We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physiochemical parameters in the GEOS-Chem chemical transport model. We use Bayesian ...inversion methods combining simulations with GEOS-Chem and ground-based Hg0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations and also matches regional over-water Hg0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is ~ 5.8 Gg yr-1. The ocean accounts for 3.2 Gg yr-1 (55 % of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg0. The optimized Asian anthropogenic emission of Hg0 (gas elemental mercury) is 650-1770 Mg yr-1, higher than its bottom-up estimates (550-800 Mg yr-1). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23 % of present-day atmospheric deposition.
Air‐sea exchange of mercury (Hg) is a critical part of the global Hg cycle as it determines, to a large degree, the response time of the biosphere to changes in mercury inputs. Recent measurements ...have demonstrated that the cycling of Hg between the ocean and atmosphere is complex, principally because of the enhanced oxidation of elemental Hg (Hgo), and the formation of reactive gaseous Hg (RGHg) in the marine boundary layer. We estimate that the dry deposition of RGHg to the ocean, which has not been previously considered in global budgets, is 35% of the total Hg input to the ocean. A further reevaluation of the global Hg cycle suggests that there is a net transfer of Hg from the terrestrial environment to the ocean and that the deep ocean Hg concentration is increasing by a few percent per year. Similarly, anthropogenic inputs on land have increased Hg on the Earth's surface layer with accumulation in the terrestrial environment accounting for nearly 80% of the net input from man's activities. Dry deposition of RGHg is important for the terrestrial realm but because of its relatively short residence time in the atmosphere, it is the oxidation of Hgo over the ocean, rather than RGHg transport offshore, which is primarily contributing to oceanic RGHg deposition.
The aim was to determine the effects of dulaglutide, a synthetic once‐weekly, injectable human glucagon‐like peptide 1 analogue that lowers blood glucose, body weight, appetite and blood pressure, on ...cardiovascular outcomes. People with type 2 diabetes, aged ≥50 years, with glycated haemoglobin (HbA1c) ≤9.5%, and either a previous cardiovascular event, evidence of cardiovascular disease or ≥2 cardiovascular risk factors were randomly allocated to a weekly subcutaneous injection of either dulaglutide (1.5 mg) or placebo and followed within the ongoing Researching cardiovascular Events with a Weekly INcretin in Diabetes (REWIND) trial every 3 to 6 months. The primary cardiovascular outcome is the first occurrence of the composite of cardiovascular death or non‐fatal myocardial infarction or non‐fatal stroke. Secondary outcomes include each component of the primary composite cardiovascular outcome, a composite clinical microvascular outcome comprising retinal or renal disease, hospitalization for unstable angina, heart failure requiring hospitalization or an urgent heart failure visit, and all‐cause mortality. Follow‐up will continue until the accrual of 1200 confirmed primary outcomes. Recruitment of 9901 participants (mean age 66 years, 46% women) occurred in 370 sites located in 24 countries over a period of 2 years. The mean duration of diabetes was 10 years, mean baseline HbA1c was 7.3%, and 31% had prior cardiovascular disease. The REWIND trial's international scope, high proportion of women, high proportion of people without prior cardiovascular disease and inclusion of participants whose mean baseline HbA1c was 7.3% suggests that its cardiovascular and safety findings will be directly relevant to the typical middle‐aged patient seen in general practice throughout the world.
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We demonstrate a high-speed GaN-based green light-emitting diode for plastic optical fiber (POF) communication applications. By using a combination of n-type doping and undoped In x Ga 1-x N/GaN ...based multiple quantum wells (MQWs), and a 76-mum-diameter current-confined aperture structure, we can obtain an extremely high electrical-to-optical (E-O) 3 dB bandwidth (~330 MHz), which is limited by the spontaneous recombination lifetime of the MQWs. A reasonable coupled power (-264 muW) can be simultaneously achieved for a 2 mm in diameter POF with a 0.5 numerical aperture (NA).
To understand further the cycling of mercury at the earth's surface we discuss the results of recent measurements of Hg concentration and speciation in the upper ocean and marine boundary layer of ...the Atlantic Ocean. In water, dissolved gaseous Hg (DGHg) and total Hg measurements are reported; for the atmosphere, total gaseous Hg, reactive gaseous Hg (RGHg) and particulate Hg measurements were made. These measurements allow estimation of gas evasion to the atmosphere and deposition to the ocean. In conjunction with the field collections, incubation experiments both on board ship and in the laboratory have examined further the processes controlling the oxidation and reduction of Hg species in water. Our results suggest that dry deposition of RGHg. could be significant.
Aims
People with diabetes are at high risk for cardiovascular events including heart failure (HF). We examined the effect of the glucagon‐like peptide 1 agonist dulaglutide on incident HF events and ...other cardiovascular outcomes in those with or without prior HF in the randomized placebo‐controlled Researching Cardiovascular Events with a Weekly Incretin in Diabetes (REWIND) trial.
Methods and results
The REWIND major adverse cardiovascular event (MACE) outcome was the first occurrence of a composite endpoint of non‐fatal myocardial infarction, non‐fatal stroke, or death from cardiovascular causes (including unknown causes). In this post‐hoc analysis, a HF event was defined as an adjudication‐confirmed hospitalization or urgent evaluation for HF. Of the 9901 participants studied over a median follow‐up of 5.4 years, 213/4949 (4.3%) randomly assigned to dulaglutide and 226/4952 (4.6%) participants assigned to placebo experienced a HF event (hazard ratio HR 0.93, 95% confidence interval CI 0.77–1.12; p = 0.456). In the 853 (8.6%) participants with HF at baseline, there was no change in either MACE or HF events with dulaglutide as compared to participants without HF (p = 0.44 and 0.19 for interaction, respectively). Combined cardiovascular death and HF events were marginally reduced with dulaglutide compared to placebo (HR 0.88, 95% CI 0.78–1.00; p = 0.050) but unchanged in patients with and without HF at baseline (p = 0.31).
