Long‐term measurements of the light absorption coefficient (babs) obtained with a particle soot absorption photometer (PSAP), babs (PSAP), have been previously reported for Barrow, Alaska, and ...Ny‐Ålesund, Spitsbergen, in the Arctic. However, the effects on babs of other aerosol chemical species coexisting with black carbon (BC) have not been critically evaluated. Furthermore, different mass absorption cross section (MAC) values have been used to convert babs to BC mass concentration (MBC = babs/MAC). We used a continuous soot monitoring system (COSMOS), which uses a heated inlet to remove volatile aerosol compounds, to measure babs (babs (COSMOS)) at these sites during 2012–2015. Field measurements and laboratory experiments have suggested that babs (COSMOS) is affected by about 9% on average by sea‐salt aerosols. MBC values derived by COSMOS (MBC (COSMOS)) using a MAC value obtained by our previous studies agreed to within 9% with elemental carbon concentrations at Barrow measured over 11 months. babs (PSAP) was higher than babs (COSMOS), by 22% at Barrow (PM1) and by 43% at Ny‐Ålesund (PM10), presumably due to the contribution of volatile aerosol species to babs (PSAP). Using babs (COSMOS) as a reference, we derived MBC (PSAP) from babs (PSAP) measured since 1998. We also established the seasonal variations of MBC at these sites. Seasonally averaged MBC (PSAP) decreased at a rate of about 0.55 ± 0.30 ng m−3 yr−1. We also compared MBC (COSMOS) and scaled MBC (PSAP) values with previously reported data and evaluated the degree of inconsistency in the previous data.
Key Points
We evaluated the accuracy of black carbon (BC) measurements at Barrow, Alaska, and Ny‐Ålesund, Spitsbergen, in the Arctic
At Barrow, seasonally averaged BC mass concentrations decreased in winter and summer at a rate of 0.55 ± 0.30 ng m−3 yr−1 during 1998–2015
We established seasonal variations of BC at the two sites and evaluated the causes of the inconsistency of the previously reported data
A major limitation to cardiac tissue engineering and regenerative medicine strategies is the lack of proliferation of postnatal cardiomyocytes. The extracellular matrix (ECM) is altered during heart ...development, and studies suggest that it plays an important role in regulating myocyte proliferation. Here, the effects of fetal, neonatal and adult cardiac ECM on the expansion of neonatal rat ventricular cells in vitro are studied. At 24h, overall cell attachment was lowest on fetal ECM; however, ~80% of the cells were cardiomyocytes, while many non-myocytes attached to older ECM and poly-l-lysine controls. After 5 days, the cardiomyocyte population remained highest on fetal ECM, with a 4-fold increase in number. Significantly more cardiomyocytes stained positively for the mitotic marker phospho-histone H3 on fetal ECM compared with other substrates at 5 days, suggesting that proliferation may be a major mechanism of cardiomyocyte expansion on young ECM. Further study of the beneficial properties of early developmental aged cardiac ECM could advance the design of novel biomaterials aimed at promoting cardiac regeneration.
Trend analyses were performed on several indicators of Arctic haze using data from sites located in the North American, Norwegian, Finnish and Russian Arctic for the spring months of March and April. ...Concentrations of nonseasalt (nss) SO
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in the Canadian, Norwegian and Finnish Arctic were found to have decreased by 30-70% from the early 1990s to present. The magnitude of the decrease depended on location. The trend in nss SO
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at Barrow, Alaska from 1997 to present, is unclear. Measurements at Barrow of light scattering by aerosols show a decrease of about 50% between the early 1980s and the mid-1990s for both March and April. Restricting the analysis to the more recent period of 1997 to present indicates an increase in scattering of about 50% during March. Aerosol NO
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measured at Alert, Canada has increased by about 50% between the early 1990s and 2003. Nss K
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and light absorption, indicators of forest fires, have a seasonal maximum during the winter and spring and minimum during the summer and fall at both Alert and Barrow. Based on these data, the impact of summertime forest fire emissions on low-altitude surface sites within the Arctic is relatively small compared to winter/spring emissions. Key uncertainties about the impact of long range transport of pollution to the Arctic remain including the certainty of the recent detected trends; sources, transport and trends of soot; and radiative effects due to complex interactions between aerosols, clouds and radiation in the Arctic.
The recent decline in sea ice cover in the Arctic Ocean could affect the regional radiative forcing via changes in sea ice–atmosphere exchange of dimethyl sulfide (DMS) and biogenic aerosols formed ...from its atmospheric oxidation, such as methanesulfonic acid (MSA). This study examines relationships between changes in total sea ice extent north of 70°N and atmospheric MSA measurement at Alert, Nunavut, during 1980–2009; at Barrow, Alaska, during 1997–2008; and at Ny‐Ålesund, Svalbard, for 1991–2004. During the 1980–1989 and 1990–1997 periods, summer (July–August) and June MSA concentrations at Alert decreased. In general, MSA concentrations increased at all locations since 2000 with respect to 1990 values, specifically during June and summer at Alert and in summer at Barrow and Ny‐Ålesund. Our results show variability in MSA at all sites is related to changes in the source strengths of DMS, possibly linked to changes in sea ice extent as well as to changes in atmospheric transport patterns. Since 2000, a late spring increase in atmospheric MSA at the three sites coincides with the northward migration of the marginal ice edge zone where high DMS emissions from ocean to atmosphere have previously been reported. Significant negative correlations are found between sea ice extent and MSA concentrations at the three sites during the spring and June. These results suggest that a decrease in seasonal ice cover influencing other mechanisms of DMS production could lead to higher atmospheric MSA concentrations.
