Ground-level SO2 Concentrations Research Articles

Modeling SO2 dispersion from future eruptions in the Auckland Volcanic Field, New Zealand

Auckland city (pop. 1.7 M) is Aotearoa New Zealand’s largest city and an important economic hub. The city is built upon the active intraplate basaltic Auckland Volcanic Field (AVF). An AVF eruption would cause considerable impacts. An important component of volcanic risk management is assessing the likely volcanic hazards to help inform emergency planning and other preparedness activities. Previous volcanic hazard assessments for the AVF, particularly those for emergency planning scenarios, have modeled multiple volcanic hazards including lava flows, pyroclastic density currents, ballistic projectiles and tephra fall. Despite volcanic gas being an important and impactful hazard from intraplate basaltic field eruptions, there has been limited consideration of volcanic gas in AVF hazard assessment to date. This project is one of the first to quantitatively assess potential volcanic gas hazards for an explosive eruption scenario. For basaltic volcanism, sulfur dioxide (SO2) gas is typically the most consequential volcanic gas emitted. The aim of this exploratory study was to model SO2 dispersion from a high impact eruption during weather conditions conducive to high ground level pollutant concentrations. Since ground level SO2 concentrations are influenced by complex wind patterns resulting from interactions of locally driven flow circulations and topographically influenced weather, we modeled SO2 dispersion using the HYSPLIT model, a state-of-the art hybrid Eulerian and Lagrangian dispersion model widely used for volcanic gases, using high-resolution meteorological forcing fields given by the Weather Research and Forecasting (WRF) model.Modeled air parcel trajectories and ground level SO2 concentrations illustrate the effect of the converging sea breeze winds on SO2 dispersion. Under worst-case dispersion conditions, extensive areas of up to hundreds of square kilometers to the north and northwest of the eruption location would exceed New Zealand short-term (24 h) air quality standards and guidelines for SO2, indicating heightened health risks to downwind communities. Using this numerical modeling approach, this work presents a methodology for future applications to other AVF eruption scenarios, with a wider range of meteorological conditions that can help in exploring consequences for health services such as anticipated emergency department respiratory admissions.

Estimation of the ground-level SO2 concentration in eastern China based on the LightGBM model and Himawari-8 TOAR

Sulfur dioxide (SO2) is one of the main pollutants in China’s atmosphere, but the spatial distribution of ground-based SO2 monitors is too sparse to provide a complete coverage. Therefore, obtaining a high spatial resolution of SO2 concentration is of great significance for SO2 pollution control. In this study, based on the LightGBM machine learning model, combined with the top-of-atmosphere radiation (TOAR) of Himawari-8 and additional data such as meteorological factors and geographic information, a high temporal and spatial resolution TOAR-SO2 estimation model in eastern China (97–136°E, 15–54°N) is established. TOAR and meteorological factors are the two variables that contribute the most to the model, and both of their feature importance values exceed 30%. The TOAR-SO2 model has great performance in estimating ground-level SO2 concentrations with 10-fold cross validation R2 (RMSE) of 0.70 (16.26 μg/m3), 0.75 (12.51 μg/m3), 0.96 (2.75 μg/m3), 0.97 (2.16 μg/m3), and 0.97 (1.71 μg/m3) when estimating hourly, daily, monthly, seasonal, and annual average SO2. Taking North China as main study area, the annual average SO2 is estimated. The concentration of SO2 in North China showed a downward trend since 2016 and decreased to 15.19 μg/m3 in 2020. The good agreement between ground measured and model estimated SO2 concentrations highlights the capability and advantage of using the model to monitor spatiotemporal variations of SO2 in Eastern China.

Trade-driven relocation of ground-level SO2 concentrations across Chinese provinces based on satellite observations.

