30,569 research outputs found

    Contribution of coal combustion to black carbon: coupling tracers with the aethalometer model

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    Black carbon (BC) aerosol characteristics have been analysed from January 2016 to March 2017 in an urban background area (León, Spain), located in a coal-mining region, where this fuel is commonly used. The monthly and seasonal variations of BC and source contributions were examined. The mean equivalent BC concentration (eBC) during cold and warm months were 1.0±0.5 and 0.6±0.2 μg m-3, respectively. eBC can be further divided into eBCff (eBC from liquid fossil fuel) and eBCbb+cc (eBC from biomass burning plus coal combustion), with mean annual values of 0.6±0.3 and 0.3±0.3 μg m 3 (cold months) and 0.4±0.2 μg m 3 and 0.1±0.1 μg m 3 (warm months), respectively. The eBC obtained from the aethalometer and the elemental carbon (EC) quantified through a Thermal Optical Transmittance method presented a significant strong positive correlation in both warm (r=0.82) and cold (r=0.88) periods. A mass absorption cross-section (MAC) of 4.46±0.16 between two techniques has been obtained. In the cold period, a multilinear regression model to decouple eBCbb from eBCcc was established (r2=0.85) based on two tracers: arsenic for coal combustion and potassium for biomass burning. The model application enabled us to distinguish the contributions to eBCbb+cc (as a function of the variance explained by the tracers) in the cold period: 74% from biomass burning and 26% from coal combustion. The highest eBCcc concentration was estimated for December 2016 and January 2017 (0.18 μg m 3). This result was supported by the Absorption Ångström Exponent (AAE), which showed the maximum value in January 2017 (1.43±0.37) due to the high biomass burning and coal combustion contributions.publishe

    Development of novel high-resolution instruments to measure the real-time oxidative potential of ambient particulate matter and their application in source apportionment

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    Exposure to ambient particulate matter (PM) is known to have an adverse effect on human health. One hypothesized mechanism by which PM affects human health is by inducing an oxidative stress, leading to cell damage. Measuring this oxidative stress induced by ambient PM would help find a better association between PM and its health impacts, than the commonly used PM mass concentrations. Conventional oxidative potential (OP) measurement protocols involve measuring the rate of reactive oxygen species (ROS) generation or antioxidant consumption using either cellular or acellular assays. OP measurements are generally performed on PM samples collected using offline filters followed by extraction in a suitable solvent. However, this approach has several shortcomings; for instance, filter-based PM sampling involves long sampling hours and is prone to sampling artifacts, especially when measuring the reactive components in the ambient air. Additionally, due to the long sampling duration, filter-based sampling cannot capture the temporal variations in the PM chemical characteristics and sources, which could significantly alter the OP of the PM. In this study, we designed and developed a new real-time automated instrument that can measure the OP of ambient PM based on multiple acellular assays. The real-time instrument consists of a glass mist chamber (MC) particle into liquid sampler that collects PM2.5 (PM with diameter < 2.5 um) directly into a liquid solution. We used an automated syringe pump system, connected to a spectrophotometer and/or a spectrofluorometer, to measure the OP of the collected PM2.5 sample. The instrument can measure the OP based on the dithiothreitol assay (DTT) and surrogate lung fluid (SLF; a mixture of four antioxidants: ascorbic acid (AA) + glutathione (GSH), uric acid, and citric acid). OP is reported as the rate of consumption of DTT (OPDTT), AA(OPAA), GSH (OPGSH), and rate of hydroxyl radical generation in DTT (OPDTT-OH) and SLF (OPSLF-OH). This instrument can be operated in either single endpoint mode (only OPDTT, time resolution = 1h) or five endpoint mode (time resolution = 3h). This instrument was used in field campaigns in Champaign, Illinois (a small city), and Delhi, India (a highly polluted megacity). For the first time, we report the diurnal OP profile and PM2.5 sources driving the OP in these cities. Source apportionment analysis revealed, secondary aerosols, traffic, industry, and biomass burning were the important PM2.5 sources driving the OP. Using this instrument, we captured the effect of short-duration episodic pollution events like fireworks emissions (Diwali festival and fourth of July) and investigated how it influenced the OP. Finally, we performed an intercomparison of the real-time OP measured based on the five different endpoints and found a poor correlation among the various endpoints. These results suggest that a single OP endpoint probably does not represent the entire OP. Multiple endpoints need to be evaluated together to account for the varying contribution from the diverse redox-active components in PM2.5. The findings from this study demonstrate the usefulness of obtaining highly time resolved PM2.5 OP data to comprehend various emission sources and their relative importance in assessing the risk from PM2.5 exposure.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    Changes in soil fertility and microbial communities following cultivation of native grassland in Horqin Sandy Land, China: a 60-year chronosequence