Key Points
Variation in methanesulfonic acid exists at Alert measurement station
Trends in MSA are linked to changes in DMS emissions and transport
Increase in MSA since 2000 at all sites are coincident with change in sea ice
Abstract
The largest uncertainty in the historical radiative forcing of climate is caused by changes in aerosol particles due to anthropogenic activity. Sophisticated aerosol microphysics processes ...have been included in many climate models in an effort to reduce the uncertainty. However, the models are very challenging to evaluate and constrain because they require extensive in situ measurements of the particle size distribution, number concentration, and chemical composition that are not available from global satellite observations. The Global Aerosol Synthesis and Science Project (GASSP) aims to improve the robustness of global aerosol models by combining new methodologies for quantifying model uncertainty, to create an extensive global dataset of aerosol in situ microphysical and chemical measurements, and to develop new ways to assess the uncertainty associated with comparing sparse point measurements with low-resolution models. GASSP has assembled over 45,000 hours of measurements from ships and aircraft as well as data from over 350 ground stations. The measurements have been harmonized into a standardized format that is easily used by modelers and nonspecialist users. Available measurements are extensive, but they are biased to polluted regions of the Northern Hemisphere, leaving large pristine regions and many continental areas poorly sampled. The aerosol radiative forcing uncertainty can be reduced using a rigorous model–data synthesis approach. Nevertheless, our research highlights significant remaining challenges because of the difficulty of constraining many interwoven model uncertainties simultaneously. Although the physical realism of global aerosol models still needs to be improved, the uncertainty in aerosol radiative forcing will be reduced most effectively by systematically and rigorously constraining the models using extensive syntheses of measurements.
The COVID-19 pandemic has placed significant pressure on health and social care. Survivors of COVID-19 may be left with substantial functional deficits requiring ongoing care. We aimed to determine ...whether pre-admission frailty was associated with increased care needs at discharge for patients admitted to hospital with COVID-19.
Patients were included if aged over 18 years old and admitted to hospital with COVID-19 between 27 February and 10 June 2020. The Clinical Frailty Scale (CFS) was used to assess pre-admission frailty status. Admission and discharge care levels were recorded. Data were analysed using a mixed-effects logistic regression adjusted for age, sex, smoking status, comorbidities, and admission CRP as a marker of severity of disease.
Thirteen hospitals included patients: 1671 patients were screened, and 840 were excluded including, 521 patients who died before discharge (31.1%). Of the 831 patients who were discharged, the median age was 71 years (IQR, 58-81 years) and 369 (44.4%) were women. The median length of hospital stay was 12 days (IQR 6-24). Using the CFS, 438 (47.0%) were living with frailty (≥ CFS 5), and 193 (23.2%) required an increase in the level of care provided. Multivariable analysis showed that frailty was associated with an increase in care needs compared to patients without frailty (CFS 1-3). The adjusted odds ratios (aOR) were as follows: CFS 4, 1.99 (0.97-4.11); CFS 5, 3.77 (1.94-7.32); CFS 6, 4.04 (2.09-7.82); CFS 7, 2.16 (1.12-4.20); and CFS 8, 3.19 (1.06-9.56).
Around a quarter of patients admitted with COVID-19 had increased care needs at discharge. Pre-admission frailty was strongly associated with the need for an increased level of care at discharge. Our results have implications for service planning and public health policy as well as a person's functional outcome, suggesting that frailty screening should be utilised for predictive modelling and early individualised discharge planning.
Submicron atmospheric aerosol particles were collected between 1 March 2008 and 1 March 2009 at Barrow, Alaska, to characterize the organic mass (OM) in the Arctic aerosol. Organic functional group ...concentrations and trace metals were measured with FTIR on submicron particles collected on Teflon filters. The OM varied from 0.07 μg m−3 in summer to 0.43 μg m−3 in winter, and 0.35 μg m−3 in spring, showing a transition in OM composition between spring and winter. Most of the OM in spring could be attributed to anthropogenic sources, consisting primarily of alkane and carboxylic acid functional groups and correlated to elemental tracers of industrial pollution, biomass burning, and shipping emissions. PMF analysis associated OM with two factors, a Mixed Combustion factor (MCF) and an Ocean‐derived factor (ODF). Back trajectory analysis revealed that the highest fractions of the MCF were associated with air masses that had originated from northeastern Asia and the shipping lanes south of the Bering Straits. The ODF consisted of organic hydroxyl groups and correlated with organic and inorganic seawater components. The ODF accounted for more than 55% of OM in winter when the sampled air masses originated along the coastal and lake regions of the Northwest Territories of Canada. Frost flowers with organic‐salt coatings that arise by brine rejection during sea ice formation may account for this large source of carbohydrate‐like OM during the ice‐covered winter season. While the anthropogenic sources contributed more than 0.3 μg m−3 of the springtime haze OM, ocean‐derived particles provided comparable OM sources in winter.
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