Reason Analyses Of Physical And Chemical Properties Of Sediments In Hemu And Xixi Wetland, Hangzhou

As one of main components in urban ecosystems, urban wetland plays important roles in ecological and social functions, such as environmental regulation, resource supply, disaster prevention and control, life support and social culture, etc. However, with the rapid development of economy, society and urbanization, accompanied by severe pollution problems (e.g. eutrophication), urban wetland ecosystem is facing serious challenges such as structural damage, functional degradation and biodiversity decrease. To establish wetland park is a kind of effective sustainable utilization mode to protect the urban wetland, which can significantly solve the eutrophication problem and improve the ecosystem stability. For urban wetland unprotected comprehensively, the daily lives of the residents in wetland have a great interference (pollution) to the wetland, while the various wetland utilizations have a great impact on the wetland ecosystem. Sediment is an important component of the wetland ecosystem, and it is a major pool of material and energy. The physical and chemical characteristics of the sediments can reflect the health status of wetland ecosystem to some extend.Before 2003, Xixi Wetland and Hemu Wetland were similar adjacent wetlands. On the one hand, Xixi Wetland has been protected comprehensively by the form of wetland park since 2003 and is considered less interference. On the other hand, Hemu Wetland is still in the "restricted development" protection status, disturbed by residents living and farming pollution. In this study, the major scientific question is the response of physical and chemical characteristics of the sediments to the human activities. And the main contents of this study include investigation and analysis the influence of the pond using modes and human activities intensity (pond position, distance away from residential areas) on the physical and chemical characteristics of sediments in Hemu Wetland, and taking Xixi and Hemu wetlands as the research objects, study on the effects of wetland protection mode and hydrodynamic conditions on the physical and chemical characteristics of sediments aim to provide scientific basis for urban wetland protection. The main results are as follows:1. Generally, for Hemu Wetland and Xixi Wetland, wetland protection mode and hydrodynamic conditions in relatively large scale had more significant effects on sediment physicochemical characteristics than the pond using modes and distance away from residential areas in relatively smaller scale.2. Organic carbon content, total nitrogen content, total phosphorus content, phosphorus content, TOC/N and δ13C values of sediments in Hemu Wetland were significantly higher than Xixi Wetland. The reason might be Xixi Wetland have been protected better than Hemu Wetland. Although Hemu Wetland existed various using modes of ponds, there were more internal living sewage pollution overall and ecosystem destruction was relatively serious.3. In Hemu and Xixi wetlands, total and available phosphorus contents of pond sediments were both extremely significantly lower than the river sediments of them respectively.4. For Hemu Wetland, pond using modes (i.e. planting water chestnut, fish farming and abandoned) had no significant effect on physicochemical characteristics of sediments. However, organic carbon, ammonium nitrogen and nitrate nitrogen content of the pond sediments near the residential areas were significantly higher than those of the pond sediments far away from residential areas. The results inferred that residential lives (e.g. sewage) have stronger interference than farming activities, which means residential lives near the ponds have aggravated the phenomenon of eutrophication in the vicinity of the residential area.5. Total and available phosphorus contents of the sediments did not differ among the ponds with six different using modes (planting water chestnut, fish farming, abandoned near residential areas and planting water chestnut, fish farming, abandoned away from residential areas) in Hemu Wetland, indicating that the main eutrophication elements of residential sewage were carbon and nitrogen, and phosphorus content was relatively low.