Ash Mass Concentration Research Articles

Strength test and reinforcement mechanism of gangue-building solid waste-based cement filling material improved by soda residue

To utilize solid soda residue (SR) and building solid waste (BSW), this study proposes to use SR for modification and preparation of mining-used soda residue-gangue-building solid waste-based cement filling material (SGBCFM). In this study, we studied the influence of fly ash (FA) content, SR content, BSW content, and mass concentration (MC) on the early strength and later strength of SGBCFM. Through XRD and SEM tests, we analyzed the hydration products and microstructure of SGBCFM and investigated the mechanism of SR enhancing the later strength of SGBCFM. The results show that these influencing factors have a weaker impact on the early strength of SGBCFM, but a significant impact on later strength. These influencing factors can be ranked from the most significant impact to the least impact as follows: MC, SR content, FA content, and BSW content. A proper amount of SR can effectively improve the later strength of the material, but an excessive amount of SR leads to a decrease in strength; SR has combined effects such as micro-aggregate filling, alkali activation, and promoting cementation reactions. These effects can increase the original cementitious substances and generate new compounds, effectively enhancing the later strength of SGBCFM.

Study on Resistance Loss of Fly Ash Slurry Multistage High‐Pressure Grouting Pipeline Based on Fluent

In order to understand the resistance loss along the way during multistage high‐pressure slurry transportation, the flow state of fly ash slurry in the pipeline was simulated by Fluent software in this paper, and the effects of pipe diameter D, pipe transportation flow rate Q, and fly ash mass concentration Cw on the resistance loss along the pipeline were studied. The fly ash slurry is a non‐Newtonian Bingham fluid that moves in a turbulent state in a pipeline. When simulating the flow of fly ash slurry using Fluent software, the mesh type is a mixed mesh of hexahedron and wedge shapes, and the viscous model is selected as realizable k‐ε Turbulence Model, with Enhanced‐Wall Function (EWF) selected as the wall function, combined with a four‐layer boundary layer mesh, which can more accurately capture the details of velocity changes at the wall, thereby improving the accuracy of the model. The inlet of the model is the velocity inlet, and the outlet is the pressure outlet. The coupled algorithm is chosen as the solution method. Under these conditions, the model converges quickly and the calculation accuracy is high. The results show that the resistance loss along the pipeline decreases as a power function with the increase of pipeline diameter, and there is a polynomial relationship between the pipeline flow and the resistance loss along the pipeline, while the mass concentration of fly ash slurry changes linearly with the resistance loss along the pipeline. In addition, three friction coefficient models, namely Blasius formula, Colebrook–White equation, and Wilson–Thomas model, were selected according to the flow characteristics of fly ash slurry. Based on the Blasius formula with the smallest relative calculation error, the Blasius formula was modified by multiple linear regression analysis to improve the accuracy of the frictional resistance coefficient model and to provide help for the design and use of separate layer grouting conveying system.

Rheological and mechanical performance analysis and proportion optimization of cemented gangue backfill materials based on response surface methodology.

Cemented backfill mining is a green mining method that enhances the coal mining rate and the safety of mined-out regions. To transport the cemented gangue backfill material (CGBM) into the mined-out regions, it is essential to ensure high flowability and adequate compressive strength after hardening. Based on the response surface methodology (RSM), 29 experiments were conducted in this paper to test the yield stress and plastic viscosity of CGBM slurry. Cubic specimens with dimensions of 100mm were prepared and underwent uniaxial compression tests to obtain the compressive strength at a curing age of 28days. Quadratic polynomial regression models were established for yield stress, plastic viscosity, and compressive strength to explore the effects of fly ash content, water-cement ratio, mass concentration, and superplasticizer dosage on the properties of CGBM. Multi-objective optimization was conducted to determine the optimal material proportion of CGBM. The research results indicate that (1) the mass concentration most profoundly affected the yield stress and plastic viscosity of CGBM, and it increased with an increase in mass concentration. Fly ash content had an inverse relationship with compressive strength. Superplasticizer was found to improve the flowability and strength of CGBM. (2) The established response surface model could reflect the relationship between CGBM's material proportion and rheological and mechanical properties, and predict relevant parameters. (3) Multi-objective optimization determined the optimal proportion of CGBM to be 80% fly ash content, 54% water-cement ratio, 79% mass concentration, and 3% superplasticizer dosage. The research findings offer valuable guidance to mining backfill engineering.

