Atmospheric Release Research Articles

Watford Anaesthetics going greener: reducing our emissions one volatile at a time

Background: Anaesthetic gases are responsible for 3% of the NHS carbon footprint. The NHS Long Term Plan aims to reduce this by 40% by: shifting away from desflurane use; effective capture, destruction, or reuse of volatiles and reduction in atmospheric release from leftover nitrous oxide gas canisters.1 A 240 ml bottle of desflurane costs £63, producing 886 kg of carbon dioxide emissions (CO2e) compared with a 250 ml bottle of sevoflurane which costs £44.99 producing 49 kg.2 We aim to reduce our carbon footprint by reducing desflurane use, encouraging low flow anaesthesia and use of TIVA. Methods: A departmental questionnaire was sent to assess knowledge of the environmental impact anaesthetic gases cause and gauge desflurane use. The pharmacy provided procurement data for sevoflurane, desflurane, and 2% propofol for 2019. Our intervention was to remove desflurane from all anaesthetic machines after consultation. TIVA training for trainees was provided and 6-month pharmacy procurement data obtained. Results: The majority (89%) use low flow anaesthesia with volatiles and interest in TIVA use is increasing. The inaccessibility of desflurane has led to a 100% decrease in use this 6-month period. Over a year, this could lead to savings of £26 124.68 and 455 240 kg CO2e (Table 5).Table 5Comparison of cost and CO2e usage before and after removal of desflurane.AnaestheticBottles usedTotal cost (£)Total CO2e (kg)2019August 21–January 222019Projected 20222019Projected 2022Sevoflurane40227518 085.9824 744.5019 69826 950Desflurane522032 8660462 4920Propofol 2%119061821422224.8000Total53 093.9826 969.30482 19026 950 Open table in a new tab Conclusions: No negative impact from desflurane removal has been reported. Equipment for TIVA use including bispectral index (BIS) monitoring is now widely available in our department. Next steps include re-auditing and comparing pharmacy procurement data from 2019 to 2022. We are looking to expand our ‘greener’ movement into re-capturing N2O and improving recycling methods. 1.England.nhs.uk. 2021. Delivering a ‘net zero’ national health service. Available at: https://www.england.nhs.uk/greenernhs/wp-content/uploads/sites/51/2020/10/delivering-a-net-zero-national-health-service.pdf (accessed 25 March 2022)2.Pierce J. The environment, the gas bill and the route to sustainable anaesthesia. Rcoa.ac.uk. 2013. Available at: https://www.rcoa.ac.uk/sites/default/files/documents/2019-09/Bulletin82-Nov2013-Pages39-41.pdf (accessed 25 March 2022).

Radiation exposure for the population living around the coal-fired power plant complexes in Vietnam.

A coal-fired power plant's operation can release radioactive nuclides and radon gas into the environment, affecting the surrounding ecosystem. In this work, the collective effective dose due to the inhalation and the consumption of food containing the deposited radionuclides from the atmospheric release of the plants were evaluated. The results show that the radioactivity concentration in coal and fly ash samples depends on the originof feed coal. The distribution of Th and U radionuclides in the 6a1 dust coal and bituminous coal is different. In general, the collective effective dose for different organs due to radiation exposure from the atmospheric release of two surveyed CFPP complexes are lower than the corresponding value published by UNSCEAR.

Spatiotemporal distribution of the atmospheric 14C around Ningde NPP

In this paper, the sampling and monitoring methods of atmospheric 14C around Ningde NPP were presented, and the variations and trends during 2013–2021 were statistically analyzed and comparatively studied with worldwide reported values around NPPs. Meanwhile, the correlation study with the gaseous effluent emission amount from Ningde NPP was analyzed, and the spatial distribution of the atmospheric 14C around Ningde NPP was simulated with the atmospheric release based on the long-term meteorological parameters with the plume diffusion model. It was shown that the average specific activity of atmospheric 14C at each sampling site ranged from 229 to 230 mBq/gC, and the weak evidence of influence on the nearest sampling site from the release of the NPP could be observed. Seasonal variations of 14C specific activity were analyzed, and it was shown that, except for the site 1.7 km from the NPP, the specific activity of the atmospheric 14C was higher in summer and autumn and lower in winter and spring. Besides, it was shown that the excess 14C for long-term monitoring results around the NPP was consistent with the simulated values on the order of magnitude.

