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Carbon dioxide (CO2) is colorless, odorless and also heavier than air, which means it can accumulate at low elevations. At high concentrations, CO2 can be hazardous and can cause asphyxiation by reducing the amount of oxygen available to breathe. In high concentrations, it can also irritate the eyes, nose, and throat. During the post-eruptive phase of Tajogaite eruption, high concentrations of air CO2, up to 20% (200,000 ppmv), have been detected both outdoor and indoor of buildings at La Bombilla and Puerto Naos, which are located about 5 km from the eruption vent. Hazardous CO2 concentrations were detected not only in the basements, but also on the ground floors and even inside of some upper floors buildings in Puerto Naos. In the case of La Bombilla, relatively high CO2 concentrations were just observed on the ground floors. The spatial distribution of these hazardous indoor CO2 concentrations is not uniform throughout both populated areas (Hernández et al, 2022).In order to study and assess this volcanic hazard, in both evacuated neighborhoods, an instrumental network for air CO2 monitoring has been established by INVOLCAN in collaboration with the DGSE-GOBCAN and the Universities of the Azores (Portugal) and Düsseldorf Applied Sciences (Germany). The first CO2 monitoring station was installed on 9 January 2022 and by the time being this network consists of 35 air CO2 monitoring stations with different full scale (2 of 100%, 22 of 20%, 7 of 5% and 4 of 4%). In the case of La Bombilla the air CO2 monitoring network consists of 10 different stations monitoring the indoor (7) and outdoor (3) CO2 concentrations, respectively. The other 25 stations are located in Puerto Naos to monitor the indoor (21) and outdoor (4) ambient air CO2 concentrations.Observed outdoor CO2 maximum and mean daily average concentrations > 5% (> 50,000 ppmv) and 0.9% (9,000 ppmv), respectively, have been recorded at Puerto Naos. However, indoor CO2 monitoring at Puerto Naos have reached maximum and mean daily average concentrations about 20% (200,000 ppmv) and 12% (120,000 ppmv), respectively. In the case of La Bombilla, outdoor CO2 measurements have reached maximum and mean daily average concentrations > 5% (> 50,000 ppmv) and about 2% (20,000 ppmv). Stations to monitor the indoor air CO2 concentrations at La Bombilla were just installed (December 2022) and by the time being are recording maximum and mean CO2 concentrations about 6% (60,000 ppmv) and 1.9% (19,000 ppmv), respectively. Most of the air CO2 monitoring stations, both outdoor and indoor, shows that the daily averages of CO2 concentrations from fifteen-minute data during the night are usually higher than during the day.To mitigate the observed hazardous CO2 concentrations some remediation techniques have been suggested, such as the installation of an indoor air CO2 monitoring network with a larger number of stations and an automatic alert system for air CO2 concentration inside residences with forced air ventilation systems.Hernández P. A. et al., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.

Heterogeneous catalysts usually consist of porous, inorganic materials. Especially in the mobile application, e.g., in exhaust gas catalysis as a part of the gas line of an engine, there are loads due to vibrations and high gas velocities. It can be assumed that physical stress will lead to a loss of the catalytically active coating. The present contribution describes experimental setups and methods for a systematic and reproducible investigation of the main influences to the mass loss due to vibrational and fluid-mechanical stress caused by particle-free gas flows.

Volcanic areas frequently have diffuse gas emission of CO2, SO2, H2S and even more. Normally these diffuse emissions do not vary only by time but also with location. Therefore, the spatial variation of concentrations cannot be monitored with one measurement system alone. On the other hand, the strength of gaseous volcanic emissions is often correlated with volcanic activity and can potentially endanger population in the vicinity.For this reason, we developed a light new low-cost unit for the parallel measurement of various gases like CO2, SO2 and H2S, which has the remarkable advantage of being able to transmit the measured data and GPS position with LTE to a remote server. Moreover, it can operate in an unattended way for days or even weeks, depending on the customizable operation modus of the unit and the capacity of the attached rechargeable battery. A solar-powered version is currently in development. The evaluation of the received data can be performed online on the server and the results are displayed continuously. The software is programmed by us in a way that alarms can be started in case that concentrations exceed predefined alarm thresholds also via email.The electronic hardware unit is designed in a way that it can be equipped with low-cost NDIR sensors, electrochemical sensors or photoacoustic sensors (e.g. for CO2: Sensirion SCD41). There are 4 analog ports (selectable voltage or current).The operation procedure of the sensors electronics is customizable as well: The operation can be changed from continuous running to following mode:Measurement period, low power sleep period, sensor warm up-period, measurement period etc. The length of all these time periods of the operation procedure can be varied depending on the measurement needs. That means for long runtime of the measurement a long sleeping time between the measurement periods can be chosen. On the other hand, if low power consumption and long runtime are not necessary, short sleeping periods or even the continuous running mode can be chosen. The operation configuration, e.g. sleeping time, can be changed by remote firmware update.