Understanding the effect of high-volume fly ash on micro-structure and mechanical properties of cemented coal gangue paste backfill

The utilization of coal gangue and fly ash to produce cemented paste backfill is an effective strategy to mitigate the environmental impact of such bulk solid wastes. In this study, we aimed to investigate the hardening properties of cemented coal gangue paste backfill (CCGPB) containing high-volume fly ash using macroscopic and microscopic characterization techniques. Specifically, uniaxial compressive strength (UCS) and slump were measured to evaluate the hardening properties of CCGPB, while Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP) were used to characterize the internal microstructure and internal pores. A total of 216 mixture proportions were designed through variations in the contents of cement, fly ash, water, and curing time. The resulting experimental data were used to develop a random forest model. This model was subsequently employed to evaluate the impact of different variables on the development of UCS in CCGPB. The results revealed that the slump increased with increasing fly ash contents and mass concentration. The maximum UCS was achieved at the mass concentration of 0.81 and the fly ash-cement replacement ratio of 0.42, which was also verified by the SEM showing a more compact interfacial transition zone with hydration products of calcium silicate hydrates, calcium aluminosilicate hydrates, and ettringites. The MIP results showed that the addition of fly ash had slight effect on the pores less than 1 μm, while pores larger than 1 μm increased with increasing fly ash content. The porosity ratio decreased by only 4% when fly ash was increased from 30% to 50%. The simulation results by the developed RF model indicated that the curing age had the highest relative importance (47.7%), while the UCS gain was less sensitive to the fly ash content compared with the cement. Overall, this study provides valuable insights into the application of fly ash and coal gangue to cemented paste backfill.

Fresh volcanic aerosols injected in the atmosphere during the volcano eruptive activity at the Cumbre Vieja area (La Palma, Canary Islands): Temporal evolution and vertical impact

For the first time in fifty years, the Cumbre Vieja volcanic area (La Palma, Canary Islands, Spain) erupted on September 19, 2021, giving birth to a new volcano. Fresh volcanic aerosols were continuously injected into the troposphere at different height levels, decreasing with time until the end of December 2021 (15 weeks duration). A wide set of different instrumentation was deployed all over the Island in order to evaluate the effects of the volcanic plumes on the atmosphere and the air quality. For the first time, a long-term study of the relative mass contribution and vertical impact of the volcanic components, ash and non-ash particles separately, during the eruptive activity was carried out in this work. In particular, a polarized Micro-Pulse Lidar (P-MPL) was deployed at Tazacorte (at around 8 km west from the volcano) in 24/7 operation from October 17, 2021 until the end of the volcano activity (11 weeks) for vertical monitoring of the volcanic particles. First, a statistical study of the mass conversion factors for mass concentration estimation of the volcanic (ash and non-ash) particles was performed by using the AERONET sun/sky-photometer dataset at Fuencaliente (at around 18 km south from the volcano). A representative mass conversion factor was obtained for ash and non-ash particles: 1.89 ± 0.53 and 0.31 ± 0.06 g m−2, respectively, with no dependence on time and optical depth. Second, these factors were used to calculate the ash and non-ash mass concentrations from P-MPL observations. Ash particles dominated 11% of the time and mostly until week 3 (i.e. week 7 from the volcanic eruption). Their mass concentration decreased by one order of magnitude: the relative ash mass contribution was 73 ± 18% with a total mass loading of 566 ± 281 mg m−2 at week 1, reducing gradually down to 38 ± 32% and 120 ± 49 mg m−2, respectively, at week 11. Layer-to-layer, it decreased with increasing layer-height; no ash was detected above 4 km at the end of the volcanic period. Third, in order to analyse the potential AERONET underestimation of the coarse mass conversion factor due to the 15 μm cutoff effect in the AERONET retrieval, two worst-case-scenarios (WCS) were examined, representing aged-like ash particles (WCS1, 4-μm radius) and fresh-like (WCS2, 10-μm radius). For both scenarios, the mass concentration of the volcanic plumes exceeded the first contamination level (>200 μg m−3, as defined by the UK Meteorological Office) up to 5–6 km height mostly during week 1 and up to 1–2 km until week 9. The extreme contamination level (>2000 μg m−3, aircraft flight limitations) was only exceeded from week 1 to week 6 under WCS2 conditions. This work infers a new long-term insight on the volcanic matter injected in the atmosphere with relevance for Air Quality issues and air traffic safety policies.

