During the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) intensive field campaign conducted in the spring of 2001, aerosol properties were measured on board the R/V Ronald H. ...Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180° backscatter were measured. Aerosol within the ACE‐Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Ångström exponents, optical depth, and vertical profiles of aerosol extinction. All results, except aerosol optical depth and the vertical profiles of aerosol extinction, are reported at a relative humidity of 55 ± 5%. An overdetermined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By adjusting the measured size distribution to take into account nonsphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE‐Asia aerosol. Mass scattering efficiencies of non‐sea‐salt sulfate aerosol, sea salt, submicron particulate organic matter, and dust found for the ACE‐Asia aerosol are comparable to values estimated for ACE 1, Aerosols99, and the Indian Ocean Experiment (INDOEX). Unique to the ACE‐Asia aerosol were the large mass fractions of dust, the dominance of dust in controlling the aerosol optical properties, and the interaction of dust with soot aerosol.
The spectral deconvolution algorithm (SDA) and SDA+ (extended SDA) methodologies can be employed to separate the fine and coarse mode extinction coefficients from measured total aerosol extinction ...coefficients, but their common use is currently limited to AERONET (AErosol RObotic NETwork) aerosol optical depth (AOD). Here we provide the verification of the SDA+ methodology on a non-AERONET aerosol product, by applying it to fine and coarse mode nephelometer and particle soot absorption photometer (PSAP) data sets collected in the marine boundary layer. Using data sets collected on research vessels by NOAA-PMEL(National Oceanic and Atmospheric Administration - Pacific Marine Environmental Laboratory), we demonstrate that with accurate input, SDA+ is able to predict the fine and coarse mode scattering and extinction coefficient partition in global data sets representing a range of aerosol regimes. However, in low-extinction regimes commonly found in the clean marine boundary layer, SDA+ output accuracy is sensitive to instrumental calibration errors. This work was extended to the calculation of coarse and fine mode scattering coefficients with similar success. This effort not only verifies the application of the SDA+ method to in situ data, but by inference verifies the method as a whole for a host of applications, including AERONET. Study results open the door to much more extensive use of nephelometers and PSAPs, with the ability to calculate fine and coarse mode scattering and extinction coefficients in field campaigns that do not have the resources to explicitly measure these values.
Measurements during recent field campaigns downwind of the Indian subcontinent, Asia, and the northeastern United States reveal a substantial decrease in the relative humidity dependence of light ...scattering, fσsp(RH), with increasing mass fraction of particulate organic matter (POM) for submicrometer aerosol. Using data from INDOEX (INDian Ocean EXperiment), ACE Asia (Aerosol Characterization Experiment – Asia), and ICARTT (International Consortium for Atmospheric Research on Transport and Transformation), we have identified, within measurement limitations, the impact of POM on the fσsp(RH) of accumulation mode sulfate‐POM mixtures. The result is a parameterization that quantifies the POM mass fraction ‐ fσsp(RH) relationship for use in radiative transfer and air quality models either as input or as validation. The parameterization is valid where the aerosol consists of an internally mixed sulfate‐carbonaceous accumulation mode and other externally mixed components (e.g. sea salt, dust) and is applicable on both global and regional scales.
Increased production of superoxide anion may contribute to impaired bioactivity of endothelium-derived nitric oxide in hypertension. Ascorbic acid is capable of scavenging superoxide anion; however, ...experimental studies have shown that high physiological concentrations (>1 mmol/L) of ascorbic acid are required to prevent superoxide-mediated vascular dysfunction. To seek kinetic evidence that superoxide anion contributes to endothelial vasomotor dysfunction in human hypertension, we examined the effects of 2.4 or 24 mg/min ascorbic acid intra-arterial infusions on forearm blood flow responses to methacholine or sodium nitroprusside in 30 patients with hypertension and 22 age-matched controls. Endothelium-dependent vasodilation to methacholine was significantly impaired in the hypertensive patients, with a response to the highest dose of methacholine (10 μg/min) of 12.3±6.7 compared with 16.1±5.8 mL · min · dL tissue in the controls (P <0.001). The response to sodium nitroprusside was equivalent in the 2 groups. Ascorbic acid at 24 mg/min significantly improved the forearm blood flow response to methacholine in hypertensive patients with a peak response of 16.1±7.1 mL · min · dL tissue (P =0.001). This dose produced a cephalic vein ascorbic acid concentration of 3.2±1.4 mmol/L. In contrast, ascorbic acid at 2.4 mg/min had no effect on the methacholine response. Ascorbic acid at both doses had no effect on the vasodilator response to sodium nitroprusside in hypertensive patients or the methacholine response in the controls. These results agree with the predicted kinetics for superoxide anion-mediated impairment of endothelium-derived nitric oxide action. Thus, superoxide anion may contribute to impaired endothelium-dependent vasodilation in patients with hypertension.