There are frequent measurement tasks, where lightweight low-cost sensor units are of interest for the parallel measurement of several environmental parameters. Moreover, often measurements of environmental parameters are necessary not only at one specific point, but distributed over a large area or at different altidudes. In this case it makes sense to utilize lightweight low-cost sensor units. Because of the low price the can be produced in many exemplares und used at several places in parallel. The Laboratory for Environmental Measurement Techniques (UMT) at the Duesseldorf University of Applied Sciences (HSD) has developed such electronic units with following features: They can measure particulate matter PM10, PM2.5, PM1, PNC and size distribution using particulate sensors of different brands, e.g. Alphasense sensors R2 or N3 or Sensirion SDS 30. Additionally they have analog interfaces so that they can be equipped with sensor units for gaseous pollutants, e.g, Alphasense sensors for SO2, NO2, Ozone and many other gases like CO2 using Sensirion sensors. In parallel atmospheric pressure, temperature and humidity can be measured by additional dedicated sensors. The sensor units are equipped with a SD card memory and optionally with I2C or RS232 interface. Additionally the data can be transmitted in a wireless way to a server on 433 MHz, 868 MHz, 2.4 GHz ISM-band or via LTE or IRIDIUM. The main electronic unit is of lightweight design. Therefore the low-cost sensor units can be used easily on mobile platformes like drones or bicycles. The sensor unit has a low power consumption, so it can be operated independently for days or weeks, depending on the battery capacity. A GPS module enables a timestamp for the data and gives position and altitude. Several fully installed measurement units have been tested by UMT groundbased at industrial and heavily polluted urban sites in Germany. Moreover, such a unit has been operated on a measurement drone for taking vertical and horizontal pollutant profiles. It is planned to use these sensor units also at volcanic sites in a mobile and stationary way. The low-cost sensor units have been intercompared with certified air pollution measurement systems to assure the data quality.

The eruption begun after an intensive earthquake activity in the volcanic system of Reykjanes that opened up several kilometer long underground dike crossing the plate boundary of Reykjanes at an angle of around 22°. Quakes of varying intensity caused material damage in the township of Grindavik, the major population center in the neighborhood. The eruption came on March 20th, with put any clear warning, a magma eruption without much ash formation but when reaching the surface, the magma released gasses in a magnitude similar to other volcanic eruption of this type, e.g., Holuhraun (magma from Bardarbunga) 2014 and Surtsey 1963 - 1967. A characteristic SO2 emission in this eruption was measured 6kg/sec of SO2 from each m3 of magma or 2 o/ o o. This is similar to what was observed in the Holuhraun airborne observation campaign and corresponds very well to the estimates for Surtsey. The composition of the volcanic gas is similar too, the main constituent is water, often 90 - 55% of the total gas flow. The magma is 1200 - 1300 °C hot and comes from a very deep source about 20 km down. The possibility exists that the eruption goes on for a long time, widens the conduit and increases in output. An airborne measurement campaign was conducted in a light airplane, TF-VTR, by Dr. Gylfi Arnason, Reykjavik University (RU) with a mobile remote sensing DOAS instrumentation specially adapted for use in this airplane from the Duesseldorf University of Applied Sciences (HSD), Germany. This observation technology has been used with good results during volcanic events in Europe, Japan and America. Four sorties were carried out, measuring the column load of SO2 by flying under the plume in several traverses, each giving about 20 measurements of the SO2 column load. The results are compared to other measurement results from IMO (Icelandic Meteorological Institute) and UI (University of Iceland) and results from previous campaigns 2014 and 1963 - 67 and found similar. In the beginning the eruption output was steady at 5 m3/sec but was increasing in output magnitude and pulsating, making gas flux estimations more difficult. A steady plume in a steady wind follows the dispersion model developed by the authors, but the pulsating plume creates large puffs with high gas concentrations and increased hazards for nearby populations centers. Gas accumulation in a large clouds during calm weather, observed during the 2014 Holuhraun event, does also happen here and increases the risk of serious pollution events. This seriously hampers the possibility of using modeling results only to estimate gas pollution risks, and stresses the need for monitoring the gas flow by airborne measurements of the propagation of the plumes, puffs and accumulated clouds that may threaten the neighborhood.