Estimation of the Mass Concentration of Volcanic Ash Using Ceilometers: Study of Fresh and Transported Plumes from La Palma Volcano

This study presents a synergistic approach to the study of the aerosol optical and microphysical properties measured in La Palma, Spain, during the 2021 eruption of the Cumbre Vieja volcano (from 19 September to 13 December 2021). This study aims to characterize the different phases of the volcanic eruption using the spatio-temporal evolution of the event together with the mass concentration quantification of four different atmospheric layers. The impact of the plume’s pathway that reached the South of France is analyzed. Here, passive and active remote sensors were used, namely CL51 and CL61 ceilometers and AERONET sunphotometers. The attenuated backscattering ranged from 0.8 to 9.1 × 10−6 (msr)−1 and the volume depolarization ratio measured nearby the volcano was up to 0.3. The ash plume remained within the first 4 km agl, with intense episodes that reached mean aerosol optical depth values of up to 0.4. Thirteen study cases were selected where coarse mode was dominant over fine mode. For the data selection, the fine and coarse lidar ratios found were 3.9 ± 0.8 and 21.0 ± 3.8 sr in the north and 6.9 ± 1.8 and 30.1 ± 10.3 sr in the south. The ash mass concentration reached moderate levels with maximum values of up to 313.7 μgm−3.

Volcanic Eruption of Cumbre Vieja, La Palma, Spain: A First Insight to the Particulate Matter Injected in the Troposphere

The volcanic eruption of Cumbre Vieja (La Palma Island, Spain), started on 19 September 2021 and was declared terminated on 25 December 2021. A complete set of aerosol measurements were deployed around the volcano within the first month of the eruptive activity. This paper describes the results of the observations made at Tazacorte on the west bank of the island where a polarized micro-pulse lidar was deployed. The analyzed two-and-a-half months (16 October–31 December) reveal that the peak height of the lowermost and strongest volcanic plume did not exceed 3 km (the mean of the hourly values is 1.43 ± 0.45 km over the whole period) and was highly variable. The peak height of the lowermost volcanic plume steadily increased until week 11 after the eruption started (and 3 weeks before its end) and started decreasing afterward. The ash mass concentration was assessed with a method based on the polarization capability of the instrument. Two days with a high ash load were selected: The ash backscatter coefficient, aerosol optical depth, and the volume and particle depolarization ratios were, respectively, 3.6 (2.4) Mm−1sr−1, 0.52 (0.19), 0.13 (0.07) and 0.23 (0.13) on 18 October (15 November). Considering the limitation of current remote sensing techniques to detect large-to-giant particles, the ash mass concentration on the day with the highest ash load (18 October) was estimated to have peaked in the range of 800–3200 μg m−3 in the lowermost layer below 2.5 km.

Characteristics of Particle Size Distributions of Falling Volcanic Ash Measured by Optical Disdrometers at the Sakurajima Volcano, Japan

In the present study, we analyzed the particle size distribution (PSD) of falling volcanic ash particles measured using optical disdrometers during six explosive eruptions of the Sakurajima volcano in Kagoshima Prefecture, Japan. Assuming the gamma PSD model, which is commonly used in radar meteorology, we examined the relationships between each of the gamma PSD parameters (the intercept parameter, the slope parameter, and the shape parameter) calculated by the complete moment method. It was shown that there were good correlations between each of the gamma PSD parameters, which might be one of the characteristics of falling volcanic ash particles. We found from the normalized gamma PSD analysis that the normalized intercept parameter and mass-weighted mean diameter are suitable for estimating the ash fall rate. We also derived empirical power law relationships between pairs of integrated PSD parameters: the ash fall rate, the volcanic ash mass concentration, the reflectivity factor, and the total number of ash particles per unit volume. The results of the present study provide essential information for studying microphysical processes in volcanic ash clouds, developing a method for quantitative ash fall estimation using weather radar, and improving ash transport and sedimentation models.

