Unveiling unique microbial nitrogen cycling and nitrification driver in coastal Antarctica.

Largely removed from anthropogenic delivery of nitrogen (N), Antarctica has notably low levels of nitrogen. Though our understanding of biological sources of ammonia have been elucidated, the microbial drivers of nitrate (NO3-) cycling in coastal Antarctica remains poorly understood. Here, we explore microbial N cycling in coastal Antarctica, unraveling the biological origin of NO3- via oxygen isotopes in soil and lake sediment, and through the reconstruction of 1968 metagenome-assembled genomes from 29 microbial phyla. Our analysis reveals the metabolic potential for microbial N2 fixation, nitrification, and denitrification, but not for anaerobic ammonium oxidation, signifying a unique microbial N-cycling dynamic. We identify the predominance of complete ammonia oxidizing (comammox) Nitrospira, capable of performing the entire nitrification process. Their adaptive strategies to the Antarctic environment likely include synthesis of trehalose for cold stress, high substrate affinity for resource utilization, and alternate metabolic pathways for nutrient-scarce conditions. We confirm the significant role of comammox Nitrospira in the autotrophic, nitrification process via 13C-DNA-based stable isotope probing. This research highlights the crucial contribution of nitrification to the N budget in coastal Antarctica, identifying comammox Nitrospira clade B as a nitrification driver.

Spatial distribution, sources, and direct radiative effect of carbonaceous aerosol along a transect from the Arctic Ocean to Antarctica.

Carbonaceous aerosols (CA) have a high impact on air quality and climate. However, the composition and spatial variability of CA in the marine boundary layer (MBL) remain understudied, especially in the remote regions. Here, atmospheric organic carbon (OC) and elemental carbon (EC) measurements using DRI Model 2001 Thermal/Optical Carbon Analyzer in the MBL were performed during the Chinese Antarctic (2019-2020) and Arctic (2021) research expedition, spanning about 160 latitudes. Due to varying intensities of atmospheric transport from the continents, a significant latitudinal gradient in OC and EC was observed. OC exhibited the highest concentration over the coastal East Asia (CEA), with a mean of 4324 ng m-3 (358-18027 ng m-3), followed by the Arctic Ocean (AO). Similar OC levels were detected over the Southern Ocean (SO) and the Antarctic Ice Sheet (AIS). Similarly, the highest EC was also observed over CEA, with a mean of 867 ng m-3 (71-3410 ng m-3), followed by AO and SO, while the lowest EC appeared over the AIS, with a mean of 30 ng m-3 (2-70 ng m-3). The lower Char-EC/Soot-EC ratios over AO and CEA compared to SO and AIS indicated that fossil fuel combustion contributed more to EC over AO and CEA, while biomass burning played a more significant role in EC levels over SO and AIS. The high OC/EC ratio over AIS was associated with an extremely low EC level and the formation of secondary OC over AIS. SBDART model results suggested that EC had a net warming effect on the atmospheric column, with the highest direct radiative effects (DRE) over AO (5.50 ± 0.15 W m-2, corresponding a heating rate of 0.15 K day-1) and the lowest DRE over SO (1.35 ± 0.04 W m-2, corresponding a heating rate of 0.04 K day-1).

Long-range atmospheric transport of microplastics across the southern hemisphere.

Airborne microplastics (MPs) can undergo long range transport to remote regions. Yet there is a large knowledge gap regarding the occurrence and burden of MPs in the marine boundary layer, which hampers comprehensive modelling of their global atmospheric transport. In particular, the transport efficiency of MPs with different sizes and morphologies remains uncertain. Here we show a hemispheric-scale analysis of airborne MPs along a cruise path from the mid-Northern Hemisphere to Antarctica. We present the inaugural measurements of MPs concentrations over the Southern Ocean and interior Antarctica and find that MPs fibers are transported more efficiently than MPs fragments along the transect, with the transport dynamics of MPs generally similar to those of non-plastic particles. Morphology is found to be the dominant factor influencing the hemispheric transport of MPs to remote Antarctic regions. This study underlines the importance of long-range atmospheric transport in MPs cycling dynamics in the environment.