Instrumented UAS (unmanned aerial systems, drones) can substantially enhance the capabilities for the investigation of air pollutants, when equipped with the appropriate and customized air pollution measurement systems. Important advantages can be found in the exploration of vertical and horizontal pollutant profiles as well as in the determination of fugitive emissions. The HSD Laboratory for Environmental Measurement Techniques (UMT) has developed a series of different multicopter UAS for various measurement tasks and payloads. Additionally, different commercial UAS are used by UMT. The multicopter UAS are equipped, depending on the measurement task, with different specifically adopted lightweight measurement systems for aerosols (PM10, PM2.5, PM1, UFP, PNC, number size distributions) or gases like O3, SO2, NOX, CO2 and VOCs. All measurement systems were intercompared with certified standard measurement equipment before use to assure the quality of the measurement results. Moreover, physical samples of aerosols can be taken during the flight, which enables a chemical or REM analysis after the flight.Additionally, UMT developed an on-line data transmission system, which allows the transmission of measurement data during the flights from the UAS to the ground for continuous monitoring. In this way concentration plumes can be tracked and hotspots can be pinpointed during the flight. This online data transmission system is independent of commercial platforms, can work on different radio frequencies in a push mode (presently on 2.4 GHz) and communicates with RS232 and I2C interfaces. Within several intercomparison studies this online data transmission proved a high reliability and correctness of transmitted data.In addition to technical details of the UAS and instrumentation we present in this contribution the results of different measurement campaigns based on our UAS measurements:Investigations of emissions from the Duesseldorf airport combining upwind and downwind UAS measurements. These investigations became of special interest, as due to the reduced air traffic caused by the Corona pandemia now single aircraft starts and landings could be monitored with their emissions at elevated altitudes. Investigations of vertical concentration profiles above the city of Duesseldorf, which could be influenced by industrial sites in the north of Duesseldorf as well as by the Duesseldorf airport. Investigations of vertical and horizontal pollution distributions near, at and around industrial sites in the Rhine Ruhr area, especially of metal industry plants and chemical plants. These examples highlight the capabilities of UAS measurements, which will be further enhanced by planned simultaneous use of several UAS in parallel and joint tasks.

One of the main compounds emitted by volcanoes or volcanic fields is CO2. This is not only emitted from localized craters, but can emerge as distributed and fugitive emission from extended volcanic regions. In this situation it is of interest to explore the distribution and horizontal concentration profiles of the CO2-emissions. For this purpose new dropsondes for sensor measurements of CO2 emissions are under development at the Duesseldorf University of Applied Sciences. These dropsondes are designed to be dropped from aircraft or drones over volcanic areas in order to map the distributed CO2 concentrations over longer times in an unattended way. They are very lightweight and cheap, so that a large number of dropsondes might be deployed even over remote areas or regions with difficult access. The data are transmitted with GSM broadcasting and can be visualized on a geographical map.The dropsondes use an NDIR CO2 sensor as a basis for the measurement unit. Additionally to the concentration of CO2 the atmospheric pressure, temperature and humidity are measured. The sensor unit is mounted in a special shock absorbing housing, which is designed to absorb impacts from the touch down after dropping of the sensor and is able to resist even adverse weather conditions.First measurement results and more details of the design of the sensor unit are presented in this contribution.

A volcanic ash (VA) test stand has been built with a precise particle feeder, concentration measuring unit and a mini turbine with an integrated thermal barrier coating (TBC) system on the blisk for the first time in a laboratory scale. This setup has allowed the testing of melting, sticking, corrosion and erosion behaviour of volcanic ash in-situ at high temperature in a realistic manner in a gas turbine. Moreover, this mini engine runs with kerosene which could also bring all the impurities such as sulphur in to system which might change the reaction mechanisms of TBC and VA. The particle size influence on the sticking/escape behaviour in the engine components was tested but a clear statement on the particle size versus its sticking behaviour could not be made, although the particles in the size range of 1-10 µm are more susceptible to melting in the given conditions. The blisks were coated with two different TBC materials such as 7 wt.% Yttria Stabilised Zirconia (7YSZ) and Gadolinium Zirconate (GZO) using Electron Beam Physical Vapour Deposition (EB-PVD) technique. Both coatings were tested in corrosion-erosion regime under VA at high temperature and it was found out that the coating with higher toughness (7YSZ) has performed better than the other coating under the used testing conditions.

The science of measuring airborne volcanic ash concentrations supports research in such fields as atmospheric environmental science and the modeling of atmospheric pollution from volcanoes, and is thus very valuable to the aviation industry. These measurements show large scatter directly traceable to turbulent fluctuations responsible for diffusing volcanic dust. Before semistationary components in observations can be compared to each other or to simulation results, they must be separated from fluctuations. In the design of the separation process, however, neither seasonal or diurnal periodicity nor random disturbance with known properties exists to serve as a guideline. It has been suggested that fluctuations could be eliminated through repeated convolutions of a simple 3-point filter enough times. The number of convolutions is chosen from the change in the rate of increase of a special variability parameter. When semistationary concentrations are separated from fluctuations, their statistics are compared to turbulence parameters and the autocorrelation of the series. The method is demonstrated using three measurement series from Sakurajima, Japan measured in 2013. It is concluded that this new method is simple and trustworthy where knowledge and experience of the environmental parameters can be utilized to support the results. They indicate a variability of 40% in the relative fluctuations of the PM10 and around 20% of the PM2.5. The relative fluctuations may be considered completely random, but normally distributed rather than a white noise with an evenly distributed variance spectrum.

Volcanic eruptions have caused very costly disturbances of international air traffic. This problem has been dealt with by simulating the formation and migration of dangerous ash plumes. However, the results of the simulations have sometimes been too safe, producing ash clouds that are too large. This was especially the case for the North Atlantic in 2010 (Eyjafjallajökull) and 2011 (Grímsvötn). Since 2012, an international cooperation team led by the Disaster Prevention Research Institute (DPRI) of Kyoto University has conducted airborne measurements of volcanic ash concentrations in the plume from Mount Sakurajima in Kagoshima Prefecture, Japan. This volcano was chosen because of its frequent but limited eruptions, which allow close observation. These measurement campaigns have provided data showing gravitational flattening of the plume, a new and previously unknown dispersion process of volcanic plumes. A new and previously unknown fallout process, called streak fallout, also has been measured. Results concerning plume flux, concentration distributions, aerosol (PM10) content of the plume, and content of very fine particles (PM2.5 and PM1) are presented, and the ways by which the observational methods can be used to produce reliable initial data and boundary values for simulations of plume dispersion are discussed.