Radiocarbon generation and atmospheric release assessment from nuclear power plant with RBMK type reactors

The article provides the results of the estimation of 14C nuclide generation and release from the systems and structures of RBMK-1500 reactors operated at Ignalina NPP. The main circulation circuit and gaseous circuit of this type of reactor are the primary sources of 14C generation and airborne release, evaluated to be 0.491 and 0.367 TBq per one calendar year (10.5 months of effective reactor operation at 1350 MWe power), respectively. The analysis of the operation specifics of these systems showed that they don’t provide an effective barrier to contain 14C due to the 14CO2 chemical form of radiocarbon in RBMK reactors, i.e., 100% release (0.858 TBq/year) have been evaluated available for atmospheric release. These results have been compared with the atmospheric releases evaluated from the 14C activity concentration measured in Scots pine tree (Pinus Sylvestris L.) ring samples by single stage accelerator mass spectrometer (SSAMS, NEC, USA) at Vilnius Radiocarbon facility, resulting to airborne release value of 1 TBq/year for one RBMK-1500 reactor. Slightly higher value reproduced from the tree ring samples indicates that the reactor graphite stack might be also a source of 14C releases of about 0.14–0.24 TBq/year. Based on similar design features the results of the study can be easily projected to the RBMK-1000 reactors rescaling 14C source term according to the lower reactor power.

Ingestion of Diazotrophs Makes Corals More Resistant to Heat Stress.

Over the past decade, coral bleaching events have continued to recur and intensify. During bleaching, corals expel millions of their symbionts, depriving the host from its main food source. One mechanism used by corals to resist bleaching consists in exploiting food sources other than autotrophy. Among the food sources available in the reefs, dinitrogen (N2)-fixing prokaryotes or planktonic diazotrophs (hereafter called ‘PD’) have the particularity to reduce atmospheric dinitrogen (N2) and release part of this nitrogen (diazotroph-derived nitrogen or DDN) in bioavailable form. Here, we submitted coral colonies of Stylophora pistillata, fed or not with planktonic diazotrophs, to a temperature stress of up to 31 ± 0.5 °C and measured their physiological responses (photosynthetic efficiency, symbiont density, and growth rates). Heat-unfed colonies died 8 days after the heat stress while heat-PD-fed corals remained alive after 10 days of heat stress. The supply of PD allowed corals to maintain minimal chlorophyll concentration and symbiont density, sustaining photosynthetic efficiency and stimulating coral growth of up to 48% compared to unfed ones. By providing an alternative source of bioavailable nitrogen and carbon, this specific planktonic diazotroph feeding may have a profound potential for coral bleaching recovery.

Studies on the contribution of the aquatic water body to the tritium flux in the atmosphere near the discharge point of Kakrapar Gujarat Site, India

The contribution of the aquatic water body to the tritium (3H) flux in the atmosphere near the discharge point of Kakrapar Gujarat Site has been assessed by collecting and analyzing the 3H activity in the air moisture and in the water sample near the aquatic discharge point. The observed air 3H activity near the discharge point was in the range of ≤0.20–19.8 Bq/m3, whereas the predicted 3H activity at the same location due to the atmospheric release through stack varied from 0.10 to 0.15 Bq/m3. The range of water 3H activity through the discharge point varied from ≤10 to 3482 Bq/l. The 3H flux (water to air transfer) was estimated and found to be in the range of ≤5.90E+01 – 2.05E+04 Bq/m2/s. The observation shows that during radioactive aquatic releases, there is an increase in the 3H activity levels in the water vapor near the aquatic discharge point. The observed 3H activity levels in air samples were extremely low to contribute any additional dose to the member of the public as compared to the public dose obtained from natural background sources.

