising a PET/paper chip (PP-chip) and a smart analytical device is developed for detection of sulphur dioxide (SO₂) concentration. In the presented approach, the distilled SO₂ solution is dropped onto the detection region of the PP-chip and undergoes a reaction with an acid-based reagent. The resulting color variation is analyzed through a high-resolution camera (CMOS) and the reacted image is processed by a RGB (red, green and blue) analytical app installed on a smartphone. Results show that the known SO₂ concentrations ranging from 10 to 300 ppm indicate that the high linear relationship (R² = 0.9981) between the (R (red) + G (green) - B (blue)) value and SO₂ concentration. Moreover, a high measurement resolution is equal to 1.45 ppm/a.u. The presented assay platform was proved to detect the SO₂ concentrations of twenty-five practical food samples. Compared with the developed assay platform and certified inspection technique, the deviation of SO₂ measurement does not exceed 3.82%. It was satisfactory to apply this developed assay platform to analyze the SO₂ concentration in the practical samples.

Sulphur dioxide and arsenic affect male reproduction via interfering with spermatogenesis in mice

As two potential environmental hazards, sulphur dioxide (SO₂) and arsenic have adverse effects on male reproduction, but the mechanism of which and their combined toxicity are not clear. In this study, we investigate male reproductive toxicity with a focus on spermatogenesis by treating mice with 5 mg/m³ SO₂ and/or 5 mg/L arsenic. Our results showed that arsenic exposure caused significant decreases in water and food consumption and body weight in mice, whereas these changes were not observed in the SO₂-only group. Both SO₂ and arsenic reduced sperm counts, increased the percentage of sperm malformation, and induced abnormal testicular pathological changes. Elevated H₂O₂ and MDA contents, declined T-SOD activity, decreased spermatogenic cell counts, enhanced caspase-3 activity, and increased TUNEL-positive cells were also observed in mice exposed to SO₂ and/or arsenic. Moreover, SO₂ and arsenic co-exposure changed the mRNA levels of Bax and Bcl-2, decreased serum testosterone levels, and downregulated the expression of steroidogenic-related genes (LHR, StAR, and ABP) in mice. These findings provide a new theoretical basis for understanding how SO₂ and arsenic interfere with spermatogenesis leading to infertility. These results also suggest that SO₂ and arsenic co-exposure likely result in an additive effect on male reproductive toxicity in mice.

Sulphur dioxide ameliorates colitis related pathophysiology and inflammation

Colitis is an inflammatory disease of the gastrointestinal tract. Inflammation, oxidative stress and cell death constitute the backbone of colitis. Most of the drugs prescribed for inflammatory bowel disease (IBD) have various side effects. In this scenario, we would like to determine the therapeutic role sulphur dioxide, a gaso-transmitter produced through the metabolism of cysteine in colitis. Colitis was induced through intrarectal administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in male Wistar rats. Rats were administered with 0.9% saline containing Na₂SO₃ and NaHSO₃ (3:1 ratio; i.e., 0.54 mmol/kg and 0.18 mmol/kg body weight) orally 1 h after colitis induction followed by the administration of the same solution after each 12 h for 72 h. TNBS administration resulted in increased oxidative stress, NF-ĸ B and inflammasome activation, ER stress and autophagy. Moreover, TNBS administration also resulted in activation of p53 and apoptosis. SO₂ reversed all these alterations and ameliorated colitis in rats. Administration of an inhibitor of endogenous SO₂ production along with TNBS exacerbated colitis. Results suggest that down-regulation of SO₂ / glutamate oxaloacetate transaminase pathway is involved in IBD. The protective role of SO₂ in colitis is attributed to its anti-inflammatory and anti-oxidant nature. Down-regulation of SO₂/glutamate oxaloacetate transaminase pathway is involved in IBD. Since SO₂ is not toxic at low concentration and endogenously produced, it may be used with prescribed drugs for synergistic effect after intensive research. Our result demonstrated the therapeutic role of SO₂ in colitis for the first time.