The influence of trade on ground-level SO2 concentrations in China was evaluated based on multiregional input-output (MRIO) analysis, using the ozone monitoring instrument (OMI) SO2 columns and SO2 profiles from an atmospheric chemical and transport model, MOZART-4. The provincial sum of ground-level SO2 concentrations has a good consistency with the provincial SO2 emissions (R = 0.65, p < 0.01). The provincial SO2 concentrations presented strong spatial variations, with a range of 5.1-50.6μg/m3 and an average of 19.7μg/m3 across China. The international trade increased the SO2 concentrations in all of the provinces and increased the national population-weighted SO2 (PWM-SO2) concentration by 2.9μg/m3. Interprovincial trade within China decreased the ambient SO2 concentrations in Beijing, Tianjin, and Chongqing and the provinces in southeast and central China, but increased SO2 in the remaining provinces of China. In general, interprovincial trade decreased the national PWM-SO2 concentration by 5.3μg/m3.

Simulation of thermal power plant source contribution to ambient air concentration in Cam Pha City, Quang Ninh province using AERMOD dispersion model

Cam Pha, the home of three major thermal power plants including Cam Pha, Mong Duong I and Mong Duong II, is one of the most important industrial cities in the North of Vietnam. Air pollution due to stacks emission is the biggest problem threatening Cam Pha City's sustainable development. In this study, the AERMOD modeling system was used to evaluate the impact of the stack emission by the thermal power plants on the ambient atmospheric environment. The maximum 1-HR, 24-HR, 99th percentile and annual average concentrations of TSP, SO2 and NO2 were simulated within the 40x40 km domain of 100x100 m grid spacing with the hourly meteorological data taken from 2018 to 2020. Air dispersion simulation is performed on the observed background gas concentration of the everyday environment. Hourly emission data of 10 primary stack sources of 3 factory groups were used as input data. The simulated spatial distribution of gases indicates the strong fluence of the mountainous topography on the dispersion of stack emission. Results also revealed that the maximum short-term stack emission at ground-level concentrations of SO2 and NO2 are much higher than the national standard, thus raising the risk of severe pollution. TSP pollution is less severe than SO2 and NO2 but still at a dangerous level. Since Cam Pha locates by the East Sea with the prevailing wind is heading northeast and east directions. The annual average concentrations of these pollutants indicate that the high terrain areas at the south and northwest of Cam Pha City, which block the flow of the stack emission, are the most affected regions by exhausted gases from industrial stacks.

Effects of Building Energy Efficiency Measures on Air Quality at the Neighborhood Level in Athens, Greece

The high concentration of pollutant sources, complex topography, and regional meteorology are all factors that may contribute to air episodes in dense urban areas. Energy use in buildings is a significant source of pollution in the Greater Athens Area (GAA), Greece, where over 90% of the existing building stock has been classified below energy class B. The present study focuses on the potential effects that a realistic level of building energy efficiency upgrades will have on the air quality over the GAA. Results are expected to be relevant to similar urban areas. Furthermore, the study of primary pollutants’ dispersion is applied at a 1.2 × 1.2 km spatial resolution, providing significant local (neighborhood) level information. Numerical simulations were performed using EPA’s CALPUFF modeling system with wind field input from an independent numerical weather prediction using NCAR’s Weather Research and Forecasting (WRF) model. In order to calculate emission rates from major roads, highways, shipping ports, residential heating installations, and major industrial facilities, data were taken from National and European statistics, demographics, and local topography. After validation, the modeling system was used to examine three building energy efficiency upgrade scenarios, implemented on 20% of the buildings. Ground level concentrations of SO2, NOx, CO, and PM10 were calculated and reductions of up to 9% were found for GAA maximum values but up to 18% for local values that were also close to or above the European safety thresholds.