Bounding uncertainties around the conceptual representation of species in radiological assessment in the context of routine atmospheric release

Wildlife protection has become of regulatory interest since the International Commission on Radiological Protection (ICRP) developed an approach to assess the level of radiological protection specifically for animals and plants. For the purpose of demonstrating compliance with regulation to protect the environment against routine authorised discharges from nuclear facilities, the wide variety of biota inhabiting an ecosystem needs to be condensed to a limited set of representative organisms, as proposed by the ICRP with a set of ‘reference animals and plants’ which can be considered representative of many other species. It is now recommended in the International Atomic Energy Agency Safety Standards, and internationally accepted, that the use of such a limited number of organisms to represent a pool of species is adequate for radiation protection purposes, particularly in planned exposure situations. Adding site-specific species to that set of surrogate species can respond to various interests, such as ensuring a site-specific context to the assessment that addresses stakeholder interests and can aid in stakeholder consultation and risk communication. Moreover, there is a need to question whether the use of the set of surrogate organisms is conservative enough to cover a wider range of biodiversity. Previous studies partially answered this question and this paper adds a range of test cases. A selection of hypothetical representations of possible site-specific species are assessed on the basis of possible variations in size (mass) and occupancy habits. Dose rates are evaluated to determine the greatest difference between hypothetical organisms and those for reference organisms (ROs), considering radionuclides (RNs) potentially discharged in atmospheric routine release from different nuclear facilities. Differences observed in the results between hypothetical organisms and ROs were less than one order of magnitude in all cases, the difference being dependent on the RNs considered. These findings do not preclude the inclusion of site-specific species in environmental radiological assessments if it is considered necessary, but they provide reassurance that using ROs for radiological impact assessments in the case of routine atmospheric discharges is sufficient.

Radiological consequence assessment for hypothetical nuclear explosion scenario using HotSpot

In this study the influence of atmospheric conditions, release height and particle size are studied on the radiological impact due to a hypothetical 15 KT nuclear explosion using the HotSpot model. Simulations show that among different parameters, the height of burst produces the highest impact on the total effective dose (TED). It is found that the maximum TED is about 4 orders higher for surface burst compared to elevated explosions. The range of impact of acute doses (TED >0.25 Sv) extends up to 10 km for neutral to stable conditions for ground releases and 5 km for unstable conditions for 600 m release. It has been found that city type terrain reduces the doses by 40% and 80% in unstable and stable conditions respectively compared to flat terrain. Simulations with different particle sizes indicate that the ground shine and TED are about twice higher for 100% RF particles compared to 50% RF particles after 0.5 km for all atmospheric conditions. The range of impact extends from 6 km for unstable to 10 km for stable conditions for both particle sizes. Larger particles lead to roughly 8 times higher ground deposited activity within 0.5 km for A to D conditions. For elevated release dose is highly sensitive to particle size parameter, almost 40 times higher compared to ground release and the range of impact extends to 10 km for 50% RF against 6 km for 100% RF. Simulations with inversion conditions suggest that an elevated inversion leads to enhanced TED especially for unstable condition (A, B, C classes) roughly by 2 factors at 1 km to 1 order at 10 km relative to no inversion and sensitivity of capping layer is lower for elevated releases. It has been found that presence of rain (10 mm.h−1) leads to higher groundshine dose by ∼1 order compared to no rain scenario. The sensitivity of washout is relatively high for elevated releases in the first 4 km range where the groundshine is at least 2 to 3 orders more compared to no rain condition and range of acute dose extends up to 8 km from 6 km in raining condition.

Timothy Grass Pollen Induces Spatial Reorganisation of F-Actin and Loss of Junctional Integrity in Respiratory Cells.