Passive Fourier Transform Infrared (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) techniques, i.e. those making use of natural radiation sources are used since the 1970s for the remote sensing of trace gases in the atmosphere. Characteristic for these methods is that they can be put to stationary or mobile use (e.g. cars, multicopters, balloons, aircraft, satellites), are capable of very quickly generating indicative data over a large measurement range and permit quantitative determinations of defined substances. A number of distinct method variations has been developed for specific purposes that cover a broad range of applications in emission and ambient air measurements. These reasons prompted the Commission on Air Pollution Prevention of VDI and DIN (a standards committee of the German Standards Institute) to establish the German Standards VDI 4211 and 4212 on these techniques. Both Standards are also intended to support and encourage manufacturers and start-ups to develop and produce marketable instruments in consideration of future air monitoring concepts (small, mobile, versatile, multi-component analysers). In order to pave the way for these methods to be recognized by the authorities as equivalent methods to established air quality monitoring methods experience-based minimum requirements for selected performance characteristics are recommended which may be the basis for a future type testing procedure.

Spatial distributions of bromine monoxide (BrO), chlorine dioxide (OClO) and sulfur dioxide (SO 2 ) were determined in the volcanic emissions of Mt. Etna on 8th and 9th of July 2011 by Airborne Imaging Differential Optical Absorption Spectroscopy (AI-DOAS). Slant column densities (SCDs in units of molec/cm 2 ) of up to 4.2 × 10 14 for BrO, 1.5 × 10 14 for OClO and 4.6 × 10 18 for SO 2 were detected. Assuming SO 2 to be a stable tracer to overcome dilution effects, measurements of BrO/SO 2 and OClO/SO 2 ratios from distances of 1–19 km to the summit crater region were used to investigate the evolution of BrO and OClO within corresponding plume ages of 2–34 min. Along the centerline of the plume relatively constant BrO/SO 2 ratios of 1.4 × 10 − 4 and 2.0 × 10 − 4 were detected on 8th and 9th of July 2011, respectively. Furthermore the BrO/SO 2 ratio was investigated along several cross-sections of the volcanic plume. On both days significant increases by a factor of 2–3 in the BrO/SO 2 ratio from the center to the edge of the plume were seen. From simultaneous measurements of BrO and OClO the mixing ratios of ClO could be inferred to range from about 80 to 300 ppt. In addition, decreases in the BrO/SO 2 ratio with time could be observed by measurements three to four hours before the culmination of a paroxysm at Mt. Etna on 9th July 2011.

We investigated the micro-scale variability of particle number and mass concentrations in the urban atmosphere of Leipzig, Germany. Particles were sampled in May and June 2011 using portable instrumentation along a fixed measurement route, representing different degrees of outdoor particle exposure that can be experienced by a pedestrian. The instrumentation comprised a Grimm NanoCheck sensor for particle number (25-300 nm) and a Grimm OPC for particle mass concentrations. The mobile measurements conducted at a time resolution of 10 s revealed rich details in the spatio-temporal distribution of urban particles that were not visible in fixed-site measurements. Motor traffic proved to be a major source of particle number and mass in the area, although the corresponding concentrations declined rapidly when moving away from the traffic sources. The experiments demonstrate that traffic-free zones and green park areas are useful measures to limit outdoor exposure to traffic-related particles even if they are rather modest in size. Unexpected findings include high fine particle concentrations (PM[0.25;1]) near outdoor seating areas of restaurants, and the apparent dependence of coarse particle concentrations (PM[2.5;10]) on the ability of surfaces to release particles by resuspension. The study illustrates the usefulness of the spatial sensing of airborne particles in the urban roughness layer and encourages the use of such data for the validation of micro-scale dispersion models.

The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain, resulting in inaccurate volcanic ash forecasts in these distal areas. In our approach, we use real-life aircraft in situ observations, measured in the northwestern part of Germany during the 2010 Eyjafjallajökull eruption, in an ensemble-based data assimilation system combined with a volcanic ash transport model to investigate the potential improvement on the forecast accuracy with regard to the distal volcanic ash plume. We show that the error of the analyzed volcanic ash state can be significantly reduced through assimilating real-life in situ measurements. After a continuous assimilation, it is shown that the aviation advice for Germany, the Netherlands and Luxembourg can be significantly improved. We suggest that with suitable aircrafts measuring once per day across the distal volcanic ash plume, the description and prediction of volcanic ash clouds in these areas can be greatly improved.