Evaluation of total polyphenol content of wines by means of voltammetric techniques: Cyclic voltammetry vs differential pulse voltammetry

Taking advantage of the low oxidation potential of polyphenolic compounds, voltammetric techniques, such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are used rather indiscriminately. In this work, we report Total Polyphenols results (TPP) obtained by these two techniques from a set of nine samples of red and Tawny Port wine. The CV and DPV voltammograms display significant correlations with the physical-chemical parameters used to characterize red and Tawny Port wines, particularly with polyphenols. Although data obtained from CV and DPV for a single polyphenol are directly proportional, important deviations are found between voltammetric results from wines. Results from CV tend to be larger than those from DPV. This difference, that can reach 50% of the TPP value, was related to the presence of total sulphur dioxide. In view of the present study, the polyphenol quantification in wines should be performed by DPV to minimize the interference of SO₂.

Brettanomyces bruxellensis yeasts: impact on wine and winemaking

Yeasts belonging to the Brettanomyces/Dekkera genus are non-conventional yeasts, which affect winemaking by causing wine spoilage all over the world. This mini-review focuses on recent results concerning the presence of Brettanomyces bruxellensis throughout the wine processing chain. Here, culture-dependent and independent methods to detect this yeast on grapes and at the very early stage of wine production are encompassed. Chemical, physical and biological tools, devised for the prevention and control of such a detrimental species during winemaking are also presented. Finally, the mini-review identifies future research areas relevant to the improvement of wine safety and sensory profiles.

The effects of Sulphur dioxide on acute mortality and years of life lost are modified by temperature in Chengdu, China

The effect modification of meteorological factors on the association between ambient Sulphur dioxide (SO₂) and mortality is critical for designing intervention policy. Existing studies did not result in consistent conclusions on the effect modification, and Years of life lost (YLLs) was rarely used as a health impact indicator to examine the modifying effect. This study aims to estimate the mean air temperature and relative humidity modification effects on the impact of SO₂ on daily mortality and YLLs in Chengdu, China. Mortality, YLLs, air pollution and meteorological data were collected for 2011-2014. Three analytical approaches based on generalized additive models (GAMs) were used, including bivariate response surface model, product term model, and stratification model. We found that the effects of SO₂ on mortality and YLLs depended on temperature at various lags, but did not depend on relative humidity. SO₂ exhibited larger adverse effects on mortality in high temperature level (22.8-29.4°C) days than in low temperature level (-0.3-9.3°C) days, with a 10μg/m³ increment in SO₂, non-accidental death increased by 0.8% (0.001, 0.015)at low temperature level, but increased by 1.4% (0.005, 0.024) at high temperature level. On the contrary, SO₂ showed greater adverse effects on YLLs in low temperature days than in high temperature days, with a 10μg/m³ increment in SO₂, non-accidental YLL increased by 40.580 (31.478, 49.682) at high temperature level, but increased by -2.703 (-14.668, 9.261) at low temperature level. We concluded that the effect of SO₂ on mortality and YLLs may depend on temperature in Chengdu, China. Our results highlight the importance of considering the interaction between SO₂ and temperature on health outcomes in future research. Also, policy makers should enhance the emission control of SO₂ in extreme temperature days in Chengdu.

Air pollution and fasting blood glucose: A longitudinal study in China

Limited studies have examined the associations between air pollutants [particles with diameters of 10 μm or less (PM10), sulphur dioxide (SO2), and nitrogen dioxide (NO2)] and fasting blood glucose (FBG). We collected data for 27,685 participants who were followed during 2006 and 2008. Generalized Estimating Equation models were used to examine the effects of air pollutants on FBG while controlling for potential confounders. We found that increased exposure to NO2, SO2 and PM10 was significantly associated with increased FBG levels in single pollutant models (p<0.001). For exposure to 4 days' average of concentrations, a 100 μg/m(3) increase in SO2, NO2, and PM10 was associated with 0.17 mmol/L (95% CI: 0.15-0.19), 0.53 mmol/L (95% CI: 0.42-0.65), and 0.11 mmol/L (95% CI: 0.07-0.15) increase in FBG, respectively. In the multi-pollutant models, the effects of SO2 were enhanced, while the effects of NO2 and PM10 were alleviated. The effects of air pollutants on FBG were stronger in female, elderly, and overweight people than in male, young and underweight people. In conclusion, the findings suggest that air pollution increases the levels of FBG. Vulnerable people should pay more attention on highly polluted days to prevent air pollution-related health issues.