Grass pollens have been identified as mediators of respiratory distress, capable of exacerbating respiratory diseases including epidemic thunderstorm asthma (ETSA). It is hypothesised that during thunderstorms, grass pollen grains swell to absorb atmospheric water, rupture, and release internal protein content to the atmosphere. The inhalation of atmospheric grass pollen proteins results in deadly ETSA events. We sought to identify the underlying cellular mechanisms that may contribute towards the severity of ETSA in temperate climates using Timothy grass (Phleum pratense). Respiratory cells exposed to Timothy grass pollen protein extract (PPE) caused cells to undergo hypoxia ultimately triggering the subcellular re-organisation of F-actin from the peri junctional belt to cytoplasmic fibre assembly traversing the cell body. This change in actin configuration coincided with the spatial reorganisation of microtubules and importantly, decreased cell compressibility specifically at the cell centre. Further to this, we find that the pollen-induced reorganisation of the actin cytoskeleton prompting secretion of the pro-inflammatory cytokine, interleukin-8. In addition, the loss of peri-junctional actin following exposure to pollen proteins was accompanied by the release of epithelial transmembrane protein, E-cadherin from cell-cell junctions resulting in a decrease in epithelial barrier integrity. We demonstrate that Timothy grass pollen regulates F-actin dynamics and E-cadherin localisation in respiratory cells to mediate cell-cell junctional integrity highlighting a possible molecular pathway underpinning ETSA events.

Mercury pollution in China: implications on the implementation of the Minamata Convention.

Mercury (Hg) is a toxic metal released into the environment through human activities and natural processes. Human activities have profoundly increased the amount of Hg in the atmosphere and altered its global cycling since the Industrial Revolution. Gaseous elemental Hg is the predominant form of Hg in the atmosphere, which can undergo long-range transport and atmospheric deposition into the aquatic systems. Hg deposition elevates the methylmercury (MeHg) level in fish through bioaccumulation and biomagnification, which poses a serious human health risk. Acute poisoning of MeHg can result in Minamata disease, while low-level long-term exposure in pregnant women can reduce the intelligence quotient of infants. After five sessions of intergovernmental negotiation, the Minamata Convention on mercury entered into force in August 2017 to protect human health and the environment from Hg pollution. Currently China contributes the largest quantity of Hg production, consumption, and emission globally. However, the status of Hg pollution in the environment in China and its associated health risk remains relatively unknown, which hinders the development of implementation plans of the Minamata Convention. In this paper, we provide a comprehensive review on the atmospheric release of Hg, distribution of air Hg concentration, human exposure to MeHg and health impacts caused by Hg pollution in China. Ongoing improvement of air pollution control measures is expected to further decrease anthropogenic Hg emissions in China. Air Hg concentrations in China are higher than the background values in the Northern Hemisphere, with spatial distribution largely influenced by anthropogenic emissions. Long-term observations of GEM in China show a decline in recent years. The net Hg transport outflow from China in 2013 is estimated to be 511 t year-1, and ∼60% of such outflow is caused by natural surface Hg emissions. Hg concentrations in fish and rice in China are relatively low and therefore the associated risks of human Hg exposure are low. Future research needs and recommendations for the implementation of the Minamata Convention are also discussed in this paper.

Rapid Contrastive Experimental Study on the Adiabatic Spontaneous Combustion Period of Loose Lignite.

The adiabatic spontaneous combustion period of coal is an important index for the macroscopic characterization of coal spontaneous combustion, and it is affected by many internal and external factors. There are several methods to study it, but there are various shortcomings to these methods. Some require too much time, while others have too many interfering factors. To quickly obtain the accurate adiabatic spontaneous combustion period of coal, a rapid contrastive experimental method was designed. In this method, the coal samples of the experimental and control groups were the same, and air and nitrogen were used as control atmospheres. A theoretical calculation method for the adiabatic spontaneous combustion period based on this method is proposed. The experimental results showed that during the temperature-programmed coal spontaneous combustion experiment, the increase in the coal temperature was due to physical and chemical heating. Physical heating is the heating effect of the temperature-programmed furnace body and the heated gas on the coal sample. Chemical heating includes oxidative exothermic heating promoted by physical and adiabatic oxidation heating. The adiabatic oxidative heat release can be determined by the oxidation heat release in the air atmosphere minus the oxidation heat release corresponding to the coal sample temperature in the nitrogen environment at the same period. The adiabatic spontaneous combustion period of coal can be calculated from the adiabatic oxidation heat release. Our results provide a rapid contrastive experimental method to quickly obtain the accurate adiabatic spontaneous combustion period of coal.

