Cosmogenic radionuclide Beryllium-7 and Beryllium-10 characteristics and influencing factors in different natural climate regions, China.

The cosmogenic radionuclide 7Be (T1/2: 53.29 days) and 10Be (T1/2: 1.39 My), as unique tracers, play an excellent indicative role in atmospheric environmental changes and Earth surface processes. Currently, their different characteristics and influencing factors in various natural climate environments are still vague. Here, we used a state-of-the-art accelerator mass spectrometry to synchronously measure the ultra-trace 7Be and 10Be in aerosols, obtaining the spatial and temporal variability of daily-resolution atmospheric 7Be and 10Be in different natural climate regions (n = 11) of China. The survey results show that the 10Be and 7Be concentrations in the central/southern regions of China (22-38°N, 85-119°E) in 2020/21 are (0.5-18.7)·104 and (0.4-6.1)·104 atoms·m-3, respectively, with 10Be/7Be ratios of 0.7-3.3. Except for the Tibetan Plateau, there are differences in the concentration thresholds of 10Be and 7Be in various regions, especially in 10Be concentration. These 10Be/7Be thresholds are consistent in areas with an altitude range of 4-3420 m a.s.l and reach their highest values throughout the spring of the year. The analysis results indicate that both 7Be and 10Be are influenced by local meteorological conditions such as rainfall and boundary layer disturbances, while also exhibiting different distribution states. This distribution states is due to the re-suspended soil dust 10Be interference caused by soil wind erosion to varying degrees in different regions, with an average contribution to aerosol 10Be of 5.0 ± 2.6 %-24.2 % ± 13.3 %, and is controlled by local annual rainfall (r = 0.8, p < 0.01). Furthermore, unlike the characteristics of 10Be and 7Be concentrations influenced by local meteorological conditions, the daily variation of corrected 10Be/7Be exhibits independence from meteorological processes other than stratosphere troposphere transport, and its significant seasonal oscillations indicate changes in atmospheric circulation in the East Asian monsoon region.

Unraveling the process of aerosols secondary formation and removal based on cosmogenic beryllium-7 and beryllium-10.

The secondary formation and diffusion processes of aerosol are extraordinarily complex and significantly impact the environment and human health. Therefore, exploring the process of aerosol formation and diffusion based on independent new tracer has always been a concern. The 7Be and 10Be, which are generated only by the action of cosmic rays, are chemically stable and adsorbed on aerosol for transmission, so they have the potential characteristics of aerosol tracers. Here, we obtained the daily resolution atmospheric 7Be, 10Be, and 10Be/7Be without dust interference in Xi'an autumn and winter (heavy pollution period in a typical polluted area) by accelerator mass spectrometry. It is found that during the rapid formation of secondary aerosols (SA) under the stable 10Be/7Be ratio, which indicates the stable atmospheric vertical structure, the concentration of 7Be and 10Be is significantly negatively correlated (R2 > 0.9) with the aerosol concentration. Therefore, SA relative content in aerosols can be estimated by the dilution amount of 7Be and 10Be to reveal the secondary-formation process of aerosol (33% average contribution to aerosols during the winter heavy air pollution period). Furthermore, we also revealed the physical removal process of aerosols based on 7Be, 10Be, and 10Be/7Be, including precipitation removal and diffusion of vertical atmospheric movement caused by stratospheric air intrusion. In summary, meteoric cosmogenic 7Be and 10Be will provide a new way to study the secondary chemical formation and physical removal of aerosols.

Heterobimetallic Uranium-Nickel/Palladium/Platinum Complexes of Phosphinoaryl Oxide Ligands: A Theoretical Probe for Metal-Metal Bonding and Electronic Spectroscopy.

Heterobimetallic uranium-transition metal (U-TM) complexes have abundant active centers (two metals and several ancillary ligands with various donor atoms) and possible metal-metal bonding interaction, leading to diversified electronic structures and rather complicated electronic transition types. In this regard, a comprehensive and systematic theoretical study is highly desired although challenging. In the work, density functional theory (DFT) was utilized to examine a series of uranium-group 10 metal complexes supported by bidentate phosphinoaryl oxide ligands (labeled as L). TM (Ni, Pd, and Pt), uranium oxidation state (IV and III) and axial donor (I, Br, Cl, F, Me3SiO, and vacant) were varied. Calculations demonstrate an intrinsic TM → U dative bond. The order of bond strength of U-Ni > U-Pt > U-Pd is suggested by the formal shortness ratios, quantum theory of atoms in molecule (QTAIM) data, interaction energy ( Eint), and bond orders calculated at various levels of theory. It is further evidenced by relativistic effects of heavy metal, natural orbital population and electronic spectroscopy. Regarding U-Ni complexes with different axial donors, metal-metal distances are found to be linearly correlated with QTAIM data/ Eint/bond orders. Experimental UV-vis-NIR spectra were well reproduced by time-dependent DFT calculations. Complicated visible-light absorption bands, whose understanding remains unclear for many experimentally known heterobimetallic complexes, were rationalized in the work, along with NIR bands assigned as 5f → 5f transitions.