RESUMEN
Long-term occupation of coal gangue dumping sites (CGDS) may destroy ecological environment of nearby area. However, how the CGDS affects the distribution pattern of soil seed banks and vegetation in the nearby area is not clear. In this study, we investigated soil seed bank and vegetation at different distances from the second CGDS of Yangchangwan in Ningdong mining area, Lingwu, Ningxia. The results showed that soil seed bank was mainly distributed in 0-10 cm layer and decreased with increasing soil depth. Species richness of soil seed bank and vegetation first increased and then tended to be stable with increasing distance to the CGDS. The influence range of CGDS on soil seed banks was 300-500 m and was 100-300 m on aboveground vegetation. The CGDS did not affect the vertical distribution pattern of soil seed bank, but significantly affected the horizontal distribution pattern of soil seed banks and aboveground vegetation. The key area of vegetation restoration around the CGDS was between 100 m and 300 m.
Asunto(s)
Banco de Semillas , Suelo , Carbón Mineral , Minería , Instalaciones de Eliminación de ResiduosRESUMEN
Lateral furan-expansion of polycyclic aromatics, which enables multiple O-doping and peripheral edge evolution of rylenes, is developed for the first time. Tetrafuranylperylene TPF-4CN and octafuranylquaterrylene OFQ-8CN were prepared as model compounds bearing unique fjord edge topology and helical conformations. Compared to TPF-4CN, the higher congener OFQ-8CN displays a largely red-shifted (≈333â nm) and intensified absorption band (λmax =829â nm) as well as a narrowed electrochemical band gap (≈1.08â eV) due to its pronounced π-delocalization and emerging of open-shell diradicaloid upon the increase of fjord edge length. Moreover, strong circular dichroism signals in a broad range until 900â nm are observed for open-shell chiral OFQ-8CN, owing to the excellent conformational stability of its central bis(tetraoxa[5]helicene) fragments. Our studies provide insights into the relationships between edge topologies and (chir)optoelectronic properties for this novel type of O-doped PAHs.
RESUMEN
A P(NMe2)3-mediated reductive intramolecular cyclopropanation is developed for the first time, which provides facile access to a wide variety of cyclopropane-fused heterocycles including chromanes, tetrahydroquinolines, lactones, and lactams. Catalytic hydrogenative ring-expansion of the cyclopropane-fused heterocycles is also elaborated, leading to various structurally important medium-sized heterocycles.