Experimental measurements of the bacterial oxidation of HT in soils: Impact over a zone influenced by an industrial release of tritium in HT form

Tritium is a radionuclide released to the atmosphere by nuclear industries in various forms, mainly HTO and to a lesser extent HT. However, some nuclear sites may emit predominantly HT in the atmosphere. The HT is oxidized to HTO essentially in the top cm of soils, and that the formed HTO is then possibly released into the atmosphere. HTO is an assimilable form by plants. Therefore, it is important to understand the environmental behaviour of HT.In this work, we adapt the bacterial oxidation model of HT in soils of Ota et al. (2007) by laboratory experiments on soils typical of western France, and we have in particular adapted the frequency factor A and the Michaelis-Menten enzymatic reaction parameter (Km) on the basis of an Arrhenius equation in function of the porosity of the soil.We then applied this model to the environment near the reprocessing plant of Orano la Hague (France), which emits a significant amount of HT. Based on the adapted model, and knowing the atmospheric variations of HTO and HT over the period 2013–2016, we estimated that the mean HTO activity in soil due to atmospheric HT reached 0.6 Bq.L−1 (with a peak value of 5 Bq.L−1) while the mean value with all sources taken into account is 6.2 Bq.L−1. Then, in an environment such as that surrounding the Orano La Hague plant, where near-field atmospheric HT activity is very high, the bacterial oxydation contribution to produce HTO in the soil can be considered as approximately 10%. The flux to the atmosphere from these source representing approximately. 1.5 Bq.m−2.d−1. If we consider an area of 2 km around the plant (i.e. 13 km2), we estimate 218 Bq.s−1 of HTO was released by the soil, representing less than 0.1% of the direct atmospheric release of HTO around the site. From this work, it appears clear that this secondary source term from the soil is insignificant at this specific site.

Source term determination with elastic plume bias correction

Estimation of a source term, i.e. release rate, of atmospheric radionuclide emissions is of key interest for nuclear emergency response and further accident analysis. The source term estimate is, however, often very inaccurate due to biases in atmospheric transport and used meteorological analysis. We propose a method for atmospheric plume bias correction which uses not only concentrations modeled at a measuring site but also the information on concentration gradient from the neighborhood of each measuring site, i.e. information already available from the atmospheric transport model. To properly regularize the model, we propose an elastic model of the plume bias correction based on regularization with the use of known topology of the measurement network. The proposed plume bias correction method can be coupled with an arbitrary source term estimation algorithm and can be instantly applied to any other atmospheric release of hazardous material. We demonstrate the method in two real cases. First, we use data from the European Tracer Experiment to validate the methodology. Second, we use data from the 106Ru occurrence over Europe in 2017 to demonstrate the methodology in a more demanding case where agreement with state-of-the-art estimates is shown with much better reconstruction of measurements.

Development and Performance of Underwater Gamma-Ray Spectrometry for Riverbed Monitoring

Ji, Y.-Y.; Joung, S.; Min, B.I., and Suh, K.-S., 2021. Development and performance of underwater gamma-ray spectrometry for riverbed monitoring. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 330–334. Coconut Creek (Florida), ISSN 0749-0208. The atmospheric release and fallouts of radionuclides have produced the radioactive contamination over wide area in the accident at the Fukushima Daiichi nuclear power plant (FDNPP). They still affect the environment around the Fukushima Prefecture, such as resident area, fields, mountainous area, river and stream, and reservoir. In JAEA (Japan Atomic Energy Agency), diverse monitoring platforms have been developing and successfully applying to the assessment of environmental radiation and deposited nuclides. Especially, there are about 3,700 irrigation reservoirs around the Fukushima Prefecture, which can be effected from direct fallouts in reservoirs as well as dispersions of the contamination in the other sites, depending on weather conditions. Underwater survey system is an important tool to assess the radioactive contamination in the river, stream and reservoir, including the bottom sediments. In this study, underwater gamma-ray spectrometry, named as MARK-U1, was developed to rapidly estimate the underwater radioactivity for the emergency preparedness, according to the lesson learned from the nuclear accident of FDNPP. A 3”φx3” NaI(Tl) detector is equipped in this underwater system and the lateral shielding around a detector was also designed using lead with a thickness of 1 cm to confine the field of view. Finally, its performance test was conducted by evaluating the natural radioactivity of 214Bi, 208Tl, and 40K in the riverbed of reservoir.

