| 41. |
- Carlén, Anna, et al.
(författare)
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Systolic Blood Pressure Response to Exercise in Endurance Athletes in Relation to Oxygen Uptake, Work Rate and Normative Values
- 2022
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Ingår i: Journal of cardiovascular development and disease. - : MDPI AG. - 2308-3425. ; 9:7
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Tidskriftsartikel (refereegranskat)abstract
- Work rate has a direct impact on the systolic blood pressure (SBP) during aerobic exercise, which may be challenging in the evaluation of the SBP response in athletes reaching high work rates. We aimed to investigate the exercise SBP response in endurance athletes in relation to oxygen uptake (VO2), work rate and to recent reference equations for exercise SBP in the general population. Endurance athletes with a left-ventricular end-diastolic diameter above the reference one performed a maximal bicycle cardiopulmonary exercise test. The increase in SBP during exercise was divided by the increase in VO2 (SBP/VO2 slope) and in Watts, respectively (SBP/W slope). The maximum SBP (SBPmax) and the SBP/W slope were compared to the predicted values. In total, 27 athletes (59% men) were included; mean age, 40 ± 10 years; mean VO2max, 50 ± 5 mL/kg/min. The mean SBP/VO2 slope was 29.8 ± 10.2 mm Hg/L/min, and the mean SBP/W slope was 0.27 ± 0.08 mm Hg/W. Compared to the predicted normative values, athletes had, on average, a 12.2 ± 17.6 mm Hg higher SBPmax and a 0.12 ± 0.08 mm Hg/W less steep SBP/W slope (p < 0.01 and p < 0.001, respectively). In conclusion, the higher SBPmax values and the less steep SBP/W slope highlight the importance of considering work rate when interpreting the SBP response in endurance athletes and suggest a need for specific normative values in athletes to help clinicians distinguish physiologically high maximal blood pressure from a pathological blood pressure response.
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| 42. |
- Chandrika Ranjendra Nair, Hari Ram, 1989-, et al.
(författare)
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Aerosol demasking enhances climate warming over South Asia
- 2023
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic aerosols mask the climate warming caused by greenhouse gases (GHGs). In the absence of observational constraints, large uncertainties plague the estimates of this masking effect. Here we used the abrupt reduction in anthropogenic emissions observed during the COVID-19 societal slow-down to characterize the aerosol masking effect over South Asia. During this period, the aerosol loading decreased substantially and our observations reveal that the magnitude of this aerosol demasking corresponds to nearly three-fourths of the CO2-induced radiative forcing over South Asia. Concurrent measurements over the northern Indian Ocean unveiled a ~7% increase in the earth’s surface-reaching solar radiation (surface brightening). Aerosol-induced atmospheric solar heating decreased by ~0.4 K d−1. Our results reveal that under clear sky conditions, anthropogenic emissions over South Asia lead to nearly 1.4 W m−2 heating at the top of the atmosphere during the period March–May. A complete phase-out of today’s fossil fuel combustion to zero-emission renewables would result in rapid aerosol demasking, while the GHGs linger on.
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| 43. |
- Chen, Bing, et al.
(författare)
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Light absorption enhancement of black carbon from urban haze in Northern China winter
- 2017
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 221, s. 418-426
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric black carbon (BC) is an important pollutant for both air quality and Earth's energy balance. Estimates of BC climate forcing remain highly uncertain, e.g., due to the mixing with non-absorbing components. Non-absorbing aerosols create a coating on BC and may thereby act as a lens which may enhance the light absorption. However, this absorption enhancement is poorly constrained. To this end a two-step solvent dissolution protocol was employed to remove both organic and inorganic coatings, and then investigate their effects on BC light absorption. Samples were collected at a severely polluted urban area, Jinan, in the North China Plain (NCP) during February 2014. The BC mass absorption cross-section (MAC) was measured for the aerosol samples before and after the solvent-decoating treatment, and the enhancement of MAC (E-MAC) from the coating effect was defined as the ratio. A distinct diurnal pattern for the enhancement was observed, with EMAC 1.3 +/- 0.3 (1 S.D.) in the morning, increasing to 2.2 +/- 1.0 in the afternoon, after that dropping to 1.5 +/- 0.8 in the evening-night. The BC absorption enhancement primarily was associated with urban-scale photochemical production of nitrate and sulfate aerosols. In addition to that, regional-scale haze plume with increasing sulfate levels strengthened the absorption enhancement. These observations offer direct evidence for an increased absorption enhancement of BC due to severe air pollution in China.
