| 1. |
- Johansson, Mattias Erik, 1980, et al.
(författare)
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Mobile mini-DOAS measurement of the outflow of NO2 and HCHO from Mexico City
- 2009
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9, s. 5647-5653
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Tidskriftsartikel (refereegranskat)abstract
- We here present the results from mobile measurements using two ground-based zenith viewing Differential Optical Absorption Spectroscopy (DOAS) instruments. The measurement was performed in a cross-section of the plume from the Mexico City Metropolitan Area (MCMA) on 10 March 2006 as part of the MILAGRO field campaign. The two instruments operated in the UV and the visible wavelength region respectively and have been used to derive the differential vertical columns of HCHO and NO2 above the measurement route. This is the first time the mobile mini-DOAS instrument has been able to measure HCHO, one of the chemically most important and interesting gases in the polluted urban atmosphere.Using a mass-averaged wind speed and wind direction from the WRF model the instantaneous flux of HCHO and NO2 has been calculated from the measurements and the results are compared to the CAMx chemical model. The calculated flux through the measured cross-section was 1.9 (1.5–2.2) kg/s of HCHO and 4.4 (4.0–5.0) kg/s of NO2 using the UV instrument and 3.66 (3.63–3.73) kg/s of NO2 using the visible light instrument. The modeled values from CAMx for the outflow of both NO2 and HCHO, 1.1 and 3.6 kg/s, respectively, show a reasonable agreement with the measurement derived fluxes.
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| 2. |
- Johansson, Mattias Erik, 1980, et al.
(författare)
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The Dual-Beam mini-DOAS technique - measurements of volcanic gas emission, plume height and plume speed with a single instrument
- 2009
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Ingår i: Bulletin of Volcanology. - 0258-8900 .- 1432-0819. ; 71, s. 747-751
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Tidskriftsartikel (refereegranskat)abstract
- The largest error in determining volcanic gas fluxes using ground based optical remote sensing instruments is typically the determination of the plume speed, and in the case of fixed scanning instruments also the plume height. We here present a newly developed technique capable of measuring plume height, plume speed and gas flux using one single instrument by simultaneously collecting scattered sunlight in two directions. The angle between the two measurement directions is fixed, removing the need for time consuming in-field calibrations. The plume height and gas flux is measured by traversing the plume and the plume speed by performing a stationary measurement underneath the plume. The instrument was tested in a field campaign in May 2005 at Mt. Etna, Italy, where the measured results are compared to wind fields derived from a meso-scale meteorological model (MM5). The test and comparison show that the instrument is functioning and capable of estimating wind speed at the plume height.
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| 3. |
- Johansson, Mattias Erik, 1980, et al.
(författare)
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Tomographic reconstruction of gas plumes using scanning DOAS
- 2009
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Ingår i: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 71:10, s. 1169-1178
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method to reconstruct the gas distribution inside a vertical cross section of a gas plume by combining data from two or more scanning DOAS instruments using a tomographic algorithm. The method can be applied to gas plumes from any single, elevated point source, such as a volcano or industrial chimney. Such two-dimensional concentration distributions may prove to be useful for example in plume chemistry, dispersion and environmental impact studies. Here we show the case with one scanning DOAS instrument located on each side of the plume, which is the easiest and most economic setup as well as the most useful in routine monitoring of e.g. volcanic gas emissions. The paper investigates the conditions under which tomographic reconstructions can be performed and discusses limitations of this setup. The proposed method has been studied theoretically by numerical simulations and has been experimentally tested during two field campaigns, with measurements of SO2 emissions from a volcano and a power plant. The simulations show that, under good measurement conditions, the algorithm presented performs well, which is further confirmed by the experimental results.
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| 4. |
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| 5. |
- Rivera, Claudia, 1976, et al.
(författare)
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Validation of optical remote sensing measurement strategies applied to industrial gas emissions
- 2009
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 1366-5901 .- 0143-1161. ; 30:12, s. 3191-3204
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Tidskriftsartikel (refereegranskat)abstract
- In May 2004 a field-campaign was conducted at a power plant in Spain, aiming at validating the use of a miniaturized, fibre-optic, ultraviolet, differential optical absorption spectrometer (mini-DOAS) instrument for sulphur dioxide flux (SO2) quantification. Emissions were determined by integrating the total number of molecules in a vertical cross-section of the gas plume, and multiplying them by the wind component at plume height. Calculated wind data was compared with balloon soundings. Plume height, computed from a tomographic reconstruction of the plume was compared with stereo-photogrammetric methods and a plume rise model. Finally, SO2 fluxes were compared to emissions reported by the power station. Although the meteorological conditions during the field-campaign were adverse, with large fluctuations in wind-speed and wind-direction, the optical measurements performed proved to be practically feasible and compared well with the techniques used for the validation. SO2 fluxes derived by mini-DOAS were within 7% of the ones reported by the power station.
