| 1. |
- Aiuppa, A., et al.
(författare)
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Gas measurements from the Costa Rica-Nicaragua volcanic segment suggest possible along-arc variations in volcanic gas chemistry
- 2014
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 407, s. 134-147
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Tidskriftsartikel (refereegranskat)abstract
- Obtaining accurate estimates of the CO2 output from arc volcanism requires a precise understanding of the potential along-arc variations in volcanic gas chemistry, and ultimately of the magmatic gas signature of each individual arc segment. In an attempt to more fully constrain the magmatic gas signature of the Central America Volcanic Arc (CAVA), we present here the results of a volcanic gas survey performed during March and April 2013 at five degassing volcanoes within the Costa Rica-Nicaragua volcanic segment (CNVS). Observations of the volcanic gas plume made with a multicomponent gas analyzer system (Multi-GAS) have allowed characterization of the CO2/SO2-ratio signature of the plumes at Pads (0.30 +/- 0.06, mean +/- SD), Rincon de la Vieja (27.0 +/- 15.3), and Turrialba (2.2 +/- 0.8) in Costa Rica, and at Telica (3.0 +/- 0.9) and San Cristobal (4.2 +/- 1.3) in Nicaragua (all ratios on molar basis). By scaling these plume compositions to simultaneously measured SO2 fluxes, we estimate that the CO2 outputs at CNVS volcanoes range from low (25.5 +/- 11.0 tons/day at Pods) to moderate (918 to 1270 tons/day at Turrialba). These results add a new information to the still fragmentary volcanic CO2 output data set, and allow estimating the total CO2 output from the CNVS at 2835 1364 tons/day. Our novel results, with previously available information about gas emissions in Central America, are suggestive of distinct volcanic gas CO2/S-T (= SO2 + H2S)-ratio signature for magmatic volatiles in Nicaragua (similar to 3) relative to Costa Rica (similar to 0.5-1.0). We also provide additional evidence for the earlier theory relating the CO2-richer signature of Nicaragua volcanism to increased contributions from slab-derived fluids, relative to more-MORB-like volcanism in Costa Rica. The sizeable along-arc variations in magmatic gas chemistry that the present study has suggested indicate that additional gas observations are urgently needed to more-precisely confine the volcanic CO2 from the CAVA, and from global arc volcanism.
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| 2. |
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| 3. |
- Arellano, Santiago, 1981, et al.
(författare)
-
Synoptic analysis of a decade of daily measurements of SO2 emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change
- 2021
-
Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3516 .- 1866-3508. ; 13:3, s. 1167-1188
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Datasets for each volcano are made available at https://novac.chalmers.se (last access: 1 October 2020) under the CC-BY 4 license or through the DOI (digital object identifier) links provided in Table 1.
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| 4. |
- Boikos, Christos, et al.
(författare)
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Validating CFD modelling of ship plume dispersion in an urban environment with pollutant concentration measurements
- 2024
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Ingår i: Atmospheric Environment. - 1873-2844 .- 1352-2310. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- Air pollution in urban areas constitutes a global environmental problem, with shipping being one major contributor to hazardous pollutants in harbour areas. This work concerns the application of a method using CFD modelling to study how ships affect the air quality of port areas at a microscale level. A steady RANS-CFD approach was applied to simulate the dispersion of shipping-emitted pollutants, and a spatial sensitivity analysis of the CFD modelling results was conducted. The port of Marseille was used as a case study, and the CFD predictions were compared with on-site observations from two monitoring stations for CO2, CO, NOx, SO2 and PM concentrations. Representative modelled and measured concentrations were considered at the location of the monitoring stations to facilitate one-by-one comparisons for all pollutants in three different test cases of departing vessels. The modelling predictions presented an 8.2% (95% CI: -9.3%, 25.7%) average deviation from the measurements. Validation metrics were included to conduct a statistical comparison between predicted and measured concentrations, with almost all metric values indicating acceptable agreement between the CFD model and measurements. From a technical perspective, this study demonstrates the reliability of the applied CFD modelling method in estimating shipping plume dispersion, while from a societal perspective, this model can serve as an advisory tool for port authorities and policy makers to reduce the impact of shipping emissions on urban air quality.
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| 5. |
- Conde Jacobo, Alexander Vladimir, 1979, et al.
(författare)
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A rapid deployment instrument network for temporarily monitoring volcanic SO2 emissions - a study case from Telica volcano
- 2014
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Ingår i: Geoscientific Instrumentation, Methods and Data Systems. - : Copernicus GmbH. - 2193-0856 .- 2193-0864. ; 3:2, s. 127-134
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic gas emissions play a crucial role in describing geophysical processes; hence measurements of magmatic gases such as SO2 can be used as tracers prior and during volcanic crises. Different measurement techniques based on optical spectroscopy have provided valuable information when assessing volcanic crises. This paper describes the design and implementation of a network of spectroscopic instruments based on Differential Optical Absorption Spectroscopy (DOAS) for remote sensing of volcanic SO2 emissions, which is robust, portable and can be deployed in relative short time. The setup allows the processing of raw data in situ even in remote areas with limited accessibility, and delivers pre-processed data to end-users in near real time even during periods of volcanic crisis, via a satellite link. In addition, the hardware can be used to conduct short term studies of volcanic plumes in remotes areas. The network was tested at Telica, an active volcano located in western Nicaragua, producing what is so far the largest data set of continuous SO2 flux measurements at this volcano.