Long-term ambient SO2 concentration and its exposure risk across China inferred from OMI observations from 2005 to 2018

Long-term trends in the ambient SO2 concentrations across China from 2005 to 2018 were estimated using Ozone Monitoring Instrument (OMI) SO2 columns and an atmospheric SO2 profile simulated by the Model for Ozone And Related Chemical Tracers (MOZART)-4. The estimated ground-level SO2 concentrations were in strong agreement with the ground observations (R = 0.86, root-mean-square error = 10.49 μg/m3, relative prediction error = 19%). From 2005 to 2018, the average ground-level SO2 concentration ranged from 0.97 to 106.41 μg/m3 across China, with higher values in eastern China than in western China. Considering the uneven distribution of SO2 concentration and population across China, the population-weighted SO2 concentration was estimated to be 20.30 μg/m3 on a national scale. The population-weighted SO2 levels showed decreasing trends, and the absolute values of the decreasing trend peaked in winter (1.41 μg/m3 per year), followed by those in autumn (0.92 μg/m3 per year), spring (0.74 μg/m3 per year) and summer (0.75 μg/m3 per year) from 2005 to 2018. Although the SO2 exposure risk in 2018 decreased significantly from 2005 on a national scale, 80% and 17% of people still faced a high SO2 exposure risk (higher than 20 μg/m3) in the North China Plain and Northwest China, respectively.

Assessment of shipping emission factors through monitoring and modelling studies

In this study, 3990 movements of 629 different ships approaching to the Ambarlı port of Istanbul and 10,272 movements of 2798 different ships arriving at Kocaeli port which are the largest ports of Turkey were monitored for a year between September 1, 2017 and September 1, 2018. It is well known that ship exhaust emissions have a significant impact on pollutant and global warming agent mass inputs and diminish air quality around port areas. We calculated ship exhaust emissions for three different modes by ENTEC method. The annual estimated emissions were 72,802, 1430.4, 900.3, 105.3, 60.9, and 59 tons for CO2, NOx, SO2, PM10, VOC, and CO, respectively, in Ambarlı Port. Higher emissions were estimated for Kocaeli Port due to marine traffic intensity. The annual estimated emissions at Kocaeli Port were 134,120.8, 2655.1, 1652.3, 181.4, 108.3, and 106.4 tons for CO2, NOx, SO2, PM10, VOC, and CO, respectively. In order to determine the impact of ship emissions, we employed AERMOD air quality dispersion modelling. Ground-level PM10, NOx, and SO2 concentrations were calculated. Their spatial distribution was plotted and results were evaluated by air quality measurement station results. Only estimated SO2 concentrations were higher than the observed concentrations. We concluded that ENTEC calculations produce excessive SO2 concentrations. Because sulphur content of marine fuel may vary and recent amendments in the related regulations limit its amount to lower values. Advancement of on-board SO2 emission control on ships can also have a reducing effect on emitted SO2 emissions. As a result, we emphasize that current ENTEC emission factors don't represent SO2 emissions accurately. Further, the advancement of SO2 emissions factors is required.

Effects of Improved Energy Performance of Buildings on Air Quality over the Greater Athens Area

Air pollution episodes are common in the Greater Athens Area (GAA) because of its pollutant source concentration, complex topography, and regional meteorology. For the GAA, over 90% of the existing building stock is classified below energy class B, so the effects of upgrades on energy savings are obvious and have been widely discussed. The present study focuses on the potential effects that a realistic level of implementation of the EPBD will have on the air quality over the GAA. Three renovation scenarios were examined with an implementation rate of 20%. Numerical simulation of primary pollutants’ dispersion over the GAA was performed using the CALPUFF modelling system. Ground level concentrations of SO2, NOx, CO and PM10 were calculated, taking into account pollutant releases from major roads and highways, passenger ports and cargo transport, residential heating installations and major industrial installations. The required source data was taken from National and European statistics, demographics and local topography while the Weather Research and Forecasting (WRF) model was implemented for the required high resolution meteorological field data. The modelling system was first successfully validated by comparison with available measurements of pollutant concentrations and then applied to case studies of EPBD implementation. Reductions up to ∼6% were found in the ground level concentrations of major pollutants.