Dual-Wavelength Polarimetric Lidar Observations of the Volcanic Ash Cloud Produced during the 2016 Etna Eruption

Lidar observations are very useful to analyse dispersed volcanic clouds in the troposphere mainly because of their high range resolution, providing morphological as well as microphysical (size and mass) properties. In this work, we analyse the volcanic cloud of 18 May 2016 at Mt. Etna, in Italy, retrieved by polarimetric dual-wavelength Lidar measurements. We use the AMPLE (Aerosol Multi-Wavelength Polarization Lidar Experiment) system, located in Catania, about 25 km from the Etna summit craters, pointing at a thin volcanic cloud layer, clearly visible and dispersed from the summit craters at the altitude between 2 and 4 km and 6 and 7 km above the sea level. Both the backscattering and linear depolarization profiles at 355 nm (UV, ultraviolet) and 532 nm (VIS, visible) wavelengths, respectively, were obtained using different angles at 20°, 30°, 40° and 90°. The proposed approach inverts the Lidar measurements with a physically based inversion methodology named Volcanic Ash Lidar Retrieval (VALR), based on Maximum-Likelihood (ML). VALRML can provide estimates of volcanic ash mean size and mass concentration at a resolution of few tens of meters. We also compared those results with two methods: Single-variate Regression (SR) and Multi-variate Regression (MR). SR uses the backscattering coefficient or backscattering and depolarization coefficients of one wavelength (UV or VIS in our cases). The MR method uses the backscattering coefficient of both wavelengths (UV and VIS). In absence of in situ airborne validation data, the discrepancy among the different retrieval techniques is estimated with respect to the VALR ML algorithm. The VALR ML analysis provides ash concentrations between about 0.1 μg/m3 and 1 mg/m3 and particle mean sizes of 0.1 μm and 6 μm, respectively. Results show that, for the SR method differences are less than <10%, using the backscattering coefficient only and backscattering and depolarization coefficients. Moreover, we find differences of 20–30% respect to VALR ML, considering well-known parametric retrieval methods. VALR algorithms show how a physics-based inversion approaches can effectively exploit the spectral-polarimetric Lidar AMPLE capability.

CHARACTERIZATION OF SERBIAN SUNFLOWER HONEYS BY THEIR PHYSICOCHEMICAL CHARACTERISTICS

Abstract: Five physicochemical parameters (water content, electrical conductivity, total acidity (pH), ash mass fraction and concentration of free acids) were analyzed in 15 sunflower honeys collected from several localities in Vojvodina, Republic of Serbia. The mean values of analyzed honeys were: water content 16.87%; concentration of free acids 27.43 mEq/kg; electrical conductivity 0.34 mS/cm; pH 3.64. The selected physicochemical characteristics of all honey samples from Serbia analyzed in this research can be considered to be within the parameters expected for sunflower honey in general. The values for ash mass fraction, electrical conductivity and concentration of free acids in all sunflower honey samples showed similar trends. High correlation was established between electrical conductivity and ash mass fraction. Statistically significant difference at p≤0.05 (p=0.017) was established only for average values of free acids concentration between honey samples originating from the localities Kanjiža and Čelarevo. All of the analyzed honeys were found to meet national and European legislation for all investigated parameters. Therefore, further research on physicochemical properties of sunflower honey is required to confirm the quality and authenticity of this product and for better understanding the benefits of this honey.

Karakterizacija srpskog suncokretnog meda na osnovu njegovih fizičko-hemijskih karakteristika

Five physicochemical parameters (water content, electrical conductivity, total acidity (pH), ash mass fraction and concentration of free acids) were analyzed in 15 sunflower honeys collected from several localities in Vojvodina, Serbia. The mean values of analyzed honeys were: water content 16.87%; concentration of free acids 27.43 mEq/kg; electrical conductivity 0.34 mS/cm; pH 3.64 and ash mass fraction 0.13%. The selected physicochemical characteristics of all honey samples from Serbia analyzed in this research can be considered to be within the parameters expected for sunflower honey in general. The values for ash mass fraction, electrical conductivity and concentration of free acids in all sunflower honey samples showed similar trends. High correlation was established between electrical conductivity and ash mass fraction. Statistically significant difference (p≤0.05) was established only for average values of free acids concentration between honey samples originating from the localities Kanjiža and Čelarevo. All of the analyzed honey samples were found to meet national and European legislation for investigated parameters