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| 6. |
- De Gouw, J. A., et al.
(författare)
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Airborne Measurements of Ethene from Industrial Sources Using Laser Photo-Acoustic Spectroscopy
- 2009
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:7, s. 2437-2442
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Tidskriftsartikel (refereegranskat)abstract
- A laser photoacoustic spectroscopy (LPAS) instrument was developed and used for aircraft measurements of ethene from industrial sources near Houston, Texas. The instrument provided 20 s measurements with a detection limit of less than 0.7 ppbv. Data from this instrument and from the GC-FID analysis of air samples collected in flight agreed within 15% on average. Ethene fluxes from the Mt. Belvieu chemical complex to the northeast of Houston were quantified during 10 different flights. The average flux was 520 +/- 140 kg h(-1) in agreement with independent results from solar occultation flux (SOF) measurements, and roughly an order of magnitude higher than regulatory emission inventories indicate. This study shows that ethene emissions are routinely at levels that qualify as emission upsets, which need to be reported to regional air quality managers.
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| 7. |
- Grutter, M., et al.
(författare)
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SO2 emissions from Popocatépetl volcano: emission rates and plume imaging using optical remote sensing techniques
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8, s. 6655-6663
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Tidskriftsartikel (refereegranskat)abstract
- Sulfur dioxide emissions from the Popocatépetl volcano in central Mexico were measured during the MILAGRO field campaign in March 2006. A stationary scanning DOAS (Differential Optical Absorption Spectrometer) was used to monitor the SO2 emissions from the volcano and the results were compared with traverses done with a COSPEC from the ground and a DOAS instrument on board an ultra-light aircraft. Daytime evolutions as well as day-to-day variation of the SO2 emissions are reported. A value of 2.45±1.39 Gg/day of SO2 is reported from all the daily averages obtained during the month of March 2006, with large variation in maximum and minimum daily averages of 5.97 and 0.56 Gg/day, respectively. The large short-term fluctuations in the SO2 emissions obtained could be confirmed through 2-D visualizations of the SO2 plume measured with a scanning imaging infrared spectrometer. This instrument, based on the passive detection of thermal radiation from the volcanic gas and analysis with FTIR spectrometry, is used for the first time for plume visualization of a specific volcanic gas. A 48-h forward trajectory analysis indicates that the volcanic plume was predominantly directed towards the Puebla/Tlaxcala region (63%), followed by the Mexico City and Cuernavaca/Cuautla regions with 19 and 18% occurrences, respectively. 25% of the modeled trajectories going towards the Puebla region reached altitudes lower than 4000 m a.s.l. but all trajectories remained over this altitude for the other two regions.
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| 8. |
- Kern, Christoph, et al.
(författare)
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Halogen oxide measurements at Masaya Volcano, Nicaragua using active long path differential optical absorption spectroscopy
- 2009
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Ingår i: Bulletin of Volcanology. - 0258-8900 .- 1432-0819. ; 71, s. 659-670
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Tidskriftsartikel (refereegranskat)abstract
- Active Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) measurements of halogen oxides were conducted at Masaya Volcano, in Nicaragua from April 14 to 26, 2007. The active LP-DOAS system allowed night-time halogen measurements and reduced the ClO detection limit by an order of magnitude when compared to previous passive DOAS measurements, as wavelengths below 300 nm could be used for the DOAS retrievals. BrO was detected with an average BrO/SO2 molecular ratio of approximately 3 × 10−5 during the day. However, BrO values were below the detection limit of the instrument for all night-time measurements, a strong indication that BrO is not directly emitted, but rather the result of photochemical formation in the plume itself according to the autocatalytic “bromine explosion” mechanism. Despite the increased sensitivity, both ClO and OClO could not be detected. The achieved upper limits for the X/SO2 ratios were 5 × 10−3 and 7 × 10−6, respectively. A rough calculation suggests that ClO and OClO should be present at similar abundances in volcanic plumes. Since the DOAS technique is orders of magnitude more sensitive for OClO than for ClO, this indicates that OClO should always be detectable in plumes in which ClO is found. However, further LP-DOAS studies are needed to conclusively clarify the role of chlorine oxides in volcanic plumes.
