Classification of yearly extreme precipitation events and associated flood risk in the Yangtze-Huaihe River Valley

Fifty cases of regional yearly extreme precipitation events （RYEPEs） were identified over the Yangtze-Huaihe River Valley （YHRV） during 1979-2016 applying the statistical percentile method. There were five types of RYEPEs, namely Yangtze Meiyu （YM-RYEPE）, Huaihe Meiyu （HM-RYEPE）, southwest-northeast-oriented Meiyu （SWNE-RYEPE） and typhoon I and II （TC-RYEPE） types of RYEPEs. Potential vorticity diagnosis showed that propagation trajectories of the RYEPEs along the Western Pacific Subtropical High and its steering flow were concentrated over the southern YHRV. As a result, the strongest and most frequently RYEPEs events, about 16-21 cases with average rainfall above 100 mm, occurred in the southern YHRV, particularly in the Nanjing metropolitan area. There have been 14 cases of flood-inducing RYEPEs since 1979, with the submerged area exceeding 120 km2 as simulated by the FloodArea hydraulic model, comprising six HM-RYEPEs, five YM- RYEPEs, two TC-RYEPEs, and one SWNE-RYEPE. The combination of evolving RYEPEs and rapid expansion of urban agglomeration is most likely to change the flood risk distribution over the Nanjing metropolitan area in the future. In the RCP6.0 （RCPS.5） scenario, the built-up area increases at a rate of about 10.41 km2 （10 yr）-t（24.67 km2 （10 yr）-1） from 2010 to 2100, and the area of high flood risk correspondingly increases from 3.86 km2（3.86 km2） to 9.00 kin2（13.51 km2）. Areas of high flood risk are mainly located at Chishan Lake in Jurong, Lukou International Airport in Nanjing, Dongshan in Jiangning District, Lishui District and other low-lying areas. The accurate simulation of flood scenarios can help reduce losses due to torrential flooding and improve early warnings, evacuation planning and risk analysis. More attention should be paid to the projected high flood risk because of the concentrated population, industrial zones and social wealth throughout the Nanjing metropolitan area.

Synthesis, characterization, and theoretical analysis of three new nonlinear optical materials K7MRE2B15O30（M= Ca and Ba, RE= La and Bi）

Three new complex borate compounds K7CaBi2B15O30, K7CaLa2B15 O30 and K7BaBi2B15O30 have been synthesized by the high-temperature solution method.K7CaLa2B15O30and K7CaBi2B15O30crystallize in the chiral trigonal space group R32, while K7BaBi2B15O30 crystallizes in the noncentrosymmetric orthorhombic polar space group Pca21. All of the title compounds have similar three-dimensional crystal structures, which are composed of isolated B5 O10 groups and LaO6 or BiO6 octahedra, and K^+, Ca^2+, and Ba^2+ cations fill into the cavities to keep charge balance. Based on our research, in the system of K7 MIIRE2 B15O30(MII= Ca, Sr,Ba, Zn, Cd, Pb, K/RE0.5;RE = Sc, Y, La, Gd, Lu, Bi),K7BaBi2B15O30 is unique and crystallizes in a different space group, which enriches the structural chemistry of borate.Detailed structural analyses indicate that the structural variation is due to the difference in size and coordination number of the alkaline-earth metal cations. Besides, UV-Vis-NIR spectroscopy analysis and the second-harmonic generation(SHG) measurement on the powder samples show that K7CaBi2B15O30 exhibits a UV cutoff edge(about 282 nm) and a moderate SHG response(about 0.6 × KDP). In addition,thermal analysis and infrared spectroscopy were also presented. To better understand the structure-property relationships of the title compounds, the first-principles calculations have been performed.

Global Financial Crisis Making a V-Shaped Fluctuation in NO_2 Pollution over the Yangtze River Delta

The Yangtze River Delta（YRD）,China’s main cultural and economic center,has become one of the most seriously polluted areas in the world with respect to nitrogen oxides（NO_x）,owing to its rapid industrialization and urbanization,as well as substantial coal consumption.On the basis of nitrogen dioxide（NO_2）density data from ozone monitoring instrument（OMI）and ground-based observations,the effects of industrial fluctuations due to the financial crisis on local NO_2 pollution were quantitatively assessed.The results were as follows.（1）A distinct V-shaped fluctuation of major industrial products,thermal generating capacity,electricity consumption,and tropospheric NO_2 densities was associated with the global financial crisis from May 2007 to December 2009,with the largest anomalies 1.5 times more than standard deviations at the height of the crisis period from November 2008 to February 2009.（2）Among all industrial sectors,thermal power plants were mainly responsible for fluctuations in local NO_2 pollution during the crisis period.Thermal generating capacity had its greatest decrease of 12.10%at the height of the crisis compared with that during November 2007–February 2008,leading to local tropospheric NO_2 density decreasing by 16.97%.As the crisis appeased,thermal generating capacity increased by 29.63%from November 2009 to February 2010,and tropospheric NO_2 densities correspondingly increased by 30.07%.（3）Among all industrial sectors in the YRD,the thermal power sector has the greatest coal consumption of about 65.96%.A decline in thermal power of about 10% can induce a decrease of about 30%in NOx emissions and NO_2 densities,meaning that a relative small fluctuation in industrial production can lead to a large decrease in tropospheric NO_2 densities over industrially developed areas like the YRD region.Since electricity is mainly obtained from local coal-burning thermal plants without NO_x-processing equipment,installing NO_x-removal devices for all thermal power plants is an important and feasible way of controlling local NO_x pollution at present.