Dispersion modeling of gaseous and particulate matter emissions from aircraft activity at Chania Airport, Greece

Aircraft emissions from Landing and Take-Off (LTO) cycles at Chania airport (Crete), Greece were estimated for the year 2016 adopting the International Civil Aviation Organization (ICAO) methodology and using daily data from air traffic. The AERMOD Gaussian dispersion model was elaborated to determine the ground-level concentrations of air pollutants emitted from the aircraft engines. Emissions of CO, NOx as NO2, SO2, CO2, PM2.5 mass, and particle number from aircraft engines were evaluated and ground-level concentrations of these pollutants were determined. The aircraft emissions were mainly derived from the ground-level parts of the LTO cycle. The AERMOD model referring to the 1-h average concentrations has revealed that there were 20 exceedances of NO2 concentrations above the value of 200 μg/m3; two more than the regulated threshold described in the European Union Directive 2008/50/EC.. The exceedances were calculated mostly during the summer period which coincides with the touristic period. High number concentrations of particles were also simulated close to the airport with yearly average values close to 10,000 particles per cm3 at the airport area. Contrary, the contribution from aircraft LTO cycles to the ground-level concentration of CO, SO2, and PM2.5 mass was below the air quality threshold values.

Modeling air quality impact of pollutants emitted by an oil/gas plant in complex terrain in view of a health impact assessment

The present study focuses on the estimation of the air quality impact of an oil/gas pre-treatment plant, the Centro Olio Val d’Agri (COVA), in view of a more comprehensive epidemiological study regarding the inhabitants of two small towns settled in close proximity of the plant. We used the RMS (RAMS/MIRS/SPRAY) modeling system to estimate the ground level concentration of SO2, NOx, and CO as a result of the incineration of residues and electric and thermic power generation. Simulations were run for 1 meteorological year. The spatial interpolation of measured H2S, proxy of the other types of emission, allowed for a more detailed picture of the plant impact. The spatial correlation between estimated NOx and SO2 and measured H2S strengthens the hypothesis of exploiting NOx maps as a proxy for the population exposure to the mixture of industry-emitted pollutants. Overall results suggest that the plant affects the inhabitants of the two towns differently. Furthermore, the simulations show that the area impacted by the plumes is much larger than that of the two municipalities within range of the plant, suggesting both the need to extend the monitoring area and to include the population living in that area in the health study.

Air quality monitoring and modeling near coal fired power plant

In municipality of Ugljevik (Bosnia and Herzegovina), the coal-fired thermal power plant is located in the vicinity of the populated area. The ambient air quality monitoring within this area were not systematically performed in the previous period. This research was the first to include indicative measurement of pollutant concentration in air combined with modeling techniques for the purpose of a preliminary assessment of impact which the power plant has on air quality. Since coal, with the sulfur content of 3-6%, is used, as well as the fact that there was no flue gas desulphurization during the research period, this paper shows the results for SO2 as one of the most prominent indicators of pollution originating from the power plant. As a complement to the measurements, modeling of SO2 dispersion was carried out using ADMS5 software. The measurements indicated increased ground-level concentrations of SO2. Additionally, the modeling of SO2 dispersion with real meteorological data was carried out. The modeling confirmed high SO2 concentrations in research area. Also, it was found that the high episodic ground-level SO2 concentrations are the consequence of the terrain configuration and meteorological conditions.

Evaluation of the impact of ground-level concentrations of SO2, NOx, CO, and PM10 emitted from a steel melting plant on Muscat, Oman

Steel melting plants expel multiple pollutant gasses and particles and, as a result, they impact the surrounding air quality. The main objective of the current study was to investigate the concentration dispersion of sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxides (NOx) and particulate matter with an aerodynamic diameter of less than 10 μm (PM10) emitted from a steel plant located in Muscat, Oman. This investigation was supported by the use of CALPUFF dispersion modeling software. The study analysis was based on selected modeling days that represent two different periods of the year: winter and summer. CALPUFF case study simulation results showed that winter NOx concentration levels exceeded the allowable concentrations set by the United States Environmental Protection Agency (U.S. EPA) standards. On the other hand, SO2, CO, and PM10 simulated results were within the allowable concentration limits.