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| 6. |
- Conde Jacobo, Alexander Vladimir, 1979
(författare)
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Application of DOAS for Studies of Evolving Volcanic Activity in Central America
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanic gas emissions play a critical role in understanding the physical processes that drive eruptive activity. Combining gas measurements with other geophysical parameters provides a more accurate description of the changes that occur beneath a volcano. Understanding and tracking the evolution of volcanic activity is crucial for populated areas that may be affected by a potential eruptive crisis.This thesis illustrates the application of ground-based optical remote sensing using Differential Optical Absorption Spectroscopy (DOAS) for measuring volcanic gas emissions. Some measurements have been made within a range of several days to a few weeks, while in some cases we made measurements for more than one year. The case studies include the following volcanoes: Turrialba (Costa Rica), Concepción (Nicaragua), Arenal (Costa Rica), and Télica (Nicaragua).At Turrialba volcano the measured SO2 flux emissions clearly indicated an imminent eruptive event. The volcano’s degassing evolution during different periods was extensively compared with the most relevant seismic signatures. At Concepción volcano our measurements were related to seismic and geodesic indicators during an active eruptive period and a quiescent period. Preliminary results of ongoing measurements at Télica and Arenal volcano are also reported.Different comparisons in different scenarios provide multi-parametric surveillance methods that may be adopted by local institutions in charge of dealing with volcanic risk assessment.
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| 7. |
- Conde Jacobo, Alexander Vladimir, 1979, et al.
(författare)
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Linking SO2 emission rates and seismicity by continuous wavelet transform: implications for volcanic surveillance at San Cristbal volcano, Nicaragua
- 2016
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Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3262 .- 1437-3254. ; 105:5, s. 1453-1465
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Tidskriftsartikel (refereegranskat)abstract
- San Cristbal volcano is the highest and one of the most active volcanoes in Nicaragua. Its persistently high activity during the past decade is characterized by strong degassing and almost annual VEI 1-2 explosions, which present a threat to the local communities. Following an eruption on 8 September 2012, the intervals between eruptions decreased significantly, which we interpret as the start of a new eruptive phase. We present here the results of semi-continuous SO2 flux measurements covering a period of 18 months, obtained by two scanning UV-DOAS instruments installed as a part of the network for observation of volcanic and atmospheric change project, and the results of real-time seismic amplitude measurements (RSAM) data. Our data comprise a series of small to moderately explosive events in December 2012, June 2013 and February 2014, which were accompanied by increased gas emissions and seismicity. In order to approach an early warning strategy, we present a statistical method for the joint analysis of gas flux and seismic data, by using continuous wavelet transform and cross-wavelet transform (XWT) methods. This analysis shows that the XWT coefficients of SO2 flux and RSAM are in good agreement with the occurrence of eruptive events and thus may be used to indicate magma ascent into the volcano edifice. Such multi-parameter surveillance efforts can be useful for the interpretation and surveillance of possible eruptive events and could thus be used by local institutions for the prediction of upcoming volcanic unrest.
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| 8. |
- Conde Jacobo, Alexander Vladimir, 1979, et al.
(författare)
-
Measurements of volcanic SO2 and CO2 fluxes by combined DOAS, Multi-GAS and FTIR observations: a case study from Turrialba and Telica volcanoes
- 2014
-
Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3262 .- 1437-3254. ; 103:8, s. 2335-2347
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Tidskriftsartikel (refereegranskat)abstract
- Over the past few decades, substantial progress has been made to overcome the technical difficulties of continuously measuring volcanic SO2 emissions. However, measurements of CO2 emissions still present many difficulties, partly due to the lack of instruments that can directly measure CO2 emissions and partly due to its strong atmospheric background. In order to overcome these difficulties, a commonly taken approach is to combine differential optical absorption spectroscopy (DOAS) by using NOVAC scan-DOAS instruments for continuous measurements of crateric SO2 emissions, and electrochemical/NDIR multi-component gas analyser system (multi-GAS) instruments for measuring CO2/SO2 ratios of excerpts of the volcanic plume. This study aims to quantify the representativeness of excerpts of CO2/SO2 ratios measured by Multi-GAS as a fraction of the whole plume composition, by comparison with simultaneously measured CO2/SO2 ratios using cross-crater Fourier transform infrared spectroscopy (FTIR). Two study cases are presented: Telica volcano (Nicaragua), with a homogenous plume, quiescent degassing from a deep source and ambient temperature, and Turrialba volcano (Costa Rica), which has a non-homogeneous plume from three main sources with different compositions and temperatures. Our comparison shows that in our "easier case" (Telica), FTIR and Multi-GAS CO2/SO2 ratios agree within a factor about 3 %. In our "complicated case" (Turrialba), Multi-GAS and FTIR yield CO2/SO2 ratios differing by approximately 13-25 % at most. These results suggest that a fair estimation of volcanic CO2 emissions can be provided by the combination of DOAS and Multi-GAS instruments for volcanoes with similar degassing conditions as Telica or Turrialba. Based on the results of this comparison, we report that by the time our measurements were made, Telica and Turrialba were emitting approximately 100 and 1,000 t day(-1) of CO2, respectively.
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| 9. |
- Conde Jacobo, Alexander Vladimir, 1979, et al.