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    Background: Grassland conversion to cropland is a prevailing change of land use in traditionally nomadic areas, especially in the Mongolian Plateau. We investigated the effects of grassland conversion followed by continuous cultivation on soil properties and microbial community characteristics in Horqin Sandy Land, a typical agro-pastoral transition zone of Northern China. Soil samples were collected from the topsoil (upper 20 cm) across a 60-year cultivation chronosequence (5, 15, 25, 35 and 60 years) and unconverted native grassland. Soil physico-chemical properties were determined and high-throughput sequencing was used to assess microbial community diversity and composition. Results: Grassland cultivation resulted in changes to soil properties in both the short and longer term. Initially, it significantly increased soil bulk density (BD), electrical conductivity (EC), soil total nitrogen (TN), available phosphorus (AP) and available potassium (AK) concentrations, while reducing soil water content (SWC) and soil organic carbon content (SOC). Over the next 35–55 years of continuous cultivation, the trend for most of these characteristics was of reversion towards values nearer to those of native grassland, except for SOC which remained highly depleted. Cultivation of grassland substantially altered soil microbial communities at phylum level but there was no significant difference in microbial α-diversity between native grassland and any cropland. However, soil bacterial and fungal community structures at phylum level in the croplands of all cultivation years were different from those in the native grasslands. Heatmaps further revealed that bacterial and fungal structures in cropland tended to become more similar to native grassland after 15 and 25 years of cultivation, respectively. Redundancy analysis indicated that SOC, EC and BD were primary determinants of microbial community composition and diversity. Conclusions: These findings suggest that agricultural cultivation of grassland has considerable effects on soil fertility and microbial characteristics of Horqin Sandy Land. Intensive high-yield forage grass production is proposed as an alternative to avoid further native grassland reclamation, while meeting the grazing development needs in the ethnic minority settlements of eco-fragile regions

    Effects of COVID‐19 lockdown measures on nitrogen dioxide and black carbon concentrations close to a major Italian motorway

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    Abstract During the first half of 2020, the Italian government imposed several restrictions to limit the spread of the COVID‐19 pandemic: at the beginning of March, a heavy lockdown regime was introduced leading to a drastic reduction of traffic and, consequently, traffic‐related emissions. The aim of this study is to evaluate the effects of these restrictions on pollutant concentrations close to a stretch of the Italian A22 motorway lying in the Alpine Adige valley. In particular, the analysis focuses on measured concentrations of nitrogen dioxide (NO2) and black carbon (BC). Results show that, close to the motorway, NO2 concentrations dropped by around 45% during the lockdown period with respect to the same time period of the previous 3 years. The equivalent analysis for BC shows that the component related to biomass burning, mostly due to domestic heating, was not particularly affected by the restrictions, while the BC component related to fossil fuels, directly connected to traffic, plummeted by almost 60% with respect to the previous years. Since atmospheric concentrations of pollutants depend both on emissions and meteorological conditions, which can mask the variations in the emission regime, a random forest algorithm is also applied to the measured concentrations, in order to better evaluate the effects of the restrictions on emissions. This procedure allows for obtaining business‐as‐usual and meteorologically normalized time series of both NO2 and BC concentrations. The results derived from the random forest algorithm clearly confirm the drop in NO2 emissions at the beginning of the lockdown period, followed by a slow and partial recovery in the following months. They also confirm that, during the lockdown, emissions of the BC component due to biomass burning were not significantly affected, while those of the BC component related to fossil fuels underwent an abrupt drop