Prediction of air pollutants concentrations from multiple sources using AERMOD coupled with WRF prognostic model

The investigation of pollutants concentrations affected by the multiple sources is essential for air quality management. In this study, the spatial variations of SO2, NO2 and PM10 emitted from multiple industrial sources in Pasir Gudang industrial area, Johor, Malaysia were predicted using American Meteorological Society/Environmental Protection Regulatory Model (AERMOD) air dispersion model coupled with Weather Research and Forecasting (WRF). The WRF model was applied to simulate the hourly surface and upper air meteorological variables for the period of two weeks. The output parameters from WRF such as temperature, wind speed and wind direction were also statistically evaluated in the study. The results of comparing the wind roses from the observed and simulated data in Pasir Gudang station showed the difficulty of prognostic WRF model in predicting wind direction in Malaysia located in a coastal site. The results showed that the maximum ground level concentration of SO2, NO2 and PM10 simulated through AERMOD-WRF in the industrial area was 36.2, 59.8 and 5.4 μg/m3, respectively. The evaluation of AERMOD through the Quantile-Quantile (Q-Q) plots showed that most of the predicted and observed pair points are lying close to the one-to-one line indicating that there is a good agreement between predicted and observed concentrations in the study. The findings of this study can facilitate and assist the local government authorities and policy makers in managing the urban air quality.

OMI satellite observations of decadal changes in ground-level sulfur dioxide over North America

Abstract. Sulfur dioxide (SO2) has a significant impact on the environment and human health. We estimated ground-level sulfur dioxide (SO2) concentrations from the Ozone Monitoring Instrument (OMI) using SO2 profiles from the Global Environmental Multi-scale – Modelling Air quality and CHemistry (GEM-MACH) model over North America for the period of 2005–2015. OMI-derived ground-level SO2 concentrations (r = 0. 61) and trends (r = 0. 74) correlated well with coincident in situ measurements from air quality networks over North America. We found a strong decreasing trend in coincidently sampled ground-level SO2 from OMI (−81 ± 19 %) and in situ measurements (−86 ± 13 %) over the eastern US for the period of 2005–2015, which reflects the implementation of stricter pollution control laws, including flue-gas desulfurization (FGD) devices in power plants. The spatially and temporally contiguous OMI-derived ground-level SO2 concentrations can be used to assess the impact of long-term exposure to SO2 on the health of humans and the environment.

Responses of Trichilia dregeana leaves to sulphur dioxide pollution: A comparison of morphological, physiological and biochemical biomarkers

Industrial zones in eThekwini, South Africa, such as the South Durban Basin (SDB) are often characterised by extremely poor air quality owing to industrial emissions. This study investigated the effects of SO2 pollution on selected stress biomarkers in the leaves of Trichilia dregeana to assess the utility of this species as a bioindicator of this pollutant. Leaves were sampled from trees growing at three industrial (treatment) sites (Prospecton, Ganges and Southern Works) within the SDB and from greenhouse-located trees (ex situ control). Sampling accommodated for directional and seasonal wind effects and yielded a sample size of n = 24 for all four seasons. Ground-level SO2 concentrations ([SO2]) measured at each site were positively correlated with leaf sulphate contents and both [SO2] and leaf sulphate levels of the control were lower than the treatment sites. Values for the various biomarkers did not differ significantly for leaves from different cardinal points within sites, but seasonal variations were evident. Except for leaf chlorophyll fluorescence, all biomarkers could discriminate between treatment and control leaves. Though seasonal data for a number of these biomarkers were significantly correlated with leaf sulphate content, none of the biomarkers were sensitive enough to reflect differences in leaf sulphate levels across the treatment sites. Furthermore, the results suggest that leaf area and relative chlorophyll content should be measured in combination with each other. Leaf sulphate content is a reliable proxy for SO2 pollution. All biomarkers, except for chlorophyll fluorescence, can be used to establish T. dregeana leaves as a bioindicator of SO2 pollution.

