No abstract

With tourism development in China, the influx of tourists in popular tourist attractions has become more frequent. However, space cannot accommodate such a large influx of tourists. Through empirical testing, this research identified 23 variables that influence the safety of tourists in crowded spaces. We divided 23 variables into three factors: pressure factors, state factors, and crowd management actions. Based on the data collected, this study proposes a system model that includes a feedback mechanism to evaluate the safety of highly aggregated tourist crowds (HATCs) and identify moments requiring security warnings. System simulation results showed that the safety level of HATCs presented a complex process of change in different situations. Thus, management can take corrective actions. We tested this model by simulating different crowding conditions and assessing the safety level of tourists. Different warning plans were proposed based on the simulated security level.

Geochemical elements, significant indicator of environmental change，have been widely used in paleoenvironment research. By comparative analysizing of sediment’s geochemical characterstics of core PJ and core ZX-1, almost opposite relations was found between them. In Holocene, there are repeated transgression-regression cycles and the deposition profile of core PJ was in the critical zone of transgression-regression. When climate was warm and humid, sea-level rose, the sedimentary environmental salinity increased and ability of element eluviate-leaching were weak, geochemical elements can not be effectively separated. On the contrary, when climate was dry and cold, sea-level became lower, the role of the element eluviate-leaching was enhanced, and different geochemical elements can be effective separated. This mechanism enables that indicators significance of core PJ’s geochemistry element changing is the opposite direction to other regions.

Water samples were collected in the northern, eastern and southern tidal creeks of Chongming Dongtan in January, 2009. The samples were passed through 0.45μm pore size GF/C glass fiber membrane and colloid was isolated by mini tangential flow ultrafiltration (TFF) with ultrafiltration membrane pore-size of 1kD (1kD=1 000 Daltons). Then the content of organic carbon was tested by TOC II. Results show that the contents of dissolved and colloidal organic carbon (DOC and COC) in the northern creek are higher than the eastern and southern tidal creeks of Chongming Dongtan, and the concentration of DOC decreased from high tidal flat to low tidal flat. Hydrodynamic and vegetation are the important factors to affect the content of COC in tidal creek water of Chongming Dongtan.