    Preparation of gelatin from broiler chicken stomach collagen

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    With the increasing consumption of poultry meat around the world, the use of chicken stomachs as a source of collagen is being offered. The objective of this study was to extract gelatin from the stomachs of broiler chickens and to estimate their gel strength, ash content, viscosity, gelling point, melting point, clarity and digestibility. An innovative biotechnological method based on the conditioning of collagen with a microbial endoproteinase (Protamex®) and hot-water extraction was used to control the chemical and thermal denaturation process of collagen to prepare gelatin. The experiments were planned using a Taguchi design, 2 factors at 3 levels; factor A for the amount of proteolytic enzyme (0.10, 0.15 and 0.20%) and factor B for the extraction temperature (55.0, 62.5 and 70.0 °C). Data were statistically processed and analyzed at a significance level of 95%. The gelatin yield averaged 65 ± 8%; the gel strength ranged from 25 ± 1 to 439 ± 6 Bloom, the viscosity from 1.0 ± 0.4 to 3.40 ± 0.03 mPa·s, gelling point from 14.0 ± 2.0 to 22.0 ± 2.0 °C, melting point from 28.0 ± 1.0 to 37.0 ± 1.0 °C. The digestibility of gelatin was 100.0% in all samples; the ash content was very low (0.44 ± 0.02–0.81 ± 0.02%). The optimal conditions for the enzymatic treatment of collagen from chicken stomachs were achieved at a higher temperature (70.0 °C) and a lower amount of enzyme (0.10–0.15%). Conditioning chicken collagen with a microbial endoproteinase is an economically and environmentally friendly processing method, an alternative to the usual acid- or alkaline-based treatment that is used industrially. The extracted products can be used for food and pharmaceutical applications. © 2022 by the authors.Univerzita Tomáše Bati ve Zlíně: IGA/FT/2022/00

    Insights into the single-particle composition, size, mixing state, and aspect ratio of freshly emitted mineral dust from field measurements in the Moroccan Sahara using electron microscopy

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    The chemical and morphological properties of mineral dust aerosols emitted by wind erosion from arid and semi-arid regions influence climate, ocean, and land ecosystems; air quality; and multiple socio-economic sectors. However, there is an incomplete understanding of the emitted dust particle size distribution (PSD) in terms of its constituent minerals that typically result from the fragmentation of soil aggregates during wind erosion. The emitted dust PSD affects the duration of particle transport and thus each mineral's global distribution, along with its specific effect upon climate. This lack of understanding is largely due to the scarcity of relevant in situ measurements in dust sources. To advance our understanding of the physicochemical properties of the emitted dust PSD, we present insights into the elemental composition and morphology of individual dust particles collected during the FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT) field campaign in the Moroccan Sahara in September 2019. We analyzed more than 300 000 freshly emitted individual particles by performing offline analysis in the laboratory using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX). Eight major particle-type classes were identified with clay minerals making up the majority of the analyzed particles both by number and mass, followed by quartz, whereas carbonates and feldspar contributed to a lesser extent. We provide an exhaustive analysis of the PSD and potential mixing state of different particle types, focusing largely on iron-rich (Fe oxide-hydroxides) and feldspar particles, which are key to the effects of dust upon radiation and clouds, respectively. Nearly pure or externally mixed Fe oxide-hydroxides are present mostly in diameters smaller than 2 µm, with the highest fraction below 1 µm at about 3.75 % abundance by mass. Fe oxide-hydroxides tend to be increasingly internally mixed with other minerals, especially clays, as particle size increases; i.e., the volume fraction of Fe oxide-hydroxides in aggregates decreases with particle size. Pure (externally mixed) feldspar represented 3.2 % of all the particles by mass, of which we estimated about a 10th to be K-feldspar. The externally mixed total feldspar and K-feldspar abundances are relatively invariant with particle size, in contrast to the increasing abundance of feldspar-like (internally mixed) aggregates with particle size with mass fractions ranging from 5 % to 18 %. We also found that overall the median aspect ratio is rather constant across particle size and mineral groups, although we obtain slightly higher aspect ratios for internally mixed particles. The detailed information on the composition of freshly emitted individual dust particles and quantitative analysis of their mixing state presented here can be used to constrain climate models including mineral species in their representation of the dust cycle.</p

