| 1. |
- Kern, Christoph, et al.
(author)
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Halogen oxide measurements at Masaya Volcano, Nicaragua using active long path differential optical absorption spectroscopy
- 2009
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In: Bulletin of Volcanology. - 0258-8900 .- 1432-0819. ; 71, s. 659-670
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Journal article (peer-reviewed)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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| 2. |
- Rivera, Claudia, 1976
(author)
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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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Doctoral thesis (other academic/artistic)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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| 3. |
- Rivera, Claudia, 1976, et al.
(author)
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Tula industrial complex (Mexico) emissions of SO2 and NO2 during the MCMA 2006 field campaign using a mobile mini-DOAS system
- 2009
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9, s. 6351-6361
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Journal article (peer-reviewed)abstract
- The Mexico City Metropolitan Area (MCMA) has presented severe pollution problems for many years. There are several point and mobile emission sources inside and outside the MCMA which are known to affect air quality in the area. In particular, speculation has risen as to whether the Tula industrial complex, located 60 km northwest of the MCMA has any influence on high SO2 levels occurring on the northern part of the city, in the winter season mainly. As part of the MILAGRO Field Campaign, from 24 March to 17 April 2006, the differential vertical columns of sulfur dioxide (SO2) and nitrogen dioxide (NO2) were measured during plume transects in the neighborhood of the Tula industrial complex using mobile mini-DOAS instruments. Vertical profiles of wind speed and direction obtained from pilot balloons and radiosondes were used to calculate SO2 and NO2 emissions. According to our measurements, calculated average emissions of SO2 and NO2 during the field campaign were 384 ± 103 and 24 ± 7 tons day-1, respectively. The standard deviation of these estimations is due to actual variations in the observed emissions from the refinery and power plant, as well as to the uncertainty in the wind fields at the exact time of the measurements. Reported values in recent inventories were found to be in good agreement with calculated emissions during the field campaign. Our measurements were also found to be in good agreement with simulated plumes.
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| 4. |
- Rivera, Claudia, 1976, et al.
(author)
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Validation of optical remote sensing measurement strategies applied to industrial gas emissions
- 2009
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In: International Journal of Remote Sensing. - : Informa UK Limited. - 1366-5901 .- 0143-1161. ; 30:12, s. 3191-3204
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Journal article (peer-reviewed)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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