(författare)
-
SO2 degassing from Turrialba Volcano linked to seismic signatures during the period 2008-2012
- 2014
-
Ingår i: International Journal of Earth Sciences. - : Springer Science and Business Media LLC. - 1437-3262 .- 1437-3254. ; 103:7, s. 1983-1998
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Tidskriftsartikel (refereegranskat)abstract
- wIn 1996, after 150 years of relative calm, Turrialba Volcano was reawakening. A visible plume and serious damage to surrounding vegetation due to acid rain are the most obvious signals. As part of the Network for Observation of Volcanic and Atmospheric Change project, four gas-monitoring stations were initially installed on the west flank of the volcano with the purpose of measuring sulphur dioxide emissions during this period of increased activity using the scanning-differential optical absorption spectroscopy technique. We present here the results of semicontinuous gas flux measurements over a period of 5 years (from 2008 to 2012), providing a novel data set that documents a relatively rapid increase in SO2 fluxes from around 350 t day(-1) to around 4,000 t day(-1) leading up to an eruptive period, followed by a gradual return to the former baseline values. Gas flux data were also compared with seismic data for selected periods of interest, providing insights into the link between degassing and seismicity. The most important result from this comparison is the identification of an inflexion point in the gas emissions followed by a clearly increasing trend in seismic activity, distinguishable 6 months prior to a phreatic eruptive event that occurred on 5 January 2010. This signal can be interpreted as a possible indicator of future eruptive events. Monitoring of SO2 thus complements seismic monitoring as a forecasting tool for eruptive events. Such monitoring is critical considering the proximity of Turrialba to the Central Valley, an area inhabited by more than 50 % of Costa Rica's population.
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| 10. |
- De Moor, J. M., et al.
(författare)
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Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring
- 2016
-
Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202 .- 2169-9313. ; 121:8, s. 5761-5775
-
Tidskriftsartikel (refereegranskat)abstract
- Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San Jose. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/S-total>4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is similar to 8-10km deep, whereas the shallow magmatic gas source is at similar to 3-5km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000T/d SO2 and H2S/SO2>1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2
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| 11. |
- Galle, Bo, 1952, et al.
(författare)
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A multi-purpose, multi-rotor drone system for long-range and high-altitude volcanic gas plume measurements
- 2021
-
Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:6, s. 4255-4277
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Tidskriftsartikel (refereegranskat)abstract
- A multi-rotor drone has been adapted for studies of volcanic gas plumes. This adaptation includes improved capacity for high-altitude and long-range, real-time SO2 concentration monitoring, long-range manual control, remotely activated bag sampling and plume speed measurement capability. The drone is capable of acting as a stable platform for various instrument configurations, including multi-component gas analysis system (MultiGAS) instruments for in situ measurements of SO2, H2S, and CO2 concentrations in the gas plume and portable differential optical absorption spectrometer (MobileDOAS) instruments for spectroscopic measurement of total SO2 emission rate, remotely controlled gas sampling in bags and sampling with gas denuders for posterior analysis on the ground of isotopic composition and halogens. The platform we present was field-tested during three campaigns in Papua New Guinea: in 2016 at Tavurvur, Bagana and Ulawun volcanoes, in 2018 at Tavurvur and Langila volcanoes and in 2019 at Tavurvur and Manam volcanoes, as well as in Mt. Etna in Italy in 2017. This paper describes the drone platform and the multiple payloads, the various measurement strategies and an algorithm to correct for different response times of MultiGAS sensors. Specifically, we emphasize the need for an adaptive flight path, together with live data transmission of a plume tracer (such as SO2 concentration) to the ground station, to ensure optimal plume interception when operating beyond the visual line of sight. We present results from a comprehensive plume characterization obtained during a field deployment at Manam volcano in May 2019. The Papua New Guinea region, and particularly Manam volcano, has not been extensively studied for volcanic gases due to its remote location, inaccessible summit region and high level of volcanic activity. We demonstrate that the combination of a multi-rotor drone with modular payloads is a versatile solution to obtain the flux and composition of volcanic plumes, even for the case of a highly active volcano with a high-altitude plume such as Manam. Drone-based measurements offer a valuable solution to volcano research and monitoring applications and provide an alternativespan idCombining double low line"page4256"/> and complementary method to ground-based and direct sampling of volcanic gases.
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| 12. |
- Geirsson, H., et al.
(författare)
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Multidisciplinary observations of the 2011 explosive eruption of Telica volcano, Nicaragua: Implications for the dynamics of low-explosivity ash eruptions
- 2014
-
Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273. ; 271, s. 55-69
-
Tidskriftsartikel (refereegranskat)abstract
- We present multidisciplinary observations of the March-June 2011 VEI 2 eruptive episode of the basalticandesite Telica volcano, Nicaragua, which allow for a comprehensive study of the eruption mechanics of low-explosivity eruptions at persistently active volcanoes. The observations are from a dense network of seismic and GPS instrumentation augmented by visual observations of the eruptive episode, geochemical and petrologic analysis of eruptive products, plume SO2 measurements, and temperature measurements of fumaroles inside and outside the active vent. The 2011 eruptive episode was Telica's most explosive since 1999 and consisted of numerous vulcanian explosions, with maximum column heights of 1.5-2 km above the crater rim, depositing a low volume of dominantly hydrothermally altered ash. Based on observed variations in seismicity, temperature, and SO2 flux, the lack of deformation of the edifice, the non-juvenile origin of and predominance of accretionary lapilli in the ash, we propose that temporary sealing of the hydrothermal system between similar to 0.5 and 2 km depth, allowed pressure to build up prior to vulcanian explosions, making this a phreatic eruptive episode.
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| 13. |
- Gislason, S.R., et al.