    Microbial Mitigation of Drought Stress in Plants: Adaptations to Climate Change

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    The global temperature is constantly increasing due to the phenomenon of climate change. Plants have developed various mechanisms to defend themselves against environmental stresses including drought stress. Apart from indigenous biochemical, physiological, and molecular mechanisms of adaptation to stress, the plant-associated microbes may also play a crucial role in plant drought tolerance. The endophytic and rhizospheric microbes perform various functions and produce different enzymes and compounds that play an important role in plants’ adaptation to various environmental stresses including drought stress. Some of the key mechanisms include production of growth hormones, siderophores, organic acids, induction of the ROS scavenging system, phosphate solubilization, and nitrogen fixation. However, the production of ACC deaminase in the plant-associated microbes has vital roles in reduction of ethylene levels under drought stress, resulting in improved plant growth and stress tolerance. Owing to the complex nature of drought tolerance, a multi-pronged approach would have to be adapted to further enhance the microbial-mediated drought tolerance in plants

    Anuário científico da Escola Superior de Tecnologia da Saúde de Lisboa - 2021

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    É com grande prazer que apresentamos a mais recente edição (a 11.ª) do Anuário Científico da Escola Superior de Tecnologia da Saúde de Lisboa. Como instituição de ensino superior, temos o compromisso de promover e incentivar a pesquisa científica em todas as áreas do conhecimento que contemplam a nossa missão. Esta publicação tem como objetivo divulgar toda a produção científica desenvolvida pelos Professores, Investigadores, Estudantes e Pessoal não Docente da ESTeSL durante 2021. Este Anuário é, assim, o reflexo do trabalho árduo e dedicado da nossa comunidade, que se empenhou na produção de conteúdo científico de elevada qualidade e partilhada com a Sociedade na forma de livros, capítulos de livros, artigos publicados em revistas nacionais e internacionais, resumos de comunicações orais e pósteres, bem como resultado dos trabalhos de 1º e 2º ciclo. Com isto, o conteúdo desta publicação abrange uma ampla variedade de tópicos, desde temas mais fundamentais até estudos de aplicação prática em contextos específicos de Saúde, refletindo desta forma a pluralidade e diversidade de áreas que definem, e tornam única, a ESTeSL. Acreditamos que a investigação e pesquisa científica é um eixo fundamental para o desenvolvimento da sociedade e é por isso que incentivamos os nossos estudantes a envolverem-se em atividades de pesquisa e prática baseada na evidência desde o início dos seus estudos na ESTeSL. Esta publicação é um exemplo do sucesso desses esforços, sendo a maior de sempre, o que faz com que estejamos muito orgulhosos em partilhar os resultados e descobertas dos nossos investigadores com a comunidade científica e o público em geral. Esperamos que este Anuário inspire e motive outros estudantes, profissionais de saúde, professores e outros colaboradores a continuarem a explorar novas ideias e contribuir para o avanço da ciência e da tecnologia no corpo de conhecimento próprio das áreas que compõe a ESTeSL. Agradecemos a todos os envolvidos na produção deste anuário e desejamos uma leitura inspiradora e agradável.info:eu-repo/semantics/publishedVersio

    A critical review of the production of hydroxyaromatic carboxylic acids as a sustainable method for chemical utilisation and fixation of CO2

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    Hydroxyaromatic carboxylic acids (HACAs) such as salicylic acids, hydroxynaphthoic acids and their halogenated derivatives are essential feedstocks for the pharmaceutical, dye, fragrance, cosmetic and food industries. Large-scale production of HACAs is currently based on the Kolbe–Schmitt reaction between CO2 and petroleum-based phenolic compounds. This batch reaction is carried out at ∼125 °C, ∼85 bar and reaction times of up to 18 hours to achieve high conversions (≈99%). The long reaction times and dependence on fossil-derived phenols have negative sustainability implications. However, as a CO2-based process, HACA production has the potential for large-volume anthropogenic CO2 sequestration and contributes to net zero. A big challenge is that the current global production capacity of HACAs uses only about 41 450 tonnes per year of CO2 which is just ≈0.00012% of the annual anthropogenic emissions. Therefore, significant efforts are needed to increase both the sustainable production and demand for such CO2-based products to enhance their economic and environmental sustainability. This review covers the basic kinetic and thermodynamic stability of CO2. Thereafter, a comprehensive coverage of early and current developments to improve the carboxylation of phenols to make HACAs is given, while discussing their industrial potential. Moreover, it covers new propositions to use biomass-derived phenolic compounds for sustainable production of HACAs. There is also a need to expand the uses and applications of HACAs and recent reports on the production of HACA-based recyclable vinyl polymers point in the right direction
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