OBJECTIVES: To determine the associations between diet quality, body mass index (BMI), and health-related quality of life (HRQOL) as assessed by the health and activity limitation index (HALex) in ...older adults. DESIGN: Multivariate linear regression models were used to analyze associations between Dietary Screening Tool (DST) scores, BMI and HALex score, after controlling for gender, age, education, living situation, smoking, disease burden and self-vs. proxy reporting. SETTING: Geisinger Rural Aging Study, Pennsylvania. Participants: 5,993 GRAS participants were mailed HRQOL and DST questionnaires with 4,009 (1,722 male, 2,287 female; mean age 81.5 ± 4.4) providing complete data. Results: HALex scores were significantly lower for participants with dietary intakes categorized as unhealthy (<60) (0.70, 95% CI 0.69, 0.72, p<0.05) or borderline (60–75) (0.71, 95% CI 0.70, 0.73, p<0.05) compared to those scoring in the healthy range (>75) (0.75, 95% CI 0.73, 0.77) based on DST scores. HALex scores were significantly lower for underweight (0.67, 95% CI 0.63, 0.72, p<0.05), obese class II (0.68, 95% CI 0.66, 0.71, p<0.05) and class III participants (0.62 95% CI 0.57, 0.67, p<0.05) compared to those with BMI 18.5–24.9. CONCLUSIONS: Poor diet quality, as assessed by the DST, is associated with lower HRQOL in adults ≥ 74 years of age.
Aerosol chemical, physical, and optical measurements were made aboard the NOAA R/V Ronald H. Brown off the coast of New England from July 12 through August 10, 2002, as part of the New England Air ...Quality Study (NEAQS). Measurements (generally 20 to 100 km from the coast) were made downwind of urban centers (New York City, Boston) and rural areas, and in air masses that had not been in contact with land for several days. On average during NEAQS, 75 ± 8% of the sub‐10 μm aerodynamic diameter dry aerosol mass sampled 18 m above the sea surface was in the sub‐1 μm fraction (size cut at 55% RH). The major submicrometer aerosol components were ammonium sulfate and particulate organic matter (POM, defined here as 1.6 times the mass concentration of organic carbon) comprising more than 92 ± 4% of the total mass. Under northwesterly flow with an average submicrometer total mass concentrations of 11 ± 4.5 μg m−3, POM was the dominant component (68 ± 8%) followed by (NH4)xHySO4 (23 ± 8%), inorganic oxidized material (IOM) (6 ± 4%), and EC (3 ± 1%). Under southwesterly flow with an average submicrometer total mass concentrations of 30 ± 11 μg m−3, (NH4)xHySO4 was the dominant component (54 ± 9%) followed by POM (41 ± 9%), IOM (3 ± 2%), and EC (2 ± 1%). Mie calculations using submicrometer nonrefractory (NR) POM and NR (NH4)xHySO4 + H2O size distributions to calculate submicrometer light scattering (σsp) at a wavelength of 550 nm suggest that POM was a dominant chemical component contributing to aerosol light scattering (haze) during NEAQS 2002, and contributed 60 ± 6 % and 57 ± 11 % to σsp at 55% RH during two pollution episodes off the New England Coast. These results are similar to those from the mid‐Atlantic states during TARFOX but contrary to the long‐term monitoring measurements over the continental northeast United States that show the New England haze is primarily a result of sulfate aerosol.