Airborne volcanic ash particles are a known hazard to aviation. Currently, there are no means available to detect ash in flight as the particles are too fine (radii μm) for on-board radar detection and, even in good visibility, ash clouds are difficult or impossible to detect by eye. The economic cost and societal impact of the April/May 2010 Icelandic eruption of Eyjafjallajökull generated renewed interest in finding ways to identify airborne volcanic ash in order to keep airspace open and avoid aircraft groundings. We have designed and built a bi-spectral, fast-sampling, uncooled infrared camera device (AVOID) to examine its ability to detect volcanic ash from commercial jet aircraft at distances of more than 50 km ahead. Here we report results of an experiment conducted over the Atlantic Ocean, off the coast of France, confirming the ability of the device to detect and quantify volcanic ash in an artificial ash cloud created by dispersal of volcanic ash from a second aircraft. A third aircraft was used to measure the ash in situ using optical particle counters. The cloud was composed of very fine ash (mean radii ~10 μm) collected from Iceland immediately after the Eyjafjallajökull eruption and had a vertical thickness of ~200 m, a width of ~2 km and length of between 2 and 12 km. Concentrations of ~200 μg m−3 were identified by AVOID at distances from ~20 km to ~70 km. For the first time, airborne remote detection of volcanic ash has been successfully demonstrated from a long-range flight test aircraft.

In this chapter, in situ measurements of airborne ash from manned aircraft are presented, and best practice for aircraft choice and sampling strategy, particularly around the use of optical particle counters (OPCs), is discussed. Results are described from in situ measurement campaigns from Eyjafjallajokull, Grimsvotn, Holuhraun, and Sakurajima. The most important parameters, in terms of measurement error from OPCs, are the aerodynamic diameter and refractive index of the particles. Other parameters, such as shape and orientation, also affect the detection, but these effects are less well understood. Finally, the relationship between observations and dispersion models, particularly around advection–diffusion assumptions, including from gravitational dispersion and streak fallouts, are highlighted.

Mean and turbulent flow characteristics together with particle concentrations were measured in a busy urban street canyon in Essen, Germany, at five (flow characteristics) and three heights (particles) above ground, respectively. Particle mass and number concentrations were sampled in the size range 0.3

In the summer of 1998, the air quality (indicators: CO, NO, NO2 ,O 3) above the water surface of the Lake Balderey (Essen, Ruhr area, North Rhine-Westphalia, Germany), an artificial lake used for recreation purposes, was measured using the Fourier transform infrared spectroscopy (FTIR) and differential optical absorption spectroscopy (DOAS) remote measurement methods. The lake, with an area of 3 km 2 was created by damming the Ruhr and is surrounded by higher ground. In calm, bright weather conditions, this location results in a low-exchange situation (formation of temperature inversions, cold air dynamics) with a sustained impact on pollutant concentrations over the lake. The results of trace substance measurements (1/2 h mean values) were compared with values from comparison stations (suburban, high traffic and forest) located outside the area of the lake. In general, it was found that mean CO and NO concentrations over the lake were very low (0.3 ppm and 7.5 ppb, respectively). NO2 values (B15 ppb) were some 3.5 times higher than those recorded at the forest station and O3 values, at 27 ppb, almost reached the same level as at the forest station (30 ppb). Mass flow densities as a function of wind direction, diurnal courses, differences between weekdays and weekends and comparisons with air quality standards are presented for the lake station. r 2002 Elsevier Science Ltd. All rights reserved.

Volcanic ash concentrations in the plume from Sakurajima volcano in Japan are observed from airplanes equipped with optical particle counters and GPS tracking devices. The volcano emits several puffs a day. The puffs are also recorded by the Sakurajima Volcanological Observatory. High concentrations are observed in the puffs and fallout driven by vertical air current, called streak fallout. Puffs dispersion is analyzed by the classical diffusion-advection method and a new gravitational dispersion method. The fluid mechanic of the gravitational dispersion, streak fallout, and classical diffusion-advection theory is described in three separate appendices together with methods to find the time gravitational dispersion constant and the diffusion coefficient from satellite photos. The diffusion-advection equation may be used to scale volcanic eruptions so the same eruption plumes can be scaled to constant flux and wind conditions or two eruptions can be scaled to each other. The dispersion analyses show that dispersion of volcanic plumes does not follow either theories completely. It is most likely diffusion in the interface of the plume and the ambient air, together with gravitational flattening of the plumes core. This means larger boundary concentration gradients and smaller diffusion coefficients than state of the art methods can predict.

