ABSTRACT
The Pearl River Delta Urban Agglomeration (PRDUA) is a highly urbanized region in China. The urbanized climate, especially the heat island effect, has a significant impact on urban ecosystems and habitats. Based on MODIS land surface temperature (LST) data and land cover data in 2000, 2005, 2010, 2015, and 2019, we quantified the land surface thermal environment and ecosystem service value (ESV), analyzed the decoupling between LST and ESV in the PRDUA from 2000 to 2019 using the decoupling analysis model, revealed the trade-off between them, and analyzed the spatiotemporal variation of the synergistic state between LST and ESV in PRDUA. The results showed that, from 2000 to 2019, the spatial pattern of land surface thermal environment in the PRDUA was relatively stable in time series but showed spatial variation with high fluctuation in the core area and low fluctuation in the peripheral area. The ESV of the PRDUA showed a trend of stable spatial distribution and decreasing in time series. The ESV of all the nine cities in PRDUA decreased by more than 9%. The decoupling between land surface thermal environment and the overall ESV of the PRDUA, as well as with the values of provisioning, regulating and support services, was dominated by weak negative decoupling and strong negative decoupling, showing a more significant trade-off, which indicated that the ecosystems of the PRDUA were still significantly influenced by the environmental characteristics of urbanization, and that the spatiotemporal variation of the decoupling states was related to the spatial variation of urbanization levels in PRDUA. The formulation of future ecological policies in the PRDUA must consider the differences in urbanization levels and the differences in the trade-offs between urbanized environments and ecosystems to precisely formulate ecological control and restoration plans and improve the efficiency and implementation effects of ecological planning.
Subject(s)
Ecosystem , Rivers , China , Cities , Conservation of Natural Resources , Hot Temperature , UrbanizationABSTRACT
Magnesium borohydride (Mg(BH4)2) has been considered as a potential material for hydrogen storage. In this paper, density functional theory studies have been carried out on native point defects and electrically active impurities (Ni and Ti) in Mg(BH4)2. A detailed analysis of the geometrical structures, energetics and migration of the defects reveals that hydrogen related defects are charged and their formation energies are Fermi-level dependent. We propose a specific mechanism for the decomposition of Mg(BH4)2: the self-diffusion of Mgi2+ is the rate-limiting process for decomposing Mg(BH4)2. Moreover, Ni and Ti impurities can tailor the hydrogen desorption kinetics of Mg(BH4)2 by shifting the Fermi level, but the effects of impurities on shifting the Fermi levels are related to how the impurity is incorporated into Mg(BH4)2.