The interaction between air pollution and diet does not influence the DNA damage in lymphocytes of pregnant women

The aim of the study was to evaluate the risk of DNA damage in lymphocytes of pregnant women with respect to hormonal and nutritional status and to air pollution in Lesser Poland. The study was performed on 39 healthy pregnant women. The oxidative DNA damage, alkali-labile sites and uracil in DNA of lymphocytes were measured by using the comet assay. The concentration of 17beta-estradiol, progesterone, DHEA, cholesterol, vitamin B12 and folates were determined. Dietary data were assembled from food diaries. Voivodeship Inspectorate for Environmental Protection in Krakow using automatic pollution monitoring system provided the air pollution information, such as concentrations of PM10, PM2.5, NO, NO2, SO2, CO and O3. Many statistical correlations between DNA damage and air pollutants concentration were found however their biological meaning is still to be explained. It should be taken under consideration, that the protective effect of air pollutants is a result of hormesis, as the measured amounts of air pollutants during the study did not exceed the admissible levels. There was found no diet-and air pollution interaction.

Measuring protection of aromatic wine thiols from oxidation by competitive reactions vs wine preservatives with ortho-quinones

Quinones are central intermediates in wine oxidation that can degrade the quality of wine by reactions with varietal thiols, such as 3-sulfanylhexanol, decreasing desirable aroma. Protection by wine preservatives (sulphur dioxide, glutathione, ascorbic acid and model tannin, phloroglucinol) was assessed by competitive sacrificial reactions with 4-methyl-1,2-benzoquinone, quantifying products and ratios by HPLC-UV-MS. Regioselectivity was assessed by product isolation and identification by NMR spectroscopy. Nucleophilic addition reactions compete with two electron reduction of quinones by sulphur dioxide or ascorbic acid, and both routes serve as effective quenching pathways, but minor secondary products from coupled redox reactions between the products and reactants are also observed. The wine preservatives were all highly reactive and thus all very protective against 3-sulfanylhexanol loss to the quinone, but showed only additive antioxidant effects. Confirmation of these reaction rates and pathways in wine is needed to assess the actual protective action of each tested preservative.

Determination of the wine preservative sulphur dioxide with cyclic voltammetry using inkjet printed electrodes

During winemaking sulphur dioxide is added to prevent undesirable reactions. However, concerns over the harmful effects of sulphites have led to legal limits being placed upon such additives. There is thus a need for simple and selective determinations of sulphur dioxide in wine, especially during winemaking. The simultaneous detection of polyphenols and sulphur dioxide, using cyclic voltammetry at inert electrodes is challenging due to close oxidation potentials. In the present study, inkjet printed electrodes were developed with a suitable voltammetric signal on which the polyphenol oxidation is suppressed and the oxidation peak height for sulphur dioxide corresponds linearly to the concentration. Different types of working electrodes were printed. Electrodes consisting of gold nanoparticles mixed with silver showed the highest sensitivity towards sulphur dioxide. Low cost production of the sensor elements and ultra fast determination of sulphur dioxide by cyclic voltammetry makes this technique very promising for the wine industry.

A comparative adsorption study of C2H4 and SO2 on clinoptilolite-rich tuff: effect of acid treatment

In this study, ethylene (C2H4) and sulphur dioxide (SO2) adsorption properties of clinoptilolite tuff from Gördes, Turkey and that of acid treated forms were studied at 293K using volumetric apparatus up to 38 and 100 kPa, respectively. In order to consider the effect of acid treatment on structural and gas adsorption properties of zeolite, clinoptilolite mineral was modified with 0.1, 0.5, 1.0 and 2.0M HCl solutions at 70 °C during 3h. XRD, XRF, TG/DTG, DTA and N2 adsorption methods were employed for thermal and structural characterization of clinoptilolite samples before and after the acid treatment. SO2 adsorption capacities (2.356-2.739 mmol/g) of the clinoptilolite samples were superior to those of the C2H4 adsorptions (0.619-1.219 mmol/g).

