Spatial variation in aragonite saturation state and the influencing factors in Jiaozhou Bay, China

Both natural processes and human activities affect seawater calcium carbonate saturation state (Ωarag), while the mechanisms are still far from being clearly understood. This study analysed the seawater surface Ωarag during summer and winter in Jiaozhou Bay (JZB), China, based on two cruises observations performed in January and June 2017. The ranges of Ωarag values were 1.55~2.92 in summer and 1.62~2.15 in winter. Regression analyses were conducted to identify the drivers of the change of Ωarag distribution, and then the relative contributions of temperature, mixing processes and biological processes to the spatial differences in Ωarag were evaluated by introducing the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC) as a proxy for Ωarag. The results showed that biological processes were the main factor affecting the spatial differences in Ωarag, with relative contributions of 70% in summer and 50% in winter. The contributions of temperature (25% in summer and 20% in winter) and the mixing processes (5% in summer and 30% in winter) were lower. The increasing urbanization in offshore areas can further worsen acidification, therefore environmental protection in both offshore and onshore is needed

Metallic states in Pb10_{10}(PO4_4)6_6O induced by the Cu/O-insertions and carrier doping

The reports of room-temperature superconductivity in Cu-doped Pb-apatite draw intense interests and debates. Herein, based on the density functional theory, we show that the Cu-insertion in Pb-apatite is thermodynamically stable and further carrier doping can convert the system CuPb$_{10}$(PO$_4$)$_6$O into metal. The electric conduction is mainly along the one-dimensional (1D) Cu-O chains in the c-axis (out-of-plane). The calculated conductance along the c-axis is larger than the in-plane ones by 2 magnitude orders, indicating the 1D conduction behavior. Moreover, the 1D Cu-O chain is an anti-ferromagnetic Mott insulator at zero-doping point due to the super-exchange. Further electron/hole-doping will erase the anti-ferromagnetism. Therefore, the Cu-inserted system CuPb$_{10}$(PO$_4$)$_6$O show transport and magnetic features similar to the cuprate superconductors. On the other hand, the O-insertion can also induce the metallic states, in which the conductance along the out-of-plane direction is higher than the in-plane direction by 6-folds. Our results display the metallization of Pb$_{10}$(PO$_4$)$_6$O via Cu/O-insertions, and suggesting the electric conductions along the c-axis might dominate the transport behaviors.Comment: 17 pages, 9 figure