Conclusions
Dulaglutide was not associated with a reduction in HF events in patients with type 2 diabetes regardless of baseline HF status over 5.4 years of follow‐up.
Passive air samplers (PASs) for gaseous mercury
(Hg) were deployed for time periods between 1 month and 1 year at 20 sites
across the globe with continuous atmospheric Hg monitoring using active
...Tekran instruments. The purpose was to evaluate the accuracy of the PAS
vis-à-vis the industry standard active instruments and to determine a
sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time)
that is applicable across a wide range of conditions. The sites spanned a
wide range of latitudes, altitudes, meteorological conditions, and gaseous
Hg concentrations. Precision, based on 378 replicated deployments performed
by numerous personnel at multiple sites, is 3.6 ± 3.0 %1, confirming the PAS's excellent reproducibility
and ease of use. Using a SR previously determined at a single site, gaseous Hg
concentrations derived from the globally distributed PASs deviate from
Tekran-based concentrations by 14.2 ± 10 %. A recalibration
using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference between concentrations from active and passive sampling is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites
of 1.54 ng m−3, this represents an ability to resolve concentrations to
within 0.13 ng m−3. Adjusting the sampling rate to deployment
specific temperatures and wind speeds does not decrease the difference in
active–passive concentration further (8.7 ± 5.7 %), but
reduces its variability by leading to better agreement in Hg concentrations
measured at sites with very high and very low temperatures and very high
wind speeds. This value (8.7 ± 5.7 %) represents a
conservative assessment of the overall uncertainty of the PAS due to
inherent uncertainties of the Tekran instruments. Going forward, the
recalibrated SR adjusted for temperature and wind speed should be used,
especially if conditions are highly variable or deviate considerably from
the average of the deployments in this study (9.89 ∘C,
3.41 m s−1). Overall, the study demonstrates that the sampler is
capable of recording background gaseous Hg concentrations across a wide
range of environmental conditions with accuracy similar to that of industry
standard active sampling instruments. Results at sites with active
speciation units were inconclusive on whether the PASs take up total gaseous
Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg
concentrations were in a similar range as the uncertainty of the PAS.
Reactive gaseous Hg (RGHg), usually assumed to be HgCl2, may dominate the total Hg depositional flux due to its higher surface reactivity and water solubility. Three methods are currently used for ...RGHg sampling: multi-stage filter packs, refluxing mist chambers, and KCl-coated denuders, but none of these methods are considered standard. Field comparisons were performed at Chesapeake Biological Laboratory (CBL) to test if these methods could give comparable results. Mist chambers and denuders were operated continuously for 24 h in some cases to observe the diurnal variation. All methods demonstrated the dynamic fluctuation of atmospheric RGHg, ranging from a few picograms per cubic meter to more than 500 pg/m3. These methods also reported similar temporal RGHg trends. At low RGHg levels, the denuder tended to report higher values of RGHg relative to the filter pack, while mist chamber values were generally in agreement with the filter pack. Discrepancy among methods was more significant under higher RGHg levels. Considering the uncertainties associated with these methods, our data suggest that these methods did produce comparable results. The 24-h continuous measurements showed that RGHg was usually undetectable at night. However, our data also suggest factors in addition to photochemistry, such as movement and mixing of air masses, are influencing the distribution of RGHg at CBL.
Dust models are widely applied over the East Asian region for the simulation of dust emission, transport, and deposition. However, due to the uncertainties in estimates of dust transport, these ...methods still lack the necessary precision to capture the complexity of transboundary dust events. This study demonstrates an improvement in the Community Multiscale Air Quality (CMAQ) model dust treatment during long-range transport of dust from northwestern China to the South China Sea (SCS). To accomplish this, we considered a super dust storm (SDS) event in March 2010 and evaluated the dust scheme by including adjustments to the recent calibration (Dust_Refined_1) and bulk density (Dust_Refined_2) refinements individually and in combination (Dust_Refined_3). The Dust_Refined_3 normalized mean bias of PM10 was −30.65 % for the 2010 SDS event, which was lower in magnitude compared to Dust_Refined_1 (−41.18 %) and Dust_Refined_2 (−49.88 %). Indeed, Dust_Refined_3 improved the simulated aerosol optical depth (AOD) value during significant dust cases, e.g., in March 2005, March 2006, and April 2009. Dust_Refined_3 also showed more clearly that, in March 2010, a “double plume” (i.e., one plume originating from the Taiwan Strait and the other from the western Pacific) separated by the Central Mountain Range (CMR) of Taiwan affected dust transport on the island of Dongsha in the SCS. On 15–21 April 2021, both CMAQ simulations and satellite data highlighted the influence of Typhoon Surigae on dust transport to downwind Taiwan and the western Pacific Ocean (WPO). The CMAQ Dust_Refined_3 simulations further revealed that many dust aerosols were removed over the WPO due to Typhoon Surigae. Hence, the model indicated a near-zero dust particle concentration over the WPO, which was significantly different from previous dust transport episodes over the Taiwan region. Therefore, our study suggested an effective method to improve dust management of CMAQ under unique topographical and meteorological conditions.
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