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| 44. |
- Chen, Bing, et al.
(författare)
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Reconciling modeling with observations of radiative absorption of black carbon aerosols
- 2017
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Ingår i: Journal of Geophysical Research - Atmospheres. - 2169-897X .- 2169-8996. ; 122:11, s. 5932-5942
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Tidskriftsartikel (refereegranskat)abstract
- The physical treatment of internal mixing and aging of black carbon (BC) aerosols that allow for enhanced solar absorption of the BC is an important parameterization in climate models. Many climate models predict a factor of 2-3 lower aerosol absorption optical depth (AAOD) than the atmospheric columnar absorption observed from ground-based networks such as AERONET, likely because these models do not parameterize properly the BC absorption enhancement (E-MAC). Models that are configured with an internal mixing have predicted large variations of E-MAC, which are poorly constrained from ambient measurements. We determined the BC E-MAC from aerosol coatings with a two-step solvent experiment to remove both organic and inorganic coatings in ambient fine particulate matter (PM2.5). Observations in a rural North China site showed that the E-MAC varied from 1.4 to 3. The E-MAC increases simultaneously with SO42-/EC ratios, suggesting the photochemical production of sulfate coatings enhanced BC absorption. A global climate model, parameterized to account for these observational constraints, verifies that sulfates are primary drivers of the BC absorption enhancement in severely polluted area in China. This magnification of the radiative forcing of coated BC is stronger by a factor of similar to 2 than predicted by the standard parameterization (external mixing) in the climate model and is in better agreement with AERONET observations of AAOD. This result would be useful for testing the representation of solar absorption by BC-containing particles in the newer generation of climate models. Plain Language Summary Atmospheric black carbon (BC) or soot in fine particulate matter (PM2.5) is emitted from incomplete combustion of fossil fuel or biomass/biofuel. The BC is an important pollutant for both air quality and Earth's energy balance, and the BC radiative forcing maybe second only to that of CO2. The photochemical production of nonabsorbing secondary aerosols may create a coating on BC and may thereby act as a lens which may enhance the light absorption. However, this absorption enhancement is poorly constrained by ambient measurements, and thus the estimates of BC climate forcing remain highly uncertain. To this end, an aerosol filter dissolution-filtration (AFD) with two-step solvent dissolution protocol was employed to remove both organic and inorganic coatings and then investigate their effects on BC light absorption. The observations and model simulation showed that the BC warming effect likely doubled due to lens effect from secondary aerosols.
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| 45. |
- Chen, Bing, et al.
(författare)
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Source Forensics of Black Carbon Aerosols from China
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:16, s. 9102-9108
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Tidskriftsartikel (refereegranskat)abstract
- The limited understanding of black carbon (BC) aerosol emissions from incomplete combustion causes a poorly constrained anthropogenic climate warming that globally may be second only to CO2 and regionally, such as over East Asia, the dominant driver of climate change. The relative contribution to atmospheric BC from fossil fuel versus biomass combustion is important to constrain as fossil BC is a stronger climate forcer. The source apportionment is the underpinning for targeted mitigation actions. However, technology-based bottom-up emission inventories are inconclusive, largely due to uncertain BC emission factors from small-scale/household combustion and open burning. We use top-down radiocarbon measurements of atmospheric BC from five sites including three city sites and two regional sites to determine that fossil fuel combustion produces 80 +/- 6% of the BC emitted from China. This source-diagnostic radiocarbon signal in the ambient aerosol over East Asia establishes a much larger role for fossil fuel combustion than suggested by all 15 BC emission inventory models, including one with monthly resolution. Our results suggest that current climate modeling should refine both BC emission strength and consider the stronger radiative absorption associated with fossil-fuel-derived BC. To mitigate near-term climate effects and improve air quality in East Asia, activities such as residential coal combustion and city traffic should be targeted.