Multi-Sensor Analysis of a Weak and Long-Lasting Volcanic Plume Emission

Volcanic emissions are a well-known hazard that can have serious impacts on local populations and aviation operations. Whereas several remote sensing observations detect high-intensity explosive eruptions, few studies focus on low intensity and long-lasting volcanic emissions. In this work, we have managed to fully characterize those events by analyzing the volcanic plume produced on the last day of the 2018 Christmas eruption at Mt. Etna, in Italy. We combined data from a visible calibrated camera, a multi-wavelength elastic/Raman Lidar system, from SEVIRI (EUMETSAT-MSG) and MODIS (NASA-Terra/Aqua) satellites and, for the first time, data from an automatic sun-photometer of the aerosol robotic network (AERONET). Results show that the volcanic plume height, ranging between 4.5 and 6 km at the source, decreased by about 0.5 km after 25 km. Moreover, the volcanic plume was detectable by the satellites up to a distance of about 400 km and contained very fine particles with a mean effective radius of about 7 µm. In some time intervals, volcanic ash mass concentration values were around the aviation safety thresholds of 2 × 10−3 g m−3. Of note, Lidar observations show two main stratifications of about 0.25 km, which were not observed at the volcanic source. The presence of the double stratification could have important implications on satellite retrievals, which usually consider only one plume layer. This work gives new details on the main features of volcanic plumes produced during low intensity and long-lasting volcanic plume emissions.

Maximum-Likelihood Retrieval of Volcanic Ash Concentration and Particle Size From Ground-Based Scanning Lidar

An inversion methodology, named maximum-likelihood (ML) volcanic ash light detection and ranging (Lidar) retrieval (VALR-ML), has been developed and applied to estimate volcanic ash particle size and ash mass concentration within volcanic plumes. Both estimations are based on the ML approach, trained by a polarimetric backscattering forward model coupled with a Monte Carlo ash microphysical model. The VALR-ML approach is applied to Lidar backscattering and depolarization profiles, measured at visible wavelength during two eruptions of Mt. Etna, Catania, Italy, in 2010 and 2011. The results are compared with those of ash products derived from other parametric retrieval algorithms. A detailed comparison among these different retrieval techniques highlights the potential of VALR-ML to determine, on the basis of a physically consistent approach, the ash cloud area that must be interdicted to flight operations. Moreover, the results confirm the usefulness of operating scanning Lidars near active volcanic vents.

Combustion quality of poplar and willow clones grown as SRC at four sites in Brandenburg, Germany

The fuel quality was assessed for nine poplar clones (AF2, Androscoggin, Max1, Max3, Max4, Monviso, Muhle-Larsen, NE42, Weser6) and one willow clone (Inger) grown as short rotation coppice (SRC) on four sites in the Brandenburg area in Germany. Fuel quality was analysed in 3-year old shoots in terms of dry matter (DM) mass fraction, total ash mass fraction and concentration of 14 ash-related elements (Al, Ca, Cd, Cl, Cu, Fe, K, Mg, Mn, Na, P, S, Si, Zn). Clone significantly affected DM and ash mass fraction and concentration of 11 of the 14 elements, site affected concentration of 7 elements, and clone and site interacted on DM, ash mass fraction and concentration of 7 elements. Among the poplar clones, Androscoggin and NE42 generally exhibited highest quality with higher DM mass fraction and lower concentrations of ash, Ca, K, P, Cd and Cu than other poplar clones. The willow clone had high DM mass fraction, low ash mass fraction and generally low concentrations of the major ash-forming elements compared to poplar clones. However, willow had significantly higher mean concentration of Cd, Mn and Zn than all poplar clones but with significant clone-site interactions and, on some sites, the concentrations were no higher in willow than in the poplar clones.Shoot diameter significantly affected fuel quality with thin shoots generally having higher ash mass fraction and element concentrations than thicker shoots. In conclusion, fuel quality of SRC biomass may be improved by selecting appropriate clones and by increasing shoot diameter at harvest.