Backward Estimation of Atmospheric Release of 137Cs and 131I Using Total Cumulative Deposition in Terrestrial Areas Following the Fukushima Daiichi Nuclear Power Plant Accident.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident caused a significant release of radionuclides into the environment. It is important to explore the timing and amount of radioactive release to terrestrial areas in order to clarify the consequences of the accident, including the dose received by the population living in the areas affected by the accident. In general, backward estimations are performed using air concentrations of radionuclides, but they are difficult to measure when radioactive plumes are passing through, and only spatially and temporally limited measurements are available. Therefore, a new method of backward estimation was developed based on the total cumulative deposition density, which can provide sufficient data in the environment by combining the atmospheric transport, dispersion, and deposition model calculations. Consequently, our estimations show that a major release of 137Cs and 131I occurred on 15, 20, 21, 22, 25, and 30 March 2011, after the accident. The amounts of release estimated by our new method for 137Cs and 131I were 4.9 × 1015 Bq and 120 × 1015 Bq, respectively. These results have no significant contradiction with the estimated results by the previous studies that were based on air concentrations and air dose rates that were measured in terrestrial areas. It was found that our new method is applicable for backward estimation oriented to the dose assessment for the people living in terrestrial areas.

Modeling Riverine N2O Sources, Fates, and Emission Factors in a Typical River Network of Eastern China.

Estimates of riverine N2O emission contain great uncertainty because of the lack of quantitative knowledge concerning riverine N2O sources and fates. Using a 3.5-year record of monthly N2O measurements from the Yongan River network of eastern China, we developed a mass-balance model to address the riverine N2O source and sink processes. We achieved reasonable model efficacies (R2 = 0.44-0.84, Nash-Sutcliffe coefficients = 0.40-0.80) across three tributaries and the entire river system. Estimated riverine N2O loads originated from groundwater (38-88%), surface runoff (3-26%), and in-stream production (4-48%). Estimated in-stream losses via atmospheric release + complete denitrification accounted for 76, 95, 25, and 89% of riverine N2O fate for the agricultural, residential, forest, and entire river system, respectively. Considering limited complete denitrification, the model estimated an upper-bound riverine N2O emission rate of 2.65 ton N2O-N km-2 year-1 for the entire river system. Riverine N2O emission estimates were of comparable magnitude to those estimated with a power-law scaling model. Riverine N2O emissions using the IPCC default emission factor (0.26%) overestimated emissions by 3-15 times, whereas the dissolved N2O concentration-based emission factor overestimated or underestimated emissions. This study highlights the importance of combining comprehensive information on N2O sources and fates to achieve accurate riverine N2O emission estimates.

Quantification of uncertainties in the assessment of an atmospheric release source applied to the autumn 2017 <sup>106</sup>Ru event

Abstract. Using a Bayesian framework in the inverse problem of estimating the source of an atmospheric release of a pollutant has proven fruitful in recent years. Through Markov chain Monte Carlo (MCMC) algorithms, the statistical distribution of the release parameters such as the location, the duration, and the magnitude as well as error covariances can be sampled so as to get a complete characterisation of the source. In this study, several approaches are described and applied to better quantify these distributions, and therefore to get a better representation of the uncertainties. First, we propose a method based on ensemble forecasting: physical parameters of both the meteorological fields and the transport model are perturbed to create an enhanced ensemble. In order to account for physical model errors, the importance of ensemble members are represented by weights and sampled together with the other variables of the source. Second, once the choice of the statistical likelihood is shown to alter the nuclear source assessment, we suggest several suitable distributions for the errors. Finally, we propose two specific designs of the covariance matrix associated with the observation error. These methods are applied to the source term reconstruction of the 106Ru of unknown origin in Europe in autumn 2017. A posteriori distributions meant to identify the origin of the release, to assess the source term, and to quantify the uncertainties associated with the observations and the model, as well as densities of the weights of the perturbed ensemble, are presented.