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| 46. |
- Cho, Chaeyoon, et al.
(författare)
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Observation-based estimates of the mass absorption cross-section of black and brown carbon and their contribution to aerosol light absorption in East Asia
- 2019
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 212, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we estimated the contribution of black carbon (BC) and brown carbon (BrC) to aerosol light absorption from surface in-situ and aerosol robotic network (AERONET) columnar observations. The mass absorption cross-section (MAC) of BC (MAC(BC)) was estimated to be 6.4 +/- 1.5 m(2) g(-1) at 565 mn from in-situ aerosol measurements at Gosan Climate Observatory (GCO), Korea, in January 2014, which was lower than those observed in polluted urban areas. A BrC MAC of 0.62 +/- 0.06 m(2) g(-1) (565 mn) in our estimate is approximately ten times lower than MACK at 565 nm. The contribution of BC and BrC to the carbonaceous aerosol absorption coefficient at 565 nm from the in-situ measurements was estimated at 88.1 +/- 7.4% and 11.9 +/- 7.4%, respectively at GCO. Similarly, the contribution of BC and BrC to the absorption aerosol optical depth (AAOD) for carbonaceous aerosol (CA), constrained by AERONET observations at 14 sites over East Asia by using different spectral dependences of the absorption (i.e., absorption Angstrom exponent) of BC and BrC, was 84.9 +/- 2.8% and 15.1 +/- 2.8% at 565 nm, respectively. The contribution of BC to CA AAOD was greater in urban sites than in the background areas, whereas the contribution of BrC to CA AAOD was higher in background sites. The overall contribution of BC to CA AAOD decreased by 73%-87% at 365 nm, and increased to 93%-97% at 860 nm. The contribution of BrC to CA AAOD decreased significantly with increasing wavelength from approximately 17% at 365 nm to 4% at 860 nm.
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| 47. |
- Cui, Xinjuan, et al.
(författare)
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Radiative absorption enhancement from coatings on black carbon aerosols
- 2016
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 551, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- The radiative absorption enhancement of ambient black carbon (BC), by light-refractive coatings of atmospheric aerosols, constitutes a large uncertainty in estimates of climate forcing. The direct measurements of radiative absorption enhancement require the experimentally-removing the coating materials in ambient BC-containing aerosols, which remains a challenge. Here, the absorption enhancement of the BC core by non-absorbing aerosol coatings was quantified using a two-step removal of both inorganic and organic matter coatings of ambient aerosols. The mass absorption cross-section (MAC) of decoated/pure atmospheric BC aerosols of 4.4 +/- 0.8 m(2)g(-1) was enhanced to 9.6 +/- 1.8 m(2)g(-1) at 678-nm wavelength for ambiently-coated BC aerosols at a rural Northern China site. The enhancement of MAC (E-MAC) rises from 1.4 +/- 0.3 in fresh combustion emissions to similar to 3 for aged ambient China aerosols. The three-week high-intensity campaign observed an average E-MAC of 2.25 +/- 0.55, and sulfates were primary drivers of the enhanced BC absorption.
