68 research outputs found
Rapid Primary Sulfate Aerosol Generation Observed With OPâFTIR in the Eruptive Plume of the Fagradalsfjall Basaltic Eruption, Iceland, 2021
OpenâPath FourierâTransform Infrared (OPâFTIR) absorption spectroscopy is a powerful method for remote characterization of volcanic plume composition from safe distances. Many studies have used it to examine the composition of volcanic gas emitted at the surface, which is influenced by initial volatile contents and magma ascent/storage processes, and help to reveal the dynamics controlling surface activity. However, to evaluate the health hazard threats associated with volcanic emissions and their potential impact on wider atmospheric conditions, nearâsource particle measurements are also key. Here we present a forward model and fitting algorithm which allows quantification of particle size and abundance. This was successfully applied to radiometrically uncalibrated OPâFTIR spectra collected with a highly dynamic radiation source during the Fagradalsfjall eruption, Iceland, on 11 August 2021. Quantification of plume temperatures ranging from 350 to 650 K was essential to characterize the emissionâabsorption behavior of SO2, enabling retrievals of particulate matter in the thermal infrared spectral window (750â1250 cmâ1) in each spectrum. For the first time, we observe the rapid formation of primary aerosols in young plumes (only a few seconds old) with OPâFTIR. Temperatureâdependent SO2/SO42â molar ratios range from 100 to 250, consistent with a primary formation mechanism controlled by cooling and entrainment of atmospheric gases. This novel aerosol spectrum retrieval opens new frontiers in fieldâbased measurements of sulfur partitioning and volcanic plume evolution, with the potential to improve volcano monitoring and quantification of air quality hazard assessments
Quantification of gas, ash, and sulphate aerosols in volcanic plumes from open path Fourier transform infrared (OP-FTIR) emission measurements at Stromboli volcano, Italy
Field-portable Open Path Fourier Transform Infrared (OP-FTIR) spectrometers can be used to remotely measure the composition of volcanic plumes using absorption spectroscopy, providing invaluable data on total gas emissions. Quantifying the temporal evolution of gas compositions during an eruption helps develop models of volcanic processes and aids in eruption forecasting. Absorption measurements require a viewing geometry which aligns infrared source, plume, and instrument, which can be challenging. Here, we present a fast retrieval algorithm to estimate quantities of gas, ash and sulphate aerosols from thermal emission OP-FTIR measurements, and the results from two pilot campaigns on Stromboli volcano in Italy in 2019 and 2021. We validate the method by comparing time series of SO2 slant column densities retrieved using our method with those obtained from a conventional UV spectrometer, demonstrating that the two methods generally agree to within a factor of 2. The algorithm correctly identifies ash-rich plumes and gas bursts associated with explosions and quantifies the mass column densities and particle sizes of ash and sulphate aerosols (SA) in the plume. We compare the ash sizes retrieved using our method with the particle size distribution (PSD) of an ash sample collected during the period of measurements in 2019 by flying a Remotely Piloted Aircraft System into the path of a drifting ash plume and find that both modes of the bimodal PSD (a fine fraction with diameter around 5â10Â ÎŒm and a coarse fraction around 65Â ÎŒm) are identified within our datasets at different times. We measure a decrease in the retrieved ash particle size with distance downwind, consistent with settling of larger particles, which we also observed visually. We measure a decrease in the SO2/SA ratio as the plume travels downwind, coupled with an increase in measured SA particle size (range 2â6Â ÎŒm), suggesting rapid hygroscopic particle growth and/or SO2 oxidation. We propose that infrared emission spectroscopy can be used to examine physical and chemical changes during plume transport and opens the possibility of remote night-time monitoring of volcanic plume emissions. These ground-based analyses may also aid the refinement of satellite-based aerosol retrievals
Awareness of vitamin D deficiency among at-risk patients
<p>Abstract</p> <p>Background</p> <p>Vitamin D deficiency is a significant problem for a growing proportion of the UK population. Individuals with dark or covered skin are at particularly high risk due to ethno-cultural, environmental and genetic factors. We assessed the level of awareness of vitamin D deficiency among at-risk patients in order to identify groups most in need of education.</p> <p>Findings</p> <p>A cross-sectional survey using a piloted questionnaire was conducted among consecutive at-risk patients without a diagnosis of Vitamin D deficiency arriving at a large inner city general practice in the North West of England over a five day period. The survey was completed by 221 patients. The mean age was 35 years. 28% of them (n = 61) had never heard about vitamin D. Older patients (p = 0.003) were less likely to have heard about vitamin D. 54% of participants were unaware of the commonest symptoms of vitamin D deficiency. 34% did not expose their skin other than their face in the last one year, and 11% did not include vitamin D rich foods in their diet.</p> <p>Conclusion</p> <p>The majority of at-risk patients are aware of vitamin D; nevertheless, there is a significant lack of knowledge among older people, who have higher morbidity. A programme of targeted education of the at-risk population is recommended.</p
Viability of Staphylococcus xylosus during shelf-life of dulce de leche prepared by vacuum evaporation
Inactivation of Staphylococcus aureus and Salmonella enteritidis in tryptic soy broth and caviar samples by high pressure processing
Avaliação da qualidade tecnolĂłgica de envoltĂłrio natural suĂno utilizado no processamento de lingĂŒiça Toscana
Development of a new assessment scale for measuring interaction during staff-assisted transfer of residents in dementia special care units
Enzymatic activity of proteases and its isoenzymes in fermentation process in cultivars of cocoa (Theobroma cacao L.) produced in southern Bahia, Brazil
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