Dimethylsulfide (DMS) emitted from the ocean is a biogenic precursor gas for sulfur dioxide (SO2) and non-sea-salt sulfate aerosols (SO42−). During the VAMOS-Ocean-Cloud-Atmosphere-Land Study ...Regional Experiment (VOCALS-REx) in 2008, multiple instrumented platforms were deployed in the Southeastern Pacific (SEP) off the coast of Chile and Peru to study the linkage between aerosols and stratocumulus clouds. We present here observations from the NOAA Ship Ronald H. Brown and the NSF/NCAR C-130 aircraft along ~20° S from the coast (70° W) to a remote marine atmosphere (85° W). While SO42− and SO2 concentrations were distinctly elevated above background levels in the coastal marine boundary layer (MBL) due to anthropogenic influence (~800 and 80 pptv, respectively), their concentrations rapidly decreased west of 78° W (~100 and 25 pptv). In the remote region, entrainment from the free troposphere (FT) increased MBL SO2 burden at a rate of 0.05 ± 0.02 μmoles m−2 day−1 and diluted MBL SO42 burden at a rate of 0.5 ± 0.3 μmoles m−2 day−1, while the sea-to-air DMS flux (3.8 ± 0.4 μmoles m−2 day−1) remained the predominant source of sulfur mass to the MBL. In-cloud oxidation was found to be the most important mechanism for SO2 removal and in situ SO42− production. Surface SO42− concentration in the remote MBL displayed pronounced diel variability, increasing rapidly in the first few hours after sunset and decaying for the rest of the day. We theorize that the increase in SO42− was due to nighttime recoupling of the MBL that mixed down cloud-processed air, while decoupling and sporadic precipitation scavenging were responsible for the daytime decline in SO42−.
The Atlantic Tradewind Ocean‐Atmosphere Mesoscale Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the east coast of Barbados and the Northwest ...Tropical Atlantic Station (NTAS) mooring. Measurements of aerosol chemical, microphysical, optical, and cloud‐nucleating properties were made during boreal winter onboard the NOAA RV Ronald H. Brown from 7 January to 13 February 2020. Observed aerosol properties indicate there were distinct periods when the aerosol was typical of clean marine conditions (particle number concentrations <400 cm−3, light absorption levels <1 Mm−1, and 222Rn concentrations <500 mBq m−3) and when there were intrusions of dust mixed to varying degrees with biomass burning aerosol. In comparison to the long‐term dust record at the Barbados Atmospheric Chemistry Observatory, the fraction of samples collected during ATOMIC with dust concentrations greater than 20 μg m−3 exceeded all years of the Barbados January to February record with the exception of 1983. The degree of mixing of the dust with biomass burning aerosol was modulated by the location of the North Atlantic subtropical high. A high located to the west of Africa led to a more northerly transport route and more dust‐like (MDL) aerosol arriving at the ship. A location of the high further to the east over northern Africa led to a more southerly transport route and more biomass burning aerosol mixed with the dust. Properties for the marine, MDL, and mixed dust and biomass burning aerosol are presented.
Key Points
The frequency of episodic dust events was higher during ATOMIC than normal for the Caribbean in January and February
Relative amounts of dust and biomass burning aerosol were modulated by the location of the North Atlantic subtropical high
Cloud Condensation Nuclei concentrations were highest when dust was mixed with biomass
Over the past decade, China has entered a “new normal” phase in economic development, with its role in global trade flows changing significantly. This study estimates the driving forces of Chinese ...export‐embodied carbon emissions in the new normal phase, based on environmentally extended multiregional input‐output modeling and structural decomposition analysis. We find that Chinese export‐embodied CO2 emissions peaked in 2008 at a level of 1,657 million tones. The subsequent decline in CO2 emissions was mainly due to the changing structure of Chinese production. The peak in Chinese export‐embodied emissions is encouraging from the perspective of global climate change mitigation, as it implies downward pressure on global CO2 emissions. However, more attention should focus on ensuring that countries that may partly replace China as major production bases increase their exports using low‐carbon inputs.
Plain Language Summary
A large share of global CO2 emissions is produced by making goods and services that are internationally traded, to which China is the largest contributor. We find that Chinese export‐embodied CO2 emissions peaked in 2008 at a level of 1,657 million tones. The peak in Chinese export‐embodied emissions is encouraging from the perspective of global climate change mitigation, as it implies downward pressure on global CO2 emissions. However, more attention should focus on ensuring that countries that may partly replace China as major production bases increase their exports using low‐carbon inputs.
Key Points
Chinese export‐embodied emissions peaked in 2008 at a level of 1,657 million tones
The subsequent decline in export‐embodied emissions was mainly due to the changing structure of Chinese production
More attention should focus on ensuring that countries increasing their exports do so using low‐carbon inputs
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