ALBERT

Description: Explosive volcanic eruptions can produce vast amounts of volcanic ash made up mainly of fragments of magmatic glass, country rock and minerals 〈 2 mm in size. Ash particles forming from magma fragmentation are generated by several processes when brittle response accommodates (local) deformation stress that exceeds the capability of the bulk material to respond by viscous flow. These processes span a wide range of temperatures, can occur inside or outside the volcanic edifice and can involve all melt compositions. Ash is then dispersed by volcanic and atmospheric processes over large distances and can have global distributions. Explosive eruptions have repeatedly drawn focus to studying volcanic ash. The continued occurrence of such eruptions worldwide and their widespread impacts motivates the study of the chemical and physical processes involved in the lifecycle of volcanic ash (e.g. magma fragmentation, particle aggregation), as well as the immediate to long-term effects (e.g. water and air pollution, soil fertilization) and consequences (e.g. environmental, economic, social) associated with ashfall. In this perspectives article, we reflect on the progress made over the last two decades in understanding (1) volcanic ash generation; (2) dispersion, sedimentation and erosion; and (3) impacts on the atmosphere, hydrosphere, biosphere and modern infrastructure. Finally, we discuss open questions and future challenges.

Description: Published

Description: 51

Description: 5V. Processi eruttivi e post-eruttivi

Description: JCR Journal

Description: We present a new aerosol extinction profile retrieval algorithm for multi-axis differential optical absorption spectrometer (MAX-DOAS) measurements at high-altitude sites. The algorithm is based on the lookup table method. It is applied to retrieve aerosol extinction profiles from the long-term MAX-DOAS measurements (February 2012 to February 2016) at the Environmental Research Station Schneefernerhaus (UFS), Germany (47.417∘ N, 10.980∘ E), which is located near the summit of Zugspitze at an altitude of 2650 m. The lookup table consists of simulated O4 differential slant column densities (DSCDs) corresponding to numerous possible aerosol extinction profiles. The sensitivities of O4 absorption to several parameters were investigated for the design and parameterization of the lookup table. In the retrieval, simulated O4 DSCDs for each possible profile are derived by interpolating the lookup table to the observation geometries. The cost functions are calculated for each aerosol profile in the lookup table based on the simulated O4 DSCDs, the O4 DSCD observations, and the measurement uncertainties. Valid profiles are selected from all the possible profiles according to the cost function, and the optimal solution is defined as the weighted mean of all the valid profiles. A comprehensive error analysis is performed to better estimate the total uncertainty. Based on the assumption that the lookup table covers all possible profiles under clear-sky conditions, we determined a set of O4 DSCD scaling factors for different elevation angles and wavelengths. The profiles retrieved from synthetic measurement data can reproduce the synthetic profile. The results also show that the retrieval is insensitive to measurement noise, indicating the retrieval is robust and stable. The aerosol optical depths (AODs) retrieved from the long-term measurements were compared to coinciding and co-located sun photometer observations. High correlation coefficients (R) of 0.733 and 0.798 are found for measurements at 360 and 477 nm, respectively. However, especially in summer, the sun photometer AODs are systematically higher than the MAX-DOAS retrievals by a factor of ∼2. The discrepancy might be related to the limited measurement range of the MAX-DOAS and is probably also related to the decreased sensitivity of the MAX-DOAS measurements at higher altitudes. The MAX-DOAS measurements indicate the aerosol extinction decreases with increasing altitude during all seasons, which agrees with the co-located ceilometer measurements. Our results also show maximum AOD and maximum Ångström exponent in summer, which is consistent with observations at an AERONET station located ∼43 km from the UFS.

Description: In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97∘ N, 4.93∘ E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation. The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions. The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques.

Description: We present a new total column water vapor (TCWV) retrieval algorithm in the visible blue spectral band for the Global Ozone Monitoring Experience 2 (GOME-2) instruments on board the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Metop satellites. The blue band algorithm allows the retrieval of water vapor from sensors which do not cover longer wavelengths, such as the Ozone Monitoring Instrument (OMI) and the Copernicus atmospheric composition missions Sentinel-5 Precursor (S5P), Sentinel-4 (S4) and Sentinel-5 (S5). The blue band algorithm uses the differential optical absorption spectroscopic (DOAS) technique to retrieve water vapor slant columns. The measured water vapor slant columns are converted to vertical columns using air mass factors (AMFs). The new algorithm has an iterative optimization module to dynamically find the optimal a priori water vapor profile. This makes it better suited for climate studies than usual satellite retrievals with static a priori or vertical profile information from the chemistry transport model (CTM). The dynamic a priori algorithm makes use of the fact that the vertical distribution of water vapor is strongly correlated to the total column. The new algorithm is applied to GOME-2A and GOME-2B observations to retrieve TCWV. The data set is validated by comparing it to the operational product retrieved in the red spectral band, sun photometer and radiosonde measurements. Water vapor columns retrieved in the blue band are in good agreement with the other data sets, indicating that the new algorithm derives precise results and can be used for the current and forthcoming Copernicus Sentinel missions S4 and S5.