Short-term changes of fructans in ryegrass (Lolium multiflorum 'Lema') in response to urban air pollutants and meteorological conditions

We investigated whether the fructan content, a storage carbohydrate, of Lolium multiflorum 'Lema' plants grown in a subtropical urban environment characterized by typical diurnal profiles of air pollutants and meteorological conditions changed over the course of a day during different seasons. Plants were collected every 2h on the last day of each two-month seasonal field experiment and separated into shoot (stubble or stubble+leaf blades) and roots for carbohydrate analyses and biomass determination. Diurnal contents of total fructose in the stubbles increased with high temperatures. In the roots, fructose accumulation showed a positive relation with hourly variations of both temperature and particulate matter and a negative relation with irradiance and SO2. Seasonal variation in shoot and root biomasses coincided with the seasonal variation of total fructose and were negatively affected by relative humidity and SO2, respectively. We concluded that hourly changes of fructans over the course of a day may increase the ability of L. multiflorum to tolerate short-term oscillations in weather and air pollution commonly observed in the subtropical urban environment, increasing its efficiency in monitoring air quality.

Are geckos useful bioindicators of air pollution?

The response of an Australian arid-zone gecko community to sulphur dioxide and salt spray from a mine and industrial site was investigated from 1992 to 1995. Geckos were abundant and fecund at control sites in chenopod shrubland and annual capture rates were strongly influenced by minimum night temperatures. Capture rate and percentage of females gravid at sites exposed to high concentrations of air pollutants were significantly lower than at control sites. Discrepancies between control and impacted sites were greatest for the termite-specialist geckos Diplodactylus conspicillatus and Rhynchoedura ornata. An increase in capture rates and percentage of females gravid at sites close to the industrial site, followed a reduction in peak sulphur dioxide emissions. Geckos may be sensitive and useful bioindicators of the environmental impacts of some atmospheric pollutants.

Decomposition rates and fungal respiration

Ash (Fraxinus excelsior L.), birch (Betula spp.), hazel (Corylus avellana L.), sessile oak [Quercus petraea (Mattuschka) Liebl.] and sycamore (Acer pseudoplatanus L.) leaf litters from a virtually non-polluted and a heavily sulphur dioxide (SO₂ )-polluted woodland were fumigated with environmentally-realistic concentrations (0.010-0.030μl l^-1 ) of SO₂ for 16-68 wk in an open-air field-fumigation experiment. Fumigation inhibited the respiration (CO₂ evolution) and decomposition rates of the leaf litters. However, there were few differences in the responses between leaf litters from the two woodlands. In addition, pure cultures of four saprotrophic fungi were grown individually on irradiated hazel litter and exposed to c. 0.030μl l^-1 of gaseous SO² , for 28 d in the laboratory. The gas inhibited the respiration of Phoma exigua Desm. and Phoma macrostoma Mont, but not the respiration of Cladosporium cladosporioides (Fres.) de Vries or Coniothyrium quercinum Sacc. var. glandicola Grove. These results in part substantiated findings of previous experiments examining the effects of SO₂ on the structures of saprotrophic fungal communities. The effects of SO₂ on fungal decomposition of angiosperm tree leaf litter as possible causes of forest decline are discussed.

Chemical content of leaf litters

Ash (Fraxinus excelsior L.), birch (Betula spp.), hazel (Corylus avellana L.), sessile oak [Quercus petraea (Mattuschka) Liebl.] and sycamore (Acer pseudoplatanus L.) leaf litters from a non-polluted and a heavily sulphur dioxide (SO₂ )-polluted woodland were fumigated with environmentally-realistic concentrations (0.010-0.030 μl l^-1 ) of SO₂ for 16-68 wk in an open-air field-fumigation experiment. Fumigation markedly increased sulphate and protons in leachates from the litters and decreased calcium and magnesium contents of the leaves. However, there were few differences in the responses between leaf litters from the two woodlands. This was attributed to rapid sulphate wash-out from the litters from the heavily polluted woodland, so that the litters from the two sites quickly reached the same sulphate status.