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| 9. |
- Olmos, R., et al.
(författare)
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Anomalous emissions of SO2 during the recent eruption of Santa Ana volcano, El Salvador, Central America
- 2007
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Ingår i: Pure and Applied Geophysics. - : Springer Science and Business Media LLC. - 0033-4553 .- 1420-9136. ; 164:12, s. 2489-2506
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Tidskriftsartikel (refereegranskat)abstract
- Santa Ana volcano in western El Salvador, Central America, had a phreatic eruption at 8:05 am (local time) on October 1, 2005, 101 years after its last eruption. However, during the last one hundred years this volcano has presented periods of quiet degassing with fumarolic activity and an acidic lake within its crater. This paper presents results of frequent measurements of SO2 degassing using the MiniDOAS (Differential Optical Absorption Spectroscopy) system and a comparison with the volcanic seismicity prior to the eruption, during, and after the eruption. Vehicle measurements of SO2 flux were taken every hour during the first nine days of the eruption and daily after that. The period of time reported here is from August to December, 2005. Three periods of degassing are distinguished: pre-eruptive, eruptive, and post-eruptive periods. The intense activity at Santa Ana volcano started in July 2005. During the pre-eruptive period up to 4306 and 5154 ton/day of SO2 flux were recorded on October 24 and September 9, 2005, respectively. These values were of the same order of magnitude as the recorded values just after the October 1(st) eruption (2925 ton/day at 10: 01 am). Hourly measurements of SO2 flux taken during the first nine days after the main eruptive event indicate that explosions are preceded by an increase in SO2 flux and that this parameter reaches a peak after the explosion took place. This behavior suggests that increasing accumulation of exsolved magmatic gases occurs within the magmatic chamber before the explosions, increasing the pressure until the point of explosion. A correlation between SO2 fluxes and RSAM (Real Time Seismic Amplitude Measurements) is observed during the complete sampling period. Periodic fluctuations in the SO2 and RSAM values during the entire study period are observed. One possible mechanism explaining these fluctuations it that convective circulation within the magmatic chamber can bring fresh magma periodically to shallow levels, allowing increasing degasification and then decreasing degasification as the batch of magma lowers its gas content, becomes denser, and sinks to give space to a new magma pulse. These results illustrate that the measurements of SO2 flux can provide important warning signals for incoming explosive activity in active volcanoes.
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| 10. |
- Rivera, Claudia, 1976
(författare)
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Application of Passive DOAS using Scattered Sunlight for quantification of gas emissions from anthropogenic and volcanic sources
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Monitoring of gas emissions from natural and anthropogenic sources is important due to the negative effects of these emissions on human health, atmospheric quality and ecosystems. Concern over air pollution has increased the need to develop measurement techniques suitable for gas flux determination. Differential Optical Absorption Spectroscopy (DOAS) is a method based on the interaction of light with matter. DOAS has been widely used during the past decades, is capable of quantifying several molecules simultaneously, provides results in real time with good time resolution and is non invasive, as well as precise and flexible to use in different conditions and environments.In this thesis, instruments based on scattered sunlight spectroscopy have been used to successfully quantify gas emissions from anthropogenic (refineries, power plants, chemical industries, urban areas) and volcanic sources during several field campaigns. The studied gas species were sulphur and nitrogen dioxides (SO2, NO2) mainly because of their negative effects on human health as well as oxidation capability, formation of sulphuric and nitric acids respectively and further dry or wet deposition; as well as formaldehyde (HCHO), which plays an important role in the chemistry of the troposphere.Results presented in this thesis demonstrate that the use of mobile and scanning mini-DOAS instruments are accurate for wind speed and plume height calculations as well as for quantification of SO2, NO2 and HCHO emissions. Calculated SO2 and NO2 emissions from Mexican refineries and power plants, conducted during field studies presented in this thesis, are in agreement with published inventories and indicate a significant reduction in emissions over recent years. Measurements conducted in the Houston-Galveston region in the United States show that SO2 and NO2 quantified emissions in some of the industrial areas were comparable with the reported values in the inventory, however slightly above the reported values. In addition HCHO has been identified in urban (Mexico City) and industrial (Houston, Texas) areas.The capability to continuously quantify gas emissions from volcanoes, using scanning mini-DOAS instruments, provides volcanic observatories with a new tool that allows them not only to react when facing a volcanic crisis but also to act proactively and in the best interest of the affected population. Quantified emissions from volcanic sources have been correlated to volcanic seismic activity in order to improve geophysical understanding of volcanic systems and thereby improve volcanic risk assessment.
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