Description: We present two-dimensional scanning Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of nitrogen dioxide (NO2) and formaldehyde (HCHO) in Munich. Vertical columns and vertical distribution profiles of aerosol extinction coefficient, NO2 and HCHO are retrieved from the 2D MAX-DOAS observations. The measured surface aerosol extinction coefficients and NO2 mixing ratios derived from the retrieved profiles are compared to in situ monitoring data, and the surface NO2 mixing ratios show a good agreement with in situ monitoring data with a Pearson correlation coefficient (R) of 0.91. The aerosol optical depths (AODs) show good agreement as well (R = 0.80) when compared to sun photometer measurements. Tropospheric vertical column densities (VCDs) of NO2 and HCHO derived from the MAX-DOAS measurements are also used to validate Ozone Monitoring Instrument (OMI) and TROPOspheric Monitoring Instrument (TROPOMI) satellite observations. Monthly averaged data show a good correlation; however, satellite observations are on average 30 % lower than the MAX-DOAS measurements. Furthermore, the MAX-DOAS observations are used to investigate the spatiotemporal characteristic of NO2 and HCHO in Munich. Analysis of the relations between aerosol, NO2 and HCHO shows higher aerosol-to-HCHO ratios in winter, which reflects a longer atmospheric lifetime of secondary aerosol and HCHO during winter. The analysis also suggests that secondary aerosol formation is the major source of these aerosols in Munich.

Description: Introduction: Non-transfusion dependent thalassemia (NTDT) includes HbH disease, β-thalassemia intermedia (β-TI) and HbE/β-thalassemia. The transfusion requirements of patients with NTDT are variable and they are all at risk of developing iron overload and other complications. The prevalent genetic changes in thalassemia are different across geographical territories, accounting largely for the diverse clinical outcomes. The complication profile of NTDT in Southern China is less well studied than other areas. Data on age-related complications is sparse. The present study aims to describe the clinical-pathological features of adult NTDT patients in Hong Kong, and to evaluate the risk factors associated with complications. Method: A single-center observational study was performed during Jan 2017 to Jun 2018. Data collection included review of medical records for demographics; globin genotypes; hepatitis B and C status; transfusion requirement; splenectomy; iron chelation therapy; complications including gallstone disease, hypothyroidism or hypogonadism, diabetes mellitus (DM), extramedullary hematopoiesis (EMH), leg ulcer, venous thrombosis and cerebral ischemia. During the study period, steady state hemoglobin (Hb) and serum ferritin levels in the recent year were obtained; organ iron deposition assessed using liver and cardiac T2* at 1.5T MRI; liver stiffness measured by Fibroscan; and presence of pulmonary arterial hypertension (PAH) evaluated by echocardiography. The disease profile and prevalence of complications were described with descriptive statistics. Factors impacting clinical parameters and development of complication were studied with univariate regressions. Age and sex adjusted β-coefficients or odd ratios were then determined with multivariable regression analysis. Results: A total of 96 Chinese patients were recruited (mean age 50±15 years; 31% patients 〉60 years; females 66%). There were 63 (65%) patients having deletional HbH disease, 20 (21%) with non-deletional HbH disease (ND-HbHD), and 13 (14%) with β-TI. The mean Hb was 8.9±1.1 g/dL. Transfusion requirement was never in 39 (41%), occasional in 50 (52%), and regular in 7 (7%) patients. Ten (10%) patients were splenectomized. Iron chelation was given to 21 (21%) patients and the median duration of therapy was 3 (range 1-21) years. Respectively 4 (4%) and 2 (2%) patients were hepatitis B and C carriers. The median serum ferritin was 473 [IQR 217-1029] ng/mL. The median liver iron concentration (LIC) estimated by MRI T2* was 3.6 [IQR 1.7-7.1] mg Fe/g with 26% of patients having moderate to severe liver iron overload (≥7.1 Fe mg/g). In the study population, the prevalence of liver fibrosis (liver stiffness ≥7.1kPa) was 26%, gallstones 50%, hypo-thyroidism/-gonadism 8%, DM 16%, EMH 5%, leg ulcer 1%, thrombotic events 2%, cardiac iron overload 1%. No patients had PAH (Table 1). In multivariable regression, advanced age (〉60 years) was associated with lower Hb (p=0.03), higher risk of liver fibrosis (p=0.04) and DM (p