Changes in communities of fungal saprotrophs

Comparisons of the saprotrophic fungi isolated from ash (Fraxinus excelsior L.), birch (Betula spp.), hazel (Corylus avellana L.), pedunculate oak (Quercus robur L.), sessile oak [Q. petraea (Mattuschka) Liebl.] and sycamore (Acer pseudoplatanus L.) leaf litters from three woodlands exposed to low, medium and high levels (c. 0.0→ 0.060μl l^-1 ) of sulphur dioxide (SO₂ ) showed that the composition of the fungal communities differed between sites. Fumigation of angiosperm tree leaf litters from the least and the most polluted site with environmentally-realistic concentrations (0.010-0.030 μl¹ ) of SO₂ for 16-68 wk in an open-air field-fumigation experiment resulted in marked changes in the composition of the fungal communities in the leaf litters, comparable with differences found between the woodland sites. Cladosporium spp., Epicoccutn nigrum Link, Fitsarium spp. and Phoma exigua Desm. were less commonly isolated from leaf litters exposed to SO² , whereas Coniothyrium quercinum Sacc. var. glandicola Grove, Cylindrocarpon orthosporum (Sacc.) Wollenw. and Penicillium spp. were more frequently isolated from fumigated litters. However, few differences could be detected in the response to SO₂ of the mycofloras of leaf litters originating from different woodland sites. In general, SO₂ did not affect the total extent of fungal occupancy of the microsites in the litter, as fungal species which decreased in abundance on exposure to the gas appeared to be replaced in the litter by other species more tolerant to the gas. SO₂ therefore appeared to be selectively toxic to saprotrophic fungi isolated from these litters.

Growth responses of barley exposed to SO2

Barley (Hordeum vulgare ev. Schooner) plants were exposed to 4, 42, 121, 256 or 517 nl 1^-l SO₂ to investigate the relationship between the exposure concentration of SO² and growth. The plants were exposed from 14 days old, in open-top chambers for 4 h day^-1 (10.00-14.00 h) for 79 days. The concentration-response curves established illustrated a small growth stimulation (approx. 10%) at 42 nl 1^-1 and a growth inhibition at 121 nl 1^1- or greater. The growth reduction was generally proportional to the exposure concentration at concentrations above 42 nl 1^-1 Sulphur concentration in the shoot increased linearly with ambient SO₂ concentration.

Gas exchange and SO2 fumigation studies with irrigated and unirrigated field grown Diplacus aurantiacus and Heteromeles arbutifolia

Experiments were performed on an evergreen (Heteromeles arbutifolia) and a drought deciduous shrub (Diplacus aurantiacus) to determine, 1) whether approaches for evaluating SO₂ absorption by leaves in laboratory studies could be extended to field studies, 2) the effects of irrigation on metabolism and SO₂ responses of the study species during a season when water was limiting, 3) to interpret SO₂ responses on the basis of SO₂ flux rates. Laboratory-developed approaches for evaluating SO₂ absorption by leaves were found to be suitable for use with field plants, despite field plants having lower gas exchange rates. Supplementing water during times of deficit did not override all the biological and environmental factors that limited photosynthesis (A). Irrigation increased leaf longevity of D. aurantiacus, and stomatal conductance to water vapour (g); g was also shown to increase with H. arbutifolia on irrigation. Irrigation profoundly influenced plant response to SO₂. Unwatered D. aurantiacus had only a small g and therefore a reduced capacity to absorb SO₂ and respond to SO₂; which resulted in apparent SO₂ avoidance. Water availability and SO₂ both affect g and therefore, SO₂ flux rates into the mesophyll. Different ambient SO₂ concentrations of 8.3 and 26.2 μmol m^-3 (0.2 and 0.6 ppm) were both found to result in similar SO₂ flux rates into the leaf, due to variations in g in response to water availability. Changes in g did not always result in changes in A, implying that carbon fixation may be little affected by some SO₂ exposures, although still potentially affecting such processes as maintenance of leaf water potential, transpirational cooling and nutrient uptake.