The Yangtze River Delta region is the region with highest urbanization speed in China. In this study, 6 typical urbanization areas in Yangtze River Delta were selected as the objectives of study. Flood risk assessment index system was established based on the flood disaster formation mechanism, and analytic hierarchy process was utilized to define the weight of indices. The flood hazard, the exposure of disaster bearing body, the vulnerability of disaster bearing body and the comprehensive flood risk corresponding to three typical years in different urbanization stages, 1991, 2001 and 2006 were assessed. The results show that the flood hazard and the exposure of disaster bearing body in the 6 areas are all with an increasing trend in the process of urbanization, among which, the increasing trend of the exposure of disaster bearing body is especially obvious. Though the vulnerabilities of disaster bearing body in the 6 areas are all with decreasing trend owe to the enhancement of flood control and disaster mitigation capability, the comprehensive flood risks in the 6 areas increased as a whole, which would pose a serious threat to urban sustainable development. Finally, effective countermeasures for flood risk management of urbanization areas in Yangtze River Delta were put forward based on the assessment results. 相似文献
Identifying the geographic origins of Chinese mitten crabs is important for food safety and fair market competition. In this study, we used strontium (Sr) isotopes as a tool to trace the geographic origins of Chinese mitten crabs. Chinese mitten crabs, water, and different types of crab feed were collected from four different lakes for Sr isotope analyses. The results showed that the Sr isotope compositions of the different parts from one single crab were consistent within error, indicating that any piece of a crab could be used to represent the Sr isotope characteristics of the whole crab. The Sr isotope compositions of Chinese mitten crabs from the same lake were consistent within the analytical error, and the values were similar to the Sr isotope composition of the water from the same lake. However, the Sr isotope compositions of water and crabs from different lakes are significantly different. Therefore, the Sr isotope compositions of Chinese mitten crabs are mainly controlled by lake water composition, while the impact of feed is limited. This study provides an effective method for tracing the geographic origins of Chinese mitten crabs.
The Tengchong-Lianghe tin district in northwestern Yunnan, China, is an important tin mineralization area in the Sanjiang Tethyan Metallogenic Domain. There are three N–S trending granite belts in the Tengchong-Lianghe area, with emplacement ages ranging from Early Cretaceous to Late Cretaceous and Early Cenozoic. Tin mineralization is spatially associated with these granitic rocks. However, the petrogenetic link between the tin deposits and the host granites is not clear because of the lack of age data for the tin mineralization. We investigate the possibility of direct dating of cassiterite from three typical tin deposits in the Tengchong-Lianghe tin district, using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). In situ LA-MC-ICP-MS dating of seven cassiterite samples from the Lailishan (LLS-1 and LLS-2), Xiaolonghe (XLH, WDS, DSP, and HJS), and Tieyaoshan (TYS) tin deposits yielded well-defined 206Pb/207Pb–238U/207Pb isochron ages. To assess the accuracy of the in situ U/Pb dating of cassiterite, 40Ar/39Ar dating of coexisting muscovite (in samples LLS-1, DSP, and TYS) was also performed. The cassiterite in situ U/Pb ages (47.4?±?2.0, 71.9?±?2.3, and 119.3?±?1.7 Ma, respectively) are in excellent agreement with the coexisting muscovite 40Ar/39Ar ages (48.4?±?0.3, 71.9?±?1.4, and 122.4?±?0.7 Ma, respectively). The U/Pb ages of cassiterite combined with the 40Ar/39Ar ages of muscovite indicate that there are three tin mineralization events in this district: the Lailishan tin deposit at 47.4?±?2.0 to 52?±?2.7 Ma, the Xiaolonghe tin deposit at 71.6?±?2.4 to 3.9?±?2.0 Ma, and the Tieyaoshan tin deposit at 119.3?±?1.7 to 122.5?±?0.7 Ma. These ages are highly consistent with the zircon U/Pb ages of the host granites. It is su.ggested that the Cretaceous tin mineralization might have taken place in a subduction environment, while the Early Tertiary tin metallogenesis was in a postcollisional geodynamic setting. 相似文献