Modeling the transport of volcanic ash and gases released during volcanic eruptions is crucially dependent on knowledge of the source term of the eruption, that is, the source strength as a function of altitude and time. For the first time, an inversion method is used to estimate the source terms of both volcanic sulfur dioxide (SO2) and ash. It was applied to the explosive volcanic eruption of Grimsvotn, Iceland, in May 2011. The method uses input from the particle dispersion model, FLEXPART (flexible particle dispersion model), a priori source estimates, and satellite observations of SO2 or ash total columns from Infrared Atmospheric Sounding Interferometer to separately obtain the source terms for volcanic SO2 and fine ash. The estimated source terms show that SO2 was emitted mostly to high altitudes (5 to 13 km) during about 18 h (22 May, 00-18 UTC) while fine ash was emitted mostly to low altitudes (below 4 km) during roughly 24 h (22 May 06 UTC to 23 May 06 UTC). FLEXPART simulations using the estimated source terms show a clear separation of SO2 (transported mostly northwestward) and the fine ash (transported mostly southeastward). This corresponds well with independent satellite observations and measured aerosol mass concentrations and lidar measurements at surface stations in Scandinavia. Aircraft measurements above Iceland and Germany confirmed that the ash was located in the lower atmosphere. This demonstrates that the inversion method, in this case, is able to distinguish between emission heights of SO2 and ash and can capture resulting differences in transport patterns. Key Points Ash and SO2 source terms estimated using inverse techniques and satellite data The transport and separation of ash and SO2 are modeled Model simulations correspond well with a range of independent observations ©2014. The Authors.

TATP is a very easy to synthesize [9], sensitive, high explosive [10] and high volatile explosive [1, 3, 7] with great absorption in the IR Spectra [4, 5, 6]. In this project we detect TATP gas traces with open path FTIR – techniques. The first project phase was to construct and build a heatable multi-reflection cell with adjustable optical path length and a heatable intake to evaporate solid TATP samples. In this cell reference TATP - spectra were collected under controlled conditions with a Bruker FTIR system (Typ OPAG 33). The next step was to find out how the TATP gas will be diluted in the ambient air and validate some physical properties which are described inconsistently in literature e.g. evaporation rates. We constructed a special double - T shaped chamber with stabile air conditions. In this chamber the dispersion kinetics of the TATP vapour could be tested. It turned out that the TATP vapours has the tendency to drop down. Therefore the highest TATP - concentrations were measured below the TATP sample. During the investigation for this study it turned out, that some materials scrub the TATP- vapour out of the air, e.g. Metals, fabric, leather. In the second phase of the project successful open path FTIR- measurements were taken in ambient air and will be continued with different system configurations of the OPAG 33 to lower the detection limits. Also successful measurements were taken in indoor ambient air with a Hyper spectral camera (passive FTIR with array sensor) to detect TATP in solid and gaseous phase. This technique allows detecting TATP and identifying the TATP source. The poster shows some selected results of the continued research.

[1] Eyjafjallajokull, a volcano in southern Iceland, erupted explosively in April and May 2010 depositing ash over a region of more than 3000 km2 to the east and southeast of the volcano. This deposited ash has been frequently remobilized by the wind causing concern for the health of Icelanders living in the region. An investigation was carried out to determine whether it would be possible to produce forecasts of days when high airborne ash concentrations were likely to occur. Information about the spatially varying surface characteristics of the region of deposited ash is not available so in the modeling approach adopted here ash is released from the surface at a rate proportional to the cube of the excess friction velocity (local friction velocity minus a threshold) only when the friction velocity exceeds a threshold. Movement of the resuspended ash is then modeled in a Lagrangian dispersion model. Modeled ash concentrations are compared to observed concentrations from two periods; PM10 observations between 23 May and 2 July 2010 and airborne particle counts between 21 September 2010 and 16 February 2011. More than 66% of the resuspension episodes between May and July are captured by the model and the relative magnitudes of the modeled episodes in this period are in good agreement with the observations. 66% of episodes between October and February are also captured by the model although there is an increase in the false alarm rate which appears to be due to the influence of precipitation.

Gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent Colli Albani volcano. These zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth. All extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells. The gas, mainly composed of CO 2 (>90 vol.%), contains appreciable quantities of H 2 S (0.35–6 vol.%), and both represent a potentially high local hazard. Both gases are denser than air and accumulate near ground where they may reach hazardous concentrations, and lethal accidents frequently occur to animals watering at local ponds. In order to evaluate the rate of degassing and the related hazard, CO 2 and H 2 S diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber. The viscous gas flux of some important discrete emissions has been evaluated and the CO 2 and H 2 S air concentration measured by portable devices and by Tunable Diode Laser profiles. The minimum potential lethal concentration of the two gases (250 ppm for H 2 S and 8 vol.% for CO 2 ) is 320 times higher for CO 2 , whereas the CO 2 /H 2 S concentration ratio in the emitted natural gas is significantly lower (15–159). This explains why H 2 S reaches hazardous, even lethal, concentrations more frequently than CO 2 . A relevant hazard exists for both gases in the depressed zones (channels, excavations) particularly in the non-windy early hours of the day.

Because of the potential impact on agriculture and other key human activities, efforts have been dedicated to the local control of precipitation. The most common approach consists of dispersing small particles of dry ice, silver iodide, or other salts in the atmosphere. Here we show, using field experiments conducted under various atmospheric conditions, that laser filaments can induce water condensation and fast droplet growth up to several μm in diameter in the atmosphere as soon as the relative humidity exceeds 70%. We propose that this effect relies mainly on photochemical formation of p.p.m.-range concentrations of hygroscopic HNO3, allowing efficient binary HNO3–H2O condensation in the laser filaments. Thermodynamic, as well as kinetic, numerical modelling based on this scenario semiquantitatively reproduces the experimental results, suggesting that particle stabilization by HNO3 has a substantial role in the laser-induced condensation., Various methods have been investigated to locally control atmospheric precipitation. In this study, field experiments show that laser-induced condensation is initiated when the relative humidity exceeds 70%, and that this effect is largely a result of photochemical HNO3 formation.