(författare)
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Environmental pressure from the 2014–15 eruption of Bárðarbunga volcano, Iceland
- 2015
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Ingår i: Geochemical Perspectives Letters. - : European Association of Geochemistry. - 2410-3403 .- 2410-339X. ; 1:2015, s. 84 - 93
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Tidskriftsartikel (refereegranskat)abstract
- The effusive six months long 2014-2015 Bárðarbunga 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 surfacewaters, soils, and vegetation of Iceland.
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| 14. |
- Mellqvist, Johan, 1965, et al.
(författare)
-
Best practice report on compliance monitoring of ships with respect to current and future IMO regulation
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Since 2015, new rules from the International Maritime Organization (IMO) and legislation from EU and the US allows ships to run with maximum fuel sulfur content (FSC) of 0.1 % m/m on northern European and US waters, respectively, or use appropriate abatement technique. In addition, since 2020, there is a global cap of 0.5 % for the FSC. From 2021, northern Europe is a NOx emission control area, requiring at least 80 % emission reduction (Tier III) for all ships built from this year and onward, compared to ships built between 2000 and 2010 (Tier I). There is also a discussion within IMO how to control particle emission of black carbon (BC). This report focuses on best practice in remote compliance monitoring of FSC without stepping on board of the ship. Similar measurements for NOx are also shown, with a discussion whether these can be used for compliance monitoring. Some examples of remote measurements of BC are provided. Remote measurement methods for compliance monitoring of FSC in ships have been developed during the last 10 years within national and European projects (EnviSum and Compmon) and furthermore implemented in national monitoring in Belgium, Denmark, Germany the Netherlands and Sweden. The measurement methods are generally based on sniffer systems measuring the exhaust gas concentrations of SO2, NOx and particulate matter (BC), respectively, against CO2. There are systems with varying sensitivity that are operated at different distances from the ships (50 m to 2 km) and from different platforms, i.e. fixed, shipborne and airborne (manned and unmanned). There are also optical systems measuring the ratio of SO2 against NO2, as an indicator of the FSC, primarily used from manned aircraft. The focus in this report is on standard sniffer systems, based on generally available equipment for air quality monitoring. Such systems have been used extensively during the last 5 years for operational compliance monitoring from both fixed and airborne platforms. A summary of FSC measurement results for multiple operators and platforms shows that the noncompliance level has decreased significantly over the last 5 years at different parts of Europe, i.e. from 5-13 % in 2015 to below 1 % in 2020. The highest noncompliance levels were found at the SECA border in the English channel and in the middle of the Baltic sea. The measurement data, interpreted with ship modelling data from the Finnish Meteorological Institute, indicates that remote compliance monitoring of NOx should work reasonably well for ships operating at high loads (above 40 % load). For slow steaming ships the measurements are associated with larger uncertainties and care should be taken in the interpretation of then results here and further ship emission modelling is needed to assess this. The remote measurements of BC work well to identify high emitters and groups of polluting ships. However, the BC emissions have a strong load dependence are intermittent by nature and it is therefore difficult to make short term measurements. See https://cshipp.eu
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| 15. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Certification of an aircraft and airborne surveillance of fuel sulfur content in ships at the SECA border
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In 2015 new rules from the IMO and legislation from EU (Sulfur directive) and the US requires ships to run with maximum fuel sulfur content (FSC) of 0.1 % m/m in northern European and North American waters. In order to promote a level playing field within the shipping sector, there is a need for measurement systems that can make effective compliance control and this is the main objective of the CompMon project, funded through the European CEF program (Connecting Europe Facility). As part of this project, a sensor system has been certified for ship surveillance measurements in a Piper Navajo aircraft and it has been demonstrated for airborne measurements of FSC in individual ships on the English Channel. The measurement system consists of an optical module which measures total emissions of SO2 and NO2 in g/s and a sniffer system by which FSC is retrieved from extractive measurements of SO2 and CO2. It can be used from fixed sites, patrol vessels and from aircraft. The advantage with airborne surveillance is the capability to check ships that are operating in the main shipping lanes, up to 200 nautical miles from shore. The precision of the estimated FSC from the sniffer system is 0.05 % m/m and hence at the 95 % confidence limit, ships above a FSC of 0.2 % m/m can be checked. The sniffer system also has a negative bias in the FSC of approx- imately 0.04 % m/m which is accounted for in the FSC calculations. The optical system has larger measurement uncertainties than the sniffer but it is intended mostly for guid- ance of other controls. As part of the CompMon project, a measurements campaign with the Navajo Piper aircraft was carried out at the SECA (Sulfur Emission Control Area) border in the English Channel at longitude 5 W. Six flight missions with duration of 4 to 5 hours were carried out from September 2 to 10, 2016, flying from Brest airport. In this manner it was possible to cover the longitude range 2o - 6o W. During the campaign, 114 ships were measured with the sniffer system, corresponding to 71 ships inside the SECA and 42 ships outside. The level of compli- ance inside the SECA was here 87 % and this is considerably lower than measurements carried out elsewhere within CompMon in other parts of the SECA (95-99 %). Two thirds of the non-complying vessels were leav- ing the SECA. With the optical system 110 individual ships were measured, 42 outside and 68 inside the SE- CA. The measurements show a similar pattern as the sniffer data but with a few false values. Nevertheless it is shown that both low and high FSC ships will be classified correctly with about 80-90 % probability with the optical system and this system is hence very promising as a tool to guide further compliance controls.
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| 16. |
- Mellqvist, Johan, 1965, et al.