Thermodynamic research on the effect of H2O on transformation of organic sulphur during coal pyrolysis under CO2 atmosphere

This study investigates the effect of H2O on transformation of organic sulphur in coal during CO2 atmospheres by thermodynamic equilibrium calculation by HSC Chemistry. The effect of water vapour on the release of sulphur containing compounds was studied. Detailed S distribution between 200-1400°C was explored. The results show that CO2 not only promotes the formation of inorganic compounds, but also moves the peak of released less complicated organic compounds such as Thiophene, Methylthiophene, Dimethylthiophene, etc. to a much lower temperature. The ranking of the sulphur release in CO2 atmosphere by HSC is: SO2 > Methyl thiophene > Dimethyl thiophene > Ethyl thiophene > dimethyl sulfone. Temperature affects the transformation of sulphur greatly during pyrolysis in CO2 atmosphere. Below 700 °C, COS and H2S are two major sulphur containing compounds formed during pyrolysis in CO2. Above 700 °C, SO2 plays the main role. H2O at different temperature range during heating also reacts with organic sulphur compounds, leading to a further decomposition. Since more organic S stays in inert gas, water promotes the decomposition of organic S compounds more intense than that in CO2 atmosphere. Besides, the effect of water vapour on S distribution depends on the amount of H2O in the reaction.

Data-driven method for the improving forecasts of local weather dynamics

This paper describes the modeling approach for lower atmosphere dynamics in a selected location. The purpose of this model is to provide short-term and long-term forecasts of the weather variables which are used as the input data for the model of the dispersion of radioactive air pollution. The information from this integrated system is important for the implementation of the population safety measures in the case of a nuclear accident with an atmospheric release. We developed a dynamical, probabilistic, and non-parametric model based on Gaussian processes (GPs). GP nonlinear autoregressive model with exogenous inputs and variational training principle was implemented for multi-output training. A Monte Carlo approach to multi-output simulation of the model for long-term forecasts is presented which allows arbitrary prior distributions over function values. The model encompasses all available measurements from the weather stations near the location of interest and combines them with the forecasts from the numerical weather prediction model. The contribution of the developed model is the harvesting of all available information and simultaneously providing interconnected forecasts. The key result of this investigation is the improvement of short-term and long-term weather variable forecasts over those of the numerical weather prediction model. Consequently, we significantly enhance the dispersion forecast of radioactive air pollution for the case study considered. The computationally demanding modeling is accelerated using general-purpose computing on graphics processing units. The proposed method represents a step forward in the assurance of safety in the case of a nuclear accident.

Dual Control for Exploitation and Exploration (DCEE) in autonomous search

This paper proposes an optimal autonomous search framework, namely Dual Control for Exploration and Exploitation (DCEE), for a target at an unknown location in an unknown environment. Source localisation is to find sources of atmospheric hazardous material release in an unknown environment. This paper proposes a control theoretic approach to this autonomous search problem. To cope with an unknown target location, at each step, the target location is estimated by Bayesian inference. Then a control action is taken to minimise the error between future robot position and the predicted future estimation of the target location. The latter is generated by hypothesised measurements at the corresponding future robot positions (due to the control action) with the current estimation of the target location as a prior. It shows that DCEE can take into account both the error between the next robot position and the estimated target location, and the uncertainty of the estimate. This approach is further extended to deal with both an unknown source location and unknown local environment (e.g. wind speed and direction). Different from current information theoretic approaches, this new control theoretic approach achieves the optimal trade-off between exploitation and exploration in an unknown environment with an unknown target by driving the robot moving towards estimated target location while reducing its estimation uncertainty. Simulation and experimental studies demonstrate promising performance of the proposed approach. The relationships between the proposed approach, informative path planning, dual control, and classic model predictive control are discussed and compared. This work opens a door for developing control systems operating in unknown environments, or performing tasks with unknown parameters.