Effect of predictive nursing combined with amiodarone on the treatment of tachyarrhythmia in patients with coronary heart disease.

OBJECTIVE: We aimed to investigate the clinical effect of predictive nursing combined with amiodarone on the treatment of tachyarrhythmia in patients with coronary heart disease (CHD). METHODS: The clinical data of 101 patients with CHD and tachyarrhythmia in our hospital were collected retrospectively and divided into two groups according to different intervention methods. Patients in group A (n=50) were treated with Propafenone, while patients in group B (n=51) were treated with Amiodarone. Meanwhile, patients in both groups were given predictive nursing. The therapeutic effect, cardiac function indexes, electrocardiogram (ECG) monitoring results, ventricular rate, chest pain recurrence, adverse reactions, the conversion rate of atrial fibrillation and re-infarction rate were compared between two groups before and after treatment. RESULTS: The total effective rate of group B was 94.21%, which was higher than 62.00% of group A (P<0.05). Compared with group A, group B had lower left ventricular end systolic diameter (LVESD) and left ventricular end diastolic diameter (LVEDD) and higher left ventricular ejection fraction (LVEF) after treatment (P<0.05). Group B also showed shorter QRS duration, longer PR interval and lower ventricular rate after treatment (P<0.05). The re-infarction rate and incidence of adverse reactions in group B was 3.92% and 5.88%, respectively, which was lower than 22.00% and 24.00% in group A, respectively (P<0.05). CONCLUSION: Predictive nursing combined with amiodarone has ideal clinical therapeutic effects on the treatment of tachyarrhythmia in patients with CHD. It can effectively improve cardiac function, increase the conversion rate of atrial fibrillation, and it can reduce re-infarction rate, recurrence rate of chest pain as well as incidence of adverse reactions.

[Adsorption of Phosphate from Aqueous Solutions on Sediments Amended with Magnetite-Modified Zeolite].

Understanding the characteristics of phosphate adsorption onto magnetite-modified zeolite (MZ)-amended sediment is helpful for knowing the exchange behavior and process of phosphorus at the interface between the overlying water and MZ-amended sediment. Furthermore, it is helpful for the application of MZ as an amendment to control phosphorus release from sediment. To achieve this goal, the adsorption of phosphate on unamended and MZ-amended sediments was comparatively investigated using a series of batch experiments, and the fractionation of phosphorus in the phosphate-adsorbed MZ was studied using a sequential extraction process. The kinetic data of phosphate adsorption onto unamended and MZ-amended sediments were more suitably fitted to the Elovich model than to the pseudo-first-order and pseudo-second-order models. The equilibrium adsorption data of phosphate adsorption onto the unamended and MZ-amended sediments were well described by the Langmuir, Freundlich, and Dubinin-Radushkevic isotherm model. The phosphate adsorption performance of the unamended and MZ-amended sediments decreased with increasing solution pH from 4 to 11. The presence of cations, such as K+, Mg2+, and Ca2+, enhanced the adsorption of phosphate on the unamended and MZ-amended sediments, and the promoting effect decreased in the order of Ca2+ > Mg2+ > K+, whereas the presence of HCO3- inhibited the adsorption of phosphate. The mechanisms for phosphate adsorption onto the unamended and MZ-amended sediments involved electrostatic attraction and ligand exchange, while the mechanism for the adsorption of phosphate on MZ in the amended sediment involved ligand exchange. The sequential extraction analysis of phosphate-adsorbed MZ showed that 49.4% of phosphorus in MZ existed in the mobile form (NH4Cl-P, BD-P, and NaOH-nrP), which could be easily released from MZ. Therefore, the used MZ should be recovered from sediment using external magnetic fields after its application. The results of this study indicated that MZ is a promising sediment amendment for the control of internal loading in rivers.