(författare)
-
Fixed remote surveillance of fuel sulfur content in ships from fixed sites in the Göteborg ship channel and Öresund bridge
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In 2015 new rules from the IMO and legislation from EU (Sulfur directive) and the US requires ships to run with maximum fuel sulfur content (FSC) of 0.1 % m/m in northern European and North American waters. In order to promote a level playing field within the shipping sector, there is a need for measurement systems that can make effective compliance control and this is the main objective of the CompMon project, funded through the European CEF program (Connecting Europe Facility). As part of this project, an automatic sniffer sensor system has been applied in the Göteborg ship channel at the Älvsborg island during 3 years (2014- 2016) and at the Öresund Bridge during two months at the end of 2016. The typical distances from the ships here varied between 500 -1000 m. The sniffer system is based on several extractive instruments measuring concentrations of SO2 and CO2 and others species, such as NOx, in the ship emission plumes that drift over the measurement station. In addition to fixed stations, the system can also be used from mobile platforms such as harbor patrol vessels and aircraft. From the data above, together with information about the ships from AIS (Automatic Identification System) and wind data, the FSC is automatically calculated and the ship is identi- fied. This is done using software developed as part of this project (Single Emitter identification Tool). The measurement precision (1σ) of the sniffer system is approx. 0.04 % m/m for ships using a FSC of 0.1 % m/m. The sniffer system also has a negative bias in the measured FSC, varying between 0.04 % to 0.08 % m/m and this is accounted for when calculating the threshold for non-compliance. Based on the above, it is possible to identify ships with FSC above 0.18 % m/m with 95% confidence limit, if the bias is corrected for statistically. For the measurements at the Älvsborg island site in 2014 and 2015, the corresponding limit is higher, 0.29 % m/m, due to a measurement artifact that was eliminated in 2016. On board measurements in 2015 and 2016 by the Swedish port state control authority shows that most non-compliant ships had FSCs be- tween 0.1 % to 0.2 % m/m when controlled at berth and this is generally below the 95% confidence limit threshold of the sniffer. Therefore many non-compliant ships will not be detected when using the sniffer close to harbors and a more precise sensor is therefore preferred. The measurements at the Älvsborg island were carried out during a time period when the allowed FSC limit changed significantly. The data for 2014, corresponding to more than 4000 measurements of 500 individual ships, shows that 99 % of the ships were using compliant fuel below the FSC limit of 1 % m/m. In 2015 the FSC limit changed to 0.1 % m/m. The measurements in 2015 and 2016, corresponding to the same amount of ships as in 2014, showed that 91.5 % and 98 %, respectively, were using compliant fuel with respect to FSC. The lower compliance rate in 2015 compared to 2016 is potentially influenced by measurement artifacts that were later eliminated in 2016. At the Öresund Bridge. 58 ships were measured as part of the CompMon pro- ject. The measurements continued another month with support from the interreg project Envisum, with anoth- er 62 ships measured. The compliance level at the Öresund Bridge corresponds to 98 %. This is actually com- parable to the corresponding measurements elsewhere and at the Älvsborg island site during the same time period.
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| 17. |
- Mellqvist, Johan, 1965, et al.
(författare)
-
Methane emissions from industrial activities using drones
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Innovative drone-based methods have been developed to map and quantify methane leakages from various industrial activities, such as refineries, Liquified Natural Gas (LNG) terminals, landfills, and water treatment facilities. These methods use a high-speed, high-sensitivity laser sensor and were validated through controlled gas releases. They were also compared to a ground-based infrared absorption-based technique. This initiative is supported by the Swedish Governmental Agency for Innovation Systems (Vinnova) and aligns with UN Sustainable Development Goals 9, 11, and 13. The goal is to reduce methane emissions significantly, aiding Sweden in achieving net-zero greenhouse gas emissions by 2045. Accurate measurements enable effective, targeted, and trackable measures to minimize emissions, resulting in a rapid positive climate impact. The project has led to the development of two distinct drone-based methods: the wall approach and the tracer approach. The wall approach measures gas concentrations across the entire cross-section of the plume, whereas the tracer approach measures the ratio of leaking gas to source gas. Depending on the source's size, one approach may be preferred over the other, with the tracer method being more suitable for point sources and the wall approach for larger sources. The custom-designed drone in this project, provided and operated by Gerdes Solution. is equipped with a high-sensitivity laser sensor and has a flight duration of about 12 minutes while carrying a 3 kg payload. This limitation presents a challenge when conducting wall measurements, which require approximately 25 minutes of flight time for the studied sources. Due to the drone's limited flight time, it necessitates landing and battery replacement, which complicates the process and limits the number of repeat measurements. In future endeavors, employing a drone with a longer flight duration would be advantageous. In total, the study detected about 220 kg/h of methane emissions and 3 kg/h of nitrous oxide emissions, equivalent to an emission rate of about 7 tons/h of carbon dioxide. The emissions were dominated by the water treatment plant and landfills, with relatively little coming from the refinery and LNG plant. However, the wall measurements in thus study serve as demonstrations of how the technique can be used and do not provide a comprehensive picture of the actual emissions from the individual sites; this would require more statistical data in terms of repeat measurements and measurement days. It is shown that drone measurements using the new high sensitivity laser is a valuable tool for mapping methane concentrations from various types of industrial sources, which are challenging to investigate today due to diffuse emissions, large dimensions, and complex geometries. The validation studies show that both the wall approach and controlled tracer releases can be used to quantify emissions, achieving an accuracy of up to 10 % for a simple, single, source. However, in the real measurement situation, the wall approach may be difficult to execute due to practical challenges like flying restrictions and the need for spatially dense data that can be interpolated to a homogenous grid and repeated measurements. In several cases, when the drone had to fly relatively close to the plumes, downwind of large buildings in complex and turbulent wind fields, the wall approach yielded large variability in the resulting flux. It is hence evident that the wall approach requires a thorough understanding of the measurement situation, and that repeated measurements are needed, at different distances from the source and in varying wind directions. The tracer approach was therefore preferred choice for obtaining emission rates in this study, although it is challenging to carry out representative tracer releases for larger sources and for cases when the measurements are performed near to the source, and in this case the wall approach is preferred. It was also shown that the drone-based tracer approach is advantageous to the ground based since it is then easier to capture the full plume.