We investigate the influence of laser parameters on laser assisted water condensation in the atmosphere. Pulse energy is the most critical parameter. Nanoparticle generation depends linearly on energy beyond the filamentation threshold. Shorter pulses are more efficient than longer ones with saturation at similar to 1.5 ps. Multifilamenting beams appear more efficient than strongly focused ones in triggering the condensation and growth of submicronic particles while polarization has a negligible influence on the process. The data suggest that the initiation of laser assisted condensation relies on the photodissociation of the air molecules rather than on their photoionization. (c) 2011 American Institute of Physics. [doi:10.1063/1.3546172]

During the eruption phase of the Icelandic volcano Eyjafjallajokull in April/May 2010 the University of Applied Sciences Duesseldorf has performed 14 measurement flights over north-western Germany in the time period of 23 April 2010 to 21 May 2010. Additionally 4 flights have been performed for visual observations, referencing and transfer. The measurement flights have been performed in situations, where the ash plume was present over north-western Germany as well as in situations, when there was no ash plume predicted. For the measurements a light aircraft (Flight Design CTSW Shortwing) was used, which was equipped with an optical particle counter (Grimm 1.107). Additionally the aircraft was equipped for one flight with an UV-DOAS system and a CO2-measurement system. The optical particle counter allowed in-situ measurements of the particle distribution between 250 nm and 32 μm and of PM10, PM2.5 and PM1. The ash plume appeared during the measurements as inhomogeneous in structure. Layers or multilayers of one hundred meters to a few hundred meters vertical depth of ash plume could be identified. Sub-plumes with a horizontal extension of several kilometres to several tenths of kilometres could be found. The layers of the ash plume could be found in altitudes between 2500m and 4500m. The measured concentrations have been compared with the concentration and extension of the ash plume predicted by the Volcanic Ash Advisory Centre (VAAC).

A VDI/DIN guideline for passive FTIR spectrometry is under development. The topics will be: Basics of the techniques: principles for the detection of gaseous clouds and exhaust composition, radiative transfer model, radiative temperature, noise equivalent column density and detection limits; Measurement systems: Fourier transform spectroscopy, Michelson interferometers, measurement configurations, spectrometers with one detector element, scanning systems, scanning imaging systems, spectrometers with a detector array; Calibration: radiometric calibration, system calibration; Remote sensing of gases at ambient temperature: basics, identification of gases, quantifications, application examples; Remote sensing of gases at high temperatures: basics, quantification of gas temperature, quantification of composition, application examples; Remote sensing of gases by means of solar radiation: basics, measurement performance, data analyses, application examples.

An innovative tunable diode laser (TDL) measurement system has been used for the on-line estimation of emissions of cars, driving through the measurement beam of the system. This paper describes the measurement principle and gives first measurement results, taken for different types of cars.

In summer 1998 a measurement campaign was performed at the lake Baldeney See in the south of the city of Essen in Germany. Two major goals should be achieved: First the intercomparison of several different remote sensing systems in real field measurements and second the determination of the ozone levels during summer with respect to the complex orographic and climatological situation of the lake Baldeney See which is intensely used as a recreational area. This paper refers to the results of the intercomparison of the remote sensing systems open-path FTIR, DOAS and TDL and presents a new automatic background generation routine for analyzing the FTIR spectra.

The OP-FTIR measurement technique and other remote sensing systems (for example UV-DOAS and TDL) become more and more established methods to monitor the ambient air quality. Some quality assurance procedures have to be done on the field measurement data to get more reliable results. Both the German and US-EPA standardization documents for the OP-FTIR technique prescribe such procedures to check the data. To assess the applicability of these procedures, OP-FTIR field measurement data of a three month continuous measurement campaign were evaluated concerning the signal strength, the influence of stray light, water vapor concentration, baseline noise, wave number shifts and the detection limits. In addition the long time signal stability of the OP-FTIR systems and the UV-DOAS systems are intercompared. The results of the several quality assurance procedures will be presented in this paper.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In summer 1998 a measurement campaign was performed at the lake Baldeney See in the south of the city of Essen in Germany. Two major goals should be achieved: First the intercomparison of several different remote sensing systems in real field measurements and second the determination of the ozone levels during summer with respect to the complex orographic and climatological situation of the lake Baldeney See which is intensely used as a recreational area. This paper only refers to the first results of the intercomparison of the remote sensing systems open-path FTIR, DOAS, and TDL and some interesting features of the ozone concentration results like secondary ozone peak concentration during night time.