Examining the utility of hyperspectral remote sensing and partial least squares to predict plant stress responses to sulphur dioxide pollution: a case study of Trichilia dregeana Sond.

The use of air quality monitoring stations is expensive, with pollution data being either unavailable or inaccessible. Hence, effects of atmospheric sulphur dioxide (SO2) levels on biomarkers related to environmental stress were investigated for Trichilia dregeana tree leaves, in order to assess their bioindicator potential. Leaves were sampled randomly from trees at three industrial sites within the South Durban Basin, and an ex situ control, across two seasons (n = 28, per season). Ground-level SO2 concentrations were measured daily and ranged between 1 and 25 ppb. There were significant (p < 0.001) differences across sites and seasons for leaf area and leaf chlorophyll content. Partial least squares regression (PLSR) was used to quantify the relationship between biomarkers and hyperspectral data. For leaf chlorophyll content and leaf area, r2 values ranged from 0.325–0.475 to 0.429–0.586, with root mean square error of prediction (RMSEP) ranging between 8.75–8.98 and 9.20–12.52. The variable importance in projection (VIP) method was utilized and significant hyperspectral wavebands were identified, within the red-edge region, at 552 and 704 nm for spring, and at 552 and 708 nm for summer. Notably, PLSR was able to relate hyperspectral data-sets to both biomarkers, showing promise in identifying stress in T. dregeana leaves. However, the interaction between leaf chlorophyll content and leaf area suggests that a simultaneous prediction of these biomarkers may be more suitable.

Current challenges in modelling far-range air pollution induced by the 2014–2015 Bárðarbunga fissure eruption (Iceland)

Abstract. The 2014–2015 Holuhraun lava-flood eruption of Bárðarbunga volcano (Iceland) emitted prodigious amounts of sulfur dioxide into the atmosphere. This eruption caused a large-scale episode of air pollution throughout Western Europe in September 2014, the first event of this magnitude recorded in the modern era. We gathered chemistry-transport simulations and a wealth of complementary observations from satellite sensors (OMI, IASI), ground-based remote sensing (lidar, sunphotometry, differential optical absorption spectroscopy) and ground-level air quality monitoring networks to characterize both the spatial-temporal distributions of volcanic SO2 and sulfate aerosols as well as the dynamics of the planetary boundary layer. Time variations of dynamical and microphysical properties of sulfate aerosols in the aged low-tropospheric volcanic cloud, including loading, vertical distribution, size distribution and single scattering albedo, are provided. Retrospective chemistry-transport simulations at low horizontal resolution (25 km × 25 km) capture the correct temporal dynamics of this far-range air pollution event but fail to reproduce the correct magnitude of SO2 concentration at ground-level. Simulations at higher spatial resolution, relying on two nested domains with finest resolution of 7.3 km × 7.3 km, improve substantially the far-range vertical distribution of the volcanic cloud and subsequently the description of ground-level SO2 concentrations. However, remaining discrepancies between model and observations are shown to result from an inaccurate representation of the planetary boundary layer (PBL) dynamics. Comparison with lidar observations points out a systematic under-estimation of the PBL height by the model, whichever the PBL parameterization scheme. Such a shortcoming impedes the capture of the overlying Bárðarbunga cloud into the PBL at the right time and in sufficient quantities. This study therefore demonstrates the key role played by the PBL dynamics in accurately modelling large-scale volcanogenic air pollution.