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| 18. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Remote emission measurements of marine vessels in real operation to check compliance with IMO legislation and investigate influence on air quality
- 2019
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Ingår i: AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019.
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Konferensbidrag (refereegranskat)abstract
- A method has been developed and for remotely monitoring emissions from marine vessels and this has been used to investigate the effects of new sulfur fuel content regulations. The work has been carried out through the Danish Environmental Protection Agency10 and the EU projects Compmon7,8. The results show that between 87 and 98 percent of ships comply with the tougher regulations for sulfur emissions that were introduced in northern Europe in 2015. The lowest levels of compliance, 85-90%, were observed in the western part of the English Channel and in the middle of the Baltic Sea.
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| 19. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Results from exploratory project on NOx emissions from Ocean Going Vessels (OGV) using remote sniffer measurements (
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The NOx emissions from ships are governed by the International Maritime Organization (IMO) through MARPOL's Annex VI. This annex is part of the International Convention for the Prevention of Pollution from Ships. It establishes emission limits in the form of Tiers, which vary depending on the construction date of the ships and their engines. Our study concentrates on ships classified under Tiers 0 to II, as these are currently the most common vessels navigating the waters. In the study, mass- and brake-specific emissions of NOx at different ship engine loads were determined from six years of remote sniffer measurements at the Great Belt Bridge in Denmark. This bridge is situated over the main shipping channel connecting the Baltic Sea and the North Sea, with over 25,000 ships passing through annually. The analyzed data predominantly corresponds to 721 container ships, 425 RoRo vessels, 127 Reefers (refrigerated cargo), and 892 crude oil tankers, which are highly relevant for the ship types traversing Southern California waters to call Port of Los Angeles and the Port of Long Beach. Additionally, since vessels tend to reduce speed when approaching the Great Belt Bridge, the operational profiles of these ships are also very relevant for specific areas like Southern California, where multiple federal and local programs exist to encourage ships to voluntarily adopt reduced speeds as a strategy to either avoid whale strikes or decrease total emissions by reducing fuel consumption for the same distance travelled. The finding reveal that Tier II container ships have the highest brake-specific NOx emissions among all ship types and tiers and that they display a different emission load dependency. The Tier II engines are tuned to minimize emissions at higher engine loads. However, emissions significantly increase at lower loads, being 30 % higher compared to those at 70 % engine load. This is unlike the older Tier 0 and Tier I engines. Noteworthy is that the requirement in the IMO technical code is based on a weighted average which is heavily weighted against higher loads, typically 80 %, and therefore Tier II container vessels are still in compliance with the IMO rules when being measured on a test bed. It should also be noted that the emissions at engine loads below 25 % are not included for any of the tiers in the IMO rules. An observation from the study is that the obtained average emission factor (Eavg) for Tier II container ships was 17.7 g/kWh. While this is considerably lower than the 19.2 g/kWh observed for Tier 0 ships, it is significantly higher when compared to the NOx emission limit of 14.4 g/kWh as outlined in the NOx technical code. Part of this discrepancy might be attributed to uncertainties in the calculation of Specific Fuel Oil Consumption (SFOC) for the container ships and differences in the calculation of the weighted average, necessitating further investigation. It is noteworthy that the average emission factor (Eavg) for other ship types such as Reefers, RoRo, and crude oil tankers is significantly lower than that of container ships and are generally consistent with the requirement of being below 14.4 g/kWh. In conclusion, Tier II container ships, despite being optimized for reduced emissions at higher engine loads, display substantially increased emissions at lower engine loads compared to Tier I and Tier 0 container ships. Notably, ships have low engine loads when they navigate through nearshore shipping lanes to enter or exit a port. This is of concern for Vessel Speed Reduction (VSR) programs in areas like Southern California, since the elevated NOx emissions at lower loads could neutralize or even surpass the emission reductions these programs aim to achieve. We suggest that it would be beneficial if Tier II emissions could be abated through modifications in engine design or optimization, or potentially through retrofitting. This could be achieved through amendments to the IMO regulations and updates to the associated engine certification procedures. For example, this might involve giving more weight to emissions at low engine loads when calculating the emission limit, and including emissions below 25% engine load in the assessment.