Infrared Fourier transform open-path spectroscopy becomes a more and more well-known method to monitor air pollution. Several companies are even selling instruments especially devoted to this application. Numerous campaigns have delivered interesting information and proved the usefulness of the technique. However the results still suffer from a certain mistrust. Reliability, reproducibility, stability are for instance not yet well defined. In order to fill this lack, we have performed a set of test measurements which could be carried out on any FTIR long-path system. This quality assurance protocol includes the determination of noise, return signal stability, detection limits, precision and accuracy. The procedure to estimate each of these parameters is described. The feasibility and relevance of these measurements have been tested on both monostatic and bistatic set-ups. Both instruments have been studied over a period of several months. Many of the parameters can be calculated without doing extra measurements and were evaluated whenever the instruments were in use. To determine parameters such accuracy and precision, series of spectra were especially acquired. This shows the possibility to better quantify the performance of open-path FTIR spectrometers. Further improvements are also suggested.

The substantiation of the characteristics, which make the Open-Path FTIR technique attractive for monitoring the ambient air quality, is the aim of a validation program, which is realized at the Fachhochschule Duesseldorf. Part of this validation program are calibration measurement, which are important to determine the performance characteristics of a remote FTIR system. The measurements are carried out at the official calibration laboratory of the Environmental State Agency of Northrhine Westphalia and at the Laboratory for Environmental Measurement Techniques at the Fachhochschule Duesseldorf, using a high resolution Open- Path FTIR spectrometer combined with an adjustable gas cell from 7 to 110 meters. The calibrations were done for methane in a concentration range from 20 to 10000 ppm.m and are evaluated corresponding to the standardization documents which are currently used to determine the performance characteristics of continuous measurement systems. It turned out that the calculated calibration function for methane is nonlinear when analyzing by the classical least square algorithm. Furthermore, if using a nonlinear calibration function over the whole concentration range, the correction of measured concentrations and the calculation of the lower detection limits leads to unrealistic high values. Better results were achieved by separating the whole concentration range in a linear one at low concentrations and a nonlinear one at high concentrations in order to determine the characteristics of the used remote FTIR system.

A calibration experiment was performed by the Fachhochschule Duesseldorf in cooperation with the official calibration laboratory of the Environmental State Agency of Northrhine Westphalia. This was the first calibration of an OP-FTIR spectrometer at an official calibration laboratory in Germany. The calibration measurements were carried out along the standard ISO/DIS 9169, 'air quality - determination of performance characteristics of measurement methods'. A multipass cell with a light path of 20m was used. During these measurements the deviation between the calibration gas concentration and the measured concentration increased rapidly with higher concentration. This indicates a nonlinear calibration function of the OP-FTIR spectrometer used here and might be addressed to the used spectral resolution of 1.0 wavenumbers. The calibration measurements are still running for other gases and other OP-FTIR spectrometers.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The 'Commission of Air Pollution Prevention in VDI and DIN', which is officially responsible for the setting of written standards in the field of air pollution in Germany, has established a working group for standardization of open-path FTIR measurements in Germany. This group has presently worked out has worked out a draft for a VDI-guideline, in which it is laid down, how to perform measurements with the open-path FTIR to get reliable results.

We compare laser-induced condensation by UV laser pulses of femtosecond, sub-picosecond, and nanosecond duration between each other, as well as with respect to near-infrared (NIR) (800 nm) ultrashort laser pulses. Particle nucleation by UV pulses is so efficient that their growth beyond several hundreds of nm is limited by the local concentration of water vapour molecules. Furthermore, we evidence a dual mechanism: While condensation induced by ultrashort UV pulses rely on nitrogen photo-oxidative chemistry like in the NIR, nanosecond laser-induced condensation occurs without NO2 production, evidencing the domination of a mechanism distinct from that previously identified in the femtosecond regime.

The open-path FTIR (op-FTIR) measurement method has several characteristics, which make the method attractive for monitoring air pollutants in urban areas. In this paper recent op-FTIR measurements at an urban site in Germany are presented. These measurements include the first direct intercomparisons between op-FTIR measurements and an official measurement system of the Environmental State Agency in North- Rhine-Westphalia. These intercomparisons revealed very good results.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Emissions of air pollutants from industrial sources are of major public concern in Germany. Remarkable efforts have been made to control and reduce there emissions. A strong reduction of these so-called classical air pollutants like e.g. SO2 out of channeled industrial sources could be recorded throughout the last years. However, at some industrial sites there are still several measurement problems that cannot always be solved appropriately by conventional measurement systems. For example, screening of fugitive emissions or sudden releases out of leakages is difficult to monitor correctly by conventional point sensors. In these cases the open-path FTIR method can show up with several advantages because of its measurement principle. In this paper, different open-path measurements at industrial sites are presented, including measurements of sudden releases of ammonia and measurements at and above an olefin production plant.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Using 100 TW laser pulses, we demonstrate that laser-induced nanometric particle generation in air increases much faster than the beam-averaged incident intensity. This increase is due to a contribution from the photon bath, which adds up with the previously identified one from the filaments and becomes dominant above 550 GW/cm2. It appears related to ozone formation via multiphoton dissociation of the oxygen molecules and demonstrates the critical need for further increasing the laser energy in view of macroscopic effects in laser-induced condensation.

Der Anwendungsbereich der optischen Fernmesverfahren last sich in zwei Bereiche einteilen: erstens wissenschaftliche und zweitens administrative Anwendungen.