Detection and characterization of volcanic ash plumes over Lille during the Eyjafjallajökull eruption

Abstract. Routine sun-photometer and micro-lidar measurements were performed in Lille, northern France, in April and May 2010 during the Eyjafjallajökull volcanic eruption. The impact of such an eruption emphasized significance of hazards for human activities and importance of observations of the volcanic aerosol particles. This paper presents the main results of a joint micro-lidar/sun-photometer analysis performed in Lille, where volcanic ash plumes were observed during at least 22 days, whenever weather conditions permitted. Aerosol properties retrieved from automatic sun-photometer measurements (AERONET) were strongly changed during the volcanic aerosol plumes transport over Lille. In most cases, the aerosol optical depth (AOD) increased, whereas Ångström exponent decreased, thus indicating coarse-mode dominance in the volume size distribution. Moreover, the non-spherical fraction retrieved by AERONET significantly increased. The real part of the complex refractive index was up to 1.55 at 440 nm during the eruption, compared to background data of about 1.46 before the eruption. Collocated lidar data revealed that several aerosol layers were present between 2 and 5 km, all originating from the Iceland region as confirmed by backward trajectories. The volcanic ash AOD was derived from lidar extinction profiles and sun-photometer AOD, and its maximum was estimated around 0.37 at 532 nm on 18 April 2010. This value was observed at an altitude of 1700 m and corresponds to an ash mass concentration (AMC) slightly higher than 1000 μg m−3 (±50%). An effective lidar ratio of ash particles of 48 sr was retrieved at 532 nm for 17 April during the early stages of the eruption, a value which agrees with several other studies carried out on this topic. Even though the accuracy of the retrievals is not as high as that obtained from reference multiwavelength lidar systems, this study demonstrates the opportunity of micro-lidar and sun-photometer joint data processing for deriving volcanic AMC. It also outlines the fact that a network of combined micro-lidars and sun photometers can be a powerful tool for routine monitoring of aerosols, especially in the case of such hazardous volcanic events.

Monitoring Etna volcanic plumes using a scanning LiDAR

In this paper, we use data obtained from LiDAR measurements during an ash emission event on 15 November 2010 at Mt. Etna, in Italy, in order to evaluate the spatial distribution of volcanic ash in the atmosphere. A scanning LiDAR system, located at 7 km distance from the summit craters, was directed toward the volcanic vents and moved in azimuth and elevation to analyse different volcanic plume sections. During the measurements, ash emission from the North East Crater and high degassing from the Bocca Nuova Crater were clearly visible. From our analysis we were able to: (1) evaluate the region affected by the volcanic plume presence; (2) distinguish volcanic plumes containing spherical aerosols from those having non-spherical ones; and (3) estimate the frequency of volcanic ash emissions. Moreover, the spatial distribution of ash mass concentration was evaluated with an uncertainty of about 50 %. We found that, even during ash emission episodes characterised by low intensity like the 15 November 2010 event, the region in proximity of the summit craters should be avoided by air traffic operations, the ash concentration being greater than 4 × 10−3 g/m3. The use of a scanning permanent LiDAR station may usefully monitor the volcanic activity and help to drastically reduce the risks to aviation operations during the frequent Etna eruptions.

Lidar depolarization measurement of fresh volcanic ash from Mt. Etna, Italy

A small, portable, polarization lidar system with scanning capability was used to perform range resolved measurements of fresh erupted volcanic plume from Mount Etna in Italy. Measurements were carried out on November 15, 2010 during a volcanic plume emission event by placing the lidar very close to volcano summit craters. Depolarization measurements highlighted that aerosol of different shape and optical properties were emitted by the two involved vents, Bocca Nuova and North-East Craters. In the plume emitted from Bocca Nuova Crater the mean value of aerosol linear depolarization ratio resulted near to zero, corresponding to non depolarizing particles or liquid droplets, while values of (16 ± 2)% and (45 ± 3)% were observed in the ash plume emitted from North-East Crater, in the morning and in the afternoon, respectively. The retrieved values of volcanic aerosol depolarization ratio, aerosol backscattering and lidar-ratio allowed distinguishing the changes in the properties of the emitted aerosol. Furthermore, the ash mass concentration at source was estimated, reaching a maximum value of 24,000 ± 6000 μg m−3, with an additional systematic uncertainty of 50% related to the assumption of an effective radius of 10 μm for ash particles.