Next article &gt;&gt; &lt;&lt; Previous article Environmental pressure from the 2014–15 eruption of Bárðarbunga volcano, Iceland

The effusive six months long 2014-2015 Barðarbunga eruption (31 August-27 February) was the largest in Iceland for more than 200 years, producing 1.6 ± 0.3 km3 of lava. The total SO2 emission was 11 ± 5 Mt, more than the amount emitted from Europe in 2011. The ground level concentration of SO2 exceeded the 350 μg m−3 hourly average health limit over much of Iceland for days to weeks. Anomalously high SO2 concentrations were also measured at several locations in Europe in September. The lowest pH of fresh snowmelt at the eruption site was 3.3, and 3.2 in precipitation 105 km away from the source. Elevated dissolved H2SO4, HCl, HF, and metal concentrations were measured in snow and precipitation. Environmental pressures from the eruption and impacts on populated areas were reduced by its remoteness, timing, and the weather. The anticipated primary environmental pressure is on the surface waters, soils, and vegetation of Iceland.

Minimization of SO2 Emissions at ADGAS (Das Island, UAE): I- Current vs. Modified Schemes

The objective of this work is to explore feasible technologies to minimize SO2 emissions from ADGAS and investigate the impact of implementing such modifications on the ambient air quality at the Island. In order to achieve this, two SO2 emission minimization schemes have been proposed; a Fuel Gas Sweetening (FGS) scheme and a Flue Gas Desulfurization (FGD) scheme.The FGS scheme involves (1) directing most of the H2S in the fuel gas to the Sulfur Recovery Units (SRUs) where it is converted to elemental sulfur. The unconverted H2S will be routed to the SRUs’ incinerators where it is oxidized to SO2, and (2) revamping the UGAs internals (by replacing current packing with an approved higher efficiency packing) in order to produce a sweeter fuel gas. The FGD scheme involves installation of SW-FGD units downstream the SRUs’ incinerators where the SO2 in the flue gas is scrubbed by the plant spent seawater in a dedicated packed bed absorber and converting it to harmless sulfate ions (natural constituents of the seawater) that will be safely disposed to the sea. The FGS scheme is expected to reduce the H2S content in the fuel gas by 94% and result in decreasing the total SO2 emissions due to fuel gas usage by 98%. The FGD scheme is expected to reduce the SO2 emissions due to incomplete sulfur recovery in the SRUs by 99.5%. Implementation of both schemes is expected to reduce the total SO2 emissions by 77%. Most of the remaining SO2 emissions (23%) are due to the continuous flaring of the flash gas in the plant. In Part II of this work, the BREEZE AERMOD Pro Software is used to predict the SO2 Ground Level Concentration (GLC) for the current and modified SO2 minimization schemes. Compliance with the country limits and challenge with future regulatory standards have been examined.

Chapter 23 Sulphur dioxide diffusion tube monitoring: Soufrière Hills Volcano, Montserrat, 1995 to 2011

Abstract Sulphur dioxide (SO 2 ) diffusion tube monitoring has been undertaken on Montserrat since 1995, providing a unique and insightful long-term dataset of ground-level SO 2 concentrations during the eruption of the Soufrière Hills Volcano (SHV). The monitoring of ground-level SO 2 is important to assess the potential of human exposure to high levels of SO 2 that may impact on health. Air-quality objectives for SO 2 are present in some countries to prevent potential health impacts. Here we summarise diffusion tube monitoring in Montserrat and analyse concentrations with respect to the potential for exposure to levels above recommended levels. We explore relationships that may exist with SO 2 flux measurements and volcanic events. Concentrations have been higher during pauses in lava extrusion. Diffusion tube concentrations are highest within 5 km of the volcano and at locations downwind of the plume. Areas where concentrations have exceeded relevant limits have been uninhabited since 1996. The potential for human exposure above recommended limits is, therefore, currently considered low, as the population would not have been exposed to high concentrations for extended periods of time. Full-time occupation and/or long-term exposure in the areas where concentrations exceed the relevant limits would not be advised.