Description: Introduction Patient blood management was developed to reduce allogeneic blood exposure and enhance patient outcomes. If transfusion is required in stable and non-bleeding hospitalized patients, prescribing one unit of red blood cells (RBC) followed by reassessment of clinical condition is recommended. Double-unit RBC transfusion, the routine practice in the past, is still widely practiced despite the advocate of restrictive transfusion strategy. One of the reasons could be a lack of evidence to support the optimal number of RBC units per transfusion. Blood transfusion is often performed to alleviate anemic symptoms. However, patient-reported outcomes were seldom measured to evaluate transfusion requirements. Method This was a single-center prospective study conducted during Mar to Jun 2016 in the medical department of a regional hospital of Hong Kong. Day-care and hospitalized patients requiring RBC transfusion were recruited. Patients with active bleeding or unstable hemodynamics were excluded. Subjects' demographics, recent transfusion history, comorbidities, transfusion trigger and the number of RBC units transfused were obtained. Patient-reported outcomes were measured on the day of transfusion (Day 0), and on Day 1 and 7 post-transfusion. Two health-related quality of life (HRQOL) instruments, i.e. Short-form 12 version 2 (SF12v2) and Functional Assessment of Cancer Therapy Anemia Subscale (FACT-AnS) in traditional Chinese, were administered to measure the general health status and anemic symptoms respectively. Physical Component Summary (PCS) and Mental Component Summary (MCS) scores were then derived from SF12v2. The number of RBC units transfused in one week and post-transfusion hemoglobin (Hb) level were evaluated. Linear regressions were performed to study the relationship between the changes in PCS, MCS and FACT-AnS on Day 1 and Day 7 from Day 0 with the number of RBC units transfused. Factors associated with the number of RBC units transfused were controlled. Other predictors of the changes in HRQOL were included in the regression analysis. Results 34 day-care and 67 hospitalized patients were recruited with HRQOL surveys completed on Day 0. The surveys were completed by 97 patients on Day 1 and 78 patients on Day 7. Forty-seven patients (47%), who were transfused with 2 or more units of RBC, were classified as double-unit group. The median transfusion trigger was 7.6 [IQR 7.0 - 7.9] g/dL in the single-unit group and 7.0 [IQR 6.2 - 7.8] g/dL in the double-unit group (p 〈 0.05). There was a trend of higher Charlson's Comorbidity Index (CCI) (p = 0.09) in the single-unit group. Baseline PCS, MCS and FACT-AnS scores on Day 0 were comparable in both groups (p = 0.35, 0.45 and 0.15 respectively). The changes in HRQOL of all subjects were summarized in Table 1. FACIT-AnS improved after transfusion but the effect size was small (Cohen's d 〈 0.5). There was improvement of PCS on Day 7. The change of MCS was non-significant. The mean number of transfused RBC in one week was 0.7 units less in the single-unit group (p 〈 0.001). The post-transfusion Hb level was 0.9g/dL (95% CI: 0.3, 1.6) and 1.1g/dL (95% CI: 0.2, 1.9) higher in the double-unit group on Day 1 and Day 7 respectively. Having controlled for transfusion trigger, CCI and RBC transfused during Day 1 to Day 7, the changes in HRQOL were not associated with the number of RBC units transfused (Table 2). Day-care patients had greater improvement in HRQOL on Day 1 but not on Day 7. The improvement of HRQOL in those having worse baseline scores was more significant. RBC use in the past 7 days was not associated with the change in patient-reported outcomes. Conclusion Double-unit RBC transfusion was frequently performed, especially in patients with a lower Hb level. Blood transfusion could improve anemic symptoms but the effect on general health status was insignificant during early follow-up. The average number of RBC units transfused in one week was 28% less in the single-unit group. Post-transfusion Hb level was higher after double-unit transfusion, but there was no evidence it led to more significant improvement in patient-reported outcomes. Day-care patients had earlier improvement in HRQOL but the effect disappeared after one week. Patients with worse symptom score at baseline had greater improvement in HRQOL. It is proposed that the practice of single-unit RBC transfusion is appropriate in terms of alleviating anemic symptoms and reducing overall blood use. Disclosures No relevant conflicts of interest to declare.