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| 48. |
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| 49. |
- Dasari, Sanjeev, 1989-
(författare)
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Isotope-based constraints on sources and processing of black carbon, carbon monoxide, and brown carbon in South Asia
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The highly populated South Asian region is facing rapid economic growth and urbanization. Here, both climate- and health-affecting atmospheric agents such as light-absorbing aerosols black carbon (BC) and brown carbon (BrC), trace gas carbon monoxide (CO), are often found in relatively high levels compared to in other regions. However, atmospheric chemistry-transport/climate models are unable to fully capture the extent of the abundance of BC, CO, and BrC in the regional atmosphere during winter. The Thesis aims to address potentially important uncertainties that may be contributing to the model-observation offset — uncertainties in the ambient optical properties of BrC, uncertainties in the relative source contributions of BC (biomass burning vs. fossil fuel combustion) and CO (direct emission-derived vs. atmospheric chemical oxidation-derived), uncertainties in the regional lifetime and absolute emission fluxes of BC. For the Thesis work, field sampling was conducted at three sites, megacity Delhi (key source region), the Bangladesh Climate Observatory–Bhola Island (BCOB; receptor site for the highly-polluted Indo-Gangetic Plain) and the Maldives Climate Observatory–Hanimaadhoo Island (MCOH; receptor site for wider South Asia).The light-absorptivity of water-soluble BrC is found to decrease by ~84% during transport of haze from source-to-receptor regions i.e., Delhi-to-BCOB-to-MCOH — much greater than estimated in chamber studies and accounted in models. Atmospheric photochemical oxidation is found to be a likely driver for the loss of water-soluble BrC light-absorption in the S Asian outflow (with an estimated bleaching rate of 0.20±0.05 day−1) (Paper I). Radiocarbon (Δ14C)-based source apportionment of BC aerosols shows a stark similarity in the relative contributions of fossil (~50%) and biomass sources (~50%) at BCOB as well as at MCOH, suggesting a regional homogeneity in BC source contributions. However, a distinct stable isotopic fingerprint (δ13C) of BC in the N Indian Ocean is found to be arising from a small yet significant contribution (upto 10%) from C4-biomass burning in peninsular India (region south of 23.4°N) (Paper II). Comparison of source-segregated observed and emission inventory-driven modeled BC concentrations indicates regional offsets in the anthropogenic emission fluxes of BC in emission inventories—overestimated fossil-BC in the Indo-Gangetic Plain and underestimated biomass-BC in peninsular India (Paper II). Dual-isotope (δ13C, δ18O)-based source apportionment of CO shows a significantly large contribution (~80%) from direct emissions of primary sources (biomass burning and fossil fuel combustion) in South Asia, in contrast to modeled CO budget (Paper III). The BC-to-CO ratio in South Asia is found to be higher, by a factor of 2-3, than in other polluted regions such as in East Asia during winter. The regional lifetime and emission flux of BC are estimated to be 8±0.5 days (higher than values used in models) and ~2.4±1 Tg/yr (significantly higher than estimated in current emission inventories), respectively (Paper IV).Taken together, for convergence between models and observations in wintertime South Asia, i) the ‘dynamic’ nature of BrC light-absorption should be considered in models, ii) improvements in emission information of BC and CO are needed for better-simulating concentrations. Controls on activities such as open burning (such as agricultural crop residue burning, domestic burning of wood and dung as fuel) in South Asia could enable a reduction in BC, CO, and BrC, thereby leading to improved air quality and paving the way for achieving some of the key sustainable development goals outlined by the United Nations.
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| 50. |
- Dasari, Sanjeev, et al.
(författare)
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Observation-constrained atmospheric lifetime and emission fluxes of black carbon aerosols over South Asia
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Black carbon (BC) aerosols cause climate perturbation and affect air quality/human health. In densely populated South Asia—where the warming effect of BC is estimated to be ~ orders of magnitude higher than the global average—model simulations underestimate the wintertime atmospheric abundance of BC relative to surface observations. Two possible explanations for this model-observation offset are ill-constrained regional emission fluxes and atmospheric BC lifetime (τBC). Here, we combine hourly-resolved BC and carbon monoxide (CO) measurements for three successive winters from a South Asian receptor site—the Maldives Climate Observatory at Hanimaadhoo (MCOH)—in inverse frameworks, to assess the impact of emissions fluxes and lifetimes on ambient BC concentrations. The average ΔBC/ΔCO ratio (background corrected) at MCOH of 14±5 ng m-3 ppb-1 is found to be 2-3 times higher than in the East Asian outflow (range: 2 to 8 ng m-3 ppb-1). A BC transport efficiency of ~86% suggests low influence of wet scavenging processes during the dry South Asian winter period. Using statistical time series analysis, the τBC for dry wintertime South Asia is estimated to be 8±0.5 days, which is higher than commonly used in models. By coupling air mass back trajectories, lifetimes, and the ΔBC/ΔCO time-series data within an inverse modelling framework, we provide an observation-based “top-down” BC emission flux for South Asia estimated to be ~2.4±1 Tg/year. This is significantly higher than estimates from current “bottom-up” emission inventories (EIs). Taken together, this study suggests that to reconcile long-standing BC model-observation offsets in South Asia, existing emission estimates may need to be more than doubled in magnitude.
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