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| 20. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Surveillance of Sulfur Emissions from Ships in Danish Waters
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In 2015 new rules from the IMO and legislation from EU (Sulfur directive) requires ships to run with maximum fuel sulfur content (FSC) of 0.1 % m/m in northern European waters. In order to promote a level playing field within the shipping sector, there is a need for measurement systems that can make effective compliance control. This report describes the results from ship emission measurements on the waters surrounding Denmark from June 2015 to July 2017 on behalf of the Danish Environmental Protection Agency. The overall aim was to carry out operational surveillance of ships with respect to the EU sulfur directive and particularly the sulfur limits for marine fuel in the European Sulfur Emission Control Area (0.10 %), which entered into force on January 1st 2015, as well as to guide further port state control of ships at the destination harbors of the ships, both in Denmark and other ports. During the project the FSC of individual ships was estimated by perform- ing spot checks of exhaust plumes of individual ships. This was conducted by automatic gas sniffer measurements at the Great Belt Bridge and airborne surveillance measurements using sniffer and optical sensors. The data from the fixed system were transmitted in real time to a web database and alarms were triggered for high FSC ships in the form of emails. The report describes the technical systems and their performance and the general compliance levels of the measured ships. The measurement systems have been developed by Chalmers University of Technology through Swedish national funding and the EU project CompMon. The airborne dataset corresponds to approx. 900 individual ships, measured by sniffer or/and optical sensor over 245 flight hours. The optical sensor has low precision and is therefore used as a first alert system to identify ships running on high sulfur fuel. The precision of the airborne FSC meas- urements by the sniffer system is better and it is estimated as ± 0.05 % m/m (1σ) with a systematic bias of - 0.045 % m/m. Therefore only ships running with FSC of 0.2 % m/m or higher can be de- tected as non-compliant ships with good confidence limit (95 %) by the airborne sniffer system. The airborne measurements during 2015 and 2016 on Danish waters show that 94 % of the ships complied with the EU Sulphur directive, at the 95 % confidence limit. The compliance rate was lower, 92 %, during the 2nd half of 2016. In the period June 2015 to May 2017, 8426 sniffer measurements of individual ships were carried out at the Great Belt Bridge. However, there were technical problems in the first part of the project and the sniffer therefore had reduced sensitivity the first year and only high sulfur ships (> 1 % FSC) could be detected as non-complying vessels with appropriate statistical confidence. The precision in the estimated FSC by the fixed sniffer system is estimated as ± 0.04 % m/m (1σ) with a systematic bias of - 0.055 % m/m. Therefore only ships running with FSC of 0.18 % or higher can be detected as non-compliant ships with good confidence limit (95 %) by the fixed sniffer system. The data for the period June 2016 to October 2016 show a compliance rate of 94.6 % which increased to 97.4 % in the period January 2017 to May 2017. The compliance level during different time periods and platforms varied between 92-97 %. Here 1 - 2 % of the ships were in gross non-compliance with the EU sulfur directive with FSC values above 0.5 % m/m. There were differences over time, with the highest values in the summer of 2016. The compliance level was close to the values (95 %) measured by port state control authorities in Sweden and Denmark 2015 and 2016. When comparing ships measured by port state and the ones in this project it can be deduced that the efficiency of finding non-compliant vessels could be increased by at least a factor of 4, if the port state controls were guided by measurements. Most of the non-compliant ships (90 %) were measured high only once. But there were cases with individual ships and ship operators that were more abundant in the non-compliance statistics. The non- compliant ships that were seldom in the area around Denmark had higher emissions of SO2 than the non-compliant ones that operated their more frequently. On several occasions during this study we encountered ships equipped with scrubbers that were non-compliant with respect to the EU sulfur directive.
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| 21. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Surveillance of Sulfur Fuel Content in Ships at the Great Belt Bridge 2019
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Results are reported from stack gas emission measurements of individual ships at the Great Belt bridge in Denmark. From the data the fuel sulfur content (FSC) used by the ships has been estimated. The project has been carried out on behalf of the Danish Environmental Protection Agency and the contract covers the period March 2018 to December 2018. The measurements reported here cover the period March to November 2018 and in addition we report measurements during January and February 2018, carried out as part of the EU project Envisum. The overall aim of the project was to carry out operational surveillance of ships with respect to the EU sulfur directive and particularly the sulfur limits for marine fuel in SECAs (0.10 %), which entered into force on January 1st 2015, as well as to guide further port state control of ships at the destination harbors of the ships, both in Denmark and other ports. The main objective of this report is to describe the technical systems and their performance, although a discussion about the general compliance levels with respect to the EU sulfur directive is provided as well. The surveillance measurements were conducted by automatic gas sniffer measurements at the Great Belt Bridge, reporting in real time to a web database. The measurement systems have been developed by Chalmers University of Technology through Swedish national funding and EU projects. In the period January 2018 to November 2018, 3580 valid sniffer measurements of individual ships were carried out at the Great Belt Bridge (medium and good quality). The precision of the fixed sniffer is estimated as ±0.04 FSC % (1σ) with an estimated systematic bias of - 0.074 % FSC for the measurements in 2018, based on comparisons with port state control authorities. Therefore, only ships running with an FSC of 0.18 % or higher can be detected as noncompliant ships with confidence limit of 95 % by the fixed sniffer system, when accounting for the bias. The data for the period January to November show a compliance rate of 95.3 %. Here 1.1 % of the ships were in gross non-compliance with the EU sulfur directive with values above 0.5 %. Additional 0.8 % of the ships were measured in the FSC interval 0.3-0.5 % while the rest had values below 0.3%. There are differences over time, with the highest values in the summer. On several occasions we encountered one specific ship that was non-compliant with respect to the EU sulfur directive and which was equipped with a scrubber that was being commissioned.
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| 22. |
- Mellqvist, Johan, 1965, et al.