Volcanic ash over Scandinavia originating from the Grímsvötn eruptions in May 2011

A volcanic ash plume that originated from the eruptions of Iceland's Grímsvötn volcano in May 2011 was observed over the Nordic countries using a combination of satellite observations and ground‐based measurements. The dispersion of the plume was investigated using London VAAC ash forecasts and MODIS observations. Hourly PM10 concentrations at air quality monitoring stations in the southern parts of Norway, Sweden, and Finland exceeded 100 μg/m3 for several hours. The FLEXPART dispersion model has been used to confirm the Icelandic origin of the sampled air masses. Column‐integrated quantities from a Sun photometer and vertical profiles from a Raman lidar were used to estimate the ash concentration within an elevated layer over Stockholm. A lofted layer with an optical thickness of 0.3 at 532 nm passed Stockholm in the morning hours of 25 May 2011. Considering a realistic range of coarse‐mode fractions and specific ash extinctions from the literature, an estimated range of maximum ash mass concentration of 150–340 μg/m3 was derived from the lidar measurements at an altitude of 2.8 km. The lower estimate of the lidar‐derived ash mass concentrations within the planetary boundary layer was found to be in good agreement with surface observations of PM10.

Monitoring of the Eyjafjallajökull volcanic aerosol plume over the Iberian Peninsula by means of four EARLINET lidar stations

Abstract. Lidar and sun-photometer measurements were performed intensively over the Iberian Peninsula (IP) during the eruption of the Eyjafjallajökull volcano (Iceland) in April–May 2010. The volcanic plume reached all the IP stations for the first time on 5 May 2010. A thorough study of the event was conducted for the period 5–8 May. Firstly, the spatial and temporal evolution of the plume was described by means of lidar and sun-photometer measurements supported with backtrajectories. The volcanic aerosol layers observed over the IP were rather thin (<1000 m) with a top height up to 11–12 km. However, in some cases at the beginning of the period the thickness of those layers reached several kilometers in Évora and Madrid. The optical thicknesses associated to those layers were rather low (between 0.013 and 0.020 in average over the whole period), with peak values near 0.10 detected on 7 May. Secondly, the volcanic aerosols were characterized in terms of extinction and backscatter coefficients, lidar ratios, Ångström exponents and linear particle depolarization ratio. Lidar ratios at different sites varied between 30 and 50 sr without a marked spectral dependency. Similar extinction-related Ångström exponents varying between 0.6 and 0.8 were observed at different sites. The temporal evolution of the backscatter-related Ångström exponents points out a possible decrease of the volcanic particle size as the plume moved from west to east. Particle depolarization ratios on the order of 0.06–0.08 confirmed the coexistence of both ash and non-ash particles. Additionally, profiles of mass concentration were obtained with a method using the opposite depolarizing effects of ash particles (strongly depolarizing), non-ash particles (very weakly depolarizing), and sun-photometer observations. In Granada the ash mass concentration was found to be approximately 1.5 times higher than that of non-ash particles, and probably did not exceed the value of 200 μg m−3 during the whole event.

Eyjafjallajökull ash concentrations derived from both lidar and modeling

Following the eruption of the Icelandic volcano Eyjafjallajökull on the 14 April 2010, ground‐based N2‐Raman lidar (GBL) measurements were used to trace the temporal evolution of the ash plume from 16 to 20 April 2010 above the southwestern suburb of Paris. The nighttime overpass of the Cloud‐Aerosol LIdar with Orthogonal Polarization onboard Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite (CALIPSO/CALIOP) on 17 April 2010 was an opportunity to complement GBL observations. The plume shape retrieved from GBL has been used to assess the size range of the particles size. The lidar‐derived aerosol mass concentrations (PM) have been compared with model‐derived PM concentrations held in the Eulerian model Polair3D transport model, driven by a source term inferred from the SEVIRI sensor onboard Meteosat satellite. The consistency between model and ground‐based wind lidar and CALIOP observations has been checked. The spatial and temporal structures of the ash plume as estimated by each instrument and by the Polair3D simulations are in agreement. The ash plume was associated with a mean aerosol optical thickness of 0.1 ± 0.06 and 0.055 ± 0.053 for GBL (355 nm) and CALIOP (532 nm), respectively. Such values correspond to ash mass concentrations of ∼400 ± 160 and ∼720 ± 670 μg m−3, respectively, within the ash plume, which was lower than 0.5 km in width. The relative uncertainty is ∼75% and mainly due to the assessment of the specific cross‐section assuming an aerosol density of 2.6 g cm−3. The simulated ash plume is smoother leading to integrated mass of the same order of magnitude (between 50 and 250 mg m−2).