(författare)
-
Surveillance of Sulfur Fuel Content in Ships at the Great Belt Bridge 2020
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Results are reported from stack gas emission measurements of individual ships at the Great Belt Bridge in Denmark. From the data the fuel sulfur content (FSC) used by the ships has been estimated. The project has been carried out on behalf of the Danish Environmental Pro-tection Agency and this report covers the period December 2019 to November 9, 2020. The overall aim of the project was to carry out operational surveillance of ships with respect to the EU sulfur directive that was entered into force in 2015 and which is implemented in the Danish legislation. It requires the usage of low sulfur marine fuel in SECAs (0.10 %) or using abate-ment technique (e.g. scrubber), The main purpose of the surveillance was to guide further port state control of ships at the destination harbors of the ships, both in Denmark and other ports, and to gather general statistics about compliance rates. This report describes the technical systems and their performance and discusses the general compliance levels with respect to the EU sulfur directive and Danish legislation. The surveil-lance measurements were conducted by automatic gas sniffer measurements at the Great Belt Bridge, reporting in real time to a web database. The measurement systems have been developed by Chalmers University of Technology through Swedish national funding and EU projects. The measurement system at the Great Belt Bridge has been in operation since 2015. In the period December 2019 to November 9, 2020, 3910 valid sniffer measurements of indi-vidual ships were carried out at the Great Belt Bridge with medium and good quality. The pre-cision of the fixed sniffer is estimated as 0.04 FSC % (1σ) and therefore only ships running with an FSC of 0.18 % (2σ) or higher can be detected as non-compliant ships with reasonable statistical confidence. The sniffer also has an estimated systematic bias of - 0.077 % FSC for the measurements in 2020, based on comparisons with port state control authorities. This bias, together with the measurement precision, is accounted for when determining the non-compliance threshold value. The data for the period December 2019 to November 9, 2020 shows a compliance rate of 98.6 %. This corresponds to 55 non-compliant ships (1.4 %) and out of these only 1 ship (i.e. 0.03 %) was in gross non-compliance, i.e. running with FSC above 0.3 % while the rest had an FSC below 0.14 %. This is slightly lower than in 2019 (4 ships corresponding to 0.075% above FSC 0.3 %) and it can be compared to the correspond-ing numbers for 2018 when the compliance rate was 95.3 % and 1.8 % of the ships were in gross noncompliance. One reason for the improvements could be that scrubber installations appears to work better in 2019 and 2020 compared to the previous years. The observed high and improved compliance rate in 2020 is similar to the measurements in 2019 and consistent with other measurement studies in northern Europe during 2019. Airborne mini-sniffer measurements of 600 ships around the coast of Denmark, on behalf of the Danish EPA, shows 50 % less noncompliance between 2018 and 2019, with only 3 ships above FSC of 0.3 %. Sniffer measurements carried out in Belgian waters, in the English Channel, by fixed wing aircraft show that the non-compliance rates of ships with FSC above 0.4% changed from 4.9 % to 0.4 % between 2018 and 2019, with similar values in 2020. Fixed site measurements in the ship channel to Hamburg shows improved compliance rates since 2015 with noncompli-ance rates less than 1 % in Wedel and Bremerhaven in 2019. Sniffer measurements at the Öresund Bridge by Chalmers University of Technology, on behalf of Swedish transport agency, shows 99.7% compliance rates in 2020 with no ships in gross noncompliance. https://www2.mst.dk/Udgiv/publications/2020/12/978-87-7038-250-2.pdf
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| 23. |
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| 24. |
- Pfeffer, M. A., et al.
(författare)
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Ground-Based measurements of the 2014-2015 holuhraun volcanic cloud (Iceland)
- 2018
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Ingår i: Geosciences (Switzerland). - : MDPI AG. - 2076-3263. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The 2014-2015 Bárðarbunga fissure eruption at Holuhraun in central Iceland was distinguished by the high emission of gases, in total 9.6 Mt SO 2 , with almost no tephra. This work collates all ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense cloud with high SO 2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, developing ramparts, and high-latitude winter conditions. Semi-continuous measurements of SO 2 flux with three scanning DOAS instruments were augmented by car traverses along the ring-road and along the lava. The ratios of other gases/SO 2 were measured by OP-FTIR, MultiGAS, and filter packs. Ratios of SO 2 /HCl = 30-110 and SO 2 /HF = 30-130 show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3-5.5 km agl were measured with ground-and aircraft-based visual observations, web camera and NicAIR II infrared images, triangulation of scanning DOAS instruments, and the location of SO 2 peaks measured by DOAS traverses. Cloud height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting.
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| 25. |
- Saballos, J. A., et al.
(författare)
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Relatively short-term correlation among deformation, degassing, and seismicity: a case study from Concepcion volcano, Nicaragua
- 2014
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Ingår i: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 76:8, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Concepcion is a frequently active composite volcano in Nicaragua, and is located on Ometepe Island, within Lake Nicaragua. Significant eruptive activity took place at this volcano between March and May 2010, consisting of ash and gas explosions (VEI 1-2). We compare geodetic baseline changes observed with global positioning system (GPS), sulfur dioxide flux (SO2), and seismic amplitude (SAM) data collected at Concepcion during April - June, 2010, and February - April, 2011. Time series analysis reveals a remarkable correlation among the data sets during 2010, when the volcano was erupting. In contrast, the volcano was at its background level of activity in 2011 and the statistical correlation among the time series is not significant for this period. We explain the emergence of correlation among the time series during eruptive activity through modeling of the GPS data with emplacement of a magma column in an open conduit. In the model, magma rose in the conduit, between May 5 and 14, 2010, from a shallow reservoir located at similar to 1.8 km depth. Later, between May 24 and 31, 2010, the top of the magma column descended to almost 600m depth, corresponding to the cessation of eruptive activity. Thus, cross-correlation and an integrated analysis of these geophysical time series on a timescale of days helps to reveal the dynamics of the magma plumbing system operating below Concepcion volcano.
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